Linking temperature sensitivity of soil CO₂ release to substrate, environmental, and microbial properties across alpine ecosystems

Abstract

Our knowledge of fundamental drivers of the temperature sensitivity (Q10) of soil carbon dioxide (CO2) release is crucial for improving the predictability of soil carbon dynamics in Earth System Models. However, patterns and determinants of Q10 over a broad geographic scale are not fully understood, especially in alpine ecosystems. Here we addressed this issue by incubating surface soils (0–10 cm) obtained from 156 sites across Tibetan alpine grasslands. Q10 was estimated from the dynamics of the soil CO2 release rate under varying temperatures of 5–25°C. Structure equation modeling was performed to evaluate the relative importance of substrate, environmental, and microbial properties in regulating the soil CO2 release rate and Q10. Our results indicated that steppe soils had significantly lower CO2 release rates but higher Q10 than meadow soils. The combination of substrate properties and environmental variables could predict 52% of the variation in soil CO2 release rate across all grassland sites and explained 37% and 58% of the variation in Q10 across the steppe and meadow sites, respectively. Of these, precipitation was the best predictor of soil CO2 release rate. Basal microbial respiration rate (B) was the most important predictor of Q10 in steppe soils, whereas soil pH outweighed B as the major regulator in meadow soils. These results demonstrate that carbon quality and environmental variables coregulate Q10 across alpine ecosystems, implying that modelers can rely on the “carbon‐quality temperature” hypothesis for estimating apparent temperature sensitivities, but relevant environmental factors, especially soil pH, should be considered in higher‐productivity alpine regions.

Larger Q10 of carbon decomposition in finer soil particles does not bring long‐lasting dependence of Q10 on soil texture

“…Ding et al . () found that Q 10 was negatively correlated with sand content after 10 days of pre‐incubation for soils at 156 grassland sites across the Tibetan Plateau. However, Wei et al .…”

“…If C in finer soil particles has a larger Q 10 , C cycling in finer‐textured soils might be more sensitive to climate warming, and vice versa . Although several studies have explored the relation between Q 10 and soil texture (Hamdi et al ., ; Ding et al ., ), the outcome is elusive.…”

Carbon quality and soil microbial property control the latitudinal pattern in temperature sensitivity of soil microbial respiration across Chinese forest ecosystems

“…The magnitude and direction of the positive feedback between the global C cycle and climate warming strongly depend on the temperature sensitivity ( Q 10 ) of Rs (Davidson & Janssens, ; Heimann & Reichstein, ). Variations in Rs across different climatic conditions and soil types were comprehensively investigated (Colman & Schimel, ; Ding et al., ; Fierer, Colman, Schimel, & Jackson, ; Liu et al., ; Peng, Piao, Wang, Sun, & Shen, ). However, these variations remain controversial because of the large spatial heterogeneity in the decomposability of soil organic matter (Schmidt, Torn, Abiven, Dittmar, & Guggenberger, ).…”

“…In recent decades, the Q 10 of Rs has gained increasing concerns, and is strongly affected by the incubation temperature (Craine, Spurr, McLauchlan, & Fierer, ; Hamdi, Moyano, Sall, Bernoux, & Chevallier, ), C quality (Sihi, Inglett, & Inglett, ; Xu, Luo, & Zhou, ), and soil microbial characteristics (Ding et al., ; Karhu et al., ; Thiessen, Gleixner, Wutzler, & Reichstein, ). However, the relative importance of these factors in the regulation of Q 10 is difficult to quantify because they often interact with each other (Colman & Schimel, ; Fierer et al., ).…”

Regional variation in the temperature sensitivity of soil organic matter decomposition in China's forests and grasslands

“…Using a large-scale incubation experiment, Colman & Schimel (2013) found that soil microbial biomass was the most important factor explaining the spatial variation of soil microbial respiration in North America, while climate and substrate only exerted slight indirect effects through their impacts on microbial biomass. Recently, a study conducted under varying temperatures of 5-25°C demonstrated that precipitation was the best predictor of soil microbial respiration rates in the alpine steppes of China (Ding et al, 2016). In previous decades, the C quality temperature (CQT) hypothesis was proposed to explain the relationship between SOM decomposition and soil substrate quality across different ecosystems.…”