Explore the vast range of titles available.

Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.

ABSTRACT Drought and agricultural management influence soil microorganisms with unknown consequences for the functioning of agroecosystems. We simulated drought periods in organic (biodynamic) and conventional wheat fields and monitored effects on soil water content, microorganisms and crops. Above the wilting point, water content and microbial respiration were higher under biodynamic than conventional farming. Highest bacterial and fungal abundances were found in biodynamically managed soils, and distinct microbial communities characterised the farming systems. Most biological soil quality parameters and crop yields were only marginally affected by the experimental drought, except for arbuscular mycorrhizal fungi (AMF), which increased in abundance under the experimental drought in both farming systems. AMF were further strongly promoted by biodynamic farming resulting in almost three times higher AMF abundance under experimental drought in the biodynamic compared with the conventional farming system. Our data suggest an improved water storage capacity under biodynamic farming and confirms positive effects of biodynamic farming on biological soil quality. The interactive effects of the farming system and drought may further be investigated under more substantial droughts. Given the importance of AMF for the plant's water supply, more in-depth studies on AMF may help to clarify their role for yields under conditions predicted by future climate scenarios. The impact of simulated summer drought on biological soil properties, microbial diversity and winter wheat yields was compared with rainout shelters under long-term conventional and organic agriculture.

1. Ecological stoichiometry predicts important control of the relative abundance of the key elements carbon (C), nitrogen (N) and phosphorus (P) on trophic interactions. In a nutrient-poor Amazonian lowland rain forest of French Guiana, we tested the hypothesis that decomposers exploit stoichiometrically diverse plant litter more efficiently, resulting in faster litter decomposition compared to litter with a uniform stoichiometry. 2. In a field experiment in the presence or absence of soil macrofauna, we measured litter mass loss, and N and P dynamics from all possible combinations of leaf litter from four common tree species which were distinctly separated along a C:N and along a N:P gradient. 3. Mean litter mass remaining after 204 days of field exposure varied between 25.2% and 71.3% among litter treatments. Fauna increased litter mass loss by 18%, N loss by 21% and P loss by 14%. Litter species richness had no effect on litter mass loss or nutrient dynamics. In contrast, litter mass and nutrient losses increased with increasing stoichiometric dissimilarity of litter mixtures in presence of fauna, suggesting faster decomposition of a stoichiometrically more heterogeneous litter. 4. However, the effect of stoichiometric dissimilarity was smaller than the strong C quality related litter composition effect and disappeared in the absence of fauna. Increasing proportions of litter that is relatively rich in accessible C compounds (non-structural carbohydrates, phenolics) and relatively poor in recalcitrant C (condensed tannins, lignin), correlated best with litter mass loss irrespective of fauna presence. No correlation was found for any of the nutrient related litter quality parameters and decomposition. 5.Synthesis. Our results suggest that Amazonian decomposer communities studied here are primarily limited by energy, and only secondarily by litter stoichiometry. Tropical tree species might thus influence decomposers and detritivores by the production of litter of specific C quality with potentially important feedback effects on ecosystem nutrient dynamics and availability.

Soil biodiversity constitutes the biological pillars of ecosystem services provided by soils worldwide. Soil life is threatened by intense agricultural management and shifts in climatic conditions as two important global change drivers which are not often jointly studied under field conditions. We addressed the effects of experimental short-term drought over the wheat growing season on soil organisms and ecosystem functions under organic and conventional farming in a Swiss long term trial. Our results suggest that activity and community metrics are suitable indicators for drought stress while microbial communities primarily responded to agricultural practices. Importantly, we found a significant loss of multiple pairwise positive and negative relationships between soil biota and process-related variables in response to conventional farming, but not in response to experimental drought. These results suggest a considerable weakening of the contribution of soil biota to ecosystem functions under long-term conventional agriculture. Independent of the farming system, experimental and seasonal (ambient) drought conditions directly affected soil biota and activity. A higher soil water content during early and intermediate stages of the growing season and a high number of significant relationships between soil biota to ecosystem functions suggest that organic farming provides a buffer against drought effects.

