Constance Harrington - Academia.edu (original) (raw)
Papers by Constance Harrington
Journal of Sustainable Forestry, 1994
Changes in old growth structural features as well as susceptibilities to disturbances were projec... more Changes in old growth structural features as well as susceptibilities to disturbances were projected in stands typical of the eastern Washington Cascades. Projected changes with and without silvicultural operations were made. Doing no silvicultural activities in these stands will not rapidly increase old growth structural fea tures and will allow the stands to become very susceptible to insects and wind breakage, followed by fires. Specifically designed silvicul tural operations can maintain or rapidly increase old growth structur al features and reduce susceptibilities to most disturbances. Unless some trees killed in the silvicultural operations are removed, the treated stands will become very susceptible to fires. Removing some of the thinned trees can also offset the costs of doing the operations. A landscape approach of treating various stands with different silvi cultural regimes will probably best maintain a dynamic balance of structural features, a reduced susceptibility to various disturbances, and a steady flow of wood for manufacturing.
Forest growth models are useful for asking “What if? ” questions when evaluating silvicultural tr... more Forest growth models are useful for asking “What if? ” questions when evaluating silvicultural treatments intended to increase the complexity of future stands. What if we thinned to level A or B? How would it aff ect the growth rates of understory trees? How many trees would survive? To answer these types of questions, a growth model needs to accurately predict the growth and survival of understory trees. Some users of the Forest Vegetation Simulator (FVS) growth model have commented that model predictions for understory trees do not match their fi eld observations or data. To study the relationships which govern growth of understory trees, we assembled a large database from silvicultural experiments and operational inventory data. Th is database provided an opportunity to look at the major factors that aff ect the growth and survival of understory Douglas-fi r (Pseudotsuga menziesii), Western Hemlock (Tsuga heterophylla), and Western Redcedar (Th uja plicata). Tree attributes like ...
Forest Science
Wound closure is an important component of tree recovery from bole damage. Damage to young Dougla... more Wound closure is an important component of tree recovery from bole damage. Damage to young Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stands in the precommercial and commercial stages is common, yet few studies have looked at how trees at these stages of stand development respond to common forms of damage. Using data from a 10-year study of artificially damaged Douglas-fir trees, we found reduced potential for relative wound closure with increasing initial tree bole diameter, and increasing initial relative bole area damaged. Wound-closure rates increased for longer periods of time in more vigorous trees, trees on better-quality sites, and trees with intact live crowns. Wound-closure rates were reduced for trees with more relative bole damage, smaller live crown cross-sections, slower relative diameter growth, and more crown competition. Trees with low levels of bole damage relative to lower bole surface area produced more callus tissue than was necessary to cover the original wound, suggesting that long-term tree stability should recover for low levels of bole damage.
The Olympic Habitat Development Study was initiated in 1994 to evaluate whether active management... more The Olympic Habitat Development Study was initiated in 1994 to evaluate whether active management in 35- to 70-year-old stands could accelerate development of stand structures and plant and animal communities associated with late-successional forests. The study used a variable-density thinning prescription as the main tool to alter stand structure; the prescription entailed creating gaps and retaining uncut areas, and thinning the remaining forest matrix. We assessed tree damage (primarily windthrow) following thinning, 5-year tree growth, and 3-year vegetation development in control and thinned plots. Windthrow damage was minor in most plots, occurring primarily in stands with high height-to-diameter ratios and located in vulnerable topographic positions. Tree growth responded positively to thinning. In addition, tree growth differed spatiallytrees near gaps or along skid trails had better-than-average growth whereas trees near uncut patches had poorer-than-average growth. Underst...
Northwest Science, 2004
We observed flower and fruit production for nine understory shrub species in western Washington a... more We observed flower and fruit production for nine understory shrub species in western Washington and Oregon and examined the relationships between shrub reproductive output and plant size, plant age, site factors, and overstory density to determine the factors that control flowering or fruiting in understory shrubs. In Washington, 50 or more shrubs or microplots (for rhizomatous species) were sampled for each of eight species. The variables examined were more useful for explaining abundance of flowers or fruit on shrubs than they were for explaining the probability that a shrub would produce flowers or fruit. Plant size was consistently the most useful predictor of flower/fruit abundance in all species; plant age was also a good predictor of abundance and was strongly correlated with plant size. Site variables (e.g., slope) and overstory competition variables (e.g., presence/absence of a canopy gap) also helped explain flower/fruit abundance for some species. At two Oregon sites, the...
