Stoichiometric plasticity of microbial communities is similar between litter and soil in a tropical rainforest

Nicolas Fanin,Nathalie Fromin,Stephan Hättenschwiler,Sandra Barantal

doi:10.1038/s41598-017-12609-8

Abstract

Heterotrophic microorganisms are commonly thought to be stoichiometrically homeostatic but their stoichiometric plasticity has rarely been examined, particularly in terrestrial ecosystems. Using a fertilization experiment in a tropical rainforest, we evaluated how variable substrate stoichiometry may influence the stoichiometry of microbial communities in the leaf litter layer and in the underlying soil. C:N:P ratios of the microbial biomass were higher in the organic litter layer than in the underlying mineral soil. Regardless of higher ratios for litter microbial communities, C, N, and P fertilization effects on microbial stoichiometry were strong in both litter and soil, without any fundamental difference in plasticity between these two communities. Overall, N:P ratios were more constrained than C:nutrient ratios for both litter and soil microbial communities, suggesting that stoichiometric plasticity arises because of a decoupling between C and nutrients. Contrary to the simplifying premise of strict homeostasis in microbial decomposers, we conclude that both litter and soil communities can adapt their C:N:P stoichiometry in response to the stoichiometric imbalance of available resources.

Highlights

The decomposition of organic material is commonly considered as a continuous process from freshly produced – mostly plant-derived – litter to soil organic matter (SOM), with increasing turnover times the older the material gets
By assessing how substrate stoichiometry and its alteration through fertilization affect the C:N:P stoichiometry of microbes, this study aims to improve our understanding of the stoichiometric plasticity of microbial communities in terrestrial ecosystems
Substrate stoichiometry varied from 582:19:1 to 1943:60:1 in the litter compared to 109:8:1 to 229:14:1 in the soil

Summary

Introduction

The decomposition of organic material is commonly considered as a continuous process from freshly produced – mostly plant-derived – litter to soil organic matter (SOM), with increasing turnover times the older the material gets. Despite experimental fertilization was shown to influence the C:N:P ratios of plant tissues[10], the question of how substrate stoichiometry and its alteration affect the stoichiometry of microbial communities along the litter-soil continuum remains poorly studied. We used a fully factorial C, N and P fertilization experiment in a tropical rainforest to compare the stoichiometric plasticity of microbial communities in the litter layer to that in the underlying soil. Because litter microbial communities grow on substrates with greater stoichiometric imbalance compared to those in the soil[5], we hypothesized that microbial communities present wider biomass C:N:P ratios in the litter layer than in the soil (H1). Based on the greater range and variability of C:N:P ratios of leaf litter compared to SOM11, we hypothesized that litter communities are stoichiometrically more plastic By assessing how substrate stoichiometry and its alteration through fertilization affect the C:N:P stoichiometry of microbes, this study aims to improve our understanding of the stoichiometric plasticity of microbial communities in terrestrial ecosystems

Objectives

Methods

Results

Conclusion