Kendra Cipollini

Separating above- and belowground effects of Alliaria petiolata and Lonicera maackii on the performance of Impatiens capensis.

ABSTRACT Invasive plants can exert their effects on native plants through both above- and belowground mechanisms. In a fully factorial field study, we examined the effects of activated carbon addition and removal of aboveground biomass (i.e., cutting) on the survival, growth and reproduction of transplanted Impatiens capensis seedlings in habitats dominated by either Lonicera maackii (honeysuckle) or Alliaria petiolata (garlic mustard). Activated carbon can adsorb organic molecules, including potential allelochemicals. Cutting of A. petiolata increased survival and fruit production of I. capensis, while cutting of L. maackii increased survival and tended to increase fruit production. Carbon application tended to increase survival of I. capensis in A. petiolata-dominated plots, but had no effect in L. maackii-dominated plots. The effects of carbon application on growth and fruit production of I. capensis depended upon the cutting treatment in A. petiolata – dominated plots. In plots where A. petiolata was not cut, carbon application increased height and fruit production. In plots where A. petiolata was cut, carbon application decreased height and tended to decrease fruit production. Impatiens capensis tended to survive longer when in competition with A. petiolata than with L. maackii. While carbon application may benefit native plant growth in the presence of A. petiolata, the addition of activated carbon after removal of aboveground biomass, a source of both allelochemicals and light competition, may have little benefit as an understory plant restoration tool.

Amur Honeysuckle (Lonicera maackii) Management Method Impacts Restoration of Understory Plants in the Presence of White-Tailed Deer (Odocoileus virginiana)

Abstract Management methods for invasive species vary in their restoration success in the presence or absence of herbivores. We investigated the performance of understory plants after management of the invasive shrub Amur honeysuckle using two herbicide-based methods (cut/paint and basal application) in fenced and unfenced plots. The cut/paint method resulted in the removal of above-ground stems, while the basal application method resulted in the dead stems remaining in place. Light level in the cut/paint treatment was higher than in the basal application treatment, which was higher than in the control (no management) treatment. Across fencing treatments, fruit production, height, and subsequent recruitment of transplanted jewelweed were greater in the cut/paint treatment. Across management treatments, jewelweed plants were taller in the fenced treatment. Native species richness was generally higher in the cut/paint and basal application treatments than in the control treatment. There were more jewelweed recruits, more jewelweed fruits, and greater native species richness in the cut/paint treatment than in the basal application treatment in fenced plots, but these measures were similar in both management treatments in unfenced plots. Thus standing dead stems of Amur honeysuckle offered protection from damage in the presence of herbivores, offsetting the advantage of the cut/paint method seen in the fenced plots. There was a trend for more leaves of transplanted wild ginger in the basal application treatment. There were more invasive garlic mustard and more Amur honeysuckle seedlings in the cut/paint treatment than in the control treatment. Our results illustrate the complexities involved in selecting appropriate restoration management techniques given herbivore pressure, differential species response, and presence of multiple invasive species. In our study, we demonstrated that the basal application honeysuckle management method (and therefore perhaps similar methods that leave the dead stems standing) led to increased understory plant restoration success when compared to the cut/paint method. Nomenclature: triclopyr; garlic mustard, Alliaria petiolata (Bieb.) Cavara & Grande; honeysuckle, Lonicera maackii (Rupr.) Maxim.; jewelweed, Impatiens capensis Meerb.; wild ginger, Asarum canadense L.; white-tailed deer, Odocoileus virginiana Zimmermann.

Guilty in the Court of Public Opinion: Testing Presumptive Impacts and Allelopathic Potential of Ranunculus ficaria

