Colonization and Effects of Garlic Mustard (Alliaria petiolata), European Buckthorn (Rhamnus cathartica), and Bell's Honeysuckle (Lonicera × bella) on Understory Plants After Five Decades in Southern Wisconsin Forests (original) (raw)
Related papers
2015
This interdisciplinary research explores the ecological impacts and underlying evolutionary mechanisms associated with the spread of Lonicera maackii (Amur honeysuckle), one of the most aggressive and abundant invasive species throughout the Midwest United States. The main goal of this research is to better understand how the encroachment of Amur honeysuckle impacts the Midwest native Quercus alba (white oak) population in a Nature Conservancy oak savanna restoration project (Nachusa Grasslands) located in Lee County, Illinois, USA, with particular focus on mechanisms required for successful oak regeneration and recruitment (i.e. carbon assimilation, soil quality, soil moisture/ temperature, and plant available nutrients). This study also aims to explore the spatial-temporal long distance dispersal patterns of Amur honeysuckle, as inferred by population genetics, in order to better understand the mechanisms and pathways by which Amur honeysuckle is spreading throughout Illinois. Ultimately, the low light levels measured in the understory of the oak savanna restoration study site at Nachusa Grasslands yielded marginal seasonal carbon assimilation totals for white oak seedlings, especially when compared to the high seasonal carbon assimilation totals modeled for white oak seedlings had they been growing in full sun light conditions. In relation to belowground properties, this study found no significant differences between any of the soil characteristics (i.e. wet macroaggregate soil stability, moisture, temperature, carbon nitrogen ratios, and nutrient levels) measured in adjacent soil samples collected under and away from Amur honeysuckle within the oak savanna restoration study site at Nachusa Grasslands. Findings from the population genetics analyses in this research supports previous research that Amur honeysuckle displays characteristics associated with stratified dispersal. Specifically, a lack of correlation between genetic distance and geographic distance for the Illinois Amur honeysuckle subpopulations suggest that active gene flow between these subpopulations occurs via regional long distance dispersal events. The New York Botanical Garden subpopulation was identified as genetically isolated from all other subpopulations. The Arnold Arboretum at Harvard University and The Morton Arboretum also displayed patterns of genetic isolation from the other subpopulations, more so than from each other. Management recommendations, based off findings from this research, are provided.
The American Midland Naturalist, 2012
Garlic mustard, Alliaria petiolata (M. Bieb.) Cavara & Grande, is an introduced biennial forb that has commonly been referred to as highly invasive and as having substantial negative effects on other plants in the eastern deciduous forests of North America. However, several recent studies have documented only modest effects on other plant species, raising questions as to the extent of the threat really posed by A. petiolata. Alliaria petiolata often exhibits an alternating two-year life-history cycle, with high rosette years alternating with high flowering stem years. It has been proposed that this cycle is partly driven by intraspecific competition between the stems and the rosettes. In a two-year study, we extensively sampled A. petiolata in a Minnesota woodland at two spatial scales, including 6.5 km of belt transects in a 6.8 ha study grid (20 3 20 m cells) and 90 small sampling quadrats (1.0 3 0.5 m) within the grid. At the large scale, we compared seed bank abundance and diversity of other herbaceous plants with A. petiolata abundance. Using the monitoring data we also investigated whether this population was exhibiting an alternating two-year life-history cycle, consistent with the intraspecific competition hypothesis for this phenomenon. At the small scale, we compared A. petiolata abundance with the abundance of other plants, including herbs, ferns, shrubs, and tree seedlings. We also conducted an ex-situ pot experiment in which we planted seeds of six tree species in soil collected from dense A. petiolata patches and soil collected where A. petiolata was absent and recorded emergence rates and seedling growth over an 8 wk period. Overall, we found little evidence that A. petiolata was negatively affecting other plant species. This is consistent with other recent studies and indicates that, despite earlier claims to the contrary, A. petiolata seems to be more a product than an agent of change in eastern North American deciduous forests. We also documented an alternating two-year life-history cycle, providing additional evidence to support the hypothesis that this cycle is at least partly being driven by intraspecific competition.
