Article

Methane and nitrous oxide fluxes of soils in pure and mixed stands of European beech and Norway spruce

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Abstract

Tree species can affect the sink and source strength of soils for atmospheric methane and nitrous oxide. Here we report soil methane (CH4) and nitrous oxide (N2O) fluxes of adjacent pure and mixed stands of beech and spruce at Solling, Germany. Mean CH4 uptake rates ranged between 18 and 48 μg C m−2 hour−1 during 2.5 years and were about twice as great in both mixed and the pure beech stand as in the pure spruce stand. CH4 uptake was negatively correlated with the dry mass of the O horizon, suggesting that this diminishes the transport of atmospheric CH4 into the mineral soil. Mean N2O emission was rather small, ranging between 6 and 16 μg N m−2 hour−1 in all stands. Forest type had a significant effect on N2O emission only in one mixed stand during the growing season. We removed the O horizon in additional plots to study its effect on gas fluxes over 1.5 years, but N2O emissions were not altered by this treatment. Surprisingly, CH4 uptake decreased in both mixed and the pure beech stands following the removal of the O horizon. The decrease in CH4 uptake coincided with an increase in the soil moisture content of the mineral soil. Hence, O horizons may maintain the gas diffusivity within the mineral soil by storing water which cannot penetrate into the mineral soil after rainfall. Our results indicate that conversion of beech forests to beech–spruce and pure spruce forests could decrease soil CH4 uptake, while the long-term effect on N2O emissions is expected to be rather small.

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... Studies comparing plots of different vegetation could show that tree species can affect CH 4 consumptions by soils [25,26,49,53,54]. Menyailo et al. [26] observed that tree species had an effect on methanotrophic activity in an afforestation, but that the composition of high affinity methantrophs was not altered. ...
... Menyailo et al. [26] observed that tree species had an effect on methanotrophic activity in an afforestation, but that the composition of high affinity methantrophs was not altered. Borken & Beese [25] attributed the observed differences in CH 4 uptake between forest sites to the different litter quality and soil moisture. Similar as to our site, Borken & Beese [25] observed no effect of vegetation on N 2 O fluxes. ...
... Borken & Beese [25] attributed the observed differences in CH 4 uptake between forest sites to the different litter quality and soil moisture. Similar as to our site, Borken & Beese [25] observed no effect of vegetation on N 2 O fluxes. Niklaus et al. [55] observed that CH 4 uptake and soil N 2 O emissions decreased with plant species richness in a grassland experiment. ...
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While differences in greenhouse gas (GHG) fluxes between ecosystems can be explained to a certain degree, variability of the same at the plot scale is still challenging. We investigated the spatial variability in soil-atmosphere fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) to find out what drives spatial variability on the plot scale. Measurements were carried out in a Scots pine (Pinus sylvestris L.) forest in a former floodplain on a 250 m2 plot, divided in homogenous strata of vegetation and soil texture. Soil gas fluxes were measured consecutively at 60 points along transects to cover the spatial variability. One permanent chamber was measured repeatedly to monitor temporal changes to soil gas fluxes. The observed patterns at this control chamber were used to standardize the gas fluxes to disentangle temporal variability from the spatial variability of measured GHG fluxes. Concurrent measurements of soil gas diffusivity allowed deriving in situ methanotrophic activity from the CH4 flux measurements. The soil emitted CO2 and consumed CH4 and N2O. Significantly different fluxes of CH4 and CO2 were found for the different soil-vegetation strata, but not for N2O. Soil CH4 consumption increased with soil gas diffusivity within similar strata supporting the hypothesis that CH4 consumption by soils is limited by the supply with atmospheric CH4. Methane consumption in the vegetation strata with dominant silty texture was higher at a given soil gas diffusivity than in the strata with sandy texture. The same pattern was observed for methanotrophic activity, indicating better habitats for methantrophs in silt. Methane consumption increased with soil respiration in all strata. Similarly, methanotrophic activity increased with soil respiration when the individual measurement locations were categorized into silt and sand based on the dominant soil texture, irrespective of the vegetation stratum. Thus, we suggest the rhizosphere and decomposing organic litter might represent or facilitate a preferred habitat for methanotrophic microbes, since rhizosphere and decomposing organic are the source of most of the soil respiration.
... Temperate forest soils are significant sources of the primarily and secondarily greenhouse gases CO 2 , N 2 O and NO Castro et al., 1993;van Dijk and Duyzer, 1999;Phillips et al., 2010), and significant sinks for atmospheric CH 4 Smith et al., 2000;Borken and Beese, 2006). Based on an ISI search, studies on trace gas exchange between temperate forest soils and the atmosphere have increased by a factor of 12 from the decade 1990-2000 to the decade 2001-2010. ...
... Compared to other land uses, temperate forest soils showed the highest CH 4 uptake rates (up to 150 µg CH 4 -C m −2 h −1 ). Nevertheless, rates of atmospheric CH 4 oxidation for European forest soils were varying widely in a range of 1-165 µg CH 4 -C m −2 h −1 (Ambus and Christensen, 1995;Borken and Brumme, 1997;Borken and Beese, 2006). Some rather acidic forest soils in Germany with pH values of the organic layer below 4.0, as found at the Solling site in central Germany , showed rather low oxidation rates of approx. ...
... For example, Borken et al. (2006) showed that soil moisture strongly controlled the uptake of atmospheric methane, since at higher soil moisture values diffusion of methane into the soil was limited. Castro et al. (1994) even used soil moisture alone as a predictor of methane uptake in temperate forest soil at Harvard Forest. ...
Thesis
In dieser Dissertation wurden langfristige Datasätze zum Boden-Atmosphäre Spurengasaustausch von Lachgas (N2O), Stickstoffmonoxid (NO), Kohlendioxid (CO2), und Methan (CH4) am Standort Höglwald dazu genutzt ein besseres Verständnis zu saisonalen und interannuellen Variabilitäten zu entwickeln und die Hypothese zu überprüfen ob empirische Gleichungen die auf einfach zu messende Umweltfaktoren wie Temperatur und Feuchtigkeit basieren dazu verwendet werden können um Spurengasflüsse auf verschiedenen Zeitskalen vorherzusagen. Die mittleren jährlichen Emissionen von N2O, NO sowie CO2 sowie die Aufnahme atmosphärischen CH4 durch den Boden für den Zeitraum 1994–2010 am Standort Höglwald waren im Bereich von 0.2–3.0 kg N2O-N ha–1 yr–1, 6.4–11.4 kg NO-N ha–1 yr–1, 7.0–9.2 t CO2-C ha–1 yr–1, und –(0.9–3.5) kg CH4-C ha–1 yr–1. Die beobachteten hohen Flüsse der N-Spurengase und die vergleichsweise geringe Methanaufnahme sind höchstwahrscheinlich eine Folge der in der Vergangenheit hohen atmosphärischen Stickstoffdeposition (> 20 kg N ha–1 yr–1) am Standort Höglwald. Die Studie zeigt zum ersten Mal, dass die große interannuelle Variabilität der Spurengasflüsse vor allem im Hinblick auf CO2 und N2O durch Gefrier- und Auftauzyklen verursacht wird und dass mehrjährige Messungen erforderlich sind, um zuverlässige Schätzungen der N2O Flüsse für ein bestimmtes Ökosystem zu erhalten. Basierend auf den in Bezug auf die Beobachtungsdauer und Meßintensität weltweit einmaligen Datensatz zum Spurengasaustausch für ein temperates Waldökosystem wurde im Folgenden untersucht, ob leicht messbare Parameter wie Bodentemperatur und Bodenfeuchte verwendet werden können um die zeitliche Dynamik von Spurengasflüssen zu simulieren. Hierzu wurden empirische lineare und nichtlineare Modelle entwickelt. Die Ergebnisse zeigten, dass Veränderungen der Bodentemperatur und Bodenfeuchte gute Prädiktoren zur Abschätzung der Flüsse von NO und CO2 auf wöchentlicher und, noch besser, monatlicher Zeitskalen waren. Aufgrund der Komplexität der zu Grunde liegenden Prozesse und der Interaktion der Auswirkungen der Bodenfeuchte und Temperatur auf CH4 und N2O Flüsse konnten jedoch für N2O (nur schwache Korrelation) oder CH4 keine sinnvollen empirische Modelle identifiziert werden. Sinnvolle empirische Modelle für monatlich aggregierte Messdaten konnten jedoch entwickelt werden, wenn andere Prädiktoren wie atmosphärische Stickstoffdeposition und Bruttoprimärproduktion des Waldes in den Gleichungen berücksichtigt wurden. Daten zur Brutto Primärproduktion erhöhten dabei insbesondere die Aussagekraft der gewonnenen empirischen Regressionen für CO2 und NO deutlich, während für N2O die atmosphärische Stickstoffdeposition ein wichtiger, zusätzlicher Prädiktor war. In einer abschließenden Studie wurde untersucht, ob über verschiedene terrestrische Ökosystem-Typen (Wald der gemässigten Breiten, Tropenwald und semi-aride Steppe) Veränderungen der Bodenfeuchte und Bodentemperatur die gleichen Wirkungen auf Boden CH4 und N2O Flüsse zeigen, d.h. ob universelle Zusammenhänge zwischen Bodentemperatur und -feuchte einerseits sowie Boden-Atmosphäre-Austausch andererseits aufgezeigt werden können. Dafür wurde nicht nur der Höglwald Datensatz verwendet, sondern auch Messdaten, die an zwei anderen Standorten (Steppe Ort in der Inneren Mongolei, China und Tropenwald Ort in Queensland, Australien) erhoben wurden und für die einjährige Datensätze zu Spurengasflüssen in sub-täglicher Auflösung zur Verfügung standen, in die Analyse miteinbezogen. Jährliche kumulative Flüsse von N2O und CH4 variierten deutlich zwischen den verschiedenen Ökosystemen, wobei die N2O-Flüsse für den Tropenwald Standort am höchsten waren (Tropenwald: 0.96 kg N ha–1 yr–1, gemäßigten Wald im Jahr 1997: 0.67 kg N ha–1 yr–1, Steppe: 0.22 kg N ha–1 yr–1), während die Methanaufnahme für den gemäßigten Wald (–3.45 kg C ha–1 yr–1) und die Steppe (–3.39 kg C ha–1 yr–1) in etwa gleich waren, aber für den Tropenwald Standort (–2.38 kg C ha–1 yr–1) niedriger lagen. Um einen standortübergreifenden Vergleich der Auswirkungen von Bodenfeuchte und Bodentemperatur auf CH4 und N2O Flüsse realisieren zu können wurde ein Normalisierungsansatz entwickelt. Die Analyse ergab, dass die höchste Methan-Aufnahmerate in etwa bei durchschnittlichen Umweltbedingungen lag. Dieser Befund bedeutet, dass jede Verschiebung der Umweltbedingungen—wie z. B. durch den Klimawandel—wahrscheinlich zu einer Verringerung der Methanaufnahme des Bodens führt. Für N2O zeigten die Ökosystem übergreifenden Analysen die erwarteten Muster, d.h. höchste Flüsse bei warmen und feuchten Bedingungen und Ereignisse heftiger Emissionen um den Gefrierpunkt (Gefrier-Autau Zyklen). Die Erklärungsleistung von Bodenfeuchte oder Bodentemperatur hinsichtlich der N2O-Flüsse war gering für alle drei Ökosystemen (R2 ≤ 0.36, kombinierten Effekte: R2 ≤0.50), was darauf hinweist, dass diese beiden wichtigen ökologischen Treiber sowohl synergistische als auch antagonistische Effekte auf andere regulierende Faktoren haben, obwohl die zugrunde liegenden mikrobiellen Prozessen Nitrifikation und Denitrifikation empfindlich auf Veränderungen der Bodentemperatur und Feuchtigkeit reagieren. Die Arbeit zeigt, dass einfache Beziehungen zwischen Bodenfeuchtigkeit und Temperatur und N2O Flüsse nicht vorhanden sind und für die Vorhersage der N2O Flüsse komplexere Modelle benötigt werden, die andere Faktoren wie Bodendurchlüftung, Substratverfügbarkeit, die produzierenden und verbrauchenden Prozesse oder die Zusammensetzung der mikrobiellen Gemeinschaft und ihrer zeitlichen Dynamik berücksichtigen können. Dennoch sind der allgemeine Normalisierungsansatz und die erzielten Ergebnisse nützlich für die Entwicklung von Umwelt-Reaktions Modelle für verschiedene Standorte, z. B. im Zusammenhang mit Modell Parametrisierungen.
... In studied soils, most variability in flux drivers was attributed to seasonal and depth scales; hence, forest type explained only a minor part of the total flux variance ( Table 2). Among ecosystem-scale controls, litter thickness tends to decrease soil methane consumption among different forest types [30,65], but it varied only slightly among study plots (Table 1). Soil pH and nitrogen content negatively correlated with methanotroph abundance in upland soil [69]. ...
... In July and September, soil sink showed no significant variability. Prior studies found the same seasonal emission patterns in temperate [62][63][64] and boreal [65,66] forest soils; forest type was reported both as significant [6,65,67] and non-significant [64,66,68] driver of methane consumption. Interaction of soil physical, chemical and biological factors trigger contrasting emission patterns. ...
... In July and September, soil sink showed no significant variability. Prior studies found the same seasonal emission patterns in temperate [62][63][64] and boreal [65,66] forest soils; forest type was reported both as significant [6,65,67] and non-significant [64,66,68] driver of methane consumption. Interaction of soil physical, chemical and biological factors trigger contrasting emission patterns. ...
Article
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Upland forest ecosystems are recognized as net sinks for atmospheric methane (CH4), one of the most impactful greenhouse gases. Biological methane uptake in these ecosystems occurs due to the activity of aerobic methanotrophic bacteria. Russia hosts one-fifth of the global forest area, with the most extensive forest landscapes located in West Siberia. Here, we report seasonal CH4 flux measurements conducted in 2018 in three types of stands in West Siberian middle taiga–Siberian pine, Aspen, and mixed forests. High rates of methane uptake of up to −0.184 mg CH4 m−2 h−1 were measured by a static chamber method, with an estimated total growing season consumption of 4.5 ± 0.5 kg CH4 ha−1. Forest type had little to no effect on methane fluxes within each season. Soil methane oxidation rate ranged from 0 to 8.1 ng CH4 gDW−1 h−1 and was negatively related to water-filled pore space. The microbial soil communities were dominated by the Alpha- and Gammaproteobacteria, Acidobacteriota and Actinobacteriota. The major group of 16S rRNA gene reads from methanotrophs belonged to uncultivated Beijerinckiaceae bacteria. Molecular identification of methanotrophs based on retrieval of the pmoA gene confirmed that Upland Soil Cluster Alpha was the major bacterial group responsible for CH4 oxidation.
... Forest soils are important sink for atmospheric CH 4 , a greenhouse gas contributing roughly 20% to the observed global warming (IPCC, 2007). While tree species strongly influence the sink strength (Borken et al., 2003;Menyailo and Hungate, 2003;Reay et al., 2005;Borken and Beese, 2006), the mechanisms underlying the tree species effects are poorly understood. Tree species having different canopy cover, rooting depth and density, alter soil temperature, moisture and pH (Angers and Caron, 1998;Hooper et al., 2000); tree species also differ in litter quality and quantity. ...
... The aim of the current work was to determine the extent to which the structure of the microbial community of high-affinity methanotrophs was responsible for tree species effects on atmospheric CH 4 consumption. Tree species is known to strongly affect CH 4 consumption by soil (Borken et al., 2003;Menyailo and Hungate, 2003;Reay et al., 2005;Borken and Beese, 2006), but whether this is due to tree species effects on microbial CH 4 oxidation or soil gas diffusivity is not known. The observed tree species effect has often been attributed to a different gas diffusivity of the litter layers formed by deciduous and coniferous stands (Borken et al., 2003;Borken and Beese, 2006). ...
... Tree species is known to strongly affect CH 4 consumption by soil (Borken et al., 2003;Menyailo and Hungate, 2003;Reay et al., 2005;Borken and Beese, 2006), but whether this is due to tree species effects on microbial CH 4 oxidation or soil gas diffusivity is not known. The observed tree species effect has often been attributed to a different gas diffusivity of the litter layers formed by deciduous and coniferous stands (Borken et al., 2003;Borken and Beese, 2006). In our laboratory incubations, gas diffusivity was kept as a constant and we found, that under these conditions, the CH 4 consumption at low concentrations differed between tree species by a factor of three, a much larger difference than observed in the field. ...
Article
Plant species exert strong effects on ecosystem functions and one of the emerging, and difficult to test hypotheses, is that plants alter soil functions through changing the community structure of soil microorganisms. We tested the hypothesis for atmospheric CH 4 oxidation by using soil samples from a Siberian afforestation experiment and exposing them to 13 C–CH 4. We determined the activity of the soil methanotrophs under different tree species at three levels of initial CH 4 concentration (30, 200 and 1000 ppm) thus distinguishing the activities of low-and high-affinity methanotrophs. Half of the samples were incubated with 13 C-enriched CH 4 (99.9%) and half with 12 C–CH 4. This allowed an estimation of the amount of 13 C incorporated into individual PLFAs and determination of PLFAs of meth-anotrophs involved in CH 4 oxidation at the different CH 4 concentrations. Tree species strongly altered the activity of atmospheric CH 4 oxidation without appearing to change the composition of high-affinity methanotrophs as evidenced by PLFA 13 C labeling. The low diversity of atmospheric CH 4 oxidizers, presumably belonging to the UCSa group, may explain the lack of tree species effects on the composition of soil methanotrophs. We submit that the observed tree species effects on atmospheric CH 4 oxidation indicate an effect on biomass or cell-specific activities rather than by a community change and this may be related to the impact of the tree species on soil N cycling.
