Publications by A.F. Linnell Nemec

Condition, growth, and projected yield of lodgepole pine and interior spruce 20 years after rehabilitation of an understocked site in north-central British Columbia: The Stony Lake trial

Fri, 04 Mar 2011

The Stony Lake trial was established in 1987 to benchmark growth performance of interior spruce (Picea glauca [Moench] Voss x engelmannii Parry ex Engelm.) and lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) planted into 12 treatment regimes for rehabilitating an understocked sub-boreal spruce site (SBSwk1). All combinations of three options for primary site clearing treatments (burn, spray and burn, or windrow), two options for secondary site preparation treatments (disc-trenching or no disc-trenching), and two options for tertiary weeding treatments (broadcast application of herbicide three years after planting or no treatment) were tested. Twenty years after planting, both species had high survival (> 90%), but pine showed much less evidence of damage that could affect future survival or sawlog form than interior spruce. Pine saplings were 57-82% taller and 28-58% larger in diameter than the spruce. Mean total stand volume ranged from 61 to 112 m3/ha for lodgepole pine, with 10 out of 12 treatments yielding > 95 m3/ha at 20 years. Total volume for interior spruce ranged from 28 to 52 m3/ha. High levels of leader weevil damage made it inappropriate to use the Tree and Stand Simulator (TASS) to project future growth for spruce, but simulations for pine predicted yields of at least 300 m3/ha (merchantable volume) between 40 and 50 years after planting for all but one treatment combination. In addition, growth advantages observed in the first 20 years were associated with a yield of higher stand volume and larger logs with potential for a higher recovery of value at harvest. Our results suggest that establishing plantations of lodgepole pine during rehabilitation of similar sites will require fewer entries than interior spruce and produce larger trees and higher stand-level volumes much earlier.

Resistance of half-sib interior Douglas-fir families to Armillaria ostoyae in British Columbia following artificial inoculation

Mon, 25 Oct 2010

The objectives of this study were to (i) develop a methodology for screening conifer seedlings for resistance to Armillaria ostoyae (Romagn.) Herink and (ii) screen a population of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Biessn.) Franco) population for resistance to A. ostoyae. Eighteen potted seedlings from each of 86 half-sib interior Douglas-fir families were challenged with inoculum in a 3-year greenhouse trial. The seed originated from four geographically distinct tree breeding zones that represent physically and biologically different environments in southeastern British Columbia. Mortality and the final percent survival of inoculated trees showed differences among the families (survival range 0%–61.1%) and breeding zones (survival range 6.6%–25.3%). Maximum heritability index (0.19) occurred at 28 months. Survival analyses revealed that most of the differences in survival could be explained by the zone from which the family originated. The less susceptible seedlings originated from the drier and warmer zones and limited the spread of the fungus in the root system. Moderate levels of family variation in resistance to A. ostoyae and low-moderate heritability suggest that, in interior Douglas-fir, gains in resistance can be achieved through breeding.

Effects of selective cutting on the epidemiology of armillaria root disease in the southern interior of British Columbia

Thu, 01 Mar 2001

In selectively cut and undisturbed parts of four mature stands, five 0.04-ha plots were established, and trees were measured, mapped, and examined for aboveground symptoms of armillaria root disease. Trees were felled, and stumps and their root systems were removed by an excavator and were measured and examined for Armillaria lesions. Isolates from root lesions, rhizomorphs associated with lesions, and basidiomes collected in or adjacent to plots were of Armillaria ostoyae (Romagn.) Herink. All trees were assigned to one of five tree condition classes based on the location of lesions and host response. The merchantable volume in each class was calculated. In undisturbed plots, incidence of trees with A. ostoyae lesions on roots was about 10% in the dry climatic region compared with about 75% in the moist region and 35% in the wet region. In plots in the selectively cut parts of the stands, 50-100% of stumps were colonized by A. ostoyae. Results of a logistic regression analysis showed that selective cutting was associated with a statistically significant increase in the probability of a tree having A. ostoyae lesions, where the magnitude of the increase in the proportion of primary roots with lesions and the average number of lesions per diseased tree; however, the increases in disease intensity were statistically significant at only two (one dry and one moist) of the four sites. The percentage of merchantable volume threatened or killed by A. ostoyae was usually higher in cutover than undisturbed plots.

Visible versus actual incidence of Armillaria root disease in juvenile coniferous stands in the southern interior of British Columbia

Sat, 26 Aug 2000

The relationship between aboveground symptoms and belowground incidence of Armillaria ostoyae (Romagn.) Herink on conifers in 13- to 24-year-old stands was investigated at five sites in each of the dry, moist, and wet climatic regions in the Nelson forest region, British Columbia. All trees >1.3 m in height in 0.01-ha circular plots centered on a tree killed fewer than two or more than five years previously or located where there were no symptomatic trees were removed from the soil by an excavator. The location and host response at each A. ostoyae lesion on root systems were recorded. Significant differences in belowground incidence were seen among climatic regions and plot types, with distance from the centre of plots, and between planted and naturally regenerated trees. Belowground incidence was related to the percentage of putatively colonized stumps within and adjacent to plots. There were significant differences among climatic regions in the intensity of infection, host reaction to infection, and percentage of diseased trees showing aboveground symptoms. These results have implications for interpreting results of surveys for Armillaria root disease in juvenile stands and for tending of such stands.