Forest Investment Account (FIA) - Forest Science Program
FIA Project Y081055

    SCHIRP: ecology and management of ericaceous shrub-dominated ecosystems in coastal BC
Project lead: van Niejenhuis, Annette (Western Forest Products Inc.)
Contributing Authors: Van Niejenhuis, Annette; Wright, Shannon H.A.; Berch, Shannon M.; Berbee, Mary L.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
SCHIRP was established in the 1980s to study poor conifer growth on sites dominated by ericaceous shrubs and to develop tools to improve conifer growth. The well-designed long-term trials allow investigation of current questions of biodiversity, ecosystem function, and carbon sequestration. SCHIRP trials were installed on CH (cedar-hemlock) and HA (hemlock-amabilis fir) sites on northern Vancouver Island (Lewis 1982). Both are zonal to wet, nutrient-poor sites in the CWHvm1 (Green and Klinka 1994), but CH sites are less productive than HA sites. CH and HA ecosystems were thought to be successional stages: a lack of windthrow disturbance causing HA forests to develop into CH forests with a resulting decline in nutrient availability (Lewis 1982). Tests of this theory showed little effect of soil mixing on nutrient availability or tree growth. Competition and allelopathic effects of salal were suspected to contribute to poor conifer growth on CH sites but salal removal has been less effective than fertilization at improving conifer growth. The theory that slow decay and nutrient immobilization contributes to low nutrient availability has also been refuted. While testing (and disproving) each of these theories, researchers made findings which indicate that CH sites are wetter than HA sites. This may be the primary cause of the low nutrient supply. These include greater frequency of gleyed horizons and hydromors in CH forests (deMontigny 1992), lower fauna abundance and biomass and larger population of copepods (Battigelli et al 1994), higher water content in CH forest floors, fast growth of shore pine (usually found in coastal bogs) on CH sites relative to other conifers (Bothwell et al 2001), and higher frequency of cedar (hence CH sites) near swamps and bogs. The theory that high soil moisture causes low nutrient supply on CH cutovers is being investigated using a combination of field measurements, lab incubations, a field trial and ecosystem modeling. Soil and vegetation characteristics of CH and HA forests and cutovers have been measured to assess if they are consistent with the hypothesis of excess moisture on CH sites, especially following harvest. Lab incubation of soil under a range of moisture conditions is currently assessing the effects on microbial activity and nutrient availability. A field drainage trial will be examined to determine if the characteristics associated with higher moisture on CH cutovers can be ameliorated by operational drainage. Finally, a hydrology stand-level simulation model, ForWaDy, will examine seasonal patterns of soil moisture and differences in hydrology between CH and HA forests and cutovers, and the forest ecosystem model FORECAST will assess the long-term effects of different moisture conditions on nutrient supply and productivity. The controlled, replicated Demonstration Trial plots offer an opportunity to evaluate the effects of fertilization on function and structure of microbial communities and on carbon sequestration. Plots logged in 1980 were fertilized in 1987 and 1997 with nitrogen (0, 100, 200, and 300 kg/ha) and phosphorus (0 and 100 kg/ha) and P with micronutrients for a total of 12 treatments. Fertilization changed the ectomycorrhizal community species composition but not diversity (Wright 2006). We sequenced ~1000 DNA fragments of 99 fungal species from control plots and from plots fertilized with 300 kg/ha N with or without 100 kg/ha P. We recorded the ectomycorrhizal fungi species that were associated with each of four sample trees from each plot and we observed that more litter and humus accumulated in the N + P plots than in the control or N plots. We will now test the theory that N or N + P fertilization increased accumulation and carbon sequestration in humus and soil organic matter, resulting in long-term carbon storage. We will compare soil C, microbial communities including ectomycorrhizal communities and their enzyme activities related to cycling of C and N in fertilized and unfertilized SCHIRP plots. We hypothesize that N-fertilized or N+P-fertilized plots are associated with less complete litter decay and larger accumulation of humus and soil organic matter compared to control plots, and that the effect will be more pronounced in the forest floor than at depth in soil. Humus and soil will be sampled in fertilized and control plots, and carbon stocks in the forest floor, soil, and root biomass will be determined and scaled up to a per ha basis. We will assess the composition of soil microbial communities in treated and control plots using established molecular methods for fungi and bacteria (Grayston et al 2004, 2006). Enzyme profiling will characterize functional diversity of soil microbial communities in terms of decomposition and nutrient cycling processes. This study will inform development of carbon indicators for certification schemes, and add to understanding of ecosystem function. Contributing to an understanding of the effects of forestry practices on non-target species, the mycorrhizae of mature CH and HA forests will be compared with those of the ~25-year-old trees of the Demonstration Trials. We will test the theory that one or more of the fertilization regimes increases the similarity of young mycorrhizal communities to the mycorrhizal community of mature forests. Studies conducted on clonal spruce showed that mycorrhizal communities of fast- and slow-growing trees differed (Korkama et al. 2006). Either the fungi responded differently to fast vs. slow growing trees, or tree growth responded differently depending on the ectomycorrhizal community. Our previous ectomycorrhizal studies at the Demonstration Trials raised the possibility which we would now like to test that tree performance was correlated with mycorrhizal species composition. We will compare mycorrhizal species of trees performing above average with species from trees performing below average of the same treatment regime. Our results will supply information about conditions under which microbial communities differ, a fundamental aspect of ecosystem function. Different ectomycorrhizal fungi may have different effects on tree growth response (Korkama et al 2006). We will isolate fungi and ectomycorrhizal root tips from fast- and slow-growing trees and use isolated fungi as inoculum for western hemlock seedlings, evaluating whether different ectomycorrhizal species have different effects on tree performance. We will maintain our long-term silvicultural field trials according to our treatment schedule. The Kennedy Lake trials will receive broadcast fertilizer applications of N and P as per the SCHIRP Field Guide, of 250 kg/ha and 100 kg/ha respectively. Team members and associated graduate students will publish findings to date and include the findings in course content in University programs. Four manuscripts will be submitted in 07-08, together with ~50 DNA sequences published to GenBank.
Related projects:  FSP_Y092055FSP_Y103055


Executive Summary (77Kb)
Abstract (22Kb)

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Updated August 16, 2010 

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