Vegetation Browning Trends in Spring and Autumn over Xinjiang, China, during the Warming Hiatus

Moyan Li,Junqiang Yao,Jianghua Zheng,Jingyun Guan

doi:10.3390/rs14051298

Abstract

Satellite-derived vegetation records (GIMMS3g-NDVI) report that climate warming promotes vegetation greening trends; however, the climate impacts on vegetation growth during the global warming hiatus period (1998–2012) remain unclear. In this study, we focused on the vegetation change trend in Xinjiang in spring and autumn before and during the recent warming hiatus period, and their climate-driving mechanisms, which have not been examined in previous studies. Based on satellite records, our results indicated that the summer normalized difference vegetation index (NDVI) in Xinjiang experienced a greening trend, while a browning trend existed in spring and autumn during this period. The autumn NDVI browning trend in Xinjiang was larger than that in spring; however, the spring NDVI displayed a higher correlation with climatic factors than did the autumn NDVI. During the warming hiatus, spring climatic factors were the main controlling factors of spring NDVI, and spring vapor pressure deficit (VPD) had the highest positive correlation with spring NDVI, followed by spring temperature. The larger increase in air temperature in spring than in autumn resulted in increased VPD differences in spring and autumn. In autumn, summer climatic factors (e.g., VPD, WS, RH, and precipitation) were significantly correlated with the autumn NDVI during the warming hiatus. However, the autumn temperature was weakly correlated with the autumn NDVI. Our results have significant implications for understanding the response of vegetation growth to recent and future climatic conditions.

Highlights

The global air temperature dataset indicates that the warming rate did not increase significantly during the period of 1998–2012 [1–8], and this period has become known as the “warming hiatus” or “global slowdown” [2,9]
Our analysis showed that the summer normalized difference vegetation index (NDVI) significantly increased; there was an insignificant reduction in the spring and autumn NDVI during the warming hiatus period
This study focused on the latest changes in spring and autumn vegetation growth in Xinjiang and their climate-driving mechanisms, using satellite-derived vegetation records (GIMMS3g-NDVI) as indicators

Summary

Introduction

The global air temperature dataset indicates that the warming rate did not increase significantly during the period of 1998–2012 [1–8], and this period has become known as the “warming hiatus” or “global slowdown” [2,9]. Many previous reports have indicated that the “warming hiatus” phenomenon has been reported in China and the Xinjiang region [10–12]. A warming hiatus has profound effects on ecosystems, water resources, and sustainable development. Many studies have found that air temperature is a major controlling factor for vegetation growth changes [13–16]. Vegetation growth is consistent with changes in temperature [17]. Kaufmann et al [18] reported that global warming was the main contributor to vegetation greening in the Northern Hemisphere using the normalized difference vegetation index (NDVI). Other studies have indicated that global warming has advanced spring vegetation green-up and delayed autumn vegetation senescence [19,20]

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