scholarly journals Microbial Utilisation of Aboveground Litter-Derived Organic Carbon Within a Sandy Dystric Cambisol Profile

2021 ◽  
Vol 1 ◽  
Author(s):  
Sebastian Preusser ◽  
Patrick Liebmann ◽  
Andres Stucke ◽  
Johannes Wirsching ◽  
Karolin Müller ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Soil Depth ◽  
Sampling Period ◽  
Beech Forest ◽  
Stable Isotope Labelling ◽  
C Stocks ◽  
Microbial Groups ◽  
Aboveground Litter ◽  
Over Time

Litter-derived dissolved organic carbon (DOC) is considered to be a major source of stabilised C in soil. Here we investigated the microbial utilisation of litter-derived DOC within an entire soil profile using a stable isotope labelling experiment in a temperate beech forest. The natural litter layer of a Dystric Cambisol was replaced by 13C enriched litter within three areas of each 6.57 m−2 for 22 months and then replaced again by natural litter (switching-off the 13C input). Samples were taken continuously from 0 to 180 cm depths directly after the replacement of the labelled litter, and 6 and 18 months thereafter. We followed the pulse of 13C derived from aboveground litter into soil microorganisms through depth and over time by analysing 13C incorporation into microbial biomass and phospholipid fatty acids. Throughout the sampling period, most of the litter-derived microbial C was found in the top cm of the profile and only minor quantities were translocated to deeper soil. The microbial 13C stocks below 30 cm soil depth at the different samplings accounted constantly for only 6–12% of the respective microbial 13C stocks of the entire profile. The peak in proportional enrichment of 13C in subsoil microorganisms moved from upper (≤ 80 cm soil depth) to lower subsoil (80–160 cm soil depth) within a period of 6 months after switch-off, and nearly disappeared in microbial biomass after 18 months (< 1%), indicating little long-term utilisation of litter-derived C by subsoil microorganisms. Among the different microbial groups, a higher maximum proportion of litter-derived C was found in fungi (up to 6%) than in bacteria (2%), indicating greater fungal than bacterial dependency on litter-derived C in subsoil. However, in contrast to topsoil, fungi in subsoil had only a temporarily restricted increase in litter C incorporation, while in the Gram-positive bacteria, the C incorporation in subsoil raised moderately over time increasingly contributing to the group-specific C stock of the entire profile (up to 9%). Overall, this study demonstrated that microorganisms in topsoil of a Dystric Cambisol process most of the recently deposited aboveground litter C, while microbial litter-derived C assimilation in subsoil is low.

scholarly journals Comparatives Study of Soil Organic Carbon (SOC) under Forest, Cultivated and Barren Land: A Case of Chovar Village, Kathmandu

2014 ◽  
Vol 14 (2) ◽  
pp. 103-108 ◽  
Author(s):  
S Bhandari ◽  
S Bam
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Forest Soil ◽  
Agricultural Land ◽  
Soil Depth ◽  
Barren Land ◽  
C Stocks ◽  
Soc Stock ◽  
Land Use And Management

The study was carried out in Chovar village of Kritipur Municipality, Kathmandu to compare the soil organic carbon (SOC) of three main land use types namely forest, agricultural and barren land and to show how land use and management are among the most important determinants of SOC stock. Stratified random sampling method was used for collecting soil samples. Walkley and Black method was applied for measuring SOC. Land use and soil depth both affected SOC stock significantly. Forest soil had higher SOC stock (98 t ha-1) as compared to agricultural land with 36.6 t ha-1 and barren land with 83.6 t ha-1. Similarly, the SOC in terms of CO22-1, 79.27 to 22.02 CO2-e ha-1 and 121.11 to 80.74 CO2-1 for 0- 20 cm to 40-60 cm soil depth, respectively. Bulk density (BD) was found less in forest soil compared to other lands at all depths, which showed negative correlation with SOC. The study showed a dire need to increase current soil C stocks which can be achieved through improvements in land use and management practices, particularly through conservation and restoration of degraded forests and soils.   DOI: http://dx.doi.org/10.3126/njst.v14i2.10422   Nepal Journal of Science and Technology Vol. 14, No. 2 (2013) 103-108

scholarly journals Effects of species-dominated patches on soil organic carbon and total nitrogen storage in a degraded grassland in China

