Figure - available from: Biogeochemistry
This content is subject to copyright. Terms and conditions apply.
Sampling design at the study site ‘Sophienhöhe’. 35 year-old afforested monocultural stands of Douglas fir (Pseudotsuga menziesii), black pine (Pinus nigra), European beech (Fagus sylvatica) and red oak (Quercus rubra) were investigated. They are located on the western exposed slopes (inclination: 22.2° ± 2.2°) of the spoil heap. Each stand is subdivided in six to ten plots with a size of 1780 ± 660 m² by skid trails established in slope line. For each of the four tree stands, five plots were selected for sampling (light grey circles) of the forest floor (grey rectangles), mineral soil (grey rectangles), roots (dark grey circles) and litterfall (litter trap)
Source publication
The knowledge of tree species dependent turnover of soil organic matter (SOM) is limited, yet required to understand the carbon sequestration function of forest soil. We combined investigations of 13C and 15N and its relationship to elemental stoichiometry along soil depth gradients in 35-year old monocultural stands of Douglas fir (Pseudotsuga men...
Citations
... Garten et al. (2000) reported strong negative correlations between δ 13 C and the logarithm of SOC concentrations at different depths, and they proposed that the slope of this relationship (β) represents the rate of microbial processing of SOC down the soil profile. While this β-index has proven to be robust in several studies (e.g., Garten, 2006;Lorenz et al., 2020;Marty et al., 2015b), it is based on the unverified assumption that the rate of SOM migration down the soil profile is related to the rate of microbial processing. For this reason, the β-index may be imprecise, as several pedogenic processes, such as bioturbation and podzolization, result in SOC migration independently from microbial processing. ...
... Bulk soil organic C and total N concentrations are among parameters that are regularly assessed in forest ecosystem research to analyze soil organic matter (SOM) pools and ecosystem development. Furthermore, stoichiometric ratios such as the carbon:nitrogen (C:N) ratio and stable isotope composition (δ 13 C and δ 15 N) of SOM also provide a powerful tool for investigating spatial and temporal SOM dynamics and particularly, SOM turnover and stability, including fire disturbances [67][68][69][70]. ...
... Forest soils are characterized by the continuous inputs of fresh plant litter and roots that are steadily mixed and undergo microbial decomposition downward the soil profile [71][72][73]. Our data clearly demonstrate that Albic Podzols under pristine and fireaffected pine forests are supplied by a litter fall containing wide C:N and 13 C and 15 N depleted organic matter, as it was shown earlier for boreal and temperate forests [68,70]. With increasing soil depths and the aging of SOM [74], the content of C and N and C:N ratios in forest soils tend to decrease, and, in opposite, δ 13 C and δ 15 N show a trend toward enrichment by heavier isotopes [67][68][69][70]. ...
... Our data clearly demonstrate that Albic Podzols under pristine and fireaffected pine forests are supplied by a litter fall containing wide C:N and 13 C and 15 N depleted organic matter, as it was shown earlier for boreal and temperate forests [68,70]. With increasing soil depths and the aging of SOM [74], the content of C and N and C:N ratios in forest soils tend to decrease, and, in opposite, δ 13 C and δ 15 N show a trend toward enrichment by heavier isotopes [67][68][69][70]. These depth patterns are specific in Albic Podzols as the eluvial E horizon lying below an organic layer is strongly depleted by C and N in comparison to the deeper illuvial Bs horizon [15]. ...
