Abstract: Soil temperature is an important environmental factor of forest climate, which closely relates to plant growth. To deeply understand the variations of soil temperature in forest is beneficial to reveal the functions of forest ecosystem and to assess the environmental benefit of forest. Our analysis on the observation data of soil temperature within a subtropical evergreen broadleaved forest and in an open area nearby in the Ailao Mountains showed that the diurnal variations of soil temperature within and outside the forest presented a singlepeak curve. Compared with that in nearby open area, the diurnal variation of soil temperature in the forest was presented in shallower depths (less than 20 cm). The depth of the diurnal variation of soil temperature in the forest was deeper in spring and autumn (20 cm) than in summer and winter (15 cm). The soil temperature in the forest was lower than that in the open area at each depth, and the diurnal and annual variations of soil temperature in the forest were smaller than those in the open area. Overall, both the diurnal and the annual variation ranges of soil temperature were larger outside the forest than within the forest.  

Key words: organic matter, budget of nitrogen, phosphorus, potassium, biomass, straw.