Temperature and soil organic matter decomposition rates - synthesis of current knowledge and a way forward

Abstract

The response of soil organic matter (OM) decomposition to increasing temperature is a critical aspect of ecosystem responses to global change. The impacts of climate warming on decomposition dynamics have not been resolved due to apparently contradictory results from field and lab experiments, most of which has focused on labile carbon with short turnover times. But the majority of total soil carbon stocks are comprised of organic carbon with turnover times of decades to centuries. Understanding the response of these carbon pools to climate change is essential for forecasting longer-term changes in soil carbon storage. Herein, we briefly synthesize information from recent studies that have been conducted using a wide variety of approaches. In our effort to understand research to-date, we derive a new conceptual model that explicitly identifies the processes controlling soil OM availability for decomposition and allows a more explicit description of the factors regulating OM decomposition under different circumstances. It explicitly defines resistance of soil OM to decomposition as being due either to its chemical conformation (quality) or its physico-chemical protection from decomposition. The former is embodied in the depolymerization process, the latter by adsorption/desorption and aggregate turnover. We hypothesize a strong role for variation in temperature sensitivity as a function of reaction rates for both. We conclude that important advances in understanding the temperature response of the processes that control substrate availability, depolymerization, microbial efficiency, and enzyme production will be needed to predict the fate of soil carbon stocks in a warmer world.

Microbial community structure mediates response of soil C decomposition to litter addition and warming

“…The amount of soil-derived WEOC also partially reflected the extent of mineralization, as the pre-incubated litter treatment had the highest content of soil-derived WEOC and the greatest soil-C mineralization. However, a combination of increased desorption but also increased mineralization of soil-derived WEOC with temperature may have masked any response to temperature (Bengtson and Bengtsson, 2007;Conant et al, 2011). Similar to other studies, these data suggest that the mineralization of C (but not necessarily biomass formation) can be related to the amount of WEOC produced via enzymatic decomposition of insoluble OM (Marschner and Bredow, 2002;Kalbitz et al, 2003).…”

Critical evaluation of a new passive exchange-meter for assessing multimedia fate of persistent organic pollutants at the air-soil interface

“…The litter in the gap, unlike that under the canopy, experienced direct exposure to solar radiation which resulted in more rapid evaporation of water and consistently significant lower litter moisture (Table 1). This determines lower bulk heat capacity and slower OM turn over in the gap deployed litter compared to the understory litter (Conant et al, 2011). Low bulk heat capacity may have implication on contaminant fugacity by means of fugacity dependence on temperature, explaining higher volatilization in the gap as a result of higher maxima in litter temperature.…”

Peat decomposability in managed organic soils in relation to land use, organic matter composition and temperature

“…In contrast to other studies on unmanaged organic soils reporting no trend or increasing Q 10 values with depth (Scanlon and Moore, 2000; Wang et al, 2010;Hardie et al, 2011;Hilasvuori et al, 2013), the cropland and grassland profiles in our study had a lower Q 10 below the 60 cm depth. Various studies on SOM decomposition used Q 10 values as an indicator of SOM recalcitrance (Hogg et al, 1992;Biasi et al, 2005;Davidson and Janssens, 2006;Conant et al, 2008Conant et al, , 2011Hartley and Ineson, 2008;Hilasvuori et al, 2013). Considering that the presence of labile crop residues would decrease Q 10 in the topsoil rather than in the subsoil, the higher topsoil Q 10 may be explained by an extended accumulation of recalcitrant moieties.…”