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Doctoral thesis, 2001

Responses of ectomycorrhizal fungi to changes in carbon and nutrient availability

Fransson, Petra

Abstract

Ectomycorrhizal (ECM) fungi may receive 20% of the total C fixed by their host plants and are essential components of host nutrient acquisition. As a consequence of the vast physiological diversity that exists among ECM fungi, changes in community structure may potentially alter C and nutrient allocation and turnover within forest ecosystems. Effects of atmospheric CO2 enrichment and balanced nutrient addition on the community structure of ECM fungi were investigated. Significant effects of elevated CO2 , as well as elevated nutrient levels were found. Daily nutrient additions for 10 years did not cause reductions in the density of ECM roots or the degree of root colonisation, in contrast to other studies. Some species became more common due to nutrient additions; Cenococcum geophilum, Amphinema byssoides, Tylospora fibrillosa, tomentelloid species, and others, Piloderma byssinum and P. croceum, became less common. High variability among samples made individual species responses difficult to distinguish. Data suggest that the same species may respond similarly to both elevated CO2 and nutrient additions. In laboratory experiments, CO2 enrichment increased the production of extraradical mycelium by Hebeloma crustuliniforme, increasing mycelial spread and root colonisation. Under field conditions such a response could enable species to increase in abundance. The natural abundance of the stable isotope 13 C in fruitbodies can be used as a tool to distinguish between the two functional groups ECM and saprotrophic fungi. However, some caution is neccesary in the interpretation since values overlap between the two functional groups. The 13 C values can also be used to reveal the host-origin of carbon in mycorrhizal fungi in mixed forests. Generalist fungi, which can be associated with several different tree species, were found to receive most of their C from overstorey trees, as indicated by their high d 13 C values. This implies that large trees which are able to fix more C potentially subsidise smaller trees via a common ECM mycelial networ

Keywords

Basidiomycetes; boreal forest; morphotype; whole-tree chamber; fertilisation; 15 N; Picea abies; Pinus sylvestris; Paxillus involutus

Published in

Acta Universitatis Agriculturae Sueciae. Silvestria
2001, number: 235
ISBN: 91-576-6319-X
Publisher: Swedish University of Agricultural Sciences

Authors' information

Swedish University of Agricultural Sciences, Department of Forest Mycology and Pathology

UKÄ Subject classification

Forest Science
Ecology

URI (permanent link to this page)

https://res.slu.se/id/publ/107661