Single introductions of soil biota and plants generate long-term legacies in soil and plant community assembly
Wubs, E.R.J. ; Putten, Wim H. van der; Mortimer, Simon R. ; Korthals, Gerard W. ; Duyts, Henk ; Wagenaar, Roel ; Bezemer, Martijn - \ 2019
Ecology Letters 22 (2019)7. - ISSN 1461-023X - p. 1145 - 1151.
Community assembly - nature restoration - plant–soil biota interactions - soil legacy - whole-soil inoculation
Recent demonstrations of the role of plant–soil biota interactions have challenged the conventional view that vegetation changes are mainly driven by changing abiotic conditions. However, while this concept has been validated under natural conditions, our understanding of the long-term consequences of plant–soil interactions for above-belowground community assembly is restricted to mathematical and conceptual model projections. Here, we demonstrate experimentally that one-time additions of soil biota and plant seeds alter soil-borne nematode and plant community composition in semi-natural grassland for 20 years. Over time, aboveground and belowground community composition became increasingly correlated, suggesting an increasing connectedness of soil biota and plants. We conclude that the initial composition of not only plant communities, but also soil communities has a long-lasting impact on the trajectory of community assembly.
Enhancing Soil Organic Matter as a Route to the Ecological Intensification of European Arable Systems
Garratt, M.P.D. ; Bommarco, R. ; Kleijn, D. ; Martin, E. ; Mortimer, S.R. ; Redlich, S. ; Senapathi, D. ; Steffan-Dewenter, I. ; Świtek, S. ; Takács, V. ; Gils, S. van; Putten, W.H. van der; Potts, S.G. - \ 2018
Ecosystems 21 (2018)7. - ISSN 1432-9840 - p. 1404 - 1415.
aphids - arable farming - ecological intensification - fertiliser, soil organic matter
Soil organic matter (SOM) is declining in most agricultural ecosystems, impacting multiple ecosystem services including erosion and flood prevention, climate and greenhouse gas regulation as well as other services that underpin crop production, such as nutrient cycling and pest control. Ecological intensification aims to enhance crop productivity by including regulating and supporting ecosystem service management into agricultural practices. We investigate the potential for increased SOM to support the ecological intensification of arable systems by reducing the need for nitrogen fertiliser application and pest control. Using a large-scale European field trial implemented across 84 fields in 5 countries, we tested whether increased SOM (using soil organic carbon as a proxy) helps recover yield in the absence of conventional nitrogen fertiliser and whether this also supports crops less favourable to key aphid pests. Greater SOM increased yield by 10%, but did not offset nitrogen fertiliser application entirely, which improved yield by 30%. Crop pest responses depended on species: Metopolophium dirhodum were more abundant in fertilised plots with high crop biomass, and although population growth rates of Sitobion avenae were enhanced by nitrogen fertiliser application in a cage trial, field populations were not affected. We conclude that under increased SOM and reduced fertiliser application, pest pressure can be reduced, while partially compensating for yield deficits linked to fertiliser reduction. If the benefits of reduced fertiliser application and increased SOM are considered in a wider environmental context, then a yield cost may become acceptable. Maintaining or increasing SOM is critical for achieving ecological intensification of European cereal production.
The EU societal awareness of landscape indicator : A review of its meaning, utility and performance across different scales
Jones, P.J. ; Andersen, E. ; Capitani, C. ; Carvalho Ribeiro, S. ; Griffiths, G.H. ; Loupa-Ramos, I. ; Madeira, L. ; Mortimer, S.R. ; Paracchini, M.L. ; Pinto Correia, T. ; Schmidt, A.M. ; Simoncini, R. ; Wascher, D.M. - \ 2016
Land Use Policy 53 (2016). - ISSN 0264-8377 - p. 112 - 122.
