Storage and Drivers of Organic Carbon in Forest Soils of Southeast Germany (Bavaria) - Implications for Carbon Sequestration. Wiesmeier, M., Prietzel, J., Barthold, F., Spörlein, P., Geuß, U., Hangen, E., Reischl, A., Schilling, B., von Lützow, M., & Kögel-Knabner, I. 295:162–172.
Storage and Drivers of Organic Carbon in Forest Soils of Southeast Germany (Bavaria) - Implications for Carbon Sequestration [link]Paper  doi  abstract   bibtex   
[Abstract] Temperate forest soils of central Europe are regarded as important pools for soil organic carbon (SOC) and thought to have a high potential for carbon (C) sequestration. However, comprehensive data on total SOC storage, particularly under different forest types, and its drivers is limited. In this study, we analyzed a forest data set of 596 completely sampled soil profiles down to the parent material or to a depth of 1 m within Bavaria in southeast Germany in order to determine representative SOC stocks under different forest types in central Europe and the impact of different environmental parameters. We calculated a total median SOC stock of 9.8 kg m-2 which is considerably lower compared with many other inventories within central Europe that used modelled instead of measured soil properties. Statistical analyses revealed climate as controlling parameter for the storage of SOC with increasing stocks in cool, humid mountainous regions and a strong decrease in areas with higher temperatures. No significant differences of total SOC storage were found between broadleaf, coniferous and mixed forests. However, coniferous forests stored around 35\,% of total SOC in the labile organic layer that is prone to human disturbance, forest fires and rising temperatures. In contrast, mixed and broadleaf forests stored the major part of SOC in the mineral soil. Moreover, these two forest types showed unchanged or even slightly increased mineral SOC stocks with higher temperatures, whereas SOC stocks in mineral soils under coniferous forest were distinctly lower. We conclude that mixed and broadleaf forests are more advantageous for C sequestration than coniferous forests. An intensified incorporation of broadleaf species in extent coniferous forests of Bavaria would prevent substantial SOC losses as a result of rising temperatures in the course of climate change. [Highlights] [::] SOC storage and its drivers of different forest types in Bavaria were investigated. [::] No SOC differences were found between broadleaf, coniferous and mixed forests. [::] Temperature and precipitation controlled total SOC storage in forests. [::] No decrease of mineral SOC of broadleaf/mixed forests in regions with high temperatures. [::] Incorporation of broadleaf species to prevent future SOC losses of coniferous forests. [Excerpt:Driving factors of SOC storage in forest soils] The combined approach of regression, principal component and multiple linear regression analyses clearly showed that the factor climate, indicated by high loadings of the climate-related parameters temperature, precipitation and elevation, mainly controlled the total storage of SOC in forest soils of Bavaria (Table 2 and Table 3). The climate-effect on the storage of SOC has two components. First, the amount of precipitation controls the above- and belowground net primary productivity of trees and thus the input of OM into the soil. High amounts of precipitation also lead to acidification of forest soils that is associated with a lower decomposition of SOM (Meier and Leuschner, 2010). Further, humid climatic conditions are associated with a profound weathering of the parent material and thus with the formation of OC-stabilizing minerals [...] [\n] [...] [\n] The temperature is the second climate-related component influencing SOC storage. Generally, the microbial decomposition of SOM is temperature-dependent as its complex molecular attributes have a high intrinsic temperature sensitivity (Davidson and Janssens, 2006, von Lützow and Kögel-Knabner, 2009 and Conant et al., 2011). Although this relationship is governed by multiple constraints (stability of SOM, substrate availability, physiology of the soil microflora and physicochemical controls as pH, water, oxygen and nutrients), numerous in situ observations and laboratory experiments revealed decreasing amounts of SOM in forest soils due to increased soil respiration with rising temperatures (e.g. Jobbagy and Jackson, 2000, Lorenz and Lal, 2010, Meier and Leuschner, 2010, Tyrrell et al., 2012 and Vesterdal et al., 2012) [...] [\n] [...] [\n] Besides climate as the dominant driver for the storage of SOC in forest soils, the factor soil moisture, indicated by the TWI and a negative correlation with slope, was detected (Table 2 and Table 3). Large TWI values are usually found in lower positions of a landscape with large contributing areas and indicate increased likelihood of saturated conditions (Sorensen et al., 2006 and Grabs et al., 2009) due to topographic position. The reduced mineralization of OM in groundwater soils in these positions is responsible for a strong accumulation of SOC stocks in forest soils of Bavaria as it was also indicated by high amounts of SOC in alluvial soils (Fig. 2). In a related study, we detected TWI as most important parameter controlling SOC and N storage in agricultural soils of Bavaria [...] [\n] [...] [Conclusions] Total SOC stocks in forest soils of Bavaria were calculated to be 9.8 kg m-2, what is considerably lower than other estimations in central Europe. The application of PTFs as well as sampling close to trunks is probably responsible for overestimations in several SOC inventories. We recommend a sampling design that includes several locations with various distances from trunks and measurement of all soil parameters down to the parent material for an accurate determination of forest SOC stocks. The storage of SOC in forest soils was mainly driven by climate with higher stocks under cool, humid regimes and lower stocks in warmer, drier regions. This highlights the importance of mountainous forest soils in the Alps and low mountain ranges of Bavaria as a major C pool. Strong correlations with climate were superimposed in the topsoil by clay content and tree species composition indicated by pH values. No significant differences of entire SOC storage were detected between broadleaf, mixed and coniferous forests. However, coniferous forests accumulated around 35\,% of total SOC in the unprotected organic layer that is prone to human disturbance, forest fires and rising temperatures. In contrast, mixed and particularly broadleaf forests stored significantly higher amounts of SOC in the mineral soil. Moreover, mineral SOC stocks of mixed and broadleaf forests remained unchanged or were even slightly higher in regions with higher temperatures, demonstrating their low actual temperature sensitivity, whereas coniferous mineral SOC stocks were continuously lower. Thus, we conclude that an incorporation of broadleaf species in expanded coniferous forests of Bavaria associated with a translocation of SOC from the forest floor into the mineral soil would promote C sequestration in the long-term, particularly under increased temperatures.
@article{wiesmeierStorageDriversOrganic2013,
  title = {Storage and Drivers of Organic Carbon in Forest Soils of Southeast {{Germany}} ({{Bavaria}}) - {{Implications}} for Carbon Sequestration},
  author = {Wiesmeier, Martin and Prietzel, Jörg and Barthold, Frauke and Spörlein, Peter and Geuß, Uwe and Hangen, Edzard and Reischl, Arthur and Schilling, Bernd and von Lützow, Margit and Kögel-Knabner, Ingrid},
  date = {2013-05},
  journaltitle = {Forest Ecology and Management},
  volume = {295},
  pages = {162--172},
  issn = {0378-1127},
  doi = {10.1016/j.foreco.2013.01.025},
  url = {https://doi.org/10.1016/j.foreco.2013.01.025},
  abstract = {[Abstract]