... Afforestation and reforestation are considered appropriate strategies for climate change mitigation, and forest plantations are increasing during the last decades throughout the world. Mixed conifers and broadleaves plantations have been developed as a silvicultural management option for substituting single conifer plantations in many countries (Borken and Beese 2006;Vesterdal et al. 2008). Indeed, there is a general effort to promote the chain of ecological succession towards mixed stands with native broadleaved species characterized by higher levels of biodiversity and resilience (Pausas et al. 2004). ...
... According to our first hypothesis, soil CH 4 uptake was significantly greater in plots with the litter of mixed tree species than in pure conifer ones, as well as for soil CO 2 effluxes. Additionally, the greater CH 4 uptake under mixed tree species composition was significant especially during summer and autumn seasons, confirming that the effect of forest type on CH 4 uptake produces a seasonal pattern (Borken and Beese 2006). This result does not seem to depend strictly on soil temperature or moisture, as initially hypothesized. ...
... Some studies have documented that CH 4 uptake in the soil of deciduous tree species' stands is higher than for soils of adjacent coniferous ones (Butterbach-Bahl and Papen 2002;Menyailo and Hungate 2003). The upper litter layer in mixed plots could limit the diffusion of atmospheric CH 4 , favoring its consumption in the deeper horizons (Borken and Beese 2006). N 2 O fluxes were characterized by very low emissions, independently from the litter tree species composition. ...
Article
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The shift of tree species composition from conifers to mixed stands as a silvicultural management option for substituting pure plantations can have consequences for the greenhouse gas (GHG) budgets and climate impact. In this context, the main objective of the study was to assess the effect of tree species composition on GHG fluxes, organic matter of forest floor and soil in a degraded conifers plantation in Central Italy. Field-chamber GHG fluxes, litter, and total concentrations of soil C and N, soil temperature, and soil moisture were analyzed, assessing their relationships, under mixed and pure conifer species composition during three monitoring years. Carbon and nitrogen contents were higher under mixed than pure conifer species composition, both in forest floor and mineral soil. Soil carbon dioxide under litter of mixed tree species was significantly higher than that of pure conifers (+17.5%). Methane uptake was higher in the mixed plots than in the pure ones (+12.4%), especially in summer and autumn. Nitrous oxide fluxes were characterized by very low emissions, higher under mixed tree-species than pure conifers during winter. The relevant role of seasonality was confirmed by including in the linear mixed-effects model (LMM) the seasons as an additional random effect that produced a significant interaction between the soil moisture and soil temperature, especially on soil carbon dioxide and methane fluxes. Overall, the GHG budget was driven by organic matter availability, higher under mixed species. Our findings are a first step to help the understanding of the role of tree species composition on GHG emissions in the Mediterranean forest ecosystems.
... Ants maintain a daily average temperature higher than 20 • C in their nest mounds during that period, but even in winter, temperatures in nest mounds are higher than 1-2 • C and thus the frost never occurs there (Rosengren et al., 1987;Frouz and Finer, 2007). CH 4 oxidation and CO 2 production by microorganisms (Pajari, 1995;Rayment and Jarvis, 2000;Borken and Beese, 2006) and ants (Holm-Jensen et al., 1980) usually increase with increasing temperature. Temperature is an important controller of gas fluxes by microorganisms, especially between −5 • C and 10 • C (i.e., in winter and in parts of spring and autumn) (Dong et al., 1998;Borken and Beese, 2006). ...
... CH 4 oxidation and CO 2 production by microorganisms (Pajari, 1995;Rayment and Jarvis, 2000;Borken and Beese, 2006) and ants (Holm-Jensen et al., 1980) usually increase with increasing temperature. Temperature is an important controller of gas fluxes by microorganisms, especially between −5 • C and 10 • C (i.e., in winter and in parts of spring and autumn) (Dong et al., 1998;Borken and Beese, 2006). It follows that ant nest mounds might support gas fluxes throughout the year. ...
... Moreover, CH 4 flux was positive in several ant nest mounds during July and August. CH 4 oxidation is favoured by porosity and aeration (Vor et al., 2003), high temperatures (Borken and Beese, 2006), and low moisture (Adamsen and King, 1993;Borken and Beese, 2006). Because these conditions typify wood ant nests, we expected CH 4 flux rates to be more negative in ant nest mounds than in the forest soil. ...
... Menyailo and Hungate [17] observed higher CH 4 consumption in aspen, birch and spruce forest soils compared to Scots and Arolla pine forest soils in Siberia. However, average CH 4 uptake rates in mixed and pure beech plantations were about twice as large as that in pure spruce plantations [18]. Soil CO 2 efflux was accelerated after conversion from secondary oak forest to pine plantation in southeastern China [19]. ...
... These results indicate that the higher CO 2 emission rates observed in the near natural forest soil can be attributed mainly to the lower C:N ratio and higher decomposition rate. Some studies have also suggested that differences in fine root biomass or the composition and quality of leaf litter due to land use may affect soil respiration [33,34], or that different tree species affect soil respiration through associated differences in leaf litter quantity, chemical properties, and soil environmental conditions [18,21]. However, we found that fine root biomass, litterfall quantity, C:N ratio of leaf litter, and soil environmental conditions were the non-significant variables in our regression model. ...
... We found no seasonal changes in the N 2 O emission rates in the plantations (Figure 2), while soil N 2 O emission rates in the near natural P. massoniana and C. lanceolata plantations were higher than those of control (Table 3). This is in line with previous studies [18,37], and essentially consistent with a study on soil N 2 O flux in mixed forests of C. hystrix and P. massoniana and pure forests of P. massoniana in the same study site [25]. The soil N 2 O emission rate also differs significantly among vegetation types across Japan [38]. ...
Article
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Greenhouse gases are the main cause of global warming, and forest soil plays an important role in greenhouse gas flux. Near natural forest management is one of the most promising options for improving the function of forests as carbon sinks. However, its effects on greenhouse gas emissions are not yet clear. It is therefore necessary to characterise the effects of near natural forest management on greenhouse gas emissions and soil carbon management in plantation ecosystems. We analysed the influence of near natural management on the flux of three major greenhouse gases (carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2 O)) in Pinus massoniana Lamb. and Cunninghamia lanceolata (Lamb.) Hook. plantations. The average emission rates of CO 2 and N 2 O in the near natural plantations were higher than those in the corresponding unimproved pure plantations of P. massoniana and C. lanceolata, and the average absorption rate of CH 4 in the pure plantations was lower than that in the near natural plantations. The differences in the CO 2 emission rates between plantations could be explained by differences in the C:N ratio of the fine roots. The differences in the N 2 O emission rates could be attributed to differences in soil available N content and the C:N ratio of leaf litter, while the differences in CH 4 uptake rate could be explained by differences in the C:N ratio of leaf litter only. Near natural forest management negatively affected the soil greenhouse gas emissions in P. massoniana and C. lanceolata plantations. The potential impact of greenhouse gas flux should be considered when selecting tree species for enrichment planting.
... Ants maintain a daily average temperature higher than 20 • C in their nest mounds during that period, but even in winter, temperatures in nest mounds are higher than 1-2 • C and thus the frost never occurs there (Rosengren et al., 1987;Frouz and Finer, 2007). CH 4 oxidation and CO 2 production by microorganisms (Pajari, 1995;Rayment and Jarvis, 2000;Borken and Beese, 2006) and ants (Holm-Jensen et al., 1980) usually increase with increasing temperature. Temperature is an important controller of gas fluxes by microorganisms, especially between −5 • C and 10 • C (i.e., in winter and in parts of spring and autumn) (Dong et al., 1998;Borken and Beese, 2006). ...
... CH 4 oxidation and CO 2 production by microorganisms (Pajari, 1995;Rayment and Jarvis, 2000;Borken and Beese, 2006) and ants (Holm-Jensen et al., 1980) usually increase with increasing temperature. Temperature is an important controller of gas fluxes by microorganisms, especially between −5 • C and 10 • C (i.e., in winter and in parts of spring and autumn) (Dong et al., 1998;Borken and Beese, 2006). It follows that ant nest mounds might support gas fluxes throughout the year. ...
... Moreover, CH 4 flux was positive in several ant nest mounds during July and August. CH 4 oxidation is favoured by porosity and aeration (Vor et al., 2003), high temperatures (Borken and Beese, 2006), and low moisture (Adamsen and King, 1993;Borken and Beese, 2006). Because these conditions typify wood ant nests, we expected CH 4 flux rates to be more negative in ant nest mounds than in the forest soil. ...
Article
Resistance to desiccation in larvae of eight species of aquatic, semiaquatic and terrestrial chironomids (Pseudodiamesa branickii, Macropelopia sp., Prodiamesa olivacea, Micropsectra sp., Chironomus riparius, Chironomus dorsalis, Metriocnemus martini and Camptocladius stercorarius) was studied. The larvae were desiccated in exicator at constant conditions (15 °C, 80% RH) and changes in moisture and body water content was recorded. The LD-50 for loss of body water was calculated. The lowest resistance to loss of body water was found in larvae from subfamilies Tanypodinae and Diamesinae Macropelopia sp. and P. branickii. They survived loss of 49.7 and 56.6% of original water content (presented values are LD-50). On the other hand the highest resistance to water loss was found in C. dorsalis. M. martini and C. stercorarius. The larvae of these species may survive loss of 67.4, 76.6 and 84.2% of original water content. Nevertheless the survival time under experimental conditions depends more closely on larval size than on lethal level of water loss. The smaller larvae desiccated faster and perished sooner than large ones despite they tolerate higher loss of body water.
... The investigated soils acted as net CH 4 sinks during the entire study period (Figure 1), as typical for upland forest soils [20,26]. The soil CH 4 uptake rates measured in this study are in the mean range of fluxes measured in northern European temperate forests [26,56,57]. ...
... While in our study, the net CH 4 sink strength was only insignificantly higher in BB than BF stands, generally deciduous forests revealed higher CH 4 oxidation rates than coniferous stands [32,58]. The biological CH 4 sink in deciduous forests can be even twice as high compared to coniferous forest [20,[25][26][27]. Borken and Beese [20] investigated pure stands of beech and spruce as well as their mixtures with 30% spruce or beech, respectively. ...
... The biological CH 4 sink in deciduous forests can be even twice as high compared to coniferous forest [20,[25][26][27]. Borken and Beese [20] investigated pure stands of beech and spruce as well as their mixtures with 30% spruce or beech, respectively. They detected the largest differences between the pure spruce and all other stands (pure beech and the two mixtures). ...
Article
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Research highlights: The admixture of fir to pure European beech hardly affected soil-atmosphere CH4 and N2O fluxes but increased soil organic carbon (SOC) stocks at a site in the Black Forest, Southern Germany. Background and objectives: Admixing deep-rooting silver fir has been proposed as a measure to increase the resilience of beech forests towards intensified drying-wetting cycles. Hence, the goal of this study was to quantify the effect of fir admixture to beech forests on the soil-atmosphere-exchange of greenhouse gases (GHGs: CO2, CH4 and N2O) and the SOC stocks by comparing pure beech (BB) and mixed beech-fir (BF) stands in the Black Forest, Germany. Materials and methods: To account for the impact of drying-wetting events, we simulated prolonged summer drought periods by rainout shelters, followed by irrigation. Results: The admixture of fir to pure beech stands reduced soil respiration, especially during autumn and winter. This resulted in increased SOC stocks down to a 0.9 m depth by 9 t C ha−1 at BF. The mixed stand showed an insignificantly decreased sink strength for CH4 (−4.0 under BB and −3.6 kg C ha−1 year−1 under BF). With maximal emissions of 25 µg N m−2 h−1, N2O fluxes were very low and remained unchanged by the fir admixture. The total soil GHG balance of forest conversion from BB to BF was strongly dominated by changes in SOC stocks. Extended summer droughts significantly decreased the soil respiration in both BB and BF stands and increased the net CH4 uptake. Conclusions: Overall, this study highlights the positive effects of fir admixture to beech stands on SOC stocks and the total soil GHG balance. In view of the positive impact of increased SOC stocks on key soil functions such as water and nutrient retention, admixing fir to beech stands appears to be a suitable measure to mitigate climate change stresses on European beech stands.
... For example, litter removal significantly increased CH 4 uptake rates in soils of temperate forests in Germany (Dong et al., 1998) and Austria (Leitner et al., 2016) and in soils of a beech forest and a deciduous forest in Canada, and a pine forest in Finland (Peichl et al., 2010), and Finland (Saari et al., 1998) in pine forest, whereas litter input in a subtropical forest in China had no effect on CH 4 flux . Conversely, litter removal from the forest floor reduced CH 4 uptake in four soils under pure beech and two mixed forests (30 % spruce, 70 % beech and 70 % spruce, 30 % beech) in Germany (Borken and Beese, 2006). Thus, the potentially important impact of litter on CH 4 flux in soils varied among forest types. ...
... Previous studies have examined litter contribution to soil CH 4 flux (Dong et al., 1998;Saari et al., 1998;Borken and Beese, 2006;Tang et al., 2006;Peichl et al., 2010;Leitner et al., 2016) and variations in soil temperature, soil water content (Yan et al., 2008;Werner et al., 2006), soil inorganic N content, and soil microbial activities affect CH 4 flux in forest soils among forests ecosystems. However, only few field experiments have evaluated the influence of litter dynamics on soil CH 4 flux in forest, particularly the possible effects of nitrogen and carbon derived from litter decomposition on CH 4 flux versus the role that soil fertility or environmental factors plays (Corteselli et al., 2017). ...
Article
Litter comprises a major nutrient source when decomposed via soil microbes and functions as subtract that limits gas exchange between soil and atmosphere, thereby restricting methane (CH4) uptake in soils. However, the impact and inherent mechanism of litter and its decomposition on CH4 uptake in soils remains unknown in forest. Therefore, to declare the mechanisms of litter input and decomposition effect on the soil CH4 flux in forest, this study performed a litter-removal experiment in a tropical rainforest, and investigated the effects of litter input and decomposition on the CH4 flux among forest ecosystems through a literature review. Cumulative annual CH4 flux was −3.30 kg CH4-C ha⁻¹ y⁻¹. The litter layer decreased annual accumulated CH4 uptake by 8% which greater in the rainy season than the dry season in the tropical rainforest. Litter decomposition and the input of carbon and nitrogen in litter biomass reduced CH4 uptake significantly and the difference in CH4 flux between treatment with litter and without litter was negatively associated with N derived from litter input. Based on the literature review about litter effect on soil CH4 around world forests, the effect of litter dynamics on CH4 uptake was regulated by litter-derived nitrogen input and the amount soil inorganic nitrogen content. Our results suggest that nitrogen input via litter decomposition, which increased with temperature, caused a decline in CH4 uptake by forest soils, which could weaken the contribution of the forest in mitigating global warming.
... Mixed stands have the potential to increase production, diversity, and carbon and nutrient storage (Moghaddam 2014). In recent decades, mixed plantations have been developed as a prospective silvicultural management approach for substituting single plantations in China as well as in other countries (Borken and Beese 2006;Vesterdal et al. 2008). A shift in forest cover changes the balance between sink and source for carbon, which can modify the dynamics of soil organic carbon (SOC) and CO 2 emissions (Vitale et al. 2012;Houghton 2013). ...
... Forest tree species composition affects soil CO 2 emissions through changing soil physical and chemical properties that influence the activities of microbe and fine root (Kelliher et al. 2006;Kumar et al. 2014). Tree species composition alters soil chemical, physical, and biological processes through their root system, canopy structure, leaf structure, and litter quality (Borken and Beese 2006;Jonard et al. 2007;Ullah et al. 2008). Soil CO 2 emissions were widely reported to be a significant different in the pure and mixed stands (Borken and Beese 2005;Berger et al. 2010;Wang et al. 2013;Gahagan et al. 2015). ...
Article
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Key message Mixed tree plantations are potential silvicultural systems to increase soil carbon storage through altering litter and root inputs and soil physiochemical properties. Abstract Afforestation and reforestation are major strategies for global climate change mitigation. Different tree species composition can induce diverse changes in soil CO2 emission and soil carbon sequestration in tree plantation. This study employed three plantations of monoculture and mixed Pinus yunnanensis and Eucalyptus globulus to estimate the effect of tree species composition on soil CO2 emission and soil organic carbon storage in subtropical China. We found that tree species composition had a significant effect on the soil CO2 emission and soil organic carbon storage. Soil CO2 emission was lower in the mixed plantation than in the P. yunnanensis plantation, whereas it was higher than in the E. globulus plantation. Differences in soil CO2 emission among the three plantations were determined by leaf litterfall mass, fine root biomass, soil available nitrogen, pH, soil bulk density, and soil C:N ratio. Soil organic carbon storage was 34.5 and 23.2 % higher in the mixed plantation than in the P. yunnanensis and E. globulus plantations, respectively. Higher soil organic carbon stock in the mixed plantation was attributed to lower C/N ratio of leaf litter and soil, greater fine root biomass and soil organic carbon content, and lower soil CO2 emission. We conclude that mixed tree plantation can enhance soil carbon sequestration, but can decrease or increase soil CO2 emission through altering litter and root inputs and soil physiochemical properties.