Forest Ecology and Management, 2007
As managing forests for biodiversity becomes more common, it is important to understand how understory species respond to disturbance. We monitored changes in species' dominance, calculated as importance values, over a 4-year period in order to determine how species' dominance varied with disturbance intensity and gap position. An experimental linear canopy opening was created in a southern New England mixed-oak forest, and plots were established on the south side, center, and north side of the opening. All vegetation was removed in half of the plots, simulating a lethal disturbance. In the other half of the plots, only the overstory was removed, simulating minimal disturbance (release plot). Before the disturbance, Dennstaedtia punctilobula dominated the plots, but typical forest understory species such as Kalmia latifolia, Trientalis borealis, Maianthemum canadense, and Mitchella repens were very common. After the disturbance, D. punctilobula expanded and continued to remain dominant in all types of plots. Early successional species, such as Carex pensylvanica, Poaceae species, Rubus ideaus, and Rubus allegheniensis dominated the lethal and center plots; late successional forest understory species experienced a reduction in frequency and cover in these plots. However, in release and edge plots, late successional species maintained relatively similar frequencies and covers to pre-disturbance values. The ability of early successional species to seed into lethal plots and grow rapidly in the high light environment of the center plots allowed them to dominate in these plots. Late successional species were able to remain relatively dominant in release plots through clonal expansion and in edge plots through exclusion of early successional species from low light levels. Three years after the disturbance, most of the residual forest understory species had attained similar frequencies and covers to pre-disturbance values in all types of plots. Thus, although there is some initial loss of residual species in highly disturbed areas and in the center of the opening, most of these species are able to recover in a relatively short time period. However, locally uncommon species may be vulnerable to permanent loss. In order to minimize loss of species from the understory, forest managers should attempt to keep groundstory disturbance as minimal as possible where desirable late-successional species exist and create edgepartial shade effects with the remaining canopy for regeneration treatments.
Landscape position influences the distribution of Garlic Mustard, an invasive species
We investigated the distribution and abundance of Alliaria petiolata, an invasive biennial, with respect to historical land use, and examined environmental conditions to look for correlations with distribution patterns. Sixty currently forested plots in Cuyahoga Valley National Park, OH were chosen based on 1959 land use: agricultural (open) versus forested. Plots were analyzed for Garlic Mustard distribution, abundance, invasion area, and incursion distance. Garlic Mustard distribution did not vary with historical land use, but did vary signifi cantly with distance from rivers and with elevation. Polygon area:perimeter values were also correlated with invasion. These results differ from studies done with Garlic Mustard in New England where historical land use appeared to be a larger factor in distribution. These results suggest the importance of landscape corridors in biological invasions and can be used to identify areas with greater potential for invasive species in this region.
Restoration Ecology, 2004
Restoration often includes control of invasive plants, but little is known about how native plant communities respond to this control. The biennial Alliaria petiolata (M. Bieb.) Cavara and Grande (garlic mustard) is one of the most prevalent invasive plants in forests of eastern North America. We investigated the effects of the herbicide Roundup (glyphosate) on Alliaria and the response of the forest floor plant community to the herbicide and the subsequent decline of Alliaria. In an old-growth Acer-Fagus stand and a second-growth Liriodendron-dominated stand in Hueston Woods State Nature Preserve, Ohio, United States, we spot applied Roundup in November 2000 and 2001 in 25 1 • 1-m plots and maintained 25 control plots. Herbicide decreased Alliaria density in both stands and reduced the density of other species in leaf during treatment (mostly exotic winter annuals) in the old-growth stand. Treatment did not affect the initial density of the Alliaria cohort that germinated in the spring of 2001, but decreased the 2002 cohort. Community differences were found in the old-growth stand after Alliaria reduction, specifically greater cover of spring ephemerals in the herbicide treatment. In the second-growth stand, herbicide treatment increased reproduction of the late-summer perennial, Phryma leptostachya. These results indicate that glyphosate reduces Alliaria without negatively impacting native species and that some native species respond positively to a single-year reduction in this invasive biennial.
Journal of Environmental Sciences
Like many natural areas in human-disturbed landscapes, those in the Midwest are susceptible in varying degrees to invasion from non-indigenous species. Approximately one-fourth of the plant species occurring in the Midwest are non-indigenous; of these, garlic mustard, Alliaria petiolata (Brassicaceae), is considered among the most problematic. This study examined the distribution and abundance of A. petiolata at Allerton Park, a natural area in east-central Illinois, with respect to previous land use, plant community traits, and distance from paths. There was no significant difference in A. petiolata density among land cover categories (mean = 14.7 plants m -2 ; Kruskal-Wallis: n = 333, df = 2, H = 0.17, P = 0.92). There also was no significant difference in A. petiolata cover between forested areas having different land-use histories in 1997 and 1998 (CMH test 1997: df = 4, χ 2 = 7.25, P = 0.12; CMH test in 1998: df = 3, χ 2 = 5.47, P = 0.14). However, A. petiolata density was significantly greater within a 35 m band from footpaths in Forest, the land cover category with the least disturbance (2-way ANOVA: df = 2.0, P = 0.009). Plant density (excluding A. petiolata) per m 2 was positively correlated with species richness (Pearson's r = 0.394, P = 0.0001) and density of A. petiolata rosettes (Pearson's r = 0.235, P = 0.019). The density per m 2 of A. petiolata rosettes was negatively correlated with the density of mature A. petiolata plants (Pearson's r = -0.340, P = 0.001). seedlings and saplings, or (3) retard succession. Based on these criteria, garlic mustard (Alliaria petiolata [Bieb.] Cavara & Grande), a biennial herb native to Europe, is among the most significant of the non-indigenous species currently impacting Illinois and other Midwestern forest natural areas (Brothers and Spingarn 1992).