Pruning trials in young alder stands were sampled to evaluate response to pruning. Effects of pru... more Pruning trials in young alder stands were sampled to evaluate response to pruning. Effects of pruning (1) live branches on different dates, and (2) dead branches with or without damaging the branch collar were assessed on trees pruned in 3- and 6-year-old plantations, respectively. Six years after pruning, stem sections were collected and dissected in the longitudinal-radial plane to expose the center of the stem and branch stub. Ring counts and linear measurements were made for various boundaries or points, including time of pruning, stub length, defect, and beginning of clear wood formation. Pruning during the growing season and, to a lesser extent, late in the growing season when leaf abscission was beginning, resulted in shorter times and distances to formation of clear wood (2.1 years, 14.5 mm) than pruning in the dormant season or just prior to the beginning of the growing season (2.6 years, 18.6 mm). Cutting the branch collar on dead branches led to shorter times and distance...
People have long valued mature western redcedar for its strong, lightweight wood that is rot-resi... more People have long valued mature western redcedar for its strong, lightweight wood that is rot-resistant.The species has cultural importance for Northwest tribes who use the tree’s bark and roots as well as the wood. Redcedar is very shade-tolerant and is often found in the understory and midstory of Pacific Northwest forests. It is also very adaptable and can grow on a wide range of site conditions in both single- and mixed-species stands. In contrast to Douglas-fir, the subject of countless studies related to its growth potential and response to management in the region, very little has been reported for redcedar. A series of studies conducted over 30 years on the responses of young growth redcedar to a wide range of stand, site, and management conditions has led researchers with the Pacific Northwest Research Station to conclude that redcedar is very responsive to management. For example, the species responded well to both thinning and fertilization on a nutrient-poor site, it didn...
Red alder is the most common hardwood in the Pacific Northwest with a range stretching from coast... more Red alder is the most common hardwood in the Pacific Northwest with a range stretching from coastal southeast Alaska to southern California and east to isolated populations in Idaho. Soil moisture during the growing season influences where it grows and its growth rates; it can tolerate poor drainage but not droughty, hot sites. Due to its tolerance of wet soil conditions, alder is common in riparian areas. Alder can be injured by spring and fall frosts and is not found at elevations above 1100 m anywhere in its range. The species produces small, very light seeds that disperse over long distances; it is favored by disturbance and often increases in abundance after logging or burning. Alder establishment via seed is not assured, however, as drought and heat injury, pathogens, animals and other factors often destroy seedlings. Alder has nitrogen-fixing nodules on its roots that directly and indirectly increase nitrogen in forest ecosystems. Alder usually has a spreading fibrous root sy...
Douglas-fir is an iconic tree in the Pacific Northwest. Although individual trees may appear to b... more Douglas-fir is an iconic tree in the Pacific Northwest. Although individual trees may appear to be identical, genetic differences within each tree have resulted from adaptation to the local environment. These genetic differences over time have resulted in differences among populations that are important to the species' survival and growth in changing climates. Current climate models project that over the next 50 years, the Pacific Northwest will experience an increase in summer temperatures. Combined with less winter snowpack, warmer summer temperatures will likely lead to more frequent and intense droughts, and it is unknown how Douglas-fir will respond. Researchers with the U.S. Forest Service Pacific Northwest Research Station tested how seedlings from different populations of Douglas-fir would grow in temperature and precipitation conditions unlike the climate of their current seed source. By sampling 35 populations in three common garden sites, researchers determined how a ...
Garry oak (Quercus garryana) woodlands provide unique habitat for many Pacific Northwest species ... more Garry oak (Quercus garryana) woodlands provide unique habitat for many Pacific Northwest species but these habitats are rapidly disappearing as species composition shifts to conifer or land use changes to urban or agricultural. Many oak trees from former savannas or oak woodlands on Fort Lewis Military Reservation (near Tacoma, WA, USA) are currently overtopped by Douglas-fir (Pseudotsuga menziesii). The shade-intolerant oak has probably survived in these stands due to past thinning activities; however, as the Douglas-fir continues to increase in height, we expect most of the oaks will not survive for long. This study's primary objectives are to determine if overtopped oaks will respond to release treatments, and if so, what pre-treatment tree and stand characteristics can be used to predict response to release. The study utilizes three levels of release in each of four stands overtopped by Douglas-fir.