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6897 ◽  
Author(s):  
Yujuan Zhang ◽  
Shiming Tang ◽  
Shu Xie ◽  
Kesi Liu ◽  
Jinsheng Li ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Total Nitrogen ◽  
Microbial Biomass Nitrogen ◽  
Soil C ◽  
Artemisia Frigida ◽  
C Stocks ◽  
Soil C And N ◽  
C And N

Background Patchy vegetation is a very common phenomenon due to long-term overgrazing in degraded steppe grasslands, which results in substantial uncertainty associated with soil carbon (C) and nitrogen (N) dynamics because of changes in the amount of litter accumulation and nutrition input into soil. Methods We investigated soil C and N stocks beneath three types of monodominant species patches according to community dominance. Stipa krylovii patches, Artemisia frigida patches, and Potentilla acaulis patches represent better to worse vegetation conditions in a grassland in northern China. Results The results revealed that the soil C stock (0–40 cm) changed significantly, from 84.7 to 95.7 Mg ha−1, and that the soil organic carbon content (0–10 cm) and microbial biomass carbon (0–10 and 10–20 cm) varied remarkably among the different monodominant species communities (P < 0.05). However, soil total nitrogen and microbial biomass nitrogen showed no significant differences among different plant patches in the top 0–20 cm of topsoil. The soil C stocks under the P. acaulis and S. krylovii patches were greater than that under the A. frigida patch. Our study implies that accurate estimates of soil C and N storage in degenerated grassland require integrated analyses of the concurrent effects of differences in plant community composition.

scholarly journals Relevance of aboveground litter for soil organic matter formation – a soil profile perspective

2020 ◽  
Vol 17 (12) ◽  
pp. 3099-3113
Author(s):  
Patrick Liebmann ◽  
Patrick Wordell-Dietrich ◽  
Karsten Kalbitz ◽  
Robert Mikutta ◽  
Fabian Kalks ◽  
...  
Keyword(s):  
Organic Matter ◽  
Stable Isotope ◽  
Soil Profile ◽  
Isotope Labeling ◽  
Soil Depth ◽  
Litter Layer ◽  
Field Exposure ◽  
C Stocks ◽  
The Stability ◽  
Aboveground Litter

Abstract. In contrast to mineral topsoils, in subsoils the origin and processes leading to the formation and stabilization of organic matter (OM) are still not well known. This study addresses the fate of litter-derived carbon (C) in whole soil profiles with regard to the conceptual cascade model, which proposes that OM formation in subsoils is linked to sorption–microbial processing–remobilization cycles during the downward migration of dissolved organic carbon (DOC). Our main objectives were to quantify the contribution of recent litter to subsoil C stocks via DOC translocation and to evaluate the stability of litter-derived OM in different functional OM fractions. A plot-scale stable isotope-labeling experiment was conducted in a temperate beech forest by replacing the natural litter layer with 13C enriched litter on an area of 20 m2 above a Dystric Cambisol. After 22 months of field exposure, the labeled litter was replaced again by natural litter and soil cores were drilled down to 180 cm soil depth. Water extraction and density fractionation were combined with stable isotope measurements in order to link the fluxes of recent litter-derived C to its allocation into different functional OM fractions. A second sampling was conducted 18 months later to further account for the stability of translocated young litter-derived C. Almost no litter-derived particulate OM (POM) entered the subsoil, suggesting root biomass as the major source of subsoil POM. The contribution of aboveground litter to the formation of mineral-associated OM (MAOM) in topsoils (0–10 cm) was 1.88±0.83 g C m−2 and decreased to 0.69±0.19 g C m−2 in the upper subsoil (10–50 cm) and 0.01±0.02 g C m−2 in the deep subsoil >100 cm soil depth during the 22 months. This finding suggests a subordinate importance of recent litter layer inputs via DOC translocation to subsoil C stocks, and implies that most of the OM in the subsoil is of older age. Smaller losses of litter-derived C within MAOM of about 66 % compared to POM (77 %–89 %) over 18 months indicate that recent carbon can be stabilized by interaction with mineral surfaces; although the overall stabilization in the sandy study soils is limited. Our isotope-labeling approach supports the concept of OM undergoing a sequence of cycles of sorption, microbial processing, and desorption while migrating down a soil profile, which needs to be considered in models of soil OM formation and subsoil C cycling.

