Warming increases soil respiration in a carbon-rich soil without changing microbial respiratory potential

Abstract

Abstract. Increases in global temperatures due to climate change threaten to tip the balance between carbon (C) fluxes, liberating large amounts of C from soils. Evidence of warming-induced increases in CO2 efflux from soils has led to suggestions that this response of soil respiration (RS) will trigger a positive land C–climate feedback cycle, ultimately warming the Earth further. Currently, there is little consensus about the mechanisms driving the warming-induced RS response, and there are relatively few studies from ecosystems with large soil C stores. Here, we investigate the impacts of experimental warming on RS in the C-rich soils of a Tasmanian grassy sedgeland and whether alterations of plant community composition or differences in microbial respiratory potential could contribute to any effects. In situ, warming increased RS on average by 28 %, and this effect was consistent over time and across plant community composition treatments. In contrast, warming had no impact on microbial respiration in incubation experiments. Plant community composition manipulations did not influence RS or the RS response to warming. Processes driving the RS response in this experiment were, therefore, not due to plant community effects and are more likely due to increases in below-ground autotrophic respiration and the supply of labile substrate through rhizodeposition and root exudates. CO2 efflux from this high-C soil increased by more than a quarter in response to warming, suggesting inputs need to increase by at least this amount if soil C stocks are to be maintained. These results indicate the need for comprehensive investigations of both C inputs and losses from C-rich soils if efforts to model net ecosystem C exchange of these crucial, C-dense systems are to be successful.

Determination of Δc13 and Δc18 Isotope Ratios to Predict Carbon-Water Relationship in Different Forest Stands in Yenice Forest Hot Spot

“…However, over larger spatio-temporal scales, plant activity and other factors may become increasingly important. Therefore, taking advantage of plant-soil relationships in further studies may help to accurately represent seasonal variation in plant C allocation among different functional groups, by modelling regional or global scales over longer time scales [42]. Climate change forecasts in Europe are unanimous in predicting significant warming for every season.…”

Choice of Forecast Scenario Impacts the Carbon Allocation at the Same Global Warming Levels

“…There are several possible explanations for this slowdown of uptake. It might be that the soil respiration increases due to warming more than carbon uptake increase due to photosynthetic uptake (Nyberg and Hovenden, 2020) or that nitrogen limitation progressively limiting photosynthetic uptake (Ågren et al, 2012). Alternatively, the changing climate may impact vegetation growth and photosynthetic uptake via droughts and warming, which moves plants outside the most efficient temperatures for photosynthesis.…”

Twenty Years of Progress, Challenges, and Opportunities in Measuring and Understanding Soil Respiration

“…A second category of manipulation experiments has aimed to change soils' in situ environmental conditions through heating, drought or water additions, fertilization, or CO 2 enrichment. Soil heating experiments have examined changes in Rs magnitude and sources, the durability of any changes, and how they are linked with for example, changes belowground allocation (Giasson et al., 2013) and/or the soil microbial community (Nyberg & Hovenden, 2020; Schindlbacher et al., 2011). For example, soil warming can induce modifications in microbial activity, facilitating thermal adaptation and influencing SOC decomposition rates, ultimately impacting Rs (Bradford et al., 2008).…”