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January 1989 - September 2015
January 1989 - July 2015
January 1989 - July 2015
Publications
Publications (65)
1. Whether plant competition grows stronger or weaker across a soil fertility gradient is an area of
great debate in plant ecology. We examined the effects of competition and soil fertility and their
interaction on growth rates of the four dominant tree species in the sub-boreal spruce forest of
British Columbia.
2. We tested separate soil nutrient...
Dothistroma needle blight, caused by the fungus Dothistroma septosporum, is a major pest of pine plantations in the Southern Hemisphere, where both the host and the pathogen have been introduced.
In northern temperate forests where the pest and host trees are native, damage levels have historically been low; however,
Dothistroma is currently causin...
Because of differences among target tree species in the scaling of NCI to neighbour size and distance (α and β), the absolute scale of NCI varies among the different species. Thus, the absolute magnitude of the C parameter cannot be used to assess the relative sensitivity to crowding among the nine species. Rather, we have plotted the predicted red...
In many regions, forestry practices are shifting to partial harvesting approaches that seek to maintain species and structural diversity in managed forests. We monitored windthrow for 21 years following partial cutting treatments with 0%, 30%, and 60% removal in a large, replicated experiment located in mixed-species mature and old-growth forests o...
In Canada and elsewhere, logging practices in natural-origin forests have shifted toward retention systems where variable levels of mature trees are retained post-logging to promote a diversity of values. We examine multiple sites that experienced a wide range of prior harvest regimes (0–76% basal area removal) to evaluate how harvest intensity and...
Management of temperate forests has the potential to increase
carbon sinks and mitigate climate change. However, those opportunities may be
confounded by negative climate change impacts. We therefore need a better
understanding of climate change alterations to temperate forest carbon
dynamics before developing mitigation strategies. The purpose of...
Population structures of old-growth spruce stands in west-central BC are described, as more fully documented in Kneeshaw & Burton, 1997, J.Veg.Sci. 8(5):615-626, as well as providing a stand-level old-growth score card (more fully developed in Kneeshaw & Burton 1998, Nat.Areas.J. 18(4):293-308). This also reports an early version of planning for ex...
Management of temperate forests has the potential to increase carbon
sinks and mitigate climate change. However, those opportunities may be
confounded by negative climate change impacts. We therefore need
a better understanding of climate change alterations to temperate
forest carbon dynamics before developing mitigation strategies. The
purpose of...
Multi-cohort-based forest management has been proposed as a strategy to conciliate wood supply and biodiversity conservation objectives. At the stand-level, the approach involves using partial harvesting to generate structurally complex stands, notably in terms of tree age, size and species mixtures, conditions that are not easily integrated into y...
We developed models to describe the responses of four commonly examined leaf traits (mass per area, weight, area and nitrogen
(N) concentration) to gradients of light, soil nutrients and tree height in three conifer species of contrasting shade tolerance.
Our observational dataset from the sub-boreal spruce forests of British Columbia included suba...
In British Columbia, many of our second-growth stands have regenerated as mixed-species
stands and yet our understanding of how to manage these stands to achieve multiple goals is
limited. There is considerable interest and need to identify management strategies that will
optimize timber production and carbon storage while maintaining biodiversity...
We examined the performance of older even-aged plantations to check the validity of three of the most fundamental tenets of
forest site productivity: the height–age site index, Eichhorn's rule and the thinning response hypothesis. We assessed the
condition of >14 000 trees in 60 randomly selected plantations to determine whether the stands were fol...
Terrestrial lidar (TLS) is an emerging technology for deriving forest attributes, including conventional inventory and canopy characterizations. However, little is known about the influence of scanner specifications on derived forest parameters. We compared two TLS systems at two
sites in British Columbia. Common scanning benchmarks and identical a...
