Invasive Species

Multiple interacting stressors are generating unprecedented challenges to ecosystem resilience, necessitating efforts to understand how ecosystems will respond to concurrent biotic and abiotic changes. To address this need, we examined the effects of Eastern hemlock (Tsuga canadensis) loss due to an exotic insect on nitrogen retention at three elevations (low, mid, high) subject to increasing atmospheric nitrogen deposition in mixed hardwood stands in western North Carolina. We found that nitrogen pools and fluxes varied substantially with elevation: total forest floor and mineral soil nitrogen increased and forest floor and soil carbon to nitrogen ratio decreased with elevation, suggesting that these high elevation pools are accumulating available nitrogen. Contrary to expectations, subsurface leaching of inorganic nitrogen was minimal overall and was not higher in stands with hemlock mortality. Moreover, although nitrogen loss increased with nitrogen availability in reference stands, there was no relationship between nitrogen availability and loss in stands experiencing hemlock decline. Higher foliar nitrogen and observed increases in the growth of hardwood species in high elevation stands suggest that hemlock decline has stimulated nitrogen uptake by healthy vegetation within this mixed forest, and may thereby contribute to decoupling the relationship between nitrogen deposition and ecosystem nitrogen loss.

Invasive plants in New England are mediated by climate and landscape characteristics. Our goal was to assess the change in forest edges in New England, the association of forest edges and invasive plants, and whether socio-economic factors could explain forest edges. We created a thematically consistent land use/land cover time series (1992, 1996, 2001, 2005/6) for New England that was used to classify forests into four forest classes: perforated, patch, edge, and core. Invasive plant distribution data from the Invasive Plant Atlas of New England, physical factors, such as roads and elevation, and socio-economic data from the U.S. Census were used for the analysis. Our analysis shows an increase in forest edges and a decrease in core and total forest in New England from 1992 to 2005/6. Invasive plants were found differentially in forest edges. Bayesian linear regression models demonstrate that physical factors, such as quantity of roads and elevation range, and time-lagged socio-economic factors, such as total population and the number of single family housing units, drive a large fraction of the variation in forest edges. Our socio-ecological approach can help guide early detection and management efforts for invasive plants and highlights the human-environment connection in the region.

As economic pressures on Americans increase, consumers are likely to forego expensive recreational activities, such as boating and fishing, in favor of more essential goods and services. Because aquatic invasive species can be dispersed overland by these human activities, decreases in boating and fishing activity could have profound effects on the spread of invasive species to inland lakes. Using boater registration data, a stochastic multi-step gravity model was constructed to simulate an inland invasion from the Great Lakes to Michigan inland lakes. The stochastic components of the model included the probability of establishment and boater behavior preferences. To demonstrate the effects of various economic states on recreational boating, we altered model parameters such as a boater?s preferred distance of travel, number of trips taken, and propensity to visit multiple lakes in a single trip. Our results show that, as economic factors discourage boating behavior, potential invasions occur less often, at shorter distances, and in a more clustered configuration. Understanding the effects of the economy on recreational behavior can provide insight into how natural resource agencies can prioritize management of lakes dependent on current economic conditions.

The talk will provide an overview of National Ecological Observatory Network (NEON): a NSF funded national investment in physical and information infrastructure. NEON?s goal is to enable understanding and forecasting of the impacts of climate change, land use change and invasive species on continental-scale ecology by providing physical and information infrastructure to support research, education and environmental management in these areas. NEON provides vetted and authoritative data and information to scientists, educators, decision makers and the public on how land use, climate change and invasive species affect biodiversity, disease ecology, and ecosystem processes. NEON high-level data products are designed to enable ecological forecasts and analyses at a continental scale and facilitate the observation of decadal scale changes against a background of seasonal-to-interannual variability. We foresee an ecosystem of government, NGO, and academic data sources that will serve as credible producers of linked data, promote data sharing, and champion responsible data life cycle management. This, together with interoperability initiatives, will open up the marketplace of ideas on ways to synthesize ecological data into meaningful information for societal benefit.

