GEOGRAPHICAL RESEARCH ›› 2020, Vol. 39 ›› Issue (5): 1200-1214.doi: 10.11821/dlyj020190399

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Spatiotemporal variation of NDVI in different ecotypes on the Loess Plateau and its response to climate change

SUN Rui1,2, CHEN Shaohui1(), SU Hongbo1   

  1. 1.Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
    2.University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2019-05-17 Revised:2019-11-05 Online:2020-05-20 Published:2020-07-20
  • Contact: CHEN Shaohui E-mail:chensh@igsnrr.ac.cn

Abstract:

Understanding the spatio-temporal changes of vegetation and its climatic control factors can provide important theoretical basis for the protection and restoration of ecological vegetation. Based on MOD13A1 and meteorological data, the spatial patterns and trends of Normalized Difference Vegetation Index (NDVI) in the Loess Plateau were analyzed. The response of NDVI to temperature and precipitation was analyzed on the annual and monthly scales. The results showed that the vegetation coverage in the study area was improving continuously, and the climate showed a warm and wet trend. Of the degraded areas in the Loess Plateau, some 83.77% (area only 5.79%) was below 2000 m and the number of vegetation degradation types were not significantly reduced. The altitude distribution and degraded proportion of different vegetation degraded areas were significantly different. The degraded area ratio of wetland was the highest (23.91%), followed by cultivated land (11.88%). On the annual scale, the area with positive correlation between NDVI and precipitation was higher than that of temperature, and about 75.06% of the area was affected by precipitation. Precipitation was the main factor affecting the growth of shrub land (altitude distribution < 2200 m, the same below), cultivated land (< 3000 m), grassland (< 3000 m) and bare land (600-3700 m). Temperature was the main factor affecting the growth of forests (< 1000 m, 1700-3700 m) and wetlands (>2500 m). On the monthly scale, the overall response lag period of the Loess Plateau to temperature was one month, and there was no response lag period to precipitation. The response lag period of different vegetations to hydrothermal conditions was obvious. Grassland (lagging altitude distribution 710-3800 m, the same below), wetland (> 860 m), cultivated land (< 150 m, 350-2250 m, 2550-2900 m, 3430-3560 m) and bare land (760-2100 m) had a one month lag effect on temperature response, while forest (< 2900 m, > 3450 m) and shrub land (< 1270 m, > 1860 m) had no lag effect on temperature response, and six types of vegetation had no lag effect on water condition response. With the time lagging, the proportion of precipitation control gradually decreases. Temperature becomes the main factor affecting vegetation. The main control of water and heat and the lagging distribution of response are obviously affected by altitude. The proper vegetation type should be selected in different areas and altitudes, and water resources should be used reasonably for vegetation restoration.

Key words: Loess Plateau, hydrothermal conditions, land cover, Normalized Difference Vegetation Index