scholarly journals Relevance of aboveground litter for soil organic matter formation – a soil profile perspective

2020 ◽  
Author(s):  
Patrick Liebmann ◽  
Patrick Wordell-Dietrich ◽  
Karsten Kalbitz ◽  
Robert Mikutta ◽  
Fabian Kalks ◽  
...  
Keyword(s):  
Organic Matter ◽  
Stable Isotope ◽  
Soil Profile ◽  
Isotope Labeling ◽  
Soil Depth ◽  
Litter Layer ◽  
Field Exposure ◽  
C Stocks ◽  
The Stability ◽  
Aboveground Litter

Abstract. In contrast to mineral topsoils, the origin and processes leading to the formation and stabilization of organic matter (OM) in subsoils is still not well known. This study addresses the fate of litter-derived carbon (C) in whole soil profiles with regard to the conceptual cascade model, which proposes that OM formation in subsoils is linked to sorption-microbial processing-remobilization cycles during the downward migration of dissolved organic carbon (DOC). Our main objectives were to quantify the contribution of recent litter to subsoil C stocks via DOC movement and to evaluate the stability of litter-derived OM in different functional OM fractions. A plot-scale stable isotope labeling experiment was conducted in a temperate beech forest by replacing the natural litter layer with 13C enriched litter on an area of 20 m2 above a Dystric Cambisol. After 22 months of field exposure, the labeled litter was replaced again by natural litter and soil cores were drilled down to 180 cm soil depth. Water extraction and density fractionation were combined with stable isotope measurements in order to link the fluxes of recent litter-derived C to its allocation into different functional OM fractions. A second sampling was conducted 18 months later to further account for the stability of translocated young litter-derived C. Almost no litter-derived particulate OM (POM) entered the subsoil, suggesting root biomass as the major source of subsoil POM. The contribution of aboveground litter to the formation of mineral-associated OM (MAOM) in topsoils (0–10 cm) was 0.99 ± 0.45 g C m−2 yr−1, and decreased to 0.37 ± 0.10 g C m−2 yr−1 in the upper subsoil (10–50 cm) and 0.01 ± 0.01 g C m−2 yr−1 in the deep subsoil > 100 cm soil depth. This finding suggests a subordinate importance of recent litter layer inputs via DOC translocation to subsoil C stocks, and implies that most of the OM in the subsoil is of older age. Smaller losses of litter-derived C within MAOM of about 66 % compared to POM (77–89 %) indicate that recent carbon can be stabilized by interaction with mineral surfaces; although the overall stabilization in the sandy study soils was low. Our isotope labeling approach supports the concept of OM undergoing a sequence of cycles of sorption, microbial processing, and desorption while migrating down a soil profile, which needs to be considered in models on soil OM formation and subsoil C cycling.

scholarly journals Changes in Soil Microbial Biomass, Community Composition, and Enzyme Activities After Half-Century Forest Restoration in Degraded Tropical Lands

Forests ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1124 ◽  
Author(s):  
Huiling Zhang ◽  
Xin Xiong ◽  
Jianping Wu ◽  
Jianqi Zhao ◽  
Mengdi Zhao ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Enzyme Activities ◽  
Soil Microbial Biomass ◽  
Extracellular Enzymes ◽  
Soil Depth ◽  
Microbial Properties ◽  
Soil Microbial ◽  
Eucalyptus Forest ◽  
Different Seasons ◽  
Microbial Groups

