灌区土地利用变化驱动因素分析——以内蒙古河套灌区为例

Driving Forces of Land Use Changes in Irrigated Agriculture

从渠系空间分布和土壤类型空间分布两个方面探讨灌区土地利用变化的驱动因素,对于理解和揭示灌区土地利用变化的原因和机制具有积极意义。本研究以内蒙古河套灌区为例,应用GIS的空间分析模块,利用1985与2000年2期土地利用数据,通过计算不同土地利用类型距离渠系的平均距离以及不同土地利用类型在不同土壤类型上所占面积百分比,分析了渠系及土壤类型的空间分布对灌区土地利用格局变化的影响。在距离渠系较近处,由于长期灌溉,再加上灌排设施不配套,地下水位逐渐抬高,导致盐碱地比重明显增加;在距离渠系较远处,受到水源与水量的限制,主要表现为耕地比例的下降和荒草地比重的上升。土壤类型对土地利用变化的影响主要表现为原本质量不高的土壤,经过长期的耕作等人为干扰,又没有合理的保护措施,部分耕地逐渐退化为荒草地及盐碱地。

Land use/cover change and its driving force have become the hot topic of geographers and ecologists within recent years. Study areas involved cities, towns, deserts and oasis, while less attention was paid to irrigated agriculture. More attention was paid to water-saving irrigation, pollution and canal system modification in irrigated agriculture. In fact, study on land use/cover change and its driving forces in irrigated agriculture have an important theoretical significance. In irrigated agriculture, canal system and soil types have an important impact on land use change. Hetao irrigated agriculture in Inner Mongolia was taken as a case study and the impact of irrigation canal distribution and soil type on land use pattern change was analyzed based on GIS technology. The mean distance to irrigation canal of each land use type and area percentage of different land use type on different soil types was computed with the support of GIS software ArcINFO and ArcView. It is found that the area of alkali-saline land increases near the irrigation canal while the area of farmland declines and wasted grassland increases in the areas far from the canal system. The former is mainly due to elevated groundwater level with long time irrigation and poor drainage system and the latter is mainly caused by limited water resources. Poor soil quality with long time tillage and no rational conservation practice cause some farmland degraded to wasted grassland and alkali-saline land. Land use/cover change and driving forces in Hetao irrigated agriculture are complicated, and it is a product of human activities and natural forces in a long-time period. In further study, water diversion form the Yellow River, groundwater level materials, natur~ factor including temperature and precipitation, social factors including population, economy and government regulation and factors mentioned above should be analyzed by synthesis method to better understand land use dynamics and promote sustainable development in Hetao irrigated agriculture.