Forest health

Forest health research investigates the impacts of a wide range of forest health factors including bark beetles, defoliators, pathogens and abiotic damage. It is also account for and  integrating the effects of invasive species and climate change.

Rhinusa linariae Effect on Yellow Toadflax (Linaria vulgaris) on Nickel Plate Mountain, British Columbia - TR145

Invasive yellow toadflax (Linaria vulgaris (L.) P. Mill.) was introduced in British Columbia and has spread across the province; as of 2021, it has been recorded at 2058 locations in a range of habitats. Biological control agents are being used to reduce the abundance and slow the spread of yellow toadflax, but they will not eradicate it. Three federally permitted biological control agents have been released in the province to control this invasive plant. One agent, Rhinusa linariae Panzer, Curculionidae, a weevil, is suspected of being particularly effective. At a site on Nickel Plate Mountain (1710 m elevation), the weevil appears to have significantly reduced the frequency of occurrence of yellow toadflax within the plant community by 90.3% in 8 years. R. linariae density increased to 32 weevils per square metre or 0.96 weevils per plant before it rapidly declined in synchrony with its host plant to 4.7 weevils per square metre or 1.3 weevils per plant as weevils crowded into the remaining yellow toadflax plants.

Developing a Tool for the Early Detection of Drought-induced Forest Stress and Mortality in British Columbia - TR141

We tested components of a drought mortality decision tool for application in British Columbia forests. The previously estimated drought thresholds for lodgepole pine and western larch were tested and revised based on the field assessment of visible foliar drought indicators in relation to estimated soil moisture regimes using the ratio of actual evapotranspiration to potential evapotranspiration (AET/PET). Post-processed photography from drones flown over sites with known drought mortality was very successful at mapping dead trees. Using a supervised image classification, dead trees identified in the field were composed of 75% pixels identified as dead. Only 1% of the dead trees were composed of >50% live pixels based on image classification. In combination, the drought assessment tool using AET/PET estimates, along with image-mapping tools, should be effective at identifying and preparing treatment maps for forests impacted by drought. Furthermore, these tools have the potential to map drought risk, allowing appropriate management planning.

Longitarsus jacobaeae Swiss Biotype Effect on Tansy Ragwort (Senecio jacobaea) in Naramata, British Columbia - TR140

The flea beetle, Longitarsus jacobaeae (Swiss biotype), exhibited a classical biological control pattern on its host plant tansy ragwort (Senecio jacobaea L.) in Naramata, B.C. by rapidly increasing in number after its release and causing the decline of the plant. L. jacobaeae’s presence was identified by approximately 1.6-mm2 feeding holes in the ragwort’s leaves. L. jacobaeae fed preferentially on rosettes (p=0.0333) as opposed to bolted plants (p=0.4621). It caused a visibly significant decrease in the number of rosettes and bolted plants combined at the trial sites in 3–4 years (p=0.0221). From the point of release, L. jacobaeae dispersed 100 m over the study site in 4 years.

Survival of the Biological Control Agent Rhinocyllus conicus on Marsh Thistle (Cirsium palustre) in British Columbia - TR136

The seed-feeding weevil Rhinocyllus conicus (Froel.) was screened and later introduced into Canada to control the invasive nodding thistle (Carduus nutans). The weevil is also known to attack thistles in the Cirsium genus. A study was conducted in British Columbia to confirm whether the weevil’s lack of establishment and population growth on marsh thistle (Cirsium palustre (L.) Scop.) was because the thistle was a poor host or its local habitat was unsuitable for the control agent. Weevils were released at 10 sites over a 4-year period. The existence of individual weevils at different life stages was investigated. No failing was found at any life stage, which indicated that marsh thistle was an adequate host plant for the weevil. The weevil’s spread from the point of release and its preferences for solar radiation as influenced by slope and aspect were documented. Additionally, although the numbers of weevils released annually had declined, the numbers marginally increased in some instances, potentially indicating acclimation to the site and population growth.

Trichosirocalus horridus Effect on Nodding Thistle (Carduus nutans) - TR135

The root-crown feeding weevil Trichosirocalus horridus (Panzer) exhibited a classical biological control pattern on its host plant, nodding thistle (Carduus nutans L.), by increasing in number after its release, causing an effect on its host, and decreasing in number with the decline of the plant. T. horridus did not readily spread from its points of release, and thereby concentrated its feeding. Nodding thistle rosette diameters decreased by 38%, bolted plant densities decreased approximately 50%, stem numbers increased 5-fold, while stem heights showed a gradual decline. The additional biocontrol agent on-site, Rhinocyllus conicus, contributed to the attack on the nodding thistle.

