Continuously Vegetation Greening over Inner Mongolia for the Past Three Decades

Hui Zhang,Yi Shang,Xin Zhang,Giri Kattel,Lijuan Miao

doi:10.3390/rs13132446

Abstract

The warming climate has rapidly altered vegetation growth in drylands, and consequently, has put great pressure on sustainable livelihoods. Various datasets have been applied from local to global scale to study vegetation dynamics and there is a lack of solid comparison among multiple datasets. Note that vegetation growth might shift over time and the greening and browning components over a long-time span might be masked by a linear trend. Here, we aim to monitor the long-term and nonlinear dynamics in vegetation greenness for Inner Mongolia (an important part of dryland Asia). As a useful tool that indicates vegetation greenness, NDVI (Normalized Difference Vegetation Index) and LAI (Leaf Area Index) integrals derived from the GIMMS (Global Inventory Modelling and Mapping Studies) NDVI3g and the GIMMS LAI3g products are applied. During the period of 1982-2016, NDVI/LAI integrals have an overall acceptable consistency in characterizing the trends of vegetation greenness, with NDVI large/small integrals and LAI large/small integrals increase at a rate of 0.96, 1.72, 2.23, and 3.13 per decade, respectively. Inner Mongolia experienced a noticeable greening process (71% and 82% greening area in NDVI large/small integrals, 67% and 73% greening area in LAI large/small integrals), despite the fragmentally distributed browning trends in eastern and partial northern Inner Mongolia. As inferred from nonlinear trend analysis, we found the greening process is still prevalent. The browning of eastern Inner Mongolia under the linear analysis was actually transferring from browning to greening, while the greening trend in northern Inner Mongolia was changing to browning. Increased occurrences in the frequency of breakpoints after 1999 suggest that previously stable vegetation ecology is more sensitive to external disturbances such as altered climatic impact and anthropogenic intervention.

Highlights

We found the averaged NDVI large integral of the vegetated area in Inner Mongolia increased by 3.26 (5.5%) from 1982 to 2016, with a rate of 0.96 per decade (p < 0.01; t-test) (Figure 3a), while the mean NDVI small integral increased by 5.85 (17%) in the same period, with a rate of 1.72 per decade (p < 0.01; t-test) (Figure 3b)
We find the spatial patterns of changes in Leaf Area Index (LAI) integrals are consistent with NDVI over most regions of Inner Mongolia, both for the large integral and small integral (Figure 4)
We combined NDVI and LAI integrals derived from the remotely-sensed datasets to explore the spatiotemporal patterns in vegetation greenness changes over

Summary

Introduction

Vegetation provides valuable ecosystem services to various terrestrial ecosystems, e.g., carbon sequestrations, resources for livestock grazing, and water resources regulations [1,2]. The. Intergovernmental Panel on Climate change Fifth Assessment Report (IPCC AR5) suggested that a 0.85 ◦ C increase in global temperature has already been observed during the period of. The future warming of the climate is predicted to greatly influence the terrestrial ecosystems, including grassland degeneration and desertification [4,5]. A shift toward more variable rainfall leads to a general decrease in the biomass of grass resources and increased dryland vegetation vulnerability to loss [6].

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Methods

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Discussion

Conclusion