How Structural Complexity of Vegetation Facilitates Invasion: Integrating LiDAR and FIA Invasive Species Plot Data in the Appalachian Mountains of the USA

This study examines how the vertical structure of forests and the variation in forest canopy tree composition relates to where forest plant invasions occur at a regional scale. We used LiDAR data on vertical structure of forests collected across 16 counties of western North Carolina, and Forest Inventory and Analysis (FIA) abundance data of invasive plant species and canopy tree species from 575 plots. We found that nearly one third of these plots were invaded by at least one invasive plant species (range = 1 to 8 species). We derived canopy gaps/clear-cut areas of the study site using LiDAR data matrix (RH100) and 2006 NLCD image to compare invasive species richness at the vegetation gap and closed canopy areas. The most frequently occurring invasive species of the 22 recorded invasive species in the vegetation gap and closed canopy areas were Lonicera japonica (Japanese honeysuckle; 67% & 49%), Rosa spp. (non-native rose; 58% & 51%) and Ligustrum sinense (Chinese privet; 36% & 25%) respectively. Majority of invasive species in both vegetation gap and closed canopy areas are dispersed by birds/ small mammals. Preliminary results suggest that plots in areas having greater forest structural complexity have less invasive plant species present. A variety of mechanisms can explain how forest structural complexity may impact invasivability. We conclude by summarizing these possible mechanisms and the role that LiDAR can play in studying and managing forested landscapes threatened by invasive species

Biological invasion hotspots: a trait-based perspective reveals new sub-continental patterns

Invader traits (including plant growth form) may play an important, and perhaps overlooked, role in determining macroscale patterns of biological invasions and therefore warrant greater consideration in future investigations aimed at understanding these patterns. To assess this need, we used empirical data from a national-level survey of forest in the contiguous 48 states of the USA to identify geographic hotspots of forest plant invasion for three distinct invasion characteristics: invasive species richness, trait richness (defined as the number of the five following plant growth forms represented by the invasive plants present at a given location: forbs, grasses, shrubs, trees, and vines), and species richness within each growth form. Three key findings emerged. 1) Th e hotspots identified encompassed from 9 to 23% of the total area of our study region, thereby revealing many forests to be not only invaded, but highly invaded. 2) Substantial spatial disagreement among hotspots of invasive species richness, invasive trait richness, and species richness of invasive plants within each growth form revealed many locations to be hotspots for invader traits, or for particular growth forms of invasive plants, rather than for invasive plants in general. 3) Despite eastern forests exhibiting higher levels of plant invasion than western forests, species richness for invasive forbs and grasses in the west were respectively greater than and equivalent to levels found in the east. Contrasting patterns between eastern and western forests in the number of invasive species detected for each growth form combined with the spatial disagreement found among hotspot types suggests trait-based variability in invasion drivers. Our findings reveal invader traits to be an important contributor to macroscale invasion patterns

Invasive Species Terminology: Standardizing for Stakeholder Education

The excessive number of terms associated with invasive species, and their often incorrect usage, hinders stakeholder education about the threats of invasive species. Here we introduce seven terms (native, nonnative, introduced, established, invasive, nuisance, and range change) that are applicable across invasive taxa, understandable, typically interpreted correctly, and useful for describing most situations regarding invasive species. We also list six terms to avoid (native invasive, invasive exotic, invasive weed, alien, foreign, and nonindigenous) that create confusion via their misuse and misinterpretation. The terms we propose will increase understanding, thereby promoting behavior changes aimed at limiting the negative impacts of invasive species

Identifying invasive species threats, pathways, and impacts to improve biosecurity

Managing invasive species with prevention and early-detection strategies can avert severe ecological and economic impacts. Horizon scanning, an evidence-based process combining risk screening and consensus building to identify threats, has become a valuable tool for prioritizing invasive species management and prevention. We assembled a working group of experts from academic, government, and nonprofit agencies and organizations, and conducted a multi-taxa horizon scan for Florida, USA, the first of its kind in North America. Our primary objectives were to identify high-risk species and their introduction pathways, to detail the magnitude and mechanism of potential impacts, and, more broadly, to demonstrate the utility of horizon scanning. As a means to facilitate future horizon scans, we document the process used to generate the list of taxa for screening. We evaluated 460 taxa for their potential to arrive, establish, and cause negative ecological and socioeconomic impacts, and identified 40 potential invaders, including alewife, zebra mussel, crab-eating macaque, and red swamp crayfish. Vertebrates and aquatic invertebrates posed the greatest invasion threat, over half of the high-risk taxa were omnivores, and there was high confidence in the scoring of high-risk taxa. Common arrival pathways were ballast water, biofouling of vessels, and escape from the pet/aquarium/horticulture trade. Competition, predation, and damage to agriculture/forestry/aquaculture were common impact mechanisms. We recommend full risk analysis for the high-risk taxa; increased surveillance at Florida's ports, state borders, and high-risk pathways; and periodic review and revision of the list. Few horizon scans detail the comprehensive methodology (including list-building), certainty estimates for all scoring categories and the final score, detailed pathways, and the magnitude and mechanism of impact. Providing this information can further inform prevention efforts and can be efficiently replicated in other regions. Moreover, harmonizing methodology can facilitate data sharing and enhance interpretation of results for stakeholders and the general public.</p

