基于遥感的中国陕北地区近20年耕地变化及其对农田生产力影响的定量评估

本文以中国退耕还林生态工程重点区域陕北地区作为研究区,对比其前后两个10年的耕地资源空间分布格局,并进一步分析耕地变化对农田生产力的影响。论文基于中高分辨率卫星遥感数据,经人机交互目视解译并结合实地验证,生成陕北地区1990、2000和2010年耕地现状以及前后两个10年耕地变化时空监测数据集。进而运用光能利用率遥感模型,结合中分辨率、长时间序列卫星遥感数据估算陕北地区农田净初级生产力,分析耕地变化对农田生产力的影响。结果表明,陕北地区耕地面积及其生产力在研究期前10年小幅增长,后10年明显减少。耕地增加的主要原因是为满足当地人口的粮食需求以及弥补城市建设对耕地的占用,大面积草地和未利用地被开垦。耕地减少的最主要原因是生态退耕,城市化也是耕地减少的原因之一。总体而言,20年来陕北地区耕地资源总面积净减少42.56%;受耕地面积变化的影响,同期农田净初级生产力下降了41.90%。研究对于评估陕北地区耕地安全和粮食安全,指导区域土地利用科学规划具有重要意义。

Cropland Dynamics and Their Influence on the Productivity in Northern Shaanxi,China, for the Past 20 Years: Based on Remotely Sensed Data

In this paper,we mainly focused our research on northern Shaanxi district,which is a pilot area of the Grain for Green Project.We compared the spatial distribution patterns of croplands and their productivity for the past 20 years（from the end of the 1980 s to 2010）.Cropland dynamics for the past 20 years were interpreted from medium- and high-resolution remote sensing images（Landsat TM/ETM＋）.In addition,using the GLO-PEM and AGRO-VPM models with a medium resolution and long time series remote sensing dataset（AVHRR/MODIS）,net primary productivity（NPP） and its relationship with cropland were estimated.Finally,the effect of cropland change on productivity was analyzed.The results show that during the first decade of the research period,cropland area and productivity in northern Shaanxi experienced a small boost,while in the latter decade,both cropland area and NPP were significantly reduced.The main cause of the increase in cropland was the reclamation of large area of grassland and unutilized land to meet the food demands of the local population as well as to compensate for the occupation of urban constructions.While the main cause of the decrease in cropland was the implementation of the Grain for Green Project.In addition,urbanization was also a key factor.Overall,during the past 20 years,the total area of cropland in northern Shaanxi decreased by 42.56%,and cropland NPP dropped by 41.90%.This study is of great importance for the assessment of regional cropland security,food security and scientific planning of regional land use.