Effects of shrubs and precipitation on spatial-temporal variability of soil temperature in microhabitats induced by desert shrubs

摘要

Soil temperatures at 0, 5, 10 and 20 cm depths were monitored continuously at different microhabitats (beneath shrub canopy (BSC); bare intershrub spaces (BIS)) induced by xerophytic shrub (Caragana korshinskii Kom.) canopy, respectively. We mainly aimed to assess the effects of shrub canopy and precipitation on the spatial-temporal variability of soil temperature. Results indicate that both precipitation and vegetation canopy significantly affect soil temperature. In clear days, soil temperatures within the BSC area were significantly lower than in the BIS at the same soil depth due to shading effects of shrub canopy. Diurnal variations of soil temperature show a unimodal sinusoidal curve. The amplitude of soil temperature tended to decrease and a hysteresis of diurnal maximum soil temperature existed at deeper soil layers. Vertical fluctuations of soil temperature displayed four typical curves. In the nighttime (approximately from sunset to sunrise), surface temperature within the BSC area was higher than in the BIS. In rainy days, however, soil temperatures were affected mainly by precipitation and the shrub canopy had a negligible effect on soil temperature, and little difference in soil temperature at the same soil depth was found between the BSC area and in the BIS. Diurnal variations in soil temperature decreased exclusively as rainfall continued and the vertical fluctuations of soil temperature show an increased tendency with increasing soil depth.