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Comparative Seasonal Observations of Soil Temperature and Moisture and the Occurrence of Two Earthworms Inhabiting Prairie and Deciduous Woodland Sites

Daniel S. Millican and William I. Lutterschmidt
The Southwestern Naturalist
Vol. 52, No. 4 (Dec., 2007), pp. 468-474
Stable URL: http://www.jstor.org/stable/20424861
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Comparative Seasonal Observations of Soil Temperature and Moisture and the Occurrence of Two Earthworms Inhabiting Prairie and Deciduous Woodland Sites
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Abstract

Two unmanaged sites (blackland prairie and deciduous woodland) in Walker County, southeastern Texas, were sampled monthly from February 2000 through January 2001 to determine effects of temperature and moisture on activity and population density of earthworms. The blackland-prairie grassland site supported an endemic earthworm fauna of two species of Diplocardia. A population of Diplocardia invecta was most numerous in the deep clay soil of this grassland site. The deciduous-woodland site supported a population of the exotic species Amynthas corticis (syn. Amynthas diffringens). This epigeic earthworm occurred in an isolated patch of disturbed, sedimentary clay soil in an otherwise sandy area. All observed D. invecta demonstrated seasonal vertical migration, but were quiescent from June to October. All observed A. corticis remained seasonally in the upper 10 cm of woodland soil, but were not observed during July, September, or October. Soil temperature and moisture at depths where earthworms occurred did not differ between the two sites from February through May and from November through January. Juvenile, adult, and total monthly population densities of both D. invecta and A. corticis varied due both to seasonal attrition and reproduction. /// Dos sitios no manejados (pradera de tierra negra y bosque caducifolio) en el condado Walker al sureste de Texas fueron mensualmente muestreados desde febrero 2000 hasta enero 2001 para determinar los efectos que la temperatura y humedad tienen sobre la actividad y la densidad poblacional de las lombrices de tierra. El sitio pradera de tierra negra contaba con una fauna de lombrices endémicas de dos especies de Diplocardia. Una población de Diplocardia invecta fue más numerosa en la parte profunda del suelo arcilloso de este pastizal. El sitio bosque caducifolio contaba con una población exótica de la especie Amynthas corticis (sin. Amynthas diffringens). Esta lombriz epigéica se encontró en un parche aislado de suelo arcilloso sedimentario perturbado en un área generalmente arenosa. Todas las lombrices observadas de D. invecta mostraron una migración vertical estacional, pero se encontraron inactivas desde junio a octubre. Todas las A. corticis observadas se quedaron en la parte superior de 10 cm del suelo forestal, pero no se observaron en julio, en septiembre ni en octubre. No se encontraron diferencias entre los dos sitios en temperatura o en humedad a las profundidades en donde las lombrices habitaban desde febrero hasta mayo y desde noviembre hasta enero. Juveniles, adultos y la densidad poblacional mensual de ambas especies, D. invecta y A. corticis, variaron debido al desgaste y reproducción estacional.

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