在区域尺度评价农田防护林对作物产量的影响对于农田防护林建设和经营管理具有重要意义。该文提出了一种基于遥感(remote sensing,RS)和地理信息系统(geographic information system,GIS)技术的农田防护林对作物产量影响的评价方法。首先利用多时相遥感影像识别农田防护林的经营阶段和和生长状态,建立农田防护林防护效应的综合判定模式；其次采用机制法,通过光、温、水、土逐级衰减,计算作物生产潜力,并基于遥感影像和光能利用率模型估算作物单产；最后构建农田防护林对作物产量影响的评价方法体系。基于该方法,在吉林省长春市北部的农田防护林重点建设区选择样区,评价了该区2009年农田防护林对玉米产量的影响。结果表明,农田防护林在一定程度上将会促进玉米增产。尤其在自然条件较差的低产区,农田防护林的增产作用更加显著,增产率达到8.85%；而在高产区,增产率约为2.4%,但是由于胁地效应的影响,在部分地区可能造成减产。因此,在农田防护林的规划建设中,应根据不同的立地条件,因地制宜,在占地面积最小的情况下,达到稳产增产的作用,实现农田防护林的最大防护效应。该研究丰富了在区域尺度研究农田防护林防护效应的技术方法,可以更加科学合理的评价区域尺度上农田防护林的增产效益,并为农田防护林的经营管理提供科学依据。

Accurately evaluating the effect of farmland shelterbelt on crop yield plays an important role in shelterbelt construction and management at regional scale.A method evaluating the farmland shelterbelt′s effect on crop yield based on remote sensing(RS) and geographic information system(GIS) was put forward in the paper.First, by using multi temporal remote sensing images combined with the theory of management for shelterbelt, the managing phase of the shelterbelts was recognized, and the shelterbelts were divided into 4 stages, including mature, pre mature, post mature and updated stage.Besides, the growth status of shelterbelts was classified as good, average and bad according to the value of normalized differential vegetation index(NDVI).Therefore, the decision rule of protection effect for farmland shelterbelts was established on the basis of managing phase and growth status of shelterbelts.Then the spatial distribution map of protection effect of shelterbelts was obtained by combining a simple model and GIS.In order to analyze the farmland shelterbelt's effect on crop yield under similar natural conditions and remove other affecting factors, with the support from mechanism methodology and GIS, the crop potential productivity was computed according to the factors such as radiation, temperature, precipitation, and soil.The study area could be divided into 3 regions, i.e.low, middle and high production area.Besides, based on the meteorological data and the in situ measured data of crop yield, absorbed photosynthetically active radiation (APAR) inversed by remote sensing, light use efficiency, and harvest index, the crop yield was estimated at regional scale with the light use efficiency model.Finally, on the basis of above results, including spatial distribution of protection effect, crop potential productivity and estimated crop yield by remote sensing, we proposed a method evaluating the farmland shelterbelt′s effect on crop yield.Taking a sample area in shelterbelts key construction region of northern Changchun as the example, the farmland shelterbelt′s effect on maize yield in 2009 was evaluated.The spatial distributions of protection effect of farmland shelterbelts and crop potential productivity subregions were obtained in study area.Besides, we estimated the maize yield in 2009 with the MODIS NDVI and the sampled data of maize yield.The result showed the absolute error of estimated maize yield in study area was 467.75 kg/hm², and the relative error was 5.43%, which met the needs of accuracy completely for crop yield estimation by remote sensing.The change of maize yield was analyzed in the subregions with different protection effect of shelterbelts and crop potential productivity in study region, and the results showed that farmland shelterbelt could enhance maize yield to some extent.Especially, in the lower production area with poor natural condition, the farmland shelterbelt could significantly increase maize yield, and the yield increase rate could be up to 8.85%.The yield increase rate was 6.81% and 2.4% in middle and high production area, respectively.Consequently, under the better nature condition, the protection effect on crop yield could be weaken.In high production area, tree was predominant in competition and would affect crops negatively, which could led to the reduction of crop yield in some places.Therefore, the planning and construction of farmland shelterbelts should be in accordance with local conditions, so that farmland shelterbelts could maximize the benefits by using the smallest area.For poor natural condition and severe wind area, the construction of farmland shelterbelts should be strengthened.But in an area with better natural conditions, the separation distance of shelterbelts network should be increased to weaken the negative effect of shelterbelts on crop yield.The research can not only enrich the technological means in protection effect of farmland shelterbelt for spatial information technology, but also make the evaluation results for farmland shelterbelt′s effect on crop yield at regional scale more scientific and reasonable, and provide decision making support for the shelterbelt management.

S727.24

国家自然科学基金青年基金项目(31400612,51409204)；陕西省教育厅科学研究计划项目(15JK1473)；西安科技大学博士启动金项目(2014QDJ039)