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Tree species affect soil organic matter stocks and stoichiometry in interaction with soil microbiota
Abstract
The purpose of this research was to evaluate tree species effects on quantitative and qualitative soil organic matter (SOM) properties of forest floors and mineral soil layers. Additionally, the contribution of soil microbial biomass to SOM was studied in five forest stands with different dominant tree species.
The study was conducted at the afforested spoil heap ‘Sophienhöhe’ located at the lignite open-cast mine Hambach near Jülich, Germany. The 35 year-old afforested sites consisted of monocultural stands of Douglas fir (Pseudotsuga mienziesii), pine (Pinus nigra), beech (Fagus sylvatica) and red oak (Quercus rubra) as well as a mixed deciduous stand site planted mainly with hornbeam (Carpinus betulus), lime (Tilia cordata) and common oak (Quercus robur). There, boundary conditions regarding soil, climate, topography and management were highly similar, equivalent to a common garden experiment but on landscape level. Because the parent material used for site recultivation was free from organic matter or coal material, the SOM accumulation is a result of in situ soil development.
Tree species had a significant effect on soil organic carbon (SOC) stocks, stoichiometric patterns of C, hydrogen (H), nitrogen (N), oxygen (O) and sulfur (S) and the microbial biomass carbon (MBC) content in the forest floor and the top mineral soil layers (0–5 cm, 5–10 cm, 10–30 cm). In general, forest floor SOC stocks were significantly higher in coniferous forest stands compared to deciduous tree species. Differences in SOM quantity became less pronounced with increasing depth, while stoichiometric molar ratios of SOM as indices of litter turnover and SOM composition differed also in deeper layers. Differences in H:C and O:C ratios among tree species clearly increased along the depth gradient in mineral soils, indicating that SOM turnover by oxidative processes depends on tree species. Differences in depth gradients of the microbial quotient (MBC to SOC ratio) among tree species emphasized differences in the microbial C turnover. Furthermore, the relationship between the microbial quotient and SOM stoichiometry (C:N and C:S ratio) became stronger with increasing soil depth. This suggests that N and especially S limitation determined the microbial turnover of SOM in deeper mineral soil layers.
... Additionally, the different litter quality in coniferous and broadleaf plantations serves as a likely explanation for the different responses of microbial C to forest conversions (Figure 4a). Broadleaf litter tends to have higher N and lower lignin content than coniferous litter (Lorenz & Thiele-Bruhn, 2019). The high-quality broadleaf litter decomposes more easily and could foster more microbial biomass than low-quality needles. ...
... Changes in soil C:N and total N closely tracked changes in bacterial richness (Figure 5c), while the RR of soil C:N negatively correlated with the RR of bacterial richness (Figure 6e). Plantations types indirectly affect soil C:N, which varies because the litter from different plantation tree species is of differential quality (Lorenz & Thiele-Bruhn, 2019). High-quality (low C:N) litter is more easily decomposed by microbes than lowquality litter, and therefore stimulates the growth of copiotrophic r-strategists (Zhou et al., 2020) and bacterial dominance. ...
... High-quality (low C:N) litter is more easily decomposed by microbes than lowquality litter, and therefore stimulates the growth of copiotrophic r-strategists (Zhou et al., 2020) and bacterial dominance. Broadleaf litter generally has a higher N content than conifer litter (Lorenz & Thiele-Bruhn, 2019;Wan et al., 2014). Similarly, AM-associated trees tend to produce high quality litter that degrades more rapidly, which leads to lower soil C:N relative to their EcM counterparts (Phillips et al., 2013). ...
Primary or secondary forests around the world are increasingly being converted into plantations. Soil microorganisms are critical for all biogeochemical processes in ecosystems, but the effects of forest conversion on microbial communities and their functioning remain unclear. Here, we conducted a meta‐analysis to quantify the impacts that converting forests to plantations has on soil microbial communities and functioning as well as on the associated plant and soil properties. We collected 524 paired observations from 138 studies globally. We found that conversion leads to broad range of adverse impacts on soils and microorganisms, including on soil organic carbon (−24%), total nitrogen (−29%), bacterial and fungal biomass (−36% and −42%, respectively), microbial biomass carbon (MBC, −31%) and nitrogen (−33%), and fungi to bacteria ratio (F:B, −16%). In addition, we found impacts on the ratio of MBC to soil organic C (qMBC, −20%), microbial respiration (−18%), N mineralization (−18%), and enzyme activities including β‐1,4‐glucosidase (−54%), β‐1,4‐N‐acetylglucosaminidase (−39%), and acid phosphatase (ACP; −34%). In contrast, conversion to plantations increases bacterial richness (+21%) and microbial metabolic quotient (qCO2, +21%). The effects of forest conversion were consistent across stand ages, stand types, and climate zone. Soil C and N contents as well as the C:N ratio were the main factors responsible for the changes of microbial C, F:B, and bacterial richness. The responses of qCO2, N mineralization, and ACP activity were mainly driven by the reductions in F:B, MBC, and soil C:N. Applying macro‐ecology theory on ecosystem disturbance in soil microbial ecology, we show that microbial groups shifted from K to r strategists after conversion to plantations. Our meta‐analysis underlines the adverse effects of natural forests conversion to plantations on soil microbial communities and functioning, and suggests that the preservation of soil functions should be a consideration in forest management practices. Conversion of primary or secondary forests to plantations is constantly increasing worldwide. This study conducted a meta‐analysis to quantify the impacts that converting forests to plantations has on soil and microbial properties and functions. We found that forest conversion significantly decreased soil organic C and N contents, microbial biomass, fungi to bacteria ratio, microbial respiration, and N mineralization, but increased bacterial richness and microbial metabolic quotient. Microbial groups were found shifted from K‐strategist dominated to r‐strategist dominated after conversion to plantations. We therefore suggest that the preservation of soil functions should be a consideration in forest management practices.
... Eilers et al., 2012;Šnajdr et al., 2013;Scheibe et al., 2015;Józefowska et al., 2017). Even more, also tree species effects on MBC (Ribbons et al., 2016;Lorenz and Thiele-Bruhn, 2019) and the microbial C:N:P stoichiometry (Zederer et al., 2017) vary with soil depth. Yang and Zhu (2015) found indications that tree species affect the amounts of soluble organic compounds in the SMB such as amino acids, reducing sugars and phenolic compounds. ...
... To do so, this research was conducted at a post-mining site that was investigated in previous studies to elucidate tree species effects on SOM and related microbial properties (Lorenz and Thiele-Bruhn, 2019;Lorenz et al., 2020). We studied monocultural stands of European beech (Fagus sylvatica), Douglas fir (Pseudotsuga menziesii) and black pine (Pinus nigra) that were grown for 35 years under identical soil and geomorphological conditions to assess their impact on soil microbial properties in different soil depths. ...
... The thickness of the Ah horizon was significantly lower under pine (2.4 ± 0.8 cm) compared to beech (4.2 ± 0.7 cm) and Douglas fir (5.0 ± 1.4 cm). Additionally, initial podsolization characterized the transition zone from the forest floor to the mineral soil layer under pine compared to the other forest stands (Lorenz and Thiele-Bruhn, 2019). Organic layers under all tree species were classified as Moder (Zanella et al., 2018). ...
Recent findings on soil organic matter (SOM) revealed that soil microorganisms are not only crucial for SOM formation through plant litter degradation but soil microbial biomass (SMB) may also directly contribute to SOM and its composition. However, the role and interactions of litter quality, microbial turnover and composition of SMB and SOM remain unclear. Hence, soil profiles (organic forest floor and mineral soil layers) at a recultivated and afforested post-mining site were investigated for the influence of litter quality from different tree species (Fagus sylvatica, Pseudotsuga menziesii, Pinus nigra) and soil depth – representing different degrees of organic matter (OM) turnover – on the molecular composition of chloroform fumigation extracted SMB-derived compounds in comparison with easily extractable (non-fumigated) SOM-derived compounds. The SMB extracts were analyzed for microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP). The molecular composition of SMB and SOM compounds were determined by electrospray ionization Fourier transformation ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) complemented by the determination of nine monosaccharides representing microbial or plant origin.
Van Krevelen diagrams obtained from the ESI-FT-ICR mass spectra revealed the substantial contribution of microbial-derived compounds to extractable SOM that further increased with soil depth. Analysis of the easily extractable monosaccharides implied that >99% were of microbial origin. Microbial sugars as well as MBC, MBN and MBP explained best depth-related variations of extractable SMB compounds indicating that supply and availability of C-rich OM drive these parameters. Furthermore, the contribution of microbial sugar C to MBC increased with depth, suggesting that recycling of carbohydrates is an adaptation strategy of microorganisms in C-limited environments. The supply of tree species-specific substrates resulted in different chemical composition of SMB with largest differences between deciduous and coniferous stands and vice versa, microorganisms contributed to SOM resulting in large similarity in the composition of extractable SOM and SMB.
... The total amount of C that is stored in the forest floor and mineral soil is affected by the dominating tree species (Mueller et al. 2015). Furthermore, stoichiometric ratios like the carbon:nitrogen (C:N) ratio of soil organic matter (SOM) are influenced by the forest stand (Cools et al. 2014;Lorenz and Thiele-Bruhn 2019). Ecological stoichiometry using elemental ratios is a suitable tool to assess SOM and its turnover (Manzoni et al. 2010;Zechmeister-Boltenstern et al. 2015). ...
... Due to this, further research is required to clarify if d 13 C and d 15 N, and thus the SOM status in organic forest floor horizons (litter-OL, fragmented-OF, humified-OH) and mineral soil differs between tree species. This research was conducted on a post-mining site, where previous accumulation of plant or coal material are negligible (Lorenz & Thiele-Bruhn 2019). We studied monocultural stands of Douglas fir (Pseudotsuga menziesii), black pine (Pinus nigra), European beech (Fagus sylvatica) and red oak (Quercus rubra) that were grown for 35 years under identical soil and geomorphological conditions to assess tree species effects on the SOM status. ...
... There, boundary conditions regarding soil, climate, topography and management were highly similar, equivalent to a common garden experiment. The Regosols at the investigated sites developed on the same sandy gravelly parent material (Lorenz and Thiele-Bruhn 2019). The carbonate-free parent material that was used for the spoil heap recultivation had a C content of 0.20 ± 0.05% and a C/N molar ratio of 7.5 ± 1.2 (Table S1). ...
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 menziesii), black pine (Pinus nigra), European beech (Fagus sylvatica) and red oak (Quercus rubra) growing on a uniform post-mining soil. We investigated the natural abundance of 13C and 15N and the carbon:nitrogen (C:N) and oxygen:carbon (O:C) stoichiometry of litterfall and fine roots as well as SOM in the forest floor and mineral soil. Tree species had a significant effect on SOM d13C and d15N reflecting significantly different signatures of litterfall and root inputs. Throughout the soil profile, d13C and d15N were significantly related to the C:N and O:C ratio which indicates that isotope enrichment with soil depth is linked to the turnover of organic matter (OM). Significantly higher turnover of OM in soils under deciduous tree species depended to 46% on the quality of litterfall and root inputs (N content, C:N, O:C ratio), and the initial isotopic signatures of litterfall. Hence, SOM composition and turnover also depends on additional-presumably microbial driven-factors. The enrichment of 15N with soil depth was generally linked to 13C. In soils under pine, however, with limited N and C availability, the enrichment of 15N was decoupled from 13C. This suggests that transformation pathways depend on litter quality of tree species.
... A major reason for this is the inherent difference in foliar traits, whereby conifer needles have a lower specific surface area, are richer in lignin and phenolic compounds, and are more acidic than deciduous leaves. This results in lower rates of litter decomposition and the accumulation of deeper organic forest floors under coniferous forest canopies (Laganière et al., 2013;Lorenz and Thiele-Bruhn, 2019;Marty et al., 2015a). On the other hand, several studies reported that SOC stocks in the underlying mineral soil horizons are equal to, or higher, in deciduous than coniferous forest stands (Boča and van Miegroet, 2017;Lorenz and Thiele-Bruhn, 2019;Marty et al., 2015a;Tremblay et al., 2002;Woldeselassie et al., 2012;Wotherspoon et al., 2014). ...
... This results in lower rates of litter decomposition and the accumulation of deeper organic forest floors under coniferous forest canopies (Laganière et al., 2013;Lorenz and Thiele-Bruhn, 2019;Marty et al., 2015a). On the other hand, several studies reported that SOC stocks in the underlying mineral soil horizons are equal to, or higher, in deciduous than coniferous forest stands (Boča and van Miegroet, 2017;Lorenz and Thiele-Bruhn, 2019;Marty et al., 2015a;Tremblay et al., 2002;Woldeselassie et al., 2012;Wotherspoon et al., 2014). Furthermore, deep organic forest floors, as found under conifer canopies, are more vulnerable to disturbances such as wildfire than SOC residing in the mineral soil (Benjamin et al., 2020;De Bano, 1991). ...
... 2). Our result is considerably lower than the recordings of Maharaj et al. 24 79 . These differences in SOC stocks are attributed to multi-level interactions between a number of in uence factors, including (i) the quantity of organic matter input via plant litter, (ii) the chemical composition of the above-and belowground litter, and (iii) resulting bioturbation and turnover processes facilitated by the soil (micro)biome 120 . ...
... e. levels that are natural and/or achievable at the site in question). A very important factor, especially in coniferous forests, is the contribution of forest oors to SOC stock change 79,127,128 . Bradford and Kastendick 127 found the C content in forest oor material to increase linearly with stand age in pine forests in the Northern USA. ...
Opencast coal mining results in high loss of soil organic carbon (SOC), which may be restored via recultivation. Common methods include liming, topsoil application, and phytoremediation. It remains unclear, however, which parameters determine the effectiveness of varying recultivation strategies especially regarding SOC sequestration. We, therefore, analysed the relationship between SOC stock changes in abandoned coal mines and the recultivation method, soil properties (pH, texture, depth), climate, and time under recultivation in 51 studies (404 data entries). All included climatic regions recorded increases in SOC stocks, with tropical soils showing the highest potential for relative gains of up to 468%. With respect to soil texture, clay content is the main factor promoting SOC sequestration. Strategy-wise, the largest positive effect was achieved by forest with liming (1.5 Mg ha − 1 a − 1 ), fallow after topsoil and fertiliser addition (1.1 Mg ha − 1 a − 1 ), agriculture after topsoil addition (1.0 Mg ha − 1 a − 1 ), and forest with fertiliser (1.0 Mg ha − 1 a − 1 ) with a response ratio of 35%, 58%, 140%, and 48%, respectively. Soil depths < 10 cm, < 20 cm, and 21–40 cm stored more SOC (0.6 Mg ha − 1 a − 1 , 1.0 Mg ha − 1 a − 1 , and 0.4 Mg ha − 1 a − 1 ; response ratio of 123%, 68%, and 73%, respectively) than soils at a depth of 41–80 cm (0.1 Mg ha − 1 a − 1 ; response ratio of 6%). In terms of pH, strongly acidic soils (pH < 4.5) and alkaline conditions (pH > 7) offered the most beneficial environment for SOC sequestration at 0.4 Mg ha − 1 a − 1 and 0.8 Mg ha − 1 a − 1 , respectively (44% and 67% response).
