Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092147

    Structural recovery in second-growth forests on Lyell Island, Haida Gwaii
Project lead: Pearson, Audrey (Ecologia)
Author: Pearson, Audrey F.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
The purpose of this project is to provide baseline data on second-growth structural and compositional recovery for both tree and understorey species (defined as ecosystem recovery) in riparian and upland forests. We have do not have a good understanding of the habitat potential of second-growth forests, including riparian forests, or reference data for determining targets for restoring structural complexity and compositional diversity associated with the original old-growth forests in second-growth forests. Many of our riparian areas in coastal BC are second-growth because those forests had the most accessible, highest volumes of timber and were logged first. However, these are also the most productive forest sites so the greatest potential for ecosystem recovery, especially since they are often our oldest second-growth. The Millennium Ecosystem Assessment, an analysis of the state of the world’s ecosystems, concluded there were virtually no environmental baseline data - essential for accurately assessing conditions and trends in biodiversity over time. In order to determine the effectiveness of stand-level attributes for maintaining biodiversity, we need such baseline data on stand-level attributes to develop targets and management guidelines.

Lyell Island (Gwaii Haanas National Park Reserve) is an ideal location for such an investigation. There is a range of seral stages (both logging dates and methods), the area will never be logged again (so can provide a long term baseline) and is being managed solely for biodiversity values. Further, many historical data sources have already been compiled. The original forest composition and riparian zone (based on terrain units) have already been reconstructed from historical sources (1937 air photos and 1966 forest cover maps) (Pearson and Gergel 2006), so landscape-level data on reference conditions already exists to which the second growth information can be linked. There are also 1966 cruise data and ecosystem plot data from the 1970s/1980s to further verify the characteristics of the original old-growth stand, including understorey species. In addition, there are old-growth structure and composition plots and gap transects from a previous wind disturbance study that can serve as a comparative baseline (Pearson et al. 2005) and second-growth growth and yield plots that were established in 1962. Finally, a stream restoration project is already underway with Haida Fisheries, Parks Canada and other agencies where the riparian forest information can be directly applied.

Based on this past summer’s field season, our experimental design was successful. Using the air photo record, logged areas were delineated into three classes: early logging (pre-1937), logging 1937 – 1966, logging 1966 – 1987, stratified into riparian and upland areas. Second-growth forest structure and composition were determined from forest structure plots and gap transects following standard techniques (See experimental design and methods.) The characteristics of the original stand will be determined from the original forest composition derived from the 1937 air photos and 1966 forest cover maps, abundance and species composition of stumps and logs remaining on the ground, air photo interpretation and historical data sources (such as old-growth plot data). The accuracy of the reconstruction will be tested against old-growth information for Windy Bay, which was never logged, so can serve as test of differences between old-growth attributes on the 1937 photos and modern photos/field verification. These analyses will be conducted over the winter and be reported in the March 31 2008 report as well as form the basis of the first manuscript.

The key forest management issues addressed by this project are forest structural and compositional recovery following logging, in both upland and riparian forests. Our questions and analyses are thus focused on differences in forest structure and composition with different eras of logging. The first year of this project was focused on groundtruthing the original forest cover and gathering broad-scale stand-structure/composition data (including densities of conifers versus alder in the riparian zone) to determine general patterns. In our second year, we will focus on further substantiating our initial results and gathering more second-growth stand-structure/composition data for sufficient sampling intensity, including encompassing the variability we have observed. Our initial hypotheses were correct. Not only is western redcedar successfully regenerating in areas logged before 1937, but also on sites logged between 1937 and 1966. We need more details on cedar density, age and site characteristics. Vaccinium and other understorey species are present on stumps in old second-growth, but absent on the forest floor. This regeneration success is due in part to the fact that stumps were cut higher in early logging than in modern clearcuts so the understorey species are further out of reach of deer. Site that were A-frame logged have more residual structure than modern clearcuts, but the pattern is inconsistent. On some of the earliest sites (logged before 1937), wood was cut and left, whereas on sites logged between 1937 and 1966, residual trees were left standing and there is very little large coarse woody debris. We will focus our analyses towards answering our original questions, including with data from the second year’s field season. What is the live and dead wood legacy (sizes, species, decay classes of logs and snags) in second-growth forests? To what extent can second growth provide habitat values (using forest structure variables as a surrogate for habitat)? How do those habitat values change over time (using logging date as a time variable)? How can we best accelerate structural and compositional recovery in second-growth forests, especially riparian forests?

This project will contribute to an ongoing research effort on ecosystem recovery in second-growth coastal forests of both field investigations and modelling. This project will link with a riparian restoration project in Kennedy Flats (Clayoquot Sound) as well as simulation modelling of forest succession under different management scenarios, including restoration (LLEMS). E.g. How does structural and compositional recovery (especially of understorey species) in Haida Gwaii compare with that of other second-growth coastal forests where introduced deer are not a factor, such as the Kennedy Flats and the Mid-Coast? This project will also contribute data to an ongoing study of conversion of old-growth cedar to second-growth spruce/hemlock forests from introduced deer. All these projects will contribute to a broader understanding of second-growth recovery, including recovery of habitat values and development of the best techniques for restoring structural complexity and compositional diversity in second-growth forests in order to maintain biodiversity.

The benefits of this project to the Haida Nation are detailed in the previous section.
Related projects:  FSP_Y081147


Executive summary (27Kb)

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Updated August 16, 2010 

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