昆嵛山腮扁叶蜂取食对赤松生长的影响

依托昆嵛山森林生态定位观察站40块永久性样地,以昆嵛山腮扁叶蜂虫口密度代表为害程度,比较不同样地赤松2006—2008年的平均胸径生长量的差异,并比较了赤松枝条受到连年连续取食或分年度取食后的生长差异,从中评判昆嵛山腮扁叶蜂为害对赤松林分的局部与整体的影响。结果表明:遭受连年取食和分年度取食后的赤松,当年生枝条长度差异显著;同时,生长率差异也显著。根据赤松枝条在3 a受到的为害情况看,赤松枝条当年的生长不受当年昆嵛山腮扁叶蜂取食的影响,但受前一年取食影响:即当前一年虫口密度较大时,赤松当年生枝条的生长受到一定的抑制,反之则影响不大。腮扁叶蜂连续在前年和去年为害2年,会严重降低赤松当年生枝条生长量。通过比较2006年至2008年37块样地赤松胸径的增长量,赤松胸径在不同虫口密度为害下,增长量没有显著差异。这说明昆嵛山腮扁叶蜂为害对树木生长的影响是局部而非整体,在短期内仅从赤松枝条的生长上难以评判其对林分生长的影响。

Imapct of Kunyushan Web-spinning Sawfly Feeding on Growth of Japanese Red Pine

Forty permanent plots were selected at Kunyushan Forest Ecological Positioning Station,and taking the population density of Kunyushan web-spinning sawfly(Cephalcia kunyushanica) to represent the damage level of insect pest,the differences in mean DBH increment of Japanese red pine(Pinus densiflora) trees during the period of 2006—2008 on various plots and the growth difference of P.densiflora trees suffered from continuous feeding or intermittent feeding were analyzed and compared.Based on the results,the local and overall impact of C.kunyushanica’s attack on P.densiflora stands were evaluated.The results showed that after continuous or intermittent feeding,there were significant differences in shoot length,and the difference in growth rate was also very significant.It was found that the growth of current year shoot was not affected by current year feeding while was affected by last year’s feeding.Current year shoot suffered significant length reduction when it had previously experienced high intensities of two successive attacks last year and the year before last.However,the DBH increment in various stands suffered from different sawfly populations showed no significant difference.This indicated that infestations of sawfly may have obvious impact on shoot growth in a short term while it might have little affection on persistence of whole pine stands.Thus,it is difficult to judge the affection of sawfly infestation on pine stands only by pine shoot growth in a short time.