Geospatial indicators - Rural agrarian landscapes - Social and cultural values
There is increasing recognition that agricultural landscapes meet multiple societal needs and demands beyond provision of economic and environmental goods and services. Accordingly, there have been significant calls for the inclusion of societal, amenity and cultural values in agri-environmental landscape indicators to assist policy makers in monitoring the wider impacts of land-based policies. However, capturing the amenity and cultural values that rural agrarian areas provide, by use of such indicators, presents significant challenges. The EU social awareness of landscape indicator represents a new class of generalized social indicator using a top-down methodology to capture the social dimensions of landscape without reference to the specific structural and cultural characteristics of individual landscapes. This paper reviews this indicator in the context of existing agri-environmental indicators and their differing design concepts. Using a stakeholder consultation approach in five case study regions, the potential and limitations of the indicator are evaluated, with a particular focus on its perceived meaning, utility and performance in the context of different user groups and at different geographical scales. This analysis supplements previous EU-wide assessments, through regional scale assessment of the limitations and potentialities of the indicator and the need for further data collection. The evaluation finds that the perceived meaning of the indicator does not vary with scale, but in common with all mapped indicators, the usefulness of the indicator, to different user groups, does change with scale of presentation. This indicator is viewed as most useful when presented at the scale of governance at which end users operate. The relevance of the different sub-components of the indicator are also found to vary across regions.
Intensive agriculture reduces soil biodiversity across Europe
Tsiafouli, M.A. ; Thébault, E. ; Sgardelis, S. ; Ruiter, P.C. de; Putten, W.H. van der; Birkhofer, K. ; Hemerik, L. ; Vries, F.T. de; Bardgett, R.D. ; Brady, M. ; Bjornlund, L. ; Bracht Jörgensen, H. ; Christensen, S. ; Herfelt, T. D'; Hotes, S. ; Hol, W.H.G. ; Frouz, J. ; Liiri, M. ; Mortimer, S.R. ; Setälä, H. ; Stary, J. ; Tzanopoulos, J. ; Uteseny, C. ; Wolters, V. ; Hedlund, K. - \ 2015
Global Change Biology 21 (2015)2. - ISSN 1354-1013 - p. 973 - 985.
food-web structure - land-use intensity - taxonomic distinctness - community structure - phylogenetic diversity - arthropod communities - temporal variability - 7-year period - ecosystem - management
Soil biodiversity plays a key role in regulating the processes that underpin the delivery of ecosystem goods and services in terrestrial ecosystems. Agricultural intensification is known to change the diversity of individual groups of soil biota, but less is known about how intensification affects biodiversity of the soil food web as a whole, and whether or not these effects may be generalized across regions. We examined biodiversity in soil food webs from grasslands, extensive, and intensive rotations in four agricultural regions across Europe: in Sweden, the UK, the Czech Republic and Greece. Effects of land-use intensity were quantified based on structure and diversity among functional groups in the soil food web, as well as on community-weighted mean body mass of soil fauna. We also elucidate land-use intensity effects on diversity of taxonomic units within taxonomic groups of soil fauna. We found that between regions soil food web diversity measures were variable, but that increasing land-use intensity caused highly consistent responses. In particular, land-use intensification reduced the complexity in the soil food webs, as well as the community-weighted mean body mass of soil fauna. In all regions across Europe, species richness of earthworms, Collembolans, and oribatid mites was negatively affected by increased land-use intensity. The taxonomic distinctness, which is a measure of taxonomic relatedness of species in a community that is independent of species richness, was also reduced by land-use intensification. We conclude that intensive agriculture reduces soil biodiversity, making soil food webs less diverse and composed of smaller bodied organisms. Land-use intensification results in fewer functional groups of soil biota with fewer and taxonomically more closely related species. We discuss how these changes in soil biodiversity due to land-use intensification may threaten the functioning of soil in agricultural production systems.
