[Responses of radial growth of Larix principis-rupprechtii at different densities to drought events].

Abstract

In recent years, a surge in drought occurrences has dramatically impacted tree growth worldwide. We examined the ecological resilience of Larix principis-rupprechtii plantations with varying densities (1950, 2355, and 2595 trees·hm^-2) 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 (R_t), recovery (R_c), and resilience (R_s). The results showed that drought events occurred in 2006-2010, 2015, and 2018. The R_t for L. principis-rupprechtii plantations varied from 0.76 to 2.01 across three drought events, indicating generally high resistance, except for the plantation with 2355 trees·hm^-2 during the second dry year (R_t=0.69). The R_t for the plantation with 2595 trees·hm^-2 significantly decreased across all drought events, while no significant change was observed in the plantations with 1950 and 2355 trees·hm^-2. The R_c 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 L. principis-rupprechtii to the first drought event, whereas the plantation with 2595 trees·hm^-2 exhibited significantly lower R_s during the second and third drought events compared with 1950 and 2355 trees·hm^-2, respectively. During the 2015 drought event, plantation with 2595 trees·hm^-2 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^-2. Overall, the plantation with 2595 trees·hm^-2 demonstrated the lowest resilience to drought events.