Leaf and root decomposition of native and non-native woody species in temperate deciduous forests
Litter decomposition plays an important role in nutrient cycling in forest ecosystems. Previous studies found that invasive species had greater rates of production and produced more labile litter than natives. The increased litter quantity and quality of the invaders should increase nutrient cycling through faster litter decomposition. However, litter decomposition rates for most invasive species are not well understood and the limited number of species that have been included in decomposition studies has hindered the ability to generalize litter decomposition patterns of invaders. Further, most past decomposition studies ignored root decomposition. The goal of this study was to examine litter decomposition rates of a large number of invasive and native shrub and tree species in Eastern U.S. forests. We measured leaf decomposition for 42 native and 36 non-native species, and root decomposition for 23 native and 25 non-native species. We tested if leaf and root decomposition differed between native and invasive species and which litter traits were the best predictors of decomposition rate.
Some non-naive species had exceptionally high leaf decomposition rates than all other (native and non-native) species, but there were no significant overall difference in leaf and root decomposition rates between native and non-native species. For leaves, non-native species had greater leaf N and lower specific leaf area than native species, but nativity was not significantly associated with leaf C, lignin, or water and ethanol extractives (WEE). Among the leaf litter traits, only chemical traits significantly affected leaf decomposition rates. Leaf N and WEE increased leaf decomposition rates and leaf C decreased the rates. Nativity had no effect on root chemical traits. However, non-natives had lower root tissue density and root dry matter content than natives. Root decomposition rates were negatively correlated with root C, lignin, and specific root length, and positively correlated with WEE. Our results suggest that the effects of decomposing litter of invasive species on nutrient cycling in Eastern U.S. forests are species specific.