Abstract

Few studies focused on non-outbreaking herbivorous insects to understand the patterns of damage they inflict on plants. We compared damage by herbivorous insects on young white spruce (Picea glauca) between natural regrowth in the understory of mixed wood forest and small extensively-managed plantations. We observed damage to foliage to quantify damage by different groups of herbivores, including leaf chewers, miners and sap-sucking species. Our hypothesis stated that trees in forest understory environments would have higher diversity of damages caused by insects but that plantation trees would have more damaged tree shoots. Our two sampling methods were branch collection, in which we collected a forty-centimeter branch and recorded foliar damage, and field surveys, where one researcher recorded foliar damage on the saplings for three-minute intervals. We also measured tree growth, canopy openness, soil temperature and humidity. We used these environmental variables in general linear models to test their effects on herbivore damage in the two habitats. The results showed that plantation and understory trees did not differ significantly in the overall amount of insect damage. There was no correlation found with any environmental factor. This pattern indicated that the plantation we sampled maintained insect biodiversity similar to that in mixed wood forests. Thus, small, extensively managed multispecies plantations can be less at risk of insect outbreaks.