Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092108

    Does Fire Promote Regeneration and Growth of Western Redcedar?
Project lead: Negrave, Roderick (Ministry of Forests and Range)
Author: Korpela, Ed
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Western redcedar is a major commercial species on the British Columbia Coast and has substantial cultural value to First Nations. The presence of western redcedar on the Coast appears to be declining. Cedar has been preferentially targeted for logging. Decline and mortality of western redcedar has been observed on eastern Vancouver Island and the mid-Coast. Regeneration of western redcedar through silvicultural practices has been only partially successful due to ungulate browsing. Despite its importance, significant questions remain about the regeneration and development of cedar in Coastal stands. Our ability to retain western redcedar at the stand and landscape level in coastal BC will be enhanced if we can better understand the regeneration ecology of this species, which is ecologically, culturally and commercially pivotal.

The regeneration ecology of cedar is poorly understood, in general. There is no consensus on the role of disturbance on cedar regeneration and stand development. Western redcedar was long regarded as requiring disturbance to regenerate although is was very long-lived once established (Krajina 1969). Daniels (2003) suggests that cedar can regenerate through gap-phase and continuous modes of recruitment, suggesting an ability to regenerate independent of stand-replacing disturbance. Contradicting this, Weber et al. (2003) suggest that cedar needs disturbance and a high-light environment to regenerate, although once established it can survive and develop in low-light environments. The role of fire in cedar regeneration has not explicitly been examined in a coastal context but there are intriguing indications that fire may be significantly influence cedar regeneration. The proponent and others have noted that evidence of fire on the coast is more common than conventional thinking would suggest, although the source of these fires is often obscure e.g. evidence of past fire combined with abundant and vigorous pole-sized cedar regeneration commonly noted north and east of Bella Bella (Seaforth Channel, Yeo Island). Cedar regeneration is often associated with evidence of past fire, whereas it is often absent from areas where stands appear to have regenerated in the absence of fire e.g. the burned portion of an old A-frame block is stocked with a near-pure cedar stand but the unburned portion is dominated by western hemlock. It has also been suggested that, in the absence of fire, natural regeneration will favour hemlock and tend to replace cedar at the landscape level. The role of fire in cedar regeneration may be important given historic fire suppression, the declining presence of cedar and the possibility that global climate change will increase the incidence of fires on the coast. This project will add to our knowledge of western redcedar ecology by specifically attempting to answer the questions: 1) Is recruitment of cedar natural regeneration promoted by fire? 2) Is the growth of cedar natural regeneration promoted by fire?

A retrospective approach will be used where historic wildfires and prescribed burns are located, sampled for the occurrence and growth of western redcedar, and compared to comparable stands of a similar age that did not experience fire in the regeneration period. The goal is to sample 15 - 20 burned sites and an equal number of comparable non-burned sites. The project will be conducted over three years. Suitable stands will be located in the first year. Wildfire occurrence data bases from Protection Branch, MoFR, along with records and local knowledge from MoFR Forest Districts and local licensees will be used to locate a population of suitable sites from which sample sites will be selected. Sampling will likely focus on stands that are 45 years of age and less, due to the presence of more accurate records in this time period. Sampling stands at a younger age will also reduce some of the structural variability associated with stands of greater age and will more reflect current rather than historic climatic conditions. Sampling will occur in the second year. The focus of sampling will be to quantify site and stand factors for appropriate comparisons; amounts of natural regeneration, including relative and absolute amounts of cedar; and height growth of regeneration will be quantified. Analysis and reporting will be completed in the third year. The analysis will focus on comparing the amount of cedar regeneration of burned versus unburned areas and whether height growth of cedar is greater on burned areas. Key elements of the analysis will be to control for the effects of site and residual stand conditions e.g. trees that may have survived a disturbance, so that accurate comparisons may be make between burned and unburned areas.

The intention of this project is to better understand the basic regeneration ecology of western redcedar, as well as the role of fire in stand development and growth on the BC Coast. This information will better position us to manage forests for the continued presence of cedar and to understand possible effects of increased fire occurrence associated with global climate change. The ultimate goal is to better guide management of the cedar resource by determining if fire enhances cedar regeneration and growth. This basic information may then be applied to management at the stand and landscape level. The project will be conducted in the traditional territories of a number of First Nations located on western and northern Vancouver Island. It is felt that this work will be of significant interest to First Nations, given the cultural value of western redcedar and the emerging First Nation interest in commercial logging.
Related projects:  FSP_Y081108FSP_Y103108

Executive summary (54Kb)

Updated August 16, 2010 

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