Current Research & Graduate Students

   Outbreak dynamics and spatial relationship between western spruce budworm and Douglas-fir beetle in the northern Chilcotin region

Neil Thompson, PhD Candidate
Douglas-fir beetle (DFB) is a native insect that infests Douglas-fir throughout much of its range in Canada, the United States, and Mexico. Douglas-fir and DFB reach their Neil Thompson coring a treenorthernmost distributions in central British Columbia, providing a unique opportunity to study the ecology of the host/pest system. Douglas-fir beetle preferentially attacks trees that have been weakened by drought, fire, windthrow, root rot, competition, or, it has been suggested, defoliation by western spruce budworm (WSB). The objective of this study is to describe and quantify historic outbreaks of Douglas-fir beetle and the interactions between DFB infestation and predisposing factors including WSB defoliation. Periods of growth suppression, release events, and scars left by failed beetle attacks are being identified in a 250-year tree ring record. These reconstructions will be used to quantify and explain changes in outbreak dynamics of both DFB and WSB over time, and project future impacts and potential mitigation strategies.

Impact of climate change-fire regime interactions on lichen succession in the wintering range of the Bathurst  Caribou Herd, NWT

The barren ground caribou (Rangifer Tarandus groenlandicus), a native wildlife species in Arctic Canada, has immense socio-cultural and economic significance to many of the inhabitants of the boreal and tundra transition woodlands of the northern ecosystem. However, the caribou population has sharply declined in last couple of decades. Ground-based lichens are the most common food for caribou in this northern ecosystem. The study will reconstruct fire history using tree ring analysis and remote sensing, which in conjunction with the existing fire database will enable comparison of the historic fire regime with current regime. The study will also explore the relationship between fire frequency and lichen succession. Lichen abundance of the boreal forest in northern ecosystem is mainly dependent on fire regimes. Longer fire-free interval favors lichens by controlling dominant competitors such as shrubs, herbs and mosses.
 

Genotypic and phenotypic diversity in Geocaulon lividum and the development of disease caused by Cronartium comandra

MSc Student, Theresa McMurchy 
Comandra blister rust (caused by the fungal pathogen Cronartium comandra), or CBR, is a disease that affects pine throughout British Columbia’s forest ecosystems, and isGeocaulon lividum considered a significant threat to timber supply in BC.  In addition to the economic impacts of this disease, CBR contributes to the decrease in habitat and ecosystem quality through the degradation of lodgepole pine stands, which are currently under attack on a much larger scale due to the current mountain pine beetle infestation in British Columbia. Comandra Blister Rust is considered the most lethal of all native rust pathogens, and unlike the mountain pine beetle, C. comandra most commonly attacks young lodgepole pines, although mature trees are also affected by Cronartium comandra. Though the effects of C. comandra are most evident in pine, the fungus requires an alternate host in order to complete its life cycle and reproduce.  Geocaulon lividum, a member of the Sandalwood (Santalaceae) family, is commonly known as Bastard toadflax, or False toadflax, and is synonymous with Comandra lividum. This small herbaceous plant is the alternate host that Cronartium comandra requires to proliferate. The life cycle of Comandra Blister Rust is well documented, and much is known about how the pathogen spreads, from G. lividum, to lodgepole pine, and back to G. lividum again. The relationship between the anamorph of C. comandra and the pine host is relatively well understood, but few studies have examined the interactions between the teleomorph and its semi-parasitic host plant Geocaulon lividum, despite the importance of this stage in disease epidemiology and damage to lodgepole pine stands. Effective management of CBR requires knowledge of population dynamics of the host plants. To date, little is known about the G. lividum – C. comandra partnership. The overall purpose of this research is to quantify phenotypic and genotypic variability of G. lividum, and to determine if this variation affects the pathogen population. Important questions include: 1) What is the genotypic diversity of Geocaulon lividum as identified using molecular methods, and are there any phenological indicators of genotypic diversity? 2) What is the variation among Geocaulon clones in terms of age, growth, range, and susceptibility to the CBR fungus? 3) How does the fungus vary within and among different sites with respect to timing of production of teliospores and uredinospores?  4) What is the variation in climate between study sites, and how does it relate to spore dynamics and variation in phenotype between communities of G. lividum?  

