Folivory of vine maple in an old-growth Douglas-fir-western hemlock forest
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Folivory of vine maple (Acer circinatum) was documented in an old-growth Douglas-fir-western hemlock (Pseudotsuga menziesii-Tsuga heterophylla) forest in southwest Washington, USA. Leaf consumption by lepidopteran larvae was estimated with a sample of 450 tagged leaves visited weekly from 7 May to 11 October 1999, the period from bud break to leaf drop. Lepidopteran taxa were identified by handpicking larvae from additional shrubs and rearing to adult. Weekly folivory peaked in May at 1.2%, after which it was 0.2% to 0.7% through mid October. Cumulative seasonal herbivory was 9.9% of leaf area. The lepidopteran folivore guild consisted of at least 22 taxa. Nearly all individuals were represented by eight taxa in the Geometridae, Tortricidae, and Gelechiidae. Few herbivores from other insect orders were observed, suggesting that the folivore guild of vine maple is dominated by these polyphagous lepidopterans. Vine maple folivory was a significant component of stand folivory, comparable to ~66% of the folivory of the three main overstorey conifers. Because vine maple is a regionally widespread, often dominant understorey shrub, it may be a significant influence on forest lepidopteran communities and leaf-based food webs.