Analysis of Drought Characteristics in Xilingol Grassland of Northern China Based on SPEI and Its Impact on Vegetation

Siqin Tong,Yuhai Bao,Si Ha,Rigele Te,Qiyun Ma,A Lusi

doi:10.1155/2017/5209173

Abstract

This research is based on the standardized precipitation evapotranspiration index (SPEI) and normalized difference vegetation index (NDVI) which represent the drought and vegetation condition on land. Take the linear regression method and Pearson correlation analysis to study the spatial and temporal evolution of SPEI and NDVI and the drought effect on vegetation. The results show that (1) during 1961–2015, SPEI values at different time scales showed a downward trend; SPEI-12 has a mutation in 1997 and the SPEI value significantly decreased after this year. (2) During 2000–2015, the annual growing season SPEI has an obvious upward trend in time and the apparent wetting spatially. (3) In the recent 16 years, the growing season NDVI showed an upward trend and more than 80% of the total area’s vegetation increased in Xilingol. (4) Vegetation coverage in Xilingol grew better in humid years and opposite in arid years. SPEI and NDVI had a significant positive correlation; 98% of the region showed positive correlation, indicating that meteorological drought affects vegetation growth more in arid and semiarid region. (5) The effect of drought on vegetation has lag effect, and the responses of different grassland types to different scales of drought were different.

Highlights

Grassland is one of the widely distributed ecosystems on the earth; it plays an important role in global carbon cycle and climate system [1] and has vital function on animal husbandry production and socioeconomic development [2]
Whether it is warming or cooling, and greenhouse gas concentration change will lead to changes on spatial-temporal distribution pattern of climate factors, such as sunlight, temperature, and precipitation, which are the indispensable factor in the process of vegetation growth [3]; these changes will be exacerbated the formation of disastrous elements [4] and will have a profound impact on changes of vegetation growth, productivity, and accompanying socioeconomic progress [5, 6]
The drought phenomenon is very complex, it can still be characterized by drought index, such as the Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI), Surface Water Supply Index (SWSI), and Effective Drought Index (EDI) [11]

Summary

Introduction

Grassland is one of the widely distributed ecosystems on the earth; it plays an important role in global carbon cycle and climate system [1] and has vital function on animal husbandry production and socioeconomic development [2]. Studies have shown that the degradation of grassland in Xilingol reached to 64% of total area because of the global climate change and expansion of usage and intensity in grassland types [18] The environmental problems such as sand storm, drought, and desertification became progressively worse [19], bringing adverse effect on local animal husbandry production and ecological environment [20]. We make use of the MODIS NDVI and meteorological data to monitor the dynamic of vegetation and drought in Xilingol grassland and discuss the drought impact on vegetation at different time scales This will have an important theoretical and practical significance to the spatial-temporal change pattern of vegetation in grassland, rational use of limited grassland resources, effective management and forecast the impact of climate change on grassland ecosystem, and risk assessment and early warning on the natural disasters in grassland pasturing area [21]

Data and Method

Results and Discussion

Conclusions