Elytroderma needle cast on lodgepole pine in British Columbia - LMH74

Elytroderma needle cast, caused by the fungus Elytroderma deformans, is a foliage disease that affects lodgepole pine (Pinus contorta var. latifolia) and ponderosa pine (Pinus ponderosa) in British Columbia. Most of the literature on Elytroderma needle cast refers to the disease on ponderosa pine. It is not known if there are host-specific subspecies of Elytroderma, but many of the signs and symptoms of the diseases are similar on both pine species. Elytroderma needle cast is fairly easy to recognize on ponderosa pine because it causes large brooms. In contrast, Elytroderma on lodgepole pine often goes unrecognized or is confused with Lophodermella concolor (another common needle cast) or lodgepole pine dwarf mistletoe (Arceuthobium americanum).

Dwarf Mistletoe Management in British Columbia - LMH73

Dwarf mistletoes are parasitic seed plants that require living hosts to survive. They are a natural and important part of many forest ecosystems. From a timber management perspective, dwarf mistletoes can increase tree mortality and reduce tree growth and wood quality. Forest practices play an important role in determining the extent of these negative effects in managed stands. Removal of susceptible host trees through harvesting and eradication of susceptible natural regeneration is the best way to reduce future losses from dwarf mistletoes. Partial harvesting should be avoided in areas with high levels of dwarf mistletoe. However, where partial harvesting is required to meet other resource management objectives, specific measures to reduce future effects from dwarf mistletoes can still be implemented. Possible effects of climate change on dwarf mistletoe are also discussed in this report.

Polypores of British Columbia (Fungi: Basidiomycota) - TR104

Nearly 200 species of polypores (Fungi: Basidiomycota) are accepted as part of the mycoflora of British Columbia, Canada. The lifestyle of the pathogenic polypores causes significant loss of timber value, especially in old-growth stands. The killing of trees affects species composition, stand density and structure, and the direction and rate of forest succession. Most polypores are saprobes and play a highly beneficial role by contributing to nutrient recycling through the decay of woody debris in forests. The rotted debris promotes growth of tree seedlings and other plants and increases the biodiversity of the forests. A main purpose of this report is to ease the identification of polypore specimens through a step-by-step reduction of the number of probable names for an unnamed collection. This is accomplished in three ways. First, several series of comprehensive keys lead the user to names of genera and species. Next, the user compares their unnamed specimen with colour photographs of the basidiomata. Finally, the user confirms the identification with a detailed account of each genus or species that includes its known habitats and geographical distribution. The description emphasizes features of fresh basidiomata, such as condition, colour, and size, and also notes critical microscopic characters.

Managing Ingrown Douglas-fir Stands for Biodiversity, Forage, and Timber: The Farwell Canyon Project Fifth-year Post-treatment Results - TR47

The Farwell Canyon project was established to explore treatment options for enhancing undergrowth vegetation cover, forage production, and tree growth in densely ingrown Douglas-fir stands of the Interior Douglas-fir very dry mild (IDFxm) biogeoclimatic subzone. Fire scar and tree age analyses along with stand structure observations suggest that many of these ingrown stands were considerably more open before European settlement. Stem reduction treatments applied to two ingrown sites in 2001 included logging only (L), logging plus juvenile thinning (LT), and logging plus thinning plus underburning (LTB). No-treatment (NT) areas were also established. The logging treatment was modified from standard practices to harvest small merchantable stems and to initiate thinning of juvenile stems. The objective of this report is to compare third- and fifth-year (2003 vs. 2006) vegetation composition, forage production, and tree regeneration responses to these treatments on one site. Douglas-fir regeneration density increased in all treatments between 2003 and 2006. Cover of grasses increased substantially, due primarily to increased cover of pinegrass (Calamagrostis rubescens). The number of plots with bunchgrasses increased even though mean cover of bunchgrasses did not increase significantly. Shrub and forb cover remained generally low on all treatments. Biomass of combined forbs and graminoids increased significantly from 2003 to 2006 but did not differ significantly among treatments.

