Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092267

    Extension - Options for the landscape-level management of dry NDT4 ecosystems in the Southern Interior Forest Region
Project lead: Klenner, Walt (Ministry of Forests and Range)
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
In western North America, forests of Ponderosa pine or Douglas-fir as pure stands or mixtures with other species such as larch, grand fir or lodgepole pine are widespread from Mexico to southern British Columbia. Over the past 50 years, numerous reports have examined and debated the role of fire and fire suppression in these ecosystems (Leopold 1924, Cooper 1960, 1961, Covington and Moore 1994). In the last decade, there has been an increasing concern regarding the shortcomings associated with current fire suppression activities (Daigle 1996, Gayton 1996), and this is being reflected in local Land and Resource Management Planning documents (e.g. see drafts of the Okanagan-Shuswap and Lillooet LRMP). These documents accept the hypothesis that frequent, low severity fires were in recent history the main disturbance agent in dry forests and grasslands, and that fire suppression has led to unnatural and “unhealthy” forest conditions.

There is little doubt that low severity fires were common in many areas dominated by coniferous forests in western North America (Agee 1993), with some of the strongest evidence for frequent low severity fires from the dry Ponderosa pine forests in the southwestern United States (e.g. Covington and Sackett 1989). However, there is mounting evidence that supports the concept of a mixed severity fire regime, especially on more mesic sites and at northern latitudes (Shinneman and Baker 1997, Veblen et al. 2000, Noss et al. 2006) with fire effects ranging from low to high severity in a complex mosaic within a single fire and across the landscape. For example, Wong (1999) found evidence to support the mixed-severity model in her study in the Stein Valley in southern British Columbia. Her work on the age structure of stands suggests only about 25% of the fires in her study area were low severity underburns. Shinneman and Baker (1997) also reported a mosaic of forest types in the Ponderosa pine forests in the Black Hills of South Dakota. Xeric sites had more open stands that would reflect periodic low severity fires, while mesic sites in valleys and northerly aspects often supported old forests in dense stands that likely arose from stand replacing fires. Similarly, studies by Taylor and Skinner (1998) in northern California report similar evidence for a mixed severity fire regime in some areas of dry conifer forests. These results, coupled with the diverse habitats encompassed by the NDT4 designation and the complex topography in BC suggests that the frequent low severity fire disturbance hypothesis should be carefully examined prior to initiating costly programs to “restore” ecosystems.

The project involves work to update and complete a review of the published literature on the management of dry forest ecosystems, some of which are the focus of extensive restoration initiatives (e.g. see Blueprint for Action, Rocky Mountain Trench Ecosystem Restoration Steering Committee 2006; ). Previous work by Klenner et al. (2001, “A strategy for managing dry-belt ecosystems of the Kamloops Forest Region”, see prepared an extensive draft review of the literature relating to likely historic natural disturbances, and the likely consequences of implementing different management strategies. Historic photographs and accounts, an analysis of lightning and weather data, and fire scar analyses suggested a mixed severity fire regime, along with episodes of widespread and intensive insect attack likely shaped many of the dry forest ecosystems in the Southern Interior. Current interest in manipulating forest structure in the context of ecosystem restoration, the current widespread mortality of Ponderosa pine across extensive areas resulting from mountain pine beetle (Dendroctonus ponderosae) and western pine beetle (Dendroctonus brevicomis) attack, and recent perspectives on fuel management (Filmon 2004, Forest Practices Board 2006) indicate a thorough synthesis of dry forest management issues needs to be undertaken to ensure there is an appropriate trade-off between ecological and socio-economic values. Restoration initiatives often cite departures from the historic frequent low severity fire regime as a key driver, but recent analyses (Klenner et al. 2001, Arsenault and Klenner 2004) suggest many of the dry forests in southern BC were more likely shaped by a mixed severity fire regime. Noss et al. (2006) come to a similar conclusion about many of the drier forests in the western United States, suggesting a cautious approach be taken before extensive and intensive “restoration” initiatives are undertaken. For example, the current widespread insect-related mortality in Ponderosa pine dominated forests may diminish the need for initiatives to create “open” forest conditions, and concerns about fuel management may need to become more strategic as the extent of the wildland-urban interface continues to expand in many jurisdictions (Dombeck et al 2004). Placing current dry forest conditions in BC in the longer-term context provided by a comprehensive literature review, recent new information on fire histories, an analysis of weather and lightning patterns, and recent new information on the likely extent of insect attack and mortality (e.g. tussock moth in low elevation Douglas-fir stands in the 1970’s) will provide a clearer technical understanding of historic disturbances to frame discussions about social, economic and ecologic management initiatives.

We will use an extensive literature review with an emphasis on publications since 2000, further and more focused analyses of data acquired since 2001 and dialogue with operational staff and planners to develop a peer reviewed publication and an extension note in the Southern Interior Forest Region Extension Note series. We will review the literature on natural disturbances, forest fuel management, wildlife habitat and biodiversity, historic insect attack and fire regimes, and the effects of stand density on timber and understory productivity to prepare a template that illustrates the kind of attributes and their dispersion in space and time that management practices should attempt to emulate. Recommendations will be developed for the implementation of landscape planning approaches to help ensure that management practices play an active role in maintaining dry forest conditions in a manner that balances a wide range of values.
Related projects:  FSP_Y081267

Executive summary (100Kb)

Updated August 16, 2010 

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