... However, the consequences of variation in biotic factors on GHG fluxes and sourceesink relations are still poorly understood (Hanson et al., 2000;Matamala et al., 2003;Paterson et al., 2007;Vargas and Allen, 2008). Recent studies reported significant tree species effects on GHG fluxes from temperate deciduous forest soils (Borken and Beese, 2006;Degelmann et al., 2009;Vesterdal et al., 2012). The impact of tree species on GHG fluxes has been explained by an alteration of the physical and chemical properties of the soil as a consequence of species-specific characteristics of stemflow, throughfall (Hagen-Thorn et al., 2004), leaf litter input (Erickson et al., 2002;Guckland et al., 2009Guckland et al., , 2010Van Haren et al., 2010), root activity (Zechmeister-Boltenstern et al., 2005), and a change in the microbial community composition in the rhizosphere (Menyailo et al., 2009). ...
... In our study, WFPS was the main influencing factor on methane uptake, independent from tree species identity or mycorrhizal association type. This is surprising as tree species identity is considered to affect CH 4 consumption strongly (Menyailo and Hungate, 2003;Reay et al., 2005;Borken and Beese, 2006), possibly as a result of species-specific rhizodeposit patterns inhibiting microbial CH 4 oxidation in favor of heterotrophic processes to different extents or as a result of species-specific litter inputs (which were mostly absent in our study). Here we show only an inferior effect of tree species identity on the correlation between methane uptake and plant transpiration (SMA slope heterogeneity; Table 4), which indicates greater soil moisture depletion, and, thus, should be interpreted as a contributing factor to the overall impact of WFPS on methanotrophy. ...
Article
Tree species identity and root-associated microbes are assumed to play an important role in the global terrestrial fluxes of the key biogenic greenhouse gases (GHG; CO2, CH4, N2O), but the specific processes driving this influence and the importance against abiotic impacts are poorly understood. To what extent changes in the species composition of temperate forests and increases in the frequency and duration of summer droughts in the course of global climate change will alter GHG emissions remains unclear. We analyzed the effect of tree species identity and mycorrhizal association type vs. soil drought on GHG fluxes by conducting a greenhouse experiment with four important deciduous tree species which form either ectomycorrhizal or arbuscular mycorrhizal associations. We combined soil gas flux measurements with analyses of leaf gas fluxes, potential fine root respiration, fine root growth and turnover, and N turnover in soil microsites. Our experiment tests the hypotheses that (1) GHG emissions differ between tree species and mycorrhizal association type mainly due to differences in root activity and root-induced processes, and (2) soil drought decreases the amount of GHG exchange from different tree species to a different extent. We found a two times higher global warming potential (GWP) from soil gas exchange in European ash than in the other three tree species (1.9 vs. 0.8-1.0 g CO2-eq kg-1 h-1) mainly due to much higher root mass-specific CO2 emission rates (495 vs. 210-236 mg C kg-1 h-1). Apart from the influence of species differences in fine root productivity, we show a stronger increase in CO2 emission rates per portion of white roots in ash which may indicate a higher metabolic activity of unsuberized fine roots in this tree species. Ectomycorrhizal tree species differed from arbuscular mycorrhizal tree species by a two times greater increase in CO2 emissions per fine root production. The N2O emissions per root mass were up to five times higher in beech than in the other species, caused either by higher nitrate production in the rhizosphere or by lower nitrate consumption. Soil porosity drove the amount of methane uptake, while biotic influences were subordinate. Soil drought generally exerted an important control on GHG fluxes: low water-filled pore space decreased the GWP from soil emissions by only 9% in sycamore, but by 40% (European beech) to 68% (European ash) in the other tree species and largely diminished any tree species differences. This suggests that tree species identity may substantially alter the GWP of temperate forests through rhizosphere processes, but this influence on GHG exchange is diminished by soil drought.
... We measured significant differences in intrinsic CH 4 oxidation rates of soils from contrasting land use types (Fig 1, Table 4) and the observed trend was similar to previous field studies (Borken and Beese, 2006;Kizilova et al., 2013), with highest CH 4 uptake rates exhibited by DF soils, followed by SF and AG soils (Fig 3.1, Table 3.4). Factors that have been proposed to be responsible for differences in CH 4 uptake capacity among land use types include soil physicochemical characters i.e. pH, NH 4 + , air diffusivity (Borken et al., 2003;Borken and Beese, 2006), methanotrophic community population size or biomass (Menyailo et al., 2010;Bárcena et al., 2014) and community structure (Nazaries et al., 2013). ...
... We measured significant differences in intrinsic CH 4 oxidation rates of soils from contrasting land use types (Fig 1, Table 4) and the observed trend was similar to previous field studies (Borken and Beese, 2006;Kizilova et al., 2013), with highest CH 4 uptake rates exhibited by DF soils, followed by SF and AG soils (Fig 3.1, Table 3.4). Factors that have been proposed to be responsible for differences in CH 4 uptake capacity among land use types include soil physicochemical characters i.e. pH, NH 4 + , air diffusivity (Borken et al., 2003;Borken and Beese, 2006), methanotrophic community population size or biomass (Menyailo et al., 2010;Bárcena et al., 2014) and community structure (Nazaries et al., 2013). Since our experimental design eliminated differences in diffusivity between the soils as a variable, the factors other than physical characters could be responsible for our results. ...
... CH 4 production) and methanotrophic bacteria (i.e. CH 4 consumption) (Borken and Beese, 2006;Smith et al., 2000) regulated by soil diffusivity (Wang et al., 2015). CH 4 production occurs under anoxic conditions, although there is evidence of less significant CH 4 production in oxic environments as well (Dean et al., 2018). ...
... This may be partly because boreal forest soils are often a sink for CH 4 , with uptake suggested to increase after fire (Kulmala et al., 2014;Morishita et al., 2014;Tas et al., 2014). In addition, studies have found that CH 4 uptake is only weakly linked to temperature (Borken and Beese, 2006;Castaldi and Fierro, 2005;Dörr et al., 1993), with soil moisture playing a greater role (Grant, 1999). Park et al., 2005 reported Q 10 values of CH 4 oxidation varying from 2.57 to 2.69. ...
Article
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Wildfires strongly regulate carbon (C) cycling and storage in boreal forests and account for almost 10% of global fire C emissions. However, the anticipated effects of climate change on fire regimes may destabilize current C-climate feedbacks and switch the systems to new stability domains. Since most of these forests are located in upland soils where permafrost is widespread, the expected climate warming and drying combined with more active fires may alter the greenhouse gas (GHG) budgets of boreal forests and trigger unprecedented changes in the global C balance. Therefore, a better understanding of the effects of fires on the various spatial and temporal patterns of GHG fluxes of different physical environments (permafrost and nonpermafrost soils) is fundamental to an understanding of the role played by fire in future climate feedbacks. While large amounts of C are released during fires, postfire GHG fluxes play an important role in boreal C budgets over the short and long term. The timescale over which the vegetation cover regenerates seems to drive the recovery of C emissions after both low- and high-severity fires, regardless of fire-induced changes in soil decomposition. In soils underlain by permafrost, fires increase the active layer depth for several years, which may alter the soil dynamics regulating soil GHG exchange. In a scenario of global warming, prolonged exposition of previously immobilized C could result in higher carbon dioxide emission during the early fire succession. However, without knowledge of the contribution of each respiration component combined with assessment of the warming and drying effects on both labile and recalcitrant soil organic matter throughout the soil profile, we cannot advance on the most relevant feedbacks involving fire and permafrost. Fires seem to have either negligible effects on methane (CH4) fluxes or a slight increase in CH4 uptake. However, permafrost thawing driven by climate or fire could turn upland boreal soils into temporary CH4 sources, depending on how fast the transition from moist to drier soils occurs. Most studies indicate a slight decrease or no significant change in postfire nitrous oxide (N2O) fluxes. However, simulations have shown that the temperature sensitivity of denitrification exceeds that of soil respiration; thus, the effects of warming on soil N2O emissions may be greater than on C emissions.
... Temperate forest soils are significant sources of atmospheric greenhouse gases 5 (GHG), namely CO 2 , N 2 O and NO (Brumme and Beese, 1992;Castro et al., 1993;Butterbach-Bahl et al., 1998;van Dijk and Duyzer, 1999;Pilegaard et al., 2006;Phillips et al., 2010), and significant sinks for atmospheric CH 4 (Borken and Brumme, 1997;Henkel, 2000;Smith et al., 2000;Brumme and Borken, 1999;Butterbach-Bahl and Papen, 2002;Borken and Beese, 2006). Based on an ISI search, studies on trace 10 gas exchange between temperate forest soils and the atmosphere have increased by a factor of 12 from the decade 1990-2000 to the decade 2001-2010. ...
... Compared to other land uses, temperate forest soils showed the highest CH 4 uptake rates (up to 150 µg CH 4 -C m −2 h −1 ). Nevertheless, Introduction rates of atmospheric CH 4 oxidation for European forest soils were varying widely in a range of 1-165 µg CH 4 -C m −2 h −1 (Ambus and Christensen, 1995;Borken and Brumme, 1997;Butterbach-Bahl et al., 1998;Brumme and Borken, 1999;Borken and Beese, 2006). Some rather acidic forest soils in Germany with pH values of the organic layer below 4.0, as found at the Solling site in Central Germany (Borken and Brumme,5 1997; Brumme and Borken, 1999), showed rather low oxidation rates of approx. ...
Article
Full-text available
Besides agricultural soils, temperate forest soils have been identified as significant sources of or sinks for important atmospheric trace gases (N2O, NO, CH4, and CO2). Although the number of studies for this ecosystem type increased more than tenfold during the last decade, studies covering an entire year and spanning more than 1–2 yr remained scarce. This study reports the results of continuous measurements of soil-atmosphere C- and N-gas exchange with high temporal resolution carried out since 1994 at the Höglwald Forest spruce site, an experimental field station in Southern Germany. Annual soil N2O emission, NO emission, CH4 uptake, and CO2 emission (1994–2010) varied in a range of 0.2–3.2 kg N2O-N ha−1 yr−1, 6.4–11.4 kg NO-N ha−1 yr−1, 0.9–3.5 kg CH4-C ha−1 yr−1, and 7.0–9.2 t CO2-C ha−1 yr−1, respectively. The observed high fluxes of N-trace gases are most likely a consequence of high rates of atmospheric nitrogen deposition (> 20 kg N ha−1 yr−1) of NH3 and NOx to our site. For N2O cumulative annual emissions were > 0.8 kg N2O-N ha−1 yr−1 high in years with freeze-thaw events (5 out 14 yr). This shows that long-term, multi-year measurements are needed to obtain reliable estimates of N2O fluxes for a given ecosystem. Cumulative values of soil respiratory CO2 fluxes were highest in years with prolonged freezing periods e.g. the years 1996 and 2006, i.e. years with below average annual mean soil temperatures and high N2O emissions. The results indicate that long freezing periods may even drive increased CO2 fluxes not only during soil thawing but also throughout the following growing season. Furthermore, based on our unique database on GHGs we analyzed if soil temperature, soil moisture, or precipitation measurements can be used to approximate GHGs at weekly, monthly, or annual scale. Our analysis shows that simple-to-measure environmental drivers such as soil temperature or soil moisture are suitable to approximate fluxes of NO and CO2 in weekly and monthly scales with a reasonable uncertainty (accounting for up to 80 % of the variance). However, for N2O and CH4 we so far failed to find meaningful correlations and, thus, to provide simple regression models to estimate fluxes. This is most likely due to the complexity of involved processes and counteracting effects of soil moisture and temperature, specifically with regard to N2O production and consumption by denitrification and microbial community dynamics.
... Temperate forest soils are significant sources of the primarily and secondarily greenhouse gases CO 2 , N 2 O and NO (Brumme and Beese, 1992;Castro et al., 1993;van Dijk and Duyzer, 1999;Pilegaard et al., 2006;Phillips et al., 2010), and significant sinks for atmospheric CH 4 (Borken and Brumme, 1997;Henckel et al., 2000;Smith et al., 2000;Brumme and Borken, 1999;Borken and Beese, 2006). Based on an ISI search, studies on trace gas exchange between temperate forest soils and the atmosphere have increased by a factor of 12 from the decade 1990-2000 to the decade 2001-2010. ...
... Compared to other land uses, temperate forest soils showed the highest CH 4 uptake rates (up to 150 µg CH 4 -C m −2 h −1 ). Nevertheless, rates of atmospheric CH 4 oxidation for European forest soils were varying widely in a range of 1-165 µg CH 4 -C m −2 h −1 (Ambus and Christensen, 1995;Borken and Brumme, 1997;Brumme and Borken, 1999;Borken and Beese, 2006). Some rather acidic forest soils in Germany with pH values of the organic layer below 4.0, as found at the Solling site in central Germany (Borken and Brumme, 1997;Brumme and Borken, 1999), showed rather low oxidation rates of approx. ...
Article
Full-text available
Besides agricultural soils, temperate forest soils have been identified as significant sources of or sinks for important atmospheric trace gases (N 2O, NO, CH4, and CO2). Although the number of studies for this ecosystem type increased more than tenfold during the last decade, studies covering an entire year and spanning more than 1-2 years remained scarce. This study reports the results of continuous measurements of soil-atmosphere C- and N-gas exchange with high temporal resolution carried out since 1994 at the Höglwald Forest spruce site, an experimental field station in Southern Germany. Annual soil N2O, NO and CO2 emissions and CH4uptake (1994-2010) varied in a range of 0.2-3.0 kg N2O-N ha-1 yr-1, 6.4-11.4 kg NO-N ha -1 yr-1, 7.0-9.2 t CO2-C ha-1 yr-1, and 0.9-3.5 kg CH4-C ha-1 yr -1, respectively. The observed high fluxes of N-trace gases are most likely a consequence of high rates of atmospheric nitrogen deposition (>20 kg N ha-1 yr-1) of NH3 and NOx to our site. For N2O, cumulative annual emissions were ≥ 0.8 kg N 2O-N ha-1 yr-1 in years with freeze-thaw events (5 out 14 of years). This shows that long-term, multi-year measurements are needed to obtain reliable estimates of N2O fluxes for a given ecosystem. Cumulative values of soil respiratory CO2 fluxes tended to be highest in years with prolonged freezing periods, i.e. years with below average annual mean soil temperatures and high N2O emissions (e.g. the years 1996 and 2006). Furthermore, based on our unique database on trace gas fluxes we analyzed if soil temperature, soil moisture measurements can be used to approximate trace gas fluxes at daily, weekly, monthly, or annual scale. Our analysis shows that simple-to-measure environmental drivers such as soil temperature or soil moisture are suitable to approximate fluxes of NO and CO2 at weekly and monthly resolution reasonably well (accounting for up to 59 % of the variance). However, for CH4we so far failed to find meaningful correlations, and also for N2O the predictive power is rather low. This is most likely due to the complexity of involved processes and counteracting effects of soil moisture and temperature, specifically with regard to N2O production and consumption by denitrification and microbial community dynamics. At monthly scale, including information on gross primary production (CO2, NO), and N deposition (N2O), increased significantly the explanatory power of the obtained empirical regressions (CO2: r2 = 0.8; NO: r2 = 0.67; N2O, all data: r2 = 0.5; N2O, with exclusion of freeze-thaw periods: r2 = 0.65).
... Compacted soil represents a less aerobic environment, which is conducive to CH 4 production (Huttunen et al., 2003;Morishita et al., 2005). Moreover, a thick litter layer could increase the production of methanogenic bacteria in the soil and inhibit CH 4 uptake (Borken and Beese, 2006). ...
... Our results confirm that thinning in temperate and subtropical forests leads to a significant reduction in CH 4 uptake (Keller et al., 2005;Ming et al., 2018). Temperate and subtropical forests have more broadleaved trees (Dannenmann et al., 2008;Yashiro et al., 2008), and we found that thinning-induced the reduction of soil CH 4 uptake was higher in broadleaved forests than in coniferous forests (Borken and Beese, 2006;Ming et al., 2018). Different tree species may affect soil CH 4 uptake as a result of differences in litter composition, soil properties, and methanotrophic bacterial communities (Barrena et al., 2013). ...
