Plants and fungi--growing together
Simard, Suzanne W. .
Mycorrhizal networks and seedling establishment: a matter of life or death.
Mycorrhizal networks (MNs) occur where mycelia link the roots of multiple plants, possibly facilitating transfer of nutrients or water. My students, colleagues and I have been examining MNs and their influence on seedling establishment across a range of climatic and site conditions in the interior Douglas-fir (Pseudotsuga menziesii var. glauca) forests of British Columbia, Canada. Interior Douglas-fir ranges from Mexico to central BC, where establishment at high latitudes and elevations is limited by low summer temperatures. At low latitudes and elevations in BC, where the forests interface with grasslands, seedlings are limited by summer drought. This distribution is expected to expand northward with climate change, but also contract in southern BC where increasing summer drought is predicted. Because the edaphic and climatic amplitudes of Douglas-fir are wide, we have used its natural distribution to examine the role MNs play in establishment limitations across a range of sites and regional climates. To characterize MNs, we used morphotyping, DNA sequencing, and microsatellite primers to determine linkage potential between mature trees and establishing seedlings by the same fungal taxa or genets. We found that different Douglas-fir cohorts share several taxa in common, suggesting high potential for MN formation. We also found that most of the 30-150 year-old Douglas-fir trees in a 40m2 stand are interlinked by overlapping Rhizopogon vinicolor/vesiculosis genets. In harvested stands, we used root-excluding mesh bags and isotopic labeling to discover that seedling establishment is significantly enhanced where linked into a MN with older trees, and this is associated with carbon transfer. Seedlings also receive water apparently redistributed through MNs, explaining improved water relations. Although preliminary, our experiments suggest that the degree of MN facilitation increases with climatic and site aridity. Retaining legacy trees and conserving MNs may be important to Douglas-fir establishment, particularly at the changing margins of its range.
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1 - The University of British Columbia, Forest Sciences, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, July 30th, 2008
Time: 3:45 PM