A suite of large-scale silvicultural experiments has been established to develop and assess opera... more A suite of large-scale silvicultural experiments has been established to develop and assess operational silviculture options for the Pacific Northwest Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) forests. This paper summarizes three such studies that focus on three major stages in the life of managed stands ‐ early development, midrotation, and regeneration harvest. Development of silvicultural treatments that are needed to restore and maintain Oregon white oak (Quercus garryana Dougl. ex Hook.) within mixed-species stands in western Oregon and Washington are also presented. In addition to responses of overstory trees and understory plants to silvicultural treatments, several other aspects, such as coarse woody debris retention, residual stand damage, soil disturbance, economics, and public acceptance of treatments, are also being investigated in one or more of the studies. Advantages, special considerations, and challenges of conducting large-scale, operational...
Trees bursting forth with new leaves signal the arrival of spring. Budburst for most temperate tr... more Trees bursting forth with new leaves signal the arrival of spring. Budburst for most temperate tree species occurs after a tree has been exposed to a sufficient number of chilling and forcing hours over the winter. Waiting until these chilling and forcing hours have accumulated is a survival mechanism. If a tree bursts bud prematurely, delicate tissue may be damaged by a late frost. Conversely, if a tree bursts bud too late in the spring, it will be unable to achieve substantial height growth before summer drought sets in. Although most Northwest tree species require a combination of chilling and forcing hours to promote budburst, the number of hours needed differs by species. To identify the chilling and forcing requirements of 11 common Pacific Northwest tree species, scientists with the U.S. Forest Service, Pacific Northwest Research Station exposed seedlings to various combinations of chilling and forcing temperatures. They tracked the timing of budburst and created possibility ...
The decline of oak woodlands is an urgent conservation challenge in the Pacific Northwest. Prior ... more The decline of oak woodlands is an urgent conservation challenge in the Pacific Northwest. Prior to settlement by Euro-Americans, prairies, oak-dominated savannas, and oak woodlands were abundant in the low-lying areas of the region. Now it’s estimated that 1 to 5 percent of that native oak savanna remains. The rest has been supplanted by pastures, fields, Douglas-fir forests, and development. Experts agree that immediate intervention is needed if Oregon white oak ecosystems are to survive.
In 1999, the Fall River Long-Term Site Productivity study began in coastal Washington to investig... more In 1999, the Fall River Long-Term Site Productivity study began in coastal Washington to investigate how intensive management practices affect soil processes and forest productivity. By comparing conventional harvests to more intensive wood removal treatments, researchers are answering long-standing questions about how residual organic matter influences future growth. Also, by using herbicides to control competing vegetation, they are quantifying the influence other vegetation has on tree growth. Finally, they are measuring soil properties and tree growth on plots where the soil was not compacted during harvest and comparing results to those on plots that were either compacted by logging equipment or compacted and subsequently tilled to restore physical properties.
The timing of spring budburst in woody plants impacts not only the subsequent seasonal growth for... more The timing of spring budburst in woody plants impacts not only the subsequent seasonal growth for individual trees, but also their associated biological community. As winter and spring temperatures have warmed under the changing climate, in many species budburst has been happening earlier in the year. Understanding the long-term effects of this shift and adapting forest management to accommodate it requires deeper insights into the dynamics of budburst. The researchers investigated this topic in a complex of experiments simulating a range of winter conditions for wide range of genetic varieties of Pacific coastal Douglas-fir. Their results, in conjunction with findings from many previous studies on budburst in other plant species, enabled the team to build a mathematical model demonstrating that an intricate interplay between temperatures during winter and spring months is involved in producing this critical first step in the growth cycle. The scientists propose that this relationsh...
Diameter growth is seasonal in Douglasfir, the evergreen tree found in much of western Washington... more Diameter growth is seasonal in Douglasfir, the evergreen tree found in much of western Washington, Oregon, and northern California. Initiation and cessation of diameter growth are both triggered by environmental cues. The tree responds to these cues to improve its chances of growing under favorable conditions. As environmental conditions change, however, land managers want to know how warmer summers and falls may affect diameter growth in Douglas-fir.