Temperate forest soils of central Europe are regarded as important pools for soil organic carbon (SOC) and thought to have a high potential for carbon (C) sequestration. However, comprehensive data on total SOC storage, particularly under different forest types, and its drivers is limited. In this study, we analyzed a forest data set of 596 completely sampled soil profiles down to the parent material or to a depth of 1 m within Bavaria in southeast Germany in order to determine representative SOC stocks under different forest types in central Europe and the impact of different environmental parameters. We calculated a total median SOC stock of 9.8 kg m-2 which is considerably lower compared with many other inventories within central Europe that used modelled instead of measured soil properties. Statistical analyses revealed climate as controlling parameter for the storage of SOC with increasing stocks in cool, humid mountainous regions and a strong decrease in areas with higher temperatures. No significant differences of total SOC storage were found between broadleaf, coniferous and mixed forests. However, coniferous forests stored around 35\,\% of total SOC in the labile organic layer that is prone to human disturbance, forest fires and rising temperatures. In contrast, mixed and broadleaf forests stored the major part of SOC in the mineral soil. Moreover, these two forest types showed unchanged or even slightly increased mineral SOC stocks with higher temperatures, whereas SOC stocks in mineral soils under coniferous forest were distinctly lower. We conclude that mixed and broadleaf forests are more advantageous for C sequestration than coniferous forests. An intensified incorporation of broadleaf species in extent coniferous forests of Bavaria would prevent substantial SOC losses as a result of rising temperatures in the course of climate change.

[Highlights]

[::] SOC storage and its drivers of different forest types in Bavaria were investigated. [::] No SOC differences were found between broadleaf, coniferous and mixed forests. [::] Temperature and precipitation controlled total SOC storage in forests. [::] No decrease of mineral SOC of broadleaf/mixed forests in regions with high temperatures. [::] Incorporation of broadleaf species to prevent future SOC losses of coniferous forests.

