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Summary: Uncoupling of carbon and nitrogen mineralization: role of
microbivorous nematodesq
Mary C. Savina,*, Josef H. GoÈrresb
, Deborah A. Neherb
, Jose A. Amadora
a
Laboratory of Soil Ecology and Microbiology, Department of Natural Resources Science, University of Rhode Island, Kingston, RI 02881, USA
b
Department of Biology, University of Toledo, Toledo, OH 43606, USA
Received 16 November 1999; received in revised form 21 June 2000; accepted 18 January 2001
Abstract
Microfaunal grazing of soil microorganisms affects nutrient mineralization rates. However, the accessibility of microbial food resources to
microfauna depends on matric potential because microfauna require water to move. Laboratory incubations of undisturbed pairs of soil cores
were conducted to evaluate temporal changes in the relationships among C and N mineralization, abundance and distribution of nematode
trophic groups, and matric potential. Cores were collected in May, August, and November 1997, and March 1998 from an old ®eld.
The general relationship between C and N mineralization for all data points did not hold among sampling periods. Differences in this
relationship may have been a result of microbivorous grazing. Nematode abundance did not decrease as matric potential decreased,
suggesting microbivorous grazers were not merely excluded from their food resources, but survived in isolated water-®lled pores as soil
dried. We suggest that at 250 kPa nematodes and their microbial food resources are enclosed within spatially isolated water pockets and this
entrapment leads to increased microbivorous grazing and microbial activity per unit biomass (qCO2). Only at 250 kPa was there a strong
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