Effects of plant diversity, functional group composition, and fertilization on soil microbial properties in experimental grassland.
BACKGROUND
Loss of biodiversity and increased nutrient inputs are two of the most crucial anthropogenic factors driving ecosystem change. Although both received considerable attention in previous studies, information on their interactive effects on ecosystem functioning is scarce. In particular, little is known on how soil biota and their functions are affected by combined changes in plant diversity and fertilization.


RESULTS
We investigated the effects of plant diversity, functional community composition, and fertilization on the biomass and respiration of soil microbial communities in a long-term biodiversity experiment in semi-natural grassland (Jena Experiment). Plant species richness enhanced microbial basal respiration and microbial biomass, but did not significantly affect microbial specific respiration. In contrast, the presence of legumes and fertilization significantly decreased microbial specific respiration, without altering microbial biomass. The effect of legumes was superimposed by fertilization as indicated by a significant interaction between the presence of legumes and fertilization. Further, changes in microbial stoichiometry (C-to-N ratio) and specific respiration suggest the presence of legumes to reduce N limitation of soil microorganisms and to modify microbial C use efficiency.


CONCLUSIONS
Our study highlights the role of plant species and functional group diversity as well as interactions between plant community composition and fertilizer application for soil microbial functions. Our results suggest soil microbial stoichiometry to be a powerful indicator of microbial functioning under N limited conditions. Although our results support the notion that plant diversity and fertilizer application independently affect microbial functioning, legume effects on microbial N limitation were superimposed by fertilization, indicating significant interactions between the functional composition of plant communities and nutrient inputs for soil processes.
J.F. Blumenbach Institute of Zoology and Anthropology, Georg August University Göttingen, Göttingen, Germany.
Tanja
T
Strecker
INRA, UMR1347 Agroécologie, Dijon, France; ETH Zurich, Zurich, Switzerland.
Romain L
RL
Barnard
ETH Zurich, Zurich, Switzerland; Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
Pascal A
PA
Niklaus
Chair of Geobotany, Faculty of Biology, University of Freiburg, Freiburg, Germany.
Michael
M
Scherer-Lorenzen
Institute for Biology, University Leipzig, Leipzig, Germany; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.
Alexandra
A
Weigelt
J.F. Blumenbach Institute of Zoology and Anthropology, Georg August University Göttingen, Göttingen, Germany.
Stefan
S
Scheu
Institute for Biology, University Leipzig, Leipzig, Germany; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.
Nico
N
Eisenhauer
D044822:Biodiversity; D018533:Biomass; D017753:Ecosystem; D005308:Fertilizers; D005858:Germany; D065948:Grassland; D010944:Plants; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
D005308:Fertilizers; D012987:Soil