Soil disturbance and juvenile Douglas-fir growth following stump removal on moderately coarse textured soils in southwestern British Columbia: Ten-year results

Mechanized treatment for root diseases like Coniferiporia sulphurascens and Armillaria ostoyae is often avoided due to cost or the perception that removal of stumps creates detrimental soil disturbance or degradation that hinders site productivity. Our study tested five diseased stands that were treated by extracting stumps following harvesting and replanting with susceptible Douglas-fir. Soil disturbance surveys were conducted in treated and untreated plots and individual planted spots were assessed and categorized for soil disturbance using existing and proposed new categories specific to disturbance caused by the stump removal. Tree measurements were taken at intervals over the first 10 years of stand development and foliage was sampled for nutrient analysis. The percentage of total and counted disturbance was 20-46% and 8-11% greater, respectively, in treated versus untreated plots. However, mean tree growth in height and diameter was not statistically different between treatments and was more positive for treated plots at all sites but one. Tree nutrition and survival to age 10 was not negatively affected by stump removal. Total site productivity represented by basal area and tree volume differed widely between sites but was not significantly different between treatments.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Reconstructing Population Dynamics Of Yellow-Cedar In Declining Stands: Baseline Information From Tree Rings

Yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) forests of coastal British Columbia are apparently experiencing decline in a manner similar to that observed in southeastern Alaska. In this pilot study, we collect tree-ring data from live and standing dead yellow-cedar trees from four declining sites on the North Coast of British Columbia. We use this data to compare growth patterns at our sites to those of yellow-cedar trees at non-declining and declining sites in southwestern British Columbia and southeastern Alaska and, in addition, to assess the possibility of reconstructing yellow-cedar population dynamics in declining stands using dendrochronology. We found coherent growth patterns (i.e. marker years and periods of suppression) among yellow-cedar chronologies from non-declining and declining sites across a broad geographic range as well as unique growth patterns between our chronologies from declining sites and those from declining sites in nearby Alaska. Using outer-ring dates of increment cores, we were able to estimate time since death of decade- to century-old standing dead yellow-cedar trees, although the precision of the estimates was influenced by partial cambial mortality and erosion of outer rings. Our results provide baseline dendrochronological information that will be useful for planning future studies that assess growth-climate relations and reconstruct the long-term population dynamics of yellow-cedar in declining stands.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]

Tree-Rings Reveal Accelerated Yellow-Cedar Decline with Changes to Winter Climate after 1980

Research Highlights: Yellow-cedar decline on the island archipelago of Haida Gwaii is driven by warm winter temperatures and low winter precipitation, which is caused by anthropogenic climate change and exacerbated by the positive phase of the Pacific Decadal Oscillation (PDO). Background and Objectives: Declining yellow-cedars are limited by physiological drought during the growing season, caused by freezing damage to fine roots through a complex pathway identified by research in Alaska. Given this, we hypothesized: (1) yellow-cedars on Haida Gwaii were limited by the winter climate. (2) Trees of different health classes were responding differently to climatic variation. (3) Changing climate-growth relations would vary among phases of the PDO. Materials and Methods: We sampled 15 stands exhibiting crown symptoms and developed three regional chronologies from trees that were healthy, had crown or tree-ring symptoms of decline, and trees that had died. We tested for growth responses to inter-annual and multi-decadal variation in climate among trees of different health statuses using correlation functions and wavelet analyses. Results: The three chronologies had similar patterns from the early 1500s to 1900s and responded to climate in the same way, with multi-decadal variability, and common narrow marker years. Climate-growth responses among trees of different health statuses diverged after the 1976/1977 switch in the PDO. Warm growing season temperatures facilitated the growth of trees in the healthy chronology. By contrast, growth of trees that showed symptoms of decline or had died was negatively associated with low winter precipitation. After 1986, growth of trees in the declining chronology decreased sharply and mortality increased, which is concurrent with the warmest winter temperatures and consistent with the root-freezing hypothesis from Alaska. Conclusions: Yellow-cedar decline is driven by climate change, exacerbated by the PDO. Warming winter temperatures, accelerated by anthropogenic climate change, have led to dieback and death of yellow-cedars, even with the temperate ocean-moderated climate of Haida Gwaii.Forestry, Faculty ofNon UBCForest and Conservation Sciences, Department ofReviewedFacultyOthe