Triggers of widespread dieback and mortality of poplar (Populus spp.) plantations across northern China

Abstract

Drought-induced mortality has been reported in many forest biomes around the world. In recent years, large-scale forest mortality has been observed across northern China, with forests exhibiting widespread crown dieback symptoms. Previous reports have attributed dieback and mortality to drought stress. In this study, a field survey was undertaken along two transects in northern China. Our aims were to clarify the underlying mechanisms of the widespread dieback and mortality of poplar (Populus spp.) plantations under various environmental stresses. Under these conditions, we observed narrower tree-ring width, and decreased soil water content, indicating that forest growth increased drought stress, and drought stress played a prominent role in triggering dieback and mortality. Bacterial canker disease and low soil nutrient were also linked to dieback and mortality. We observed xylem damage, showing that latent bacterial canker disease was present in many poplar tree stands across northern China, which may increase their susceptibility to drought stress. The results showed that widespread dieback and mortality of poplar forests were related to the interaction of drought stress, bacterial canker and low soil nutrient. The results contributed to understanding the causes for poplar plantation deaths, and could help in the prevention of large-scale death of poplar plantations.