湖北宜昌松林景观格局对松材线虫流行及扩散的影响

The relationship between pine forest landscape patterns and pine wilt disease in Yichang,Hubei Province

景观格局对能量流、物质流和物种流等生态学过程影响显著。为了探究区域生境差异对病虫害发生及扩散的影响,以湖北省宜昌市夷陵区松材线虫病为对象,结合区域森林资源二类清查矢量数据和松材线虫病普查资料,运用景观生态学的原理和方法,探究景观格局对松材线虫病发生的影响。研究结果表明:1)松林景观类型百分比、平均斑块面积、自然连接度和聚合度与松材线虫病的发病率成正相关;2)松林斑块的粒级结构分析表明,中、小斑块能抑制松材线虫病的发生,巨斑块、超大斑块对松材线虫的发生有利;3)从景观干扰上分析显示人类活动强度与松材线虫病发病率成正相关;4)在景观尺度水平上,景观的破碎度大、多样性指数高、蔓延度指数小、斑块形状简单、受人类活动影响大的乡镇松材线虫病发病率高。通过斑块类型尺度和景观尺度两个水平上的分析可知,在夷陵区乡镇尺度上,由小斑块松林组成且斑块聚集度低、景观破碎化程度低的景观格局对松材线虫病有一定的抑制作用。研究结论对当地松材线虫病的防治就有较好的参考价值。

Landscape patterns have significant and complex effects on a variety of ecological processes, including the flow of matter and nutrients and the distribution and movement of species. To explore the impacts of regional habitat differences on the occurrence and spread of forest diseases and insect pests, we focused on the pine wood nematode in Yichang in the Yiling district of Hubei Province. Using forest inventory vector data collected by the Forestry Survey and Planning Institute of Hubei and census data of pine wilt disease in the Yiling district from 2007 to 2012, collected by the Station of Pest and Disease Control and Quarantine, we examined the effects of forest landscape patterns on pine wilt disease, as predicted by landscape ecology theory. Seven towns continuously infected with pine wilt disease from 2007 to 2012 were selected as the research area. The landscape of the Yiling district were classified into 10 types by ArcGisl0 according to the intensity of human activities, the land use classification, and the dominant tree species group. To characterize the research area at the level of patches within a class, we calculated the landscape patch area, mean patch area, percentage of landscape patch area, patch cohesion index, aggregation index, geometric mean nearest neighbor distance, and the interspersionjuxtaposition index. And the pine forest landscape were classified into 5 grades by patches＇ area size （Apatch ）： the small patch （A patch 〈 10 hm2 ）, the middle patch （ 10 ≤ A patch 〈 50 hm2 ） , the large patch （ 50 ≤ A patch 〈 100 hm2 ）, the super patch （ 100 ≤Apatch〈200 hm2）, the huge patch（Apatch ≥200 hm2）. At the landscape level, we calculated the edge density, Shannon＇s diversity index, the contagion index, and the area-weighted mean patch fractal dimension. Landscape pattern indices were calculated using FRAGSTATS3.4. Morbidity was determined as the ratio of the annual average area infected with pine wilt disease compared with the total pine forest area of any one town. Correlation analysis between landscape pattern indices and morbidity was performed using SPSS18 software. The main results were as follows： 1 ） The percentage of pine forest landscape patch area, the average patch size, and the degree of natural connection and polymerization of patches were all positively correlated with pine wilt disease morbidity ; 2） Analysis of the granularity of the pine forest landscape showed that the proportion of area composed of small- and middle-patch sizes was negatively correlated with pine wilt disease morbidity, while the proportion of huge-patch and super-patch sizes was positively correlated; 3 ） The intensity of human activity, which can interfere with the landscape, was also positively correlated with pine wilt disease morbidity; and 4） At the landscape level, as edge density and Shannon＇s diversity index increased, pine wilt disease morbidity increased. The contagion index, in contrast, was negatively correlated with pine wilt disease morbidity, as was the area-weighted mean patch fractal dimension. These results suggest that fragmentation of the entire landscape will facilitate the spread of pine wilt disease. Thus, using the analysis of landscape patterns at the patch and landscape level, we can infer that, in the Yiling district, a forest landscape composed of small pine forest patches with a low aggregation index and low degree of fragmentation of the entire landscape can somewhat prevent the spread of pine wilt disease. The findings of this study can be used as a guide to aid the prevention and control of pine wilt disease in the Yiling district.