Friday, August 10, 2007
Exhibit Halls 1 and 2, San Jose McEnery Convention Center
Much evidence indicates that Amur honeysuckle (Lonicera maackii), an invasive Asian shrub, reduces the abundance, diversity, growth, and reproduction of native plants in eastern deciduous forests. There is no information, however, on whether it affects soil communities. For example, altered microhabitat under honeysuckle canopies could alter soil microbial activity, litter decomposition and ultimately nutrient turn over. We determined whether honeysuckle leaves altered soil microbial activity and measured the effects of honeysuckle on decomposition of native leaves in a southwestern Ohio forest. To estimate microbial activity, potted field soil was maintained in a greenhouse and covered with either Amur honeysuckle or sugar maple leaves. Every two weeks for 5 months, Triphenyltetrazolium chloride (TTC) reduction was performed on samples of the potted soil. To quantify litter decomposition, leaf mass loss was measured monthly from litter decomposition bags filled with a mixture of sugar maple (Acer saccharum) and chinquapin oak (Quercus muehlenbergii) and placed in forest plots invaded by honeysuckle, in plots with honeysuckle removed, and in non-invaded plots. Over 20 weeks, soil from pots containing honeysuckle leaves had higher microbial activity than pots containing maple leaves, and there was a significant interaction between leaf type and sampling period. We attribute this to the relatively fast decomposition of honeysuckle leaves in the greenhouse (8 weeks) compared to native leaves (> 20 weeks). Honeysuckle had no effect, however, on mass loss in litter decomposition bags in the field, despite a significant interaction of honeysuckle and month. This interaction could be due to seasonal variations in litter depth and temperature under honeysuckle shrubs. These data suggest land managers should focus not only on direct effects of invasive species on native populations, but should also consider indirect effects caused by alteration of the leaf litter and soil microbial community.