Soil carbon (C) sequestration and stabilization are determined by not only the C input to the soil but also the decomposition rate of soil organic matter (SOM), which is mainly mediated by soil microbes. Afforestation, an effective practice to restore forests from degraded or bare lands, may alter soil microbial properties, and thus soil C and nitrogen (N) dynamics. The aim of this study was to investigate the impacts of different afforestation strategies on soil microbial compositions and activities after afforestation for half a century. Soil samples were collected from two afforested sites (i.e., a restored secondary forest (RSF) and a managed Eucalyptus forest (MEP)) and two reference sites (i.e., a nearby undisturbed forest (UF), representing the climax vegetation and a bare land (BL), representing the original state before restoration) in south China. We quantified the soil microbial biomass, microbial community compositions, and activities of nine extracellular enzymes at different soil depths and in different seasons. Results showed that the soil microbial biomass, all the main soil microbial groups, and the activities of all extracellular enzymes were significantly increased after afforestation compared to the BL sites, while the ratios of fungi/bacteria (F/B), specific enzyme activities, and the ecoenzymatic stoichiometry were significantly decreased regardless of the season and soil depth. Between the two afforested sites, these microbial properties were generally higher in the RSF than MEP. However, the microbial properties in the RSF were still lower than those in the UF, although the differences varied with different seasons, soil depths, and microbial groups or enzymes. Our findings demonstrated that afforestation might significantly improve microbial properties. Afforestation is more effective in mixed-species plantation than in the monoculture Eucalyptus plantation but needs a much longer time to approach an equivalent level to the primary forests.

Contribution of inorganic carbon to CO2 emissions under a Mediterranean agroforestry system

2020 ◽  
Author(s):  
Tiphaine Chevallier ◽  
Rémi Cardinael ◽  
Bertrand Guenet ◽  
Thomas Cozzi ◽  
Cyril Girardin ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Co2 Emissions ◽  
Inorganic Carbon ◽  
Soil Depth ◽  
Biological Activities ◽  
Agroforestry System ◽  
Soil Samples ◽  
Arid Environments ◽  
Equilibrium Equations

