Dynamics of soil respiration and its influencing factors at the early stage of ecological restoration of two kinds of climate in earthquake-affected area

ObjectiveSoil respiration rate is one of the important parameters affecting the sensitivity and response pattern of ecosystems to stress, and the ecological restoration process can cause changes in soil respiration rate. To accurately understand the regional carbon cycle characteristics of disaster-affected areas under ecological restoration, it is crucial to study the dynamic changes of soil respiration in disaster areas and their relationship with environmental factors under different ecological restoration modes in different climate regions.

MethodIn order to study the dynamic changes of soil respiration and its relationship with hydrothermal factors during the treatment of damaged ecosystems in the earthquake-affected areas, the demonstration area of ecological restoration of the arid-valley climate region (Weizhou Town, Wenchuan County) and subtropical monsoon climate region (Hanwang Town, Mianzhu City) was selected as the study area, with destroyed and treated area (DTA), natural recovery area (NRA) and undestroyed area (UA) as sample plots. Diurnal and seasonal dynamics of soil respiration rate (R_s), 5 cm deep soil temperature (T₅) and moisture (W₅) and near-surface temperature (T₀) and moisture (W₀) were measured using the LI-8100 soil carbon flux measurement system, precision thermometer and round knife method from September 2015 to September 2016, and analyze the dynamic characteristics of soil respiration and its response to soil temperature and moisture.

Result(1) The highest R_s value of the daily scale appeared at 11:00−15:00, and the lowest value appeared at 10:00 or 18:00. In two climatic regions, the diurnal dynamics of soil respiration showed the tendency of UA > DTA > NRA, and showed obvious single peak curves with certain volatility; seasonal scale R_s was the highest in summer and autumn, and lowest in winter, and R_s showed UA > DTA > NRA in all seasons. (2) When the soil moisture in the arid-valley climate region and the subtropical monsoon climate region were < 27% and > 16%, respectively, soil respiration was mainly regulated by soil temperature; compared with the single-factor models of R_s and T₅ or R_s and W₅, the regression relationship between R_s and T₅ as well as W₅ was better, and the explanatory amount (R²) of T₅ and W₅ to R_s was both increased and was greater than 0.762. (3) The temperature sensitivity coefficients Q₁₀ of DTA, UA, and NRA in the arid-valley climate region were 2.34, 1.95, and 2.78, respectively, and the Q₁₀ values in the subtropical monsoon climate region were 1.99, 1.25, and 2.90, respectively. The performance of NRA was most sensitive to soil temperature changes, followed by DTA, and UA was the least sensitive.

ConclusionCompared with UA, the soil respiration rates of DTA and NRA decreased by 41% and 50%, respectively in the arid-valley climate region, while only decreased by 21% and 23%, respectively in the subtropical monsoon climate region.