The negative effects of competition on tree resilience weakened as drought severity intensified

Abstract

As one of the important factors limiting tree growth in forests, competition structure, such as neighborhood competitive pressure and individual tree competitive ability, plays a significant role in regulating tree responses to drought events, but how it performs in different intensities of droughts remains unclear. Here, we used a network of Larix gmelinii tree-ring data and field data in 41 sites, covering most of the distribution of natural larch across Daxinganling region, to investigate the role of competition in modulating tree resistance and resilience to moderate, severe and extreme droughts in the year 2007. The results showed that growth reduction in trees increased from 46 % under moderate drought to 65 % under extreme drought. The influence of neighborhood competitive pressure and individual competitive ability on tree resistance and resilience weakened as drought severity increases, particularly, the individual competitive ability lost its influence on tree resilience to extreme droughts. Our results highlight that competition have negative effects on tree resistance and resilience only to moderate and severe droughts, but not to extreme droughts. Therefore, the forestry practice of competition-reduction strategies, such as thinning, in aiding trees’ endurance of future droughts should be re-evaluated in consideration of the intensity of droughts.