Temperature and moisture variables affecting the earthworms of genus Amynthas Kinberg, 1867 (Oligachaeta: Megascolecidae) in a hardwood forest in the Champlain Valley, Vermont, USA

Abstract

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.