Abstract Population densities of the green spruce aphid Elatobium abietinum (Walker) (Homoptera: Aphididae) were assessed by direct counting and trapping in 24 Sitka spruce stands that were being managed either by clear-felling and replanting, or by selective thinning under a shelterwood or group selection silvicultural system. It was expected that E. abietinum populations would be lower in shelterwood and group selection spruce stands, because of their greater structural diversity, but instead, maximum E. abietinum densities in the shelterwood and group selection stands were intermediate or higher than the maximum densities recorded in the even-aged spruce stands created by clear-felling. Variation in aphid densities between stands was more closely correlated with stand age and the mean DBH of the largest trees in the stand, and (negatively) with tree density (trees ha−1). The highest mean E. abietinum densities (9.9–14.9 aphids.100 needles−1) were recorded in even-aged stands that were approaching commercial maturity, and on the main crop trees and very young naturally regenerating trees in shelterwood stands. The results of the study indicate that if E. abietinum populations in the U.K. increase in the future in response to climate change, as is predicted, then the most severe impacts of aphid infestation will be seen first in the oldest even-aged Sitka spruce stands, and in shelterwood stands where large spruce trees have been retained beyond the normal rotation age.

中文翻译：

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绿云杉蚜虫 Elatobium abietinum (Walker) 种群密度随树龄和林分结构的变化

摘要 绿云杉蚜虫 Elatobium abietinum (Walker)（同翅目：蚜科）的种群密度通过直接计数和诱捕在 24 个锡特卡云杉林中进行评估，这些林分通过清伐和重新种植，或在防护林下或通过选择性间伐进行管理。群选造林系统。由于其结构多样性更大，预计在防护林和群选云杉林分中的 E. abietinum 种群会较低，但相反，在防护林和群选林分中的最大 E. abietinum 密度是中间或高于记录的最大密度在由清伐形成的偶龄云杉林中。林分之间蚜虫密度的变化与林分年龄和林分中最大树木的平均胸径更密切相关，和（负面）树密度（树 ha-1）。最高平均 E. abietinum 密度（9.9-14.9 蚜虫.100 针-1）记录在接近商业成熟的等龄林分中，以及主要作物树木和防护林林分中非常年轻的自然再生树木上。研究结果表明，如果英国的 E. abietinum 种群在未来随着气候变化而增加，正如预测的那样，那么蚜虫侵扰的最严重影响将首先出现在最古老的偶龄云杉林中，以及在超过正常轮伐年龄后仍保留大型云杉的防护林。在主要作物树木和非常年轻的自然再生树木上。研究结果表明，如果英国的 E. abietinum 种群在未来随着气候变化而增加，正如预测的那样，那么蚜虫侵扰的最严重影响将首先出现在最古老的偶龄云杉林中，以及在超过正常轮伐年龄后仍保留大型云杉的防护林。在主要作物树木和非常年轻的自然再生树木上。研究结果表明，如果英国的 E. abietinum 种群在未来随着气候变化而增加，正如预测的那样，那么蚜虫侵扰的最严重影响将首先出现在最古老的偶龄云杉林中，以及在超过正常轮伐年龄后仍保留大型云杉的防护林。