&lt;p&gt;In the last years, soil organic carbon (SOC) dynamics have been explored for agronomic and environmental issues in different agro systems. Many soils of the world, especially in arid and semi-arid environments, contain large stocks of soil inorganic carbon (SIC) as carbonates. Yet, the SOC dynamics has been poorly investigated in these soils, due to the complexity of measurements and of the processes involved. Indeed, few previous studies have shown links between SIC and SOC dynamics. Theses interactions are initiated by biological activities, i.e. CO&lt;sub&gt;2&lt;/sub&gt; production, are explained through equilibrium equations between soil carbonates and bicarbonates. However, few data were available on the specific impact of SIC on SOC mineralization especially at increasing soil depth.&lt;/p&gt;&lt;p&gt;Alley agroforestry systems increased SOC content in the tree rows without any change in the SIC content.&amp;#160; The heterogeneity in organic inputs and SOC contents induced by alley agroforestry allows the investigation of the interactions between SIC and SOC on CO&lt;sub&gt;2&lt;/sub&gt; emissions.&lt;/p&gt;&lt;p&gt;To assess contributions of SIC to CO&lt;sub&gt;2&lt;/sub&gt; emissions with depth, we incubated carbonaceous soil samples coming from an 18-year-old agroforestry system (both tree row and alley) and an adjacent agricultural plot. Soil samples were taken at four different depths: 0-10, 10-30, 70-100 and 160-180 cm. Total CO&lt;sub&gt;2&lt;/sub&gt; emissions, the isotopic composition (&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C, &amp;#8240;) of the CO&lt;sub&gt;2&lt;/sub&gt; and microbial biomass were measured. The SIC concentrations were from 48 to 63 g C kg&lt;sup&gt;-1&lt;/sup&gt; soil and the SOC concentrations from 4 to 17 g C kg&lt;sup&gt;-1&lt;/sup&gt; soil. The total amounts of CO&lt;sub&gt;2&lt;/sub&gt; emissions from soil were correlated to C contents and decreased with depth (from 183-569 &amp;#181;gC g&lt;sup&gt;-1&lt;/sup&gt; soil in top soil vs 21-25 &amp;#181;gC g&lt;sup&gt;-1&lt;/sup&gt; soil in subsoil).&lt;/p&gt;&lt;p&gt;The contribution of SIC-derived CO&lt;sub&gt;2&lt;/sub&gt; was not homogenous along the soil profile. It represented about 20% in the topsoil and 60% in the subsoil of the total soil CO&lt;sub&gt;2&lt;/sub&gt; emissions. As the SOC content and the microbial biomass, the SOC-derived CO&lt;sub&gt;2&lt;/sub&gt; emissions were larger in the topsoil especially in the tree row compared to the alley and the agricultural plot. The SIC-derived CO&lt;sub&gt;2&lt;/sub&gt; emissions were also larger in topsoil and in tree rows at 0-10 cm than in alleys or agricultural plots (71 &amp;#181;g C g&lt;sup&gt;-1&lt;/sup&gt; soil vs 45-48 &amp;#181;g C g&lt;sup&gt;-1&lt;/sup&gt; soil) or in the subsoil (13-15 &amp;#181;g C g&lt;sup&gt;-1&lt;/sup&gt; soil), whereas the amount of SIC was similar in top and subsoil and in tree rows, alleys or agricultural soils. This indicate that CO&lt;sub&gt;2&lt;/sub&gt; emissions from SIC were linked to the SOC content and its mineralization.&amp;#160; In addition, our results suggest that the measurement of soil respiration in calcareous soils could be overestimated if the isotopic signature of the CO&lt;sub&gt;2&lt;/sub&gt; is not taken into account. It also advocates more in-depth studies on carbonate dissolution-precipitation processes and their impact on CO&lt;sub&gt;2 &lt;/sub&gt;emissions.&lt;/p&gt;&lt;p&gt;Reference:&lt;/p&gt;&lt;p&gt;Cardinael, R., Chevallier, T., Guenet, B., Girardin, C., Cozzi, T., Pouteau, V., and Chenu, C. 2019 Organic carbon decomposition rates with depth and contribution of inorganic carbon to CO2 emissions under a Mediterranean agroforestry system, Eur J Soil Sci, https://doi.org/10.1111/ejss.12908.&lt;/p&gt;

scholarly journals Effect of Litter-Derived Dissolved Organic Carbon Addition on Forest Soil Microbial Community Composition

2021 ◽  
Vol 1 ◽  
Author(s):  
Min Wang ◽  
Qiuxiang Tian ◽  
Chang Liao ◽  
Rudong Zhao ◽  
Feng Liu
Keyword(s):  
Microbial Community ◽  
Microbial Biomass ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Community Composition ◽  
Soil Microbial Biomass ◽  
Microbial Community Composition ◽  
Soil Microbial ◽  
Significant Difference ◽  
Microbial Groups

The input of dissolved organic carbon (DOC) into soil affects soil organic carbon mineralization and microbial community composition by changing carbon availability. However, up to now, there is little knowledge about the microbial groups that utilize the added DOC and how the incorporation process may vary over time. In this study, we added 13C-labeled litter-derived DOC (treatment) or pure water (control) to a forest soil from different layers to investigate the effects of DOC addition on soil microbial biomass and community composition in a 180-d laboratory incubation experiment. Soil microbial phospholipid fatty acid (PLFA) were measured to assess changes in the microbial community composition. The 13C incorporation into microbial biomass and PLFAs was analyzed to trace the microbial utilization of litter-derived DOC. Our results indicated that DOC addition increased the biomass of gram-negative bacteria, gram-positive bacteria, fungi, and actinomycetes, but the microbial community composition manifested a similar trend for both treatment and control soils at the end of incubation. Proportions of added DOC in different depths of soil microbial PLFAs had no significant difference. Moreover, 17:0 cy and 15:0 PLFAs which are described as the bacterial biomarkers had a greater amount of 13C incorporation than other PLFAs for the topsoil, which indicated that 13C-labeled litter-derived DOC was more easily assimilated by some specific bacterial community. Soil microbial biomass and the incorporation of 13C into PLFA reached its maximum around 30 days after DOC addition and then rapidly reduced to the level comparable to control. Overall, this study demonstrated that the incorporation of 13C-labeled litter-derived DOC into PLFA in different depth soil had no significant difference, and the incorporation of 13C by bacteria was higher than other microbial groups.

