Vegetation dynamic analysis based on multisource remote sensing data in the east margin of the Qinghai-Tibet Plateau, China.

Haijun Wang,Guihua Yi,Tingbin Zhang,Peihao Peng,Xiangdong Kong

doi:10.7717/peerj.8223

Haijun Wang, Guihua Yi + Show 3 more

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https://doi.org/10.7717/peerj.8223

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Abstract

This study focuses on the vegetation dynamic caused by global environmental change in the eastern margin of the Qinghai-Tibet Plateau (EMQTP). The Qinghai–Tibet Plateau (QTP) is one of the most sensitive areas responding to global environmental change, particularly global climate change, and has been recognized as a hotspot for coupled studies on changes in global terrestrial ecosystems and global climates. An important component of terrestrial ecosystems, vegetation dynamic has become a key issue in global environmental change, and numerous case studies have been conducted on vegetation dynamic trends using multi-source data and multi-scale methods across different study periods. The EMQTP is regarded as a transitional area located between the QTP and the Sichuan basin, and has special geographical and climatic conditions. Although this area is ecologically fragile and sensitive to climate change, few studies about vegetation dynamics have been carried out in this area. Thus, in this study, we used long-term series datasets of GIMMS 3g NDVI and VGT/PROBA-V NDVI to analyze the vegetation dynamics and phenological changes from 1982 to 2018. Validation was performed based on Landsat NDVI and Vegetation Index & Phenology (VIP) data. The results reveal that the year 1998 was a vital turning point in the start of growing season (SGS) in vegetation ecosystems. Before this turning point, the SGS had an average slope of 9.2 days/decade, and after, the average slope was 3.9 days/decade. The length of growing season (LGS) was slightly prolonged between 1982 to 2015. Additionally, the largest national alpine wetland grassland experienced significant vegetation degradation; in autumn, the degraded area accounted for 63.4%. Vegetation degradation had also appeared in the arid valleys of the Yalong River and the Jinsha River. Through validation analysis, we found that the main causes of vegetation degradation are the natural degradation of wetland grassland and human activities, specifically agricultural development and residential area expansion.

Highlights

Vegetation is the main component of terrestrial ecosystems on earth (Piao & Fang, 2003), playing a crucial role in energy exchange, water cycles and biological cycles on the terrestrial surface
The dynamic threshold method was used to detect the phenological changes of three ecosystems from 1982 to 2015
It was calculated that the length of growing season (LGS) decreased by 0.51 days/decade based on the start of growing season (SGS) and end of the growing season (EGS) during the study period

Summary

Introduction

Vegetation is the main component of terrestrial ecosystems on earth (Piao & Fang, 2003), playing a crucial role in energy exchange, water cycles and biological cycles on the terrestrial surface. The normalized difference vegetation index (NDVI) is widely used as a parameter of vegetation dynamics and refers to the quantitative values of vegetation conditions. It is often obtained through a combination of different spectral remote sensing data. Global Inventory Monitoring and Modeling Studies (GIMMS) 3g NDVI and SPOT VGEATION (VGT) NDVI have been acknowledged as the most widely used remote sensing data products (Casa et al, 2018; Chavez et al, 2019), being used to monitor vegetation dynamics at both regional and global scales (Liu et al, 2017a; Liu et al, 2017b; Wu et al, 2017). GIMMS NDVI data cover a large time span from 1982 to 2015, and VGT NDVI has higher spatial and temporal resolutions

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