Browsing by Subject "Exotic earthworms"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Impacts of Exotic Earthworms on Soil Temperature within Northern Temperate Forests through Removal of Litter Layer
    (2024) DeLaurentis, Sara
    Northern temperate deciduous and coniferous forests are being increasingly threatened by climate change and other anthropogenic disturbances. Many temperate deciduous and coniferous ecosystems have developed without the presence of earthworms since the last glaciers, which eradicated native earthworm populations. In North America, the status quo has been dramatically altered by the invasion of European earthworms introduced with European settlements, subsequent land use changes, recreation, etc. Geoengineering earthworm species, when introduced to previously earthworm-free forests, are known to drastically rearrange the organic and mineral particles on the soil surface through their consumption of the organic forest floor, burrowing, and casting activities. The substantial changes occurring in the earthworm-infested temperate forests include the reduction in thickness or complete removal of the O horizons and the thickening or creation of mineral A horizons. Here, we report how the structural changes in the forest floors associated with earthworm invasion affect soil temperature, which is critical to regulating biogeochemical, ecological, and hydrological processes in soils. We measured soil temperature profiles at sites with different stages of European earthworm invasion in temperate deciduous and coniferous forest stands of North Central Minnesota. Both vegetation types are geographically and geologically close and share similar air temperatures and precipitation conditions. We found that earthworm-mediated removal of O horizons results in higher mean daily soil temperatures, greater daily temperature amplitudes, and higher maximum and minimum daily temperatures during the growing seasons. The removal of O horizons also results in greater accumulation of growing-degree days. These findings were consistent between deciduous and coniferous forest stands. Our results suggest that earthworm invasion in the northern temperate forests can increase the number of growing degree days in the mineral soils by up to 10 %. Therefore, the ongoing earthworm invasion in the temperate and boreal forests with thick O horizons is likely to substantially intensify the impacts of climate warming on those ecosystems.
  • Thumbnail Image
    Item
    The wave towards a new steady state: effects of earthworm invasion on soil microbial functions
    (2011) Eisenhauer, Nico; Schlaghamersky, Jiri; Reich, Peter B; Frelich, Lee E
    Earthworms are ecosystem engineers that cause a long cascade of ecological effects when they invade previously earthworm-free forests. However, the consequences of earthworm invasion for soil microbial functions are poorly understood. Here, we used two well-studied invasion fronts of European earthworms in northern North American hardwood forests previously devoid of earthworms in order to investigate three stages of earthworm invasion: uninvaded, the front of the leading edge of earthworm invasion and locations invaded at least 10 years previously. Soil microbial biomass, respiration and metabolic quotient were measured. Earthworms had marked effects on soil microbial biomass (−42%) and respiration (−32%). At both sites, impacts were most pronounced at the leading edge of the invasion front, significantly decreasing soil microbial C use efficiency. This was most likely due to the disturbance of the soil microbial community caused by water stress. Based on these results, we hypothesize that effects of earthworm invasion on native soil ecosystem functioning are most pronounced at the peak of the invasion wave. After experiencing this wave, ecosystems possibly enter a new steady state with altered biotic compositions and functions.