Oak species along the West Coast are facing a number of threats, ranging from disease and insects... more Oak species along the West Coast are facing a number of threats, ranging from disease and insects to development and competition for space from other trees. In popular imagination, the oak tree stands for strength, endurance, and longevity. But in the coastal lowlands and central valleys of British Columbia, Washington, Oregon, and California, oaks face a battery of natural and human-induced threats. Sudden oak death, caused by a virulent pathogen identified in 2000, has killed millions of tanoaks, California black oaks, and coast live oaks in California and southern Oregon. In 2008, scientists linked oak deaths in San Diego County to the newly named goldspotted oak borer, an insect first detected in the state in 2004. Over the years, much of the oak landscape along the west coast has been converted to residential and agricultural uses. Where it remains in Washington and Oregon, the sun-loving oak is threatened by encroachment of other trees. In California’s Central Valley, blue and...
Northwest Science
This study evaluated relationships between site or tree characteristics and below-ground material... more This study evaluated relationships between site or tree characteristics and below-ground materials in Douglas-fir forests of the Pacific Northwest. We core-sampled living roots, dead organic matter, and mineral fragments at three soil depths on a 300-sample grid at nine forested sites in western Washington and Oregon resulting in approximately 7200 samples. We explored relationships between materials across depths and at three scales-point, block and site-and examined the data to quantify the degree of spatial clustering. Mass of roots and organic matter declined with depth; there were no consistent patterns with depth for mineral fragments. Correlations between values at the same point but at different depths were low for roots and organic matter at all sites (mean r values < 0.3). Total soil carbon per site was negatively correlated (r =-0.85) with total root mass; correlations between other site or tree variables and below-ground materials were much lower (r =-0.21 to 0.34). There were no detectable spatial patterns in root mass. The number of samples needed to estimate mean root mass was calculated by site and for several desired precision levels; this power analysis will aid others working at similar sites in determining necessary sample sizes a priori, or conversely, in estimating level of precision given a particular sample size. Precision of ± 1.5 kg m-3 could be achieved with less than 100 samples in the upper layer at most sites.
Forest Science
We applied a range of bole and root damage treatments to young Douglas-fir (Pseudotsuga menziesii... more We applied a range of bole and root damage treatments to young Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees. Significant natural damage occurred to tree crowns over the course of the 10-year study allowing for an analysis of how damage severity to tree boles, tree roots, and tree tops impacts growth and cumulative survival of trees. Tree bole damage severity, measured by percent bole circumference removed, exponentially reduced cumulative survival across the study period, whereas damage to tree roots had no significant impact on survival. Bole damage had different impacts on survival depending on the relative size of trees that were damaged. At higher levels of bole damage, trees with larger relative diameters had accelerated mortality rates compared with trees with smaller relative diameters. Tree crown height loss averaged at the treatment within stand level reduced the impacts of bole damage on tree cumulative survival response. Increasing bole, root, and tree crown damage severity led to reductions in estimated maximum diameter and height. Bole damage and damage to tree crowns hastened the decline of diameter growth rates and delayed the decline of height growth rates.
Northwest Science, 2015
Past studies have documented differences in epicuticular wax among several tree species but littl... more Past studies have documented differences in epicuticular wax among several tree species but little attention has been paid to changes in accumulation of foliar wax that can occur during the year. We sampled current-year needles from the terminal shoots of Douglas-fir (Pseudotsuga menziesii var. menziesii) in late June/early July, late August and early November. Needles were sampled from two sites that differed in their climate and shoot phenology. Adaxial (upper), abaxial (lower) and cross-sectional surfaces were examined on scanning electron micrographs. Wax thickness increased significantly (P < 0.01) during the year (from 2.9 ± 0.26 µm in late June/early July to 4.4 ± 0.13 µm in early November). Mean wax thickness was slightly thicker on adaxial (4.0 ± 0.16 µm) than on abaxial (3.5 ± 0.22 µm) surfaces (P = 0.03). There were no significant differences in wax thickness between needles sampled at the base of the terminal shoot or near the tip of the shoot. Tubular or rod-shaped epicuticular wax crystals were sparsely developed on adaxial surfaces, completely covered abaxial surfaces (including filling all stomatal cavities), and had the same general structure and appearance across sites and sampling dates. Some erosion of epicuticular wax crystals on adaxial surfaces and presence of amorphous wax on abaxial surfaces was observed late in the year when epicuticular wax thickness was the thickest. Fungal hyphae were observed on top of epicuticular wax crystals and emerging from stomatal pores.
