Forest Investment Account (FIA) - Forest Science Program
FIA Project Y093314

    Determining stand level structures in dry Douglas-fir forests that maintain appropriate levels of ectomycorrhizal genetic diversity to facilitate Douglas-fir regeneration
Project lead: Simard, Suzanne (University of British Columbia)
Author: Simard, Suzanne W.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Our currently FSP funded research is showing that linkage into a common mycorrhizal network (CMN) with residual trees is important to the establishment of Douglas-fir seedlings in the interior dry Douglas-fir forests. A CMN is an underground network of genetically compatible mycorrhizal fungi linking roots of trees of the same or different species. The CMN associated with residual trees in cutover or burned areas appears to facilitate new regeneration by providing mycorrhizal inoculum, carbon, and water from the mature trees. This project examines the spatial extent and genetic structure of common mycorrhizal networks (CMNs) in dry Douglas-fir forests. The information derived from this project will apply directly to the sustainability program, under the theme of ecosystem structure, function and processes, and biodiversity related to forest management (theme 1), the topic of effectiveness of stand level structures in maintaining biodiversity (topic 1.4), priority c (appropriate targets and configurations of stand level structures in dry forests for maintaining biodiversity). Specifically, We are characterizing the spatial extent, structure, and genetics of common mycorrhizal networks linking overstory Douglas-fir trees with understory cohorts in mature and old-growth forests in the Interior Douglas-fir zone. This information will be used to determine target sizes and configurations of green tree patches that should be retained following disturbance (e.g., partial cutting, salvage logging following wildfire) in order to conserve the ability of the ecosystems to regenerate and hence develop into healthy stand structures. We will contrast CMNs between two soil moisture regimes within the dry, cool biogeoclimatic subzone (IDFdk) of southern interior British Columbia to: (1) provide site series specific guidelines; (2) test whether the importance of CMN facilitation increases with site water stress, and (3) use soil moisture regime as a proxy for changes in site water stress and regeneration potential with climate change.

Tree establishment and growth, and hence ecosystem productivity, are largely influenced by the ectomycorrhizal colonization of tree roots. Of particular importance is the potential for fungal mycelia to link the roots of individual trees to other trees or new regeneration, acting as conduits for the exchange of water, carbon and nutrients. The transfer of C, N, and P between mycorrhizal plants has been demonstrated in the field (Smith & Read 1997; Simard et al. 2002; Leake et al. 2004; Simard & Durall 2004), including net C transfer from Betula papyrifera to P. menziesii trees in ICH forests (Simard et al. 1997a; Simard et al. 1997b). Our recent FSP funded work has demonstrated that linkage into a CMN with residual trees improves the survivability and productivity of naturally and artificially regenerated Douglas-fir seedlings, and hence is important in stand establishment following disturbance. A newly initiated FSP project is also examining how the importance of this CMN facilitation changes with increasing regional drought associated with climate change. In this project, we will use contemporary tools in molecular genomics to distinguish between individual genotypes of fungi and tree roots (Saari et al. 2005), allowing quantitative and qualitative examination of CMNs among trees and understory regeneration in multi-cohort Douglas-fir forest stands.

The importance of Interior Douglas-fir [P. menziesii var. glauca (Beissn.) Franco] forests to British Columbia’s economy and ecosystems are well understood, yet associations between forest dynamics and belowground ecology are not. Moisture deficits common to these forests make them particularly vulnerable to ecological stresses associated with climate change, wildfires, and outbreaks of insects and disease. Conserving or strengthening functional links between tree generations could help mediate this stress and bolster resilience to disturbance (Smith & Read 1997).

Rhizopogon vinicolor & vesiculosus is the focal ectomycorrhizal fungal species in this study for numerous reasons. We have found in earlier FSP funded research that these fungal species dominate Douglas-fir roots of every tree cohort, and therefore have high potential for linking multiple tree cohorts in a forest (Roth & Berch 1992; Molina et al. 1999). Second, these fungi are easy to recognize in the field and culture in the lab, and we have already developed a good genetic reference library of samples from the interior Douglas-fir forests. Third, Rhizopogon has been shown to translocate nutrients and water to host trees, resulting in increased seedling growth and resistance towards several root pathogens (Cairney & Chambers 1999). The “exploration-type” rhizomorphs formed by Rhizopogon can extend up to several decimeters in length (Agerer 2001), and are particularly effective in the uptake of nutrients and water (Bowen 1968; Read & Boyd 1986). Fourth, the truffle-like fruit bodies of these fungi are important components in small mammal diets (e.g., squirrels), some of which are keystone species in food webs of North American forests (Maser & Maser 1988). Despite their abundance and complex role in forest ecosystems, R. vinicolor & vesiculosus provide simple frameworks for studying CMNs because of their obligate specificity for P. menziesii hosts (Kretzer et al. 2000; Kretzer et al. 2003).

1) determine the spatial and genetic structure of CMNs formed between P. menziesii trees and Rhizopogon spp. ectomycorrhizas,
2) describe the architecture and connective potential of these networks,
3) contrast networks between dry and moist moisture regimes in the IDFdk subzone of southern interior British Columbia.
4) determine the spatial distribution of CMNs and how this affects natural regeneration patterns in the field.
5) conduct a field experiment to determine if CMNs contribute to kinship selection in P. menziesii seedlings
Related projects:  FSP_Y071314FSP_Y082314


Executive Summary (34Kb)

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Updated August 16, 2010 

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