Abstract Information about invasive species is often based primarily on anecdotal evidence, indicating the need for further information. Ranunculus ficaria is an ephemeral riparian plant species that is presumed invasive in the United States, despite the lack of any published information on its impacts. Mechanisms by which R. ficaria may affect native plant species include competition and allelopathy. We examined if R. ficaria negatively affected the growth and reproduction of the native Impatiens capensis and, if so, whether it is by allelopathy, nutrient competition or some combination thereof. We performed a fully-factorial field experiment, manipulating the presence of R. ficaria, nutrients and allelopathy (with the use of activated carbon). The presence of R. ficaria tended to negatively affect life span of I. capensis. In the absence of carbon, R. ficaria significantly decreased seed production, illustrating the negative impact of R. ficaria. In the presence of carbon, there was no effect of R. ficaria, suggesting that carbon may have ameliorated the negative allelopathic effect of R. ficaria. Nutrient competition did not show strong effects. Despite its widespread identification as an invasive species, this is the first study to demonstrate the negative impact of R. ficaria on a native species and the possible role of allelopathy in its success. Further, the negative impacts of this ephemeral species persist well beyond its early growing season, which calls into question previous widespread assumptions about R. ficaria exerting effects primarily on other ephemeral species.

A targeting approach for ecosystem protection

The Critical Ecosystems Team of the US Environmental Protection Agency (EPA), Region 5, has developed an approach to prioritize and target ecologically high-quality areas for enhanced environmental protection in the Midwestern states of Illinois, Indiana, Ohio, Michigan, Minnesota and Wisconsin. Using this approach, we intend to employ a pro-active strategy to protect the environment by protecting and restoring natural ecosystems rather than the traditional EPA approach of remediating and attempting to restore already degraded habitats. The approach consists of two components: (1) partnership and (2) criteria. For the partnership component, we collected, mapped, and summarized information on ecosystems considered critical to federal and state agencies, tribes and non-profit organizations. Multi-county areas with high numbers of ecosystems identified by a variety of partners were designated as ‘Ecologically Rich Regions’. These Ecologically Rich Regions highlight broad geographic areas where there are high levels of partner interest and, correspondingly, areas with high potential for forming collaborative partnerships for enhanced environmental protection. The second component, which relies on criteria, is still under development and defines critical ecosystems as having three important properties: (1) high ecological diversity, (2) potential for long-term sustainability and (3) presence of relict native ecosystems or communities. The information compiled under both components of this ecosystem targeting approach will inform ecological risk managers and assessors about important ecosystems that should be considered in risk management and assessment processes. Published by Elsevier Science Ltd.

A review of garlic mustard (Alliaria petiolata, Brassicaceae) as an allelopathic plant

Abstract Alliaria petiolata is a widespread biennial herb from Eurasia that is one of the most recognizable invasive plants of forests in the eastern United States and southern Canada. After two decades of intensive study on its physiology, ecology, and impacts, this plant has come to be known in both the scientific and gray literature as an allelopathic plant capable of exerting negative, chemically mediated effects on plants and microbes in its environment. A critical review of the literature reveals that there is evidence both supporting and failing to support this assertion, and that conclusions can be affected greatly by the experimental approaches taken, the target species examined, the sources of allelopathic inputs, and environmental factors. The objective of this review is to provide a history of allelopathy research in A. petiolata, describing the various approaches that have been taken and conclusions drawn, and to summarize the current standing of A. petiolata as an allelopathic plant using the most ecologically relevant data on this phenomenon. Finally, we discuss the degree to which allelopathy, versus other mechanisms, may contribute to the invasive success of this plant.

Comparison of allelopathic effects of five invasive species on two native species1

Abstract Recent studies have found that allelopathy can be an important mechanism of plant invasions. Alliaria petiolata, Lonicera maackii, Ranunculus ficaria, Celastrus orbiculatus, and Microstegium vimineum are invasive species found in the Midwestern USA. We investigated the comparative direct and indirect allelopathic effects of these five species in a laboratory setting using leaf extracts in a germination experiment and a growth experiment. Results illustrate that the effect of each invasive species varied with target species and with life stage. Extracts of L. maackii and R. ficaria had the largest overall effects (∼50% reduction) on germination across both species, but effects of extracts varied by target species. Extracts of A. petiolata and C. orbiculatus had a greater effect on germination of E. hystrix than on C. fasciculata. Extracts of L. maackii, M. vimenum, and R. ficaria had larger inhibitory germination effects on C. fasciculata than on E. hystrix. For growth of E. hystrix after 8 wk, C. orbiculatus and L. maackii extracts had the largest (>80%) reduction of biomass, followed by treatment with extracts of R. ficaria (∼ 20% reduction). Treatment with L. maackii and C. orbiculatus extracts reduced height, with extracts of L. maackii having greater effects (60% versus 40% reduction, respectively). Plants treated with L. maackii extracts allocated significantly less biomass to roots. We also found evidence of indirect impacts. Mycorrhizal inoculation overall was most negatively affected by treatment with L. maackii extracts (∼70% reduction), even at low concentrations, and least by treatment with C. orbiculatus, with intermediate effects of A. petiolata, M. vimineum, and R. ficaria. Overall, L. maackii had the strongest effects, followed closely by C. orbiculatus, which was then followed in turn by R. ficaria. These results provide further support for the allelopathic potential of L. maackii and add to the growing body of evidence on the allelopathic potential of R. ficaria and C. orbiculatus. Effects of A. petiolata and M. vimineum were less strong than in other studies, suggesting the importance of variation between populations and in experimental venue.