Journal of Sustainable Forestry, 1994
Changes in old growth structural features as well as susceptibilities to disturbances were projec... more Changes in old growth structural features as well as susceptibilities to disturbances were projected in stands typical of the eastern Washington Cascades. Projected changes with and without silvicultural operations were made. Doing no silvicultural activities in these stands will not rapidly increase old growth structural fea tures and will allow the stands to become very susceptible to insects and wind breakage, followed by fires. Specifically designed silvicul tural operations can maintain or rapidly increase old growth structur al features and reduce susceptibilities to most disturbances. Unless some trees killed in the silvicultural operations are removed, the treated stands will become very susceptible to fires. Removing some of the thinned trees can also offset the costs of doing the operations. A landscape approach of treating various stands with different silvi cultural regimes will probably best maintain a dynamic balance of structural features, a reduced susceptibility to various disturbances, and a steady flow of wood for manufacturing.
Forest growth models are useful for asking “What if? ” questions when evaluating silvicultural tr... more Forest growth models are useful for asking “What if? ” questions when evaluating silvicultural treatments intended to increase the complexity of future stands. What if we thinned to level A or B? How would it aff ect the growth rates of understory trees? How many trees would survive? To answer these types of questions, a growth model needs to accurately predict the growth and survival of understory trees. Some users of the Forest Vegetation Simulator (FVS) growth model have commented that model predictions for understory trees do not match their fi eld observations or data. To study the relationships which govern growth of understory trees, we assembled a large database from silvicultural experiments and operational inventory data. Th is database provided an opportunity to look at the major factors that aff ect the growth and survival of understory Douglas-fi r (Pseudotsuga menziesii), Western Hemlock (Tsuga heterophylla), and Western Redcedar (Th uja plicata). Tree attributes like ...
Forest Science
Wound closure is an important component of tree recovery from bole damage. Damage to young Dougla... more Wound closure is an important component of tree recovery from bole damage. Damage to young Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stands in the precommercial and commercial stages is common, yet few studies have looked at how trees at these stages of stand development respond to common forms of damage. Using data from a 10-year study of artificially damaged Douglas-fir trees, we found reduced potential for relative wound closure with increasing initial tree bole diameter, and increasing initial relative bole area damaged. Wound-closure rates increased for longer periods of time in more vigorous trees, trees on better-quality sites, and trees with intact live crowns. Wound-closure rates were reduced for trees with more relative bole damage, smaller live crown cross-sections, slower relative diameter growth, and more crown competition. Trees with low levels of bole damage relative to lower bole surface area produced more callus tissue than was necessary to cover the original wound, suggesting that long-term tree stability should recover for low levels of bole damage.
The Olympic Habitat Development Study was initiated in 1994 to evaluate whether active management... more The Olympic Habitat Development Study was initiated in 1994 to evaluate whether active management in 35- to 70-year-old stands could accelerate development of stand structures and plant and animal communities associated with late-successional forests. The study used a variable-density thinning prescription as the main tool to alter stand structure; the prescription entailed creating gaps and retaining uncut areas, and thinning the remaining forest matrix. We assessed tree damage (primarily windthrow) following thinning, 5-year tree growth, and 3-year vegetation development in control and thinned plots. Windthrow damage was minor in most plots, occurring primarily in stands with high height-to-diameter ratios and located in vulnerable topographic positions. Tree growth responded positively to thinning. In addition, tree growth differed spatiallytrees near gaps or along skid trails had better-than-average growth whereas trees near uncut patches had poorer-than-average growth. Underst...
Northwest Science, 2004
We observed flower and fruit production for nine understory shrub species in western Washington a... more We observed flower and fruit production for nine understory shrub species in western Washington and Oregon and examined the relationships between shrub reproductive output and plant size, plant age, site factors, and overstory density to determine the factors that control flowering or fruiting in understory shrubs. In Washington, 50 or more shrubs or microplots (for rhizomatous species) were sampled for each of eight species. The variables examined were more useful for explaining abundance of flowers or fruit on shrubs than they were for explaining the probability that a shrub would produce flowers or fruit. Plant size was consistently the most useful predictor of flower/fruit abundance in all species; plant age was also a good predictor of abundance and was strongly correlated with plant size. Site variables (e.g., slope) and overstory competition variables (e.g., presence/absence of a canopy gap) also helped explain flower/fruit abundance for some species. At two Oregon sites, the...
