title: Relationship of Climatic and Forest Factors to Drought- and Heat-Induced Tree Mortality.
abstract: Tree mortality due to warming and drought is a critical aspect of forest ecosystem in responding to climate change. Spatial patterns of tree mortality induced by drought and its influencing factors, however, have yet to be documented at the global scale. We collected observations from 248 sites globally where trees have died due to drought and then assessed the effects of climatic and forest factors on the rate of tree mortality. The global mean annual mortality rate was 5.5%. The rate of tree mortality was significantly and negatively correlated with mean annual precipitation (P < 0.01). Tree mortality was lowest in tropical rainforests with mean annual precipitation >2000 mm and was severe in regions with mean annual precipitation <1000 mm. Mortality rates varied amongst species. The global annual rate of mortality was much higher for gymnosperms (7.1%) than angiosperms (4.8%) but did not differ significantly between evergreen (6.2%) and deciduous (6.1%) species. Stand age and wood density affected the mortality rate. Saplings (4.6%) had a higher mortality rate than mature trees (3.2%), and mortality rates significantly decreased with increasing wood density for all species (P < 0.01). We therefore concluded that the tree mortality around the globe varied with climatic and forest factors. The differences between tree species, wood density, stand density, and stand age should be considered when evaluating tree mortality at a large spatial scale during future climatic extremes.
authors.affiliation: College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province, China.
authors.forename: Qingyin
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province, China.|Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.|State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi Province, China.|College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Ming'an
authors.initials: M
authors.lastname: Shao
authors.affiliation: Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.|College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Xiaoxu
authors.initials: X
authors.lastname: Jia
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi Province, China.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Wei
mesh_terms: D057231:Climate Change; D055864:Droughts; D017753:Ecosystem; D065928:Forests; D006358:Hot Temperature; D008954:Models, Biological; D011156:Population Density; D014197:Trees / Q000254:growth & development*