Urban and agricultural soils: conflicts and trade-offs in the optimization of ecosystem services
Setälä, H. ; Bardgett, R.D. ; Birkhofer, K. ; Brady, M. ; Byrne, L. ; Ruiter, P.C. de; Vries, F.T. de; Gardi, C. ; Hedlund, K. ; Hemerik, A. ; Hotes, S. ; Liiri, M. ; Mortimer, S.R. ; Pavao-Zuckerman, M. ; Pouyat, R. ; Tsiafouli, M. ; Putten, W.H. van der - \ 2014
Urban Ecosystems 17 (2014)1. - ISSN 1083-8155 - p. 239 - 253.
biological-control - land-use - functional composition - united-states - landscapes - conservation - impact - carbon - infrastructure - sustainability
On-going human population growth and changing patterns of resource consumption are increasing global demand for ecosystem services, many of which are provided by soils. Some of these ecosystem services are linearly related to the surface area of pervious soil, whereas others show non-linear relationships, making ecosystem service optimization a complex task. As limited land availability creates conflicting demands among various types of land use, a central challenge is how to weigh these conflicting interests and how to achieve the best solutions possible from a perspective of sustainable societal development. These conflicting interests become most apparent in soils that are the most heavily used by humans for specific purposes: urban soils used for green spaces, housing, and other infrastructure and agricultural soils for producing food, fibres and biofuels. We argue that, despite their seemingly divergent uses of land, agricultural and urban soils share common features with regards to interactions between ecosystem services, and that the trade-offs associated with decision-making, while scale- and context-dependent, can be surprisingly similar between the two systems. We propose that the trade-offs within land use types and their soil-related ecosystems services are often disproportional, and quantifying these will enable ecologists and soil scientists to help policy makers optimizing management decisions when confronted with demands for multiple services under limited land availability.
Soil food web properties explain ecosystem services across European land use systems
Vries, F.T. de; Thebault, E.M.C. ; Liiri, M. ; Birkhofer, K. ; Tsiafouli, M. ; Bjornlund, L. ; Jorgensen, H.B. ; Brady, M.V. ; Christensen, S. ; Ruiter, P.C. de; Hertefeldt, T. d'; Frouz, J. ; Hedlund, K. ; Hemerik, L. ; Hol, W.H.G. ; Hotes, S. ; Mortimer, S.R. ; Setälä, H. ; Sgardelis, S.P. ; Uteseny, K. ; Putten, W.H. van der; Wolters, V. ; Bardgett, R.D. - \ 2013
Proceedings of the National Academy of Sciences of the United States of America 110 (2013)35. - ISSN 0027-8424 - p. 14296 - 14301.
nitrogen mineralization - carbon sequestration - bacterial community - mycorrhizal fungi - biomass - scale - intensification - decomposition - biodiversity - agriculture
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.
Community patterns of soil bacteria and nematodes in relation to geographic distance
Monroy, F. ; Putten, W.H. van der; Yergeau, E. ; Duyts, H. ; Mortimer, S.R. ; Bezemer, T.M. - \ 2012
Soil Biology and Biochemistry 45 (2012). - ISSN 0038-0717 - p. 1 - 7.
cooccurrence patterns - microbial communities - global diversity - chalk grassland - spatial scales - biogeography - ecology - microorganisms - biodiversity - gradient
Ecosystems consist of aboveground and belowground subsystems and the structure of their communities is known to change with distance. However, most of this knowledge originates from visible, aboveground components, whereas relatively little is known about how soil community structure varies with distance and if this variability depends on the group of organisms considered. In the present study, we analyzed 30 grasslands from three neighboring chalk hill ridges in southern UK to determine the effect of geographic distance (1–198 km) on the similarity of bacterial communities and of nematode communities in the soil. We found that for both groups, community similarity decayed with distance and that this spatial pattern was not related to changes either in plant community composition or soil chemistry. Site history may have contributed to the observed pattern in the case of nematodes, since the distance effect depended on the presence of different nematode taxa at one of the hill ridges. On the other hand, site-related differences in bacterial community composition alone could not explain the spatial turnover, suggesting that other factors, such as biotic gradients and local dispersal processes that we did not include in our analysis, may be involved in the observed pattern. We conclude that, independently of the variety of causal factors that may be involved, the decay in similarity with geographic distance is a characteristic feature of both communities of soil bacteria and nematodes.