Fires are one of the most widespread factors of changes in the ecosystems of boreal forests. The paper presents the results of a study of the morphological and physicochemical properties and soil organic matter (SOM) of Albic Podzols under pine forests (Pinus sylvestris L.) of the middle taiga zone of Siberia (Krasnoyrsky kray) with various time passed after a surface fire (from 1 to 121 years ago). The influence of forest fires in the early years on the chemical properties of Albic Podzols includes a decrease in acidity, a decrease in the content of water-soluble compounds of carbon and nitrogen and an increase in the content of light polycyclic aromatic hydrocarbons (PAHs) in organic and upper mineral horizons. Podzols of pine forests that were affected by fires more than forty-five years ago are close to manure forest soils according to most physical and chemical properties. Significant correlations were found between the thickness (r = 0.75, p < 0.05), the moisture content (r = 0.90, p < 0.05) of organic horizons and the content of ∑PAHs in the organic horizon (r = −0.71, p < 0.05) with the time elapsed after the fire (i.e., from 1 to 121 years). The index of the age of pyrogenic activity (IPA) calculated as the ratio of ∑ PAHs content in the organic horizon to ∑ PAHs at the upper mineral horizon is significantly higher in forests affected by fires from 1 to 23 years than for plots with «older» fires (45-121 years). Thus, the article presents the conserved and most changing factors under the impact of fires in the boreal forests of Russia.
... As soil moisture in our experiment was higher throughout the year under F. sylvatica than P. abies -a trend that became more pronounced under drought (Grams et al., 2021) -we would expect higher C content in HF in the topsoil under F. sylvatica compared to P. abies. An additional valuable tool to identify SOM stability makes use of the relation between the vertical enrichment of 13 C and the simultaneous decrease of SOC with depth (Acton et al., 2013;Brunn et al., 2014;Lorenz et al., 2020). The extent of SOC decomposition can be approximated from the slopes of linear relationships between δ 13 C values and log 10 C content and these so-called beta values can be interpreted both in terms of C processing, as well as the potential for C to form organomineral associations (Brunn et al., 2017). ...
Reduced carbon assimilation by trees is often considered to lower the overall carbon sink function of drought-stressed forests. However, soil organic carbon (SOC) stocks may respond differently to drought than ecosystem carbon flux dynamics, leading to imprecise predictions of soil carbon sequestration when one value is inferred from the other. As a major component of soil organic matter, SOC is the largest actively cycling terrestrial carbon reservoir, and thus fulfills various important ecosystem services. Yet, there is uncertainty about how SOC quantity and quality respond to drought in temperate forests. This study addressed the depth distribution of SOC stocks and soil organic matter stability in a forest exposed to artificial drought for five consecutive growing seasons below clusters of temperate mature deciduous beech (Fagus sylvatica L.) and coniferous spruce (Picea abies (L.) Karst.). In addition to SOC stock determination, we measured concentrations of water-extractable organic carbon (WEOC), performed density fractionation, and determined beta values of SOC (slopes of linear regressions between δ 13 C of soil and log-transformed SOC content throughout soil depth profiles). Following drought, SOC stocks down to 30 cm depth increased by a factor of 1.5 under P. abies while they did not change with drought under F. sylvatica. Under both species, SOC stocks in the mineral topsoil (0-5 cm soil depth) increased by >80 % with drought, increasing the relative contribution of this thin depth section to total SOC from 5 % to >30 %. At 5-15 cm soil depth, SOC stocks decreased with drought under F. sylvatica but not under P. abies. With drought, carbon in the free light fraction (fLF) increased under F. sylvatica but declined marginally under P. abies. Results from density fractionation and beta values suggest decreased soil organic matter stability under F. sylvatica and increased stability under P. abies. Greater SOC accumulation suggests that the belowground carbon sink strength of drought-stressed forests increases, which contrasts with reduced ecosystem carbon uptake under drought.
... However, Wang et al. (2014) found that biochar increased labile organic C only in the first month after application, and Anderson et al. (2011) found that microbial abundances in soils significantly increased 12 weeks after biochar application, which suggested that, in the short term, biochar could also accelerate the degradation of SOC through the release of labile organic C from biochar and providing a favour environment for microbes. In addition, the prevalence of SOC decreases and δ 13 C increases with soil depth has promoted the use of the δ 13 C value as an indicator for the formation and alteration of SOC pools (Nguyen et al. 2018;Lyu et al. 2019;Lorenz et al. 2020); accordingly, soil δ 13 C might vary in response to the impacts of biochar application on soil C pools. ...
