Observational Quantification of Climatic and Human Influences on Vegetation Greening in China

Wenjian Hua,Haishan Chen,Shanlei Sun,Xing Li,Minhua Qin,Liming Zhou,Hedi Ma,Qinghan Huang,Zhenghui Xie

doi:10.3390/rs9050425

Abstract

This study attempts to quantify the relative contributions of vegetation greening in China due to climatic and human influences from multiple observational datasets. Satellite measured vegetation greenness, Normalized Difference Vegetation Index (NDVI), and relevant climate, land cover, and socioeconomic data since 1982 are analyzed using a multiple linear regression (MLR) method. A statistically significant positive trend of average growing-season (April–October) NDVI is found over more than 34% of the vegetated areas, mainly in North China, while significant decreases in NDVI are only seen in less than 5% of the areas. The relationships between vegetation and climate (temperature, precipitation, and radiation) vary by geographical location and vegetation type. We estimate the NDVI changes in association with the non-climatic effects by removing the climatic effects from the original NDVI time series using the MLR analysis. Our results indicate that land use change is the dominant factor driving the long-term changes in vegetation greenness. The significant greening in North China is due to the increase in crops, grasslands, and forests. The socioeconomic datasets provide consistent and supportive results for the non-climatic effects at the provincial level that afforestation and reduced fire events generally have a major contribution. This study provides a basis for quantifying the non-climatic effects due to possible human influences on the vegetation greening in China.

Highlights

The past few decades have been characterized by a widespread increase in the greenness of northern forests [1,2,3]
The Normalized Difference Vegetation Index (NDVI) increases from southeast to northwest and ranges from 0.4 to 0.6 over northern China, 0.7 in Fujian, Zhejiang, south of Shanxi, and west of Hubei Province
We further examine the spatiotemporal patterns of NDVI changes over China by conducting an Figure 4 the shows

Summary

Introduction

The past few decades have been characterized by a widespread increase in the greenness of northern forests [1,2,3]. An increase in vegetation greenness generally implies higher absorption of photosynthetically active radiation, and greater fractions of leaves and biomass [4]. These changes in land surface, especially over the Northern mid- and high-latitudes, may alter land surface properties such as albedo and aerodynamic roughness, influence the surface energy budget via partitioning between sensible and latent heat fluxes, and have important climatic implications [5,6,7,8,9]. Nemani et al [10] estimated that water mainly limits vegetation growth on over 40% of the Earth’s vegetated surface, whereas temperature and radiation limit 33% and 27% of that growth, respectively

Methods

Results

Conclusion