Sensitivity of western redcedar to climate variables, and the relationship between climate and past outbreaks of western hemlock looper in the Interior Cedar Hemlock zone.

MSc Student, Chris Konchalski
The northern extent of the Inland temperate rainforest (ITR) is predicted to undergo some of the most significant ecosystem change as a function of climate change, yet littlewestern redcedar cross section is known of the existing ecological processes that have enabled maintenance of the ITR over the past centuries. Cedar is one of the most dominant species in the ITR, and it is what makes the ITR so unique. Very little is known about inland western redcedar with regard to variability in growth response to climate.  Recent research on ITR stands suggests that snowmelt in upslope positions which normally have a high snowpack level, buffers ITR stands, especially western redcedar, from climate variation, but little is known regarding sensitivity of cedar to specific climate variables.    Disturbance history in the ITR is also not well understood. The oldest cedar in the ITR may be the first colonizers and together with hemlock became established in the area only 2000 years ago. Time between major disturbance events (e.g. fire) is thought to be greater than 500 years and the cool, moist conditions of the ITR may be more conducive to periodic disturbance by biotic agents, rather than disturbance caused by fire. An analysis of historic (1911 to 1994) western hemlock looper outbreaks in the Upper Fraser region of the ITR and found 2 major outbreaks in the 1950s and 1990s, with the latter leading to severe damage and mortality of conifer species in the ITR.   This study will examine the following working hypotheses:  1. Radial growth of Thuja plicata varies with climate and is more sensitive to climate variables at upper slope positions than at toe slopes.  2. Radial growth of cedar varies significantly with snowpack levels. 3. Effects of defoliation by western hemlock looper can be identified in tree rings, and can be used to reconstruct historic looper outbreaks.
 

The evolutionary, molecular, and genetic basis for intra-species variation in lodgepole pine (Pinus contorta) secondary metabolite synthesis as a defense against  Dothistroma septosporum.

PhD Student - Tim Owen

This project aims to determine the proximate genetic basis of fungal disease resistance by increased secondary metabolite synthesis, and to correlate this with disease history. An improved knowledge of the genetic basis for Dothistroma resistance will aid in development of resistant varieties, decisions regarding assisted migration, and prediction of future outbreaks.

Mountain pine beetle disturbance dynamics and climate interactions in north-central British Columbia

PhD student - Kate Hrinkevich, completed Sept. 2012
The purpose of this study was to investigate the long-term history of mountain pine beetle outbreaks in north-central BC, and to relate the historical variability of infestations to past disturbances and climate factors. The study also examined the interactions between outbreak regimes and the successional processes driving forest composition and structure. Using the reconstructed disturbance and climate records, historical evidence was compared with characteristics of the current outbreak to determine that the present conditions fall outside the range of natural variability; and that changes in climate are linked to changes in beetle disturbance dynamics.

Spore Dispersal and Infection of Dothistroma septosporum in Northwest British Columbia

MSc Student - Kennedy Boateng, Completed 2011
Spore dispersal and infection of the foliar disease caused by the fungus Dothistroma septosporum (Dorog), which has severely attacked lodgepole pine plantations in northwest British Columbia were studied. Spores were trapped at different distances and heights from single juvenile tree inoculum sources and microclimatic factors were recorded during two consecutive years. One- year-old lodgepole pine seedlings were exposed to natural conditions at the study sites for inoculation. Conidia were trapped from June to September in 2009 whenever rain fell, with a peak in July. It was rare to trap spores more than 2m away from inoculum sources. The timing and number of conidia dispersed were strongly tied to the climatic variables particularly rainfall. Infection by the fungus was strongly influenced by the exposure periods, number of spores and high relative humidity. The results suggest increasing the planting distances between susceptible tree species through mixed species plantations and promoting dry conditions within pine plantations may be valuable strategies to reduce the spread of the disease and manage lodgepole pine plantations in the area.