Yazar "Melnichuk, Ryan Dustin Scott" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim
    Öğe
    Can commercial mulches be reservoirs of invasive earthworms? Promotion of ligninolytic enzyme activity and survival of Amynthas agrestis (Goto and Hatai, 1899)
    (Elsevier Science Bv, 2015) Bellitürk, Korkmaz; Goerres, Josef Hubert; Kunkle, Jeanne; Melnichuk, Ryan Dustin Scott
    Amynthas agrestis is an exotic, invasive earthworm in North America that has been associated with horticulture settings as well as damage to forest soil. An experiment was conducted to find out whether A. agrestis, an earthworm commonly found in mulches in Vermont, stimulates ligninolytic enzymes in the presence of commercial wood mulches. Mesocosms filled with a sandy loam soil were topped with either spruce, cedar or pine mulch. Half of the mesocosms received juvenile A. agrestis, the other half did not. After 7 weeks soils were analyzed for phenoloxidase and peroxidase activity. Most A. agrestis survived and developed into adults during the incubation period. Significantly greater phenoloxidase activity was detected in soils with A. agrestis than without earthworms. Mean (standard deviation) phenoloxidase activities in the presence of A. agrestis were 0.15 (+/- 0.10), 1.14 (+/- 0.46), 2.71 (+/- 0.98) mu mol g(-1) h(-1) for pine, spruce and cedar respectively, and 0.012 (+/- 0.023), 0.25 (+/- 0.25), 0.78 (+/- 0.45) mmol g(-1) h(-1) in the absence of A. agrestis. There was significantly greater peroxidase activity for the pine and spruce treatment when earthworms were present. Mean peroxidase activities were 0.47 (+/- 0.21), 0.94 (+/- 0.29), 1.20 (+/- 0.77) mmol h(-1) g(-1) soil for pine, spruce and cedar, respectively for soils with A. agrestis and 0.15 (+/- 0.10), 0.37 (+/- 0.10), 0.63 (+/- 0.30) mmol h(-1) g(-1) soil in the absence of earthworms. The increased ligninolytic activity in combination with successful maturation of juveniles into adult A. agrestis suggests that mulch can be habitat for these invasive earthworms. This finding is supported by a survey of master gardeners in Vermont and New Hampshire 20% of whom reported to have seen these earthworms mainly in their gardens and mulched beds. (C) 2014 Elsevier B.V. All rights reserved.
  • Küçük Resim
    Öğe
    Temperature and moisture variables affecting the earthworms of genus Amynthas Kinberg, 1867 (Oligachaeta: Megascolecidae) in a hardwood forest in the Champlain Valley, Vermont, USA
    (Elsevier Science Bv, 2016) Gorres, Josef Hubert; Bellitürk, Korkmaz; Melnichuk, Ryan Dustin Scott
    Earthworms in the genus Amynthas Kinberg, 1867, are invasive, annual species of hardwood forests in the northeastern USA. Their phenology is not well-known. Our objectives were (1) to conduct field measurements to validate temperature cues on hatching and mortality, (2) to relate abundance to growing degree days and moisture deficit, (3) to validate maturation time for Amynthas that was derived from geographic distribution information and climate data. We sampled a complex of Amynthas species in the Champlain Valley, Vermont, from early April to first frosts in December 2011. In agreement with laboratory studies conducted for Amynthas agrestis, hatchlings of earthworms in the genus Amynthas were observed after air termperatures first reached above 10 degrees C and die-offs were observed in September and October after temperatures fell below 5 degrees C. Maturation time was estimated as 77 to 93 days and occurred at 1000 degrees C growing degree days (base 5 degrees C) accumulated from the time of hatching. Juvenile and adult Amynthas abundance was not linearly related to moisture deficits. Juvenile abundance was linearly related to the average daily increment in growing degree days between sampling dates. In 2014, cocoons survived a winter with soil temperatures below -20 degrees C. Overall lab benchmarks established for A. agrestis agreed with observations for the Amynthas complex at the study site (C) 2015 Elsevier B. V. All rights reserved.