Influences of space, soil, nematodes and plants on microbial community composition of chalk grassland soils
Yergeau, E. ; Bezemer, T.M. ; Hedlund, K. ; Mortimer, S.R. ; Kowalchuk, G.A. ; Putten, W.H. van der - \ 2010
Environmental Microbiology 12 (2010)8. - ISSN 1462-2912 - p. 2096 - 2106.
fatty-acid analysis - bacterial diversity - neighbor matrices - global patterns - ecological data - rhizosphere - protozoa - microorganisms - biogeography - gradient
Microbial communities respond to a variety of environmental factors related to resources (e.g. plant and soil organic matter), habitat (e.g. soil characteristics) and predation (e.g. nematodes, protozoa and viruses). However, the relative contribution of these factors on microbial community composition is poorly understood. Here, we sampled soils from 30 chalk grassland fields located in three different chalk hill ridges of Southern England, using a spatially explicit sampling scheme. We assessed microbial communities via phospholipid fatty acid (PLFA) analyses and PCR-denaturing gradient gel electrophoresis (DGGE) and measured soil characteristics, as well as nematode and plant community composition. The relative influences of space, soil, vegetation and nematodes on soil microorganisms were contrasted using variation partitioning and path analysis. Results indicate that soil characteristics and plant community composition, representing habitat and resources, shape soil microbial community composition, whereas the influence of nematodes, a potential predation factor, appears to be relatively small. Spatial variation in microbial community structure was detected at broad (between fields) and fine (within fields) scales, suggesting that microbial communities exhibit biogeographic patterns at different scales. Although our analysis included several relevant explanatory data sets, a large part of the variation in microbial communities remained unexplained (up to 92% in some analyses). However, in several analyses, significant parts of the variation in microbial community structure could be explained. The results of this study contribute to our understanding of the relative importance of different environmental and spatial factors in driving the composition of soil-borne microbial communities.
Climate vs. soil factors in local adaptation of two common plant species
Macel, M. ; Lawson, C.S. ; Mortimer, S.R. ; Smilauerova, M. ; Bischoff, A. ; Crémieux, L. ; Dolezal, J. ; Edwards, A.R. ; Lanta, V. ; Bezemer, T.M. ; Putten, W.H. van der; Igual, J.M. ; Rodriguez-Barrueco, C. ; Müller-Schärer, H. ; Steinger, T. - \ 2007
Ecology 88 (2007)2. - ISSN 0012-9658 - p. 424 - 433.
reciprocally sown populations - lotus-corniculatus - chamaecrista-fasciculata - clinal patterns - gene flow - evolution - performance - plasticity - feedback - establishment
Evolutionary theory suggests that divergent natural selection in heterogeneous environments can result in locally adapted plant genotypes. To understand local adaptation it is important to study the ecological factors responsible for divergent selection. At a continental scale, variation in climate can be important while at a local scale soil properties could also play a role. We designed an experiment aimed to disentangle the role of climate and (abiotic and biotic) soil properties in local adaptation of two common plant species. A grass (Holcus lanatus) and a legume (Lotus corniculatus), as well as their local soils, were reciprocally transplanted between three sites across an Atlantic¿Continental gradient in Europe and grown in common gardens in either their home soil or foreign soils. Growth and reproductive traits were measured over two growing seasons. In both species, we found significant environmental and genetic effects on most of the growth and reproductive traits and a significant interaction between the two environmental effects of soil and climate. The grass species showed significant home site advantage in most of the fitness components, which indicated adaptation to climate. We found no indication that the grass was adapted to local soil conditions. The legume showed a significant home soil advantage for number of fruits only and thus a weak indication of adaptation to soil and no adaptation to climate. Our results show that the importance of climate and soil factors as drivers of local adaptation is species-dependent. This could be related to differences in interactions between plant species and soil biota.
