官司河流域防护林结构调整及景观格局变化

利用2005年度的IKONOS4卫片解译数据、1:1万林相图、2007年度森林资源二类小班调查资料,结合样地调查数据以及四川省林业科学研究院森林生态效益定位站(四川绵阳新桥)径流场的有关数据,对绵阳官司河流域的防护林结构进行了调整,并对调整前后的生态经济效益和景观格局的变化进行了对比分析.结果表明:目前本区的林地面积分配不合理.针阔混交林面积偏小,仅占整个有林地面积的14.97%,而针针混交林的面积却占了27.37%,针叶纯林的面积更是占了42.48%.从物种多样性、均匀度以及生态优势度综合来看,均表现出混交林优于纯林.经调整后各类防护林面积比例为针阔混交林28.05%、灌木林17.28%、经济林13.27%、阔叶纯林13.13%、针针混交林11.04%、针叶纯林10.89%、草地6.34%.针阔混交林面积明显增加,从原来的124.39 hm2增加到现在的233.13 hm2,增加了87.42%.经济林的面积有所增加,从原来的96.67 hm2增加到调整后的110.30 hm2.本区防护林土地利用的生态效益指数由调整前的2 053.93点上升到调整后的2 327.39点,净增了13.31%,经济效益指数则从调整前的2 300.40点上升到调整后的2 493.63点,净增了8.40%.景观多样性指数(H)和景观均匀度指数(E)分别由调整前的1.826 1和0.523 8增加到调整后的2.192 3和0.768 3,分别增加了20.05%和46.68%.景观优势度和蔓延度指数由调整前的0.734 8和0.732 7减少到调整后的0.381 6和0.692 8.说明景观的异质性提高,向着多样化和均匀化方向发展.调整后各景观要素的边缘密度和斑块密度减少,其斑块向小型化发展,景观破碎度增加.调整后各要素的散布与分列指数IJI都有明显的增加,说明其空间关系趋于复杂化.聚集度指数AI增大,其斑块越来越聚集,斑块的结合底在增大.各景观要素的LSI都有不同程度的减少,而分维数都有不同程度的增加,说明其斑块复杂程度减少,稳定性增加.

Structure Regulation of Protection Forest and Changes of Landscape Structure in Guansi River Watershed

By application of interpreted IKONOS4 in 2005, 1∶10 000 forest map, data of Class II forest survey in 2007, as well as runoff data in permanent runoff monitoring field, the structure of protection forest systems in Guangsi river in Mianyang municipality were regulated; besides, the eco-economic benefits and landscape pattern before and after regulation were analyzed.The results indicated that the forest distribution in this area is not rational, the area of mixed forest between coniferous and broad-leafed species is relatively low (14.97%), the area of mixed forest by coniferous species and pure coniferous forest was 27.37% and 42.48% respectively.Judging by biodiversity, evenness and eco-dominance, the mixed forest is much better than that of pure forest.After regulation, the area of mixed coniferous and broad-leafed forest, shrub forest, economic forest, broad-leafed forest, mixed forest by coniferous species, pure coniferous forest and grassland was 28.05%, 17.28%, 13.27%, 13.13%, 11.04%, 10.89% and 6.34% respectively.The area of mixed forest between coniferous and broad-leafed species increases sharply, from 124.39 hm2 to 233.13 hm2 (by 87.42%); the economic forest goes up from 96.67 hm2 to 110.30 hm2.Meanwhile, the ecological benefit index increases from 2 053.93 to 327.39(or by 13.31%), economic benefit index goes up from 2 300.40 to 2 493.63(or by 8.40%).The landscape diversity index (H) and evenness index (E) change from 1.826 1 and 0.523 8 before regulation to 2.192 3 and 0.768 3 (or by 20.05% and 46.68% respectively).After regulation, the index of landscape dominance and contagion decreases from 0.734 8 and 0.732 7 to 0.381 6 and 0.692 8 respectively, this means that the heterogeneity of landscape increases and develops toward diversity and evenness.Besides, the margin density and patch density of landscape elements go down; the patch develops toward small size and the degree of fragmentation increases.Meanwhile, the dispersion and IJI increase obviously, which means the spatial relationship become more complicated.Higher AI means increase of congregation.LSI of landscape elements decrease but fractural dimension goes up to some extent; this indicates that the complex of patches decrease and stability increases.