| The Loess Plateau is one of the major regions for the farming, forestry, and husbandry industry in China, whose agriculture development concerns are not only related to the living standard of its own people but an overall improvement of its ecosystem. As a bridge connecting man with nature, agroecosystem sustainable development lays the foundation for human society’s existence. Since the agroecosystems on the county level are the building blocks of the whole agroecosystem, it is necessary to adopt the sustainable development mode on the county level, which is of strategic importance to realizing the sustainable farming development of the Loess Plateau in China.With its different geographic features-the west being the typical mountainous terrain of the Loess Plateau, the central to west loess hills, the east and south alluvial plains, and the whole a typical transitional region of the Plateau from mountainous terrain to alluvial plain, the agroecosystem development pattern vary in different regions in Wenshui County, Shanxi, it could be considered that Wenshui can roughly represent the general situation concerning the Plateau’s agroecosystem. Based on the above ideas, Wenshui belonging to Lvliang, Shanxi located in east of the plateau was taken as the subject of this article.First, with GIS spatial analyzing function, the changes of the county’s land use and landscape patterns over the period of 1976 to 2009 were mapped according to its Mss data in 1976 and five sets of TM photo-topographic maps obtained from land satellite for the years of 1990,2000,2005, and 2009. Then, the trend on the land use over the coming 20a was predicted by using both Markov Chain and Gray System methods respectively on another five sets of TM photo-topographic maps from 2005 to 2010, and the results predicted by the two methods were compared. The functional agroecosystem division of Wenshui was conducted by using ARCGIS, TWINSPAN, DCA and high-resolution photographic data. By overlapping the results of the eco-functional regionalization of Lvliang City and Wenshui County, the agroecosystem functional regionalization was obtained. The indices for the appraisal system of agroecosystem sustainability for Wenshui County was acquired by theoretical analysis, frequency statistics, and specialist consultations and AHP, and the sustainability of the agro-ecosystem in Wenshui was evaluated from 1990 to 2009. The supporting degree for whole agroecosystem development was characterized by resource-development (R-D) index and environment-development (E-D), and each subsystem’s contribution to the whole system was analyzed by PCA (principal component analysis). On the basis of the above-apprising, the restricting factors to the system’s sustainable development were explored, and the sustainable developing modes and management strategies for the agroecosystem sustainablity in Wenshui were discussed, respectively.The results from the spatial-time changes in the land use indicated that the construction land and waters in Wenshui have increased. The farm land, woodland, grassland and uncultivated land have decreased, and the farm land mainly was transformed into the construction land from 1976 to 2009. The fastest conversion occurred to construction land with the water area, farm land, uncultivated land, grass land and woodland coming one after another in sequence. With continuous shrinking of farm land, the county would be hard pressed for it.The result from the dynamic simulation and prediction of the land utilization in Wenshui showed that the farm land and grass land would decrease on large scale, while the woodland and construction land would increase significantly, uncultivated land roughly on the dropping side and waters on the rise in the coming for 20a. The change in the land use pattern, especially the continuous great decline of the farm land would impose a fundamental effect on the agroecosystem and a great stress.The results from the change of the landscape pattern demonstrated that the diversity of the landscape in Wenshui from 1976 to 2009 was wider and human interference was having an increasing threat to shatter the landscape. The change of the landscape pattern was dependent upon the change of natural factors in some degree such as the topography and climate, but much more dependent on that of the human factors such as social economy and population growth. The complicating, irregulating and fragmenting of the farm landscape resulted in the decline of the agroecosystem landscape, sped up the fragmenting of agroecosystem as well as weakened the abilities as in self-restore, self-sustain, and self-development.Based on the pattern of the land use, the agroecosystem in Wenshui was divided into three regions by ARCGIS, TWINSPAN and DCA together, namely the central, western and eastern agro-development regions. The first axis from the left to right on the DCA reflected the altitude from lower to higher, and the agroecosystems were the eastern, the central and the western development regions in the same sequence. The second axis reflected the ratios among the farming, forestry and animal husbandry with lower ratio of forestry and higher ratio of animal husbandry to the top. Combining Eco-Functional Regionalization of Wenshui ", " Eco-Economic Regionalization of Wenshui " and the results of agroecosystem Regionalization of Wenshui from ARCGIS, TWINSPAN, and DCA, the agroecosystem in Wenshui was divided into:(1) Agroecosystem Type of Mountainous Region in Cang’erhui, (2)Agroecosystem Type of Diluvial Plain, and (3) Compound Agroecosystem Type of Loess Hilly Region.The appraisal of the sustainability of the agroecosystem in Wenshui showed that the population subsystem was enlarged by a small scale with fluctuations during the period of 1990 to 2009, while the economic subsystem followed a rising-stabilizing-rapid rising pattern; the society subsystem demonstrated an overall fast rising trend, which contributed to the improvement of the agroecosystem sustainability greatly, the resource subsystem showed a relatively stable trend, and the environment subsystem had some minor ups and downs but began to improve slightly in recent years. Among them, the society subsystem contributed the most to the agroecosystem while the resource subsystem the least to the agroecosystem sustainability of Wenshui.The analysis of the R-D and E-D compound indices showed that the agricultural resource status was imposing more and more pressures or obstacles on the population, economic and social development in Wenshui. The environment sustainability deteriorated gradually, which resulted in restricting its agricultural economy and social development on some degree.The ordination of the agroecosystem sustainability by PCA and regression analysis with the five subsystems and agroecosystem sustainability showed that:The subsystems’contributions to the whole county agro-ecosystem’s sustainability were sequenced in magnitude from large to small as follows:the society, economy, population, environment, and resource subsystems.In the long run, the restricting factors on the agroecosystem sustainability included the shrinking of the farm land, inferior agro-technology and lack of agro-technicians for long-term period, while the environmental pollution and soil and water erosion for mediate-term period, and the inappropriate ratio among farming and forestry and animal husbandry and mono-structuring within farming for short-term period.Based the regionalization of agroecosystem of Wenshui, the different developing stages for the different subsystems and involving with each restricting factors, the strategies for developing modes in Wenshui could be concluded as:(1) The package modes for alluvial plain including the "grain-alcohol-livestock-fertilizer" mode, the "grain-fowl-pig-methane-fertilizer" mode, the "forest fruit-economic crop" 3-D mode with their related techniques, a "farm field and forest net" pattern, a "green vegetable" pattern and a compound eco-breeding plant pattern. (2) The package modes for loess hilly region mainly including an "around the mountain to develop economy" pattern, an eco-economic valley pattern, and an eco-orchard pattern. (3) The package modes for Cang’erhui mountainous region mainly including the compound operating pattern for farming and forestry in mountains and a "sight-seeing agriculture" pattern. (4) Mode of the sustainable developing of agroecosystem of intensive cultivation for Helianthus tuberosus in alkaline land.Finally, the sustainable strategies for the agroecosystem in Wenshui were discussed, including:never surpassing the alarming line for minimum farm land to ensure the resource, initiating recycling demonstration bases, pushing forward agricultural restructuring, strengthening agroscience and technology research and application and enhancing financial investment by the government to improve the developing of the recycling economy in agriculture. |
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