... L'horizon organique des peuplements de conifères est plus épais que celui des peuplements de feuillus en raison d'une plus forte accumulation de litière causée par un fort ratio lignine/azote qui ralentit fortement sa décomposition (Bārdule et al., 2021;Berg & Meentemeyer, 2002;Hobbie et al., 2006;Jacob et al., 2010). Cela conduit à une plus faible teneur en MO pour les feuillus que pour les conifères (Augusto et al., 2015;Lorenz & Thiele-Bruhn, 2019;Schulp et al., 2008). Cependant cette tendance globale n'est pas forcément vraie pour tous les peuplements comme le montre Schulp et al. (2008) avec une teneur en MO plus forte et un horizon organique en pinèdes, certes plus épais qu'en hêtraies, mais équivalents à ceux des chênaies. ...
... Ces résultats sont en accord avec l'étude de Schulp et al. (2008) qui trouve la même différence de teneur en MO des hêtraies par rapport aux pinèdes et chênaies. En revanche, d'autres études ont montré une plus forte teneur en MO des peuplements de conifères par rapport aux peuplements de feuillus (Augusto et al., 2002;Cremer et al., 2016;Lorenz & Thiele-Bruhn, 2019;Vesterdal & Raulund-Rasmussen, 1998). La différence de teneur en MO entre les deux peuplements de feuillus est généralement expliquée par une influence sur le pH du sol avec une plus grande acidité de la litière et de la matière organique sous peuplement de chêne et à une plus forte immobilisation des cations dans la biomasse (Nordén, 1994 (Bergkvist & Folkeson, 1995;Oostra et al., 2006), ce qui n'est pas le cas pour notre étude. ...
Le méthane est l’un des principaux gaz à effet de serre contribuant au réchauffement climatique. Son oxydation par les organismes méthanotrophes des sols forestiers superficiels constitue un service écosystémique majeur mais souvent négligé. L’objectif de mes travaux de thèse était de déterminer les principaux facteurs responsables des variations spatiales de l’oxydation du méthane des sols de forêts à l’échelle du massif forestier. J’ai pu montrer que le contenu en eau du sol apparait comme le principal facteur expliquant les variations spatiales au printemps et les variations saisonnières de l'oxydation du CH4 dans les cinq premiers centimètres du sol. L’oxydation du méthane est optimale pour un faible contenu en eau et une forte porosité en air mais peut être fortement impactée par des conditions climatiques extrêmes. En cas de forte sécheresse ou d’inondation importante, dont la fréquence et l’intensité seront croissantes dans le futur avec le changement climatique, le puits de méthane des sols pourrait être fortement diminué. L’essentiel de l’oxydation du méthane ne se produit pas toujours dans les 5 premiers centimètres du sol et la profondeur à laquelle l’oxydation du méthane est la plus forte varie selon le type de peuplement. Cette structuration verticale de l’oxydation du méthane s’explique par l’effet combiné d’une baisse de la teneur en matière organique avec la profondeur et de l’épuisement du méthane disponible pour les méthanotrophes par l’oxydation réalisée dans les couches supérieures. Néanmoins, la distribution verticale de l’abondance des méthanotrophes ne reflétait pas celle de l’oxydation du méthane, ce qui suggère que cette dernière présente très probablement une forte dynamique saisonnière.
... Over time, forest species should start to appear in the understorey, but the problem is with the quality of the diaspore source. The area is mainly characterized by species-poor, unnatural spruce stands, but even these types of habitats can contribute to carbon sequestration, albeit with a different distribution within the ecosystem compared to natural forests [60,61]. There were no significant differences in species differentiation by life form, which is not consistent with Piekarska-Stachowiak et al. [61,62]. ...
... The area is mainly characterized by species-poor, unnatural spruce stands, but even these types of habitats can contribute to carbon sequestration, albeit with a different distribution within the ecosystem compared to natural forests [60,61]. There were no significant differences in species differentiation by life form, which is not consistent with Piekarska-Stachowiak et al. [61,62]. The different results may be explained by different geographical conditions (temperature, altitude), as these factors are often the main drivers of the community [62,63]. ...
The relationship between vegetation and selected soil characteristics in different monoculture forest types was investigated as part of a landscape restoration project after brown coal mining. Six forest types were selected: alder (Alnus sp.), spruce (Picea sp.), pine (Pinus sp.), larch (Larix sp.), long-term deciduous forest (Quercus robur, Tilia sp.), and forest created by spontaneous succession. These stands were classified into two age categories (younger and older). The soil attributes, C/N, TC, TN, pH, and A horizon depth were assessed. The observed species were categorized into functional groups by life history, life forms according to Raunkiær, and affinity to the forest environment. C/N ratio, humus thickness, and canopy cover were the main soil parameters affecting plant communities. The highest C/N values were recorded in Pinus and Larix stands, which were significantly different from deciduous and succession stands. The highest diversity index was noted in younger stands of Alnus and the lowest in younger stands of Picea. Intermediate values of the diversity index were achieved in successional stands at both age levels and in Larix and Alnus stands. The species belonging to a functional group was not an important factor in these habitat types. The species composition and vegetation change over time in the Alnus, long-life deciduous, and Larix stands show that these species are more suitable for forestry reclamation than spruce or pine. The study also emphasizes the great value of spontaneous succession areas as full-fledged alternatives to forestry reclamation.
... The biogeochemical cycles of C, N and P and their stoichiometric characteristics are affected by various biotic and abiotic factors (Chaopricha and Marín-Spiotta 2014;Lai et al. 2016;Liu et al. 2020), such as land use change (Deng et al. 2014), vegetation type (Liang et al. 2017;Lorenz and Thiele-Bruhn 2019) and climatic zones . The contents of SOC, TN and labile organic carbon (LOC) fractions (including dissolved organic carbon (DOC), microbial biomass carbon (MBC) and readily oxidised organic carbon (ROOC)) were significantly increased after vegetation restoration (Benbi et al. 2015;Lai et al. 2016;Li et al. 2016;Gao et al. 2018;Zhang et al. 2020a), and the available N, P and K contents were increased for 38 years after vegetation restoration in Horqin Sandy Land (Li et al. 2013. ...
... Our results showed that TN, AK, AP, NO 3 − -N, EC and pH have a substantial spatial heterogeneity, which supports the fertility island theory (Tables 3 and 4) and was found to be similar to the results of Li et al. (2007) and Hu et al. (2018). This finding could be due to the litter and roots of A. ordosica mainly being distributed on the surface (0-20 cm) layer, which increases soil organic matter and root exudate input as well as increases mineral nutrients from their decomposition (Lorenz and Thiele-Bruhn 2019;Zhang et al. 2020b). Therefore, organic acids and amino acids originated from organic matter decomposition, and root exudates decreased pH and increased EC and AP of the topsoil (Hong et al. 2018). ...
PurposeVegetation restoration is an effective measure for improving the function of soil ecosystems and promoting the biogeochemical cycling of carbon (C), total nitrogen (TN) and total phosphorus (TP). Here, we aimed to quantify the fine-scale (pedon scale) spatial distribution of soil C, N, P and soil physical–chemical properties in the Mu Us Desert ecosystems.Methods
We systematically evaluated the effects of A. ordosica on fine-scale (pedon scale) spatial distribution of C, TN, TP, soil-available nutrients, and liable organic carbon (LOC) and their stoichiometric characteristics in the semiarid Mu Us Desert in the 0–100-cm soil profiles at various distances from the plant.Results and discussionThe results demonstrated that soil organic carbon (SOC), TN and LOC were decreased with increasing distance from the plant and soil depth. SOC stocks at 20 cm were 16.98% higher than those at 120 cm from the plant. SOC stocks at 20, 60 and 120 cm from the plant were increased by 71.62%, 58.14% and 46.72% compared with shifting sandy land (Sland), respectively. Microbial biomass carbon (MBC) and readily oxidised organic carbon (ROOC) were significantly affected by different soil layers and distances and their interaction (p < 0.05), whereas dissolved organic carbon (DOC) was affected by the soil layers. TN and soil-available nutrients in the surface layer and at closer distances to the plant were higher than those in the sublayer and Sland. The ratio of C:N:P was generally decreased with different distances from the plant and different soil layers. The ratios of soil C:N, C:P and N:P were significantly different at different soil layers, whereas the ratios of soil C:P and N:P were significantly different at different distances from the plant (p < 0.05). Soil C:P ratio was positively correlated with soil C:N and N:P ratios (p < 0.001). N and P contents in leaves were higher than those in roots, branches and litter, but C contents in leaves were lower than those in other plant tissues and litter (p < 0.01). N:P ratio in leaves (13.94) showed that there was a shortage of N and P in the Mu Us Desert ecosystems.Conclusions
We concluded that A. ordosica could enhance the accumulation of SOC, LOC and N on a fine scale and improve mineral-nutrient availability in semiarid deserts and, as a result, the function of soil ecosystems could be improved. Moreover, the limitation of N and P can be alleviated by adding additional N and P.
... e. levels that are natural and/or achievable at the site in question). A very important factor, especially in coniferous forests, is the contribution of forest floors to SOC stock change [82][83][84] . Bradford and Kastendick 82 found the C content in forest floor material to increase linearly with stand age in pine forests in the Northern USA. ...
Abstract Opencast coal mining results in high loss of soil organic carbon (SOC), which may be restored via recultivation. Common strategies include liming, topsoil application, and phytoremediation. It remains unclear, however, which parameters determine the effectiveness of these varying recultivation strategies especially regarding SOC sequestration. This meta-analysis analyses the effect of varying recultivation strategies on SOC sequestration under different climate and soil conditions (pH, texture, depth) as well as in relation to time, based on 404 data entries from 51 studies. All included climatic regions recorded increases in SOC stocks, with tropical soils showing the highest potential for relative gains at up to 637%. We demonstrate that loamy soils sequester twice as much newly introduced SOC than sand. Strategy-wise, the highest mean rate of SOC sequestration is achieved by forest after topsoil application (3.9 Mg ha−1 a−1), agriculture after topsoil application (2.3 Mg ha−1 a−1), and agriculture with topsoil and fertiliser application (1.9 Mg ha−1 a−1) with a response ratio of 304%, 281%, and 218%, respectively. Soils analysed to less then 40 cm depth show higher SOC sequestration rates (
... In the current study, there were significant differences in TN, pH and EC between S. psammophila and P. sylvestris because differences in root and surface litter input from different plants changed the TN and pH in the surface soil (0-10 cm) and subsurface layer (10-20 cm) on a fine-scale level. Therefore, there was higher TN and lower pH in the surface soil and at closer distances from the plant, consistent with the results of previous studies (Lorenz and Thiele-Bruhn 2019;Zhang et al. 2020b). For TN of S. psammophila and P. sylvestris, there was a significant difference among different distances, mainly depending on the input and output of nitrogen from root and litter and their distribution, as well as the difference in N At a distance of 20 cm, soil TN of P. sylvestris was significantly higher than that of S. psammophila, mainly due to the fact that the <80 cm distances from P. sylvestris distributed more C silt in 10-60 cm soil layers ( Supplementary Fig. S2d, Yao et al. 2019) and increased SOC accumulation and deposition (Fig. 3e). ...
Afforestation is helpful to improve soil functions and increase soil organic carbon (SOC) sequestration in semiarid deserts. However, the fine-scale (around a single plant) spatial distribution of SOC and its liable organic carbon (LOC) fractions after afforestation in semiarid deserts are poorly understood. Pinus sylvestris and Salix psammophila afforested on shifting sandy land (Sland) were selected to quantify fine-scale (at 20, 80, 150 and 240 cm away from the trees) spatial distribution of SOC and its LOC fractions in the southeast edge of Mu Us Desert, China. The results showed that the afforested S. psammophila and P. sylvestris significantly increased SOC, total nitrogen, dissolved organic carbon, microbial biomass carbon and readily oxidized organic carbon (ROOC). At 20 cm distance, SOC storage of P. sylvestris was 27.21% higher than S. psammophila in 0–100 cm soil layers, and SOC storage of S. psammophila at 80 and 150 cm distances was 5.50% and 5.66% higher than P. sylvestris, respectively. Compared with Sland, SOC storage under S. psammophila and P. sylvestris significantly increased by 94.90%, 39.50%, 27.10% and 18.50% at 20, 80, 150 and 240 cm distance, respectively. ROOC accounted for 14.09% and 18.93% of SOC under S. psammophila and P. sylvestris, respectively. Our results suggest that afforestation can promote SOC accumulation at different distances from the plants, and that P. sylvestris allocates more organic matter to the closer soil compared with S. psammophila (<80 cm from the tree).
... First, the conversion from natural forests to monoculture plantations reduces native plant diversity and soil C and N content because of the reduction in litter input (Guillaume et al., 2018). Second, broadleaved litter has a higher N and lower lignin than coniferous litter (Lorenz and Thiele-Bruhn, 2019), which makes it easier for litter to decompose and foster more microbial biomass . ...
Considerable natural or secondary forests have been converted to plantations in response to the growing needs for timber, paper, and fuel. Soil fungal communities are sensitive to ecosystem transformation and play an important role in aboveground-belowground linkages and biogeochemical cycling. However, the effect of forest conversion on fungal community structure and functions and driving mechanisms remains unclear. We investigated the response of soil fungal communities and the corresponding change in soil physicochemical biological properties and enzymatic activities to the natural broad-leaved forest (NBF) converted to the Chinese fir (Cunninghamia lanceolata) plantation (CFP) in subtropical China with ITS rRNA amplicon sequencing. Soil physicochemical properties, microbial biomass, fungal alpha diversities, and enzymatic activities decreased with forest conversion, including pH, soil water content, soil organic carbon, available phosphorus, total nitrogen, nitrate nitrogen, microbial biomass carbon and nitrogen, urease, protease, and acid phosphatase. Fungal community composition and structure were also strongly affected by forest conversion. Ascomycota had a higher read abundance in the NBF, but Basidiomycota showed a higher read abundance in the CFP. The read abundance of saprotroph and arbuscular mycorrhizal fungi increased with forest conversion, while that of ectomycorrhizal fungi decreased. Some fungal guilds—dung saprotrophs, lichenized fungi, endophytes, and lichen parasites—were even nearly lost in the CFP. These changes in fungal communities are all closely correlated to soil physicochemical properties, microbial biomass, and enzymatic activities. Overall, our study emphasizes the negative effect of the NBF conversion to the CFP on C, N, and P cycling mediated by fungi—and recommends replacing monoculture coniferous forests with mixed forests in reforestation to improve soil degradation.