Pruning trials in young alder stands were sampled to evaluate response to pruning. Effects of pru... more Pruning trials in young alder stands were sampled to evaluate response to pruning. Effects of pruning (1) live branches on different dates, and (2) dead branches with or without damaging the branch collar were assessed on trees pruned in 3- and 6-year-old plantations, respectively. Six years after pruning, stem sections were collected and dissected in the longitudinal-radial plane to expose the center of the stem and branch stub. Ring counts and linear measurements were made for various boundaries or points, including time of pruning, stub length, defect, and beginning of clear wood formation. Pruning during the growing season and, to a lesser extent, late in the growing season when leaf abscission was beginning, resulted in shorter times and distances to formation of clear wood (2.1 years, 14.5 mm) than pruning in the dormant season or just prior to the beginning of the growing season (2.6 years, 18.6 mm). Cutting the branch collar on dead branches led to shorter times and distance...
People have long valued mature western redcedar for its strong, lightweight wood that is rot-resi... more People have long valued mature western redcedar for its strong, lightweight wood that is rot-resistant.The species has cultural importance for Northwest tribes who use the tree’s bark and roots as well as the wood. Redcedar is very shade-tolerant and is often found in the understory and midstory of Pacific Northwest forests. It is also very adaptable and can grow on a wide range of site conditions in both single- and mixed-species stands. In contrast to Douglas-fir, the subject of countless studies related to its growth potential and response to management in the region, very little has been reported for redcedar. A series of studies conducted over 30 years on the responses of young growth redcedar to a wide range of stand, site, and management conditions has led researchers with the Pacific Northwest Research Station to conclude that redcedar is very responsive to management. For example, the species responded well to both thinning and fertilization on a nutrient-poor site, it didn...
Red alder is the most common hardwood in the Pacific Northwest with a range stretching from coast... more Red alder is the most common hardwood in the Pacific Northwest with a range stretching from coastal southeast Alaska to southern California and east to isolated populations in Idaho. Soil moisture during the growing season influences where it grows and its growth rates; it can tolerate poor drainage but not droughty, hot sites. Due to its tolerance of wet soil conditions, alder is common in riparian areas. Alder can be injured by spring and fall frosts and is not found at elevations above 1100 m anywhere in its range. The species produces small, very light seeds that disperse over long distances; it is favored by disturbance and often increases in abundance after logging or burning. Alder establishment via seed is not assured, however, as drought and heat injury, pathogens, animals and other factors often destroy seedlings. Alder has nitrogen-fixing nodules on its roots that directly and indirectly increase nitrogen in forest ecosystems. Alder usually has a spreading fibrous root sy...
Douglas-fir is an iconic tree in the Pacific Northwest. Although individual trees may appear to b... more Douglas-fir is an iconic tree in the Pacific Northwest. Although individual trees may appear to be identical, genetic differences within each tree have resulted from adaptation to the local environment. These genetic differences over time have resulted in differences among populations that are important to the species' survival and growth in changing climates. Current climate models project that over the next 50 years, the Pacific Northwest will experience an increase in summer temperatures. Combined with less winter snowpack, warmer summer temperatures will likely lead to more frequent and intense droughts, and it is unknown how Douglas-fir will respond. Researchers with the U.S. Forest Service Pacific Northwest Research Station tested how seedlings from different populations of Douglas-fir would grow in temperature and precipitation conditions unlike the climate of their current seed source. By sampling 35 populations in three common garden sites, researchers determined how a ...
Garry oak (Quercus garryana) woodlands provide unique habitat for many Pacific Northwest species ... more Garry oak (Quercus garryana) woodlands provide unique habitat for many Pacific Northwest species but these habitats are rapidly disappearing as species composition shifts to conifer or land use changes to urban or agricultural. Many oak trees from former savannas or oak woodlands on Fort Lewis Military Reservation (near Tacoma, WA, USA) are currently overtopped by Douglas-fir (Pseudotsuga menziesii). The shade-intolerant oak has probably survived in these stands due to past thinning activities; however, as the Douglas-fir continues to increase in height, we expect most of the oaks will not survive for long. This study's primary objectives are to determine if overtopped oaks will respond to release treatments, and if so, what pre-treatment tree and stand characteristics can be used to predict response to release. The study utilizes three levels of release in each of four stands overtopped by Douglas-fir.