... This result also indicated that the short-term "positive priming" of biochar on soil C and N pools was significant only at the 0-5 cm depth and after 3 months of biochar application. Accordingly, in contrast to soil total C, soil δ 13 C, which is usually combined with SOC as a proxy for evaluating SOM turnover (Lorenz et al. 2020), increased with biochar application rates. Moreover, our study site was located in an urban forest and close to a motorway; therefore, fuel combustion from vehicles was one of the main sources of NOx (Bai et al. 2012), and negative δ 15 N values were detected in the topsoil after 3 months of biochar application in our study. ...
... Biochar effectively regulated the processes of N cycling and SOM turnover, which was characterized by the linear relationship between δ 15 N and δ 13 C, although generally, biochar does not significantly affect soil C and N pools (Lyu et al. 2019;Lorenz et al. 2020). Increased soil labile pools that were derived from the stimulation of microorganisms by biochar might have resulted in a dominance of labile pools during the processes of SOM turnover and N cycling in the sixth month after biochar application, and this result also suggested the key role of the duration after biochar application in affecting SOM turnover and N cycling processes. ...
Purposes
Biochar has received widespread attention as a means for improving carbon (C) sequestration and soil fertility over the long term. However, information on its short-term effects on the soil C and nitrogen (N) pools is scarce, particularly in poor soils that are subjected to prescribed burning.
Materials and methods
In an effort to better understand the short-term effects of biochar on the soil C and N pools, a half-year field study was conducted in a suburban forest that is subjected to prescribed burning in subtropical Australia. In this experiment, biochar was applied to the soil once at rates of 0, 5 and 10 t ha⁻¹, and soil samples were collected for the top 20 cm soil profile under the canopies of leguminous Acacia leiocalyx (A. leiocalyx) and Acacia disparimma (A. disparimma) in the third month (August 2019) and the sixth month after biochar application (November 2019). At this site, we measured soil total C, total N, δ¹³C and δ¹⁵N.
Results
We observed that biochar generally impacted the soil C and N pools in the third month after biochar application: soil total C, particularly at the 0–5 cm depth, significantly decreased with increased biochar application rates. Soil C and N pools, particularly at the 10–20 cm depth, varied with sampling times, and soil total C and N under the A. leiocalyx canopy were significantly higher, while soil δ¹³C and δ¹⁵N were lower in the sixth month relative to the third month. Soil δ¹³C and δ¹⁵N were primarily linearly related to soil total C and N in the third month, while the linear relationship was closer than that between soil δ¹³C and δ¹⁵N and the labile C and N pools in the sixth month, which were regulated by biochar application rates.
Conclusions
Biochar application significantly decreased the soil C and N pools at the 0–5 cm depth in the third month after biochar application. The soil C and N pools and soil labile C and N pools were responsible for the changes in the processes of soil organic matter (SOM) turnover and N cycling that were revealed by soil δ¹³C and δ¹⁵N, and the changes were governed by the biochar application rates and the time elapsed after biochar application. The influence of understorey legume Acacia species, particularly A. leiocalyx, on N inputs and C sequestration in the poor forest soils was significantly enhanced in the sixth month after biochar application.
... It was unexpected to observe the highest C:N ratio of soils under BEF (Table 2). Indeed, the relatively low C:N ratio of beech residues is commonly recognized [119,120]. The high C:N ratio due to the lowest TN content found in the soils under BEF might be attributable to the fast degradation rate of such residues [121,122]. ...
Pedodiversity is considered the cornerstone of biodiversity. This work aimed to (1) assess pedodiversity according to vegetation, topographic factors, and lithology and to (2) identify the major soil-forming factors on soil organic matter (SOM) stock at a 0–30 cm depth. These goals were reached using data from 147 georeferenced soil profiles distributed along 400–1000 m (≤1000) and 1000–2134 m (>1000) altitudinal gradients in the northern part of the Apennine chain in Italy. Soils showed mainly weak or incipient development (i.e., Entisols and Inceptisols), which could be attributed to sand-based lithology, high slope gradients, and low SOM accumulation rates, which promote soil erosion processes. However, higher pedodiversity was observed at >1000 m than at ≤1000 m, likely due to the higher vegetation cover diversity and climate variability; Spodosols and Mollisols were also found. A greater SOM stock was found at >1000 than ≤1000 m, and vegetation seemed to not affect SOM amounts, suggesting a greater influence of climate on SOM content compared to vegetation. Considering ecosystem conservation, the observed spatial pedodiversity could be considered a critical basis for the protection of soil resources and pedodiversity itself in mountain regions.
