Effects of Plant Diversity, Functional Group Composition, and Fertilization on Soil Microbial Properties in Experimental Grassland

Tanja Strecker,Romain L Barnard,Michael Scherer-Lorenzen,Nico Eisenhauer,Stefan Scheu,Alexandra Weigelt,Pascal A Niklaus,Andrew Hector

doi:10.1371/journal.pone.0125678

Abstract

BackgroundLoss 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.Methodology/Principal FindingsWe 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/SignificanceOur 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.

Highlights

Loss of biodiversity and increased nutrient inputs are two of the most crucial anthropogenic impacts on Earth’s biosphere [1,2]
Plant diversity effects on soil microbial respiration and MBCSIR remained significant even if accounting for the effect of aboveground plant biomass or soil water content, indicating that plant diversity effects on soil microbial properties cannot be fully explained by aboveground plant biomass production and soil water content
Our results underline the importance of plant functional groups, in particular legumes, for soil microbial functioning and stoichiometry

Summary

Introduction

Loss of biodiversity and increased nutrient inputs are two of the most crucial anthropogenic impacts on Earth’s biosphere [1,2]. Many studies have investigated the effects of species loss and eutrophication on ecosystem functioning; usually these factors have been considered in isolation. Positive effects of species diversity on plant productivity in turn increase the input of organic carbon (C) to the soil, e.g., by producing more root exudates and shoot and root litter, thereby enhancing resource supply to decomposers [11,12]. Loss of biodiversity and increased nutrient inputs are two of the most crucial anthropogenic factors driving ecosystem change. Both received considerable attention in previous studies, information on their interactive effects on ecosystem functioning is scarce. Little is known on how soil biota and their functions are affected by combined changes in plant diversity and fertilization

Methods

Results

Discussion

Conclusion