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| Vegetation cover changes and their relationship with rainfall in different physiognomy type areas of Loess Plateau |
| Liu Zhihong1,Guo Weiling2,Yang Qinke2,Guo Yanfen1,Zhu Xiaoxiang3,Li Rui2 |
| 1.Department of Resource and Environment,Chengdu University of Information Technology,610225,Chengdu;2.Institute of Soil and Water Conservation,Chinese Academy of Science and Ministry of Water Resource,712100,Yangling,Shaanxi;3.National Satellite Meteorological Center,100081,Beijing:China |
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Abstract Vegetation play a very important role in controlling the soil and water loss in Loess Plateau.Based on the NOAA/AVHRR month maximum value composite NDVI(Normalized Difference Vegetation Index)data of in July from 1988—2005,the spatial and temporal distribution of NDVI in different physiognomy areas of Loess Plateau was analyzed and the vegetation changes between the pre-and-post phases of the Conversion from Farmland to Forest was compared.The correlation between NDVI and rainfall in the same term was established to analyze the rainfall impact on NDVI.And also the impact on NDVI from the policy of Conversion from Farmland to Forest was discussed roughly.The results show that the average NDVI is 0.29 in the whole Loess Plateau,between 0.30-0.40 in plain,stony mountain,low loess mountain and loess tableland,between 0.18-0.22 in Liang shape loess hill,Mao shape loess hill,and sand loess hill,and lower than 0.15 in other regions.The vegetation changes between the pre-and-post phases of the Conversion from Farmland to Forest are different and show a zonary distribution from north-east to south-west in different physiognomy areas with a gentle increase in whole Loess Plateau about 4%,a 10% increase in the principle part of Loess Plateau,a little decrease in wind erosion sandy hill and Mao shape loess hill region.Moreover,the NDVI in Wuqi County has a great increase with 40%,higher far than the average increase value 14% in same Liang shape loess hill region.They are positive correlations(R2>0.60) between the maximum NDVI in July and the cumulate rainfall from May to July in those physiognomy type areas except in the rocky mountainous region,low loess mountain region and plain region.Some conclusions have been obtained that rainfall plays a decisive role in the spatial distribution of NDVI,and also determine the NDVI increase and decrease in the principle part of Loess Plateau in different time phases.The policy of the Conversion from Farmland to Forest has exerted an active action on the increase of vegetation cover through the model demonstration of Wuqi County for its available fund,a suitable revegetation selection between grass and forest based on its terrain and rainfall condition,and a perfect protection measure.
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Received: 30 April 2009
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