| Land use and land cover show the spatial pattern of the surface of the earth, and its change is closely related to many kinds of environmental problems, The emission of greenhouse gases such as C02 is one of the most serious environmental problems. The net primary productivity (NPP), as the main research content of carbon cycle, is the key indicator of terrestrial ecosystem, and reflects the carbon sequestration capacity of vegetation. This paper researched the changes of land use and simulated the vegetation net primary productivity of North Korea, in order to provide basis for carbon cycle and construction of ecological think-tank in North Korea.Based on the object classification of ENVI, this paper used landsat remote sending images to interprate the land use classification maps in generated 2000 and 2010 for eastablishment of a land use/cover database, calculated the land use and used the transfer matrix and mathematical models to analyze its change characteristics;on the other hand, this paper also put datas of temperature, precipitayion solar radiation through ordinary kriging interpolation and MODIS NDVI into CASA model to simulate NPP through writing IDL language, and then verified the simulation results, analyzed NPP from space and time aspects, exppored the influence facters of NPP.The main conclusions are as follows:(1) The main land use cover of the research area is woodland, followed by farmland. During 10 years, the forest land areas have decreased, the cultivated land areas have increased, the areas of grassland and unused land have reduced in different degree, the areas of water, construction land have increased in different degree. Among them, the growth of construction land is the largest and the speed and space of change is the most significant, the deduction of grassland is the largest;the areas of paddy field, dry land, broad-leaved forest, water, construction land presente increasing trend, the areas of coniferous forest, mixed forest, grassland and uneused presente decreasing trend; in the land use transfer, the transfer between dry land and paddy field, between coniferous forest、mixed forest、broad-leaved forest transfer are the most significant.(2) In spatial distribution, the lowest NPP value areas are distributed in coastal sandy land, unused land, inland river and Changbai Mountain near the lake mouth;the lower value areas are mainly distributed in the west coast, east coast and Changbai Mountain area; the highest NPP value areas locate along the eastern coast; the administrative order of NPP means is that Kaesong> Hamgyungnam-do> Ra Son> P’ yongannam-do> Hwanghaebuk-do> Gangwon-do> Hamgy o ngbuk-do> Hwanghaenam-do> P’ y (?) nganbuk-do>Chagang-do>Yanggang-do>Pyongyang>Namp’ o; the administrative order of NPP amounts is that Hamgyungnam-do> Chagang-do> Hamgyongbuk-do> Yanggang-do>P’ y6nganbuk-do>P’ y6ngannam-do> Gangwon-do> Hwanghaebuk-do> Hwanghaenam-do> Pyongyang> Kaesong> Namp’o> Ra Son.(3)During this 10 years, the average NPP and the total amount of NPP were increased, but the growth was not large. The average NPP of month showed single peak distribution, the time of NPP accumulation was mainly in summer and autumn, and the maximum of NPP was in July, and the time of June and September are the time that NPP accumulated largely.(4)The carbon sequestration order of land use:broad-leaved forest) mixed forest>dry land>paddy land>coniferous forest>grassland. From 2001 to 2010, the total amount of NPP was NPP that forest produced, followed by cultivated land, far greater than other land use types. During 10 years, the NPP of. forest and grassland have decreased, the NPP of cultivated land, water, construction land, unsed land have increased, the NPP value of broad-leaved forest is higher than the NPPs of mixed forest and coniferous forest, the NPP value odf dry land is higher than the NPP of paddy land. The change trend with time of different land use types is the same, the accumulation of NPP in summer was the most, and in other seasons NPP value were less. The NPP value of seasonal changes of different land differed in magnitude, the change of broad-leaved forest was the largest, and the average NPP of January and July were higher than that of other land use types of NPP.(5) The main factors that affect the NPP are temperature, precipitation, solar radiation, NDVI, land use types and area change. NDVI shows vegetation degree of coverage, the coverage of vegetation is mainly decided by the growth of vegetation development; the good combination of temperature and precipitation on plant growth has an important influence; compared to the solar radiation, the temperature and precipitation had more important on the NPP;the different physiological characteristics of land use and the different utilization use of weather conditions will have an impact on NPP production; The change of land use types also resulted in the change of NPP quantity. |
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