Effects of the invasive vine Vincetoxicum rossicum on ecosystem multi-functionality
Human-caused species invasions are widely recognized as not only having significant economic impacts, but also drastically reducing diversity and altering ecosystem function. An emerging trend in the assessment of ecosystem functionality is the application of multi-functionality indices that integrate the simultaneous production of multiple ecosystem functions and services. Here, we present a synthetic approach that considers the impact of invasion on ecosystem multi-functionality in a semi-natural peri-urban ecosystem. Ontario’s Rouge Park contains variable abundance of Dog-strangling vine (Vincetoxicum rossicum, Apocynaceae), an aggressive plant invader from Eurasia. Variable dominance of V. rossicum results in a diversity gradient throughout the Park with some sites being virtual monocultures, others showing partial invasion, and others as of yet un-invaded. We examined how the relative abundance of V. rossicum affects multiple ecosystem functions and services in meadow communities throughout Rouge Park (biomass production, decomposition rates, nutrient availability, soil carbon, and pollinator diversity). We hypothesize that V. rossicum invasion will cause a significant reduction in ecosystem multi-functionality.
Preliminary analysis shows that V. rossicum abundance has variable influence across the studied ecosystem functions and services. Across 14 study sites, the relative abundance of V. rossicum ranged from 3.8 ±2.1 % to 55.3 ±3.8 %. Biomass production ranged from 310.65 ±27.22 g to 1227.49 ±107.35 g per 1m2 plot but was not significantly related to V. rossicum abundance. We found that the decomposition rate of V. rossicum litter, determined through exponential decay functions, was significantly reduced with increasing V. rossicum abundance (r2=0.45, p <0.01), but the decomposition rate of litter from a native dominant, solidago spp., showed no significant variation. From composite soil samples (to a depth of 10 cm) we found no significant variation in total carbon or nitrogen, but inorganic nitrogen (NO3- + NH3+) was significantly reduced with increasing V. rossicum abundance (r2=0.43, p <0.01). Average pollinator species richness, was reduced with increasing V. rossicum abundance, but only significant at p < 0.1 (r2=0.25). To fully assess the impact of invasion, further analysis will involve the integration of these effects into a multi-functionality index. In the context of species invasion, this will require a novel approach that considers the interaction between multiple ecosystem functions and services.