Vegetation Dynamic Assessment by NDVI and Field Observations for Sustainability of China's Wulagai River Basin.

Panpan Chen,Dongwei Liu,Dehua Mao,Huamin Liu,Zongming Wang,Lixin Wang,Zhiyong Li,Yi Zhuo,Jinghui Zhang,Cunzhu Liang,Lu Wen

doi:10.3390/ijerph18052528

Abstract

Accurate monitoring of grassland vegetation dynamics is essential for ecosystem restoration and the implementation of integrated management policies. A lack of information on vegetation changes in the Wulagai River Basin restricts regional development. Therefore, in this study, we integrated remote sensing, meteorological, and field plant community survey data in order to characterize vegetation and ecosystem changes from 1997 to 2018. The residual trend (RESTREND) method was utilized to detect vegetation changes caused by human factors, as well as to evaluate the impact of the management of pastures. Our results reveal that the normalized difference vegetation index (NDVI) of each examined ecosystem type showed an increasing trend, in which anthropogenic impact was the primary driving force of vegetation change. Our field survey confirmed that the meadow steppe ecosystem increased in species diversity and aboveground biomass; however, the typical steppe and riparian wet meadow ecosystems experienced species diversity and biomass degradation, therefore suggesting that an increase in NDVI may not directly reflect ecosystem improvement. Selecting an optimal indicator or indicator system is necessary in order to formulate reasonable grassland management policies for increasing the sustainability of grassland ecosystems.

Highlights

Our study revealed that normalized difference vegetation index (NDVI) values in the Wulagai River Basin showed an overall gentle upward trend
The residual analysis indicated that human factors were the main driving forces of the vegetation dynamics, and that the implementation of the new pasture management policy should help to curb the increase in stocking rates and increase the vegetation area
The typical steppe and riparian wet meadow ecosystems experienced declines in productivity and the replacement of dominant species, such that the ecosystems can be considered relatively fragile. Annual vegetation in these communities has replaced the original dominant species, which has led to an increase in the NDVI, masking the degradation trend of the grassland

Summary

Introduction

Agriculture and animal husbandry originate from grasslands; human production and life are inseparable from grasslands [1]. Grassland dynamics play important roles in the ecological balance and in human economic development, and provide important ecosystem services [2,3]. Grassland vegetation features both seasonal and interannual change characteristics. Monitoring changes in vegetation using long-term remote sensing data can help to better understand and simulate the dynamic changes in terrestrial ecosystems and further reveal global vegetation dynamic trends and rules [4,5]. The normalized difference vegetation index (NDVI), obtained from the Global Inventory Modeling and Mapping Studies (GIMMS) Advanced Very-High Resolution Radiometer (AVHRR) or from

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Methods

Results

Discussion

Conclusion