... Considering the similar soil substrate, soil texture, climate, stand age and forest management, the differences in soil properties are assumed to be primarily caused by the influence of tree species. This experimental design is comparable to a common garden experiment in spite of the limited number of replicates per tree species (Lin et al. 2018;Lorenz and Thiele-Bruhn 2019). ...
Tropical forests are among the most productive and vulnerable ecosystems in the planet. Several global forestation programs are aiming to plant millions of trees in tropical regions in the future decade. Mycorrhizal associations are known to largely influence forest soil carbon (C) stocks. However, to date, little is known on whether and how different tree mycorrhizal types affect soil respiration (Rs) and C stocks in tropical forests. In this study, we used a three-decade tropical common garden experiment, with three arbuscular mycorrhizal (AM) and three ectomycorrhizal (EM) monocultures, to investigate the impacts of tree mycorrhizal type on Rs and soil C stocks. Associating biotic (e.g. root biomass, litter dynamic, soil microbes) and abiotic factors (e.g. microclimate) were also measured. Our results showed that AM stands supported significantly higher Rs and soil C stock, litter turnover rate, and fine root biomass than EM stands. Further statistical analysis displayed that tree mycorrhizal type was the most important factor in regulating Rs and soil C stock compared with other biotic or abiotic factors. Moreover, we found that mycorrhizal type directly and indirectly affected Rs and soil C stocks via fine root biomass and litter dynamic (i.e. litter production, litter standing crop, and litter turnover rate). Our findings highlight important effects of tree mycorrhizal type on forest C cycle, suggesting that planting AM tree species could contribute to promote soil C stock in tropical ecosystems.
... Forest type is a determinant of SOC storage as it affects both input and decomposition of C (Wiesmeier et al., 2019). The SOC stocks have been reported to vary with differences in the dominant tree species composition in other studies as well: Kooch et al. (2016), Liu et al. (2016a) and Lorenz and Thiele-Bruhn (2019). In tropical forest ecosystems, forest type can alter the SOC stocks through the interacting effects of several factors e.g., climate, topography, structure, temperature, precipitation, forest type, moisture content, SOM, seasonal rainfall, etc. (García-Oliva et al., 2003;Liu et al., 2016b;Pulla et al., 2016;Gebeyehu et al., 2019;Mayer et al., 2020;Yuan et al., 2021;Zhang et al., 2021). ...
Assessment of soil organic carbon (SOC) dynamics in tropical dry deciduous forests is imperative to know their contribution in regulating the regional and global carbon (C) cycles. In the present study, three forest types: dry deciduous teak (DDTF), dry deciduous mixed (DDMF) and Boswellia (BF) forests were selected to assess the variation in SOC and the factors influencing it. The SOC stocks (0-50 cm) varied significantly within and among the forest types and ranged from 48.7 (BF) to 89.1 (DDTF) Mg C/ha (mean: 64.6 ± 9.7 Mg C/ha). The differences observed could be due to variations in organic matter input, quality and quantity of litter produced, topography, vegetation composition, soil bulk density, soil moisture and soil depth. The total mean SOC stocks at 0-10, 10.1-30 and 30.1-50 cm depths were 19.2, 24.4 and 21.0 Mg C/ha, respectively. The SOC showed significant positive relationships with soil organic matter (r = 0.79, P < 0.01), soil moisture (r = 0.41, P < 0.01), aspect (r = 0.52, P < 0.01) and dominance (r = 0.53, P < 0.01), which accounted for 66.8, 15.7, 8.4 and 5.6% of variance. This study provided an understanding of the SOC stock variation among three tropical dry deciduous forest types in the Central Indian landscape and identified the roles of different drivers in SOC storage.
... Soil microorganisms constitute the main biomass pool in the soil ecosystem. Mounting studies have found that soil microorganisms are affected by soil environments (Almario et al., 2017;Dilly, 1999;Fierer and Jackson, 2006;Lennon et al., 2012;Lorenz and Thiele-Bruhn, 2019). They link the soil environments to the ecosystem functioning and provide ecosystem service benefits for plant production (van der Voort et al., 2016). ...
Revealing soil microbial community assembly and associated influencing factors is essential for understanding the diversity and functioning of terrestrial ecosystems. Yet how soil microbial communities respond to environmental factors and plant traits in natural shrub ecosystems has received little attention. Therefore, we explored the diversity and assembly mechanisms of soil bacterial and fungal communities across four ecoregions of natural shrubland in Shaanxi Province, northeastern China. Soil chemical properties, climatic variable, and plant growth traits of dominant shrub species were analyzed to determine their relationships with local soil microbial communities. The results indicated that soil bacteria and fungi in the four ecoregions had divergent diversity patterns. The microbial community composition was significantly affected by soil pH, nutrients, and mean annual precipitation. Bacterial community assembly was mainly driven by variable selection (a deterministic process) in the Loess Plateau and the southern slope of Qinling Mountains, or by stochastic processes in the Mu Us Desert and the northern slope of Qinling Mountains. Fungal community assembly was primarily influenced by variable selection in different ecoregions, except for the Mu Us Desert. A highly connected subnetwork of microorganisms did not exist in the desert, but in the southern mountain slope the microbial network did harbor remarkably critical nodes. Bacterial keystone taxa that belonged to Chloroflexi were most relevant to shrub biomass traits. Our findings have implications for predicting the structure of microbial communities in shrubland soils in response to environmental change and their potential impact on plant growth. This study could improve our understanding of soil bacterial and fungal diversity and community assembly patterns in natural shrublands.
... A common-garden study on the development of soil organic matter (SOM) and SOM-related variables on a mining spoil heap in western Germany conducted with various 35-year-old coniferous and broadleafdeciduous trees, including Douglas-fir and beech monocultures and a mixture of hornbeam (Carpinus betulus), small-leaved lime and pedunculate oak, showed the highest organic carbon stock (forest floor plus uppermost 30 cm of the mineral soil) under the Douglas fir (35.17 ± 7.80 t ha − 1 ; Lorenz and Thiele-Bruhn, 2019). Tree species identity was found to exert the greatest influence on the C:N ratios of forest soils in a European-wide comparison. ...
Against the background of the ongoing climate change, forest science and Central-European forest management need information about tree species that are suitable of forming resistant and resilient multispecific and multipurpose forest stands. Non-native species are also considered for this purpose. One of these species may be the Douglas fir (Pseudotsuga menziesii), which has been introduced from western North America to Europe in the 19th century. The aim of this review is to compile recent scientific results that are relevant in the context of the use of the Douglas fir in future Central-European forestry to create a foundation for science-based decision-making, and to formulate future research tasks on that basis.
Due to its high growth rates and low susceptibility to needle cast fungi, the Douglas fir's coastal variety (P. menziesii var. menziesii, syn.: var. viridis) is being preferred in Central-European silviculture. It is competitively superior to all indigenous Central-European forest tree species due to rapid height growth and efficient shading of competing plants; high drought tolerance, water use efficiency and resilience after drought stress; and efficient water and nutrient uptake and high nutrient use efficiency. In Central Europe, the Douglas fir is currently less threatened by pests and pathogens than are the indigenous Norway spruce and Scots pine. Its litter is better decomposable compared to native conifers, but increased nitrification, especially at sites with former agricultural use or under anthropogenic nitrogen deposition, or lower nitrate uptake rates due to lower nitrogen demand of the species can result in enhanced soil acidification, aluminum mobilization and leaching of nitrate, “base” cations and aluminum compounds. Mixtures of Douglas fir and native trees may be particularly effective in sequestrating carbon and nitrogen in the soil. Negative effects of the Douglas fir on the plant diversity of a given community seem to be small or even non-existent, but its interactions with the fauna is more ambiguous. The majority of nature conservation organizations recommend avoiding Douglas-fir monocultures and restricting the fraction of Douglas-fir admixtures to stands of native tree species to 30% at maximum in considering current regulations for nature protection. Future research tasks comprise monitoring of the Douglas-fir provenances in cultivation and of introduced pests and pathogens, investigations of responses to consecutive and combined stress factors and of the species' invasiveness at dry sites as well as comparative long-term studies on interactions with animal communities and on matter flux and turnover in the ecosystems.
... Species ranking of FF and mineral topsoil C org and N t stocks as well as the vertical distribution was as expected from earlier findings (Achilles et al., 2021;Hagen-Thorn et al., 2004;Langenbruch et al., 2012;Lorenz & Thiele-Bruhn, 2019;Oostra et al., 2006;Peng et al., 2020;Vesterdal et al., 2008Vesterdal et al., , 2013. They provide further support that species could be grouped by their effect on C org and N t dynamics. ...
Temperate forest soils are often considered as an important sink for atmospheric C, thereby buffering anthropogenic CO2 emissions. However, the effect of tree species composition on the magnitude of this sink is unclear. We resampled a tree species common garden experiment (six sites) a decade after initial sampling to evaluate whether forest floor (FF) and topsoil organic carbon (Corg) and total nitrogen (Nt) stocks changed in dependence of tree species (Norway spruce - Picea abies L., European beech – Fagus sylvatica L., pedunculate oak – Quercus robur L., sycamore maple – Acer pseudoplatanus L., European ash – Fraxinus excelsior L. and small-leaved lime – Tilia cordata L.). Two groups of species were identified in terms of Corg and Nt distribution: (1) Spruce with high Corg and Nt stocks in the FF developed as a mor humus layer tended to have smaller Corg and Nt stocks and a wider Corg:Nt ratio in the mineral topsoil, and (2) the broadleaved species, of which ash and maple distinguished most clearly from spruce by very low Corg and Nt stocks in the FF developed as mull humus layer, had greater Corg and Nt stocks, and narrow Corg:Nt ratios in the mineral topsoil. Over 11 years, FF Corg and Nt stocks increased most under spruce, while small decreases in bulk mineral soil (esp. in 0-15 cm and 0-30 cm depth) Corg and Nt stocks dominated irrespective of species. Observed decadal changes were associated with site-related and tree species-mediated soil properties in a way that hinted toward short-term accumulation and mineralisation dynamics of easily available organic substances. We found no indication for Corg stabilization. However, results indicated increasing Nt stabilization with increasing biomass of burrowing earthworms, which were highest under ash, lime and maple and lowest under spruce.
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... In total, the biomass in the soil can equal or exceed the sum of all living biomass on the soil surface [18]. Microbial biomass C is even higher in the topmost centimetres of the soil, and in litter layers it reaches values of up to 10 000 µg C g −1 [2,40]. Especially for arable soils the very first centimetre of the soil surface is of high functional relevance. ...
Intact, ‘healthy’ soils provide indispensable ecosystem services that largely depend on the biotic activity. Soil health is connected with human health, yet, knowledge of the underlying soil functioning remains incomplete. This review highlights selected services, i.e. (i) soil as a genetic resource and hotspot of biodiversity, forming the basis for providing (ii) biochemical resources and (iii) medicinal services and goods. Soils harbour an unrivalled biodiversity of organisms, especially microorganisms. Some of the abilities of autochthonous microorganisms and their relevant enzymes serve (i) to improve natural soil functions and in particular plant growth, e.g. through beneficial plant growth-promoting, symbiotic and mycorrhizal microorganisms, (ii) to act as biopesticides, (iii) to facilitate biodegradation of pollutants for soil bioremediation and (iv) to yield enzymes or chemicals for industrial use. Soils also exert direct effects on human health. Contact with soil enriches the human microbiome, affords protection against allergies and promotes emotional well-being. Medicinally relevant are soil substrates such as loams, clays and various minerals with curative effects as well as pharmaceutically active organic chemicals like antibiotics that are formed by soil microorganisms. By contrast, irritating minerals, soil dust inhalation and misguided soil ingestion may adversely affect humans.
This article is part of the theme issue ‘The role of soils in delivering Nature’s Contributions to People.
... The SOM content of black soil is affected by many natural and anthropogenic factors. They include soil type [4][5][6], topography [7,8], climate [9][10][11], vegetation [12][13][14][15], land use [16][17][18], and so on. The different soil types lead to different soil nutrient losses, which lead to different accumulation of SOM. ...
Black soil is fertile, abundant with organic matter (OM) and is exceptional for farming. The black soil zone in northeast China is the third-largest black soil zone globally and produces a quarter of China’s commodity grain. However, the soil organic matter (SOM) in this zone is declining, and the quality of cultivated land is falling off rapidly due to overexploitation and unsustainable management practices. To help develop an integrated protection strategy for black soil, this study aimed to identify the primary factors contributing to SOM degradation. The geographic detector, which can detect both linear and nonlinear relationships and the interactions based on spatial heterogeneous patterns, was used to quantitatively analyze the natural and anthropogenic factors affecting SOM concentration in northeast China. In descending order, the nine factors affecting SOM are temperature, gross domestic product (GDP), elevation, population, soil type, precipitation, soil erosion, land use, and geomorphology. The influence of all factors is significant, and the interaction of any two factors enhances their impact. The SOM concentration decreases with increased temperature, population, soil erosion, elevation and terrain undulation. SOM rises with increased precipitation, initially decreases with increasing GDP but then increases, and varies by soil type and land use. Conclusions about detailed impacts are presented in this paper. For example, wind erosion has a more significant effect than water erosion, and irrigated land has a lower SOM content than dry land. Based on the study results, protection measures, including conservation tillage, farmland shelterbelts, cross-slope ridges, terraces, and rainfed farming are recommended. The conversion of high-quality farmland to non-farm uses should be prohibited.
... The highest dosage of biochar applied to the soil (16 t ha −1 ) allowed a greater microbial activity (i.e., higher SBR) that is capable of decomposing SOM, allowing a greater C-input into the soil system. Although this dosage also increased the metabolic quotient (which indicates the possibility of disturbances), the relationship between C-mic and the TOC contents (i.e., microbial quotient-qMic) ranged between 1 and 5%, which is expected for the total C organic in SOM (Lorenz and Thiele-Bruhn 2019), thus, ruling out any possibility of metabolic stress due to microrganismal activities. ...
