Vegetation Changes along the Qinghai-Tibet Plateau Engineering Corridor Since 2000 Induced by Climate Change and Human Activities

Yi Song,Long Jin,Haibo Wang

doi:10.3390/rs10010095

Abstract

The Qinghai-Tibet (QT) Plateau Engineering Corridor is located in the hinterland of the QT Plateau, which is highly sensitive to global climate change. Climate change causes permafrost degradation, which subsequently affects vegetation growth. This study focused on the vegetation dynamics and their relationships with climate change and human activities in the region surrounding the QT Plateau Engineering Corridor. The vegetation changes were inferred by applying trend analysis, the Mann-Kendall trend test and abrupt change analysis. Six key regions, each containing 40 nested quadrats that ranged in size from 500 × 500 m to 20 × 20 km, were selected to determine the spatial scales of the impacts from different factors. Cumulative growing season integrated enhanced vegetation index (CGSIEVI) values were calculated for each of the nested quadrats of different sizes to indicate the overall vegetation state over the entire year at different spatial scales. The impacts from human activities, a sudden increase in precipitation and permafrost degradation were quantified at different spatial scales using the CGSIEVI values and meteorological data based on the double mass curve method. Three conclusions were derived. First, the vegetation displayed a significant increasing trend over 23.6% of the study area. The areas displaying increases were mainly distributed in the Hoh Xil. Of the area where the vegetation displayed a significant decreasing trend, 72.4% was made up of alpine meadows. Second, more vegetation, especially the alpine meadows, has begun to degenerate or experience more rapid degradation since 2007 due to permafrost degradation and overgrazing. Finally, an active layer depth of 3 m to 3.2 m represents a limiting depth for alpine meadows.

Highlights

Vegetation makes up the main part of terrestrial ecosystems [1] and is an important element of energy exchanges, the water cycle and biogeochemical cycles at the Earth’s surface
Vegetation change has been and will be a key issue in global changes involving terrestrial ecosystems as it is sensitive to climate change [3,4]
Between 2002 and 2012, the spring onset of soil thawing at a depth of 50 cm advanced by approximately 20 days within alpine meadows and 18 days within alpine steppes [12]

Summary

Introduction

Vegetation makes up the main part of terrestrial ecosystems [1] and is an important element of energy exchanges, the water cycle and biogeochemical cycles at the Earth’s surface. Vegetation change has been and will be a key issue in global changes involving terrestrial ecosystems as it is sensitive to climate change [3,4]. The Qinghai-Tibet (QT) Plateau is one of the most sensitive areas in terms of its response to global climate change because of its unique topography [5] and the widespread occurrence of permafrost [6,7] and is recognized as a hotspot for coupled studies. From 1987 to 2008, there was a pattern of earlier thawing and later freezing due to climate warming, especially in seasonally frozen ground and permafrost regions with high ground temperatures [14]

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Results

Discussion

Conclusion