落叶松叶蜂危害对落叶松生长及发育的影响

The Influence of Larch Sawfly on the Growth and Development of Larix principis-rupprechtii

通过测定火地塘林区人工落叶松针叶日增重，及落叶松叶蜂幼虫的日食量，在建立针对重量生长及幼虫日食量动态模型的基础上，模拟并演示了特定林分中特定种群为害时叶量的损失过程，结果表明，叶量损失率迅速增长的阶段处于幼虫的４～５龄期，即针叶重量生长的稳定期；由此给出了在不同虫龄期能够确定调查林中虫口密度是否达防治标准的叶量损失率指标值。同时还研究了落叶松叶蜂为害后，华北落叶松枝条生长量及材积生长量的变化规律，结果说明，当叶量损失率达５０％以上时，枝条年生长减少６．１２ｃｍ，胸径生长下降１６．６０％，１９８１～１９９２年４次暴发期共减少材积１８．５０ｍ３／ｈｍ２，平均每暴发期净损失达４．６２５ｍ３／ｈｍ２，严重年份损失高达６ｍ３／ｈｍ２。

Revealed the losing process of leaf-quantity in the larch sawfly outbreaking,based on the measurement of leaf increment and larvae diet-quantity in a specific larch forest stand and larvae population. The result shows that the phase in which the lossing rate of the larch leaves increases rapidly is in the period when larvae are at 4-5 instar. The control threshold of leaf lossing rate at different instar larvae was also established. At the same time, studied and discussed the dynamic-rules of branch growth and timber accumulation of the larch, after damaged by larch sawfly. As a result, when the lossing rate of the larch leaves is over 50%,the branchlength reduced 6.12cm and 16. 6% for bosom-across. The total timber accumulation reduced 18.50m3/ha at four periods of autbreak during 1981-1992, and average net loss is about 4. 625m3/ha in each period of outbreaking, and the heaviest one is 6m3/ha.