Article
Forest thinning is a major forest management practice worldwide and may lead to profound alterations in the fluxes of soil greenhouse gases (GHGs). However, the global patterns and underlying mechanisms of soil GHG fluxes in response to forest thinning remain poorly understood. Here, we conducted a global meta-analysis of 106 studies to assess the effects of forest thinning on soil GHG fluxes and the underpinning mechanisms. The results showed that forest thinning significantly increased soil CO2 emission (mean lnRR: 0.07, 95% CI: 0.03–0.11), N2O emission (mean lnRR: 0.39, 95% CI: 0.16–0.61) and decreased CH4 uptake (mean Hedges’ d: 0.98, 95% CI: 0.32–1.64). Furthermore, the negative response of soil CH4 uptake was amplified by thinning intensity, and the positive response of soil N2O emission decreased with recovery time after thinning. The response of soil CO2 emission was mainly correlated with changes in fine root biomass and soil nitrogen content, and the response of soil CH4 uptake was related to the changes in soil moisture and litterfall. Moreover, the response of soil N2O emission was associated with changes in soil temperature and soil nitrate nitrogen content. Thinning also increased the total balance of the three greenhouse gas fluxes in combination, which decreased with recovery time. Our findings highlight that thinning significantly increases soil GHG emissions, which is crucial to understanding and predicting ecosystem-climate feedbacks in managed forests.
... The absorption of CH 4 is mainly accomplished by methanotrophs in soil. Soil temperature, soil aeration and the activity of soil methanotrophs are the limiting factors of soil methane uptake (Borken and Beese, 2006;Borken et al., 2003). In addition, the competition of soil available N and CH 4 to methane-monooxygenase also inhibits the oxidation of soil methane (Wang et al., 2002). ...
... Forest types differ in the composition of litter, the hydrothermal conditions of soil, and thus affect the emission of N 2 O and CH 4 in soil (Tang et al., 2006). Existing studies mostly compare the greenhouse gas emissions of different forest components, but the effect of tree species structure change on soil greenhouse gas emission in the initial replanting stage is unclear (Borken and Beese, 2006;Piva et al., 2014). ...
Article
Thinning and replanting are effective forest management measures to improve the stand structure and species composition of artificial forests. However, the effects of thinning and replanting on soil N2O and CH4 fluxes and their associations with changes in soil environment factors have been poorly understood in plantation forests. A 36-month field experiment was conducted to elucidate the effects of thinning and replanting different species on soil N2O and CH4 fluxes and related environmental factors in Cunninghamia lanceolata plantation on shallow soil. The experiment consisted of five treatments, uncut control (CK), moderate thinning + replanting evergreen seedlings (MTE), moderate thinning + replanting deciduous seedlings (MTD), heavy thinning + replanting evergreen seedlings (HTE), heavy thinning + replanting deciduous seedlings (HTD). Compared with the control, moderate and heavy thinning increased cumulative N2O emissions by 12.4% and 21.4%, respectively, and reduced CH4 cumulative uptake by 35.4% and 38.8%, respectively. However, the effects on soil N2O and CH4 fluxes replanting deciduous or evergreen seedlings were insignificant. The results showed that thinning increased N2O emissions and decreased CH4 uptake due to the increased soil temperature, labile C and N concentrations. Soil temperature was the dominant factor, and mineral N was a contributing factor affecting N2O and CH4 fluxes. The study concludes that thinning increased the global warming potential with N2O contributing more than CH4 (113.5%: −13.5%). Our findings highlight that thinning increased N2O emissions and decreased CH4 uptake with the increasing intensity and the replanting had no different effects between deciduous and evergreen seedlings on the fluxes of N2O and CH4 during the early years following thinning.
... Intrinsic rates of CH 4 oxidation differed for the three soils in our study (Fig. 1, Table 2). The differences were similar to those reported in previous field studies ( Borken and Beese, 2006;Kizilova et al., 2013), with highest CH 4 uptake rates exhibited by deciduous forest soil, followed by spruce forest and agricultural soils (Fig 1, Table 2). Among the factors proposed to be responsible for differences in intrinsic CH 4 uptake rates are those associated with soil physicochemical characters, i.e. diffusion rates, pH, NH 4 þ (Borken et al., 2003;Borken and Beese, 2006), and those associated with the abundance and composition of MOB (methane oxidizing bacteria) (Bender and Conrad, 1994;Menyailo et al., 2010;Nazaries et al., 2013;B arcena et al., 2014). ...
... The differences were similar to those reported in previous field studies ( Borken and Beese, 2006;Kizilova et al., 2013), with highest CH 4 uptake rates exhibited by deciduous forest soil, followed by spruce forest and agricultural soils (Fig 1, Table 2). Among the factors proposed to be responsible for differences in intrinsic CH 4 uptake rates are those associated with soil physicochemical characters, i.e. diffusion rates, pH, NH 4 þ (Borken et al., 2003;Borken and Beese, 2006), and those associated with the abundance and composition of MOB (methane oxidizing bacteria) (Bender and Conrad, 1994;Menyailo et al., 2010;Nazaries et al., 2013;B arcena et al., 2014). The design of our flow-through chambers was intended to minimize effects associated with differences in diffusion rates between soils. ...
Article
Variations in the rates of atmospheric CH4 uptake in upland soils can arise from both abiotic and biotic factors. Among the less-studied biotic factors is the degree to which methanotroph activity and community composition interact with supply of CH4 to the soil. Here, we investigated whether the abundance of high affinity methanotrophs in a range of soils representing different land use types is substrate (CH4) dependent. Field replicates of three soils sampled from deciduous forest, spruce forest and agricultural sites were incubated in columns flushed continuously for 24 days with air at one of four CH4 concentrations: <1 ppm (starvation), 1.8 (ambient), 30 (low elevated) and 60 (high elevated) ppm. In all soils, CH4 oxidation rates increased linearly with CH4 supply. For all levels of CH4 supply, CH4 oxidation rates were the highest in deciduous forest soil followed by spruce forest and agricultural soils. Terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that the agricultural soil had a distinct methanotrophic community compared to the two forest soils. In particular, the T-RFs (Terminal restriction fragments) associated with USCα and Type II methanotrophs (Methylocystis sp, Methylosinus sp.) were the most abundant in forest soils while Type 1a associated T-RFs dominated in agricultural soil. The agricultural and forest soils also differed in their fractionation of stable isotopes, 13C and 2H, during CH4 oxidation. Altering CH4 concentration in the inlet air did not change methanotroph abundance, as evidenced by three different assays, two qPCR and T-RFLP, that recorded no changes in the number of pmoA genes and/or the relative abundance of T-RFs. Altogether, it is proposed that intrinsic differences in CH4 oxidation rates between soils, particularly between temperate agricultural and forest soils, are driven by methanotroph community structure. The population size of methanotrophs in upland soils did not respond to CH4 availability and is most probably regulated by other factors, such as the availability of nitrogen, cross-feeding or other carbon sources.
... 메탄산화균은 대기 중 메탄의 농도와 토양 내 수분함량, 온도, pH, 유기물함량 등의 영향을 받으며 (Hanson and Hanson, 1996), 크게 두 부류로 나뉜다 (Conrad R. 2007 (Conrad, 2007), pMMO 의 Alpha subunit인 pmoA gene을 16s RNA 와 같이 Maker로 활 용하여 Aerobic methanoprophs를 정량할 수 있다 (Holmes et al., 1995). MacDonald et al., 1997;Smith et al., 2000;Bradford et al., 2001;Borken et al., 2006)과 미국 (Crill, 1991;Yavitt et al., 1993;Goldman et al., 1995) (Priha and Smolander, 1997;Grayston and Prescott, 2005;Lejon et al., 2005;Menyailo, 2007 (Rolston 1986). (Fig. 6). ...
Article
BACKGROUND: Forest soils contain microbes capable of consuming atmospheric methane (CH_4), an amount matching the annual increase in CH_4 concentration in the atmosphere. However, the effect of plant residue production by different forest structure on CH_4 oxidation is not studied in Korea. The objective of this study was to evaluate the effect of Korean alpine soils having different forestation structure on CH_4 uptake rates. METHODS AND RESULTS: the CH_4 flux was measured at three sites dominated with pine, chestnut and oak trees in southern Korea. The CH_4 uptake potentials were evaluated by a closed chamber method for a year. The CH_4 uptake rate was the highest in the pine tree soil (1.05mg/m^2/day) and then followed by oak (0.930mg/m^2/day) and chestnut trees (0.497mg/m^2/day). The CH_4 uptake rates were highly correlated to soil organic matter and moisture contents, and total microbial and methanotrophs activities. Different with the general concent, there was no any correlation between CH_4 oxidation rates, and soil temperature and labile carbon concentrations, irrespective with tree species. CONCLUSION: Conclusively, the methane oxidation rate was correlated in positive manner with organic matter, abundance of methanotrophs. Methane oxidation was different among tree species. This results could be used to estimate methane oxidation rate in forest of Korea after complementing information about statistical data and methane oxidation of other site.
... From several studies, the following trend was observed (in decreasing order of sink strength): woodland > non-cultivated upland > grassland > cultivated soils (Dobbie & Smith, 1996;Hütsch et al., 1994;Le Mer & Roger, 2001;Willison et al., 1995). More specifically, an effect of land-use change on CH 4 oxidation rates was associated to tree species (Borken & Beese, 2006;Menyailo et al., 2010;Menyailo & Hungate, 2003;Reay et al., 2001;Reay et al., 2005;Saggar et al., 2007). Different tree species had varied effects on CH 4 consumption but a common trend was that soils under hardwood species (aspen, beech, birch, oak) consumed more CH 4 than soils under coniferous species (larch, pine, spruce). ...
Thesis
Methane (CH4) is one of the most potent greenhouse gases and its increasing concentration in the Earth’s atmosphere is linked to today’s global warming. The types of land and land-use have an impact on net CH4 fluxes, e.g. wetlands are generally net CH4 emitters while upland forest soils are a sink for CH4. This project aimed to elucidate the effect of afforestation and reforestation on net CH4 fluxes and to determine the control of the CH4-oxidising bacteria (methanotrophs) on net CH4 flux rate. This was investigated using a combination of molecular (T-RFLP, cloning/sequencing, microarray) and activity-specific (PLFA-SIP) approaches. Several sites were selected to analyse soil methanotrophs under shrubs regenerating after a fire compared to a native mature forest (in New Zealand), and under bog, grass, heath, pine and birch vegetation (in Scotland). Furthermore, a simple bottom-up approach was applied to seasonal measurements of local net CH4 fluxes in Scotland. These were upscaled to annual values in order to estimate the contribution to the national CH4 budget for each habitat investigated. The effect on CH4 mitigation of the conversion of different types of non-forested habitat to forests was then estimated. Afforestation/reforestation was always found to induce net CH4 oxidation at rates much faster than previously estimated. This preliminary analysis suggests that heathland conversion to birch forest was beneficial in term of CH4 sinks but it also induced large and permanent losses of soil C. However, bog afforestation with pine trees can potentially neutralise the national CH4 emissions from non-forested areas, while preserving soil C stocks. This project also revealed that changes in net CH4 flux due to land-use changes were closely related to shifts in the structure of the methanotrophic community. The relative abundance of members of the USCα cluster (high-affinity methanotrophs) was a strong predictor of net CH4 fluxes. Finally, the sole presence of trees suggested a niche-specific adaptation of the methanotrophs, which may have been correlated to some of the soil characteristics.
... At low temperature (20°C) acetoclastic methanosaetaceae archea were responsible for CH 4 production and at high temperature (45°C) hydrogenotrophic methanogens play a significant role in CH 4 production . The oxidation of methane is also highly influenced by temperature (Borken and Beese 2006;Le Mer and Roger, 2001). The optimum conditions for aerobic oxidation of methane ranged from 25 to 35°C in paddy rice soil (Mohanty et al., 2007;Min et al. 2002). ...
... The model prediction is similar to that of Saggar et al. (2007), who measured CH 4 on a pasture grazed by sheep. Well-aerated soils are generally a sink for atmospheric CH 4 via methanotrophic oxidation (Le Mer and Roger 2001;Borken and Beese 2006). Methane emissions have, however, been shown to increase following manure application on grassland (Sherlock et al. 2002;Dittert et al. 2005). ...
Article
Backgrounding, raising weaned beef cattle in preparation for finishing in a feedlot, is a common practice in western Canadian beef production systems. The objectives of this study were: (i) to assess the whole-farm greenhouse gas (GHG) emissions from a pasture-based backgrounding system using an observation-based and model-based approach and (it) to compare model-based estimated emissions with observation-based emissions from the key components of the farm, in order to identify the knowledge gaps that merit further study. For the observation-based approach, emissions were garnered from a multi-disciplinary field study that examined three fertility treatments applied to the pasture grazed by beef cattle: (i) no liquid hog manure application (control); (ii) split application of liquid hog manure, half applied in fall and half in spring (split) and (iii) single spring application of liquid hog manure (single). The model-based approach used a systems-based model, adapted from Intergovernmental Panel on Climate Change algorithms, to estimate annual net farm GHG emissions from the three fertility treatments and a hypothetical synthetic fertilizer treatment. Total farm emissions included methane (CH4), nitrous oxide (N2O) emissions from farm components and carbon dioxide (CO2) emissions from energy use. Net farm GHG emissions using the observation-based approach ranged from 0.4 to 2.2 Mg CO2 eq ha(-1) and from 4.2 to 6.5 kg CO2 eq kg(-1) liveweight gain exported; the model-based approach resulted in net farm emissions ranged from 0.6 to 3.7 Mg CO2 eq ha(-1) and from 7.0 to 12.9 kg CO2 eq kg(-1) liveweight gain exported. Except in the control treatment, both enteric CH4 and soil N2O emissions were the major contributors to total farm emissions. Emissions intensity for the hypothetical synthetic fertilizer treatment (9.4 kg CO2 eq kg(-1) liveweight gain) was lower than for the split and single scenarios. Although individual GHG emission estimates varied appreciably, trends in emissions intensity were similar between the two approaches. Efforts to reduce GHG emissions should be directed towards components such as enteric CH4 and soil N2O, which have larger impacts on overall system emissions.
... The positive relationships between root biomass and soil organic matter, and between soil organic matter and denitrification potential, imply that establishing deep-rooted vegetation may increase the depth of the active denitrification zone (Gift et al. 2010). Some forest studies demonstrate species-specific effects on N2O production from denitrification (Menyailo and Huwe 1999, Butterbach-Bahl et al. 2002, van Haren et al. 2010, while others show no effect of vegetation type (Borken andBeese 2006, Christiansen andGundersen 2011). Similarly, in the riparian zone, in some instances no difference has been found between vegetation types in terms of denitrification and N2O production (Clément et al. 2002, Liu et al. 2011, Jacinthe et al. 2012. ...
Thesis
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Less than 0.5 % native vegetation cover remains in the productive Canterbury Plains region of New Zealand. Incorporating native plants into agricultural landscapes could provide numerous benefits including shelter, supplementary stock fodder, production of essential oils or honey, wildlife-corridors, and protection of waterways. New Zealand’s native species are adapted to environments where nitrogen (N) occurs at low concentrations. Such environments are in stark contrast to New Zealand’s agricultural landscapes, where high inputs of fertilisers and animal effluents have elevated soil N. There is a lack of knowledge on how native species will interact with N in agricultural environments. Potentially, native species may alter nitrate leaching to receiving waters and emissions of nitrous oxide (N₂O), a potent greenhouse gas. This research aims to investigate the interaction with soil N of selected native species and their rhizospheres to gain an understanding of species-specific differences and potential effects on N fluxes. The native species investigated were typical of those used in restoration projects. Perennial ryegrass (Lolium perenne), an introduced species that dominates New Zealand pasturelands, was used as a control. I studied rhizosphere soil and foliar N status at two planted restoration sites. Plant growth and uptake in response to agriculturally elevated N levels were investigated in greenhouse pot trials. A field experiment explored the effect of Kunzea robusta (kānuka) on N₂O fluxes from soil. Finally, farm-scale N uptake and reduction in N losses were modelled for various native planting scenarios. At the restoration sites New Zealand native species Austroderia richardii (toetoe), Phormium tenax (flax), Cordyline australis (cabbage tree), Coprosma robusta (karamu), K. robusta, Olearia paniculata (akeake) and Pittosporum tenuifolium (black matipo) had similar foliar N concentrations to L. perenne. While native species with winter leaf loss, Plagianthus regius (ribbonwood) and Sophora microphylla (kōwhai), had higher foliar N than these other species. There was significant inter species variation in rhizosphere soil mineral N concentrations among native species, with A. richardii and P. regius having higher nitrate status than L. perenne. Pot trials revealed that while native species tolerate high N loading (up to 1600 kg ha⁻¹), there was negligible growth response. Increased soil N concentrations resulted in increased foliar N in native plants, of which the high-biomass-producing monocotyledons assimilated the most. Nevertheless, foliar N concentrations were higher for L. perenne receiving N and farm-scale calculations showed L. perenne to extract more soil N than the native species. K. robusta reduced N₂O emissions following effluent application by 80 % relative to control soil, which emitted significant amounts. Modelling revealed that incorporating native species into agricultural landscapes reduced the N loading per hectare due to the reduced area of fertilised and grazed soil. The native monocotyledons, in particular P. tenax and Carex virgata (pukio), have greater potential to reduce nitrate leaching than the woody species and are the most suitable for receiving effluent, whereas K. robusta in farm paddocks may mitigate N₂O emissions following urine deposition by sheltering stock. Further work could involve lysimetry to quantify simultaneously the effects of native species on nitrate leaching and N₂O emissions. These findings provide a first step towards targeted native planting strategies in sustainable agricultural management.