... Анализ состава стабильных изотопов углерода (δ 13 С) представляет собой один из важных методологических подходов к исследованию пространственно-временной вариабельности почвенного органического вещества (ПОВ) [18,20]. δ 13 С рассматривается в качестве интегрального показателя процессов трансформации органического вещества [16] и, таким образом, имеет значительный потенциал для оценки динамики почвенного углерода [16,21]. ...
Изучены пространственные и внутрипрофильные вариации состава стабильных изотопов углерода органического вещества почв центральной части западного побережья озера Байкал. Территория характеризуется контрастной ландшафтной структурой и вариативностью климатических условий, отражающихся на составе стабильных изотопов углерода почв. Значения δ13С органического вещества и опада находятся в диапазоне от –27,93 до –18,19‰ и свидетельствуют о преобладании растительности с С3-типом фото-
синтеза. Тем не менее в степных ландшафтах отмечены единичные представители растений с С4- и CAM-фотосинтезом. Значения δ13С возрастают в направлении от лесных почв предгорий Приморского хребта
к степным почвам Приольхонского плато. Такая тенденция отражает снижение влагообеспеченности, являющейся основным лимитирующим фактором развития почв Приольхонья и определяющей через дискриминацию 13С в растительных тканях состав стабильных изотопов углерода органического вещества почв. Вне зависимости от условий педогенеза для почв исследуемой территории характерно снижение значений δ13С с глубиной. Однако выраженность такого градиента определяется локальными сочетаниями
факторов почвообразования. Исходя из различий исследуемых почв по коэффициентам наклона линейных регрессий (β), предполагается более интенсивный оборот углерода в почвах склонов северо-западных
экспозиций, а также прибрежных ландшафтов и отрицательных форм рельефа, где влияние воздушных масс с озера Байкал обусловливает меньшее иссушение профиля в летний период и обеспечивает более
благоприятный гидротермический режим почв для микробиологической активности. При этом вариации β не сопровождаются существенными колебаниями в значениях C:N и pH, что может свидетельствовать о
несущественной роли внутрипочвенных факторов и перекрытии их влияния эффектом влагодефицита на интенсивность оборота углерода в почвах Приольхонья.
... The composition of stable carbon isotopes (δ 13 С) is one of the important characteristics of soil organic matter (SOM) and is considered an integral indicator of the transformation processes of organic matter [16]. Thus, its analysis is crucial for the study of SOM spatiotemporal variability [18,20] and has a significant potential for assessing the dynamics of soil carbon [16,21]. ...
Spatial and depth-profile variations in stable carbon isotopic composition of soil organic matter have been studied in the central part of the western coast of Lake Baikal. The contrasting landscape structure and significant climatic variability of the area strongly affect the soil stable carbon isotopic composition. The δ13С values of organic matter and litter vary in the range from –27.93 to –18.19‰ and indicate the predominance of C3-pathway vegetation. However, in the steppe landscapes, single representatives of plants with C4 and CAM photosynthesis types have been noted. The δ13С values increase in the direction from the forest soils of the foothills of the Primorsky Range to the steppe soils of the Olkhon Plateau. This trend reflects a
decrease in humidity, the main limiting factor of the soil development in the Olkhon region. Insufficient moisture determines the stable carbon isotopic composition of soil organic matter through 13C discrimination in plant tissues. Regardless of the soil-forming conditions, δ13С values increase with the depth in the soils of
the studied area. However, the gradient rates are determined by local combinations of environmental factors. According to the differences in the slope coefficients of linear regressions (β) in the studied soils, more intensive carbon turnover is assumed in the soils of coastal landscapes, negative landforms, and the slopes of northwestern exposures. Under such conditions, air masses from Lake Baikal cause a significantly lower drying of the soil profile in summer and provide a more favorable water and temperature regime for microbiological activity. At the same time, β variations are not accompanied by significant fluctuations in C/N ratio and pH values, which may indicate an insignificant role of edaphic factors and overlapping of their influence by the effect of moisture deficiency on the carbon turnover intensity in the soils of the Olkhon region.
