Title:Effect of Precipitation Variation on Soil Respiration in Rain-Fed Winter Wheat Systems on the Loess Plateau, China

Authors:Houkun Chu, Hong Ni, Jingyong Ma and Yuying Shen*

Journal: International Journal of Environmental Research and Public Health

Impact factor: IF₂₀₂₁= 3.390

Abstract:Global climate change has aggravated the hydrological cycle by changing both the amount and distribution of precipitation, this is especially notable in semiarid Loess Plateau. How these precipitation variations have affected soil carbon (C) emission by the agroecosystems is still unclear. Here, to evaluate the effects of precipitation variation on soil respiration (R_s), a field experiment (from 2019 to 2020) was conducted with 3 levels of manipulation, including ambient precipitation (CK), 30% decreased precipitation (P_-30), and 30% increased precipitation (P₊₃₀) in rain-fed winter wheat (Triticum aestivum L.) agroecosystems on the Loess Plateau, China. Results showed that the average R_s in P_-30 treatment was significantly higher than those in the CK and P₊₃₀ treatments (P < 0.05), and the cumulative CO₂ emission were 406.37, 372.58 and 383.59 g C m^-2, respectively. Seasonal responses of R_s to the soil volumetric moisture content (VWC) were affected by the different precipitation treatments. R_s was quadratically correlated with the VWC in the CK and P₊₃₀ treatments, and the threshold of the optimal VWC for R_s was approximately 16.06-17.07%. But, R_s was a piecewise linear function of the VWC in the P_-30 treatment. The synergism of soil temperature (T_s) and VWC can better explain the variation in soil respiration in the CK and P_-30 treatments. However, an increase in precipitation led to the decoupling of the R_s responses to T_s. The temperature sensitivity of respiration (Q₁₀) varied with precipitation variation. Q₁₀ was positive correlated with seasonal T_s in the CK and P₊₃₀ treatments, but exhibited a negative polynomial correlation with seasonal T_s in the P_-30 treatment. R_s also exhibited diurnal clockwise hysteresis loops with T_s in the three precipitation treatments, and the seasonal dynamics of the diurnal lag time were significantly negatively correlated with the VWC. Our study highlighted that understanding the synergistic and decoupled responses of R_s and Q₁₀ to T_s and VWC and the threshold of the change in response to the VWC under precipitation variation scenarios can benefit the prediction of future C balances in agroecosystems in semiarid regions under climate change.

Linkage: https://doi.org/10.3390/ijerph19116915 (1).pdf