... Wood ant nests acted as hot spots of CO 2 production, especially during summer. Although we expected that CH 4 consumption would be greater in ant nest mounds than in the surrounding forest floor because of the higher aeration (Le Mer & Roger, 2001;Dutaur & Verchot, 2007) and more stable and higher temperature (Borken & Beese, 2006) in nest mounds, we found that CH 4 flux was less negative in ant nest mounds than in the surrounding soil (i.e., CH 4 oxidation was lower in the mounds than in the surrounding soil). In the current study, we therefore attempted to increase our understanding of factors controlling the flux of CH 4 and CO 2 in wood ant nests. ...
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We compared methane (CH4) and carbon dioxide (CO2) fluxes in samples collected from the aboveground parts of wood ant nests and in the organic and mineral layer of the surrounding forest floor. Gas fluxes were measured during a laboratory incubation, and microbial properties (abundance of fungi, bacteria, and methanotrophic bacteria) and nutrient contents (total and available carbon and nitrogen) were also determined. Both CO2 and CH4 were produced from ant nest samples, indicating that the aboveground parts of wood ant nests act as sources of both gases; in comparison, the forest floor produced about four-times less CO2 and consumed rather than produced CH4. Fluxes of CH4 and CO2 were positively correlated with contents of available carbon and nitrogen. The methanotrophic community was represented by type II methanotrophic bacteria, but their abundance did not explain CH4 flux. Fungal abundance was greater in ant nest samples than in forest floor samples but bacterial abundance was similar in both kinds of samples, suggesting that the organic materials in the nests may have been too recalcitrant for bacteria to decompose. The results indicate that the aboveground parts of wood ant nests are hot spots of CO2 and CH4 production in the forest floor.
... The larger variations in mean soil N 2 O emissions among plantations in the hot-humid season than those in the cool-dry season could be related to the variations in soil temperature and moisture. It has been reported that nitrification activities can increase N 2 O production by increasing soil temperature and moisture in temperate forests (Borken and Beese 2006) and in subtropical forests (Tang et al. 2006;Liu et al. 2008). ...
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The effects of land use and land use change on soil green house gas (GHG) fluxes are concerned due to Kyoto protocol requirement. Carbon dioxide, CH 4 and N 2 O fluxes, emission and global warming potential from soil under a tropical dry deciduous forest and Eucalyptus plantation at Mogari, central Gujarat, Western India were measured for three months (February-April, 2011) at fifteen days intervals using closed static chamber technique and gas chromatography method. However, little information is known about the effects of natural forest and plantation on soil-atmosphere greenhouse gas (GHG) exchanges. The mean soil N 2 O and CO 2 emissions in the Eucalyptus plantation (EP) recorded were 0.18 mg N m −2 h −1 and 5.81 mg C m −2 h −1 whereas in dry deciduous forest the values were 0.15 mg N m −2 h −1 and 6.52 mg C m −2 h −1 respectively. The Eucalyptus plantation soil had lower mean CH 4 uptake (-0.024 mg C m −2 h −1) than the dry deciduous forest soils (-0.020 mg C m −2 h −1). Variations in soil N 2 O emissions among the sites could be primarily explained by differences in mean WFPS and soil total N stock. Differences in soil CH 4 uptake among the sites could be mostly attributed to differences in mean WFPS. The C : N ratio of soil could largely account for variations in soil CO 2 emissions among the sites. This study reveals the potential values of GHGs in forest ecosystems.
... Wide variations in CH 4 oxidation, arising from direct human disturbance of soils, have been reported for a variety of land uses, encompassing different soil types and climates (Priem e et al., 1997;Smith et al., 2000;Borken and Beese, 2006;Kim and Kirschbaum, 2014). Some recent examples are also included in Table 1 where land-use changes have been primarily responsible for the observed shifts in soil CH 4 oxidation. ...
... The creation of monospecific stands of trees that are not native to a landscape carries a high risk of consequential ecological damage, such as decrease in ecosystem stability and outbreak of diseases and insect pests [16,17,18,19,20]. As a result, alternative plantations of indigenous broadleaf species are spreading in this region of China and in neighbouring countries [21,22,23,24,25,26,27]. ...
Article
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More than 60% of the total area of tree plantations in China is in subtropical, and over 70% of subtropical plantations consist of pure stands of coniferous species. Because of the poor ecosystem services provided by pure coniferous plantations and the ecological instability of these stands, a movement is under way to promote indigenous broadleaf plantation cultivation as a promising alternative. However, little is known about the carbon (C) stocks in indigenous broadleaf plantations and their dependence on stand age. Thus, we studied above- and below-ground biomass and C stocks in a chronosequence of Mytilaria laosensis plantations in subtropical China; stands were 7, 10, 18, 23, 29 and 33 years old. Our assessments included tree, shrub, herb and litter layers. We used plot-level inventories and destructive tree sampling to determine vegetation C stocks. We also measured soil C stocks by analyses of soil profiles to 100 cm depth. C stocks in the tree layer dominated the above-ground ecosystem C pool across the chronosequence. C stocks increased with age from 7 to 29 years and plateaued thereafter due to a reduction in tree growth rates. Minor C stocks were found in the shrub and herb layers of all six plantations and their temporal fluctuations were relatively small. C stocks in the litter and soil layers increased with stand age. Total above-ground ecosystem C also increased with stand age. Most increases in C stocks in below-ground and total ecosystems were attributable to increases in soil C content and tree biomass. Therefore, considerations of C sequestration potential in indigenous broadleaf plantations must take stand age into account.
... The soil CH 4 flux was significantly correlated with WFPS in the case of Mixed Plantation as shown in Fig.4. This is in contrast to finding of [68], that the soil moisture strongly control the uptake of atmospheric CH 4 by limiting the diffusion of CH 4 into the soil, resulting in a negative correlation between soil moisture and CH 4 uptake rates under most non-drought conditions. There was high and significant correlation which is found between soil CH 4 flux and soil temperature (R 2 = -0.674, ...
Article
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The study of the magnitude of temporal and spatial patterns of Greenhouse Gases (GHG) fluxes from the cultivated land of subtropical regions of India is still an uncharted territory. The paper contributes towards the improvement of actual estimate and investigates the seasonal variation of greenhouse gases (GHGs) emissions (N O, CH and CO ) For the purpose three mono specific plantation viz. Manilkara zapota, Mangifera indica, Dendrocalumus stictus, and Mixed plantation are studied in semi arid region of central Gujarat, India to assess the extent of GHG fluxes in response to their soils and the comparative analysis presented to understand the atmospheric interchanges. The research contributes in building a framework for plantation approach for carbon sequestration by analyzing the patterns of GHGs emission under different ecosystem.
... Maximum methanotrophic activity shifted from the litter layer (Oct 1) down into the topsoil (Oct 6) over time (Fig. 4d), probably because the litter layer (including mineral compounds) became too dry. Other studies (Adamsen and King, 1993;Karbin et al., 2016;Niklaus et al., 2016;Rosenkranz et al., 2006;) also showed that CH 4 consumption is highest in the top centimeters of the mineral soil and that a decreasing soil water content is often associated with a higher CH 4 consumption (Borken and Beese, 2006;Butterbach-Bahl et al., 2002;Hartmann et al., 2011). Stiehl-Braun et al. (2011 observed that the most active zone of CH 4 consumption shifted downward within the soil profile during a drought. ...
... Therefore, C1 was a strong sink of CH 4 (Fig. 8b). CH 4 production and consumption can occur simultaneously, and dry soil had been reported to increase net CH 4 uptake in previous studies (Borken and Beese, 2006;Butterbach-Bahl et al., 2002;Hartmann et al., 2011). At the same time, higher CH 4 peaks in C4 (wetland and localized depressions) were caused Table 5 Cumulative nitrous oxide (kg N 2 O-N ha − 1 ) and methane (kg CH 4 -C ha − 1 ) emissions and global warming potential (kg CO 2 -C equivalent ha − 1 ) during corn (2019; 137 days) and soybean (2020; 106 days) growing seasons. ...
Article
Seasonal wetlands and depressions in agricultural fields that accumulate nutrients from runoff water might act as hotspots of nitrous oxide (N 2 O) and methane (CH 4) emissions. However, the spatiotemporal pattern of these gases from different parts of agricultural fields had not been compared. A two-year field experiment was conducted in Ontario, Canada, to test whether field locations with higher wetness act as N 2 O and CH 4 hotspots. The objectives included, i) to classify agricultural field using topographical wetness index (TWI), ii) to determine the spatiotemporal patterns of N 2 O, CH 4 , and soil properties from TWI classes; and iii) to determine the impact of soil variables on N 2 O and CH 4 emission prediction. The field was divided into four classes based on TWI, i) low TWI (C1; steep slopes), ii) medium TWI and slopes (C2), iii) Higher TWI (C3; low slopes), and iv) very high TWI (C4; seasonal wetlands and depressions). Each TWI class had six sampling points as replicates to collect soil and gas samples during corn (2019) and soybean (2020) seasons. TWI classes had a significant impact on N 2 O and CH 4 emissions. Mean maximum and minimum N2O emissions were observed during corn season from C4 (153 ± 34) and C1 (69 ± 35 µg N 2 ON m-2 h − 1), respectively. However, during soybean season, C1 had higher (70 ± 1), and C4 had lower average (26.5 ± 8 µg N 2 ON m-2 h − 1) emissions. Higher mean CH 4 emissions were observed from C4 and C1, respectively, during corn (1264 ± 778) and soybean (60 ± 44 µg CH 4-C m-2 h − 1) seasons. Regression analysis revealed that N 2 O emissions were mainly controlled by nitrate, electrical conductivity, and moisture during corn and ammonium, pH, and nitrate during soybean season. Similarly, CH 4 emissions were regulated by moisture and clay during corn season and ammonium and pH during soybean season. These relationships could help upscale greenhouse gas emissions at regional levels and formulate mitigation strategies.
... The litterfall layer plays a significant role in soil CH4 exchange with the atmosphere. It is able to control the exchange of CH4 flux with the atmosphere through controlling soil aeration and soil moisture, functioning as a barrier to gas exchange between mineral soil and the atmosphere, consuming either negligible or small amounts of atmospheric CH4 [12,51]. Although there is no direct evidence for coniferous litter, as in the present study, the fresh litter originating from green leaves could produce more CH4 by abiotic factors, such as temperature and solar radiation. ...
Article
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The contribution of litterfall (dead leaves, twigs, etc., fallen to the ground) and forest floor (organic residues such as leaves, twigs, etc., in various stages of decomposition, on the top of the mineral soil) is fundamental in both forest ecosystem sustainability and soil greenhouse gases (GHG) exchange system with the atmosphere. The effect of different thinning treatments (control-no thinning, traditional-low thinning, selective-intense thinning) on litterfall and forest floor nutrients , in relation to soil GHG fluxes, is analyzed. After one year of operations, thinning had a significant seasonal effect on both litterfall and forest floor, and on their nutrient concentrations. The intense (selective) thinning significantly affected the total litterfall production and conifer fractions, reducing them by 46% and 48%, respectively, compared with the control (no thinning) sites. In the forest floor, thinning was able to significantly increase the Fe concentration in traditional thinning by 59%, and Zn concentration in the intense thinning by 55% (compared with control). Overall, litterfall acted as a bio-filter of the gasses emitting from the forest floor, acting as a GHG regulator.
... The relationships of fine root dynamics and soil temperature, moisture, and nutrients have been widely reported, but the results of these studies are not consistent [20,[55][56][57][58][59]. In our study, thinning had a more significant effect on soil moisture than on temperature at the 0-20 cm depth, mainly because different tree species can affect soil moisture levels due to their canopy structure and canopy interactions with the atmosphere [60]. The results of this study were similar to those of Bréda et al. [26] who showed that soil moisture increased in thinned plots owing to the reduction of transpiration, which was in contrast to the findings of Mattson and Smith [24]. ...
Article
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Fine roots play an important role in plant growth as well as carbon (C) and nutrient cycling in terrestrial ecosystems. Fine roots are important for understanding the contribution of forests to the global C cycle. Knowledge about this topic is still limited, especially regarding the effects of different forest management practices. This study investigated the seasonal dynamics of fine roots (<2 mm) in masson pine (P. massoniana) plantations for one year after low intensity thinning by using a sequential soil coring method. The fine roots showed pronounced seasonal dynamics, with a peak of fine root biomass (FRB) occurring in September. Significant differences were noted in the seasonal dynamics of FRB for the different diameter size sub-classes (≤0.5 mm, 0.5–1 mm and 1–2 mm); also FRB was inversely related to soil depth. Moreover, the FRB (≤0.5 mm and 0.5–1 mm except 1–2 mm) in the thinning plots was greater than that in the control only in the upper soil layer (0–10 cm). Furthermore, the FRB varied significantly with soil temperature, moisture and nutrients depended on the diameter sub-class considered. Significant differences in the soil temperature and moisture levels were noted between low-intensity thinned and control plots. Soil nutrient levels slightly decreased after low-intensity thinning. In addition, there was a more sensitive relationship between the very fine roots (diameter < 0.5 mm) and soil nutrients. Our results showed an influence of low-intensity thinning on the fine root dynamics with a different magnitude according to fine root diameter sub-classes. These results provide a theoretical basis to promote the benefits of C cycling in the management of P. massoniana forests.
... We found that the dominant tree species had some effect on PMORs. Even though the literature indicates that spruce forest soils exhibit a lower capacity to oxidize CH 4 than beech forest soils (Borken & Beese, 2006;Degelmann et al., 2009), we could not detect significant differences between beech-dominated and coniferous forests (pine or spruce) across all forest sites. However, PMORs were lower in oak than in beech dominated forests. ...
Article
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Aerated topsoils are important sinks for atmospheric methane (CH4) via oxidation by CH4‐oxidizing bacteria (MOB). However, intensified management of grasslands and forests may reduce the CH4 sink capacity of soils. We investigated the influence of grassland land‐use intensity (150 sites) and forest management type (149 sites) on potential atmospheric CH4 oxidation rates (PMORs) and the abundance and diversity of MOB (with qPCR) in topsoils of three temperate regions in Germany. PMORs measurements in microcosms under defined conditions yielded approximately twice as much CH4 oxidation in forest than in grassland soils. High land use intensity of grasslands had a negative effect on PMORs (‐40%) in almost all regions and fertilization was the predominant factor of grassland land use intensity leading to PMOR reduction by 20%. In contrast, forest management did not affect PMORs in forest soils. USC‐α, was the dominant group of MOBs in the forests. In contrast, USC‐γ was absent in more than half of the forest soils but present in almost all grassland soils. USC‐α abundance had a direct positive effect on PMOR in forest, while in grasslands USC‐α and USC‐γ abundance affected PMOR positively with a more pronounced contribution of USC‐γ than USC‐α. Soil bulk density negatively influenced PMOR in both, forests and grasslands. We further found that the response of the PMORs to pH, soil texture, soil water holding capacity and organic carbon and nitrogen content differ between temperate forest and grassland soils. pH had no direct effects on PMOR, but indirect ones via the MOB abundances, showing a negative effect on USC‐α, and a positive on USC‐γ abundance. We conclude that reduction in grassland land‐use intensity and afforestation has the potential to increase the CH4 sink function of soils and that different parameters determine the microbial methane sink in forest and grassland soils.
... From several studies, the following trend was observed (in decreasing order of sink strength): woodland > non-cultivated upland > grassland > cultivated soils (Dobbie & Smith, 1996;Hütsch et al., 1994;Le Mer & Roger, 2001;Willison et al., 1995). More specifically, an effect of land-use change on CH 4 oxidation rates was associated to tree species (Borken & Beese, 2006;Menyailo et al., 2010;Menyailo & Hungate, 2003;Reay et al., 2001;Reay et al., 2005;Saggar et al., 2007). Different tree species had varied effects on CH 4 consumption but a common trend was that soils under hardwood species (aspen, beech, birch, oak) consumed more CH 4 than soils under coniferous species (larch, pine, spruce). ...
Thesis
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Methane (CH4) is one of the most potent greenhouse gases and its increasing concentration in the Earth’s atmosphere is linked to today’s global warming. The types of land and land-use have an impact on net CH4 fluxes, e.g. wetlands are generally net CH4 emitters while upland forest soils are a sink for CH4. This project aimed to elucidate the effect of afforestation and reforestation on net CH4 fluxes and to determine the control of the CH4-oxidising bacteria (methanotrophs) on net CH4 flux rate. This was investigated using a combination of molecular (T-RFLP, cloning/sequencing, microarray) and activity-specific (PLFA-SIP) approaches. Several sites were selected to analyse soil methanotrophs under shrubs regenerating after a fire compared to a native mature forest (in New Zealand), and under bog, grass, heath, pine and birch vegetation (in Scotland). Furthermore, a simple bottom-up approach was applied to seasonal measurements of local net CH4 fluxes in Scotland. These were upscaled to annual values in order to estimate the contribution to the national CH4 budget for each habitat investigated. The effect on CH4 mitigation of the conversion of different types of non-forested habitat to forests was then estimated. Afforestation/reforestation was always found to induce net CH4 oxidation at rates much faster than previously estimated. This preliminary analysis suggests that heathland conversion to birch forest was beneficial in term of CH4 sinks but it also induced large and permanent losses of soil C. However, bog afforestation with pine trees can potentially neutralise the national CH4 emissions from non-forested areas, while preserving soil C stocks. This project also revealed that changes in net CH4 flux due to land-use changes were closely related to shifts in the structure of the methanotrophic community. The relative abundance of members of the USCα cluster (high-affinity methanotrophs) was a strong predictor of net CH4 fluxes. Finally, the sole presence of trees suggested a niche-specific adaptation of the methanotrophs, which may have been correlated to some of the soil characteristics.