This transect study in 41–178 year-old stands of Lodgepole pine (Pinus contorta DOUGL. ex. LOUD.) in the southern boreal forest of British Columbia, Canada, analyses how site conditions modify the coarse root–shoot dynamics of trees. The allometric relationship between diameter growth of coarse roots and trunk is scrutinised for long-term site depe...
Stand and disturbance dynamics are key processes that need to be assessed along with climate-species interactions if we are to better understand the impacts of climate change on species. In this study we investigated the biotic interactions (competition) between species, the influence of disturbance type, and changes in resource availability (moist...
Silviculture systems (clear-cut, partial-cut, and unharvested forest) were compared 910 years after harvesting to determine their effects on conifer nutrition and the availability of soil resources, especially nitrogen. These results were used to discuss the effects of silviculture systems on tree growth in relation to the more commonly described...
Observations of tree seedlings with chlorotic foliage and stunted growth near harvest gap – forest edges in interior cedar–hemlock forests inspired a study addressing the following questions: (1) Do seedling foliar chemistry, foliar nitrogen (N) versus growth relationships, and fertilizer responses suggest N-limited seedling growth? (2) Are pattern...
The 5-year height and diameter growth response of a frost-tolerant species, (lodgepole pine, Pinuscontorta var. latifolia Dougl. ex Loud.) and a frost-susceptible species (hybrid spruce, Piceaglauca (Moench) Voss × Piceasitchensis (Bong.) Carr.) to different vegetation-control site-preparation treatment and timing combinations was examined using a...
Soil nitrogen (N) supply and uptake by regenerating trees is an important ecosystem attribute but difficult to quantify in
partial-cut forests where light availability varies. The foliar attributes of N concentration (N%) and N per unit area (Na) may help characterize the influence of soil nutrition, but ideally the relationship between soils and f...
Competition for canopy space is a fundamental structuring feature of forest ecosystems and remains an enduring focus of research attention. We used a spatial neighborhood approach to quantify the influence of local competition on the size of individual tree crowns in north-central British Columbia, where forests are dominated by subalpine fir (Abie...
A Critique of Silviculture bridges a gap between silviculture and ecology that has long hindered the adoption of new ideas. It breaks the mold of disciplinary thinking by directly linking new ideas and fi ndings in ecology and complexity science to the fi eld of silviculture. This is a critically important book that is essential reading for anyone...
Since the mid-1990s the forests of central British Columbia have undergone an unprecedented Mountain Pine Beetle (Dendroctonus ponderosae Hopkins) (MPB) epidemic that has resulted in extensive mortality of canopy lodgepole pine (Pinus contorta var. latifolia Engelm.). This study investigated how seed-source availability, seedbed substrate, overstor...
The topic of model complexity is fundamental to model developers and model users. In this study, we investigate how over- and under-fitting of a driving function in a simulation model influences the predictive ability of the model. Secondly, we investigate whether model selection approaches succeed in selecting driving functions with the best predi...
A series of conventional distance-independent and distance-dependent competition indices, a highly flexible distance-dependent crowding index, and two light resource estimation indices were compared to predict individual tree diameter growth of five species of mature trees from natural-origin boreal mixed forests. The crowding index was the superio...
Large gaps (equivalent to twice the height of the trees, 1590 m(2)) originating from group selection cutting in mixed tolerant hardwood - eastern white pine (Pinus strobus L.) stands of Quebec were used for geostatistical analysis of the seasonal mean of daily percent photosynthetic photon flux density (%PPFD), soil temperature and moisture, regene...
1 Traditional rankings of shade tolerance of trees make little reference to individual size. However, greater respiratory loads with increasing sapling size imply that larger individuals will be less able to tolerate shade than smaller individuals of the same species and that there may be shifts among species in shade tolerance with size. 2 We test...
We compared three commonly used empirical seed/seedling dispersal functions for trees (lognormal, 2Dt, and two‐parameter Weibull) by analysis of published studies where the location of the source is known, as well as by inverse modelling within an old growth hardwood forest in southern Quebec. Almost all the species were wind‐dispersed.
