Browsing by Subject "earthworm invasion"

Now showing 1 - 3 of 3
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    Changes in hardwood forest understory plant communities in response to European earthworm invasions
    (Ecological Society of America, 2006) Hale, Cindy M; Frelich, Lee E; Reich, Peter B
    European earthworms are colonizing earthworm-free northern hardwood forests across North America. Leading edges of earthworm invasion provide an opportunity to investigate the response of understory plant communities to earthworm invasion and whether the species composition of the earthworm community influences that response. Four sugar maple-dominated forest sites with active earthworm invasions were identified in the Chippewa National Forest in north central Minnesota, USA. In each site, we established a 30 × 150 m sample grid that spanned a visible leading edge of earthworm invasion and sampled earthworm populations and understory vegetation over four years. Across leading edges of earthworm invasion, increasing total earthworm biomass was associated with decreasing diversity and abundance of herbaceous plants in two of four study sites, and the abundance and density of tree seedlings decreased in three of four study sites. Sample points with the most diverse earthworm species assemblage, independent of biomass, had the lowest plant diversity. Changes in understory plant community composition were most affected by increasing biomass of the earthworm species Lumbricus rubellus. Where L. rubellus was absent there was a diverse community of native herbaceous plants, but where L. rubellus biomass reached its maximum, the herbaceous-plant community was dominated by Carex pensylvanica and Arisaema triphyllum and, in some cases, was completely absent. Evidence from these forest sites suggests that earthworm invasion can lead to dramatic changes in the understory community and that the nature of these changes is influenced by the species composition of the invading earthworm community.
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    Impact Of Invasive Earthworms On Soil Microbial Communities
    (2023-04) Liu, Chang
    The invasion of non-native earthworms may drive significant changes to the local soil environment. Previous research shows that invasive earthworms can affect the soil physical and chemical properties and soil microbial activity. The changes of soil microbial community structures are strongly relevant to soil health and soil biodiversity. In research conducted near a hardwood forest at Northern Minnesota, it was found that earthworm invasion disrupts the soil microbial species diversity and shifted the community structure (Jang et al., 2022). Learning the fact that there are multiple other places formerly glaciated are under earthworm invasion, this study aims to extend the previous research to a global level. The approach of this study is to conduct 16S rRNA gene amplicon sequencing to investigate how the structure of microbial species are affected by non-native earthworms at earthworm-invaded sites including Alaska, Sweden and mesocosm study. Results from this study will lead to a greater understanding of earthworm dynamics and their impact on the broader soil community and carbon dynamics. This study uses 16S rRNA gene amplicon sequencing to have a comprehensive view of the soil microbial communities affected by earthworm invasion. Soil samples were collected at the study sites and soil DNA were extracted. The samples were sequenced for downstream analysis. The objective of this study was to examine the effects of earthworm invasion on the soil microbial community structure, and it was hypothesized that the earthworm-invaded soils would have different soil microbial community structures compared to non-invaded sites. The study found that there are differences in soil microbial communities depending on the extend how the soil was invaded by earthworms. The results are significant to understand the soil microbial activities, provide suggestions om regulation of earthworm invasion, and maintenance of soil health.
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    Regional extent of an ecosystem engineer: Earthworm invasion in northern hardwood forests
    (2007) Holdsworth, Andrew R; Frelich, Lee E; Reich, Peter B
    The invasion of exotic earthworms into northern temperate and boreal forests previously devoid of earthworms is an important driver of ecosystem change. Earthworm invasion can cause significant changes in soil structure and communities, nutrient cycles, and the diversity and abundance of herbaceous plants. However, the regional extent and patterns of this invasion are poorly known. We conducted a regional survey in the Chippewa and Chequamegon National Forests, in Minnesota and Wisconsin, USA, respectively, to measure the extent and patterns of earthworm invasion and their relationship to potential earthworm introduction sites. We sampled earthworms, soils, and vegetation in 20 mature, sugar maple-dominated forest stands in each national forest and analyzed the relationship between the presence of five earthworm taxonomic groups, habitat variables, and distance to the nearest potential introduction site. Earthworm invasion was extensive but incomplete in the two national forests. Four of the six earthworm taxonomic groups occurred in 55–95% of transects; however 20% of all transects were invaded by only one taxonomic group that has relatively minor ecological effects. Earthworm taxonomic groups exhibited a similar sequence of invasion found in other studies: Dendrobaena > Aporrectodea = Lumbricus juveniles > L. rubellus > L. terrestris. Distance to the nearest road was the best predictor of earthworm invasion in Wisconsin while distance to the nearest cabin was the best predictor in Minnesota. These data allow us to make preliminary assessments of landscape patterns of earthworm invasion. As an example, we estimate that 82% of upland mesic hardwood stands in the Wisconsin region are likely invaded by most taxonomic groups while only 3% are unlikely to be invaded at present. Distance to roads and cabins provides a coarse-scale predictor of earthworm invasion to focus stand-level assessments that will help forest managers better understand current and potential forest conditions and identify uninvaded areas that could serve as important refugia for plant species threatened by earthworm invasion.