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

Hindawi Mathematical Problems in Engineering Volume 2017, Article ID 5209173, 11 pages https://doi.org/10.1155/2017/5209173 Research Article Analysis of Drought Characteristics in Xilingol Grassland of Northern China Based on SPEI and Its Impact on Vegetation Siqin Tong,1,2,3 Yuhai Bao,2,3 Rigele Te,2,3 Qiyun Ma,1 Si Ha,1 and A. Lusi1 1 School of Environment, Northeast Normal University, Changchun 130117, China College of Geographical Science, Inner Mongolia Normal University, Hohhot 010022, China 3 Inner Mongolia Key Laboratory of Remote Sensing and Geographic Information System, Hohhot 010022, China 2 Correspondence should be addressed to Yuhai Bao; Received 20 September 2016; Revised 11 November 2016; Accepted 7 December 2016; Published 18 January 2017 Academic Editor: Hasi Bagan Copyright © 2017 Siqin Tong et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 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. 1. 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 also has vital function on animal husbandry production and socioeconomic development [2]. However, grassland is one of the most vulnerable ecosystems as well, which is seriously affected by climate changes [1]. Global climate change, 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]; moreover these changes will be exacerbated the formation of disastrous elements [4] and then will have a profound impact on changes of vegetation growth, productivity, and accompanying socioeconomic progress [5, 6]. Drought is one of the most serious natural disasters in the world. It has the characteristics of high frequency, wide range, and long duration [7]. It also has great influence on agriculture, water resources, natural ecosystem, and society, and then it brings huge economic losses, famine, epidemic, land degradation, and other negative effects [8]. Because of the global climate warming, drought occurs frequently and there is a clear upward trend. It has a direct impact on the development of agriculture and animal husbandry in Mongolia steppe [9] and accelerates the desertification and causes severe sand storm [10]. Therefore, drought assessment and monitoring are essential to reducing the losses and ensuring the safety of human being and property. Although 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]. The drought index can be used to quantify the intensity and duration of drought, as well as the occurrence of spatial extent [12]. In this study, the standardized precipitation evapotranspiration index (SPEI) 2 Mathematical Problems in Engineering 100∘ E 110∘ E 120∘ E 55∘ N 55∘ N DWQ XWQ ABG 50∘ N 50∘ N XLHT SNTZQ Hulunbuir # ELHT SNTYQ XHQ ZXBQ ZLQ Stations Meadow steppe Typical steppe Steppe desert Desert steppe DLX TPSQ N Hinggan 45∘ N 45∘ N Tongliao Xilingol Chifeng Baotou Wulanchabu 40∘ N Bayan Nur China Inner Mongolia Hohhot Alxa 40∘ N Wuhai Ordos (km) 0 100∘ E 110∘ E 90 180 360 120∘ E Figure 1: Location of study area, spatial distribution of meteorological stations, and grassland types of Xilingol. was selected to analyze the dynamics of drought. It is widely used to analyze drought in various fields, because it not only considers the role of precipitation and evapotranspiration in drought causes, but also retained the sensitivity of SPI and PDSI index to temperature and precipitation, and it also has advantage of multiscale and multispace [13]. The frequent occurrence of drought and long duration hinder the normal green up and growth of grassland, cause the decrease of productivity in grassland, and pose a great threat to the sustainable development of the economy of animal husbandry. Therefore, it is of great significance to monitor and reveal the impact of drought to vegetation and to study the relationship between climate change and terrestrial ecosystem. In recent years, a great number of researchers have studied the relationship between vegetation and drought; however, the current study mainly concentrated on the relation between vegetation and single climate factor [14–17]. And this is not able to reflect the effect of climate change on vegetation [7]. On the other hand, most studies focused on a watershed analysis and have less attention on the correlation analysis of vegetation and drought, especially the drought impact on vegetation in Xilingol grassland which has not been reported yet. Xilingol grassland locates in the north of China, and it is one of the three major natural grasslands of China and the typical temperate grassland of Eurasia, as well as the most complete preservation of word’s temperate grassland in the Central Plains plants. However, due to the typical continental climate and fragile ecological system, Xilingol grassland is vulnerable to global climate change and human activities. 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 desertifi (...truncated)