Plant community impacts on the structure of earthworm communities depend on season and change with time |
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Authors: | Nico Eisenhauer Alexandru Milcu Holger Bessler Christof Engels |
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Institution: | a Georg-August-University Göttingen, J.F. Blumenbach Institute of Zoology and Anthropology, Berliner Str. 28, 37073 Göttingen, Germany b NERC Centre for Population Biology, Division of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire, UK c Darmstadt University of Technology, Institute of Zoology, Schnittspahnstr. 3, 64287 Darmstadt, Germany d Humboldt University of Berlin, Department of Plant Nutrition and Fertilization, Albrecht-Thaer-Weg 4, 14195 Berlin, Germany e University of Jena, Institute of Ecology, Dornburger Str. 159, 07743 Jena, Germany |
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Abstract: | Declining plant diversity potentially threatens essential ecosystem functions driven by the decomposer community, such as litter decomposition and nutrient cycling. Currently, there is no consensus on the interrelationships between plant diversity and decomposer performance and previous studies highlighted the urgent need for long-term experiments.In the Jena Experiment we investigated the long-term impacts of plant community characteristics on the structure of earthworm communities representing key decomposers in temperate grassland. We repeatedly sampled plots varying in plant species richness (1-16 species), plant functional group richness (1-4 groups), and presence of certain plant functional groups (grasses and legumes) three, four, and six years after establishment of the experiment in spring and autumn.The results show that earthworm performance is essentially driven by the presence of certain plant functional groups via a variety of mechanisms. Plant productivity (root biomass) explained most of the detrimental grass impacts (decrease in earthworm performance), while beneficial legume effects likely were linked to high quality inputs of plant residues (increase in earthworm performance). These impacts depended on the functional group of earthworms with the strongest effects on surface feeding anecic earthworms and minor effects on soil feeding endogeic species. Remarkably, effects of plant community characteristics on the composition and age structure of earthworm communities varied between seasons. Moreover, plant diversity effects reported by a former study decreased and detrimental effects of grasses increased with time.The results indicate that plant community characteristics, such as declining diversity, indeed affect the structure of earthworm communities; however, loss of key plant functional groups is likely to be more important than plant species number per se. However, in frequently disturbed ecosystems plant species richness might be important for the recovery and resilience of belowground functions. Moreover, the results accentuate the importance of long-term repeated measurements to fully appreciate the impacts of plant community composition and diversity on ecosystem properties. Single point observations may be misleading and potentially mask the complexity of above-belowground interrelationships. |
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Keywords: | Anecic earthworms Biodiversity loss Endogeic earthworms Key plant functional groups Long-term experiment Plant functional group richness Plant species richness Seasonality The Jena experiment |
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