基于地学规律的科尔沁沙地土地整治与生态修复规划方法

内蒙古科尔沁沙地历史上曾是科尔沁大草原,现在是农牧交错区,该区的土地利用关系到生态安全、国家粮食安全和农民生计。该区域“坨甸相间”地貌特点造成不同地形部位土壤含水量存在差异,降水量年际变化大。通过卫星影像数据解译出土地利用/覆被类型图与土壤图进行叠加,获得了显性沙地和隐性沙地数量与分布信息。首先保留耕地以外的其他地类,再利用卫星影像数据反映不同降水年型耕地的归一化植被指数(NDVI),将偏欠水年NDVI低于平均值的耕地退耕还草,消除这些耕地的冬春沙化风险,以进行土地利用布局调整。这种直接利用遥感数据获取土地利用/覆被类型和耕地的NDVI进行土地利用空间布局调整的方法,十分简单实用。本文还根据地貌和沙地降水入渗快的特点,提出了与高标准农田建设模式不同但与区域地理环境相吻合的农田整治模式,即利用自然沙丘作为区域风沙防护工程,土地开发不做大平整,不修建灌溉系统,发展雨养农业。以上根据区域地理环境条件进行土地利用布局和确定农田开发建设模式,可将农业生产与荒漠化防治和谐结合在一起,实现土地可持续利用。

Land consolidation and ecological restoration in Horqin: Land use planning strategy based on geosciences knowledge

The Horqin sandy land in Inner Mongolia is the largest sandy land in China with a mean annual precipitation of 380 mm. Historically the sandy land was a prairie and nowadays it is a mixed farming and grazing zone. Today, farmlands occupy a large portion of the entire region, which has major implications for ecological security, national food security, and farmers’ livelihoods. Soil water content is conspicuously different at the dune top and in the inter-dune depression. Based on the large interannual variation in precipitation and the topographical features of sand dunes, the research objective was to overlay the soil and land use maps interpreted by satellite imagery to delineate the dominant and hidden sandy lands. Using NDVI data of different precipitation years as the discrimination criteria, cultivated land with low NDVI can be transferred to grassland to avoid the risk of desertification in the drier years. Adapted to the regional geographic environment in semi-arid regions, this method of optimizing spatial allocation of land use could be consistent with ecological and production needs while being uncomplicated. The study could be used as a functional model for reducing desertification in semi-arid areas by using sand dunes as wind protection, abandoning large-scale land leveling engineering and developing rain-fed agriculture. In other words, land-use allocation and farmland consolidation should be in harmony with the regional geographical environment. Combining agricultural production and desertification prevention is a sustainable land use planning strategy.