Although they are important components of forest communities, lianas (woody vines) are often overlooked in ecological studies. While lianas have been shown to damage mature tropical trees and reduce the growth of juvenile trees, the impact of lianas on canopy tree growth in temperate systems is largely unknown. We examined growth of canopy trees over a 9-year period within young forests in the Piedmont region of New Jersey, USA. Trees were grouped into early and late successional categories based on their presence in the canopy of an adjacent old growth forest. Five lianas, Celastrus orbiculatus, Lonicera japonica, Parthenocissus quinquefolia, Toxicodendron radicans and Vitis spp., occurred throughout the forest. Total liana basal area and percent cover within host tree canopies were evaluated to assess liana burdens. These data were related to tree growth to assess liana impacts.
Results/Conclusions
In general, lianas in this system were fairly abundant, with 68% of the trees having at least one liana species present. On average, each tree had 9.7 cm2 of liana basal area associated with the trunk and 23% of the canopy covered with lianas. Trees with > 50% of the canopy covered with lianas grew significantly slower than trees with < 50% or no lianas present. Liana basal area and stem count were not related to reductions in tree growth. Although the association between liana canopy cover and tree growth was statistically significant, our results indicate that lianas within the BSS had a minimal impact on tree growth as liana burden explained very little of the variation in tree growth. Liana densities at the site (4,893 liana stems/ha and 10,725 cm2/ha) were similar to other temperate, deciduous studies. At similar latitudes, lianas have been found to be problematic to forest regeneration at densities of 15,000 cm2/ha. Perhaps liana density at the site was not sufficient to alter forest regeneration. However, some liana species, C. orbiculatus and Vitis spp., are still increasing at the site and may pose future risks to forest growth and development.