... In the undisturbed beech stand, cumulative emissions of 0.4 kg N 2 O ha −1 y −1 are in agreement with observations by Mogge et al. [27] but lower than measurements by Butterbach-Bahl et al. [77] during four consecutive years in a beech stand (1.6-10.4 kg N 2 O ha −1 y −1 ) and several other authors [78,79]. The only study quantifying N 2 O emissions from skid trails under comparable conditions reported cumulative N 2 O effluxes between 1.8 and 4.3 kg ha −1 during the growing season [2], which is in the range of our observations on the skid trail. ...
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The compaction of forest soils can deteriorate soil aeration, leading to decreased CH4 uptake and increased N2O efflux. Black alder (Alnus glutinosa) may accelerate soil structure regeneration as it can grow roots under anaerobic soil conditions. However, symbiotic nitrogen fixation by alder can have undesirable side-effects on greenhouse gas (GHG) fluxes. In this study, we evaluated the possible trade-off between alder-mediated structure recovery and GHG emissions. We compared two directly adjacent 15-year old beech (Fagus sylvatica) and alder stands (loamy texture, pH 5–6), including old planted skid trails. The last soil trafficking on the skid trails took place in 1999. GHG fluxes were measured over one year. Undisturbed plots with beech had a moderately higher total porosity and were lower in soil moisture and soil organic carbon than undisturbed alder plots. No differences in mineral nitrogen were found. N2O emissions in the undisturbed beech stand were 0.4 kg ha−1 y−1 and 3.1 kg ha−1 y−1 in the undisturbed alder stand. CH4 uptake was 4.0 kg ha−1 y−1 and 1.5 kg ha−1 y−1 under beech and alder, respectively. On the beech planted skid trail, topsoil compaction was still evident by reduced macro porosity and soil aeration; on the alder planted skid trail, soil structure of the uppermost soil layer was completely recovered. Skid trail N2O fluxes under beech were five times higher and CH4 oxidation was 0.6 times lower compared to the adjacent undisturbed beech stand. Under alder, no skid-trail-effects on GHG fluxes were evident. Multiple regression modelling revealed that N2O and CH4 emissions were mainly governed by soil aeration and soil temperature. Compared to beech, alder considerably increased net fluxes of GHG on undisturbed plots. However, for skid trails we suggest that black alder improves soil structure without deterioration of the stand’s greenhouse gas balance, when planted only on the compacted areas.
... The soil CH 4 flux was significantly correlated with WFPS in the case of Mixed Plantation as shown in Fig.4. This is in contrast to finding of [68], that the soil moisture strongly control the uptake of atmospheric CH 4 by limiting the diffusion of CH 4 into the soil, resulting in a negative correlation between soil moisture and CH 4 uptake rates under most non-drought conditions. There was high and significant correlation which is found between soil CH 4 flux and soil temperature (R 2 = -0.674, ...
... Yet, it is still challenging to explain spatial variability of GHG fluxes on the small scale (Darenova et al., 2016;Maier et al., 2017b). Studying the spatial variability of gas fluxes at the plot scale allows identifying effects of vegetation and soil properties and finding links between processes (Borken and Beese, 2006;Maier et al., 2017b;Warner et al., 2017). Maier et al. (2017b) found that CH 4 consumption and soil respiration covary spatially in a forest stand and suggested that this might be explained by the rhizosphere being the most important source of soil CO 2 and possibly a preferred habitat for methanotrophic bacteria. ...
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Forests contribute strongly to global carbon (C) sequestration and the exchange of greenhouse gases (GHG) between the soil and the atmosphere. Whilst the microbial activity of forest soils is a major determinant of net GHG exchange, this may be modified by the presence of litter through a range of mechanisms. Litter may act as a physical barrier modifying gas exchange, water movement/retention and temperature/irradiance fluctuations; provide a source of nutrients for microbes; enhance any priming effects, and facilitate macro-aggregate formation. Moreover, any effects are influenced by litter quality and regulated by tree species, climatic conditions (rainfall, temperature), and forest management (clear-cutting, fertilization, extensive deforestation). Based on climate change projections, the importance of the litter layer is likely to increase due to an litter increase and changes in quality. Future studies will therefore have to take into account the effects of litter on soil CO2 and CH4 fluxes for various types of forests globally, including the impact of climate change, insect infestation, and shifts in tree species composition, as well as a better understanding of its role in monoterpene production, which requires the integration of microbiological studies conducted on soils in different climatic zones.
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Tree species play a key role in regulating soil CH4 uptake and N2O emission through altering soil physical, chemical and microbial properties in forest ecosystem. In northeast China, about 70% of forest areas are dominated by secondary forests, and the rest are larch and other tree species plantations which were established following secondary forests being harvested. But few studies have investigated the effects of the conversion of secondary forest to larch plantation on soil CH4 and N2O fluxes. In this study, by using static chamber/ gas chromatograph techniques, we measured soil CH4 and N2O fluxes from secondary forest and adjacent larch (Larix olgensis) plantations. Four static chambers were set in each forest type. Gas samples were took every two weeks (growing season) or one month (dormant season) during June 2007 to June 2008. Soil temperature, soil moisture and soil available nitrogen content near each chamber were concurrently measured. The fluxes of soil CH4 in secondary forest and larch plantation varied from -168.8 to 22.7μg CH4 m-2 h-1 and -191.4 to - 40.5μg CH4 m-2 h-1 respectively, and the corresponding values of soil N2O were -29.1 to 34.6 μg N2O m-2 h-1 and -3 to 61.8 μg N2O m-2 h-1. The cumulative soil CH4 uptake and soil N2O fluxes in larch plantation were respectively 20% and 2.6 fold greater than those in secondary forest. Similar seasonal dynamics of soil CH4 uptake and N2O emission fluxes were presented in both secondary forest and larch plantation, showing higher fluxes in growing season but lower ones in dormant season. The fluxes of soil CH4 uptake positively correlated with soil temperatures, but negatively correlated with soil moisture. Through intercepting more rainfall in summer or melt water in spring, canopy and thicker litter can decrease soil moisture, and then enhance soil CH4 uptake in larch plantation. The fluxes of N2O emission were positively related to soil temperature and soil NH+4 -N contents, but had no significant correlation with soil-water content in both forest types. Nevertheless, thicker litter store more water during drought in spring and autumn in the larch plantation, which can increase N2O production of soil organic horizon. In conclusion, the conversion of secondary forest to larch plantation increased soil CH4 uptake and N2O emission, mainly due to litter-induced changes in spatial and temporal distribution of soil water.
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Methane (CH4) is an important anthropogenic greenhouse gas that can be produced and consumed by microorganisms in soils. We present a meta-analysis of the potential effects of environmental change on CH4 uptake by forest soils. Such effects have not been reliably estimated even though aerobic methanotrophs in forest soils are the largest biological sink for atmospheric CH4. Differences in the annual rate of CH4 uptake between forests are likely caused by differences in vegetation, microbial communities, and the physical and chemical properties of soil environments, but we found no clear different patterns at annual scale among tropical, temperate, and boreal forests. The meta-analysis indicated that the rates of CH4 uptake in forest ecosystems were significantly decreased under elevated CO2 and N enrichment, but the rates increased under drought. The effects of warming on the rates of CH4 uptake were inconsistent in forest soils, and the response ratio accordingly suggested that a warmer climate would have no significant effect on the rate of CH4 uptake. The seasonality of CH4 uptake in natural forest soils and the clear results of the drought experiments evidence the importance of soil moisture. However, our linear model did not unravel a clear negative effect of climatic water surplus nor mean annual precipitation on soil CH4 uptake. Therefore, process-based and ecosystem-specific models of CH4 flux are also warranted for predicting the responses of ecosystemic CH4 fluxes to climate change.
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The exchange processes of greenhouse gases in the soil–atmosphere system are discussed, including their production and microbial reutilization in the soil, emission from the soil surface, and consumption from the atmosphere. It was shown that the effect of soil–ecological conditions on the emission of greenhouse gases is manifested through the changes in production and consumption activities, as well as in the gases ratios. The direct measurement of CO2, CH4, and N2O fluxes gives clear understanding of gas exchange between the soil and the atmosphere and allows estimating the contribution of soil to the emission and sink of greenhouse gases and determining the activity of carbon and nitrogen transformations in the soil.
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Forest regeneration plays an important role in the carbon (C) and nitrogen (N) budget after clear‐cutting. Nonetheless, the effects of regeneration pattern on soil‐atmosphere exchange of greenhouse gases (GHG; CO2, CH4 and N2O) remain poorly understood on the eastern Qinghai‐Tibetan Plateau. This study reports measured field layer GHG fluxes from Picea asperata broadleaved mixed forest (MF, mixed forests with planted P. asperata and natural regeneration of broadleaved species), natural secondary forest (NF, natural without assisted regeneration), and P. asperata plantation forest (PF, artificial planting) to investigate the influence of regeneration patterns on soil GHG fluxes. The soils of the three forest types acted as CO2 and N2O sources and CH4 sinks. The seasonal variation in GHG fluxes was related to soil temperature, rather than soil moisture. Forest types originating from different regeneration processes exhibited different gaseous C fluxes (CO2 and CH4), but did not exhibit significant effect on N2O emissions. NF and MF had higher CO2 emissions than PF. The difference was related to soil C and N density, NH4+ concentration, and soil β‐glucosidase activity, rather than the soil microbial community. NF had higher CH4 uptake than the other two forest types, which is possibly related to specific individual phospholipid fatty acids. Overall, forest types differing in regeneration patterns had a significant impact on the C balance from the perspective of soil‐atmosphere exchange of gaseous C at our site. Therefore, the GHG fluxes should be considered when taking measures of forest management and regeneration practices in this region.
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Knowledge about the influence of terrestrial ecosystems and their regulating function as net sink or source for greenhouse-gas fluxes is limited. During the past decades, land-use and land-cover changed and thus the interactions between the terrestrial biosphere, pedosphere, and atmosphere were altered. One main objective of this experiment was to verify species-specific influences of European beech (Fagus sylvatica L.) and European ash (Fraxinus excelsior L.) saplings on greenhouse gas (GHG) fluxes between soil and atmosphere under near-natural conditions in a field experiment. The hypothesis was that high metabolic activity of fine roots induces strong species-specific effects on GHG fluxes before and during frondescence in early spring. This is due to characteristic differences in the phenological cycle of these tree species, also addressing fine root growth, which may lead to considerably different GHG fluxes. According to that the GHG emissions showed a consistent low fluxes for both tree species (14 μg N-N2O m-2 h-1) during the leafless period. Before frondescence, the GHG emissions from soil planted with F. sylvatica increased less than from soil planted with F. excelsior which increased up to 230 % (14 to ca. 80 μg N-N2O m-2 h-1) under the same soil temperature regime. During frondescence, the fluxes continued to increase and no constant emissions were observed. Generally emissions of planted soil plots were lower than those of the control. The strongest reduction of N2O emission was observed for soils planted with ash. The five gas measurements during the leafless period showed that the CH4 uptake by the soil remained constant over time. Uptake was higher for soil planted with ash than planted with beech. A trend of increasing CO2 efflux from each plant treatment was observed. Mean fluxes ranged from 30.4 ± 5.1 to 85 ± 35.4 mg C-CO2 m-2 h-1 during frondescence the measurement time. Declines of up to 60-80 %in fluxes were found. Fluxes of CO2 from plots with F. sylvatica were higher than plots with F. excelsior but not significant. On the one hand, the temporal increase of the N2O emission fromplanted soil ended after frondescence. On the other hand, CO2 emission of soils planted with beech continuously increased after the end of frondescence.
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To understand soil N2O fluxes from temperate forests in a climate-sensitive transitional zone, N2O emissions from three temperate forest types (Pinus tabulaeformis, PTT; Pinus armandii, PAT; and Quercus aliena var. acuteserrata, QAT) were monitored using the static closed-chamber method from June 2013 to May 2015 in the Huoditang Forest region of the Qinling Mountains, China. The results showed that these three forest types acted as N2O sources, releasing a mean combined level of 1.35 ± 0.56 kg N2O ha⁻¹ a⁻¹, ranging from 0.98 ± 0.37 kg N2O ha⁻¹ a⁻¹ in PAT to 1.67 ± 0.41 kg N2O ha⁻¹ a⁻¹ in QAT. N2O emission fluctuated seasonally, with highest levels during the summer for all three forest types. N2O flux had a significantly positive correlation with soil temperature at a depth of 5 cm or in the water-filled pore space, where the correlation was stronger for temperature than for the water-filled pore space. N2O flux was positively correlated with available soil nitrogen in QAT and PAT. Our results indicate that N2O flux is mainly controlled by soil temperature in the temperate forest in the Qinling Mountains.
Chapter
Temperate and boreal forest ecosystems cover approximately 13% of the world terrestrial surface and provide a wide range of ecological services to society, including a significant contribution to the regulation of atmospheric greenhouse gas concentrations. Forests do not only function as major sinks (and sources) for atmospheric carbon dioxide (CO2) but also as significant sources and sinks of other atmospheric greenhouse gases, namely, nitrous oxide (N2O) and methane (CH4). The importance of forests as regulators of atmospheric concentrations of these trace gases is undebated, but how this function might change in view of the ongoing climate and associated environmental changes remains a matter of debate. On the one hand, increases in temperature and atmospheric CO2 could lead to permafrost thaw, dramatically increasing N transformation rates in the soil and associated N2O emissions. On the other hand, declining precipitation or changes toward more episodic rainfall events might result in the opposite, through reduced N2O efflux and stimulated uptake of atmospheric CH4 by forest soils. By providing a set of examples from field and laboratory studies, we present the current knowledge and the research perspectives aiming at a better understanding of the current and future role of boreal and temperate forest soils as regulators of the atmospheric concentrations of N2O and CH4 in the frame of global change.
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From June, 2007 to October, 2009, a measurement with static chamber/gas chromatograph techniques was conducted on the soil CH4 flux in a typical secondary hardwood forest in Northeast China under the effects of different harvest disturbances, i. e., uncut (control), clear cutting (including both farming and reforestation after clear cutting), 50% stand volume removed, and 25% stand volume removed. In all of the four treatments, the soil was the sink of atmospheric CH4, but cutting decreased the soil CH4 uptake flux, with the order of uncut (-85.03 μg CH4·m-2 ·h-1) > 50% stand volume removed (-80.31 μg CH4 ·m-2 ·h-1) > 25% stand volume removed (-70.97 μg CH4 ·m-2h-1) > farming after clear cutting (-65.57 μg CH4·m-2·h-1) > reforestation after clear cutting (-62.02 μg CH4·m-2·h-1). During the study period, the seasonal patterns of the soil CH4 uptake flux in all treatments were similar, with a higher value in growth season and a lower one in winter. After the harvest disturbance, the soil temperature, humidity, and NO3--N, and NH4+-N contents were all increased, and the soil CH4 flux had a significant quadratic correlation with soil temperature, and a negative linear correlation with soil moisture content. It was suggested that the increase of the soil moisture, NO3--N, and NH4+-N contents after the forest harvest was the main cause of the decrease of the soil CH4 uptake flux.
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The development of the new process-based TRIPLEX-GHG model derives from the Integrated Biosphere Simulator (IBIS), which couples nitrification and denitrification processes to quantify nitrous oxide (N2O) emissions from natural forests and grasslands. Sensitivity analysis indicates that the nitrification rate coefficient (COENR) is the most sensitive parameter to simulate N2O emissions. Accordingly, we calibrated this parameter using data from 29 global forest sites (across different latitudes) and grassland sites. The average nitrification rate coefficient gradually increases in the order of tropical forest to grassland to temperate forest to boreal forest, and giving means of 0.009, 0.03, 0.04, and 0.09, respectively. This study validated the mean value for each ecosystem at 52 sites globally. Calibration results both indicate the good performance of the model and its suitability in capturing seasonal variation and magnitude of N2O flux; however, it is limited in modeling N2O uptake and increments during periods of snowmelt. Additionally, validation results indicate that simulated and observed annual or seasonal N2O fluxes are highly correlated (R2=0.75; P<0.01). Consequently, our results suggest that the model is suitable in simulating N2O emissions from different forest and grassland land types under varying environmental conditions on a global scale.
