科研之友
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摘要
Drought is a natural disaster caused by long-time water shortage and uneven water distribution, which is one of the most common disasters around the world. Under the background of global warming, droughts have become more and more frequent and devastating, causing negative impacts on agricultural production, ecological environment and social economy. For the protection of vegetation and crops, it would be of practical significance to investigate how vegetation develops under the influence of drought which varies in time and space. This research applied the standard precipitation evaporation index (SPEI) derived from high spatial resolution dataset of precipitation and evaporation, as well as the newly published normalized difference vegetation index (NDVI) which represents the growth condition of vegetation on land. Mann-Kendall (MK) test and correlation analysis were taken to study the spatial and temporal evolution of SPEI and NDVI at catchment scale with the help of ArcGIS 10.1 software. The results of the research illustrated that: 1) The MK value of SPEI at catchment scale showed great coincidence with that of the 4189 grid points both in time and space, indicating the feasibility to investigate the response of vegetation growth under the influence of meteorological drought at catchment scale. SPEI was getting increasing slightly at different time scales during 1962-2012, indicating that China as a whole was being more humid. However, taking the time series of 1982-2012 as the research object, China was getting drier slightly at different time scales. In space, both at annual and at seasonal scale, drought trends were mainly detected in catchments in the Loess Plateau area, Northeast and Southwest China, while catchments in Northwest China presented significant humidifying tendency. 2) The NDVI value of the whole China was upgrading with time during 1982-2012, among which the NDVI in spring, growing season and whole year had a significant increasing trend. In space, some catchments of northern Xinjiang and Northeast China demonstrated a significant downgrading tendency, while the upgrading tendency was different owing to different time scales. 3) At annual scale, 56 of the 209 catchments showed significant positive correlation (P<0.05) between SPEI and NDVI, and most of them were located in north Xinjiang, and northern and northeastern China, which indicated that vegetation in arid and semiarid area was significantly affected by droughts. At the same time, negative correlation was mainly distributed in southern China (few of them passed the significant level of 0.95), indicating that droughts in southern China exerted little influence on vegetation growth. 4) Correlation analysis between seasonal NDVI and SPEI showed that in summer and autumn, catchments with positive relation mainly occurred in north area, while catchments with negative correlation mainly occurred in Southeast China and the middle and lower reaches of the Yangtze River plain. In spring and winter, negative relation came to dominate, which mainly occurred in Northeast China, the Yangtze River Basin and most catchments in Southeast China. Lag-relation analysis between seasonal NDVI and SPEI one or two seasons early showed similar correlation distribution as the result of relation analysis without lag. 5) For most of the catchments, air temperature, precipitation and evaporation exerted significant influence on NDVI of vegetation;among them, temperature played a leading role on the vegetation growth in catchments in southern China, while precipitation played a leading role on the vegetation growth in catchments in northern China. Our study on the relationship between meteorological drought and vegetation growth can provide a scientific basis for drought predication and precaution, and thus help to guide agricultural production and protect vulnerable ecosystems.
- 出版日期2016-7-15
- 单位华南理工大学