1. It is well known that plant–soil interactions play an important role in determining the impact of global change phenomena on biodiversity and ecosystem functioning. Little is known, however, about the individual and relative importance for carbon (C) and nitrogen (N) cycling of non-random changes in plant and soil communities that result from global change phenomena, such as fertilization and agricultural intensification. 2. We set up a field-based mesocosm experiment in which we re-inoculated soil with contrasting microbial communities taken from extensively managed and from intensively managed grasslands. In a full-factorial design, we subsequently established plant communities representative of intensively and extensively managed grasslands and imposed a fertilization treatment. We then measured plant biomass and diversity, and leaching of C and N as key measures of C and N loss. 3. We hypothesized that non-random changes in both microbial and plant communities would impact C and N leaching, but via different mechanisms. We predicted that plant communities representative of extensively managed grassland would reduce C and N leaching directly through increased water or N uptake, or indirectly via promoting microbial communities that immobilize C and N, whereas plant communities of intensively managed grassland would have the opposite effect. We also hypothesized that microbial communities of extensively managed grassland would feed back positively to plant diversity and that 'matching' plant and microbial communities would reduce C and N leaching. 4. We found that both plant and microbial communities from extensively managed grassland reduced C and N leaching, especially when 'matched'. Plant community effects on C and N leaching operated directly through root C inputs and N uptake, rather than through changes in soil microbial communities. In contrast, microbial communities modified C and N leaching both directly by immobilization and indirectly through modifying plant community composition. 5. Synthesis. Our results show that changes in plant and microbial communities both individually and interactively modify C and N loss from grasslands. Moreover, our results suggest that soil microbial communities typical of extensively managed grassland might counteract, or delay, the negative consequences of fertilization on plant diversity and ecosystem functioning.

Background Soils contain the largest stock of organic carbon (C) in terrestrial ecosystems and changes in soil C stocks may significantly affect atmospheric CO 2 . A significant part of soil C is present in cultivated soils that occupy about 35 % of the global land surface. Agricultural intensification has led to practices that may decrease soil organic carbon (SOC), and agricultural management has the potential to be a powerful tool for climate change mitigation and increased soil fertility through SOC sequestration. Here, we systematically map evidence relating to the impacts of agricultural management on SOC in arable systems of the warm temperate and snow climate zones (subset of temperate and continental climates: Köppen–Geiger Classification). Methods Seventeen academic citation databases, 3 search engines and 25 organisational websites were searched for literature (academic and grey) using search strings translated into a range of languages relevant to the included geographical scope of the topic. Stakeholders were also contacted with requests for evidence. Bibliographic checking of 127 relevant reviews was undertaken to check for missing articles. Screening for relevance against predefined inclusion criteria was undertaken at title, abstract and full text levels according to a published protocol. All relevant studies were coded in a meta-database describing the citation, study settings, methods and quantitative data available (without extraction of the study findings). A basic critical appraisal of included studies was also performed. A geographical information system (GIS) presenting the map database on a physical, online map was also produced. Results A total of 735 studies from 553 articles was included in the systematic map database. Studies investigated one or more of five broad categories of interventions: amendments (286 studies), crop rotations (238), fertilisers (307), tillage (306), and multiple interventions (55). Studies were identified from across the includible climate zones, with the notable underrepresentation from Russia. The majority of studies employed only point sampling of SOC, low levels of true spatial replication and moderate study periods (i.e. 10–20 years). Missing key methodological information was found in 28 % of studies. Conclusions Long-term study sites identified in this map provide a useful addition to existing databases of long-term experiments (LTEs). The identification of knowledge gaps, such as studies from Russia, also identify a need for improved cataloguing or reporting of existing and on-going research. This systematic map database represents a useful resource for decision-makers wishing to identify knowledge gaps warranting further primary research, knowledge gluts warranting further secondary research, and deficiencies and best practice in research methodology. In addition to the systematic map database, we have also produced two further resources: (1) a database of LTE sites investigating agricultural management and SOC, and (2) a database of reviews and meta-analyses. To our knowledge, this is the first systematic review or map that utilises a GIS for presentation of an evidence base, which we believe substantially increases the utility of the map outputs.

Background Soils are important global carbon pools that are under threat from intensive land use through a variety of agricultural practices. Sustainable management of agricultural soils may have the potential to mitigate climate change through increased carbon sequestration and increase their fertility. Among management practices to increase carbon sequestration, crop rotation designs have often been tested on yield effects in long-term agricultural experiments. However, in these studies, soil organic carbon (SOC) was monitored but not always the key objective. Thus, here we provide a method for a systematic review to test the effects of common crop rotations on SOC sequestration to provide evidence on the most sustainable management regimes that can promote SOC storage. Methods This systematic review incorporates studies concerning selected crop rotations (rotations-vs-monocultures, legumes-vs-no legumes, and perennials-vs-annuals) collated in a recently completed systematic map on the effect of agricultural management on SOC, restricted to boreo-temperate systems (i.e., the warm temperate climate zone). Some 208 studies relevant for this systematic review were identified in the systematic map. An update of the original search (September 2013) will be undertaken to identify newly published academic and grey literature. Studies will be critically appraised for their internal and external validity, followed by full data extraction (meta-data describing study settings and quantitative study results). Where possible, studies will be included in meta-analyses examining the effects of the different rotational practices. Implications of the findings will be discussed in terms of policy, practice and research, and the nature of the evidence base.