A suite of large-scale silvicultural experiments has been established to develop and assess opera... more A suite of large-scale silvicultural experiments has been established to develop and assess operational silviculture options for the Pacific Northwest Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) forests. This paper summarizes three such studies that focus on three major stages in the life of managed stands ‐ early development, midrotation, and regeneration harvest. Development of silvicultural treatments that are needed to restore and maintain Oregon white oak (Quercus garryana Dougl. ex Hook.) within mixed-species stands in western Oregon and Washington are also presented. In addition to responses of overstory trees and understory plants to silvicultural treatments, several other aspects, such as coarse woody debris retention, residual stand damage, soil disturbance, economics, and public acceptance of treatments, are also being investigated in one or more of the studies. Advantages, special considerations, and challenges of conducting large-scale, operational...
Trees bursting forth with new leaves signal the arrival of spring. Budburst for most temperate tr... more Trees bursting forth with new leaves signal the arrival of spring. Budburst for most temperate tree species occurs after a tree has been exposed to a sufficient number of chilling and forcing hours over the winter. Waiting until these chilling and forcing hours have accumulated is a survival mechanism. If a tree bursts bud prematurely, delicate tissue may be damaged by a late frost. Conversely, if a tree bursts bud too late in the spring, it will be unable to achieve substantial height growth before summer drought sets in. Although most Northwest tree species require a combination of chilling and forcing hours to promote budburst, the number of hours needed differs by species. To identify the chilling and forcing requirements of 11 common Pacific Northwest tree species, scientists with the U.S. Forest Service, Pacific Northwest Research Station exposed seedlings to various combinations of chilling and forcing temperatures. They tracked the timing of budburst and created possibility ...
The decline of oak woodlands is an urgent conservation challenge in the Pacific Northwest. Prior ... more The decline of oak woodlands is an urgent conservation challenge in the Pacific Northwest. Prior to settlement by Euro-Americans, prairies, oak-dominated savannas, and oak woodlands were abundant in the low-lying areas of the region. Now it’s estimated that 1 to 5 percent of that native oak savanna remains. The rest has been supplanted by pastures, fields, Douglas-fir forests, and development. Experts agree that immediate intervention is needed if Oregon white oak ecosystems are to survive.
In 1999, the Fall River Long-Term Site Productivity study began in coastal Washington to investig... more In 1999, the Fall River Long-Term Site Productivity study began in coastal Washington to investigate how intensive management practices affect soil processes and forest productivity. By comparing conventional harvests to more intensive wood removal treatments, researchers are answering long-standing questions about how residual organic matter influences future growth. Also, by using herbicides to control competing vegetation, they are quantifying the influence other vegetation has on tree growth. Finally, they are measuring soil properties and tree growth on plots where the soil was not compacted during harvest and comparing results to those on plots that were either compacted by logging equipment or compacted and subsequently tilled to restore physical properties.
The timing of spring budburst in woody plants impacts not only the subsequent seasonal growth for... more The timing of spring budburst in woody plants impacts not only the subsequent seasonal growth for individual trees, but also their associated biological community. As winter and spring temperatures have warmed under the changing climate, in many species budburst has been happening earlier in the year. Understanding the long-term effects of this shift and adapting forest management to accommodate it requires deeper insights into the dynamics of budburst. The researchers investigated this topic in a complex of experiments simulating a range of winter conditions for wide range of genetic varieties of Pacific coastal Douglas-fir. Their results, in conjunction with findings from many previous studies on budburst in other plant species, enabled the team to build a mathematical model demonstrating that an intricate interplay between temperatures during winter and spring months is involved in producing this critical first step in the growth cycle. The scientists propose that this relationsh...
Diameter growth is seasonal in Douglasfir, the evergreen tree found in much of western Washington... more Diameter growth is seasonal in Douglasfir, the evergreen tree found in much of western Washington, Oregon, and northern California. Initiation and cessation of diameter growth are both triggered by environmental cues. The tree responds to these cues to improve its chances of growing under favorable conditions. As environmental conditions change, however, land managers want to know how warmer summers and falls may affect diameter growth in Douglas-fir.
