Interactive Effects of Climate Warming and Management on Grassland Soil Respiration Partitioning

Grassland ecosystems are important for the provision of food, fuel and fibre. They represent globally important carbon (C) reservoirs that are under pressure from intensive management and ongoing climate change. How these drivers of change will interact to affect grassland soil C and nitrogen (N) cycling and heterotrophic and autotrophic respiration remains uncertain. Roots and mycelia in grassland soil are important regulators of ecosystem functioning and likely to be an influential determinant of CO2 fluxes responses to global change. The aim of this study was to investigate the interactive effect of climate warming and grassland management on soil respiration originating from roots rhizosphere, mycelia and free-living microbes. The experiment used a block design to measure the interactive effects of warming, nitrogen addition, aboveground biomass (AGB) removal on belowground respiration in a temperate grassland ecosystem. An in-growth core method using cores with different mesh sizes was used to partition belowground respiration due to its simplicity of design and efficacy. We found that basal respiration (free-living microorganisms) was the highest (58.5% of the total emissions), followed by that from roots (22.8%) and mycelia (18.7%) across all treatments. Warming reduced basal respiration whilst AGB removal increased it. An antagonistic interaction between warming and nitrogen addition reduced root respiration, and a three-way interaction between warming, nitrogen addition and AGB removal affected mycelial respiration. The results show different contributions of belowground biota to soil respiration, and how interactions between climate change and grassland management may influence effects on soil respiration.