Soil Moisture and Temperature: Tolerances and Optima for a Non-Native Earthworm Species, Amynthas agrestis (Oligochaeta: Opisthopora: Megascolecidae)
ABSTRACT Field observations indicate an invasion by the non-native, Asian earthworm species Amynthas agrestis (Goto and Hatai 1899) in the Great Smoky Mountains National Park (GSMNP). The aim of this study was to determine if A. agrestis was capable of surviving in the ridge-top soil along an invasion front in a mesic—xeric habitat gradient in GSMNP. Additionally, this study sought to determine optimum and tolerance conditions for A. agrestis within a range of soil moistures and temperatures. Investigating soil temperature and moisture as parameters of earthworm survivability will allow for more predictive power when investigating the GSNMP invasion. Although A. agrestis invasions are widespread in eastern North America, few studies have addressed factors that may influence their distribution and their potential impacts on ecosystem processes. Using incubators and PVC tube microcosms, it was determined that A. agrestis was able to survive in the GSMNP ridge-top soil at temperatures of 12 °C and 25 °C. No survival was observed at temperatures of-5, 5, or 35 °C at any soil moisture level. No survival occurred in 25 °C dry (8% gravimetric water) treatments. Of the conditions tested, maximum survival plus fresh-weight maintenace occured at 12 °C and mid-moisture (24% gravimetric water), but highest activity and effects on litter and soil structure occurred at 25 °C and high soil moisture (57% gravimetric water; field capacity). Soil moisture contributed to the success of A. agrestis at higher temperatures within the tolerance conditions; more moisture increased the survival rate and decreased weight-loss.
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ABSTRACT: European and Asian earthworm invasions are widespread in North America. European earthworms especially are well-known to cause dramatic changes in ecosystems in northern, formerly glaciated portions of the continent, but less is known about the impacts of earthworm invasions in unglaciated areas inhabited by indigenous earthworms. We monitored fluctuations in the spatial extent of an Amynthas agrestis (Megascolecidae) population in the Great Smoky Mountains National Park in eastern Tennessee, USA. Two years of monthly growing-season observations revealed that the distribution of the earthworm population was dynamic, but overall distribution was closely linked to temperature and moisture with dramatic reductions of earthworm numbers associated with very dry conditions. In plots where A. agrestis were more often detected, we measured increased A-horizon soil aggregation and decreased thickness of the Oe/Oa-horizon. However, A. agrestis was not related to A-horizon microbial biomass, A-horizon C:N, Oi-horizon (litter) thickness, or mass of forest floor (O-horizon). Reductions in millipede species richness and density were associated with frequency of A. agrestis presence, possibly due to direct competition for food resources (Oe/Oa material). This evidence for potentially negative interactions between millipedes and A. agrestis suggests that expansion of the non-native earthworm into new habitats in the Park may alter soil physical properties and could pose a threat to native millipede diversity. KeywordsEarthworm– Amynthas –Invasive species–Millipede–Soil aggregationBiological Invasions 01/2011; 13(2):349-358. · 2.72 Impact Factor
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ABSTRACT: The endogeic earthworm Pontoscolex corethrurus (Müller, 1857) was the most abundant species (75%) insoil contaminated with hydrocarbons, mostly benzo(a)pyrene (BaP), in the state of Tabasco (Mexico). Theearthworm P. corethrurus was tested for its capacity to remove 100 mg BaP kg−1from an Anthrosol soil(sterilized or not) and amended with legume Mucuna pruriens (L.) DC. var. utilis (Wall. ex Wight) Baker exBurck (3%) or the grass Brachiaria humidicola (L.) DC (3%) (recently renamed as Urochloa humidicola (Ren-dle) Morrone & Zuloaga) in an aerobic incubation experiment. P. corethrurus removed 26.6 mg BaP kg−1from the sterilized soil and application of B. humidicola as feed increased this to 35.7 mg BaP kg−1and M.pruriens to 34.2 mg BaP kg−1after 112 days. The autochthonous microorganisms removed 9.1 mg BaP kg−1from the unsterilized soil and application of B. humidicola increased this to 18.0 mg BaP kg−1and M.pruriens to 11.2 mg BaP kg−1. Adding P. corethrurus to the unsterilized soil accelerated the removal of BaPand 36.1 mg kg−1was dissipated from soil. It was found that the autochthonous microorganisms removedBaP from soil, but addition of P. corethrurus increased the dissipation 4-fold. The endogeic earthworm P.corethrurus can thus be used to remediate hydrocarbon-contaminated soils in tropical regions.Applied Soil Ecology 04/2013; 70:62-69. · 2.21 Impact Factor