[Excerpt:Driving factors of SOC storage in forest soils]

The combined approach of regression, principal component and multiple linear regression analyses clearly showed that the factor climate, indicated by high loadings of the climate-related parameters temperature, precipitation and elevation, mainly controlled the total storage of SOC in forest soils of Bavaria (Table 2 and Table 3). The climate-effect on the storage of SOC has two components. First, the amount of precipitation controls the above- and belowground net primary productivity of trees and thus the input of OM into the soil. High amounts of precipitation also lead to acidification of forest soils that is associated with a lower decomposition of SOM (Meier and Leuschner, 2010). Further, humid climatic conditions are associated with a profound weathering of the parent material and thus with the formation of OC-stabilizing minerals [...]

[\textbackslash n] [...] [\textbackslash n] The temperature is the second climate-related component influencing SOC storage. Generally, the microbial decomposition of SOM is temperature-dependent as its complex molecular attributes have a high intrinsic temperature sensitivity (Davidson and Janssens, 2006, von Lützow and Kögel-Knabner, 2009 and Conant et al., 2011). Although this relationship is governed by multiple constraints (stability of SOM, substrate availability, physiology of the soil microflora and physicochemical controls as pH, water, oxygen and nutrients), numerous in situ observations and laboratory experiments revealed decreasing amounts of SOM in forest soils due to increased soil respiration with rising temperatures (e.g. Jobbagy and Jackson, 2000, Lorenz and Lal, 2010, Meier and Leuschner, 2010, Tyrrell et al., 2012 and Vesterdal et al., 2012) [...]

[\textbackslash n] [...]

[\textbackslash n] Besides climate as the dominant driver for the storage of SOC in forest soils, the factor soil moisture, indicated by the TWI and a negative correlation with slope, was detected (Table 2 and Table 3). Large TWI values are usually found in lower positions of a landscape with large contributing areas and indicate increased likelihood of saturated conditions (Sorensen et al., 2006 and Grabs et al., 2009) due to topographic position. The reduced mineralization of OM in groundwater soils in these positions is responsible for a strong accumulation of SOC stocks in forest soils of Bavaria as it was also indicated by high amounts of SOC in alluvial soils (Fig. 2). In a related study, we detected TWI as most important parameter controlling SOC and N storage in agricultural soils of Bavaria [...]

[\textbackslash n] [...]

[Conclusions]

Total SOC stocks in forest soils of Bavaria were calculated to be 9.8 kg m-2, what is considerably lower than other estimations in central Europe. The application of PTFs as well as sampling close to trunks is probably responsible for overestimations in several SOC inventories. We recommend a sampling design that includes several locations with various distances from trunks and measurement of all soil parameters down to the parent material for an accurate determination of forest SOC stocks. The storage of SOC in forest soils was mainly driven by climate with higher stocks under cool, humid regimes and lower stocks in warmer, drier regions. This highlights the importance of mountainous forest soils in the Alps and low mountain ranges of Bavaria as a major C pool. Strong correlations with climate were superimposed in the topsoil by clay content and tree species composition indicated by pH values. No significant differences of entire SOC storage were detected between broadleaf, mixed and coniferous forests. However, coniferous forests accumulated around 35\,\% of total SOC in the unprotected organic layer that is prone to human disturbance, forest fires and rising temperatures. In contrast, mixed and particularly broadleaf forests stored significantly higher amounts of SOC in the mineral soil. Moreover, mineral SOC stocks of mixed and broadleaf forests remained unchanged or were even slightly higher in regions with higher temperatures, demonstrating their low actual temperature sensitivity, whereas coniferous mineral SOC stocks were continuously lower. Thus, we conclude that an incorporation of broadleaf species in expanded coniferous forests of Bavaria associated with a translocation of SOC from the forest floor into the mineral soil would promote C sequestration in the long-term, particularly under increased temperatures.},
  keywords = {*imported-from-citeulike-INRMM,~INRMM-MiD:c-13930720,~to-add-doi-URL,carbon-stock,climate,forest-resources,germany,organic-carbon,precipitation,soil-carbon,soil-resources,temperate-forests,temperature,topographic-wetness-index},
  options = {useprefix=true}
}

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