Jc. Su et Sa. Woods, Importance of sampling along a vertical gradient to compare the insect fauna in managed forests, ENV ENTOMOL, 30(2), 2001, pp. 400-408
Unbiased samples from insect traps are dependent on the placement of traps
to account for variation in the spatial distribution of insect fauna. In fo
rests, the spatial distribution of insects reflects forest vertical structu
re. However, comparative studies of insect diversity in managed forests hav
e traditionally focused a single forest stratum (e.g., forest floor, canopy
). We evaluated the importance of sampling along a vertical gradient to ass
ess the effects of silvicultural treatments on insect fauna. We compared th
e catch from flight-intercept traps suspended at 1, 3, 5, 7, 9, and 11 m ab
ove the forest floor in eight forest stands representing three management t
ypes: two clearcut stands, two shelterwood stands, and four selection stand
s. The vertical distribution of insects was significantly different across
the three management systems, A greater proportion of the insect fauna was
recovered close to the forest floor in clearcut stands than in selection an
d shelterwood stands. Some insect taxa were restricted to the higher traps;
whereas other taxa showed different height associations across the three m
anagement systems. Therefore, vertical sampling is important to compare the
insect fauna in managed forests differing in vertical structure.