| Aiming at the Huanghe-Huaihe-Haihe (HHH) zone, which was the main agricultural area, the quick economic development area, and the common boundary from one to two step terrains in China, the studies of vegetation cover variation and its impact on regional climate and water resource had been carried out. The results had important scientific significances and applied values.In terms of the analysis methods of trend, correlation, EOF, SVD, PCA and numerical simulation etc., the temporal & spatial characteristics of vegetation cover variations and the relationship between the climate factors and the ones in HHH zone were analyzed based on the longer term NOAA/AVHRR GIMMS NDVI data (1981.7-2003.12). The types of vegetation cover and their transforming each other more than 20 years were conducted by remote sensing classification on the cover. By using the social economic and climate factors, the driving forces and driving mechanism of the change of vegetation cover in HHH zone were researched on the basis of mean NDVI. The numerical simulations on the impact of the urbanization and the farming vegetation variation on regional climate and water resource of HHH Zone by use of RegCM3 for 5 years (2001-2005) were carried out. The main conclusions included:(1) The temporal & spatial variations of vegetation cover of 1982-2003 in HHH zoneThe vegetation NDVI had an indistinct increase trend in whole HHH zone in 1982-2003, but there was a negative change trend in parts of area. The negative change trend existed not only in the quick economic development areas but also in parts of forest areas.In HHH zone, the annual NDVI variation of agriculture vegetation was bi-peak style (except annual harvest crop), but the natural vegetation was single peak style. The annual mean NDVI had a obvious rise trend in grassland, annual harvest crop and biannual irrigated & dry harvest crop vegetation, a less rise trend in needle leaf forest, board lead forest and shrub etc. forestland, a middle rise trend in meadow and biannual harvest crop.According to the yearly variation of NDVI pixel numbers for the different periods of time and different level, the pixel numbers of higher cover forestland increased continuously, the middle cover agriculture vegetation, grassland and shrub pixel numbers had decreasing trends, and sparseness vegetation and lower cover vegetation had little variation. Considering dynamic change trend of pixel number for different vegetation, the no change pixels for forest priority to natural vegetation occupied the dominant status, the no change pixels were little much than the increasing pixels for shrub and all agriculture vegetation, and the increasing level pixels were the main for grassland.(2) The relationship between vegetation and climate factors of 1982-2003 in HHH zoneFor the whole vegetation in HHH zone, yearly mean temperature was the strongest sensitivity factor, the follow was yearly precipitation and evaporation. To the seasonal scale, temperature and precipitation were the most sensitive factors, but the sensitivities of humidity and evaporation were weaker relatively. The sensitivities of temperature was the strongest, precipitation was the follow for the agriculture vegetation. But the sensitivities of precipitation was the strongest, temperature was the follow for the natural vegetation. Partitioning the detail vegetation types, in the agricultural vegetation, annual harvest crop had a strongest sensitivity to precipitation, the follow was temperature and evaporation. Biannual harvest crop part of which could be irrigated or biyearly tri-harvest dry crop had a strongest sensitivity to temperature, the follow was precipitation and evaporation. Biannual irrigation & dry harvest crop had a strongest sensitivity to temperature, the follow was evaporation and precipitation. In natural vegetation, the precipitation was the most sensitive factor to grassland, meadow and shrub, the follows were needle leaf forest and board lead forest. And the temperature was the most sensitive factor to the board leaf forest and needle lead forest, the follow was shrub, but it was the weakest to the grassland and meadow.The movement rules of green wave and brown wave for vegetation were analyzed. The results showed that vegetation growth season prolonged about 10.9d/10a in HHH zone with the climate change.(3) Vegetation cover changes monitoring by remote sensing in HHH zoneBased on the data of multi-yearly NDVI,Holdridge bio-region index and other supplementary data, the vegetation types of 1982, 1992 and 2002 in the HHH zone were classified by the ways of PCA and unsupervised classification methods, and the classification accuracy was very high. The results showed that the whole vegetation cover situation in HHH zone during in the last 20 years had no distinct changes, and its change rate had a little decline, while looking at the internal variation of annual bi-harvest crops exhibited a rise trend during 20 years, but the change speed was slowing. Annual irrigation & dry bi-harvest farming and brushwood vegetation had a declining trend during in the last 20 years. By the influence of climate, the changes of dramatically situate were in common boundary of theâ… andâ…¡step and around 400 mm annual rainfall line, hilly area in Shandong province and the downstream of Huaihe river in HHH zone. But the vegetations changes in plain zone were slower.(4) Study on the driving forces and driving mechanism of the change of vegetation cover in HHH zoneThe farmland vegetation area received the common drive of climate and the society factors, but climate factors were the main driving forces for annual harvest crop or biannual irrigated and dry harvest crop, and society factors were the main driving forces for biannual harvest crop or biyearly tri-harvest dry crop.In annual harvest crop area, the averaged temperature, yearly relative humidity, temperature, precipitation, and relative humidity of spring season, temperature of winter and society factors are positive driving forces, but temperature of summer, precipitation and relative humidity of autumn are negative driving forces. For biannual harvest crop, the precipitation and relative humidity of autumn, the farmland area and the total population are negative correlate to the change of NDVI, while the temperature of autumn and winter is positive correlate to the variance of NDVI. For biannual harvest irrigated and dry land crop, the precipitation and relative humidity of autumn, the yearly relative humidity are the negative driving forces, and the society factors are positive driving forces.In natural vegetation area, where mainly are forest land, the yearly relative humidity and precipitation of spring are the driving forces to the change of NDVI. In brush and shrub area, the change of NDVI is driven by the precipitation and relative humidity of autumn. In grassland and rare tree bush grassland district, the main driving forces are human factors, and the driving mechanism is that farmland and cropping sown area are negative to the change of NDVI, but society factors are positive.(5) Numerical simulation on the impact of vegetation variation on regional climate and water resource of HHH Zone Numerical simulations had been carried out over HHH zone by using RegCM3 for 5 years (2001-2005). The results showed that the large scale vegetation variation in the zone had notable effect on regional climate and water resource. Neither the urbanizing nor the farming could weak the summer monsoon, decrease rainfall and water resource and make the temperature increase. The variations resulted in the autumn drought happen easily, the floods became more severity because of the increasing of run off in summer. The vegetation changes caused the decreasing of soil moisture holding capacity, and stimulated the vegetation degradation inversely. Accordingly, the climate abnormity and the shortening of water resource in HHH zone transformed tempestuously, and led to the ecological environment deteriorating.To sum up, the study filled up some blanks on vegetation cover and its impact on climate and water resource in HHH zone by using some new and integrity remote sensing etc. data. Multi domains on LUCC study were conducted, such as the time & space variation laws of vegetation cover, the relationship with climate factors, classification methods and dynamic change rules, driving forces and driving mechanism, and numerical simulation about variation effects etc by some new data, methods and means. Some new results were achieved. Meanwhile, some problems which need be improved urgently were found. To solving the problems would improve on the understanding on the variation rules of vegetation cover and advanced the numerical simulation precision on the vegetation variation effects.
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