Tradeoff between the Conservation of Soil C Stocks and Vegetation Productivity in Temperate Grasslands

Caroline Kohler,Jean-Bernard Cliquet,Katja Klumpp,Annette Morvan-Bertrand,Servane Lemauviel-Lavenant

doi:10.3390/agronomy10071024

Abstract

Grassland management affects ecosystem services such as the conservation of C stocks. The aim of this study was to analyze the relation between vegetation production and soil C stocks for a set of seven temperate grasslands of various productivity levels. We estimated vegetation production directly through measurements of aboveground biomass (>5 cm), stubble and root biomass, and indirectly via plant community functioning. Soil C stocks were measured for bulk soil (organic C, SOC) and hot-water-extractable C (HWC) of topsoil. Plant community functioning was characterized by community-weighted mean (CWM) traits and functional diversity index. Results show a negative relation between biomass production and SOCstock. The tradeoff between productivity and SOCstock could be linked to plant community functioning and particularly Leaf Dry Matter content (LDMCCWM) which appeared to be the most relevant descriptor of plant community functioning. High SOCstock could be associated to low productivity, conservative strategy (high LDMCCWM), low soil labile C content and grassland age. Our results show a strong direct effect of management and grassland age on plant community, which in turn affects plant tissue quality and subsequent organic matter mineralization. Old permanent grasslands appeared less productive but represent an occasion for C storage and thus global change mitigation.

Highlights

Grasslands cover about 20% of the total area in Europe [1] where most of the area is dedicated to feed livestock
The present study focused on the relationship between two ecosystem services (ES), namely conservation of C stocks and grassland productivity, through the analysis of plant community functioning
As ES provision does vary with management and with local environmental drivers [48], we examined seven grassland fields within the same pedoclimatic, differing in ages since last seeding and management practices with respect to C exports and fertilization

Summary

Introduction

Grasslands cover about 20% of the total area in Europe [1] where most of the area is dedicated to feed livestock. Grasslands play a key role in forage provision, but they deliver a number of ecosystem services (ES) [2], including the regulation of air and soil quality, especially carbon (C) sequestration [3,4]. Grasslands have a high potential to mitigate climate change through C sequestration [5]. Around 12% of the global terrestrial C pool is located in temperate grasslands (calculated from [6]). C input mainly results from CO2 fixation by plants and C output is the result of the release of CO2 into the atmosphere by the plant and micro-organism respiration, the volatilization of organic compounds and the leaching of dissolved organic C [7]. In managed grasslands, a portion of the C output is due to the export of biomass by grazing or mowing

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