[Responses of radial growth of at different densities to drought events].

In recent years, a surge in drought occurrences has dramatically impacted tree growth worldwide. We examined the ecological resilience of plantations with varying densities (1950, 2355, and 2595 trees·hm) at the Saihanba Mechanical Forest Farm, by extracting the increment cores using the standard dendrochronological method to measure individual-tree basal area increments (BAI) as part of our assessment of ecological resilience, including resistance (), recovery (), and resilience (). The results showed that drought events occurred in 2006-2010, 2015, and 2018. The for plantations varied from 0.76 to 2.01 across three drought events, indicating generally high resistance, except for the plantation with 2355 trees·hm during the second dry year (=0.69). The for the plantation with 2595 trees·hm significantly decreased across all drought events, while no significant change was observed in the plantations with 1950 and 2355 trees·hm. The showed no differences in response to a single drought event across plantation densities, with a significant upward trend for all the densities with each occurrence of drought event. There was no significant difference in the resilience of different densities of to the first drought event, whereas the plantation with 2595 trees·hm exhibited significantly lower during the second and third drought events compared with 1950 and 2355 trees·hm, respectively. During the 2015 drought event, plantation with 2595 trees·hm experienced a significant growth decline (radial growth change rate was -26.5%), while no such decline was observed in the plantations with 1950 and 2355 trees·hm. Overall, the plantation with 2595 trees·hm demonstrated the lowest resilience to drought events.