Drought-induced tree mortality has recently received considerable attention. Questions have arisen over the necessary intensity and duration thresholds of droughts that are sufficient to trigger rapid forest declines. The values of such tipping points leading to forest declines due to drought are presently unknown. In this study, we have evaluated the potential relationship between the level of tree growth and concurrent drought conditions with data of the tree growth-related ring width index (RWI) of the two dominant conifer species (Pinus edulis and Pinus ponderosa) in the Southwestern United States (SWUS) and the meteorological drought-related standardized precipitation evapotranspiration index (SPEI). In this effort, we determined the binned averages of RWI and the 11 month SPEI within the month of July within each bin of 30 of RWI in the range of 0–3000. We found a significant correlation between the binned averages of RWI and SPEI at the regional-scale under dryer conditions. The tipping point of forest declines to drought is predicted by the regression model as SPEItp = −1.64 and RWItp = 0, that is, persistence of the water deficit (11 month) with intensity of −1.64 leading to negligible growth for the conifer species. When climate conditions are wetter, the correlation between the binned averages of RWI and SPEI is weaker which we believe is most likely due to soil water and atmospheric moisture levels no longer being the dominant factor limiting tree growth. We also illustrate a potential application of the derived tipping point (SPEItp = −1.64) through an examination of the 2002 extreme drought event in the SWUS conifer forest regions. Distinguished differences in remote-sensing based NDVI anomalies were found between the two regions partitioned by the derived tipping point.
State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, People’s Republic of China;Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, People’s Republic of China;School of Earth and Environmental Sciences, Queens College, City University of New York, New York, NY 11367, USA;Department of Meteorology, Bert Bolin Centre for Climate Research, Stockholm University, Stockholm S-106 91, Sweden;School of Geography, Beijing Normal University, Beijing 100875, People’s Republic of China;College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, People’s Republic of China;State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, People’s Republic of China;Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, People’s Republic of China;School of Geography, Beijing Normal University, Beijing 100875, People’s Republic of China;College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, People’s Republic of China;School of Earth and Environmental Sciences, Queens College, City University of New York, New York, NY 11367, USA;School of Earth and Environmental Sciences, Queens College, City University of New York, New York, NY 11367, USA;State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, People’s Republic of China;Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, People’s Republic of China;State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, People’s Republic of China;Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, People’s Republic of China;State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, People’s Republic of China;Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, People’s Republic of China
Recommended Citation:
Kaicheng Huang,Chuixiang Yi,Donghai Wu,et al. Tipping point of a conifer forest ecosystem under severe drought[J]. Environmental Research Letters,2015-01-01,10(2)