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Annual fluxes of N2O trace gas emissions were assessed after stratifying German forest soils into Seasonal Emission Pattern (SEP) and Background Emission Pattern (BEP). Broad-leaved forests with soil pH(KCl) ≤ 3.3 were assigned to have SEP, broad-leaved forests with soil pH(KCl) > 3.3 and all needle-leaved forests to have BEP. BEPs were estimated by a relationship between annual N2O emissions and carbon content of the O-horizon. SEPs were primarily controlled by temperature and moisture and simulated by the model Expert-N after calibration to a 9-year record of N2O measurements. Analysis with different climate and soil properties indicated that the model reacts highly sensitive to changes in soil temperature, soil moisture, and soil texture. A geographic information system (ARC/INFO) was used for a spatial resolution of 1 km × 1 km grid where land cover, dominant soil units, and hygro climate classes were combined. The mean annual N2O emission flux from German forest soils was estimated as 0.32 kg ha−1 yr−1. Broad-leaved forests with SEP had the highest emissions (2.05 kg ha−1 yr−1) followed by mixed forests (0.38 kg ha−1 yr−1), broad-leaved forests (0.37 kg ha−1 yr−1), and needle-leaved forests with BEP (0.17 kg ha−1 yr−1). The annual N2O emission from German forest soils was calculated as 3.26 Gg N2O-N yr−1. Although needle-leaved trees cover about 57% of the entire forest area in Germany, their contribution is low (0.96 Gg N2O-N yr−1). Broad-leaved forests cover about 22% of the forest area but have 55% higher emissions (1.49 Gg N2O-N yr−1) than needle-leaved. Mixed forests cover 21% of the area and contribute 0.81 Gg N2O-N yr−1. Compared to the total N2O emissions in Germany of 170 Gg N yr−1, forest soils contribute only 1.9%. However, there are some uncertainties in this emission inventory, which are intensely discussed.
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Fertilization of nutrient-depleted and degraded forest soils may be required to sustain utilization of forests. In some European countries, the application of composts may now be an alternative to the application of inorganic fertilizers because commercial compost production has increased and compost quality has been improved. There is, however, concern that compost amendments may cause increased leaching of nitrogen, trace metals and toxic organic compounds to groundwater. The objective of this study was to assess the risk of ammonium (NH4 +), nitrate (NO3 –) and dissolved organic nitrogen (DON) leaching following a single compost application to silty and sandy soils in mature beech (Fagus sylvatica L.), pine (Pinus silvestris L.) and spruce (Picea abies Karst.) forests at Solling and Unterl in Lower Saxony, Germany. Mature compost from separately collected organic household waste was applied to the soil surface at a rate of 6.3kgm–2 in the summer of 1997 and changes in NH4 +, NO3 – and DON concentrations in throughfall and soil water at 10 and 100cm soil depths were determined for 32 months. The spruce forests had the highest N inputs by throughfall water and the highest N outputs in both the control and compost plots compared with the pine and beech forests. Overall, the differences in total N outputs at 100cm soil depth between the control and compost plots ranged between 0.3 and 11.2gNm–2 for the entire 32-month period. The major leaching of these amounts occurred during the first 17 months after compost amendments, but there was no significant difference in total N outputs (–0.2 to 1.8gNm–2) between the control and compost plots during the remaining 15 months. Most of the mineral soils acted as a significant sink for NO3 – and DON as shown by a reduction of their outputs from 10 to 100cm depth. Based on these results, we conclude that application of mature compost with high inorganic N contents could diminish the groundwater quality in the first months after the amendments. A partial, moderate application of mature compost with low inorganic N content to nutrient depleted forest soils can minimize the risk of NO3 – leaching.
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Soil CH4 flux rates were determined on 28 occasions between June 1996 and July 1997 in a temperate deciduous woodland in south-west England. The effects of environmental and edaphic factors on flux rates and the effects of chronic deposition of sulphuric acid, nitric acid and ammonium sulphate were investigated. The soil was a consistent net CH4 oxidiser, with mean (n=10) oxidation rates for plots exposed to ambient throughfall ranging from 44.3 to 110.6 μg CH4 m−2 h−1 between samplings; net CH4 production was not observed. The annual mean uptake rate differed by only 6% from the annual mean flux calculated from the literature for other studies of >364 d duration in temperate and boreal deciduous woodlands. The CH4 uptake rates were correlated with soil water potential (square-root transformed), temperature and depth of organic horizon (r2=0.78, 0.30 and 0.41, respectively). Soil water potential was the best predictor of net CH4 oxidation rates and when temperature was added to the regression model no improvement in the r2 was observed. The chronic deposition of sulphuric acid stimulated net methane oxidation (P<0.05), while the chronic deposition of nitric acid and ammonium sulphate had no significant effect.
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Nitrous oxide is a greenhouse gas contributing to stratospheric ozone depletion with major sources that derive from soils. Most measurements were performed at well-aerated or anaerobic sites, excluding common hydromorphic soils (e.g., Gleysols). The main thesis of this study was that the intermediate aeration of such soils promotes N2O emissions. The investigated catena "Wildmooswald," which is little more than 200 m long, includes common temperate forest soils (n = 7) of three aeration categories (Cambisols, Gleysols, and Histosol). The influence of fluctuating water tables of the Gleysols led to distinctively higher N2O release compared to the Cambisol within the same mature Norway spruce ecosystem. Even a stable "hot spot" of N2O emissions was detected at a Histosol, where artificial drainage created a redox environment comparable to the Gleysols. Ranking the soils according to emission rate results in fairly regular doubling steps; for example, mean annual flux rates in kg N ha-1 yr-1 for the 2.5 years of measurements were -0.1, 0.4, 1.0, 1.9/1.9, 3.2, and 6.4 for Fibric Histosol, Chromic Cambisol, Endoskeletic Cambisol, Histic Gleysol 1/2, Humic Gleysol, and Sapric Histosol, respectively. The annual emission rates (0.93 kg N ha-1 yr-1) of the predominant Cambisols (63.4% of the area) are comparable to other studies, but only 34.3% of intermediately aerated soils led to a redoubling of the average to 1.86 kg N ha-1 yr-1, which is clearly higher than previously presented from temperate forests. Therefore N2O releases of soils are underestimated if soils having intermediate aeration conditions are left unconsidered.
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Rates of methane consumption were measured in subarctic coniferous and temperate mixed-hardwood forest soils, using static chambers and intact soil cores. Rates at both sites were generally between 1 and 3 mg of CH(4) m day and decreased with increasing soil water contents above 20%. Addition of ammonium (1 mumol g of soil) strongly inhibited methane oxidation in the subarctic soils; a lesser inhibition was observed for temperate forest samples. The response to nitrogen additions occurred within a few hours and was probably due to physiological changes in the active methane-consuming populations. Methane consumption in soils from both sites was stratified vertically, with a pronounced subsurface maximum. This maximum was coincident with low levels of both nitrate and ammonium in the mixed-hardwood forest soil.
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Ammonia oxidizers (family Nitrobacteraceae) and methanotrophs (family Methylococcaceae) oxidize CO and CH4 to CO2 and NH4+ to NO2-. However, the relative contributions of the two groups of organisms to the metabolism of CO, CH4, and NH4+ in various environments are not known. In the ammonia oxidizers, ammonia monooxygenase, the enzyme responsible for the conversion of NH4+ to NH2OH, also catalyzes the oxidation of CH4 to CH3OH. Ammonia monooxygenase also mediates the transformation of CH3OH to CO2 and cell carbon, but the pathway by which this is done is not known. At least one species of ammonia oxidizer, Nitrosococcus oceanus, exhibits a Km for CH4 oxidation similar to that of methanotrophs. However, the highest rate of CH4 oxidation recorded in an ammonia oxidizer is still five times lower than rates in methanotrophs, and ammonia oxidizers are apparently unable to grow on CH4. Methanotrophs oxidize NH4+ to NH2OH via methane monooxygenase and NH4+ to NH2OH via methane monooxygenase and NH2OH to NO2- via an NH2OH oxidase which may resemble the enzyme found in ammonia oxidizers. Maximum rates of NH4+ oxidation are considerably lower than in ammonia oxidizers, and the affinity for NH4+ is generally lower than in ammonia oxidizers. NH4+ does not apparently support growth in methanotrophs. Both ammonia monooxygenase and methane monooxygenase oxidize CO to CO2, but CO cannot support growth in either ammonia oxidizers or methanotrophs. These organisms have affinities for CO which are comparable to those for their growth substrates and often higher than those in carboxydobacteria. The methane monooxygenases of methanotrophs exist in two forms: a soluble form and a particulate form. The soluble form is well characterized and appears unrelated to the particulate. Ammonia monooxygenase and the particulate methane monooxygenase share a number of similarities. Both enzymes contain copper and are membrane bound. They oxidize a variety of inorganic and organic compounds, and their inhibitor profiles are similar. Inhibitors thought to be specific to ammonia oxidizers have been used in environmental studies of nitrification. However, almost all of the numerous compounds found to inhibit ammonia oxidizers also inhibit methanotrophs, and most of the inhibitors act upon the monooxygenases. Many probably exert their effect by chelating copper, which is essential to the proper functioning of some monooxygenases. The lack of inhibitors specific for one or the other of the two groups of bacteria hampers the determination of their relative roles in nature.
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Fluxes of CO 2 , CH 4 , and N 2 O from forest soils were measured with an enclosed chamber technique between October 1990 and December 1991 in a deciduous forest near Darmstadt, Germany. Flux measurements were made before and after the removal of leaves and humus layer from the forest floor, and gas fluxes from the leaves and humus alone were also measured as well as depth profiles of CH 4 , N 2 O, and soil moisture. Except for N 2 O, large seasonal variations were observed with generally higher gas fluxes during the summer. CO 2 and CH 4 fluxes were significantly dependent on changes in ambient temperature, whereas N 2 O fluxes were more affected by soil moisture. A good correlation between CO 2 production and CH 4 uptake was observed, but no relationship was found between N 2 O emissions and either CO 2 or CH 4 fluxes. Depth profiles of the CH 4 mixing ratio in soil air consistently showed an exponential decrease with depth, whereas N 2 O profiles were highly variable and appeared to be related to changes in soil moisture. The manipulated soil experiments indicate that the leaves and the humus layers contribute significantly to the soil-atmosphere exchange of trace gases. DOI: 10.1034/j.1600-0889.1998.t01-2-00003.x
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While much is known about process level control on N2O production by nitrification and denitrification, knowledge of the environmental controls responsible for site variation in annual N2O fluxes on ecosystem level is low. Our goal was to improve existing concepts of controls on N2O fluxes. We measured N2O emission weekly or biweekly during 1 year in 11 temperate forest ecosystems using closed chambers. We identified three types of forest with different temporal emission patterns: forest with seasonal, event-based and background emission patterns. Comparison of annual data sets from literature showed that most temperate forests had low N2O emissions throughout the year (background emission pattern) with mean annual fluxes of 0.39+/-0.27kgNha-1yr-1(n=21). Event-based emission patterns were observed during frost/thaw periods and after rewetting. Highest fluxes up to 72 kg N ha-1 were emitted from a drained alder forest with organic soil in 46 weeks, followed by well drained tropical and temperature forests with seasonal emission patterns and fluxes between 2-6(n=3) and 1-5kgNha-1yr-1(n=4), respectively. Seasonal emission patterns were explained by combined effect of high annual precipitations; broad leave trees; amount and structure of organic upper horizon; high mineral bulk densities; and plant community. These state variables reduce gas diffusivity so that oxygen demand by microorganism and roots exceeded oxygen supply during wet and warm periods (>10°C). The resultant upper mean level was about 100mugN2O-Nm-2h-1 in both temperate and tropical forests. Annual N2O losses of the seasonal emission type were controlled by both duration and upper mean level of the periods with high emissions. We conclude that ``short-term controls'' of climate determine the duration of high emissions, whereas ``long-term controls'' by state variables determine the difference between background and seasonal emission types.
Article
A long-term experiment was performed at two sites in the Black Forest (Germany), in which methane oxidation rates of soils of an unfertilized spruce site and of a spruce site that had been fertilized with 150kg of Nha−1 (as (NH4)2SO4) were followed seasonally over approximately three years (1994–1996). Throughout the observation period, the soil at both sites functioned exclusively as a sink for atmospheric CH4. Mean CH4 oxidation rates at both sites were almost identical in magnitude (82.2±34.6μg CH4m−2h−1 for the unfertilized site, and 84.2±31.8μg CH4m−2h−1 for the N fertilized site) during the observation period. Results from an additional small-scale N fertilization experiment indicate that high N applications to the soil of this N-limited forest resulted only in a small reduction of CH4 oxidation: less than 30% for less than 72d. The results indicate that the atmospheric CH4 uptake activity of the soils of forest ecosystems characterized by N limitation has the capacity to recover rapidly from the inhibitory effects of high inorganic N inputs. CH4 oxidation rates at both sites showed no significant diurnal variation. However, there were significant seasonal differences in the magnitude of CH4 oxidation rates at both experimental sites with high rates during summer, relative low rates during winter and intermediate rates during spring and autumn. Correlation analysis revealed that CH4 oxidation rates were positively correlated with soil temperature and negatively with soil moisture. However, at low soil temperatures (
Article
a 10-m radius of action to both sides of the skid trail. This means that skid trails make up approximately 12 Fluxes of the greenhouse gases, N2O and CH4, were measured to 16% of the total operational area. In Germany a across a skid trail at three beech (Fagus sylvatica L.) forest sites with soils of different texture. At each site three skid trails were established permanent skid trail system with a skid trial distance of by applying two passes with a forwarder. Soil compaction in the middle 20 m is recommended by the Forestry Commissions of the wheel track caused a considerable increase of N2O emissions (Anonymous, 1991) to ensure efficient wood harvesting with values elevated by up to 40 times the uncompacted ones. Compac- but also to avoid the risk of unrestricted soil trafficking tion reduced the CH4 consumption at all sites by up to 90%, and at during harvesting. the silty clay loam site its effect was such that CH4 was even released. Soil compaction by harvesting machines alters many These changes in N2O and CH4 fluxes were caused by a reduction in important soil properties, such as bulk density, aeration macropore volume and an increase of the water-filled pore space porosity (McNabb et al., 2001), hydraulic conductivity (WFPS). Additionally, the slipping of the forwarder's wheels led to
Article
We studied in situ and in the laboratory whether the organic horizon (O horizon) could act as a physical ‘buffer system’ against soil dryness and water stress for the CH4 oxidizing microbes in boreal coniferous forest soil. The laboratory experiments with samples from a Scots pine forest soil showed that the CH4 oxidation took place in the uppermost mineral soil and was not affected by removal of the O horizon (peeling) and irrigation. The removal of a thin O horizon (2–3 cm) in early June increased the mean summertime uptake of CH4 by 50% and decreased the release of CO2 by 50%. Thus, the O horizon acts as a diffusion barrier, lowering the uptake rate of atmospheric CH4. The experimental 50% increase in precipitation by irrigation (from 58 to 84 mm month−1) had only a marginal effect on the gas fluxes in both control plots and peeled plots. During the study summer two dry periods with low matric potentials (<−1 MPa) in mineral soil occurred without there being any reduction in CH4 uptake. In laboratory experiments, the gravimetric water content of 12% (−9 kPa) led to the maximum CH4 oxidation. The CH4 oxidation was still 60% of the maximum at a water content of 4% (<−1.5 MPa) and totally inhibited at a water content of 1%. The results reveal that a low soil water content is not an important factor in restricting CH4 oxidation in mineral soil of boreal forests.
Article
We present a method for extraction of active methane (CH4)-oxidizing bacteria from soil samples. The method is based on physical dispersion of bacteria from the soil particles followed by separation of bacteria and soil particles by floatation in the density media Nycodenz or Percoll. Separation on Nycodenz produced very pure bacterial suspensions while separation on Percoll produced rather impure suspensions. However, more than 60% of the methane-oxidizing activity was irreversibly inhibited in the procedure using Nycodenz compared to less than 10% irreversible inhibition when Percoll was employed. The bacterial suspensions extracted from soil can be used to study the physiology and ecology of soil bacteria that oxidize methane at atmospheric concentrations. Our data indicated that these bacteria are extremely difficult to dislodge from particles compared to the majority of bacteria in soil. Tentatively, we interpret the strong attachment to long residence time (i.e. slow turnover) of the methane-oxidizing bacteria. A slow turnover/growth rate would explain why soil disturbances, like cultivation, have a long lasting effect on the oxidation of atmospheric methane in soil.
