The relative importance of influence factors to field soil respiration is shifted by straw incorporations: comprehensive analysis of the seasonal variability

Abstract

Understanding the effects of agricultural managements (e.g., straw incorporation) on soil respiration (Rs) and its temperature sensitivity (Q10) is crucial for accurate estimation of the soil carbon sequestration potential under an increasing-temperature scenario in the future. However, how the influence drivers regulate Rs and whether their relative roles are changed under different agricultural practices remain unexplored. Static chambers were used to monitor field CO2 flux in one growing season for a straw return experiment, which had been amended with different amounts of straw (CK, no straw return; S4, straw amendment at 4000 kg ha−1; and S8, straw amendment at 8000 kg ha−1) for five consecutive years. Our monitoring showed that Rs was elevated with intensified use of straw and confirmed soil temperature, soil moisture, and rainfall were important seasonal drivers of Rs. Moreover, the lower coefficient of variations (CV) for each series of treatments of Rs was detected at the vigorous growth stage of the crop, implying the biotic factor of crop roots might also exert a role simultaneously. Straw addition tended to reduce Q10, probably due to the fact that the microbial degradation of SOC in S4 and S8 was less sensitive to temperature change. Interestingly, the Q10 of S4 but not S8 was significantly smaller (P < 0.05) than that of CK as the reduced magnitude of Q10 for S4 was more profound. This result corresponded with more proportional growth of crop root of S8 than S4. By comprehensively analyzing the seasonal variability of our data set, we inferred that for S8, the negative impact of straw incorporation on Q10 would be more offset by upregulated root metabolism. Although additional works were needed to corroborate and specify this explanation, present research highlighted the abiotic and biotic factors should both be incorporated to analyze the underlying mechanisms responsible for the seasonal dynamics of soil C emissions under agricultural managements.