[Spatiotemporal distribution pattern of soil temperature in forest gap of Pinus koraiensis-dominated broadleaved mixed forest in Xiao Xing'an Mountains].

ABSTRACT

By using grid and transect methods, measurement plots were established in forest gap of Pinus koraiensis-dominated broadleaved mixed forest in Xiao Xing'an Mountains, and soil surface thermometer and bended-tube thermometer were placed at each plot. The soil surface temperature, its maximum and minimum temperature, and the temperature at 5, 10, 15, and 20 cm soil depths were measured from May to September in 2006, aimed to investigate the spatiotemporal distribution pattern of soil temperature in the forest gap in study area. The high-value region of soil surface temperature in forest gap was not at gap center, but had an apparent diurnal variation, with the sequence of northwestern, northern, and eastern sides of the gap. Within this high-value region, the maximum temperature from high to low was in the time order of 1400, 1200, 1000 and 1600. At any other time, the soil surface temperature in forest gap distributed evenly, with no high-value region appeared. The complexity degree and patch grades of spatial distribution of soil surface temperature were different in months, and their high-value regions were at the north-western and eastern sides of the gap, with an asymmetric distribution. The mean diurnal range of soil surface temperature was bigger in the tree's early and late growth periods (May and September) , but relatively smaller in fast growth period. As for the mean daily and monthly soil temperature at 5, 10, 15, and 20 cm depths, a bimodal behavior was observed in east-west direction. The mean daily temperature in north-south direction exhibited an unapparent single peak behavior, and the mean monthly temperature except in May presented a single peak variation pattern.