Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092240

    Sustainable management of the ponderosa pine parkland ecosystems in the Thompson River watershed after the mountain pine beetle epidemic
Project lead: Vyse, Alan (Thompson Rivers University)
Contributing Authors: Klenner, Walt; Arsenault, Andre; Vyse, Alan
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
The current mountain pine beetle is having a severe impact on the ponderosa pine (Pinus ponderosae Dougl. Ex Lawson. var. ponderosae) stands of the southern interior. In the Thompson River drainage, for example, mortality levels of 90% in pine parkland stands has ben reached by 2006. Within the boundaries of the City of Kamloops, city staff have estimated that 75% of the mature pines have been lost. Further mortality took place in 2007. Drought in 1998 and 2003 also caused extensive mortality, especially in young stands on the forest/grassland edge, and may have contributed to the beetle mortality.

Extensive mortality from pine beetle epidemics is not new in North America or B.C. Oliver and Ryker (1990) cite evidence of large scale outbreaks in the Black Hills of Dakota at the turn of 19th century and other outbreaks on the front ranges of the Rockies. In BC, Mulholland (1937) reported on the widespread loss of mature pine as a result of an epidemic in the mature yellow pine stands throughout its range ion the province. Richmond (1982) provides details of an epidemic in the Nicola River watershed, which ended in 1935.

Although ponderosa pine stands do not have a high timber value at this time and no active forest management has taken place for decades, this was not always the case. In the early part of the last century, overgrazing was common, and ponderosa pine (variously called yellow, bull and jack pine) was intensively exploited for many uses, including railway ties, construction lumber, and boxes for the fruit industry. Whitford and Craig (1918) report on extensive and heavy use of the ponderosa pine stands in the province and this continued into the 1930’s (Arsenault et al. 2001). In the 1950’s the B.C. Forest Service issued a Stand Management Guide (B.C. Forest Service undated) which detailed stand treatments for the yellow pine forest type. Since then however there has been little timber management action.

Grazing has been widespread in the ponderosa pine forest for 150 years and continues to the present although at a diminished level. Today the stands have high value for recreation, whether active, in the case of mountain bike riding and hiking, or passive, as part of the backdrop to urban areas and recreational properties in the Thompson River system. The stands also have high ecological value as habitat for an unusual assemblage of dry forest and grassland species, including several species at risk, and this value is increasing as the habitat dwindles under pressure for urban, agricultural and recreational developments.
Mature stands of Ponderosa Pine provide breeding habitat for a broad community of bird and animal species. Three key groups—nuthatches, woodpeckers, and diurnal owls—constitute primary and secondary cavity nesters that rely to a greater or lesser extent on the forest type : Pygmy Nuthatches, Pygmy Owls, and Lewis’ Woodpeckers. The nuthatch is of particular interest because of its reliance on Py during all seasons for nesting cavities, an over-winter food supply, and winter roosting cavities.

The current beetle epidemic in the ponderosa pine stands (which involves Dendroctonus ponderosae primarily but also includes significant attacks by Dendroctonus brevicomis and Dendroctonus valens) is creating a great deal of uncertainty about future management. With the high level of mortality, major changes in the ponderosa pine ecosystem are inevitable. From the information available at present it is not clear if the ecosystem will return to forest, or revert to grassland, if no management takes place. The current policy of “no management” is no longer valid. Pressures for active management are growing, with initial efforts taking place on a small scale, focused on fuel management adjacent to urban areas, and forest encroachment. There is also concern over species at risk and non-native species invasions, especially in the Provincial and Municipal parks, and these concerns may conflict with suggested management interventions. A wide range of questions are being asked but there is a very limited scientific foundation for providing answers. Much of the information available comes from the US Forest Service publications (Baumgartner and Lotan 1988; Oliver and Ryker 1990) which deal with ponderosa pine ecosystems far to the south.

Some authors have suggested that these forests are “fire maintained” and that a combination of fire suppression and a lack of management action to counter the effects of fire suppression have led to unsustainable stand structures and away from the dynamic equilibrium maintained by frequent fires (BC Ministries of Forests and Environment 1995). Based largely on forest fire history studies in the ponderosa pine forests of the American Southwest, the supposed sustainable structure is characterized by extensive areas with low crown closure, widely spaced large trees, lush grass understory, and few tree seedlings or woody shrubs. Fire suppression is claimed to have changed the forest structure of local stands by increasing the density of small stems, and changing species composition as it has done in the South west (Covington and Moore 1994; Moore et al. 1999). Tree invasion of grassland (Strang and Parminter 1980), increased fuel loading leading to more extreme fire events, and pest outbreaks have also been attributed to the management failure to maintain this structure. Arsenault and Klenner (2005) present an alternative view of a mixed severity, non-equilibrium fire regime in the dry forests of British Columbia. They state that: “historical conditions like today were quite variable and therefore choosing a reference condition for ‘ecological restoration’ is virtually impossible. p.14.”

Our project will supply a foundation for understanding the short and long term ecological impact of the mountain pine beetle on the current ponderosa parkland stands, the disturbance history in these stands, and stand or stand structures that might be the focus of future sustainable management. We are concentrating on easily measured ecosystem variables such as tree mortality, stand structure, regeneration, snags, coarse woody debris, presence and abundance of key bird species, ground vegetation including non native species and easily assessed invertebrate species (ants, grasshoppers and butterflies). Long term plots have established for future monitoring in stands with heavy mortality in area around Kamloops. We found no stands with low mortality, so we have established long term plots in the South Okanagan where MPB mortality is low, using existing bird population transects. Expansion to the East Kootenay ponderosa pine stands is planned in 2008.

First Nations use of the plants in these forests has been extensively researched (Turner et al. 1990) but their views of the effect of the beetle epidemic and its effect on their interests have not been explored and recorded. Work on this component of the project will begin in 2007 and expand in 2008.

Related projects:  FSP_Y081240FSP_Y103240


Journal article on Ponderosa pine mortality (0.5Mb)
Executive summary (0.6Mb)
Sisco Poster (0.2Mb)

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Updated August 16, 2010 

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