This proposed PhD project examines the ecology of mycorrhizal associations in two contrasting coastal ecosystems, one dominated by western redcedar and the other by western hemlock, to understand how it influences seedling establishment of different tree species. It will contribute to the forestry regeneration project known as the Salal Cedar Hemlock Integrated Research Project (SCHIRP), which is addressing well-known regeneration problems of conifers on northern Vancouver Island (http://www.forestry.ubc.ca/schirp/homepage.html). One objective of SCHIRP is to identify factors and underlying ecological mechanisms differentiating Cedar-Hemlock (CH) and Hemlock-Amabilis fir (HA) ecosystems that influence the growth and nutrient acquisition of different regenerating conifer species (Prescott, 1996; Mallik & Prescott, 2001; Blevins & Prescott, 2002). A new objective, initiated by Western Forest Products, is to refine the biogeoclimatic ecological classification (BEC) system and associated ecosystem-based interpretations for improved forest management (McWilliams & Klinka, 2005; McWilliams et al., 2007).
Mycorrhizal associations between symbiotic fungi and tree roots are crucial for seedling nutrient uptake, survival and growth, and tree productivity in nutrient-limited environments (van der Heijden et al., 1998; Jonsson et al., 2001; Read & Perez-Moreno, 2003). Two dissimilar mycorrhizal associations we will study are arbuscular mycorrhizae (AM), which colonize western redcedar, and ectomycorrhizae (EM), which associate with western hemlock. AM and EM fungal species are biologically distinct, with AM fungi forming intra-cellular arbuscules and EM fungi forming an extra-cellular Hartig net, both serving as sites for nutrient-carbon exchange with the host tree. Cedar and hemlock have strict fidelity to its specific class (AM vs EM) of fungi (Molina et al. 1992), but potentially with considerable fungal species variability within each class. We hypothesize that the class of mycorrhizal inoculum present in the soil is governed by the dominant host tree species, such that CH sites dominated by cedar contain predominantly AM inoculum, whereas HA sites dominated by hemlock contain predominantly EM inoculum. Preliminary surveys suggest there is a strong correlation between dominance by AM or EM classes of fungi and the ability for cedar and hemlock seedlings to become established following harvest. On cedar-origin sites, for example, low EM inoculum potential would limit establishment of hemlock, matching field observations. Further study is required to confirm this hypothesis.
Our questions are:
1. Are there differences in AM and EM fungal communities or inoculum potential between CH and HA sites?
2. How does mycorrhizal inoculum of different ecosystems influence seedling establishment, survival, foliar nutrients and growth?
3. Can modifying mycorrhizal inoculum at the time of planting improve seedling establishment?
There are two parts to this project. The first part involves the molecular characterization of mycorrhizal fungal communities within adjacent CH and HA ecosystems of old growth, clear-cut and regenerating sites, and determining inoculum potential. This will enhance earlier work involving molecular characterization of EM fungi on hemlock saplings in fertilized and control sites at the SCHIRP study area, where it was discovered that legacy effects of fertilization on tree growth persisted for many years in the fungal community (Wright 2006). Here, we will augment this earlier research by expanding the fungal community characterization to old-growth and newly regenerating forests, and to include western redcedar as well as western hemlock. The second part of this project involves planting cedar and hemlock seedlings at each CH and HA clearcut site with (a) soil transferred from hemlock, and (b) soil transferred from cedar forests nearby. This study will be repeated in the greenhouse under a common garden environment
Shannon. 2011. Mycorrhizal fungi: unlocking its ecology and role for the establishment and growth performance of different conifer species in coastal ecosystems. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), British, Columbia
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