[Differences of drought tolerance of the main tree species in Dongling Mountain, Beijing, China as indicated by tree rings].

Forests in Beijing exhibit vulnerability to increasing stress of extreme drought in recent years. To investigate the drought tolerance of different tree species, we chose three tree species (, , and ) from the forest of Dongling Mountain in Beijing and used dendroecological method to analyze the relationship between radial growth and climate, as well as their resistance and resilience to extreme drought events. Our results showed that the radial growth of and was significantly negatively correlated with monthly mean temperature from May to June, but that of was significantly negatively correlated with monthly mean temperature only in May. The radial growth of was significantly positively correlated with monthly mean precipitation in June, monthly mean relative humidity from May to June and August to September. The radial growth of was significantly positively correlated with monthly mean precipitation and monthly mean relative humidity from June to August. The radial growth of was significantly positively correlated with monthly mean precipitation in February and May, and monthly mean relative humidity in May. The radial growth of all the three species was significantly positively correlated with monthly mean SPEI (standardized precipitation evapotranspiration index) from May to July. was least drought tolerant, as indicated by the greatest growth reduction (46.6%-69.6%), lowest resistance (0.534, 0.304, 0.530) and resilience (0.686, 0.570, 0.753) during the three extreme drought events occurred in the 1994, 2001-2002, and 2007. In contrast, tree growth of showed the highest drought resistance in 2007, whereas no significant differences were observed between other two species. Extreme drought events caused by continuous high temperature and reduced precipitation during the growing season accounted for the reduction in tree radial growth. The various physiological and ecological strategies of tree species were the possible reasons for the difference in drought tolerance. Our results could provide a basis for the selection of suitable afforestation tree species and the formulation of forest protection mea-sures to maintain forest ecosystem functions and services under the background of undergoing climate change.