Warming and straw application increased soil respiration during the different growing seasons by changing crop biomass and leaf area index in a winter wheat-soybean rotation cropland

Warming and straw application are two important factors that may influence soil respiration. Investigations of the different effects of warming and straw application on soil respiration during different crop growing seasons are crucial to understand the soil carbon (C) cycles in croplands under future climate scenarios. A two-year field experiment was performed in a winter wheat-soybean cropland in subtropical east China to investigate the different effects of 1.4 degrees C warming and straw application on soil respiration. There were two main plots, i.e., warming and unwarmed treatments, with three straw application levels: no straw applied, low straw application (6 t ha(-1)) and high straw application (12 t ha(-1)) in each treatment. Seasonal variations in soil respiration, soil temperature, soil moisture and leaf area index (LAI) were measured. The results indicated that both warming and straw application significantly increased soil respiration during each growing season. Compared with the unwarmed treatment, warming increased soil respiration by 24.7%, 12.1%, and 12.6% in the plots with no straw applied, low straw application and high straw application, respectively, during the 2017-2019 rotation period. The mean soil respiration during the two-year rotation was significantly (P < 0.01) correlated with mot biomass, stem and shoot biomass, grain yield, and LAI. The soil temperature, moisture and LAI-based model accounted for 57.9%-69.1% of the seasonal variation in soil respiration in all treatments. The positive effects of warming and straw application on soil respiration were related more to the variations in crop biomass and LAI than those in grain yield.