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

Soil respiration (R_s) 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 (M_m) field. A two-year field experiment was conducted to investigate the responses of R_s and its components, including respiration from roots (R_r) and soil free-living microbes (R_m), to soil temperature (ST) and water content (SWC) amidst environmental changes. Results showed that M_m significantly stimulated the cumulative CO₂ emissions of R_m (CE-R_m) and R_r mainly due to the prominent increase of them in rows without plastic film in M_m. This was attributed to more favorable microclimatic conditions under M_m 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 R_r and R_m variation than solely ST or SWC. M_m considerably increased the temperature sensitivity of R_m and the water sensitivities of R_m and R_r 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 M_m could sustain crop yield without increasing environmental impacts because there was no significant difference for CE-R_m per unit of grain yield produced between M₀ and M_m.