农田防护林林网结构动态变化遥感评价

Evaluation of the dynamics of farmland shelterbelt network structure based on remote sensing

农田防护林是三北防护林工程中一种重要的防护林类别,及时准确掌握其林网结构的动态变化对了解防护林工程的建设状况和防护林防护效应的发挥至关重要。本研究在原有的景观指数基础上,针对农田防护林特征结合遥感影像数据特点对部分景观指数(带斑比、优势度)进行了修正,对实际与理想状况下防护林景观指数的差异进行了计算,实现了农田防护林林网结构时空动态变化的评价。选择长春市北部防护林建设典型区对该评价方法进行了应用。结果表明:修正后的景观指数计算更简易且适用于中低分辨率遥感数据的评估;通过分割研究区并且计算实际与理想状况下防护林景观指数的差异,一定程度上可以弥补宏观评价的不足,且能够从防护林数量、成型状况及分布状况3个方面对农田防护林林网结构的时空动态变化进行有效评价;所选典型区1985—2020年防护林林网结构总体上趋于优化,但闭合成型林网较少,环度分级为优的林网仅占14%左右。本研究为使用遥感手段评价防护林林网结构动态变化提供了新的思路,评价结果也能够为区域尺度上农田防护林林网的可持续经营提供参考依据。

Farmland shelterbelts are an important part of the Three-North Shelterbelt Project.Detecting changes in the network structure of farmland shelterbelts is crucial for assessing the project’s construction and shelter effects.We proposed revised landscape index that considered the characteristics of farmland shelterbelts and remote sensing data to analyze the spatiotemporal variations in their network structure.Our evaluation method was applied to a typi-cal area of shelterbelt construction in the north of Changchun.The results showed that the revised landscape index calculation was simpler and more suitable for medium and low-resolution remote sensing data.By dividing the research area and calculating the difference in landscape index between real and ideal conditions,the spatiotempo-ral variations in the farmland shelterbelt network structure could be effectively evaluated from three aspects,inclu-ding the number of shelterbelts,their development status,and distribution.From 1985 to 2020,the structure of the shelterbelt network in the selected areas tended to be optimized,although closed-formed shelterbelt networks were less frequent and only about 14%of the shelterbelt networks graded as excellent in circularity degree.Our method provides a novel approach for evaluating the dynamics of shelterbelt network structure and can serve as a reference for the sustainable management of shelterbelts at the regional scale.