云南松树冠受害表征与有害生物复合危害的关系

The relationship between degrees of Pinus yunnanensis canopy dieback and the types of damage caused by specific pests

【目的】云南松Pinus yunnanensis Franch是我国西南地区重要的生态林造林树种之一。钻蛀性害虫松墨天牛Monochamus alternatus Hope、几种切梢小蠹Tomicus spp.、微红梢斑螟Dioryctria rubella Hampson和一种病害松针褐斑病Lecanosticta acicola能在云南松人工林内严重发生,对森林健康构成威胁。本研究选取树冠枯梢率作为云南松树势的评价标准,筛选出引起树冠枯梢的主要因子,建立云南松树冠受害表征与不同种类(数量)有害生物复合危害之间的关系,以期探索对云南松有害生物进行遥感监测预警的精准判别方法。【方法】设置标准地,抽样选择35株受害状为局部枝梢枯萎和29株系统性萎蔫的云南松,分别调查其上有害生物的种类和数量。使用Pearson相关性分析等方法研究云南松枯梢率与各致害因子(松墨天牛、切梢小蠹、微红梢斑螟和松针褐斑病)之间的关系。通过多元线性逐步回归的方法,筛选出导致云南松树冠局部枯梢的主要因子,建立枯梢率关于主要有害生物种群数量的反演模型。【结果】局部枝梢枯萎植株的树冠枯梢率与两种切梢小蠹的种群数量均呈高度正相关,与树木胸径和其他致害因子呈较弱或无相关性。分析标准地每木调查结果发现,树冠有无病梢不能显著影响枯梢率情况。建立了通过枯梢率(Y)反演云南松树冠两种切梢小蠹混合种群数量(X)的回归模型:Y=12.0984+0.9835 X,Adj-R2=0.8081。明确了在蛀梢阶段,云南松树势随着切梢小蠹种群数量上升而下降。在蛀干阶段,切梢小蠹和松墨天牛的钻蛀活动主要集中在濒死木和枯立木上。【结论】引起树冠局部枯梢、树势下降的主要因子为横坑切梢小蠹和云南切梢小蠹成虫的蛀梢活动;引起树冠系统性萎蔫、树木死亡的主要原因是松墨天牛与切梢小蠹的蛀干活动。应用本研究模型可通过判别云南松树冠枯梢率估算两种切梢小蠹在蛀梢期的混合种群数量,为航天遥感或无人机监测虫情提供可靠的理论基础。

[Objectives] Pinus yunnanensis Franch is an important tree species in plantation forests in southwestern China. Recently, outbreaks of wood boring pests such as Monochamus alternatus Hope, Tomicus spp., Dioryctria rubella Hampson and brown-spot needle blight have been found in P. yunnanensis plantations, threatening local forest health. This study used the dieback rate of the tree canopy as an indicator of tree condition and identified the main factors that cause canopy dieback. A mathematical relationship between the degree of canopy damage and the species and abundance of pest insects was developed to improve the precision of pest monitoring methods and provide accurate early warning of pest infestation in P. yunnanensis plantations. [Methods] In the sample areas, 35 P. yunnanensis with partly withered canopies and 29 completely withered trees were investigated. Species and amounts of different pests in the canopies and trunks of these trees were identified and counted. The correlation between dieback rate and damage factors was analyzed using Pearson correlation coefficients. A multiple linear stepwise regression was used to identify the main factors causing canopy dieback and model the major pest populations based on canopy dieback. [Results] A highly positive relationship between dieback rate and Tomicus spp. abundance was found, whereas a weak, or no, relationship was found between dieback rate and diameter at breast height, shoot disease rate and other factors. A chi-square test showed that shoot disease didn’t influence shoot dieback significantly. We developed a regression model to estimate the population abundance of Tomicus spp. from dieback rate： Y=12.0984＋0.9835 X, Adj-R2=0.8081. This indicated that tree vigor declined as Tomicus spp. abundance increased during the shoot feeding phase. Tomicus spp. and M. alternatus mainly damaged trunks of dying and withered trees during the trunk colonization phase. [Conclusion] The shoot feeding behavior of Tomicus spp. causes partial withering of the canopy and a decline in the vigor of P. yunnanensis, whereas complete withering of the canopy and death follows colonization of the trunk by M. alternatus and Tomicus spp. The dieback model developed in this study can help estimate the mixed population of Tomicus spp. in canopies during the shoot feeding phase and provide a reliable theoretical foundation for pest space remote sensing or unmanned aerial vehicle monitoring.