Browsing by Subject "Rhamnus cathartica"

Now showing 1 - 6 of 6
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    Common buckthorn (Rhamnus cathartica), European earthworms, and ecosystem management: Invasion and restoration in Minnesota’s deciduous forests
    (2015-05) Roth, Alexander
    Common buckthorn (Rhamnus cathartica) and European earthworms are problematic invasive species in forests of the upper Midwest United States, and it is hypothesized that these two species may have a facilitative relationship. To better understand their invasion, it is necessary to understand how they interact with biotic and abiotic filters, as well as with each other. We established a greenhouse microcosm experiment to investigate the effects of important biotic and abiotic factors on buckthorn establishment and further explored the relationship between buckthorn and earthworms using a 24-plot field study. Using insights from our greenhouse results, we manipulated factors affecting plant colonization in a buckthorn removal experiment in order to improve buckthorn removal and ecosystem restoration efforts. Greenhouse results showed that the presence of earthworms increased buckthorn abundance and biomass across all light and leaf litter treatment levels, supporting the hypothesis that earthworms facilitate buckthorn invasion in upper Midwest forests. Results from the field study, conducted across a naturally-occurring gradient of buckthorn abundance, suggest that buckthorn, in turn, facilitates earthworms in this study system. Plots with higher buckthorn abundance had higher earthworm biomass, with linear regression, mixed model, and path analysis results supporting the directionality of the relationship. Together, these results lend support to a co-facilitative relationship between the two organisms. Co-facilitation my increase the success of both species and strengthen their negative impacts on native species and forest ecosystems. Finally, we tested three buckthorn removal methods (weed-wrenching, cut and paint, and basal bark herbicide application) chosen to differentially affect conditions controlling plant establishment. Removal plots differed in the subsequent cover and diversity of plant regeneration, with methods that disturbed soil and increased available light resulting in the highest species cover and diversity. Non-metric multidimensional scaling ordinations and indicator species analysis demonstrated that the resulting plant communities differed significantly in their species composition, with weed-wrench plots associated with more early-successional community assemblages. Ultimately, removal methods can differentially affect the regeneration of understory vegetation and affect future community succession. Understanding why and how a species invades can encourage a more scientific approach to invasive species management, potentially resulting in improved management outcomes.
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    Ecology and ecosystem impacts of common buckthorn (Rhamnus cathartica): a review
    (2007) Knight, Kathleen S; Kurylo, Jessica S; Endress, Anton G; Stewart, J. Ryan; Reich, Peter B
    In this review, we synthesize the current knowledge of the ecology and impacts of Rhamnus cathartica L., a shrub from Europe and Asia that is a successful invader in North America. Physiological studies have uncovered traits including shade tolerance, rapid growth, high photosynthetic rates, a wide tolerance of moisture and drought, and an unusual phenology that may give R. cathartica an advantage in the environments it invades. Its high fecundity, bird-dispersed fruit, high germination rates, seedling success in disturbed conditions, and secondary metabolite production may also contribute to its ability to rapidly increase in abundance and impact ecosystems. R. cathartica impacts ecosystems through changes in soil N, elimination of the leaf litter layer, possible facilitation of earthworm invasions, unsubstantiated effects on native plants through allelopathy or competition, and effects on animals that may or may not be able to use it for food or habitat.
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    Healthy forests to resist invasion: The role of resources, plant traits, and propagule pressure
    (2015-04) Lodge, Alexandra
    Invasive species are a global problem, dominating habitats, negatively impacting biodiversity, and changing ecosystem processes. There is no consensus regarding which nonnative species are likely to become invasive if introduced, nor which habitats are most susceptible to invasion. To investigate these questions, we studied the native and nonnative plants in 68 oak forest stands in Minnesota, USA. Nonnative plants possessed functional traits similar to those of some native species, suggesting that they exhibit similar growth strategies. These traits allow nonnatives and some natives to grow quickly in high resource environments. Among these same sites, we also examined whether there are characteristics of forests that make them more susceptible or resistant to a particularly pernicious invasive shrub, common buckthorn (Rhamnus cathartica L.). We found that buckthorn presence was best predicted by high propagule availability and site light levels, while buckthorn was more abundant in sites with higher soil fertility, lower resident plant diversity, and less leaf litter. Timber harvesting also affected buckthorn abundance, with more buckthorn in sites that were clearcut or unharvested than in those that were selection harvested. Management practices that minimize increases in light levels and soil disturbance or maintain or increase resident plant diversity (e.g., reduce deer populations) may help uninvaded forests resist buckthorn invasion, especially if local propagule pressure is also reduced. Finally, we also investigated the below-ground effects of buckthorn by examining nutrient cycling across a natural gradient of buckthorn abundance along an invasion front. Buckthorn appears to increase soil nitrogen, organic carbon, calcium, and pH through deposition of nutrient-rich leaf litter. Increases in soil fertility may lead to increased forest productivity and potentially facilitate further spread of buckthorn or other invasive species that may be better able than natives to take advantage of abundant resources. Overall, both the traits of invasive plants and the characteristics of receiving systems can play key roles in determining the success of nonnative species and the potential impacts they may have on native ecosystems.
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    Resident plant diversity and introduced earthworms have contrasting effects on the success of invasive plants
    (Springer International Publishing, 2014) Whitfeld, Timothy J S; Roth, Alexander M; Lodge, Alexandra G; Eisenhauer, Nico; Frelich, Lee E; Reich, Peter B
    Theoretical predictions and empirical studies suggest that resident species diversity is an important driver of community invasibility. Through trait-based processes, plants in communities with high resident species diversity occupy a wider range of ecological niches and are more productive than low diversity communities, potentially reducing the opportunities for invasion through niche preemption. In terrestrial plant communities, biotic ecosystem engineers such as earthworms can also affect invasibility by reducing leaf litter stocks and influencing soil conditions. In a greenhouse experiment, we simultaneously manipulated resident species diversity and earthworm presence to investigate independent and interactive effects of these two variables on the success of several invasive plants. Higher diversity of resident species was associated with lower biomass of invasives, with the effect mediated through resident species biomass. The presence of earthworms had a strong positive effect on the biomass of invasive species across all levels of resident species diversity and a weaker indirect negative effect via decreased soil moisture. Earthworms also weakened the positive correlation between resident species diversity and productivity. We did not observe any interactive effects of resident species biomass and earthworms on invasive species success. Partitioning the net biodiversity effect indicated that selection effects increased with resident species diversity whereas complementarity effects did not. Results suggest that managing for diverse forest communities may decrease the susceptibility of these communities to invasions. However, the presence of introduced earthworms in previously earthworm-free sites may undermine these efforts. Furthermore, future studies of plant community invasibility should account for the effects of introduced earthworms.
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    Role of leafing phenology in the invasion of forest ecosystems by Rhamnus cathartica
    (2015-04) Pretorius, Andrew
    Buckthorn breaks bud earlier in the spring and holds leaves later in the fall compared to co-occurring native understory species and the forest canopy. This phenology may allow buckthorn to take advantage of high light levels prior to canopy closure in spring and after leaf drop in fall. We hypothesized that this unique phenology is one mechanism that facilitates invasion of the forest interior by buckthorn. To test our hypothesis, we experimentally shaded buckthorn seedlings, reducing high light levels in the spring and fall to simulate intact canopy conditions. We measured spring and fall leafing phenology, light availability and seedling survival and growth. After a year and half of shading little mortality was observed but individuals receiving shading treatments had significantly decreased growth. Supporting our hypothesis that access to phenology-induced high light levels in the spring and autumn is one mechanism for buckthorn success in closed canopy forests.