The effects of coffee biochar residue combined with cow manure fertilizer on soil chemical attributes, microbial biomass, and structure and abundance of the soil microbial community are not fully understood. Thus, the objective of this study was to evaluate the effect of coffee biochar combined with cow manure on chemical and microbial attributes in soil cultivated with bean (Phaseolus vulgaris). We hypothesized that biochar from coffee residues drives the bacteria, fungi, and diazotrophic communities in a sandy soil and increases the abundance of these microorganism groups, raising soil basal respiration and microbial biomass. The experiment was carried out in a completely randomized design and was distributed in a factorial scheme (2 × 3 + 2) including two types of biochar (coffee ground-CG and coffee husk-CH) at three dosages (4, 8, and 16 t ha−1), and two control groups (S = native soil without treatment (−control) and E = fertilization with cow manure at dosage of 15 m3 ha−1 (+control)). The experiments were conducted with four repetitions. All treatments received the same dosage of cow manure applied in sandy soil and bean seeds were grown in pots. Soil samples were collected after 45 days to evaluate chemical attributes, total organic carbon (TOC), microbial biomass (C, N, and P), soil basal respiration, structure and abundance of total bacterial and fungal community (16S rRNA, 18S rRNA) and diazotrophs (nifH) in the soil by DGGE (denaturing gradient gel electrophoresis) and qPCR (real-time quantitative PCR), respectively. The results showed that TOC increased 9 and 11.5% with highest dosage of CG and CH biochar, respectively; thus, CG at 4 t ha−1 increased the C:N ratio in soil (4.7 times). The addition of biochar combined with cow manure increased soil basal respiration in CG at 16 t ha−1. The combined application of CH at 16 t ha−1 and cow manure increased the P content (2.37 times) and K+ (5.6 times). The highest increase in C from microbial biomass was found in CG at 16 t ha−1 and the addition of biochar and cow manure did not affect the P content in microbial biomass; nevertheless, biochar increased the nifH gene abundance by 8.23% at 16 t ha−1. Biochar addition influenced the structure of soil microbial communities, presenting distinct and well-differentiated communities in the multivariate analysis, according to the dosage and type of biochar. The group formed by different CG dosages showed a higher number of 16S genes, and greater amounts of Nmic, nifH, soil basal respiration, metabolic quotient, K, and Na. The major conclusion of this study was that coffee biochar, used in combination with cow manure, significantly improves the chemical and microbiological attributes of sandy soil cultivated with bean.
... This process is an important driver for soil characteristics such as soil carbon content, nitrogen content, cation exchange capacity and pH in the forest topsoil layer (Augusto et al. 2015;Dawud et al. 2016;Bohara, Yadav, Dong, Cao, & Hu, 2019). Xiao, Chen, Kumar, Chen, & Guan, (2019) stated that tree species diversity affects the microenvironment conditions and litter decomposition rate as well as the chemical composition of the litter of overstory species which are an essential factor for the soil carbon and nitrogen content (Guendehou et al. 2014) and influencing the soil pH and nutrients (Eshaghi Rad, 2014;Lorenz & Thiele-Bruhn, 2019). Also, Bartels and Chen (2013) concluded that total nitrogen content, exchangeable phosphorus, and cation exchange capacity had a significant positive correlation with the composition of tree species in the overstory stratum. ...
Revealing the effect of mixed beech and hornbeam stands on herb layer diversity is essential for sustainable forestry and biodiversity conservation since little is known in Hyrcanian forests. So, we studied the effects of such stands on understory diversity and soil physico-chemical properties in Hyrcanian forests of Iran. Forty sampled plots were established by random systematic sampling method with a regular 100 m × 200 m grid. At each sample point we recorded species identity and percent cover of each tree layer and herb layer species within plots of size 400 m2 (20 m × 20 m) and 100 m2 (10 m ×10 m) respectively. Soil samples were taken from 0 cm -10 cm and 10 cm - 30 cm soil depths. Cluster analysis was used to classify the samples based on the floristic composition data. Also detrended correspondence analysis (DCA) method was employed to assess the relationship between vegetation and environmental variables. There was no significant difference in terms of species richness, and diversity between mixed beech stands and hornbeam stands, but cluster analysis indicated that these stands were separated in two different groups based on herb layer species composition. DCA results showed that litter thickness, soil texture, total nitrogen, and organic carbon in the first layer were considered effective environmental variables in the distribution of sample plots in two stands. We observed that tree layer composition and soil characteristics were crucial contributors to variations of understory species composition which may be changed by forest management approaches over time. Tree layer composition and soil attributes can be considered effective factors for controlling and assessment of understory plant species composition. These findings could provide guidelines for conserving plant species diversity within any framework of sustainable forest management in Hyrcanian forests.
... Soil fauna play essential roles in soil ecological processes in terrestrial ecosystems (Berg & McClaugherty 2014;Lorenz & Thiele-Bruhn 2019). Researching the ecological role of soil fauna in soil processes contributes to understanding the mechanisms of material circulation and energy flows (Crowther et al. 2014;Janoušková et al. 2018). ...
As an arthropod biocide, naphthalene has been used in studies of the ecological functions of soil fauna for decades. However, its potential non-target effects on soil microorganisms may affect soil mineralization and litter decomposition processes. Therefore, we conducted an experiment with naphthalene adding to soil surface at a rate of 100 g·m−2 per month to examine the potential non-target effects of this treatment on soil fungal phospholipid fatty acids (PLFAs), 18S rDNA gene copy numbers and community diversity in a subalpine forest of western Sichuan, China. The results showed that naphthalene addition significantly increased fungal PLFAs but did not significantly alter fungal gene copy numbers. A total of 16 phyla, 62 genera and 147 Operational taxonomic units (OTUs) were identified through Illumina MiSeq sequencing analysis. Basidiomycota and Ascomycota were the most abundant phyla in both the control and naphthalene addition plots. Naphthalene addition did not affect the diversity or structure of the soil fungal community, but the increase in some genera of Basidiomycota might contribute to the increase in fungal PLFAs in the naphthalene addition plots. These results suggest that naphthalene exerts non-target effects on the active fungal abundance by stimulating the abundance of specific taxa in subalpine forest soils. The non-target effects of naphthalene on the fungal community should be taken into consideration when it is used to exclude soil fauna.
... Different litter quality in coniferous and broadleaf forests might explain the contrasting responses of C-oxidase and microbial biomass to thinning. Broadleaf forests tend to have higher N content and lower lignin content than coniferous forests (Wan et al., 2015;Lorenz and Thiele-Bruhn, 2019). The warmer and wetter soil environment induced by thinning promotes the decomposition of both high-quality broadleaves and low-quality needles. ...
Thinning profoundly affects soil microbial communities and carbon (C) cycling through altering soil microclimate, plant growth, C inputs and allocations. However, these effects are uncertain and may change with thinning intensity, recovery stage, forest type, and climate. Here, we conducted a global meta-analysis, based on 337 observations from 49 studies, to quantify the responses of soil properties, microbial biomass and community structure, and extracellular enzyme activities (EEAs) to thinning. We found that thinning did not change the total microbial biomass, but significantly shifted the soil microbial community structure and EEAs. Thinning stimulated both C-oxidase and C-hydrolase, but decreased the ratio of oligotrophic to copiotrophic microbes (i.e. fungi to bacteria ratio and Gram-positive bacteria to Gram-negative bacteria ratio) in the early recovery stage. In contrast, in the mid recovery stage, thinning enhanced C-oxidase but reduced C-hydrolase, and increased the ratio of oligotrophic to copiotrophic microbes. In the late recovery stage, neither community structure nor EEAs differed significantly between thinned and control stands. Such recovery dynamics reflect shifts of the resource-utilization strategies of microbes that are associated with community reorganization. Besides, the distinct litter quality between coniferous and broadleaf forests explained their different microbial responses. Overall, the current meta-analysis suggested that microbes can adapt the thinning-induced biotic and abiotic changes by adjustment of community structure rather than their biomass. The global patterns of how soil microbial community structure and EEAs respond to thinning deepen the understanding of the mechanisms underlying the thinning impacts on the soil C cycling.
... Some studies have investigated the effects of mixed plantations on soil OC, TN, and TP content and stocks (Cremer et al., 2016;Jiang et al., 2017). However, few studies have included an evaluation of C/N/P stoichiometry changes in mixed plantation soils (Lorenz and Thiele-Bruhn, 2019). In particular, the effects of mixed plantations on C/N/P stoichiometry and OC and nutrient content of soil aggregates remain largely unclear . ...
In forestry, stand conversion influences soil physicochemical and biological properties, yet the effects of conversion of pure plantation to uneven-aged mixed plantation on soil aggregate distribution and stability, C/N/P stoichiometry and enzyme activity remain unclear. We studied the distribution of water-stable aggregate fractions, mean weight diameter (MWD), stoichiometric ratios (C/N, C/P, and N/P), and urease, invertase, and acid phosphatase activity in the soils of pure and uneven-aged mixed plantations (including artificially and naturally established mixed plantations). The mixed plantations showed improved bulk soil and aggregate physiochemical and biological properties, including higher soil organic C (OC), total N (TN), total P (TP), and enzyme activity in the artificially mixed plantations than in the naturally established mixed plantation. Additionally, in contrast to pure plantation soil, mixed plantation soil showed a significant decrease in the microaggregate (MA) (<0.25 mm) mass fractions, and a marked increase in the proportion of large macroaggregate (LMA) (>2 mm), MWD, and other soil properties (especially OC and TN content, stoichiometric ratios, and enzyme activity in LMA). Principal component analysis indicated that compared to other aggregate sizes, LMA had a significant effect on soil properties, and LMA mass fractions were strongly positively correlated with OC, TN, C/N, and MWD in the bulk soils. Moreover, OC and nutrient content, stoichiometric ratios, and enzyme activity in LMA were significantly positively correlated with the corresponding variables in the bulk soils. These findings indicate that LMA properties can be used as sensitive indicators to changes in soil properties after stand conversion from pure to uneven-aged mixed plantation.
... The large differences in chemical soil properties between Q. rubra and control plots were expected to be associated with the differences in elemental composition of senesced leaves, as initial litter quantity and quality is one of main factors affecting its decomposition rate and soil properties (Chen et al., 2015;Dobrylovská, 2001;Jonczak et al., 2015). Large production of low-quality and hardly decomposable litter with low N content and high C/N ratio by Q. rubra is reflected in differences in soil C and N content between Q. rubra and native plant communities, as observed in our and previous studies (Finzi et al., 1998a;Jonczak et al., 2015;Lorenz and Thiele-Bruhn, 2019). Relatively low N content and high C/N ratio in Q. rubra senesced leaves may lead to N-immobilization in soils overgrown by this species. ...
This study assessed the effects of invasive Quercus rubra on soil physicochemical properties and understory vegetation in native plant communities. Chemical properties of senesced tree leaves were also analysed. The study was performed at paired invaded-native plots in managed forests in southern Poland. Freshly fallen senesced leaves were characterized in terms of C, Ca, K, Mg, N, P, total phenolics and condensed tannins concentrations. Soil physicochemical parameters, namely bulk soil density, moisture, water holding capacity (WHC), pH, organic C, total Ca, K, Mg, N, P, exchangeable Ca, K, Mg, N-NH4, N-NO3, P-PO4, and total phenolics were analysed in organic and mineral soil horizons, and condensed tannins were analysed in organic soil horizon. The diversity, cover and composition of understory vegetation were assessed. Although, senesced leaves of Q. rubra and native trees, Quercus robur, Fagus sylvatica, Carpinus betulus and Acer pseudoplatanus among others, differed only in total K, N and C/N ratio, we observed considerable differences in soil physicochemical parameters between the plot types. Soil beneath Q. rubra was characterised by significantly lower WHC, organic C, total Mg, N, P, exchangeable Ca, Mg, N-NH4, N-NO3, total phenolics and higher moisture in organic and mineral soil horizons as well as lower content of P-PO4 and condensed tannins in organic soil horizon relative to native plant communities. Q. rubra negatively influenced species richness and cover of understory vegetation. The changes in soil physicochemical parameters and understory vegetation under Q. rubra may be associated with low quality (low N, high C/N) litter that decomposes slowly and generates a physical barrier, limiting seed germination and seedling growth. The changes in soil properties and vegetation under invasive Q. rubra indicate that this species may alter the structure and function of forest ecosystems and should be avoided in forest management practices.
... Removal of the natural vegetation led to root decomposition and organic acid exudation in the deeper layers, which then contributed to acidification-a common tendency linked to afforestation (Holubík et al., 2014)-helping to slow mineralization (Malavolta, 1987;Moreira and Costa, 2004;Chen et al., 2017) and increase organic matter retention. In fact, the resemblance between C4 an SF60 was not expected, due the tree species' effect on soil carbon stocks (Lorenz and Thiele-Bruhn, 2019), but the elapse of time after conversion in C4 explains the lack of significant difference between these areas. ...
Rosewood (Aniba rosaeodora Ducke) is an endangered Amazonian tree species that produces a commercially valuable essential oil, used mainly in cosmetics and fine fragrances production. The species can also be used in reforestation programs, which generate jobs and as a source of income and reduce the pressure of exploitation on natural rosewood populations. The objective of this study was to verify the influence of rosewood stands on physical and chemical soil attributes. This study was conducted at a rural farm in the Maués municipality, 350 km from Manaus, Amazonas State, Brazil. Samples were collected in five areas; 4-, 10-and 20-year-old rose-wood stands, and 15-and 60-year-old secondary forests. The latter two served as control treatments, reflecting natural spontaneous succession conditions over time. Soil was sampled at 10 equidistant points within each area to measure physicochemical attributes, and at the center of each one, a soil profile was dug for description and classification of morphological characteristics. Based on the profile description, the soils were classified as Xanthic Hapludox. The results show that soil conditions under 20-year-old rosewood stand resembled those beneath the 60-year-old secondary forest, and likewise for the soil under the 10-year-old rosewood stand and the 15-year-old secondary forest. The soil bulk density ranged from 0.81 to 0.99 g cm −3 among all areas and no significant difference was found (P = 0.052). With exception to 4-year-old stand, the organic matter (2.68-5.87%) and carbon stock (18.57-31.71 Mg ha −1) did not differ significantly between stands and control treatments. For the soil macronutrients, nitrogen (0.10-0.22%), phosphorus (1.17-11.70 mg kg −1), calcium (0.03-0.31 mg kg −1) and magnesium (0.02-0.16 mg kg −1) were higher or equal in the rosewood stands in comparison to the two controls , while the potassium values (0.03-0.36 mg kg −1) were significantly higher in 60-year-old secondary forests only compared to the 10-year-old rosewood stands (P = 0.005). The soil beneath the 4-year-old rosewood stand, however, differed from the other four areas, having significantly higher natural clay content (>600 g kg −1) and higher topsoil chemical concentrations, associated with the more recent burning. This result represents the first step in addressing concern about sustainable soil use in rosewood forestry economics. Consequently, this kind of rosewood plantation can be recommended as an appropriate use of historically exploited areas, providing economic return from local biodiversity.
