Tree rings reveal a major episode of forest mortality in the late 18th century on the Tibetan Plateau

• Published in: Global and planetary change 2018-04, Vol.163, p.44-50
• Main Authors: Fang, Ouya, Alfaro, René I., Zhang, Qi-Bin
• Format: Article
• Language: English
• Subjects: Dendroecology; Drought; Dust storm; Growth decline; Growth release; Tree rings
• ISSN: 0921-8181; 1872-6364
• DOI: 10.1016/j.gloplacha.2018.02.004

There is a growing research interest on studying forest mortality in relation to ongoing climate warming, but little is known about such events in past history. The study of past forest mortality provides valuable information for determining baselines that establish the normal parameters of functioning in forest ecosystems. Here we report a major episode of previously undocumented forest mortality in the late 18th century on the northern Tibetan Plateau, China. The event was not spatially uniform, in which a more severe mortality happened in dryer sites. We used dendrochronology to compare radial growth trajectories of individual trees from 11 sites in the region, and found that many trees showed positive growth trend, or growth release, during 1796–1800 CE. Growth releases are a proxy indicator of stand thinning caused by tree mortality. The growth release was preceded by an almost two-decade long growth reduction. Long-term drought related to weakened North Atlantic Oscillation and frequent El Niño events are the likely factors causing the tree mortality in a large area of the plateau. Our findings suggest that, besides the effect of drought in the late 18th century, large-scale forest mortality may be an additional factor that further deteriorated the environment and increased the intensity of dust storms. •A major episode of forest mortality was identified to occur in the 1796–1800 CE on the northern Tibetan Plateau.•The forest mortality was preceded by a two-decade growth reduction relating to climatic drought.•The forest mortality contributed to the increased intensity of dust storm in the region.•The approach we developed to identify forest mortality is applicable to other studies.