This study seeks a further understanding on climate trends in a subtropical mountain forest, SW China. Air (T_a) and soil temperature (T_s), both in open land (1983–2010) and under a forest canopy (1986–2010), were investigated. Short-term radiation components were also measured simultaneously both in open land and understory to explore the relationships of microclimatic variables. Correlations of T_a and T_s with sunshine hours (S_t) and wind speed (W_s) were also analysed as driving factors of the temperature trends.

The results showed that (1) Understory radiation components were greatly reduced by the forest canopy, showing a strong effect of forest canopy on microclimatic variables. T_s_0 in open land was significantly correlated with solar radiation. Wind speed had significant influences on differences between T_a and T_s_0, between open land T_s_0 and understory T_s_0. The long-term data showed that T_s_0 under forest canopy were closely coupled with T_a in open land. (2) T_a had a larger increase than T_s_0 in open land, and temperature increases in winter were greater than in other seasons. Soil temperature at depths under forest canopy had nearly twice the increases of those on open land; we attributed this to the higher relative increase of W_s over S_t. (3) A slope change in 1998 was detected in the T_s_0 and T_a difference (T_s_0 − T_a) series, suggesting different response of T_s_0 and T_a since that year. Deceleration of S_t and stability of W_s may have been factors.

This study improves our understanding of warming in a nature reserve where anthropogenic influences are absent. Further studies are needed for the biological and biochemical implications on subtropical mountain forest.