... This process is an important driver for soil characteristics such as soil carbon content, nitrogen content, cation exchange capacity and pH in the forest topsoil layer (Augusto et al. 2015;Dawud et al. 2016;Bohara, Yadav, Dong, Cao, & Hu, 2019). Xiao, Chen, Kumar, Chen, & Guan, (2019) stated that tree species diversity affects the microenvironment conditions and litter decomposition rate as well as the chemical composition of the litter of overstory species which are an essential factor for the soil carbon and nitrogen content (Guendehou et al. 2014) and influencing the soil pH and nutrients (Eshaghi Rad, 2014;Lorenz & Thiele-Bruhn, 2019). Also, Bartels and Chen (2013) concluded that total nitrogen content, exchangeable phosphorus, and cation exchange capacity had a significant positive correlation with the composition of tree species in the overstory stratum. ...
The degradation of organic matter in soils plays an important role in the carbon cycle. Lignin is the main source of soil organics and it can be used to trace the source, distribution and turnover of organic matter. In this study the distribution and degradation of lignin were investigated to identify the source and degradation of soil organic matter during the succession of China's Zoige Plateau. Lignin monomers were determined by gas chromatography-mass spectrometry with alkaline CuO oxidation and the soils' δ¹³C and δ¹⁵N contents were interpreted to explore the turnover rate of lignin and organic matter. The main source of organics was identified as C3 non-woody angiosperm tissues. Lignin in the topsoil (0–30 cm) was derived from litter and roots, and it then migrated vertically to the deep soil (30–80 cm). Correlations of δ¹³C/δ¹⁵N with the soil's elemental composition showed that the organics degraded more quickly in meadow soil than in bog soil. The soil communities in the meadow and bog soils were generally similar, but there were certain differences in the dominant microbial phyla at different depths. The meadow soil's effectiveness as a carbon sink was gradually weakened, while that of the bog soil strengthened with depth. These results provide a scientific basis for accurately assessing the carbon sink capacity of the soils in Zoige Plateau.
The elevation is a complicated environmental factor that affects the availability of light, temperature, soil nutrients, and moisture, thereby affecting the mountain ecosystem. However, it is unclear how the C:N:P ecological stoichiometry of leaf, soil, and litter changes along the altitudinal gradient, especially in the karst ecosystem in Southwest China. This work investigated the soil organic carbon (SOC), total phosphorus (TP), and total nitrogen (TN) contents, and the corresponding stoichiometric ratios of Pseudotsuga sinensis leaf, litter, and soil at an elevation range of 2127–2302 m in the northwestern Guizhou Province of China. The results indicated that altitude significantly affected the nutrient contents and stoichiometric ratios of P. sinensis in leaf, soil, and litter. The mean contents of C, N, and P in the P. sinensis forests were 473.57, 14.49, and 1.97 mg·g−1 for leaves; 422.35, 8.36, and 1.08 mg·g−1 for litter; and 40.59, 2.44, and 1.04 mg·g−1 for soil, respectively. The C, N, and P contents of soil and leaf increased significantly, whereas those in the litter decreased significantly with elevation. The average ratios of C:N, C:P, and N:P were 32.97, 244.60, and 7.42 for leaves; 51.38, 395.53, and 7.79 for litter; and 16.68, 38.84, and 2.34 for soil, respectively. The leaf C:N, N:P, and C:P ratios showed a linear decrease with an increase in altitude, whereas C:P and C:N ratios in the litter and N:P and C:P ratios in soil showed a linear increase with an increase in altitude. The resorption efficiency of both N and P of P. sinensis increased remarkably with altitude. The mean resorption efficiency of P (43.84%) was higher than that of N (40.91%). Since the N:P ratio in leaves predicts limited nutrition for plant development, we hypothesized that the N element limited the development of P. sinensis. Besides, nutrient contents were markedly related to the ratios in P. sinensis leaves, litter, and soil. The results indicate that P. sinensis had developed a favorable strategy to adapt to the high altitude and cope with unfavorable soil nutrient conditions. The N element was mainly limited to the development of P. sinensis. The P. sinensis had developed a favorable strategy to adapt to the high altitude and cope with unfavorable soil nutrient conditions. These findings highlight the relationship between the C:N:P stoichiometric ratios and altitude in plants, soils, and litters in the karst forest ecosystem, and provide insight on the better management of the karst forest ecosystems in Southwest China.
Climate change has increased attention paid in the research to forest soils and tree species composition, in respect to the potential for carbon sequestration. It is known that forest stands are able to store soil organic carbon (SOC), but little is known about the effect of forest naturalness on SOC content. This is important in relation of dying of unnatural spruce stands. It is necessary to determine a suitable composition of tree species which will replace them. This research is based on 248 plots with oak, beech, and spruce stands and mixtures of these species, with measured values of SOC. Our results show that autochthonous and mixed stands, in terms of tree species composition, in the study area had a higher SOC content than allochthonous and pure stands. In addition, it was found that autochthonous oak and beech stands, especially in mixtures, had a higher SOC content than allochthonous spruce stands (monocultures). On the basis of the presented results, it is possible to optimize the future tree species composition of stands in the study area, which currently have an allochthonous representation of spruce, to provide better function of carbon sequestration and resistance to climate change.
Aim of study: To determine the effects of stand characteristics, which closely relate to forest management practices, on the soil organic carbon (SOC) content in the organic (O) and surface mineral (A) soil horizons in spruce and deciduous stands, and to show SOC dynamics during the life of production stands.
Area of study: Spruce and deciduous stands located throughout the Czech Republic.
Material and methods: The effects of age, density of stocking and canopy of stand on SOC content in the O and A horizons, and the difference between categories of variables and the trends of SOC were evaluated in spruce and deciduous stands (401 plots) at lower and middle elevations.
Main results: SOC content changed during the life of stands. In spruce stands, a decreasing trend of SOC with stand age was found in the A horizon. In deciduous stands, SOC content was higher overall in the A horizon, fluctuating slightly with stand age, but more balanced during the life of stands. Based on the results, in terms of management of dying spruce stands and carbon sequestration, felling should be carried out in the age group of 81-120 years in spruce stands, whereas in deciduous stands felling should take place in older stands (141 years and more). Density of stocking and canopy of stand had no substantial effect of SOC content.
Research highlights: Deciduous stands have the potential to replace dying spruce stands at lower elevation in terms of carbon sequestration.
Nature of the tree species used for revegetation of post-mining land affects the soil carbon and nutrient stocks. This study was aimed at a comparative evaluation of Cassia siamea and Albizia lebbeck for their potential to increase the carbon and nutrient stocks in mined land. Soil and plant samples were collected from chronosequence (3–16 years) sites and evaluated for biomass stock, soil C, nutrient contents, microbial biomass, and dehydrogenase activity. The increase in tree height, diameter at breast height, and biomass weight with age was observed to be higher in C. siamea than A. lebbeck. Biomass carbon stock increased from 0.97 Mg ha⁻¹ to 54.81 Mg ha⁻¹ for C. siamea and from 0.60 Mg ha⁻¹ to 48.96 Mg ha⁻¹ for A. lebbeck for 3–16-year old sites. Soil dehydrogenase activity and microbial biomass C were higher in C. siamea (32.5–102 µg TPF g⁻¹ 24 h⁻¹, 116–416 mg kg⁻¹) compared to A. lebbeck (24.6–88.2 µg TPF g⁻¹ 24 h⁻¹, 92–377 mg kg⁻¹). In C. siamea, soil carbon stock increased from 6.61 to 24.04 Mg ha⁻¹ and in A. lebbeck from 6.10 to 21.43 Mg ha⁻¹ along the chronosequence. Overall, there was 3.5-fold increase in soil carbon stock, 5.5 and 2.5-fold increase in soil available N and available P stock, and a 30-fold increase in the available K stock along the age gradient of reclaimed mine soil. Reclamation time played a major role in increasing the soil C and nutrient stocks, where C. siamea performed comparatively better than A. lebbeck.
Drought-sensitive European beech forests are increasingly challenged by climate change. Admixing other, preferably more deep-rooting, tree species has been proposed to increase the resilience of beech forests to drought. This diversification of beech forests might also affect soil organic carbon (SOC) and total nitrogen (TN) stocks that are relevant for a wide range of soil functions and ecosystem services, such as water and nutrient retention, filter functions and erosion control. Since information of these effects is scattered, our aim was to synthesize results from studies that compared SOC/TN stocks of beech monocultures with those of beech stands mixed with other tree species as well as monocultures of other tree species. We conducted a meta-analysis including 38 studies with 203, 220, and 160 observations for forest floor (i.e., the organic surface layer), mineral soil (0.5 m depth) and the total soil profile, respectively. Monoculture conifer stands had higher SOC stocks compared to monoculture beech in general, especially in the forest floor (up to 200% in larch forests). In contrast, other broadleaved tree species (oak, ash, lime, maple, hornbeam) showed lower SOC stocks in the forest floor compared to beech, with little impact on total SOC stocks. Comparing mixed beech-conifer stands (average mixing ratio with regard to number of trees 50:50) with beech monocultures revealed significantly higher total SOC stocks of around 9% and a smaller increase in TN stocks of around 4%. This equaled a SOC accrual of 0.1 Mg ha ⁻¹ yr ⁻¹ . In contrast, mixed beech-broadleaved stands did not show significant differences in total SOC stocks. Conifer admixture effects on beech forest SOC were of additive nature. Admixing other tree species to beech monoculture stands was most effective to increase SOC stocks on low carbon soils with a sandy texture and nitrogen limitation (i.e., a high C/N ratio and low nitrogen deposition). We conclude that, with targeted admixture measures of coniferous species, an increase in SOC stocks in beech forests can be achieved as part of the necessary adaptation of beech forests to climate change.
Soil microorganisms, which mediate all events happening in the soil, are also a sensitive indicator of the changes occurring in soil organic matter. Fir-beech mixed stand located in the Arıt district of Bartın province is chosen as the study area. In this study, it is aimed to determine microbial biomass C, N and P contents according to seasons. The material part of the study consists of forest floor samples (20x20 cm area) taken under the stand. For some chemical and microbial analyzes of forest floor samples, 15 forest floor samples (total 120 samples) were taken in the spring, summer, autumn and winter seasons. Microbial biomass C, N and P contents of forest floor samples were determined by chloroform-fumigation-extraction method. The average pH of the forest floor samples is
shown in the lowest summer season (6.49), the highest winter season (6.96). The lowest organic C (Corg) content of the samples is observed in summer (18.1%) season and the highest spring season (36.8%). The highest microbial biomass C (Cmic) content of the forest floor samples is determined in the autumn season (5492.30 µg g-
1) and the highest microbial biomass N (Nmic) content is detected in the summer season (715.23 µg g-1). In addition, the lowest microbial biomass P (Pmic) content in the study area is found as 370.71 µg g-1 in the autumn season. According to the results of the simple variance analysis (One-Way ANOVA), some chemical properties (moisture,
pH and organic C, etc.) and microbial biomass C, N and P contents of forest floor samples are varied with the seasons.
Keywords: Organic carbon, microbial biomass, mixed stand, seasonal change, forest floor.
Silviculture of appropriate tree species can improve soil properties, subsequently ameliorating the productivity and ecological functions. However, it is not clear about the differences in the effects of tree species on soil properties in secondary forest ecosystems. In this study, four stands of 60–70 years secondary forests were chosen. Eight replicate individuals of five common native tree species: Acer mono, Quercus mongolica, Juglans mandschurica, Fraxinus rhynchophylla, and Fraxinus mandschurica were selected in each stand to test the effects of tree species on soil properties in a typical temperate secondary forest ecosystem in Northeast China. Forest floor, soil at three depths (0–10, 10–20 and 20–40 cm) were compared among five tree species. Our findings showed significant differences in soil mineral nitrogen (N) (i.e. NH4⁺-N and NO3–-N) and available phosphorus (P), microbial biomass C (MBC), microbial biomass N (MBN) and enzyme activities depending on the tree species. At 0–10 cm soil depth, F. mandschurica soils exhibited 18–28% higher mineral N than those A. mono, F. rhynchophylla, and Q. mongolica, 24–38% higher available P than Q. mongolica and F. rhynchophylla. Similarly, F. mandschurica soils showed 64–66% higher MBC and MBN than Q. mongolica, and 41–133% higher β-glucosidase enzyme activity than J. mandshurica, F. rhynchophylla, and Q. mongolica. At 10–20 cm soil depth, F. mandschurica exhibited higher soil mineral N and available P concentrations, MBC, enzyme activities of phenol oxidase, exoglucanase, and β-glucosidase than the other tree species. At 20–40 cm soil depth, there were no difference in soil mineral N and available P, MBC, MBN, and enzyme activities among five tree species. No differences were observed between the tree species in the C, N, and C/N ratio of forest floor; however, the C/N ratio of fine roots was lower for F. mandschurica than for Q. mongolica. Significant correlations were established between C/N ratio of fine roots and soil mineral N and available P, MBC and MBN, and phenol oxidase. This suggests that the high quality of F. mandschurica fine roots improved soil chemical and microbial properties. Nevertheless, these native tree species exhibited improving soil chemical and microbial properties, compared to larch plantation soils in secondary forest ecosystems. Therefore, we suggest that introduction of F. mandschurica followed by that of A. mono and J. mandshurica, and then Q. mongolica and F. rhynchophylla into larch plantations should be considered for restoring the degraded soils in plantations.
Processes underlying soil organic matter (SOM) transformations meet growing interest as SOM contains more carbon (C) than global vegetation and the atmosphere combined. Therefore, SOM is a crucial element of the C cycle, especially in ecosystems rich in organic matter, such as boreal forests. However, climate change may shift the fate of this SOM from C sink into C source, accelerating global warming. These processes require a better understanding of the involved mechanisms driving both the C cycle and the interlinked nitrogen (N) cycle. SOM transformations are balanced by a network of interactions between biological, chemical and physical factors. In this review, we discuss the findings of the most recent studies to the current state of knowledge about the main players in SOM transformations. We focus especially on plant-derived secondary metabolites, as their biochemical traits, especially interactions with soil microbial communities, organic N compounds and enzymes make them potential regulators of SOM decomposition. However, yet these regulatory abilities of plant-derived compounds are not fully explored.
This article is an as simple as possible key of classification of terrestrial (aerobic, not submersed) topsoils (organic and organic-mineral series of soil horizons). Based on the introduction exposed in Humusica 1, article 1, and using vocabulary and definitions listed in article 4, a classification is proposed for better understanding the biological functioning of the soil, partially disclosing the process of litter digestion. Five types of terrestrial topsoils, called terrestrial humus systems, are described and illustrated with the help of photographs. Within each humus system, 3–4 humus forms are also revealed, corresponding to similar series of soil horizons generated in a relatively homogeneous environment whose range of ecological factors is not so large to overstep and cause the genesis of another different humus system. The article ends with a figure that shows the relationship between Tangel and Amphi humus systems, and a dichotomous key of classification that one can easily print and bring in the field for practicing humus classification.