scholarly journals Whole-soil warming decreases abundance and modifies the community structure of microorganisms in the subsoil but not in surface soil

SOIL ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 477-494
Author(s):  
Cyrill U. Zosso ◽  
Nicholas O. E. Ofiti ◽  
Jennifer L. Soong ◽  
Emily F. Solly ◽  
Margaret S. Torn ◽  
...  
Keyword(s):  
Community Structure ◽  
Microbial Community ◽  
Microbial Biomass ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Community Composition ◽  
Soil Depth ◽  
Phospholipid Fatty Acid ◽  
Community Response ◽  
Similar Response

Abstract. The microbial community composition in subsoils remains understudied, and it is largely unknown whether subsoil microorganisms show a similar response to global warming as microorganisms at the soil surface do. Since microorganisms are the key drivers of soil organic carbon decomposition, this knowledge gap causes uncertainty in the predictions of future carbon cycling in the subsoil carbon pool (> 50 % of the soil organic carbon stocks are below 30 cm soil depth). In the Blodgett Forest field warming experiment (California, USA) we investigated how +4 ∘C warming in the whole-soil profile to 100 cm soil depth for 4.5 years has affected the abundance and community structure of microorganisms. We used proxies for bulk microbial biomass carbon (MBC) and functional microbial groups based on lipid biomarkers, such as phospholipid fatty acids (PLFAs) and branched glycerol dialkyl glycerol tetraethers (brGDGTs). With depth, the microbial biomass decreased and the community composition changed. Our results show that the concentration of PLFAs decreased with warming in the subsoil (below 30 cm) by 28 % but was not affected in the topsoil. Phospholipid fatty acid concentrations changed in concert with soil organic carbon. The microbial community response to warming was depth dependent. The relative abundance of Actinobacteria increased in warmed subsoil, and Gram+ bacteria in subsoils adapted their cell membrane structure to warming-induced stress, as indicated by the ratio of anteiso to iso branched PLFAs. Our results show for the first time that subsoil microorganisms can be more affected by warming compared to topsoil microorganisms. These microbial responses could be explained by the observed decrease in subsoil organic carbon concentrations in the warmed plots. A decrease in microbial abundance in warmed subsoils might reduce the magnitude of the respiration response over time. The shift in the subsoil microbial community towards more Actinobacteria might disproportionately enhance the degradation of previously stable subsoil carbon, as this group is able to metabolize complex carbon sources.

scholarly journals Whole soil warming decreases abundance and modifies community structure of microorganisms in subsoil but not in surface soil

2021 ◽  
Author(s):  
Cyrill U. Zosso ◽  
Nicholas O. E. Ofiti ◽  
Jennifer L. Soong ◽  
Emily F. Solly ◽  
Margaret S. Torn ◽  
...  
Keyword(s):  
Community Structure ◽  
Microbial Community ◽  
Microbial Biomass ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Community Composition ◽  
Soil Depth ◽  
Phospholipid Fatty Acid ◽  
Community Response ◽  
Similar Response

