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Open AccessArticle

Drying and Wetting Trends and Vegetation Covariations in the Drylands of China

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School of Geographical Sciences, Nanjing University of Information Science and Technology, Nanjing 210044, China
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Department of Earth Sciences, Free University Amsterdam, 1081 HV Amsterdam, The Netherlands
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School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China
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Office of the University President, Nanjing University of Information Science and Technology, Nanjing 210044, China
*
Authors to whom correspondence should be addressed.
Water 2020, 12(4), 933; https://doi.org/10.3390/w12040933
Received: 14 January 2020 / Revised: 18 March 2020 / Accepted: 19 March 2020 / Published: 25 March 2020
(This article belongs to the Section Hydrology)
The semi-arid and arid drylands of China, which are located in the inland region of Eurasia, have experienced rapid climate change. Some regions in particular, have shown upward trends in the observational records of precipitation. However, there is more to drying and wetting than just changes in precipitation which still have large uncertainties. Coherent results, however, can be obtained, at the regional scale, with the use of multiple indices as shown in the recent literature. We divided the drylands of China into three sub-regions, i.e., a semi-arid (SA), an eastern-arid (EA) and a western-arid (WA) region. Precipitation from the China Meteorological Administration (CMA) and Climatic Research Unit (CRU), statistical and physical drought indices, including the Standardized Precipitation Evapotranspiration Index (SPEI), the Palmer Drought Severity Index (PDSI), self-calibrating PDSI (sc_PDSI), Root zone soil moisture (Root_sm) and Surface soil moisture (Surf_sm) from Global Land Evaporation Amsterdam Model (GLEAM), and Normalized Difference Vegetation Index (NDVI) were used to identify temporal and spatial patterns in drying and wetting. Data were selected from 1982–2012, in line with the availability of the remotely sensed vegetation data. Results show that the drylands of China exhibits a pattern of wetting in the west and drying in the east. The semi-arid region in the east is becoming drier and the drought area is increasing, with the values of CMA_P, CRU_P, PDSI, sc_PDSI, SPEI-01,SPEI-06, SPEI-12, Root_sm, Surf_sm at −1.064 mm yr−1, −0.834 mm yr−1, −0.050 yr−1 (p < 0.1), −0.174 yr−1 (p < 0.1), −0.014 yr−1, −0.06, −0.021 (p < 0.1), −0.257×10−3 m3 m−3 yr−1, −0.024×10−3 m3 m−3 yr−1, respectively. The arid region generally exhibits a wetting trend, while the area in drought declines only in the western arid region, but not in the eastern arid part. In the semi-arid region, growing season (May to September) NDVI is significantly correlated (p < 0.1) with eight out of nine indicators. We show in this study that the semi-arid region needs more study to protect the vegetation ecosystem and the water resources. View Full-Text
Keywords: dryland; drought index; drying and wetting trend; vegetation dryland; drought index; drying and wetting trend; vegetation
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MDPI and ACS Style

Liang, C.; Chen, T.; Dolman, H.; Shi, T.; Wei, X.; Xu, J.; Hagan, D.F.T. Drying and Wetting Trends and Vegetation Covariations in the Drylands of China. Water 2020, 12, 933.

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