The spread of aquatic invasive species to inland lakes can be facilitated by angler activities associated with bait use and transportation. As such, bait retailer locations could be used to indicate possible risk of infestation to nearby lakes. Other factors, such as lake area and distance to other infested lakes have previously been shown to be important predictors of the presence of invasive species. Thus, in this study, we tested if the presence of bait shops aids in the prediction of the presence of zebra mussels (Dreissena polymorpha) in the inland lakes of Michigan. Using data developed in a GIS we compared various single- and multi-factor models to examine these relationships in Michigan lakes. Our results show that the distance to the nearest bait retailer, in conjunction with boat ramp presence, road network distance to nearest infested lake, and lake surface area are important factors in determining presence of zebra mussels in lakes. Identifying these interactions is important for understanding the distribution of future invasive species, and could have possible practical applications to boater behavior models and natural resource management.

Successful management of biological invasions requires landscape-scale information on the spatial distribution and abundance of the invader. Spectral reflectance properties of high-resolution multi-spectral satellite imagery provide detailed and synoptic perspectives on vegetation composition, but have limited ability to detect the structure and composition of forest understory plant species. To address this, we examine the utility of structural and radiometric indices of forest vegetation ? derived from LiDAR (Light Detection and Ranging) data ? to detect and map the spatial distribution of invasive understory plant species. We map the understory plant Chinese privet (Ligustrum sinense) as a case study of a rapidly spreading exotic species in urbanizing forest landscapes. Our approach uniquely integrates LiDAR-derived indices with field data on forest structure using an ensemble classifier, the Random Forest Algorithm, for detection and mapping of an invasive plant species. We evaluate the hypothesis that the evergreen nature of Chinese privet and its height range from 1 - 5 m provide sufficient structural and radiometric characteristics for LiDAR detection. We discuss the characteristics of Privet (e.g., size and rarity) and presence of other plant species (e.g., confusion with Eastern red cedar) that influence detection and suggest methods for improving invasive species mapping using LiDAR.

To determine if commercial ship ballast water discharge is playing a role in the secondary spread of viral hemorrhagic septicemia virus (VHSV) in the Great Lakes, we developed several competing spatial models. Our null and random shipping models were used to determine if the current pattern of VHSV is related to ballast water discharge locations or if VHSV occurrences are located randomly. A weighted shipping model was built to determine if discharge locations were more likely to be infested if they received more visits from discharging ships. The weighted shipping model was also used to test three different initial infestation scenarios to see if the model could be used to identify the location of first infestation in the Great Lakes. All models included a local spread component, ranging from 10- to 30-km spread per year to represent the spread of the disease via natural vectors. Sensitivity, specificity, and a weighted kappa were calculated to analyze the data. Our results suggest that ballast water discharge has played a role in the spread of VHSV, and that Montreal, as opposed to the initially observed location of Lake St. Clair, was the initial infestation location.

The delimitation of dispersal routes utilized by invasive species has the potential to direct management efforts in invaded systems, and may be used to prevent the invasion of native communities. Landscape genetics provides a powerful tool to determine post-invasion movement corridors by integrating inferences of gene flow between populations with landscape ecological metrics. This technique was used to describe dispersal patterns of invasive red swamp crayfish (Procambarus clarkii) through a spring system in Nevada's Mojave Desert. Ash Meadows National Wildlife Refuge is comprised of thirty springs and seeps that provide habitat for forty endemic species. A combination of anthropogenic habitat degradation and the establishment of invasive species like P. clarkii has caused extinctions, local extirpations, and severe population declines of native and endemic biota in Ash Meadows. Although many Ash Meadows springs are hydrologically isolated, intermittent connectivity occurs during heavy precipitation events, allowing for dispersal of aquatic organisms. Invasion routes of P. clarkii from reservoir populations to distal springs were inferred using microsatellite genotypes and mitochondrial haplotypes combined with GIS models of hydrologic connectivity. These results will direct the placement of barriers to crayfish movement to prevent reinvasion of distal springs after they have been restored.