... Instead, vertical changes in either δ 13 C or δ 15 N of forest soils have been extensively studied (Lorenz et al. 2020 and references therein), and some studies further investigated co-variations in the δ 13 C and δ 15 N of soils across depth (Bohlen et al. 2004;Billings and Richter 2006;Boström et al. 2007;Bekele et al. 2013). Vertical distributions of δ 13 C and δ 15 N are unique features of natural forest soils that have rarely been disturbed, unlike croplands and grasslands (Han et al. 2020). ...
This review analyzes the data on co-variations in δ¹³C and δ¹⁵N of soils with land-use types, management, and disturbance obtained from literature to explore potential implications of the dual isotopes in the study of soil organic matter (SOM) sources and C and N processes. Overall, croplands (δ¹³C and δ¹⁵N were − 20.3 ± 4.4‰ and + 7.6 ± 4.4‰, respectively) had greater isotopic values than grasslands (‒26.3 ± 3.0‰ and + 5.4 ± 1.1‰, respectively) and forests (− 26.0 ± 1.1‰ and + 4.3 ± 2.2‰, respectively). For intensively managed lands such as croplands and grasslands, application of organic inputs such as manure and compost of which isotopic signatures differed from the indigenous SOM was the main driver of co-variations in the δ¹³C and δ¹⁵N of SOM. For natural forests, both δ¹³C and δ¹⁵N of SOM co-increased with soil depth, reflecting heavy isotope enrichment during microbial stabilization of SOM and the potential influence of ¹³C-depleted atmospheric CO2 and ¹⁵N-depleted N deposition on the upper soils. Such vertical co-enrichments of ¹³C and ¹⁵N were disturbed by a land-use conversion to other lands including croplands. Though there were indications that land management practices such as tillage in croplands and grazing in grasslands, land-use changes, and land disturbance including forest fire might also affect both δ¹³C and δ¹⁵N, more data need to be accumulated to find a general trend of the isotopic variations of SOM. Analysis of both δ¹³C and δ¹⁵N may enlarge understanding of changes in SOM sources and soil C and N cycling by land-use types, management, change, and disturbance.
... The soil C/N ratio can represent the decomposition rate of organic N and microorganisms; the higher soil C/N ratio, the lower the decomposition rate of organic N; and the opposite is true for microorganisms [15]. In addition, it was found that microbes can optimize their resource utilization strategy according to litter quality, nutrient utilization efficiency, and restriction status, thus affecting the δ 13 C and the δ 15 N composition [16]. In conclusion, soil stoichiometry and microorganisms are tightly connected to δ 13 C and δ 15 N. Yet, the variation of forest δ 13 C and δ 15 N with plantation age and the mechanism of soil stoichiometry driving C and N isotope fractionation are still uncertain and need to be further studied. ...