Long-term effectiveness of sowing high and low diversity seed mixtures to enhance plant community development on ex-arable fields
Leps, J. ; Dolezal, J. ; Bezemer, T.M. ; Brown, V.K. ; Hedlund, K. ; Igual Arroya, M. ; Jörgensen, H.B. ; Lawson, C.S. ; Mortimer, S.R. ; Peix Geldart, A. ; Rodríguez Barrueco, C. ; Santa Regina, I. ; Smilauer, P. ; Putten, W.H. van der - \ 2007
Applied Vegetation Science 10 (2007)1. - ISSN 1402-2001 - p. 97 - 110.
life-history strategies - productivity relationships - european grasslands - species diversity - restoration - succession - land - biodiversity - vegetation - invasion
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 x 10 m experiment tal 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.
Plant species and functional group effects on abiotic and microbial soil properties and plant-soil feedback responses in two grasslands
Bezemer, T.M. ; Lawson, C.S. ; Hedlund, K. ; Edwards, A.R. ; Brooks, A.J. ; Igual, J.M. ; Mortimer, S.R. ; Putten, W.H. van der - \ 2006
Journal of Ecology 94 (2006)5. - ISSN 0022-0477 - p. 893 - 904.
fatty-acid analysis - community structure - diversity - rhizosphere - vegetation - biota - dynamics - biomass - succession - management
1 Plant species differ in their capacity to influence soil organic matter, soil nutrient availability and the composition of soil microbial communities. Their influences on soil properties result in net positive or negative feedback effects, which influence plant performance and plant community composition. 2 For two grassland systems, one on a sandy soil in the Netherlands and one on a chalk soil in the United Kingdom, we investigated how individual plant species grown in monocultures changed abiotic and biotic soil conditions. Then, we determined feedback effects of these soils to plants of the same or different species. Feedback effects were analysed at the level of plant species and plant taxonomic groups (grasses vs. forbs). 3 In the sandy soils, plant species differed in their effects on soil chemical properties, in particular potassium levels, but PLFA (phospholipid fatty acid) signatures of the soil microbial community did not differ between plant species. The effects of soil chemical properties were even greater when grasses and forbs were compared, especially because potassium levels were lower in grass monocultures. 4 In the chalk soil, there were no effects of plant species on soil chemical properties, but PLFA profiles differed significantly between soils from different monocultures. PLFA profiles differed between species, rather than between grasses and forbs. 5 In the feedback experiment, all plant species in sandy soils grew less vigorously in soils conditioned by grasses than in soils conditioned by forbs. These effects correlated significantly with soil chemical properties. None of the seven plant species showed significant differences between performance in soil conditioned by the same vs. other plant species. 6 In the chalk soil, Sanguisorba minor and in particular Briza media performed best in soil collected from conspecifics, while Bromus erectus performed best in soil from heterospecifics. There was no distinctive pattern between soils collected from forb and grass monocultures, and plant performance could not be related to soil chemical properties or PLFA signatures. 7 Our study shows that mechanisms of plant-soil feedback can depend on plant species, plant taxonomic (or functional) groups and site-specific differences in abiotic and biotic soil properties. Understanding how plant species can influence their rhizosphere, and how other plant species respond to these changes, will greatly enhance our understanding of the functioning and stability of ecosystems.
