Document: MAR-3-58-14

Differing microbial enzyme and biomass responses to leaf litter of exotic Norway maple and native sugar maple and their effects on litter decay and nutrient release.

CARREIRO, M.M.*, D.A.REPERT and J.REICHERT

Fordham University, Armonk, NY 10504 USA ¹

Abstract:
Exotic plant species may affect decomposition processes in the communities they invade if they are abundant and their leaf litter quality varies substantially from other plants in the system. The objective of this experiment was to determine whether leaf litter of Norway maple (Acer platanoides), an invasive exotic species in many suburban and urban forests in the northeastern USA, differed in its decay, nitrogen (N) and phosphorus (P) dynamics from a native congener, sugar maple (Acer saccharum) with which it coexists. Norway maple (NM) litter contained about the same amount of lignin as sugar maple (SM) litter collected from the same forest (8.1% NM; 9.8% SM), but had greater %N (1.2% vs. 0.8%) and %P (0.071% vs. 0.043%). In a one-year paired-litterbag decay experiment conducted in a suburban oak forest near New York City, we found that NM, with a mean residence time of 230 days, decayed faster than (SM) (0.43% vs. 0.28% per day). At the end of one year NM released more of its original N and P than sugar maple, with NM losing 56% and 42%, and SM losing 24% and 18% of original N and P, respectively. Cumulative microbial enzyme activity patterns showed that microbes reacted to the differences in litter nutrient quality by producing nearly 150% more cellulase on NM than SM during the entire decay period. However, microbes growing on SM produced 65% more phosphatase, as predicted from the lower initial P content of SM. Total ligninase activity for the two litters were very similar. NM supported 50% more cumulative fungal biomass (measured as ergosterol) than SM and, as expected, this was correlated with greater N-acetylglucosaminidase activity in NM. These results suggest that substitution of NM for SM in a forest would result in a shallower litter layer, faster rates of N and P return to soil, and differing microbial growth dynamics that could affect the rest of the decomposer food web.

Keywords: exotic plant species, decomposition, microbial enzymes, N and P mineralization, Norway maple

This abstract is being presented at: 10:30 AM in session:
Poster Session #13: Decomposition and Soil Respiration.