Understanding the relationships between carbon; nitrogen, their stable isotopes δ13C and δ15N, and soil stoichiometry may further our understanding of the regulatory mechanisms of the soil quality index on the equilibrium on isotopic fractionation. Four plantations of Zanthoxylum planispinum var. dintanensis (5–7, 10–12, 20–22 and 30–32 years) in the karst plateau gorge area, Guizhou Province, China, were selected to determine the variation characteristics and interactions between leaves, leaf litter, soil carbon (C), soil nitrogen (N) and their isotopes with plantation age, and to explore the relationship between soil stoichiometry and the isotopes δ13C and δ15N. The results were as follows: (1) the δ13C in leaves, litter, and soil were −28.04‰ ± 0.59‰, −26.85‰ ± 0.67‰, and −19.39‰ ± 1.37‰, respectively. The contents of δ15N were 2.01‰ ± 0.99‰, 2.91‰ ± 1.32‰, and 3.29‰ ± 0.69‰, respectively. The contents of δ13C and δ15N were ranked in the order, soil > litter > leaf. (2) With increasing plantation age, the soil 13C decreased; the leaf and the litter δ15N increased first then decreased, and the litter δ13C and the soil δ15N did not vary significantly. (3) The litter layer was positively correlated with soil δ13C and negatively correlated to δ15N. (4) Redundancy analysis showed that the soil microbial biomass carbon (MBC) and the bacteria/fungi (BAC/FUN) were the dominant factors affecting the natural abundance of C and N isotopes
... The proximity between sampling plots minimizes the influence of factors such as parent material, soil texture, climate and geomorphology. Therefore, the variations in the chemical characteristics among the organic horizons are mainly attributed to species-specific effects, as evidenced in previous studies (Vesterdal et al., 2013;Augusto et al., 2015;Cremer et al., 2016;Lorenz et al., 2020). ...
... The C/N ratio of the organic horizons studied in Serra da Nogueira was within the range (16-44) reported in European forests (Cools et al., 2014). Higher values of the C/N ratio in the organic horizons of coniferous plots (PN and PM) (Table 1), were in agreement with a lower degree of organic matter decomposition (Díaz-Pinés et al., 2011;Augusto et al., 2015;Lorenz et al., 2020;Güner et al., 2021). On the contrary, the higher content of total N in the organic horizons under the native species (QP) could be justified by a faster organic matter decomposition, resulting in a lower C/N ratio (Vesterdal et al., 2012). ...
... Regarding the type of organic subhorizon, the progressive reduction of the C/N ratio from the OL to the OH (Table 1) was in agreement with the more fresh material and lignin-rich biomass in the former (Cools et al., 2014;López-Marcos et al., 2018). Total organic C and total N in the organic subhorizons sometimes peak in the OF layers departing from the sequence OL > OF > OH often reported in the literature (Herrero et al., 2016;Lorenz et al., 2020). However, highest values of total N in the OF layer of forest soils dominated by coniferous or deciduous species have already been observed in other studies, varying between 12 and 25 g kg −1 and being similar to ours (Hilli et al., 2008;Trum et al., 2011). ...
Forest areas are a primary sink of atmospheric mercury (Hg) within terrestrial ecosystems, whereas forest vegetation plays a key role in atmospheric Hg transfer to soil horizons. This study assessed variations in total Hg contents (HgT) and accumulation (HgRes) in the soil organic horizons of a forest area in NE Portugal, where post-wildfire afforestation led to the substitution of the native deciduous species (Quercus pyrenaica) by fast-growing coniferous species (Pseudotsuga menziesii and Pinus nigra). The study also evaluated, for each species, the links between Hg contents and other biophilic elements of soil organic matter (C, N, S) present in organic subhorizons (OL, OF, OH). Mean HgT in the organic horizons of the different tree species follow the sequence: P. nigra (88 μg kg⁻¹) < Q.pyrenaica (101 μg kg⁻¹) < P. menziesii (141 μg kg⁻¹). The highest HgRes for the entire organic horizon was found under P. menziessi (471 μg m⁻²), followed by P. nigra (253 μg m⁻²) and Q. pyrenaica (189 μg m⁻²). Among the organic subhorizons, values of HgT and HgRes follow the sequence OL < OF < OH, which is consistent with the degree of organic matter humification. Indeed, HgT and HgRes correlated significantly with the C/N and C/S ratios for all species and organic subhorizons, suggesting that the quality of organic matter may influence strongly the Hg fate in these forest soils. Soils from P. menziesii plots have shown an HgRes 2.5 times higher than in plots dominated by the native Q. pyrenaica. Hg accumulation in the organic horizons, promoted in the coniferous species, may increase the risk of Hg mobilization due to wildfires and forest management practices. Therefore, forest management plans should select cautiously the tree species for afforestation in order to minimize adverse environmental effects caused by changes in the biogeochemical cycle of contaminants such as Hg.