Habitat Assessment and Conservation Status of Endangered Northeastern Bulrush

Abstract Scirpus ancistrochaetus (Northeastern Bulrush) is a federally endangered sedge that grows in temporary wetlands. We performed surveys of 90 wetlands in Pennsylvania, Maryland, West Virginia, and Virginia, measuring areal extent, stem density, and number of flowering stems of Northeastern Bulrush. We also measured percentage of tree canopy closure, presence of threats, and size of wetland. Percentage of tree canopy closure was negatively correlated with wetland area, percentage of wetland area occupied by North-eastern Bulrush, total number of stems, stem density, and percentage of flowering stems. Wetland area was positively related to percentage of flowering stems and had a tendency to be positively related to stem density, likely in part due to larger wetlands having lower tree canopy closure. Invasive Phalaris arundinacea (Reed Canarygrass) and Microstegium vimineum (Japanese Stiltgrass) were present at 7% and 21% of the wetlands, respectively. Odocoileus virginianus (White-tailed Deer) and Ursus americanus (Black Bear) damage were present in 38% and 17% of wetlands, respectively. Modification of habitat was noted at 27% of wetlands. For wetlands with previous data on population size, 14% had increased, 34% were stable, 25% had decreased, and 27% were absent or had severely decreased. Our recommendations for management include reducing tree canopy closure with control of invasive species and White-tailed Deer where needed.

Genetic Population Structure across the Range of Endangered Northeastern Bulrush, Scirpus ancistrochaetus

Premise of research. Determining population structure and the spatial distribution of existing genetic variation is important for prioritizing areas for conservation of endangered species. Specifically, identifying clusters of genetically differentiated populations ensures that the genetic diversity of a species is conserved. Scirpus ancistrochaetus, northeastern bulrush, is a federally endangered wetland sedge, found in eight states in the northeastern United States, for which little information on genetic structure is available. Methodology. We collected leaf samples from 96 separate wetlands spanning seven states and representing over half of all known sites (N = 71 sites). We sequenced eight variable loci, which were used to construct distance-based trees and calculate population-assignment probabilities to investigate population structure, and we tested isolation by distance by correlating genetic similarity with geographic distance among populations. Pivotal results. All plants sampled from the same wetland (i.e., a population) were genetically identical with low heterozygosity, and there was little to no variation among clustered wetlands within a site. Scirpus ancistrochaetus was genetically structured across its range. Notably, all populations from New England were genetically identical to each other but differed from all other populations, and a similar pattern was observed for northern Pennsylvania populations. Three genetic clusters were identified, including a primarily New England cluster, a primarily Pennsylvanian cluster, and a southern Appalachian cluster, and overall, genetic distances were consistent with isolation by distance. Although genetic clusters mostly corresponded with geography, some populations did not show this geographic-genetic association, suggesting long-distance dispersal; for example, one population from West Virginia was assigned to the New England cluster. Overall, the highest genetic diversity was found within Pennsylvania and nearby states. Conclusions. Whether similarity between geographically distant locations is due to animal-mediated gene flow or retention of ancestral alleles needs additional study. Additionally, the development of a large number of new markers may help to reveal diversity in areas such as New England with wetlands that did not have any diversity using our markers. Nevertheless, conservation of different genetic clusters at a regional scale is important for maintaining the genetic diversity of S. ancistrochaetus, particularly in its southern range, where the greater amount of genetic diversity suggests that this region is a reservoir of genetic variation.