Forest Stewardship in the Context of Large-scale Salvage Operations: An Interpretation Paper - TR19

All indications are that the current mountain pine beetle outbreak will have a significant impact on a large proportion of the pine forests in British Columbia (Eng et al. 2004). It is neither desirable nor possible to harvest all of the affected pine forests. Nonetheless, any increases beyond current harvest levels must carefully consider all forest values. This document provides recommendations to the Chief Forester about the conservation of all forest values during large-scale salvage operations:
- At the landscape level, there should be little, to no, salvage harvesting in the noncontributing land base and, at the very least, what was originally planned under existing landscape-level plans should be left .
- At the stand level, there should be no changes to the provisions made for riparian management areas and riparian reserve zones. As well, there should be no changes to the management of wildlife tree patches, wildlife habitat areas, and other fine-filter measures. Legacies of coarse woody debris should be left throughout the blocks.
- To the extent possible, the area chosen for salvage should have the highest level of infestation and the highest proportion of pine.
- The creation of large openings (> 1000 hectares) will be appropriate; however, the legacies of unharvested areas within the openings should increase in proportion to the increasing size of the opening (up to 25% in the case of 1000-hectare openings).
Other related recommendations are made about access structures, adverse effects on peak flows and soil erosion, silviculture that might lessen future problems with mountain pine beetle outbreaks, fire risk at the wildland-urban interface, and monitoring programs.

Measuring Light in the Forest - EN42

PPFD levels in the understorey of a forest vary both temporally (i.e., during the day, and during the year) and spatially. Because of the large spatial variability in light levels in the forest understorey, it is desirable to obtain large numbers of samples either by installing a number of fixed sensors or by moving one or more sensors to several locations in the stand to characterize average light conditions. When studying growth responses of single trees or vegetation in small plots, it is generally desirable to obtain measurements at specific points (i.e., above the seedling or at the centre of the measurement plot). Several direct and indirect methods are available for measuring light in the forest understorey. Direct methods include: fixed light sensors, handheld light sensors, plant canopy analyzers, and fisheye (hemispherical) photographs. Indirect techniques include the use of correlations between transmittance and canopy cover, stand basal area, gap fraction, or other stand parameters, and the use of computer models.

Ultraviolet-B Risks to British Columbia Trees - EN35

Earth's natural ozone layer in the upper atmosphere is under attack from synthetic chemicals. These include chlorofluorocarbons (CFCs), which were used widely before 1987 when the Montreal Protocol outlawed their manufacture. Before this ban, thousands of tonnes of CFCs entered the atmosphere from air conditioners and refrigerators. CFCs may persist for years before breaking down, and each chlorine atom in CFCs can destroy many thousand ozone (O 3 ) molecules.Near the ground, ozone is often part of urban smog, but ozone in the stratosphere benefits living things below. Its absorption spectrum has a peak in the UV-B wavelengths emitted by the sun, so most UV-B never reaches ground level (Figure 1). More than a billion years ago, earth's atmosphere grew rich in oxygen and the ozone layer appeared. Since then life has evolved under a UV-B shadow. Recent increases in UV-B levels may have many consequences for living things. UV-B, twice as energetic as visible red light, can alter DNA, destroy proteins, bleach pigments, and cause tissue burns.

Field Guide to the Biological Control of Weeds in British Columbia - LMH27

The biological control of weeds typically involves the local establishment of host-specific organisms from other parts of the world to give continuing control of weeds. Weeds reduce floral diversity and the capacity of land to support wildlife, livestock, trees, and recreational activities. The biological control of weeds has a long history as an economically sound and environmentally friendly method of controlling widespread introduced weeds on uncultivated land. In Canada the biological control of weeds began in British Columbia in 1952 with the release of the defoliating beetles Chrysolina quadrigemina and C. hyperici to control St. John's wort. Although initial results of that trial were disappointing, within 13 years of the release the beetle populations had increased sufficiently to control the weed in most areas of the province, eliminating the need for chemical control of this species. From these early beginnings, biological control of weeds has expanded to most provinces of Canada, and the program now uses more than 50 insects and pathogens on more than 20 different introduced weed species. This guide is designed to help resource managers in British Columbia identify weeds and select suitable biological control agents for those weeds. Biological control offers stable, long-term solutions to weed problems across the province.