Minimal direct contribution of arbuscular mycorrhizal fungi to DOC leaching in grassland through losses of glomalin-related soil protein

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This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Arbuscular mycorrhizal fungi (AMF) have multiple influences on ecosystem C cycling, but most research has focused on ecosystem C gains. We explore here the possibility of direct contributions of AMF to ecosystem C losses, namely via leaching of glomalin-related soil protein (GRSP). We tested the hypothesis that GRSP, an operationally defined SOM pool to which AMF contribute (especially as evidenced with monoclonal antibody MAb32B11-based detection), is mobile in soils and can be lost in leachate. For two New Zealand soils, we showed that only insignificant amounts of GRSP were lost: a maximum of 0.03% of MAb32B11-immunoreactive GRSP present in soils was lost during the week-long experiment, representing a minute fraction of total leachate dissolved organic carbon (0.06%). Our data showed that this pathway of C loss may be relatively unimportant in many soils. However, other indirect contributions of AMF to soil C losses remain yet to be explored.

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Wood, nematodes, and the nematode-trapping fungus Arthrobotrys oligospora

Product Description
This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Researchers have proposed that Arthrobotrys oligospora and related fungi trap soil nematodes to obtain nitrogen and thereby compete saprophytically for carbon and energy in nitrogen-poor environments, including litter and wood. The current study tested two hypotheses concerning this model. The first was that wood decomposition would be enhanced if both large numbers of nematodes (a potential nitrogen supply) and A. oligospora (a cellulolytic organism that can use that N supply) were present. The second was that A. oligospora trapping activity would increase if large numbers of nematodes were added to soil containing abundant carbon (a wood dowel or chip). Although the first hypothesis was supported by an in vitro experiment on agar (A. oligospora degraded much more wood when nematodes were present), neither hypothesis was supported by an experiment in vials containing field soil. In soil, wood decomposition was unaffected by the addition of A. oligospora or large numbers of nematodes. Whereas A. oligospora trapped virtually all nematodes added to agar cultures, it trapped few or no nematodes added to soil. Given that the fungal isolate was obtained from the same soil and that the fungus increased to large numbers (>1×10^3 propagulesg^-^1 soil), the failure of A. oligospora to trap nematodes in soil is difficult to explain. Soil nitrate levels, however, were high (71 mg kg^-^1), and it is possible that with lower nitrate levels, trapping in soil might be stimulated by wood and nematodes.

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