Oak species along the West Coast are facing a number of threats, ranging from disease and insects... more Oak species along the West Coast are facing a number of threats, ranging from disease and insects to development and competition for space from other trees. In popular imagination, the oak tree stands for strength, endurance, and longevity. But in the coastal lowlands and central valleys of British Columbia, Washington, Oregon, and California, oaks face a battery of natural and human-induced threats. Sudden oak death, caused by a virulent pathogen identified in 2000, has killed millions of tanoaks, California black oaks, and coast live oaks in California and southern Oregon. In 2008, scientists linked oak deaths in San Diego County to the newly named goldspotted oak borer, an insect first detected in the state in 2004. Over the years, much of the oak landscape along the west coast has been converted to residential and agricultural uses. Where it remains in Washington and Oregon, the sun-loving oak is threatened by encroachment of other trees. In California’s Central Valley, blue and...
Northwest Science
This study evaluated relationships between site or tree characteristics and below-ground material... more This study evaluated relationships between site or tree characteristics and below-ground materials in Douglas-fir forests of the Pacific Northwest. We core-sampled living roots, dead organic matter, and mineral fragments at three soil depths on a 300-sample grid at nine forested sites in western Washington and Oregon resulting in approximately 7200 samples. We explored relationships between materials across depths and at three scales-point, block and site-and examined the data to quantify the degree of spatial clustering. Mass of roots and organic matter declined with depth; there were no consistent patterns with depth for mineral fragments. Correlations between values at the same point but at different depths were low for roots and organic matter at all sites (mean r values < 0.3). Total soil carbon per site was negatively correlated (r =-0.85) with total root mass; correlations between other site or tree variables and below-ground materials were much lower (r =-0.21 to 0.34). There were no detectable spatial patterns in root mass. The number of samples needed to estimate mean root mass was calculated by site and for several desired precision levels; this power analysis will aid others working at similar sites in determining necessary sample sizes a priori, or conversely, in estimating level of precision given a particular sample size. Precision of ± 1.5 kg m-3 could be achieved with less than 100 samples in the upper layer at most sites.
Forest Science
We applied a range of bole and root damage treatments to young Douglas-fir (Pseudotsuga menziesii... more We applied a range of bole and root damage treatments to young Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees. Significant natural damage occurred to tree crowns over the course of the 10-year study allowing for an analysis of how damage severity to tree boles, tree roots, and tree tops impacts growth and cumulative survival of trees. Tree bole damage severity, measured by percent bole circumference removed, exponentially reduced cumulative survival across the study period, whereas damage to tree roots had no significant impact on survival. Bole damage had different impacts on survival depending on the relative size of trees that were damaged. At higher levels of bole damage, trees with larger relative diameters had accelerated mortality rates compared with trees with smaller relative diameters. Tree crown height loss averaged at the treatment within stand level reduced the impacts of bole damage on tree cumulative survival response. Increasing bole, root, and tree crown damage severity led to reductions in estimated maximum diameter and height. Bole damage and damage to tree crowns hastened the decline of diameter growth rates and delayed the decline of height growth rates.
Northwest Science, 2015
Past studies have documented differences in epicuticular wax among several tree species but littl... more Past studies have documented differences in epicuticular wax among several tree species but little attention has been paid to changes in accumulation of foliar wax that can occur during the year. We sampled current-year needles from the terminal shoots of Douglas-fir (Pseudotsuga menziesii var. menziesii) in late June/early July, late August and early November. Needles were sampled from two sites that differed in their climate and shoot phenology. Adaxial (upper), abaxial (lower) and cross-sectional surfaces were examined on scanning electron micrographs. Wax thickness increased significantly (P < 0.01) during the year (from 2.9 ± 0.26 µm in late June/early July to 4.4 ± 0.13 µm in early November). Mean wax thickness was slightly thicker on adaxial (4.0 ± 0.16 µm) than on abaxial (3.5 ± 0.22 µm) surfaces (P = 0.03). There were no significant differences in wax thickness between needles sampled at the base of the terminal shoot or near the tip of the shoot. Tubular or rod-shaped epicuticular wax crystals were sparsely developed on adaxial surfaces, completely covered abaxial surfaces (including filling all stomatal cavities), and had the same general structure and appearance across sites and sampling dates. Some erosion of epicuticular wax crystals on adaxial surfaces and presence of amorphous wax on abaxial surfaces was observed late in the year when epicuticular wax thickness was the thickest. Fungal hyphae were observed on top of epicuticular wax crystals and emerging from stomatal pores.