混交林不同配比结构对落叶松毛虫发生与传播的影响

Effects of different ratio structures of mixed forests on the occurrence number,probability and distri⁃bution of Dendrolimus superans Butler

[目的]落叶松毛虫(Dendrolimus superans Butler)是危害我国北方地区针叶树种的主要虫害,明晰其发生规律和影响因素对提升森林稳定性和森林质量有重要意义。[方法]本研究以华北落叶松纯林和华北落叶松-云杉混交林为研究对象,采用点格局和相关性分析的方法,分析了虫害的空间分布格局以及影响其发生和传播的主要因素。[结果]华北落叶松纯林虫害发生最严重,单株林木感染松毛虫的数量接近10头·株^(-1),林木发病率达到33%;混交配比为3∶5的混交林中,单株林木感染松毛虫的数量低于3头·株^(-1),林木发病率低于15%,其余混交配比的林分中,单株林木感染松毛虫的数量至少达到6头·株^(-1),林木发病率均高于20%。落叶松松毛虫的空间分布格局在小尺度范围内属于聚集分布,随着尺度的增加,逐渐转变为随机分布。华北落叶松纯林中林木大小(胸径和树高)与单木感染落叶松毛虫的数量呈显著的负相关关系,在混交林中林木大小与松毛虫的发生无明显关系。林分密度是影响落叶松毛虫发生及传播的重要林分因子,二者的相关系数达到0.9以上。[结论]营造混交林可以一定程度上降低松毛虫的发生数量和概率,抑制其传播效率,但不同混交配比产生的效果存在差异,本研究中华北落叶松-云杉混交林以3∶5的混交结构对虫害的防治效果最好。

[Objective]Dendrolimus superans Butler is a major pest of coniferous trees in northern China.Clarifying its occurrence pattern and influencing factors is of significance to improve forest stability and forest quality.[Methods]In this study,the spatial distribution pattern of D.superans and the major effective indicators in pure larch forest and mixed forest of Larix principis-rupprechtii with Picea asperata were analyzed based on point pattern analysis and correlation analysis.[Results]The damage of D.superans was the most serious in the pure larch forest with the number of 10 per tree and the proportion of infected trees was 33%.When the mixed ratio was 3∶5,the number of D.superans per tree was less than 3 and the proportion of infected trees was less than 15%.But in other mixed forests,the number of D.superans per tree was at least 6 and the incidence of infected trees was more than 20%.The spatial distribution pattern of D.superans gradually changed from aggregation type to random type with the increase of spatial scale.In the pure forest,the significantly negative correlation was observed between tree size(diameter at breast height,tree height)and the number of D.superans per tree,but there was no significant relationship between the two factors in mixed forests.Stand density was the most important factor that effected the number and transmission of D.superans,and the probability of Dendrolimus punctatus and inhibit its transmission efficiency to a certain extent,but the effects with different mixed ratios were different.[Conclusion]In this study,the mixed ratio of 3∶5 of Larix principisrupprechtii with Picea asperata has the best effect on controlling the occurrence and transmission of Dendrolimus superans.