Abstract. The microbial community composition in subsoils remains understudied and it is largely unknown whether subsoil microorganisms show a similar response to global warming as do microorganisms at the soil surface. Since microorganisms are key drivers of soil organic carbon decomposition, this knowledge gap causes uncertainty in predictions of future carbon cycling in the subsoil carbon pool (>50 % of the soil organic carbon stocks are below 30 cm soil depth). In the Blodgett forest field warming experiment (California, USA) we investigated how +4 °C warming the whole soil profile to 100 cm soil depth for 4.5 years has affected the abundance and community structure of microorganisms. We used proxies for bulk microbial biomass carbon (MBC) and functional microbial groups based on lipid biomarkers, such as phospholipid fatty acids (PLFAs) and branched glycerol dialkyl glycerol tetraethers (brGDGTs). Microbial biomass decreased and community composition changed with depth. Our results show that the concentration of PLFAs decreased with warming in the subsoil (below 30 cm) by 28 % but was not affected in the topsoil. Phospholipid fatty acid concentrations changed in concert with soil organic carbon. The microbial community response to warming was depth dependent. The relative abundance of actinobacteria increased in subsoil, and gram+ bacteria in subsoils adapted their cell-membrane structure to warming induced stress as indicated by the ratio of anteiso to iso PLFAs. Our results show for the first time that subsoil microorganisms can be more affected by warming as compared to topsoil microorganisms. These microbial responses could be explained by the observed decrease in subsoil organic carbon concentration in the warmed plots. A decrease in microbial abundance in warmed subsoils might reduce the magnitude of the respiration response over time. The shift in the subsoil microbial community towards more actinobacteria might disproportionately enhance degradation of previously stable subsoil carbon, as this group is able to metabolize complex carbon sources.

scholarly journals Impact of reduced tillage on soil organic carbon and nutrient budgets under organic farming

2011 ◽  
Vol 27 (1) ◽  
pp. 68-80 ◽  
Author(s):  
Florian Gadermaier ◽  
Alfred Berner ◽  
Andreas Fließbach ◽  
Jürgen Kurt Friedel ◽  
Paul Mäder
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Fertility ◽  
Organic Farming ◽  
Soil Microbial Biomass ◽  
Soil Depth ◽  
Microbial Biomass C ◽  
Nutrient Budgets ◽  
Soil Microbial

AbstractNo-tillage (NT) and reduced tillage (RT) systems are well-known management tools for reducing soil erosion and improving soil fertility. NT and RT may improve the environmental and economic performance of organic farming, but they are still not common practice among organic farmers. This paper presents the effects of tillage [RT versus conventional tillage (CT)], fertilization (slurry versus manure compost) and biodynamic preparations (with versus without) on soil fertility indicators such as soil organic carbon (Corg), microbial biomass and microbial activity, soil nutrients and nutrient budgets in an organic farming system during the first six-year crop rotation period of a long-term experiment on a clayey soil in a temperate climate. RT caused stratification of soil organic carbon (Corg), microbial properties and soil nutrients in the soil profile. Under RT, Corg in the 0–10 cm soil layer increased from 2.19 to 2.61% (w/w) from 2002 to 2008, whereas it remained constant under CT. In both tillage treatments, Corg remained constant in the 10–20 cm soil depth. Microbial biomass C increased by 37% under RT in the 0–10 cm soil depth and microbial activity [dehydrogenase activity (DHA)] was enhanced by 57%. Soil microbial biomass C and DHA in the 10–20 cm soil depth were also higher under RT (+10 and +17%, respectively). Soluble soil P and K were 72 and 40%, respectively, higher in 0–10 cm soil depth under RT when compared with CT. Fertilization showed no effects on the measured soil properties. Biodynamic preparations increased solely the Cmic-to-Nmic (soil microbial biomass C to soil microbial biomass N) ratio by 7% in the 0–10 cm soil depth. Nutrient budgets for P were balanced in all treatments, but N and K exports were higher under RT compared to CT. We conclude that RT is a suitable method for increasing indicators of soil fertility in organic farming systems. The combined effects of RT and an organic farming system with a diverse, ley-based crop rotation and organic fertilization merit further promotion and it may be considered for supporting actions by the agricultural policy schemes.

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