Litter decay controlled by temperature, not soil properties, affecting future soil carbon

Abstract

Widespread global changes, including rising atmospheric CO 2 concentrations, climate warming and loss of biodiversity, are predicted for this century; all of these will affect terrestrial ecosystem processes like plant litter decomposition. Conversely, increased plant litter decomposition can have potential carbon-cycle feedbacks on atmospheric CO 2 levels, climate warming and biodiversity. But predicting litter decomposition is difficult because of many interacting factors related to the chemical, physical and biological properties of soil, as well as to climate and agricultural management practices. We applied 13 C-labelled plant litter to soil at ten sites spanning a 3500-km transect across the agricultural regions of Canada and measured its decomposition over five years. Despite large differences in soil type and climatic conditions, we found that the kinetics of litter decomposition were similar once the effect of temperature had been removed, indicating no measurable effect of soil properties. A two-pool exponential decay model expressing undecomposed carbon simply as a function of thermal time accurately described kinetics of decomposition. (R 2 = 0.94; RMSE = 0.0508). Soil properties such as texture, cation exchange capacity, pH and moisture, although very different among sites, had minimal discernible influence on decomposition kinetics. Using this kinetic model under different climate change scenarios, we projected that the time required to decompose 50% of the litter (i.e. the labile fractions) would be reduced by 1-4 months, whereas time required to decompose 90% of the litter (including recalcitrant fractions) would be reduced by 1 year in cooler sites to as much as 2 years in warmer sites. These findings confirm quantitatively the sensitivity of litter decomposition to temperature increases and demonstrate how climate change may constrain future soil carbon storage, an effect apparently not influenced by soil properties.

The spatial patterns of litter turnover time in Chinese terrestrial ecosystems

“…For example, mean annual temperature (MAT) and mean annual precipitation (MAP) explained 38% of the variance in litter decomposition for 11 litter species at different forest sites across Canada (Moore et al, 1999). Additionally, Gregorich et al (2016) reported that the time required for litter decomposition decreased by 1 and 2 years in the cool zone and warm zone, respectively. This relationship between climate and litter has been incorporated into ecosystem C cycle and terrestrial ecological models, and the litter turnover times of different litter tissues (leaves, stems and roots) are usually simulated using soil moisture and air temperature.…”

“…Frøseth and Bleken (2015) reported that litter turnover time was higher in sandy compared to clay soil. Gregorich et al (2016) concluded that soil properties, such as soil nutrients, had little influence on litter turnover compared with soil moisture and temperature. It is clear that complex interconnections exist among these factors.…”

Temperature response of plant residue and soil organic matter decomposition in soil from different depths

“…The decomposition of plant residue and soil organic matter (SOM) is important because of its feedback to the concentration of atmospheric greenhouse gas. Temperature is one of the main controllers of decomposition (Curiel Yuste et al, 2007;Gregorich et al, 2016) and is expected to change and become more variable in the future (Hansen et al, 2006). Prediction of the response of SOM decomposition to temperature is difficult because of the influences of many interwoven and fluctuating factors; these include the availability and concentration of substrates (Davidson & Janssens, 2006;German et al, 2011), the quality or complexity of the organic matter (substrate) (Giardina & Ryan, 2000;Schmidt et al, 2011), and the activity and composition of the microbial community (Strickland et al, 2009).…”

Spatial distribution of the litter carbon stock in the Cerrado biome in Minas Gerais state, Brazil

“…The litter is a terrestrial ecosystem that is fundamental for nutrients cycling and supply carbon to the soils (Gregorich et al, 2016). Studies have demonstrated that its removal, which mostly occurs by land-use changes and burning, causes negative impacts on the soil quality properties, like soil bulk density, soil organic matter and microbiological diversity (Tanner;Sheldrake;Turner, 2016).…”