Questions: How is succession on ex-arable land affected by sowing high and low diversity mixtures of grassland species as compared to natural succession? How long do effects persist? Location: Experimental plots installed in the Czech Republic, The Netherlands, Spain, Sweden and the United Kingdom. Methods: The experiment was established on ex-arable land, with five blocks, each containing three 10 m × 10 m experimental plots: natural colonization, a low- (four species) and high-diversity (15 species) seed mixture. Species composition and biomass was followed for eight years. Results: The sown plants considerably affected the whole successional pathway and the effects persisted during the whole eight year period. Whilst the proportion of sown species (characterized by their cover) increased during the study period, the number of sown species started to decrease from the third season onwards. Sowing caused suppression of natural colonizing species, and the sown plots had more biomass. These effects were on average larger in the high diversity mixtures. However, the low diversity replicate sown with the mixture that produced the largest biomass or largest suppression of natural colonizers fell within the range recorded at the five replicates of the high diversity plots. The natural colonization plots usually had the highest total species richness and lowest productivity at the end of the observation period. Conclusions: The effect of sowing demonstrated dispersal limitation as a factor controlling the rate of early secondary succession. Diversity was important primarily for its ‘insurance effect’: the high diversity mixtures were always able to compensate for the failure of some species. Abbreviations; ED = Euclidian distance; HD = High diversity; LD = Low diversity; NC = Natural colonization

Background The loss of carbon (C) from agricultural soils has been, in part, attributed to tillage, a common practice providing a number of benefits to farmers. The promotion of less intensive tillage practices and no tillage (NT) (the absence of mechanical soil disturbance) aims to mitigate negative impacts on soil quality and to preserve soil organic carbon (SOC). Several reviews and meta-analyses have shown both beneficial and null effects on SOC due to no tillage relative to conventional tillage, hence there is a need for a comprehensive systematic review to answer the question: what is the impact of reduced tillage intensity on SOC? Methods We systematically reviewed relevant research in boreo-temperate regions using, as a basis, evidence identified within a recently completed systematic map on the impacts of farming on SOC. We performed an update of the original searches to include studies published since the map search. We screened all evidence for relevance according to predetermined inclusion criteria. Studies were appraised and subject to data extraction. Meta-analyses were performed to investigate the impact of reducing tillage [from high (HT) to intermediate intensity (IT), HT to NT, and from IT to NT] for SOC concentration and SOC stock in the upper soil and at lower depths. Results A total of 351 studies were included in the systematic review: 18% from an update of research published in the 2 years since the systematic map. SOC concentration was significantly higher in NT relative to both IT [1.18 g/kg ± 0.34 (SE)] and HT [2.09 g/kg ± 0.34 (SE)] in the upper soil layer (0–15 cm). IT was also found to be significant higher [1.30 g/kg ± 0.22 (SE)] in SOC concentration than HT for the upper soil layer (0–15 cm). At lower depths, only IT SOC compared with HT at 15–30 cm showed a significant difference; being 0.89 g/kg [± 0.20 (SE)] lower in intermediate intensity tillage. For stock data NT had significantly higher SOC stocks down to 30 cm than either HT [4.61 Mg/ha ± 1.95 (SE)] or IT [3.85 Mg/ha ± 1.64 (SE)]. No other comparisons were significant. Conclusions The transition of tilled croplands to NT and conservation tillage has been credited with substantial potential to mitigate climate change via C storage. Based on our results, C stock increase under NT compared to HT was in the upper soil (0–30 cm) around 4.6 Mg/ha (0.78–8.43 Mg/ha, 95% CI) over ≥ 10 years, while no effect was detected in the full soil profile. The results support those from several previous studies and reviews that NT and IT increase SOC in the topsoil. Higher SOC stocks or concentrations in the upper soil not only promote a more productive soil with higher biological activity but also provide resilience to extreme weather conditions. The effect of tillage practices on total SOC stocks will be further evaluated in a forthcoming project accounting for soil bulk densities and crop yields. Our findings can hopefully be used to guide policies for sustainable management of agricultural soils.

Background Loss of soil organic carbon (SOC) from agricultural land is identified as one of the major threats to soils, as it influences both fertility and the production of ecosystem services from agriculture. Losses of SOC across regions are often determined by monitoring in different land use systems. Results from agricultural field experiments can reveal increasing SOC stocks after implementation of specific management practices compared to a control, though in time series experiments the relative rate of change is often negative and implying an overall loss. Long-term agricultural field experiments are indispensable for quantifying absolute changes in SOC stocks under different management regimes. Since SOC responses are seldom linear over time, time series data from these experiments are particularly valuable. Methods This systematic review is based on studies reporting time series data collated in a recently completed systematic map on the topic restricted to the warm temperate climate zone and the snow climate zone. These 53 studies were identified and selected systematically according to CEE guidelines. An update of the original search for studies will be repeated using Web of Science and Google Scholar to include newly published academic and grey literature in the time since the original search was performed in September 2013. Studies will be subject to critical appraisal of the internal and external validity, followed by full data extraction (meta-data describing study settings and quantitative study results). Where possible, studies will be included in a quantitative synthesis using time series meta-analytical approaches. The implications of the meta-analytical findings will be discussed in terms of policy, practice and research along with a discussion of the nature of the evidence base.