Most heterotrophic organisms feed on substrates that are poor in nutrients compared to their demand, leading to elemental imbalances that may constrain their growth and function. Flexible carbon (C)-use efficiency (CUE, C used for growth over C taken up) can represent a strategy to reduce elemental imbalances. Here, we argue that metabolic regulation has evolved to maximise the organism growth rate along gradients of nutrient availability and translated this assumption into an optimality model that links CUE to substrate and organism stoichiometry. The optimal CUE is predicted to decrease with increasing substrate C-to-nutrient ratio, and increase with nutrient amendment. These predictions are generally confirmed by empirical evidence from a new database of c. 2200 CUE estimates, lending support to the hypothesis that CUE is optimised across levels of organisation (microorganisms and animals), in aquatic and terrestrial systems, and when considering nitrogen or phosphorus as limiting nutrients.
The formation and turnover of soil organic matter (SOM) includes the biogeochemical processing of the macronutrient elements nitrogen (N), phosphorus (P) and sulphur (S), which alters their stoichiometric relationships to carbon (C) and to each other. We sought patterns among soil organic C, N, P and S in data for c. 2000 globally distributed soil samples, covering all soil horizons. For non-peat soils, strong negative correlations (p < 0.001) were found between N:C, P:C and S:C ratios and % organic carbon (OC), showing that SOM of soils with low OC concentrations (high in mineral matter) is rich in N, P and S. The results can be described approximately with a simple mixing model in which nutrient-poor SOM (NPSOM) has N:C, P:C and S:C ratios of 0.039, 0.0011 and 0.0054, while nutrient-rich SOM (NRSOM) has corresponding ratios of 0.12, 0.016 and 0.016, so that P is especially enriched in NRSOM compared to NPSOM. The trends hold across a range of ecosystems, for topsoils, including O horizons, and subsoils, and across different soil classes. The major exception is that tropical soils tend to have low P:C ratios especially at low N:C. We suggest that NRSOM comprises compounds selected by their strong adsorption to mineral matter. The stoichiometric patterns established here offer a new quantitative framework for SOM classification and characterisation, and provide important constraints to dynamic soil and ecosystem models of carbon turnover and nutrient dynamics.
Objectives
Afforestation changes soil chemical properties over several decades. In contrast, microbial community structure can be shifted within the first decade and so, the direct effects of tree species can be revealed. The aim of this study was to determine the alteration of soil microbial community composition 10 years after afforestation by trees with contrasting functional traits. Methods
The study was conducted at the BangorDIVERSE temperate forest experiment. Soil samples were collected under single, two and three species mixtures of alder and birch, beech and oak - early and secondary successional species, respectively, and contiguous agricultural field. Soil was analysed for total carbon (C) and nitrogen (N) contents, and microbial community structure (phospholipid fatty acids (PLFAs) analysis). Results and conclusionsThe total PLFAs content (370–640 nmol g−1 soil) in forest plots increased for 30 to 110 % compared to the agricultural soil (290 nmol g−1 soil). In contrast, soil C, N and C/N ratios were altered over 10 years much less - increased only up to 20 % or even decreased (for beech forest).Afforestation increased bacterial PLFAs by 20–120 %, whereas it had stronger impact on the development of fungal communities (increased by 50–200 %). These effects were proved for all forests, but were more pronounced under the monocultures compared to mixtures. This indicates that species identity has a stronger effect than species diversity. Principal component analysis of PLFAs revealed that under mono and three species mixtures similar microbial communities were formed. In contrast, gram-positive PLFAs and actinomycete PLFAs contributed mainly to differentiation of two species mixtures from other forests. Thus, at the early afforestation stage: i) soil biological properties are altered more than chemical, and ii) tree species identity affects more than species amount on both processes.
We explored tree species diversity effects on soil C stock, C/N ratio, and pH as compared with effects of tree species identity. We sampled forest floors and mineral soil (0–40 cm) in a diversity gradient of 1–5 tree species composed of conifers and broadleaves in Białowieża Forest, Poland. Diversity was a weaker driver than identity of soil C stocks, C/N ratio, and pH in the soil profile. However, there were significant non-additive effects of diversity and significant effects of identity on C stock and C/N ratio within different parts of the soil profile. More diverse forests had higher C stocks and C/N ratios in the 20–40 cm layer, whereas identity in terms of conifer proportion increased C stocks and C/N ratios only in forest floors. A positive relationship between C stocks and root biomass in the 30–40 cm layer suggested that belowground niche complementarity could be a driving mechanism for higher root carbon input and in turn a deeper distribution of C in diverse forests. Diversity and identity affected soil pH in topsoil with positive and negative impacts, respectively. More diverse forests would lead to higher soil nutrient status as reflected by higher topsoil pH, but there was a slight negative effect on N status as indicated by higher C/N ratios in the deeper layers. We conclude that tree species diversity increases soil C stocks and nutrient status to some extent, but tree species identity is a stronger driver of the studied soil properties, particularly in the topsoil.
Key messageCombined effects of litterfall and root turnover significantly increase topsoil carbon stocks in Norway spruce and European beech mixed forests, indicating local complementarity effects mediated by tree species mixtures. ContextThe establishment of mixed stands by intermingling individuals of European beech and Norway spruce is an ongoing trend in adaptive forest management strategies. However, our understanding of the potential of these strategies to promote C sequestration remains limited. AimsThis study aims to assess the effect of species composition on SOC stock in a mixed forest of Norway spruce and European beech. Methods
We studied C stocks in the uppermost soil layers in two stands dominated either by Norway spruce or European beech and in a mixture of both species. We evaluated the effect of litterfall and root turnover on soil organic carbon (SOC) stocks and its spatial distribution by combining structural equation models and geostatistical techniques. ResultsC stocks in the forest floor were highest in Norway spruce, whereas in the mineral soil, the highest values were in the mixed stand. The proportion of Norway spruce litterfall was positively related to C stock in the forest floor across stands. Root turnover was positively related to C stock in the mineral soil of the mixed stand. Conclusion
Our results confirm a contrasting role of root turnover and litterfall between soil layers in the studied stands, suggesting that tree species composition can mediate the spatial distribution of SOC stocks in mixed forests.
Understanding the potential of soil to store organic carbon (SOC) is important for potential climate change mitigation strategies and assessing soil health issues. We examined the factors controlling SOC storage in eastern Australian soils and how these vary with depth. Models were developed using a set of readily interpreted covariates to represent key soil forming factors together with multiple linear regression and Cubist piecewise decision tree techniques. Independent validation demonstrated concordance correlation coefficients up to 0.68 for SOC density in near surface layers but progressively decreasing with depth.
The results demonstrate the key role of climate (rainfall and maximum temperatures) in controlling SOC stocks, with parent material (lithology) and vegetation cover also being key drivers, whilst topography and aspect are of lesser influence, at least at this sub-continental scale. The relative influence of temperature and land use/vegetation cover decreases with depth, while that of parent material increases. The necessity of considering a combination of factors when deriving meaningful estimates of current or projected SOC storage is demonstrated with quantitative estimates of SOC stocks in 45 different climate-parent material-vegetation cover regimes. Average SOC stocks in the 0-30 cm depth interval range from 16.3 Mg ha-1 in dry, highly siliceous parent material environments with low vegetation cover, up to over 145.0 Mg ha-1 in wet, mafic parent material environments with high vegetation cover. Results suggest that the proportion of SOC stock in the 30-100 cm interval as a proportion of the top 100 cm varies from a low of 41% in wet climates up to a high of 59% in dry climates. Climate appears to be the dominant controller of subsoil SOC storage proportion, with parent material and vegetation cover also having restricted influence.
Tree species interact with soil biota to impact soil organic carbon (C) pools, but it is unclear how this interaction is shaped by various ecological factors. We used multiple regression to describe how ~100 variables were related to soil organic C pools in a common garden experiment with 14 temperate tree species. Potential predictor variables included: (i) the abundance, chemical composition, and decomposition rates of leaf litter and fine roots, (ii) species richness and abundance of bacteria, fungi, and invertebrate animals in soil, and (iii) measures of soil acidity and texture. The amount of organic C in the organic horizon and upper 20 cm of mineral soil (i.e. the combined C pool) was strongly negatively correlated with earthworm abundance and strongly positively correlated with the abundance of aluminum, iron, and protons in mineral soils. After accounting for these factors, we identified additional correlations with soil biota and with litter traits. Rates of leaf litter decomposition, measured as litter mass loss, were negatively correlated with size of the combined soil organic C pool. Somewhat paradoxically, the combined soil organic C pool was also negatively related to the ratio of recalcitrant compounds to nitrogen in leaf litter. These apparent effects of litter traits probably arose because two independent components of litter ''quality'' were controlling different aspects of decomposition. Leaf litter mass loss rates were positively related with leaf litter calcium concentrations, reflecting greater utilization and depolymerization of calcium-rich leaf litter by earthworms and other soil biota, which presumably led to greater proportional losses of litter C as CO2 or dissolved organic C. The fraction of depolymerized and metabolized litter that is ultimately lost as CO2 is an inverse function of microbial C use efficiency, which increases with litter nutrient concentrations but decreases with concentrations of recalcitrant compounds (e.g. lignin); thus, high ratios of recalcitrant compounds to nitrogen in leaf litter likely caused a greater fraction of depolymerized litter to be lost as CO2. Existing conceptual models of soil C stabilization need to reconcile the effects of litter quality on these two potentially counteracting factors: rates of litter depolymerization and microbial C use efficiency.
This study investigated the possible effects of tree species diversity and identity on the soil microbial community in a species-rich temperate broad-leaved forest. For the first time, we separated the effects of tree identity and tree species diversity on the link between above and belowground communities in a near-natural forest. We established 100 tree clusters consisting of each three tree individuals represented by beech (Fagus sylvatica L.), ash (Fraxinus excelsior L.), hornbeam (Carpinus betulus L.), maple (Acer pseudoplatanus L.), or lime (Tilia spec.) at two different sites in the Hainich National Park (Thuringia, Germany). The tree clusters included one, two or three species forming a diversity gradient. We investigated the microbial community structure, using phospholipid fatty acid (PLFA) profiles, in mineral soil samples (0–10 cm) collected in the centre of each cluster.
Tree species diversity has been reported to increase forest ecosystem above-ground biomass and productivity, but little is known about below-ground biomass and production in diverse mixed forests compared to single-species forests. For testing whether species richness increases below-ground biomass and production and thus complementarity between forest tree species in young stands, we determined fine root biomass and production of trees and ground vegetation in two experimental plantations representing gradients in tree species richness. Additionally, we measured tree fine root length and determined species composition from fine root biomass samples with the near-infrared reflectance spectroscopy method. We did not observe higher biomass or production in mixed stands compared to monocultures. Neither did we observe any differences in tree root length or fine root turnover. One reason for this could be that these stands were still young, and canopy closure had not always taken place, i.e. a situation where above- or below-ground competition did not yet exist. Another reason could be that the rooting traits of the tree species did not differ sufficiently to support niche differentiation. Our results suggested that functional group identity (i.e. conifers vs. broadleaved species) can be more important for below-ground biomass and production than the species richness itself, as conifers seemed to be more competitive in colonising the soil volume, compared to broadleaved species.
It has been recognized for a long time that the overstorey composition of a forest partly determines its biological and physical-chemical functioning. Here, we review evidence of the influence of evergreen gymnosperm (EG) tree species and deciduous angiosperm (DA) tree species on the water balance, physical-chemical soil properties and biogeochemical cycling of carbon and nutrients. We used scientific publications based on experimental designs where all species grew on the same parent material and initial soil, and were similar in stage of stand development, former land use and current management. We present the current state of the art, define knowledge gaps, and briefly discuss how selection of tree species can be used to mitigate pollution or enhance accumulation of stable organic carbon in the soil. The presence of EGs generally induces a lower rate of precipitation input into the soil than DAs, resulting in drier soil conditions and lower water discharge. Soil temperature is generally not different, or slightly lower, under an EG canopy compared to a DA canopy. Chemical properties, such as soil pH, can also be significantly modified by taxonomic groups of tree species. Biomass production is usually similar or lower in DA stands than in stands of EGs. Aboveground production of dead organic matter appears to be of the same order of magnitude between tree species groups growing on the same site. Some DAs induce more rapid decomposition of litter than EGs because of the chemical properties of their tissues, higher soil moisture and favourable conditions for earthworms. Forest floors consequently tend to be thicker in EG forests compared to DA forests. Many factors, such as litter lignin content, influence litter decomposition and it is difficult to identify specific litter-quality parameters that distinguish litter decomposition rates of EGs from DAs. Although it has been suggested that DAs can result in higher accumulation of soil carbon stocks, evidence from field studies does not show any obvious trend. Further research is required to clarify if accumulation of carbon in soils (i.e. forest floor + mineral soil) is different between the two types of trees. Production of belowground dead organic matter appears to be of similar magnitude in DA and EG forests, and root decomposition rate lower under EGs than DAs. However there are some discrepancies and still are insufficient data about belowground pools and processes that require further research. Relatively larger amounts of nutrients enter the soil-plant biogeochemical cycle under the influence of EGs than DAs, but recycling of nutrients appears to be slightly enhanced by DAs. Understanding the mechanisms underlying forest ecosystem functioning is essential to predicting the consequences of the expected tree species migration under global change. This knowledge can also be used as a mitigation tool regarding carbon sequestration or management of surface waters because the type of tree species affects forest growth, carbon, water and nutrient cycling.
Terrestrial microbial decomposer communities thrive on a wide range of organic matter types that rarely ever meet their elemental demands. In this review we synthesize the current state-of-the-art of microbial adaptations to resource stoichiometry, in order to gain a deeper understanding of the interactions between heterotrophic microbial communities and their chemical environment. The stoichiometric imbalance between microbial communities and their organic substrates generally decreases from wood to leaf litter and further to topsoil and subsoil organic matter. Microbial communities can respond to these imbalances in four ways: first, they adapt their biomass composition toward their resource in a non-homeostatic behavior. Such changes are, however, only moderate, and occur mainly because of changes in microbial community structure and less so due to cellular storage of elements in excess. Second, microbial communities can mobilize resources that meet their elemental demand by producing specific extracellular enzymes, which, in turn, is restricted by the C and N requirement for enzyme production itself. Third, microbes can regulate their element use efficiencies (ratio of element invested in growth over total element uptake), such that they release elements in excess depending on their demand (e.g., respiration and N mineralization). Fourth, diazotrophic bacteria and saprotrophic fungi may trigger the input of external N and P to decomposer communities. Theoretical considerations show that adjustments in element use efficiencies may be the most important mechanism by which microbes regulate their biomass stoichiometry. This review summarizes different views on how microbes cope with imbalanced supply of C, N and P, thereby providing a framework for integrating and linking microbial adaptation to resource imbalances to ecosystem scale fluxes across scales and ecosystems.
