Changing Trends of NDVI and Their Responses to Climatic Variation in Different Types of Grassland in Inner Mongolia from 1982 to 2011

Jie Yang,Qingzhu Gao,Zhiqiang Wan,Suld Borjigin,Yulong Yan,Yali Chen,Rui Gu,Dong Zhang

doi:10.3390/su11123256

Abstract

Normalized difference vegetation index (NDVI) is commonly used to indicate vegetation density and condition. NDVI was mostly correlated with climate factors. We analyzed changing trends of NDVI in different types of grassland in Inner Mongolia and the response of NDVI to climatic variation from 1982 to 2011. NDVI of meadow steppe increased significantly in spring while it decreased in other seasons. The annual mean NDVI in typical steppe and desert steppe increased significantly in the last 30a. However, in the greatest area of steppe desert, the NDVI had no significant change in summer, autumn, and the growing season. In meadow steppe, typical steppe, and desert steppe, the area showed a positive correlation of NDVI to temperature as highest in spring compared to other seasons, because warming in spring is beneficial to the plant growth. However, in the greatest area of steppe desert, the correlation of NDVI to temperature was not significant. The NDVI was positively correlated to precipitation in four types of grassland. In the steppe desert, the precipitation had no significant effect on the NDVI due to the poor vegetation cover in this region. The NDVI was not significantly correlated to the precipitation in autumn because of vegetation withering in the season and not need precipitation. Precipitation was a more important factor rather than temperature to NDVI in the region. The response of NDVI to temperature and precipitation in different seasons should be studied in more detail and the effect of other factors on NDVI should be considered in future research.

Highlights

Normalized difference vegetation index (NDVI) is commonly used for measuring vegetation density and condition from remotely sensed data that show the difference in reflected radiation between visible and near-infrared wavelengths [1], with lower differences indicating sparser vegetation
The ratio that NDVI increased significantly in typical steppe was higher than decreased in five seasons
NDVI increased in spring and decreased in summer in the steppe desert, but did not change significantly in autumn, growing season, and year-round scale in most areas

Summary

Introduction

NDVI (normalized difference vegetation index) is commonly used for measuring vegetation density and condition from remotely sensed data that show the difference in reflected radiation between visible and near-infrared wavelengths [1], with lower differences indicating sparser vegetation. The impacts of climate change on grassland vegetation change vary spatially. Climate change has led to grassland degradation in some regions while promoting grassland restoration [9]. Warmer and drier climates cause the productivity of North America grassland to decline [10]. Grassland ecosystems in Australia are extremely sensitive to climate change, and global warming has caused a decline in productivity in most grasslands [11]. Climate change has exacerbated grassland degradation in China [12]. Studies have shown that climate change contributes more to grassland degradation than “overgrazing” in Inner Mongolia [13]. Climate change is one of the main driving factors to grassland desertification in southern and eastern Xinjiang [14]

Methods

Findings

Discussion

Conclusion