Article
Well-drained forest soils are thought to be a significant sink for atmospheric methane. Recent research suggests that land use change reduces the soil methane sink by diminishing populations of methane oxidizing bacteria. Here we report soil CH4 uptake from ‘natural’ mature beech forests and from mature pine and spruce plantations in two study areas of Germany with distinct climate and soils. The CH4 uptake rates of both beech forests at Solling and Unterlüß were about two–three times the CH4 uptake rates of the adjacent pine and spruce plantations, indicating a strong impact of forest type on the soil CH4 sink. The CH4 uptake rates of sieved mineral soils from our study sites confirmed the tree species effect and indicate that methanotrophs were mainly reduced in the 0–5 cm mineral soil depth. The reasons for the reduction are still unknown. We found no site effect between Solling and Unterlüß, however, CH4 uptake rates from Solling were significantly higher at the same effective CH4 diffusivity. This potential site effect was masked by higher soil water contents at Solling. Soil pH (H2O) explained 71% of the variation in CH4 uptake rates of sieved mineral soils from the 0–5 cm depth, while cation exchange capacity, soil organic carbon, soil nitrogen and total phosphorous content were not correlated with CH4 uptake rates. Comparing 1998–99, annual CH4 uptake rates increased by 69–111% in the beech and spruce stands and by 5–25% in the pine stands, due primarily to differences in growing season soil moisture. Cumulative CH4 uptake rates from November throughout April were rather constant in both years. The CH4 uptake rates of each stand were separately predicted using daily average soil matric potential and a previously developed empirical model. The model results revealed that soil matric potential explains 53–87% of the temporal variation in CH4 uptake. The differences between measured and predicted annual CH4 uptake rates were less than 10%, except for the spruce stand at Solling in 1998 (17%). Based on data from this study and from the literature, we calculated a total reduction in the soil CH4 sink of 31% for German forests due in part to conversion of deciduous to coniferous forests.
Article
This paper reports the range and statistical distribution of oxidation rates of atmospheric CH4 in soils found in Northern Europe in an international study, and compares them with published data for various other ecosystems. It reassesses the size, and the uncertainty in, the global terrestrial CH4 sink, and examines the effect of land-use change and other factors on the oxidation rate. Only soils with a very high water table were sources of CH4; all others were sinks. Oxidation rates varied from 1 to nearly 200 μg CH4 m−2 h−1; annual rates for sites measured for ≥1 y were 0.1–9.1 kg CH4 ha−1 y−1, with a log-normal distribution (log-mean ≈ 1.6 kg CH4 ha−1 y−1). Conversion of natural soils to agriculture reduced oxidation rates by two-thirds –- closely similar to results reported for other regions. N inputs also decreased oxidation rates. Full recovery of rates after these disturbances takes > 100 y. Soil bulk density, water content and gas diffusivity had major impacts on oxidation rates. Trends were similar to those derived from other published work. Increasing acidity reduced oxidation, partially but not wholly explained by poor diffusion through litter layers which did not themselves contribute to the oxidation. The effect of temperature was small, attributed to substrate limitation and low atmospheric concentration. Analysis of all available data for CH4 oxidation rates in situ showed similar log-normal distributions to those obtained for our results, with generally little difference between different natural ecosystems, or between short-and longer-term studies. The overall global terrestrial sink was estimated at 29 Tg CH4 y−1, close to the current IPCC assessment, but with a much wider uncertainty range (7 to > 100 Tg CH4 y−1). Little or no information is available for many major ecosystems; these should receive high priority in future research.
Article
The effect of superficial liming of acidic forest soils on CO2 and N2O emissions and CH4 uptake was investigated with closed chambers in two deciduous and two spruce forests, by weekly to biweekly measurements over at least one year. The flux rates of untreated areas varied between 1.94 and 4.38 t CO2-C/ha per y, 0.28 and 2.15 kg/N2O-N/ha per y and between 0.15 and 1.06 kg CH4-C/ha per y. Liming had no clear effect on CO2 emissions which may change in the long-term with decreasing root turnover and increasing C-mineralization. Apart from one exception, liming resulted in a reduction of N2O emissions by 9 to 62% and in an increase of CH4 uptake by 26 to 580%. The variability in N2O emissions between the forest sites could not be explained. In contrast, the variability of annual CH4 uptake rates could be explained by N content (r2= 0.82), C content (r2= 0.77), bulk density (r2= 60), pore space (r2= 0.59) and pH (r2= 0.40) of mineral soil at a depth of 0 to 10 cm, and by the quantity of material in the organic layer (r2= 0.66). Experiments with undisturbed columns of the same soils showed that between 1 and 73% of the total N2O emissions came from the organic layer. However, atmospheric CH4 was not oxidized in this layer, which represents a diffusion barrier for atmospheric CH4. When this barrier was removed, CH4 uptake by the mineral soil increased by 25 to 171%. These results suggest that liming of acidic forest soils causes a reduction of the greenhouse gases N2O and CH4 in the atmosphere, due to changes in the chemical, biological, and physical condition of the soils.
Article
N2O emission rates were measured during a 13-month period from July 1981 till August 1982 with a frequency of once every two weeks at six different forest sites in the vicinity of Mainz, Germany. The sites were selected on the basis of soil types typical for many of the Central European forest ecosystems. The individual N2O emission rates showed a high degree of temporal and spatial variabilities which, however, were not significantly correlated to variabilities in soil moisture content or soil temperatures. However, the N2O emission rates followed a general seasonal trend with relatively high values during spring and fall. These maxima coincided with relatively high soil moisture contents, but may also have been influenced by the leaf fall in autumn. In addition, there was a brief episode of relatively high N2O emission rates immediately after thawing of the winter snow. The individual N2O emission rates measured during the whole season ranged between 1 and 92 g N2O-N m–2 h–1. The average values were in the range of 3–11 g N2O-N m–2 h–1 and those with a 50% probability were in the range of 2–8 g N2O-N m–2 h–1. The total source strength of temperate forest soils for atmospheric N2O may be in the range of 0.7–1.5 Tg N yr–1.
Article
Methane uptake to soil was examined in individual chambers at three small forest catchments with different treatments, Control, Limed and Nitrex sites, where N-deposition was experimentally increased. The catchments consisted of both well-drained forest and wet sphagnum areas, and showed uptake of CH4 from the ambient air. The lowest CH4 uptakes were observed in the wet areas, where the different treatments did not influence the uptake rate. In the well-drained areas the CH4 uptakes were 1.6, 1.4 and 0.6 kg ha–1 year–1 for the Limed, Control and Nitrex sites, respectively. The uptake of methane at the well-drained Nitrex site was statistically smaller than at the other well-drained catchments. Both acidification and increase in nitrogen in the soil, caused by the air-borne deposition, are the probable cause for the reduction in the methane uptake potential. Uptake of methane was correlated to soil water content or temperature for individual chambers at the well-drained sites. The uptake rate of methane in soil cores was largest in the 0- to 10-cm upper soil layer. The concentration of CH4 in the soil was lower than the atmospheric concentration up to 30 cm depth, where methane production occurred. Besides acting as a sink for atmospheric methane, the oxidizing process in soil prevents the release of produced methane from deeper soil layers reaching the atmosphere.
Article
During 4 years continuous measurements of N-trace gas exchange were carried out at the forest floor-atmosphere interface at the Hglwald Forest that is highly affected by atmospheric N-deposition. The measurements included spruce control, spruce limed and beech sites. Based on these field measurements and on intensive laboratory measurements of N2-emissions from the soils of the beech and spruce control sites, a total balance of N-gas emissions was calculated. NO2-deposition was in a range of –1.6 –2.9 kg N ha–1 yr–1 and no huge differences between the different sites could be demonstrated. In contrast to NO2-deposition, NO- and N2O-emissions showed a huge variability among the different sites. NO emissions were highest at the spruce control site (6.4–9.1 kg N ha–1 yr–1), lowest at the beech site (2.3–3.5 kg N ha–1 yr–1) and intermediate at the limed spruce site (3.4–5.4 kg N ha–1 yr–1). With regard to N2O-emissions, the following ranking between the sites was found: beech (1.6–6.6 kg N ha–1 yr–1) >> spruce limed (0.7–4.0 kg N ha–1 yr–1) > spruce control (0.4–3.1 kg N ha–1 yr–1). Average N-trace gas emissions (NO, NO2, N2O) for the years 1994–1997 were 6.8 kg N ha–1 yr–1 at the spruce control site, 3.6 kg N ha–1 yr–1 at the limed spruce site and 4.5 kg N ha–1 yr–1 at the beech site. Considering N2-losses, which were significantly higher at the beech (12.4 kg N ha–1 yr–1) than at the spruce control site (7.2 kg N ha–1 yr–1), the magnitude of total gaseous N losses, i.e. N2-N + NO-N + NO2-N + N2O-N, could be calculated for the first time for a forest ecosystem. Total gaseous N-losses were 14.0 kg N ha–1 yr–1 at the spruce control site and 15.5 kg N ha–1 yr–1 at the beech site, respectively. In view of the huge interannual variability of N-trace gas fluxes and the pronounced site differences in N-gas emissions it is concluded that more research is needed in order to fully understand patterns of microbial N-cycling and N-gas production/emission in forest ecosystems and mechanisms of reactions of forest ecosystems to the ecological stress factor of atmospheric N-input.
Article
Elevated nitrogen deposition has increased tree growth, the storage of soil organic matter, and nitrate leaching in many European forests, but little is known about the effect of tree species and nitrogen deposition on nitrous oxide emission. Here we report soil N2O emission from European beech, Scots pine and Norway spruce forests in two study areas of Germany with distinct climate, N deposition and soils. N2O emissions and throughfall input of nitrate and ammonium were measured biweekly during growing season and monthly during dormant season over a 28months period. Annual N2O emission rates ranged between 0.4 and 1.3kg N ha−1year−1 among the stands and were higher in 1998 than in 1999 due to higher precipitation during the growing season of 1998. A 2-way-ANOVA revealed that N2O fluxes were significantly higher (p<0.001) at Solling than at Unterlüß while tree species had no effect on N2O emissions. Soil texture and the amount of throughfall explained together 94% of the variance among the stands, indicating that increasing portions of silt and clay may promote the formation of N2O in wet forest soils. Moreover, cumulative N2O fluxes were significantly correlated (r2=0.60, p<0.001) with cumulative NO3− fluxes at 10cm depth as an indicator of N saturation, however, the slope of the regression curve indicates a rather weak effect of NO3− fluxes on N2O emissions. N input by throughfall was not correlated with N2O emissions and only 1.6–3.2% of N input was released as N2O to the atmosphere. Our results suggest that elevated N inputs have little effect on N2O emissions in beech, spruce and pine forests.
Article
Production of C2H4, but not of CH4, was observed in anoxically incubated soil samples (cambisol on loamy sand) from a deciduous forest. Ethylene production was prevented by autoclaving, indicating its microbial origin. Ethylene production gradually decreased from 4 to 12 cm soil depth and was not affected by moisture or addition of methionine, a possible precursor of C2H4. Oxidation of atmospheric CH4 in soil samples was inhibited by C2H4. Ethylene concentrations of 3, 6 and 10 μl l−1 decreased CH4 uptake by 21, 63 and 98%, respectively. Methionine and methanethiol, a possible product of methionine degradation, also inhibited CH4 oxidation. Under oxic conditions, C2H4 was consumed in the soil samples. Ethylene oxidation kinetics exhibited two apparent Km values of 40 μl l−1 and 12,600 μl l−1 suggesting the presence of two different types of C2H4-oxidizing microorganisms. Methanotrophic bacteria were most probably not responsible for C2H4 oxidation, since the maximum of C2H4 oxidation activity was localized in soil layers (2–8 cm depth) above those (8–10 cm depth) of CH4 oxidation activity. Our observations suggest that C2H4 production in the upper soil layers inhibits CH4 oxidation, thus being one reason for the localization of methanotrophic activity in deeper soil layers.
Article
In a 140 year-old beech forest with undergrowth of Allium ursinum, field measurements of N2O and CO2 emissions in conjunction with measurements of microbial biomass-N, extractable mineral nitrogen and NO3−-leaching were made during four vegetation growth periods. We examined whether pulses of nitrate leaching could be accompanied by enhanced N2O emission rates. Highest N2O emission rates (>150 μg N m−2 h−1) were recorded during July, when substantial nitrate leaching also was evident from ion exchange resins and suction cup lysimeters. These nitrogen losses were preceded by mineralisation of decaying Allium leaves and microbial proliferation in June. In July, a significant decline of microbial biomass nitrogen occurred and up to 113 kg N ha−1 were released. Microbial biomass carbon, as determined from substrate induced respiration, also declined in July. With this method, we identified recurring cycles of microbial growth triggered by soil wetting. Soil microbial biomass carbon related inversely to concentrations of extractable sugar carbon substrates. Our study suggests that within nitrogen-enriched forests, nitrate leaching and N2O emissions may be linked during the plant growing season. Nitrogen losses appeared to be strongly affected by biomass turnover and microbial mineralisation.
Article
Methane consumption by temperate forest soils is a major sink for this important greenhouse gas, but little is known about how tree species influence CH4 uptake by soils. Here, we show that six common tree species in Siberian boreal and temperate forests significantly affect potential CH4 consumption in laboratory microcosms. Overall, soils under hardwood species (aspen and birch) consumed CH4 at higher rates than soils under coniferous species and grassland. While NH4+ addition often reduces CH4 uptake, we found no effect of NH4+ addition, possibly because of the relatively high ratio of CH4-to-NH4+ in our incubations. The effects of soil moisture strongly depended on plant species. An increase in soil moisture enhanced CH4 consumption in soils under spruce but had the opposite effect under Scots pine and larch. Under other species, soil moisture did not affect CH4 consumption. These results could be explained by specific responses of different groups of CH4-oxidizing bacteria to elevated moisture.
Article
Aqueous extracts of forest soils inhibited atmospheric methane consumption by boreal and temperate forest soils by up to 100%. Extracts from the upper soil layers (0–5 cm) were generally inhibitory, while those from deeper in the soil column (5–12 cm) were not. The inhibitory effect was concentration-dependent and transient, becoming insignificant after as little as 3 d of exposure of soil to the aqueous extracts. Ammonium concentration alone could not explain the inhibitory effect and treatment with activated charcoal suggested involvement of an organic component. Methane oxidation by pure cultures of the methanotrophs Methylosinus trichosporium OB3b and Methylobacter luteus was significantly inhibited by the aqueous extracts of upper, but not lower soil layers. Removal of phenolic compounds by polyvinylpolypyrrolidone alleviated inhibition in the pure cultures but not in a forest soil. The results support the hypothesis that naturally occurring substances may prevent methane consumption in the upper layers of forest soils.
Article
Fluxes of CO2, CH4, and N2O from forest soils were measured with an enclosed chamber technique between October 1990 and December 1991 in a deciduous forest near Darmstadt, Germany. Flux measurements were made before and after the removal of leaves and humus layer from the forest floor, and gas fluxes from the leaves and humus alone were also measured as well as depth profiles of CH4, N2O, and soil moisture. Except for N2O, large seasonal variations were observed with generally higher gas fluxes during the summer. CO2 and CH4 fluxes were significantly dependent on changes in ambient temperature, whereas N2O fluxes were more affected by soil moisture. A good correlation between CO2 production and CH4 uptake was observed, but no relationship was found between N2O emissions and either CO2 or CH4 fluxes. Depth profiles of the CH4 mixing ratio in soil air consistently showed an exponential decrease with depth, whereas N2O profiles were highly variable and appeared to be related to changes in soil moisture. The manipulated soil experiments indicate that the leaves and the humus layers contribute significantly to the soil-atmosphere exchange of trace gases.
Article
Ammonia oxidizers (family Nitrobacteraceae) and methanotrophs (family Methylococcaceae) oxidize CO and CH4 to CO2 and NH4+ to NO2-. However, the relative contributions of the two groups of organisms to the metabolism of CO, CH4, and NH4+ in various environments are not known. In the ammonia oxidizers, ammonia monooxygenase, the enzyme responsible for the conversion of NH4+ to NH2OH, also catalyzes the oxidation of CH4 to CH3OH. Ammonia monooxygenase also mediates the transformation of CH3OH to CO2 and cell carbon, but the pathway by which this is done is not known. At least one species of ammonia oxidizer, Nitrosococcus oceanus, exhibits a Km for CH4 oxidation similar to that of methanotrophs. However, the highest rate of CH4 oxidation recorded in an ammonia oxidizer is still five times lower than rates in methanotrophs, and ammonia oxidizers are apparently unable to grow on CH4. Methanotrophs oxidize NH4+ to NH2OH via methane monooxygenase and NH4+ to NH2OH via methane monooxygenase and NH2OH to NO2- via an NH2OH oxidase which may resemble the enzyme found in ammonia oxidizers. Maximum rates of NH4+ oxidation are considerably lower than in ammonia oxidizers, and the affinity for NH4+ is generally lower than in ammonia oxidizers. NH4+ does not apparently support growth in methanotrophs. Both ammonia monooxygenase and methane monooxygenase oxidize CO to CO2, but CO cannot support growth in either ammonia oxidizers or methanotrophs. These organisms have affinities for CO which are comparable to those for their growth substrates and often higher than those in carboxydobacteria. The methane monooxygenases of methanotrophs exist in two forms: a soluble form and a particulate form. The soluble form is well characterized and appears unrelated to the particulate. Ammonia monooxygenase and the particulate methane monooxygenase share a number of similarities. Both enzymes contain copper and are membrane bound. They oxidize a variety of inorganic and organic compounds, and their inhibitor profiles are similar. Inhibitors thought to be specific to ammonia oxidizers have been used in environmental studies of nitrification. However, almost all of the numerous compounds found to inhibit ammonia oxidizers also inhibit methanotrophs, and most of the inhibitors act upon the monooxygenases. Many probably exert their effect by chelating copper, which is essential to the proper functioning of some monooxygenases. The lack of inhibitors specific for one or the other of the two groups of bacteria hampers the determination of their relative roles in nature.