The capacity of soils to store organic carbon represents a key function of soils that is not only decisive for climate regulation but also affects other soil functions. Recent efforts to assess the impact of land management on soil functionality proposed that an indicator- or proxy-based approach is a promising alternative to quantify soil functions compared to time- and cost-intensive measurements, particularly when larger regions are targeted. The
objective of this review is to identify measurable biotic or abiotic properties that control soil organic carbon (SOC) storage at different spatial scales and could serve as indicators for an efficient quantification of SOC. These indicators should enable both an estimation of actual SOC storage as well as a prediction of the SOC storage potential, which is an important aspect in land use and management planning. There are many environmental
conditions that affect SOC storage at different spatial scales. We provide a thorough overview of factors from micro-scales (particles to pedons) to the global scale and discuss their suitability as indicators for SOC storage: clay mineralogy, specific surface area, metal oxides, Ca and Mg cations, microorganisms, soil fauna, aggregation,
texture, soil type, natural vegetation, land use and management, topography, parent material and climate. As a result, we propose a set of indicators that allow for time- and cost-efficient estimates of actual and potential SOC storage from the local to the regional and subcontinental scale. As a key element, the fine mineral fraction was identified to determine SOC stabilization in most soils. The quantification of SOC can be further refined by including climatic proxies, particularly elevation, as well as information on land use, soil management and vegetation characteristics. To enhance its indicative power towards land management effects, further “functional soil characteristics”, particularly soil structural properties and changes in the soil microbial biomass pool should be included in this indicator system. The proposed system offers the potential to efficiently estimate the SOC storage capacity by means of simplified measures, such as soil fractionation procedures or infrared spectroscopic approaches.
Over the past five decades, the delivery of global Ecosystem Services (ES) has diminished and this has been driven partly by anthropogenic activities. Agro-ecosystems cover almost 40% of the terrestrial surface on Earth, and have been considered as one of the most significant ecological experiments with a potential to both contribute to and mitigate global ES loss. In the present study, six different ES (food and fodder production, carbon sequestration, biological pest control, soil water storage, nitrogen regulation and soil formation) were quantified in various organic farming systems and the hypothesis that there is a link between these ES and C:N, C:O and H:O stoichiometric ratios in farming systems was experimentally tested. The results show that different ES are correlated with the stoichiometric ratios to different extents. There are significant positive linear correlations between C:N stoichiometric ratios and all measured ES in the investigated organic farming systems, while not all the ES are correlated with the C:O and H:O ratios. This study has expanded the horizons of stoichiometry by linking a fundamental chemical property of molecules with an emergent property of organic farming systems, namely their ecosystem service provision.
Fine roots (diameter ≤2 mm) contribute significantly to the forest carbon cycle and are essential for resource acquisition from the soil. We conducted a study to assess the relationships between tree and ground vegetation
fine root biomass and tree species diversity (monocultures compared to 2–5 species mixtures), conifer proportion and other site factors (stand basal area, soil carbon stocks and C:N ratio) in the six major European forest types, boreal forest in Finland, temperate forests in Poland, Germany and Romania, thermophilous deciduous forests in Italy, and Mediterranean forests in Spain. We sampled the fine roots of trees and ground vegetation to the depth of 20 cm in the mineral soil and allocated the fine root biomass to individual tree species using near-infrared reflectance spectroscopy (NIRS). We did not find any general positive effects of tree species diversity on the fine root biomass of trees or ground vegetation across the forest types and tree species combinations. However, our results suggest that tree fine root biomass increases with tree species diversity in pure broadleaf forests, but not in pure conifer forests. Species diversity explained 7% of the variation in tree fine root biomass in the broadleaf stands. The narrow tree species diversity gradient (1–2 species) in the conifer forests compared to the broadleaf forests (1−4) may have decreased the probability of conifer species combinations with below-ground functional traits conducive to over-yielding. Some evidence of diversity-mediated changes in the vertical rooting patterns of broadleaf trees and ground vegetation were found within the entire organic and 0–20 cm mineral soil layer although the weighted mean depth of fine root biomass was not affected. Negative diversity effects were found in the organic layer and positive diversity effects in the 0–10 cm mineral soil layer for broadleaf tree fine root biomass. Diversity effects were negative for ground vegetation fine root biomass in the 0–10 cm mineral soil layer. There was a general positive effect of conifer proportion on total fine root biomass in the organic layer, but not in the mineral soil layers. In general conifer proportion and site factors explained more of the variation in tree fine root biomass than tree species diversity. More research covering the annual variation in fine root biomass and deeper soil layers is needed before recommending managing species-rich forest for increasing below-ground biomass and carbon pools.
Tree litter decomposition on disturbed post-mining sites has been mainly studied within successional gradients, whereas almost no results were shown from afforested spoil heaps. Litterfall and its decomposition rate are considered the most important ecological processes for soil restoration during stand development on such initial forest habitats. These processes allow development of a functional ecosystem and productive forest stands. Moreover, the pedogenesis process on such “soilless”’ habitats can be significantly improved and accelerated by tree species selection during afforestation.
The main aim of the study was to determine litter decomposition rates of nine tree species used for afforestation of a lignite mine spoil heap. We assumed that leaf litter decomposition rates would differ among tree species studied and that the site conditions would significantly influence this process.
Our study was conducted on the spoil heap of the lignite open cast mine in Bełchatów, central Poland. We studied leaf litter decomposition of Alnus glutinosa, Betula pendula, Pinus sylvestris, Quercus robur, Q. rubra and Robinia pseudoacacia in pure stands of these species (home stands), and litter decomposition of Acer pseudoplatanus, A. glutinosa, Fagus sylvatica, Prunus serotina, Q. rubra, and R. pseudoacacia in Scots pine stands. We used the litterbag method. The experiments lasted for three years and the samples were collected every three months.
Leaf litter decomposition calculated for home stands after three years of decomposition was 94.4% of the initial leaf mass for A. glutinosa, 70.9% for R. pseudoacacia, 70.1% for P. sylvestris, 68.3% for B. pendula, 66.9% for Q. rubra and 61.5% for Q. robur. In Scots pine stands, after three years of the experiment, 92.3% of the initial leaf mass decomposed for P. serotina, 85.7% for A. glutinosa, 83.5% for A. pseudoplatanus, 65.2% for R. pseudoacacia, 50.9% for Q. rubra and 40.1% for F. sylvatica. A. glutinosa, R. pseudoacacia and Q. rubra leaves decomposed significantly faster in home stands than in Scots pine stands. Site aspect significantly influenced litter decomposition of the species studied, with higher rates mostly on the western slope.
Our study revealed that the decision on tree species used for afforestation might shorten the period needed for soil restoration and achievement of sustainability of novel ecosystems. Proper selection of main and admixture tree species for afforestation of the post-mining sites might reduce the renewal period of the soilless and newly created habitats, which may provide noticeable ecological and economical effects during stand management.
full paper can be downloaded here: https://authors.elsevier.com/c/1Vo3T3JGmQvIL3
Many ecosystem processes in forest ecosystems are influenced by tree species richness and tree functional diversity (FD). Several studies, mainly in grasslands, have already underlined a positive effect of plant species
richness on soil carbon (C) storage, but evidence for such a relationship for forests is scarce and not much is
known about the role of FD. In this study, we investigated the impact of trees with contrasting functional litter
traits on soil C and nitrogen (N) storage in a forest plantation on a former grassland. In addition, we also
investigated the impact of increasing FD on six different soil enzymes, considered as proximate agents of potential microbial mineralization processes. We found synergistic effects of tree mixtures on soil enzymatic activities at the highest FD levels and an overall increase in soil mineralization potential with FD within tree
mixtures. Moreover, we registered an overall decrease in soil C and N stocks 12 years after tree planting. Our
results suggest that the selection of tree species and mixtures based on functional traits influencing soil C storage is fundamental for the success of climate change mitigation strategies employing tree plantations on abandoned pastures or grasslands.
Studies of the decomposition, transformation and stabilization of soil organic matter (SOM) have dramatically increased in recent years owing to growing interest in studying the global carbon (C) cycle as it pertains to climate change. While it is readily accepted that the magnitude of the organic C reservoir in soils depends upon microbial involvement, as soil C dynamics are ultimately the consequence of microbial growth and activity, it remains largely unknown how these microorganism-mediated processes lead to soil C stabilization. Here, we define two pathways—ex vivo modification and in vivo turnover—which jointly explain soil C dynamics driven by microbial catabolism and/or anabolism. Accordingly, we use the conceptual framework of the soil ‘microbial carbon pump’ (MCP) to demonstrate how microorganisms are an active player in soil C storage. The MCP couples microbial production of a set of organic compounds to their further stabilization, which we define as the entombing effect. This integration captures the cumulative long-term legacy of microbial assimilation on SOM formation, with mechanisms (whether via physical protection or a lack of activation energy due to chemical composition) that ultimately enable the entombment of microbial-derived C in soils. We propose a need for increased efforts and seek to inspire new studies that utilize the soil MCP as a conceptual guideline for improving mechanistic understandings of the contributions of soil C dynamics to the responses of the terrestrial C cycle under global change.
Respiration is a simple method to describe the overall condition of soils. Most usually, it is suggested CO2 evaluation after 7 days. Our study compared the relationship between soil respiration measured at different periods of times (one and eight weeks and cumulative respiration), as well as basic soil properties and the quantification microbial and fungal communities and their activity. We located our research on three sites with post-mine soils in Poland afforested by pine, birch and oak. Each site had soil derived from different substrate. The samples were taken from the fermentation layer (Oe) and mineral soil layer (A – at 0–5 cm beneath the Oe). In both studied layers basic soil properties such as: pH and C,N contents were analysed while soil texture was determined in A layer only. Microbial respiration was measured after each week of the eighth weeks incubation period. Microbial analyses included determination of ergosterol and phospholipid fatty acid (PLFA) profiles. Microbial respiration was nearly two time higher after the first week than the eighth week in both soil layers. Forest type and soil substrate had an effect on respiration in the Oe layer at both measurement times. Respiration in the A layer measured in the eighth week was affected only by the soil substrate. In the Oe layer, fungal decomposers play a lead role, and their activity was affected both by tree species and soil substrate. In the A layer, however, bacteria activity was predominated and was affected by tree species and substrate composition.
Globally, forests represent highly productive ecosystems that act as carbon sinks where soil organic matter is formed from residuals after biomass decomposition as well as from rhizodeposited carbon. Forests exhibit a high level of spatial heterogeneity and the importance of trees, the dominant primary producers, for their structure and functioning. Fungi, bacteria and archaea inhabit various forest habitats: foliage, the wood of living trees, the bark surface, ground vegetation, roots and the rhizosphere, litter, soil, deadwood, rock surfaces, invertebrates, wetlands or the atmosphere, each of which has its own specific features, such as nutrient availability or temporal dynamicy and specific drivers that affect microbial abundance, the level of dominance of bacteria or fungi as well as the composition of their communities. However, several microorganisms, and in particular fungi, inhabit or even connect multiple habitats, and most ecosystem processes affect multiple habitats. Forests are dynamic on a broad temporal scale with processes ranging from short-term events over seasonal ecosystem dynamics to long-term stand development after disturbances such as fires or insect outbreaks. The understanding of these processes can be only achieved by the exploration of the complex 'ecosystem microbiome' and its functioning using focused, integrative microbiological and ecological research performed across multiple habitats.
The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent 'humic substances' in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon-climate interactions and land management.
Microorganisms play major roles in transformations of inorganic nutrients such as phosphorus, sulfur, iron, and trace elements in terrestrial systems. The bacteria, fungi, and archaea that mediate these cycles inhabit a wide range of environmental niches in soils, varying from fully aerobic in aerated surface soils to entirely anaerobic within soil aggregates or in sediments. Important nutrient transformations include mobilization of nutrients from primary minerals through weathering, immobilization of nutrients into soil organic matter, and their mineralization from organic matter to liberate nutrients for assimilation or dissimilation as required. Mineralization mechanisms for P and S are often hydrolytic in nature, whereas key processes for metal solubilization involve chelation and redox transformations. Biological nutrient cycles for different elements are often closely integrated with each other. We present examples of these interactions in wetlands with varying water levels and during early soil development on a glacier forefield.
Tree species may affect diversity of soil microbial communities in afforested post-mining barrens. The objective of this study was to compare community level physiological profiles (CLPPs) of microbial communities in O horizons and uppermost mineral layers of mine soils under the pine (Pinus sylvestris), birch (Betula pendula), larch (Larix decidua), alder (Alnus glutinosa), and mixed pine-alder and birch-alder forest stands. The physiological abilities of soil microbial communities were studied using the Biolog® test. Physiological diversity was calculated as Shannon’s index (H’) based on the Biolog® data. There were significant vegetation-dependent differences in CLPPs with the larch and birch stands supporting microbial communities with distinct physiological profiles. The soil microbial communities under these stands used less efficiently carbohydrates and were characterized by lower CH/AA ratio. The differences in CLPPs were limited to O horizon, in the mineral soil the effect of tree species was much less pronounced. Admixture of alders to birch and pine stands did not result in consistent increase of physiological diversity of soil microbial communities. However, the microbial communities under pure larch stand were significantly less physiologically diverse which may suggest worse functioning of microbial communities under pure larch plantations.
A meta-analysis using 77 studies from 28 countries was performed to assess the effect of hardwood vs. conifer overstory on soil organic C (SOC) storage in forest floor (FF), mineral soil, and whole soil (FF + mineral soil). Overall, FF stocks were 38% higher under conifers, mineral SOC stocks were similar, and whole soil SOC was 14% higher under conifers. An analysis with six of the seven most reported tree genera reaffirmed higher FF and whole soil C stocks under conifer stands. Analysis with all seven of the genera showed more pronounced variability in mineral SOC results compared with the overall results. Eucalyptus was the only hardwood that stored significantly (17%) more SOC in the mineral soil than adjacent conifers. Picea was the only conifer that stored significantly (7%) more SOC in the mineral soil than hardwoods. Differences in FF SOC stocks had a limited predictive power in explaining the variability of mineral SOC stock differences, suggesting that they are not very closely linked with regard to SOC storage. Only when comparing FF SOC stocks among genera did precipitation, age difference, soil texture, and previous land use moderate SOC storage differences between conifers and hardwoods. In other cases, neither climate nor soil variables could explain differences between SOC stocks. Our findings suggest that using plant-trait-driven vegetation categories may be a more descriptive way of detecting vegetation effects on SOC. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved.
