落叶松毛虫发生的空间分布及其影响因子

Spatial distribution of larch caterpillar and its driving factors

落叶松毛虫是大兴安岭林区的主要食叶害虫之一,利用模型模拟其景观尺度的空间分布、揭示其发生机理对落叶松毛虫灾害的预防和治理具有重要意义。本研究基于黑龙江省大兴安岭林区下辖3个林业局2008—2012年落叶松毛虫发生数据(小班水平),应用广义线性模型和最大熵模型预测了落叶松毛虫在立地条件、林分结构等环境变量共同作用下的空间分布,对比分析了环境变量的相对重要性,量化了落叶松毛虫发生概率对环境变量的响应规律。结果表明:广义线性模型与最大熵模型均取得了较好的预测结果,两种模型预测落叶松毛虫发生概率的空间分布大体一致,但通过设定不同的虫害发生概率阈值,适宜发生面积存在明显差别。海拔、龄组、土壤厚度、落叶松百分比是影响落叶松毛虫分布的重要环境变量。其中,落叶松毛虫发生概率在海拔300 m附近最高;中龄林、幼龄林的发生概率显著高于其他龄组;土壤厚度薄的小班更易爆发成灾;虫害发生概率与落叶松比例存在非线性正相关关系。

Larch caterpillar （Dendrolimus superans Butler） is one of the most common defoliators in the forests of Great Xing＇ an Mountains. Modeling the spatial distribution and elucidating its occurrence mechanisms at landscape scales are of high importance for regional prevention and management of this forest pest. In this research, we analyzed the historical larch caterpillar occur- rence data observed during 2005-2012 at the stand level across three forestry bureaus of Great Xing＇ an Mountains. We used generalized linear model （GLM） and maximum entropy model （MaxEnt） to predict spatial distribution of larch caterpillar under the influences of a suite of en- vironmental variables representing site conditions and forest stand structure. We also assessed the marginal effect and relative importance of those environmental variables. The results showed that both GLM and MaxEnt models produced good predictions. Although the spatial distribution pat- terns of the potential larch caterpillar occurrence probability derived from the two models were similar, there were clear differences in pest-prone areas when setting various probability thresh- olds. Elevation, stand age, soil thickness and larch proportion in a stand were important environ- mental variables in determining larch caterpillar distribution. Our results indicated that the larch caterpillar might have the highest occurrence probability in the area where the elevation was around 300 m and forest was young or in the middle-age group. The occurrence probability tended to be higher in the stands with a thinner soil layer. Larch proportion in a stand exhibited a posi- tive but nonlinear relationship with the pest occurrence probability.