Trait-based assembly rules govern grassland succession despite species divergence
Fukami, T. ; Bezemer, T.M. ; Mortimer, S.R. ; Putten, W.H. van der - \ 2005
succession of species in ecosystems is one of the most important yet controversial topics in ecology. The degree to which succession is deterministic, convergent, and predictable has been vigorously debated for nearly a century. In this study, we provide the first experimental evidence, to our knowledge, that succession can simultaneously be predictable and unpredictable. We manipulated initial plant species composition on abandoned arable land in the Netherlands and subsequently allowed natural colonization over nine years. We show that initial compositional variation causes plant communities to follow divergent pathways of succession in species composition. Such divergence makes succession appear strongly unpredictable. However, these same communities exhibit striking patterns of convergence in the composition of trait-based groups of plant species, indicating highly deterministic assembly rules. This contrast between species divergence and trait convergence is attributable to priority effects involving inhibition or facilitation rather than to statistical inevitability, dispersal limitation, or community neutrality. These results have profound implications for restoration of biodiversity: restoring specific species compositions may require detailed knowledge of how initial community states determine the direction of ecosystem assembly, even when communities converge predictably in species traits
Species divergence and trait convergence in experimental plant community assembly
Fukami, T. ; Bezemer, T.M. ; Mortimer, S.R. ; Putten, W.H. van der - \ 2005
Ecology Letters 8 (2005)12. - ISSN 1461-023X - p. 1283 - 1290.
functional diversity - natural communities - ecosystem processes - desert rodents - succession - rules - restoration - ecology - stability - fields
Despite decades of research, it remains controversial whether ecological communities converge towards a common structure determined by environmental conditions irrespective of assembly history. Here, we show experimentally that the answer depends on the level of community organization considered. In a 9-year grassland experiment, we manipulated initial plant composition on abandoned arable land and subsequently allowed natural colonization. Initial compositional variation caused plant communities to remain divergent in species identities, even though these same communities converged strongly in species traits. This contrast between species divergence and trait convergence could not be explained by dispersal limitation or community neutrality alone. Our results show that the simultaneous operation of trait-based assembly rules and species-level priority effects drives community assembly, making it both deterministic and historically contingent, but at different levels of community organization
Plant species diversity, plant biomass and responses of the soil community on abandoned land across Europe: idiosyncracy or above-belowground time lags
Hedlund, K. ; Santa Regina, I. ; Putten, W.H. van der; Leps, J. ; Díaz, T. ; Korthals, G.W. ; Lavorel, S. ; Brown, V.K. ; Gormsen, D. ; Mortimer, S.R. ; Rodríguez Barrueco, C. ; Roy, J. ; Smilauer, P. ; Smilauerová, M. ; Dijk, C. van - \ 2003
Oikos 103 (2003). - ISSN 0030-1299 - p. 45 - 58.
experimental grassland ecosystems - trophic-level biomasses - fatty-acid analysis - microbial communities - food-web - agricultural land - arable land - set-aside - biodiversity - productivity
We examined the relationship between plant species diversity, productivity and the development of the soil community during early secondary succession on former arable land across Europe. We tested the hypothesis that increasing the initial plant species diversity enhances the biomass production and consequently stimulates soil microbial biomass and abundance of soil invertebrates. We performed five identical field experiments on abandoned arable land in five European countries (CZ, NL, SE, SP and UK) which allowed us to test our hypothesis in a range of climate, soil and other environmental factors that varied between the experimental sites. The initial plant diversity was altered by sowing seed mixtures of mid-successional grassland species with two or five grass species, one or five legumes and one or five forbs. The results of low and high sown diversity treatments were compared with plots that were naturally colonized by species present in the seed bank. In three out of the five field sites, there was no correlation between plant species number and plant biomass production, one site had a positive and the other a negative relation. Treatments with a high diversity seed mixture had a higher biomass than the naturally colonized plots. However, there was no significant difference between high and low sown diversity plots at four out of five sites. The three-year study did not give any evidence of a general bottom-up effect from increased plant biomass on biomass of bacteria, saprophytic fungi or abundance of microarthropods. The biomass of arbuscular mycorrhizal was negatively related to plant biomass. The abundance of nematodes increased after abandonment and was related to plant biomass at four sites. Our results support the hypothesis that plant species diversity may have idiosyncratic effects on soil communities, even though studies on a longer term could reveal time lags in the response to changes in composition and biomass production of plant communities.