Temperature sensitivity of SOM decomposition governed by aggregate protection and microbial communities

Abstract

Temperature sensitivity (Q10) of soil organic matter (SOM) decomposition is a crucial parameter for predicting the fate of soil carbon (C) under global warming. However, our understanding of its regulatory mechanisms remains inadequate, which constrains its accurate parameterization in Earth system models and induces large uncertainties in predicting terrestrial C-climate feedback. Here, we conducted a long-term laboratory incubation combined with a two-pool model and manipulative experiments to examine potential mechanisms underlying the depth-associated Q10 variations in active and slow soil C pools. We found that lower microbial abundance and stronger aggregate protection were coexisting mechanisms underlying the lower Q10 in the subsoil. Of them, microbial communities were the main determinant of Q10 in the active pool, whereas aggregate protection exerted more important control in the slow pool. These results highlight the crucial role of soil C stabilization mechanisms in regulating temperature response of SOM decomposition, potentially attenuating the terrestrial C-climate feedback.

Soil warming increases soil temperature sensitivity in subtropical Forests of SW China

“…Warming treatment can change substrate supplies and microbial activities or communities (Wang et al, 2019; Li et al, 2018). Therefore, soil aggregate protection and microbial communities can also affect the Q 10 values (Qin et al, 2019). In the present study, we focused on warming effects on R S and Q 10 .…”

Warming alters surface soil organic matter composition despite unchanged carbon stocks in a Tibetan permafrost ecosystem

“…Approximately 100 mg of treated soil samples was measured by 13 C NMR on a Bruker BioSpin Avance III 400 MHz WB spectrometer (Bruker BioSpin), which was equipped with a standard bore CPMAS probe of 4 mm. The spin rate was set as 8 kHz, with a 2-ms contact time and a 6-s recycle delay (Qin et al, 2019). For the NMR characterization, spinning side bands were added.…”

Ocean temperature controls kelp decomposition and carbon sink potential

“…Our experiments revealed a signi cant relationship between temperature and kelp detritus decomposition rates across the northern hemisphere, with markedly slower decomposition in cooler northern regions relative to warmer southern regions. Temperature dependence of organic-matter decomposition constitutes an important link between climate change and the global carbon cycle 5 , including in the ocean where there are large actively cycling pools of organic matter 38,39 . There is a widely held view that decomposition rates and carbon turnover are faster at lower latitudes, due to increased microbial activity and metabolic rates of detritivores in warmer climates 8,17,40 .…”

“…Consequently, there has been a strong focus on resolving inorganic carbon (CO 2 ) uptake and primary productivity on global scales 3 . Yet, decomposition rates of organic carbon at the ecosystem scale, which are known to vary with environmental conditions such as temperature e.g., 4,5 , could be equally important in determining the balance between pools of organic and inorganic carbon [6][7][8] . At the land-sea interface, carbon cycling by macroalgae and other macrophytes has recently emerged as an important process by which CO 2 is captured, stored, and potentially sequestered in the ocean 9,10 .…”

“…The dynamics of temperature-decomposition relationships are also complex 17 . Organic matter tends to be remineralized faster in warmer compared to cooler environments, and the temperature-dependent decomposition of carbon has been highlighted as a key source of uncertainty in future global carbon models 5,18,19 . Understanding the environmental drivers underlying spatial variation in carbon turnover is critical because it effectively controls how current rates of carbon cycling could be changed with global warming.…”