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: 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. DOI:10.1016/j.apsoil.2013.04.009 · 2.21 Impact Factor
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ABSTRACT: Earthworms can accelerate the removal of contaminants from soil. Earthworms change the physical and chemical properties of soil by mixing it with organic material and through their burrowing they improve aeration and render contaminants available for microorganisms. The presence of earthworms in contaminated soil indicate that they can survive a wide range of different organic contaminants, such as pesticides, herbicides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and crude oil, at least when concentrations of the contaminant are not too high. The improvement of the soil due to their activity and the microorganisms in their digestive track can contribute to the accelerated removal of contaminants from soil, but sometimes their casts adsorb the pollutant so that its dissipation is delayed. There are limits, however, on how earthworms can be used to remediate soil, which will be discussed in this review.Applied Soil Ecology 07/2014; 79:10–25. DOI:10.1016/j.apsoil.2014.02.010 · 2.21 Impact Factor
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ABSTRACT: Biological invasions are one of the most significant global-scale problems caused by human activities. Earthworms function as ecosystem engineers in soil ecosystems because their feeding and burrowing activities fundamentally change the physical and biological characteristics of the soils they inhabit. As a result of this “engineering,” earthworm invasions can have significant effects on soil physical, chemical and biological properties. The species Amynthas agrestis (family Megascolecidae) was introduced to the United States from Asia, and has expanded its distribution range to include relatively undisturbed forests. Here, to clarify life history traits, we reared individuals under seven different conditions of food provision using litter, fragmented litter and soil, and also analyzed the stable isotope ratios of field-collected specimens to investigate their food resources in the field. Second, we examined whether prescribed fire can be used to manage invasive earthworms. We constructed eight experimental plots, each with 100 individuals of A. agrestis each, and burned half of the plots. The feeding experiment showed that the earthworms in units containing soil and some form of organic matter (litter and/or fragmented litter) produced many cocoons, indicating that litter and fragmented litter are important food resources for them. Stable isotope analyses also supported this result. During the experimental fires, average soil temperature at 5 cm depth increased by only 7.7 °C (average maximum of 32.2 °C). Litter mass was significantly reduced by the fires. Although numbers of A. agrestis and cocoons recovered from burned and unburned plots were not different, the viability of cocoons was significantly lower in burned plots. Fire may also reduce the survival rate of juveniles in the next year by depriving them of their preferred food resource. Most native earthworms in the United States live in the soil, while many invasive ones live in the litter layer and soil surface. Therefore, prescribed fire could be a viable tool for control of invasive earthworms without negatively impacting native earthworm populations.Soil Biology and Biochemistry 03/2015; 82. DOI:10.1016/j.soilbio.2014.12.011 · 4.41 Impact Factor