Since the publication of the 2nd edition, there have been substantial developments in the field of litter decomposition. This fully revised and updated 3rd edition of Plant Litter reflects and discusses new findings and re-evaluates earlier ones in light of recent research and with regard to current areas of investigation. The availability of several long-term studies allows a more in-depth approach to decomposition patterns and to the later stages of decomposition, as well as to humus formation and accumulation. The latest information focuses on three fields: - the effects of manganese on decomposition and possibly on carbon sequestration, - new findings on decomposition dynamics, and - the new analytical technique using 13C-NMR. © 2014 Springer-Verlag Berlin Heidelberg. All rights are reserved.
Differences in soil nutrients beneath different tree species are often attributed to the impacts of species-level patterns of nutrient uptake and litter chemistry. However, in naturally established forests it is difficult to isolate tree species' influence on soil development from differences in underlying soil properties that can affect tree species establishment. To discern the impacts of tree species on soil properties, we investigated how Norway spruce (Picea abies (L.) H. Karst.), red oak (Quercus rubra L.), and sugar maple (Acer saccharum Marshall) influence the distribution of carbon, nitrogen, and calcium in a 67-year-old common garden. We expected these species would produce foliar litter with contrasting chemistry, resulting in corresponding variation in organic matter (OM) turnover and nutrient accumulation in soils. Instead, we found that forest floor mean residence time correlated negatively with earthworm density and did not correlate with any measurement of litter chemistry. Red oak exhibited the fastest OM turnover and highest earthworm densities and Norway spruce showed the greatest OM accumulation and fewest earthworms. These findings suggest that future changes in earthworm invasion and forest tree species composition may have strong implications for ecosystem nutrient cycling and retention.
The C:N ratio is considered as an indicator of nitrate leaching in response to high atmospheric nitrogen (N) deposition. However, the C:N ratio is influenced by a multitude of other site-related factors. This study aimed to unravel the factors determining C:N ratios of forest floor, mineral soil and peat top soils in more than 4000 plots of the ICP Forests large-scale monitoring network. The first objective was to quantify forest floor, mineral and peat soil C:N ratios across European forests. Secondly we determined the main factors explaining this C:N ratio using a boosted regression tree analysis (BRT), including fifteen site and environmental variables.
Processes involved in the structuring of forest communities include: (1) ecological sorting, where species poorly suited to local conditions are subject to environmental filtering and competitive displacement; (2) disturbance, resulting in stochastic removal of individuals and reinitiating successional regimes and (3) dispersal limitation, inhibiting the infiltration of species into preferred sites. Temporal dynamics in these processes lead to difficulty inferring causal landscape–biota correlations. Complicating factors include potential for ontogenetic variation in habitat preferences among age classes, and inherent ambiguity regarding severity and coverage of historical disturbance events. Sorting species into age groups can provide relevant temporal information. Fundy National Park is a northern, mixed-temperate forest in Atlantic Canada (Acadian forest type), which was pervasively altered upon European settlement. Species frequency data for three tree age classes (saplings, juveniles and adults) in permanent sample plots (400 m2, n = 33) were compared to environmental data, including soil chemistry, understory light conditions, physiography and disturbance history using ordination and randomization techniques. Abiotic and disturbance-related predictors of species distributions differed among life stages. Specifically, in the adult stage, stand age was a critical predictor of distribution, whereas in younger age classes environmental variables such as nutrient availability and soil moisture and drainage were key drivers of distribution. It is concluded that older populations were increasingly less constrained by environmental conditions, suggesting that adult populations bear the legacy of stochastic landscape alteration, thus appearing randomly distributed along environmental gradients. As younger populations gradually expand in distribution, they are filtered into preferred conditions by ecological sorting. These findings indicate the importance of considering age-class effects and site history in further assessments of interactions between landscapes and flora.
The aim of this work was to quantify the effects of vegetation on the activity of extracellular enzymes in the litter and soil. To achieve this, we investigated a set of post-mining sites in a brown-coal mine deposit area near Sokolov, Czech Republic. The sites were 22–33 years old and had been established on the same initial substrate by planting with six tree genera or leaving for spontaneous revegetation, with four replicate sites per vegetation type. The activity of extracellular hydrolytic and oxidative enzymes and the microbial community composition of the litter and topsoil were compared in the spring, summer and autumn using the dominant tree, pH, soil nutrient content and soil moisture as the explanatory variables. Sites under individual trees exhibited significant differences in the chemical properties of both the litter and soil, and the tree effect was identified as the most important factor affecting the activity of extracellular enzymes either directly or in the interaction with seasonal effects, although not all pairs of tree species were significantly different from each other. Seasonal effects on enzyme activity were only important in the litter. The effects of dominant trees and of seasons contributed equally to the variation in the microbial community composition at individual sites. Only a minor part of the tree effect could be explained by differences in the litter or soil chemistry. Among the chemical variables, the N content most affected the microbial biomass content, increasing fungal (but not bacterial) biomass in the litter and bacterial (but not fungal) biomass in the soil. The results indicate that other factors, such as nutrient quality or the specific association of microorganisms with rhizospheres of different trees or the understory, are likely important mediators of the vegetation effects. When comparing the revegetated sites with sites under spontaneous succession, the enzyme activities and microbial biomass were similar except for the sites revegetated with Alnus which may indicate similar rates of soil development at revegetated and succession sites. Spontaneous succession in temperate Europe may thus be a suitable option for land restoration.
Information on tree species effects on soil organic carbon (SOC) stocks is scattered and there have been few attempts to synthesize results for forest floor and mineral soil C pools. We reviewed and synthesized current knowledge of tree species effects on SOC stocks in temperate and boreal forests based on common garden, retrospective paired stand and retrospective single-tree studies. There was evidence of consistent tree species effects on SOC stocks. Effects were clearest for forest floor C stocks (23 of 24 studies) with consistent differences for tree genera common to European and North American temperate and boreal forests. Support for generalization of tree species effects on mineral soil C stocks was more limited, but significant effects were found in 13 of 22 studies that measured mineral soil C.
a b s t r a c t The effects of tree species differing in foliage and litter chemistry on the chemical, micro-morphological, and biological properties of soil were studied on post-mining sites afforested with one of six tree species (spruce, pine, larch, oak, lime, and alder) and also on sites left to natural succession (dominated by wil-low). The sites were located on a large colliery spoil heap that had been produced by the mining of coal in alkaline tertiary clays near the city of Sokolov, Czech Republic. Because no topsoil had been applied to the sites, soil development resulted from in situ interactions among the deposited overburden (spoil), trees, and soil biota. Soil formation differed markedly among sites afforested with different tree species. On sites with trees producing litter with a low C/N ratio (the deciduous species), the organic Oe layer was narrow or absent and a thick organomineral A layer was evident. On sites with trees producing litter with a high C/N ratio (the evergreen species), in contrast, a thick Oe layer and a thin A layer were evident. Besides C/N ratio, earthworm abundance and earthworm bioturbation activity (measured as the amount of earthworm casts in the topsoil) were the strongest predictors of A layer thickness and C accumulation in the mineral topsoil. Sites with higher C accumulation in mineral soil had higher microbial biomass and lower microbial respiration, which may have contributed to the higher C storage. The gradient of biotur-bation was correlated with changes in the composition of the bacterial community and other soil biota, but partial correlation showed that the effects of litter quality and bioturbation were largely independent. Overall, the results indicate that the effect of tree species on soil development is substantially mediated by soil fauna activity and especially by earthworm bioturbation. Ó 2013 Elsevier B.V. All rights reserved.
Sequestering soil carbon (C) relies upon the availability of stabilising elements, nitrogen (N), phosphorus (P) and sulphur (S) which are known to be essential components of the stable organic C pool (Himes, 1998; Lal, 2008). The C:N:P:S ratios were investigated for a series of soils to test the hypothesis that the stable portion of the soil organic material (humus) has constant ratios of C:N:P:S. Constant ratios, if established, would provide an excellent tool to evaluate the feasibility, cost and strategies to sequester soil C in terrestrial ecosystems. Freshly-collected Australian soils cited in the literature were analysed for total C, N, P, organic P (OP) and S, and the ratios were compared with values for soils from numerous locations around the world, hereafter known as the International soils.
The knowledge of tree species effects on soil C and N pools is scarce, particularly for European deciduous tree species. We studied forest floor and mineral soil carbon and nitrogen under six common European tree species in a common garden design replicated at six sites in Denmark. Three decades after planting the six tree species had different profiles in terms of litterfall, forest floor and mineral soil C and N attributes. Three groups were identified: (1) ash, maple and lime, (2) beech and oak, and (3) spruce. There were significant differences in forest floor and soil C and N contents and ON ratios, also among the five deciduous tree species. The influence of tree species was most pronounced in the forest floor, where C and N contents increased in the order ash = lime = maple < oak = beech << spruce. Tree species influenced mineral soil only in some of the sampled soil layers within 30 cm depth. Species with low forest floor C and N content had more C and N in the mineral soil. This opposite trend probably offset the differences in forest floor C and N with no significant difference between tree species in C and N contents of the whole soil profile. The effect of tree species on forest floor C and N content was primarily attributed to large differences in turnover rates as indicated by fractional annual loss of forest floor C and N. The C/N ratio of foliar litterfall was a good indicator of forest floor C and N contents, fractional annual loss of forest floor C and N, and mineral soil N status. Forest floor and litterfall C/N ratios were not related, whereas the ON ratio of mineral soil (0-30 cm) better indicated N status under deciduous species on rich soil. The results suggest that European deciduous tree species differ in C and N sequestration rates within forest floor and mineral soil, respectively, but there is little evidence of major differences in the combined forest floor and mineral soil after three decades.
Canopy litterfall is a significant pathway for return of nutrients and carbon (C) to the soil in forest ecosystems. Litterfall was studied in five even-aged stands of Norway spruce, Sitka spruce, Douglas-fir, European beech and common oak at three different locations in Denmark; two sandy sites, Ulborg and Lindet in Jutland, and one loamy site, Frederiksborg on Zealand. Litterfall was collected during three years from 1994 to 1996 in all five species and during six years from 1994 to 1999 in Norway spruce, Sitka spruce and European beech. The average total litterfall was in the range of 3200-3700 kg ha(-1) yr(-1) and did not differ significantly among tree species. There were no significant differences in total litterfall among sites during the short period, but during the longer period the richer site Frederiksborg had significantly higher total and foliar litterfall amounts compared to the more nutrient-poor sites Lindet and Ulborg. There were close relationships between foliar and total litterfall Suggesting that foliar litterfall can be reliably estimated from total litterfall. Beech and oak bud scale litter was significantly related to foliar litterfall. The amount of branch and twig litter was significantly higher in oak than in other tree species. The average foliar litterfall was well related to the annual volume increment. The relationship differed markedly from previously reported relationships based on global litterfall data suggesting that such relationships are better evaluated at the regional level. Nutrient concentrations and fluxes in foliar litterfall were not significantly different among the five tree species. However. there was a significant effect of site on most nutrient concentrations of the three litterfall fractions, and foliar fluxes of P. Ca and Mn were all significantly highest at Frederiksborg and lowest at Ulborg. The similarity in litterfall inputs to the forest floor under these five tree species suggested that previous reports of large variability in forest floor accumulation should primarily be attributed to differences in litter decomposition.
We reviewed the experimental evidence for long-term carbon (C) sequestration in soils as consequence of specific forest management strategies. Utilization of terrestrial C sinks alleviates the burden of countries which are committed to reducing their greenhouse gas emissions. Land-use changes such as those which result from afforestation and management of fast-growing tree species, have an immediate effect on the regional rate of C sequestration by incorporating carbon dioxide (CO(2)) in plant biomass. The potential for such practices is limited in Europe by environmental and political constraints. The management of existing forests can also increase C sequestration, but earlier reviews found conflicting evidence regarding the effects of forest management on soil C pools. We analyzed the effects of harvesting, thinning, fertilization application, drainage, tree species selection, and control of natural disturbances on soil C dynamics. We focused on factors that affect the C input to the soil and the C release via decomposition of soil organic matter (SOM). The differentiation of SOM into labile and stable soil C fractions is important. There is ample evidence about the effects of management on the amount of C in the organic layers of the forest floor, but much less information about measurable effects of management on stable C pools in the mineral soil. The C storage capacity of the stable pool can be enhanced by increasing the productivity of the forest and thereby increasing the C input to the soil. Minimizing the disturbances in the stand structure and soil reduces the risk of unintended C losses. The establishment of mixed species forests increases the stability of the forest and can avoid high rates of SOM decomposition. The rate of C accumulation and its distribution within the soil profile differs between tree species. Differences in the stability of SOM as a direct species effect have not yet been reported.
We studied the soil properties of 18-year-old plantations beneath the crowns of the native sessile oak (Quercus petraea) and of the introduced red oak (Quercus rubra) growing on reclaimed lignite open-cast mines. The soil properties of both plantations, which are growing on either highly fertile (loess deposits, silty loam) or on low fertile (mixture of loess and sand deposits, clayed sand) soil, were measured and compared with values taken from 2-year-old Quercus robur plantations.In plantations of Q. petraeawe generally found higher values of total carbon (Corg) and total nitrogen (Ntot) in the upper soil, although the amount of organic matter in the O-horizon did not significantly differ. Soils of Q. petraea plantations also exhibited higher values for microbial and faunal life. For example, microbial activity, the respiratory quotient (qCO2) and C-mineralization were about twice as high as for the Q. rubra plantations. Collembola and mites (Oribatei), both belonging to the soil mesofauna, reached higher densities in the Q. petraea plantations.When growing on highly fertile soils, the amount of soil nutrients (K+, Ca2+, Mg2+, and PO43−P) did not differ between the two plantations. However, when oak trees grew on the less-fertile soil, the amount of soil nutrients was significantly lower beneath red oak. The amount of soil nutrients beneath red oak was even lower than beneath 2-year-old Q. robur plantations; the soil properties of which are almost at the beginning stage of succession. The results suggest that nutrient depletion beneath red oak when compared to sessile oak is caused both by increased immobilization into woody biomass, and by increased recalcitrance of organic matter.
The decomposition and transformation of above- and below-ground plant detritus (litter) is the main process by which soil organic matter (SOM) is formed. Yet, research on litter decay and SOM formation has been largely uncoupled, failing to provide an effective nexus between these two fundamental processes for carbon (C) and nitrogen (N) cycling and storage. We present the current understanding of the importance of microbial substrate use efficiency and C and N allocation in controlling the proportion of plant-derived C and N that is incorporated into SOM, and of soil matrix interactions in controlling SOM stabilization. We synthesize this understanding into the Microbial Efficiency-Matrix Stabilization (MEMS) framework. This framework leads to the hypothesis that labile plant constituents are the dominant source of microbial products, relative to input rates, because they are utilized more efficiently by microbes. These microbial products of decomposition would thus become the main precursors of stable SOM by promoting aggregation and through strong chemical bonding to the mineral soil matrix.