Llewellyn, Anne, Ecology, Susquehanna University, 1858 Weber Way, Selinsgrove, PA, 17870, llewellyna@susqu.edu; Wilson, Matthew, Freshwater Research Institute , Susquehanna University, 1858 Weber Way, Selinsgrove, PA, 17870, wilsonmatt@susqu.edu.
The leaf litter decomposition in streams is an important stream ecosystem process. The fallen leaves support the stream food web providing nutrients for microbes and macroinvertebrates as well as shelter. Invasive species are known to easily overtake riparian habitats, due to frequent disturbance making these areas vulnerable. Invasive species can simplify the food web, change available nutrients, and reduce biodiversity. Japanese knotweed (Reynoutria japonica) is an invasive perennial that invades wetlands, riverbanks, and roads. Spotted jewelweed (Impatiens capensis) is a native annual that has fragile watery stems, favoring shady moist areas of wetlands and riparian areas. We chose these species for this study because of the frequency at which knotweed invades and replaces jewelweed along streams, making it important to understand how their decomposition rates compare. During decomposition both microbes and macroinvertebrates play a role; microbes biodegrade while macroinvertebrates shred. These differences affect the speed at which the leaves break down and food availability across trophic levels. The goal of this experiment is to measure the decomposition rates of spotted jewelweed and Japanese knotweed when placed in different size mesh packs, to include or exclude macroinvertebrate shredders. These packs were placed in three sites in an unnamed tributary to Chillisquaque Creek at the Bucknell Natural Area in Milton, Pennsylvania. To determine the decomposition rates of the leaf litter, leaves are removed from the packs, and we take a dry mass and ash-free dry mass of each sample. After one week, it was clear jewelweed decomposes faster overall then knotweed with an average of 48.7% mass loss of jewelweed while knotweed lost 25.0% of its mass. Additionally, litter in coarse mesh decomposed twice as fast as in fine mesh across species. By looking at the decomposition rates between a native annual and a non-native perennial we can understand how invasion by knotweed may alter microbial breakdown and macroinvertebrate shredding of leaf litter in streams.
Spotted jewelweed, Japanese knotweed, Decomposition, Leaf Litter