Enzyme activities during litter decomposition of two exotic and two native plant species in hardwood forests of New Jersey

Invasions by exotic plant species can alter ecosystem properties, including important soil functions and characteristics. As a result, decomposition of litter from the exotic, as well as native plants, can also be altered, leading to more profound changes in ecosystem functioning. We present here a study of eight enzyme activities during the decomposition of litter from four plant species, two of which are successful exotic invaders in Northeastern USA deciduous forests. The four studied species are: Japanese barberry (exotic), Japanese stilt grass (exotic), chestnut oak (native) and black birch (native). We measured enzyme activities in the decomposing litter at two locations (exotics infested and native vegetation) in two parks in Northeastern New Jersey. In the first 2 years of decomposition, patterns of enzyme activites changed significantly among the four types of litter, however, they were not affected by the location (exotic/native) where decomposition was taking place. Our results clearly show that litter chemistry and site characteristics are strong determinants of enzyme activity in decomposing litter. The microbial community in the litter quickly adapted to the differences in litter chemistry, as patterns of enzyme activity in decomposing litter from the two exotic species were virtually indistinguishable between exotic and native locations.