Effects of plastic film mulching on soil respiration and its sensitivity to temperature and water content

Soil respiration (Rs) and its temperature and water sensitivities play a vital role in understanding the processes and mechanisms of carbon (C) cycling in half plastic film mulching (Mm) field. A two-year field experiment was conducted to investigate the responses of Rs and its components, including respiration from roots (Rr) and soil free-living microbes (Rm), to soil temperature (ST) and water content (SWC) amidst environmental changes. Results showed that Mm significantly stimulated the cumulative CO2 emissions of Rm (CE-Rm) and Rr mainly due to the prominent increase of them in rows without plastic film in Mm. This was attributed to more favorable microclimatic conditions under Mm for microbes and roots growth, identified by improved SWC, dissolved organic C (DOC) and total nitrogen (DTN), microbial biomass C (MBC) and nitrogen (MBN) contents, enzyme activities and functional genes abundances associated with C degradation. The combination of ST and SWC can help to more accurately predict the seasonal Rr and Rm variation than solely ST or SWC. Mm considerably increased the temperature sensitivity of Rm and the water sensitivities of Rm and Rr probably due to the improved soil C and nitrogen substrates for microbes and roots indicated by growing DOC and DTN contents. This study indicated that the Mm could sustain crop yield without increasing environmental impacts because there was no significant difference for CE-Rm per unit of grain yield produced between M0 and Mm.