EP1204

Project Summary

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Project:

Occurrence of Armillaria species in site series of unmanaged, mature forests in subzones of the ICH biogeoclimatic zone in the Nelson Forest Region

Project Number:

EP1204; Transferred from MOF to CFS.

District(s):

Location:

Project Leader(s):

Duncan Morrison, Canadian Forest Service, Pacific Forestry Centre, Victoria

Contact:

Duncan Morrison
E-mail:	dmorrison@a1.pfc.forestry.ca
Phone:	(250) 363-0642

Introduction:

Armillaria ostoyae is one of the most economically important damging agents in forests in southern British Columbia, especially in the southern interior. While the fungus occurs in all biogeoclimatic zones in the southern interior, it is particularly damaging in the Interior Cedar Hemlock (ICH) zone. Harvesting and thinning of old - growth forests increases the incidence of Armillaria root diesease, and forest productivity may be reduced by as much as 30%.

Armillaria ostoyae is a common fungus in unmanaged forests in the south part of B.C.; in the ICH up to 90% of trees may have root infections, but show few or no above ground symptoms of infection. It appears to be a common component of ecosystem dynamics, facillitating tree succession, replacement of advanced succession tree species, such as hemlock, Douglas-fir, spruce by early succession tree species, mainly broadleafs. Two or three Armillaria species are normal components of forest ecosystems in the ICH biogeoclimatic zone. Armillaria sinapina, a saprophytic species, may have a role in reducing damage by the pathogenic A. ostoyae by competing for substrate.

Preliminary data suggests that the occurrence of Armillaria species in several subzones of the ICH is related to site series, i.e. soil moisture and nutrients (edatopic grid). Understanding the distribution of Armillaria species, the niches they occupy, the competition with other fungi, and the controlling factors of their distribution, could improve management of the disease.

Although the Armillaria literature is extensive, little information exists on the ecology and dynamics of Armillaria in unmanaged forests. Understanding ecological distribution and function of Armillaria species in unmanaged forest ecosystems is important for developing strategies for Armillaria root disease management in managed second growth forests.

Objectives:

To describe distribution of Armillaria spp. in mature forests in site series of several subzones of Interior Cedar Hemlock (ICH) zone and relate distribution to moisture and nutrient regime.
To assess possible roles of different Armillaria spp. in ecosystem dynamics in the ICH biogeoclimatic zone, such as in tree mortality, regeneration, succession, and nutrient cycling.
To propose potential ecosystem niches being occupied by different Armillaria spp., such as, where are Armillaria spp. distributed, in association with what other plant species, and how are Armillaria spp. affecting ecosystem processes?

Experimental Design:

Sampling Design:

The objective of this research is to collect baseline data on the function of Armillaria species in unmanaged forest ecosystems and to understand the interaction between the fungus and its hosts. The sampling design generally follows the concepts of analytical sampling as described by Eberhardt and Thomas (1991).

Sampling Rationale

Current sampling is focused on sites with extreme moisture and temperature regimes within the ICH zone because these are the areas where Armillaria ostoyae is most damaging.

Layout:
- In 1996, 1296 roots were examined for general health (alive-healthy or dead) and possible infection by Armillaria species (e.g. the presence of lesions, dead root tips or rhizomorphs). In addition, rhizomorphs were removed from the soil in 20 plots.
- Isolations were made from 692 roots and the 20 rhizomorphs resulting in a total of 3173 samples.
- Armillaria species were recovered from 136 roots and rhizomorphs and samples were identified to species using PCR/RFLP techniques developed at the Pacific Forestry Centre in Victoria (White et al. in press).

Major Findings:

Both Armillaria species were identified in all of the subzones sampled and from all but one of the sites surveyed in 1996. Armillaria ostoyae was found in the wetter variants of the dry subzones and in the dryer variants of the wet subzones. Conversely, A. sinapina was found in almost all subzones and variants.

Armillaria ostoyae was isolated most commonly from the dead roots of conifers (61%) or lesions on conifer roots (17%). Only 13% of A. ostoyae isolates were from rhizomorphs. By contrast Armillaria sinapina was isolated most commonly as rhizomorphs on roots (39%), or from the soil (21%). A further 27% of the isolates were from dead roots and 12% were isolated from small lesions (<10 mm in length).

Shrub species were rarely affected by A. ostoyae.

References and Publications (Click on Highlighted References to Obtain an Electronic Copy in PDF Form):

Eberhardt, L.L. and J.M. Thomas. 1991. Designing environmental field studies. Ecological Monographs 61(1): 53-73

White, E.E., C.P. Dubetz, M.G. Cruikshank, and D.J. Morrison. 1997. DNA diagnostics for Armillaria species: within and between species variation in the IGS 1 and IGS 2 isolates of British Columbia. Mycologia (in process).

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Acknowledgments:

Support for this project has been provided by the B.C. Ministry of Forests.