title: Assessments of Drought Impacts on Vegetation in China with the Optimal Time Scales of the Climatic Drought Index.
abstract: Drought is expected to increase in frequency and severity due to global warming, and its impacts on vegetation are typically extensively evaluated with climatic drought indices, such as multi-scalar Standardized Precipitation Evapotranspiration Index (SPEI). We analyzed the covariation between the SPEIs of various time scales and the anomalies of the normalized difference vegetation index (NDVI), from which the vegetation type-related optimal time scales were retrieved. The results indicated that the optimal time scales of needle-leaved forest, broadleaf forest and shrubland were between 10 and 12 months, which were considerably longer than the grassland, meadow and cultivated vegetation ones (2 to 4 months). When the optimal vegetation type-related time scales were used, the SPEI could better reflect the vegetation's responses to water conditions, with the correlation coefficients between SPEIs and NDVI anomalies increased by 5.88% to 28.4%. We investigated the spatio-temporal characteristics of drought and quantified the different responses of vegetation growth to drought during the growing season (April-October). The results revealed that the frequency of drought has increased in the 21st century with the drying trend occurring in most of China. These results are useful for ecological assessments and adapting management steps to mitigate the impact of drought on vegetation. They are helpful to employ water resources more efficiently and reduce potential damage to human health caused by water shortages.
authors.affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China. zhengli@mail.bnu.edu.cn.|Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, China. zhengli@mail.bnu.edu.cn.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China. tzhou@bnu.edu.cn.|Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, China. tzhou@bnu.edu.cn.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhou
authors.affiliation: School of Geography, Beijing Normal University, Beijing 100875, China. zhaoxiang@bnu.edu.cn.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China. huangkaicheng@mail.bnu.edu.cn.|Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, China. huangkaicheng@mail.bnu.edu.cn.
authors.forename: Kaicheng
authors.initials: K
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China. gsapril@163.com.|Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, China. gsapril@163.com.
authors.forename: Shan
authors.initials: S
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China. wuhaogis@163.com.|Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, China. wuhaogis@163.com.
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China. luohui3377@163.com.|Academy of Disaster Reduction and Emergency Management, Ministry of Civil Affairs & Ministry of Education, Beijing 100875, China. luohui3377@163.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Luo
mesh_terms: D002681:China; D055864:Droughts; D004463:Ecology; D065928:Forests; D012621:Seasons
keywords: China; NDVI; SPEI; drought; ecological assessment; optimal time scales