青海高原东部土地利用变化模拟与景观生态风险评价

为了研究西部大开发和退耕还林等生态工程对未来土地利用变化趋势的影响,将Gray-Markov模型和CLUE-S模型相结合,模拟自然情景、耕地保护情景和土地规划情景下青海高原东部农业区2020年土地利用覆盖状况,并分析3种情景下土地利用变化特征,采用景观格局指数和景观生态风险指数比较3种情景模拟结果。自然情景延续1999-2009年的发展模式,至2020年退耕还林/草633.98 km2,其他未利用地造林/草117.66 km2;耕地保护情景严格保护耕地,至2020年退耕还林/草142.00 km2,未利用地造林/草130.71km2;土地规划情景经济发展与环境保护并重,退耕还林/草444.18 km2,未利用地造林/草333.75 km2。景观格局指数和景观生态风险指数均表明土地规划情景下的模拟结果布局较合理。研究表明,新增建设用地扩张的同时加强生态保护,仍可以保证区域景观生态安全。该研究可为中国西部的土地利用规划和政策制定提供参考。

Simulation of land-use changes and landscape ecological assessment in eastern part of Qinghai Plateau

Abstract: West Development and a series of ecological environmental regulation projects have been carried out in West China since 1999. In order to study the effects of West Development and ecological projects on future land use change, this paper combines Gray-Markov model and CLUE-S model to simulate land use/cover change in 2020 in the Eastern part of Qinghai Plateau. The validation of the CLUE-S model is verified by comparing the predictive model to a null model, and the former is higher in agreement due to the quantity and location of the latter, while they have the same agreement due to chance. According to actual conditions in the Eastern part of Qinghai Plateau three scenarios (natural scenario, farmland protection scenario and planning scenario) are designed, then it analyzes the changes of land use and land cover in these scenarios and assesses them by landscape pattern index and landscape ecological risk index. The forecast of land structure based on Gray-Markov model show that construction land and forest increase greatly due to West Development and a series of ecological environmental regulation projects, especially in the planning scenario, while irrigation farmland and dry farmland descend in the study period from 2009 to 2020. The development mode of the natural scenario is the same as that from 1999 to 2009, and there will be 633.98km2 farmland returning to forest and grassland and 117.66km2 unused land turning into forest and grassland by 2020; the farmland protection scenario strictly protects arable land, with 142.00km2 farmland returning to forest and grassland and 130.71km2 unused land turning into forest and grassland; the planning scenario which integrates development of economic and environmental protection, will have 444.18km2 farmland returning to forest and grassland while 333.75km2 unused land for afforestation. The predictive results are assessed by four class-level indexes including number of patches (NP), percent of landscape (PLAND), largest patch index(LPI), landscape shape index(LSI), and eight landscape-level indexes comprised by NP, patch density(PD), edge density(ED), LSI, contagion(CONTAG), Shannon's diversity index(SHDI), Shannon's evenness index(SHEI), and aggregation index(AI). Class-level indexes indicate that woodland has the least landscape fragmentation in the planning scenario. Five of eight landscape-level indexes, containing ED, LSI, SHDI, SHEI and AI, indicate that the planning scenario is the best scenario of the three in intensive use of land. In conclusion, landscape evaluation and landscape ecological risk index show that the simulation results of the land planning scenario is reasonable. The planning scenario comprehensively coordinates the superior index, the goal of regional economic development and ecological protection, paying attention to the development of economic construction as well as the ecological environment construction, and improving or restoring the damaged ecosystem function to improve the overall productivity and stability of the landscape ecological system. Although new construction land expands strongly, strengthening ecological protection can still guarantee the regional landscape ecological security. Therefore, to 2020 the Eastern part of Qinghai plateau should continue to carry out the conversion of farmland to forest, but slightly lower than the strength during the period of 1999 to 2009.This study can provide evidence for the planning and land use policy formulation in the Western part of China.