For the dis...
We have developed extensions of traditional distance-dependent, spatial competition analyses that estimate the magnitude of the competitive effects of neighboring trees on target tree growth as a function of the species, size, and distance to neighboring trees. Our analyses also estimate inter- and intra-specific competition coefficients and explic...
The discipline of silviculture is evolving rapidly, moving from an agricultural model that emphasized simple stand structures toward a natural disturbance- or ecosystem-based model where stands are managed for multiple species and complex structures. Predicting stand dynamics and future yields in mixed-species complex structured stands cannot be ea...
We characterized the abundance, size and spatial patterning of canopy gaps, as well as gap-forming processes and light availability in boreal, sub-boreal, northern temperate and subalpine old-growth forests of northwestern British Columbia. The proportion of area in canopy gaps ranged from 32% in northern temperate forests to 73% in subalpine fores...
We model and compare the biological and financial constraints of four prescriptions that serve as alternatives to conventional clearcutting followed by planting in eastern and western boreal mixedwood stands. These alternative prescriptions for full or partial conifer stocking are (1) reliance on advance regeneration with or without augmentation by...
The effects of gradients in light levels and tree height on growth and crown attributes of six conifer species were studied in eastern and western Canada. Three conifers were studied in British Columbia (Abies lasiocarpa (Hook.) Nutt., Picea glauca (Moench) Voss ◊ Picea engelmannii Parry ex Engelm., and Pinus contorta Dougl. ex Loud. var. latifolia...
Tree seedling recruitment was monitored after various types of logging in mixed conifer and deciduous forests of northern British Columbia, Canada. Predicting tree seedling recruitment after disturbance is fundamental to understanding forest dynamics and succession and is vital for forest management purposes. Seedling recruitment success in multi-s...
Saplings of canopy tree species frequently undergo alternating periods of suppression and release before reaching canopy size. In this study, we document the effects of periods of suppression and release on current responses to variation in light by saplings of the 11 major tree species of northwestern, interior British Columbia. We were specifical...
We examine the influence of (i) the spatial distribution and abundance of parent trees (as seed sources) and (ii) the abundance and favourability of seedbed substrates, on seedling recruitment for the major tree species in northwestern interior cedar-hemlock forests of British Columbia, under four levels of canopy openness (full canopy, partial can...
Studies of gap dynamics have contributed significantly to our understanding of the role of small-scale disturbance in forest ecosystems, but have been little used by foresters for predicting tree responses to partial cutting. Fifth year growth and survival of five commonly planted tree species were contrasted in canopy gaps (single-tree to 5000 m2)...
Saplings of canopy tree species frequently undergo alternating periods of suppression and release before reaching canopy size. In this study, we document the effects of periods of suppression and release on current responses to variation in light by saplings of the 11 major tree species of northwestern, interior British Columbia. We were specifical...
We have characterized canopy geometry and light transmission by the nine dominant conifer and broad-leaved tree species of the interior cedar-hemlock (ICH) forests of northern British Columbia. Our field data were used to parameterize a spatially explicit model of light transmission through mixed-species forests. That model, a component of the fore...
We investigated the species richness of ectomycorrhizal fungi based on epigeous sporocarps in an Interior Cedar-Hemlock forest in northwestern British Columbia in gap sizes of 49-4526 m(2), 3-4 years following harvest. We also determined ectomycorrhizal diversity on Pinus contorta var. latifolia Engelm. and Tsuga heterophylla (Raf.) Sarg. seedlings...
Insights into field-planted conifer seedling growth were gained by fitting height and diameter growth to relative irradiance over the growing season using Michaelis-Menten functions. There was little difference among tree species (Abies lasiocarpa (Hook.) Nutt., Picea glauca (Moench) Voss ◊ Picea sitchensis (Bong.) Carr., Pinus contorta Dougl. ex L...