Global data on earthworm abundance, biomass, diversity and corresponding environmental properties

Publisher Copyright: © 2021, The Author(s).Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change.Peer reviewe

Global data on earthworm abundance, biomass, diversity and corresponding environmental properties

Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change

Utilizing Multiple Approaches to Understand the Ecology of Rhamnus cathartica L. Invasion and Management

Exotic shrubs are becoming an increasingly dominant component of plant communities throughout the temperate regions of North America; and thus a concern for management. I studied these invasions and their management using three different investigative approaches. In Chapter 1, I used a landscape-scale natural experiment in conjunction with statistical modeling to determine if the belowground differences between woodlands with and without the exotic shrub Rhamnus cathartica (European buckthorn; hereafter buckthorn) reflect pre-invaded conditions or buckthorn-induced changes. I found that the higher levels of soil moisture, pH, total C, total N, NH4+-N, and Ca2+ observed in buckthorn-invaded woodlands pre-date and likely promote buckthorn invasion. I also found that buckthorn invades areas with higher rates of leaf-litter decomposition, but buckthorn then further accelerates decomposition and causes spring NO3--N to initially increase and then later decrease as invasions progress. In Chapter 2, I used a manipulative field experiment to determine if amending soils with buckthorn mulch can limit buckthorn reinvasion. I found that the mechanical disturbance of tilling mulch into the soil, and not the actual mulch, greatly reduced reinvasion by killing small buckthorn individuals that were overlooked during initial removal. I also found that recruitment of new buckthorn individuals rapidly declined overtime, suggesting that buckthorn seeds are short-lived. Therefore, repeated annual follow-up control of overlooked and newly recruiting buckthorn individuals may deplete buckthorn’s remnant seedbank, causing more prolonged reductions in reinvasion than what are typically observed. In Chapter 3, I used an individual-based model to investigate invasions by exotic shrubs into light-limited woodlands. I found that rates of spread were highly sensitive to moderate variation in reproductive age and fecundity, and that canopy gaps facilitate spread by affecting these life-history traits, but not by affecting dispersal. The changes in reproductive age and fecundity that increased rates of spread produced non-parallel changes in the following invasion characteristics: the proportion of invasions reproducing, degree of clumping, and invasional lag. Model outcomes were consistent regardless of where invasions started. From these model outcomes, I determined empirical investigations that will likely improve our understanding of exotic-shrub invasions, and management strategies that may limit their spread

Wet Meadow Revegetation Following Invasive Plant Control

Phalaris arundinacea invades sedge meadow restorations, forming persistent monotypes that prevent community establishment. Eradicating Phalaris, however, leaves restored ecosystems prone to reinvasion. In order to restore desired plant communities, methods to control Phalaris are needed. To determine if reducing light by sowing cover crops and reducing nitrogen by incorporating soil-sawdust amendments would prevent Phalaris invasions, a study was conducted under conditions similar to a restored wetland in two experimental basins with controlled hydrology. Seeds of a 10-species target community and Phalaris were sown in plots with high diversity, low diversity, or no cover crops in soils with or without sawdust amendments. Nitrogen, light, tissue C:N ratios, firstyear seedling emergence, establishment, and growth, and second-year above ground biomass were measured. Only high diversity cover crops reduced light and sawdust reduced nitrogen for about 9 weeks. Similar trends in firstyear seedling data and second-year biomass data suggested Phalaris control efforts should focus on establishing perennial communities rather than implementing separate resource-limiting strategies. Sowing high diversity cover crops resulted in Phalaris-dominated communities, making cover crops an ineffective Phalaris control strategy. Using sawdust amendments did not reduce Phalaris invasion much beyond what the target community did but resulted in a community similar to those of natural sedge meadows by increasing the abundance of seeded species from the Cyperaceae family and colonization of non-seeded wetland species. The target community apparently reduced Phalaris invasion by reducing both light and nitrogen. Regardless, no treatment fully prevented invasion, making follow-up Phalaris control necessary to ensure community recovery.Minnesota Department of TransportationIannone III, Basil V.; Galatowitsch, Susan M.. (2008). Wet Meadow Revegetation Following Invasive Plant Control. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/151676