Effect of climate and thaw depth on alpine vegetation variations at different permafrost degrading stages in the Tibetan Plateau, China

Yuqing Feng,Sihai Liang,Xingxing Kuang,Guangjun Wang,Xu-Sheng Wang,Pan Wu,Li Wan,Qingbai Wu

doi:10.1080/15230430.2019.1605798

Abstract

ABSTRACTUnderstanding the driving forces for alpine vegetation variations at different permafrost degrading stages is important when the Tibetan Plateau is experiencing climate warming. We applied the modified Frost Number model to simulate frozen ground distributions in the Tibetan Plateau and calculated the maximum thawing depth by the Stefan approach. We classified the simulated frozen ground into three subzones: seasonal frozen ground zone, changing zone, and permafrost zone. We evaluated the effects of precipitation, air temperature, and maximum thawing depth on Normalized Difference Vegetation Index (NDVI) in the subzones across five different stages from 1982 to 2012. The results show that permafrost zone, changing zone, and seasonal frozen ground zone account for about 30.6 percent, 23.3 percent, and 46.1 percent of the study area, respectively. Over the five stages, permafrost areas decreased at fast, slow, fastest, and then slowest rate from stage1 to stage 5, and the large continuous permafrost area has been degraded into pieces. Precipitation is strongly correlated with NDVI and contributes most `to the changes of NDVI. Maximum thawing depth and particularly air temperature show a much smaller correlation and contribute less to the variation rate of NDVI. The findings will have broad applications in investigating the impact of climate and environment changes on alpine vegetation variations in the Tibetan Plateau.

Highlights

Permafrost, the frozen ground at low temperature below 0 °C for ≥2 years (Muller 1947), is highly sensitive to climate change and surface disturbances, especially to air temperature changes (Li et al 2008; Yang et al 2010)
Permafrost in the Tibetan Plateau is more sensitive to air temperature changes and it is considered the key indicator for climate and environment changes
We quantitatively analyzed the relations between precipitation, temperature, the maximum thawing depth, and Normalized Difference Vegetation Index (NDVI) in the subzones

Summary

Introduction

Permafrost, the frozen ground at low temperature below 0 °C for ≥2 years (Muller 1947), is highly sensitive to climate change and surface disturbances, especially to air temperature changes (Li et al 2008; Yang et al 2010). Permafrost in the Tibetan Plateau is more sensitive to air temperature changes and it is considered the key indicator for climate and environment changes (Wang et al.2016). A significant climate warming occurred on the Tibetan Plateau and the increase in temperature came earlier and faster than in other parts of China (Pan and Li 1996; Liu and Chen 2000; Wang et al 2000; Cheng and Wu 2007; Wu and Zhang 2010; Kuang and Jiao 2016; Lu, Zhao, and Wu 2017). The permafrost degradation is mainly characterized by a reduction in areal extent of permafrost occurrence and active layer deepening (Jin et al 2009; Xue et al 2009; Wu and Zhang 2010)

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