Old-growth stands can be rare in northern coniferous forests, and hence are worthy of protection and special management. We describe some quantitative guidelines for recognizing old-growth stands and options for maintaining a long-term supply of old-growth values in landscapes managed for timber production. In the Sub-Boreal Spruce forests of centr...
We have characterized canopy geometry and light transmission by the nine dominant conifer and broadleaved tree species of the interior cedar–hemlock (ICH) forests of northern British Columbia. Our field data were used to parameterize a spatially explicit model of light transmission through mixed-species forests. That model, a component
of the fores...
Canopy gap size can play a major role in determining composition of tree regeneration after disturbance. The effect of different positions within gaps and within the intact forest has received less study. We seeded six tree species onto two substrates (organic and undisturbed moss) in three positions along a north-south gradient within eight replic...
We characterize variation in radial and height growth of saplings of 11 tree species across a range of light levels in boreal, sub-boreal, subalpine, and temperate forests of northwestern British Columbia. Shade-tolerant species had the greatest response to an increase in light at low-light levels but had low asymptotic growth at high light. Shade-...
We characterize variation in radial and height growth of saplings of 11 tree species across a range of light levels in boreal, sub-boreal, subalpine, and temperate forests of northwestern British Columbia. Shade-tolerant species had the greatest response to an increase in light at low-light levels but had low asymptotic growth at high light. Shade-...
Foresters have traditionally managed forests with silvicultural systems that prescribe stand homogeneity for optimized tree growth. The primacy of timber as the dominant objective is giving way to broader objectives such as sustaining the function and dynamics of ecosystems, maintaining ecosystem diversity and resilience or protecting sensitive spe...
Partial cutting that removed either 30 or 60% of the volume as single trees or small groups up to 0.5 ha had little effect on wind damage to merchantable trees (≥17.5 cm diameter). On average, 6.7 stems per hectare of windthrow occurred across unlogged and logged units, representing approximately 1.9% of the standing trees. Over 2 years, 0.63 m2·ha...
We have developed models of sapling mortality for the eight dominant tree species of northwestern British Columbia in order to better understand forest community dynamics and succession in this important forest region. The species-specific models characterize an individualís probability of mortality as a function of recent growth (a surrogate for w...
Effects of light availability (percentage of above-canopy light,
PACL) on the terminal growth (height increment, caliper,
caliper
2
*
height increment, height increment:caliper ratio) and
leaf characteristics of shade-intolerant lodgepole pine and
moderately shade-tolerant interior spruce were examined on
naturally regenerated seedlings across thre...
Based on data from the Prince Rupert Forest Region. It is concluded that measures of soil moisture and soil nutrients are good predictors of Pinus contorta and Picea glauca site index over a large area. -from Authors
The success of various grass-legume mixtures in controlling competing vegetation, and their effect on subsequent survival and growth of Sitka spruce seedlings was studied on a coastal alluvial site in northwestern British Columbia. Mechanically scarified (bladed) strips were hand seeded to pure and combined mixtures of legumes, bunchgrasses, and so...
The effects of different site preparation treatments and their timing on thimbleberry (Rubus parviflorus) percent cover were examined using a factorial experiment. Methods of thimbleberry control tested were: an untreated control, manual cutting, 1.4 kg active ingredient (a.i.)/ha glyphosate, and 2.1 kg a.i./ha glyphosate. Four treatment dates cove...
The influence of various amounts of shrub and herb cover on microclimate and on survival and growth of Engelmann spruce (Picea engelmannii Parry) and lodgepole pine (Pinus contorta Dougl.) was examined in plots established in the Engelmann Spruce - Subalpine Fir zone of south central British Columbia. The planting sites varied from those with undis...
Knowledge of ecological site characteristics and tree growth on different sites is fundamental for silvicultural decisionmaking and planning. With biogeoclimatic ecosystem classification in place in British Columbia, silvicultural management has been given an ecological foundation; however, relationships between growth and site quality have not yet...