Abstract: Four ringwidth chronologies of Pinus koraiensis and Abies nephrolepis in and out of forest gaps in a broadleaved Korean pine forest in Xiaoxing’an Mountain, Northeast China were developed to explore the influence of gap disturbance (microenvironmental difference) and global warming after 1980 on tree radial growth. Results showed that the annual mean ring width of P. koraiensis out of forest gaps slightly decreased after warming, while it increased in forest gaps. The relationship between the radial growth of P. koraiensis out of forest gaps and temperature became weakened, but it became strengthened for the trees in forest gaps. The coefficients of correlation between Palmer drought severity index (PDSI) and P. koraiensis chronologies in and out of forest gaps both changed from negative to positive after warming. However, the radial growth of A. nephrolepis decreased due to forest gap disturbance. Annual mean ring width of A. nephrolepis in and out of forest gaps both decreased about 50% since climate warming after 1980. Temperature was more negatively correlated with the radial growth of A. nephrolepis out of forest gaps than with that in forest gaps. The negative effect of temperature from May to October on radial growth of A. nephrolepis out of forest gaps was obvious after 1980. The negative effect of precipitation from January to May on A. nephrolepis out of forest gaps increased, while such effect changed from negative to positive for A. nephrolepis in forest gaps. The correlation coefficients between PDSI and A. nephrolepis chronologies out of forest gaps changed from negative before warming to positive after warming, but negative correlations became more significant for A. nephrolepis in forest gaps. Our results indicate that forest gap disturbance decreases the radial growth of shaded tree species, while it has little effect on sunny tree species or slightly increases the radial growth. Tree radial growth in forest gaps is more vulnerable to be affect by external environmental change than that out of forest gaps. Gap disturbance improves the adaptability of the wet and shadetolerant species to warming by making it adapt to the warm and arid environment (forest gap environment) in advance. In addition, warming causes larger difference of growthclimate relationship between trees growing in and out of forest gaps.

Key words: Tibet Plateau, climate change., seasonal response, structural equation model (SEM), PDO, vegetation growth