Effects of Plastic Mulch on Soil Heat Flux and Energy Balance in a Cotton Field in Northwest China

摘要

Surface energy balance (SEB) is a basic principle for all of the atmospheric circulation models, and surface soil heat flux ( G 0 ) is an important component of energy balance. Plastic mulch is widely used in arid regions and alters land surface processes. In this study, hourly/daily G 0 and SEB over a mulched cotton field were analyzed in Northwest China. The net radiation beneath the mulch was simulated using transmitted down short-wave and down long-wave radiation through the mulch and up short-wave and up long-wave radiation from the soil beneath mulch. The results show that: (1) on the hourly time scale, G 0 in mulched soil is much smaller than that in non-mulched soil, day and night. This implies that mulch prevents energy going into the soil during the daytime and reduces soil heat loss at night. On the daily time scale, G 0 is similar in mulched and non-mulched soil. (2) During the seedling emergence period when the cotton is small, the energy balance closure over mulched soil (0.79) is slightly smaller than that over non-mulched soil (0.81). (3) Comparing to soil temperature in non-mulched soil, there’s a time offset on soil temperature in mulched soil at the same depth, which will bring a hysteresis on G 0 and SEB.