Regeneration in mixed conifer clearcuts in the Cascade Range and the Blue Mountains of Eastern Oregon /

Seidel, Kenneth W.

doi:10.5962/bhl.title.94509

Cited by 9 publications

(17 citation statements)

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“…Early developmental stages may have been initiated by stand-replacing fire, logging (Adams and Latta 2007), or expansion into meadows or shrublands (Halpern et al 2010). Early developmental stages in the late 20th century have been truncated and with rapid canopy closure following planting for timber management (Seidel 1979, Sensenig et al 2013), but our data suggest that pathways of protracted development have also been common. Most late developmental stages are associated with a different pathway which includes repeated removal of large trees and fire exclusion followed by recruitment and infilling of shade tolerant trees dating to late 19th and early 20th centuries (Youngblood et al 2004, Merschel et al 2014) and current basal area and density are much higher than in the late 19th and early 20th century (Baker 2012, Hagmann et al 2013, Hagmann et al 2014.…”

Section: Potential Pathways Of Structural Developmentmentioning

confidence: 72%

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Reilly

Spies

2015

Ecosphere

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Despite its importance to biodiversity and ecosystem function, patterns and drivers of regional scale variation in forest structure and development are poorly understood. We characterize structural variation, create a hierarchical classification of forest structure, and develop an empirically based framework for conceptualizing structural development from 11,091 plots across 25 million ha of all ownerships in Oregon, Washington, and inland Northern California, USA. A single component related to live tree biomass accounted for almost half of the variation in a principal components analysis of structural attributes, but components related to live tree density and size, dead wood, and understory vegetation together accounted for as much additional variation. These results indicate that structural development is more complex than a monotonic accumulation of live biomass as other components may act independently or emerge at multiple points during development. The classification revealed the diversity of structural conditions expressed at all levels of live biomass depending on the timing and relative importance of a variety of ecological processes (e.g., mortality) in different vegetation zones. Low live biomass structural types (<25 Mg/ha) illustrated the diversity of early‐seral conditions and differed primarily in density of live trees and abundance of snags and dead wood. Moderate live biomass structural types (25–99 Mg/ha) differed in tree size and density and generally lacked dead wood, but some structurally diverse types associated with partial stand‐replacing disturbance had abundant live and dead legacies. High live biomass structural types (>100 Mg/ha) substantiated the diversity of later developmental stages and exhibited considerable variation in the abundance of dead wood and density of big trees. Most structural types corresponded with previously described stages of development, but others associated with protracted early development, woodland/savannah transitions, and partial stand‐replacing disturbance lacked analogs and indicated alternative pathways of development. We propose a conceptual framework that distinguishes among families of pathways depending on the range of variation along different components of structure, the relative importance of different disturbances, and complexity of pathways. Our framework is a starting point for developing more comprehensive models of structural development that apply to a wider variety of vegetation zones differing in environment and disturbance regimes.

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Section: Potential Pathways Of Structural Developmentmentioning

confidence: 72%

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Reilly

Spies

2015

Ecosphere

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“…Indeed, aspect had a dramatic effect on the pace and intensity of overstory development, with canopy closure occurring .10 yr earlier on N than on S aspects. Substantially greater densities of Pseudotsuga and shade-tolerant Tsuga (Lutz and Halpern 2006) are indicative of a less stressful regenerative environment on N aspects (Isaac 1943, Silen 1960, Larson and Franklin 2005. Although aspect-related declines in understory richness and cover were consistent with a model of resource preemption (i.e., greater canopy shading or greater root competition with trees [Coomes andGrubb 2000, Lindh et al 2003]), the differences between aspects were much less dramatic than those of the overstory.…”

Section: Variation Across Resource and Environmental Stress Gradientsmentioning

confidence: 98%

“…Manuscript Several factors are likely to contribute to variation in understory decline during canopy closure: the pace or intensity of closure, variation in resource supply, the extent to which trees preempt these resources, and the ability of understory species to tolerate the conditions. Numerous factors may influence the pace of overstory development, including post-disturbance seed limitations, resource or other environmental constraints, and competition with early-seral vegetation (Seidel 1979, Graham et al 1982, Haeussler and Coates 1986, Donato et al 2012. Topography and soils jointly determine the supply of light, soil moisture, and nutrients to the understory, but trees can preempt these resources.…”

Section: Introductionmentioning

confidence: 99%

Canopy closure exerts weak controls on understory dynamics: a 30‐year study of overstory–understory interactions

Halpern

Lutz

2013

Ecological Monographs

153

102

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Stem exclusion and understory reinitiation are commonly described, but poorly understood, stages of forest development. It is assumed that overstory trees exert strong controls on understory herbs and shrubs during the transition from open‐ to closed‐canopy forests, but long‐term observations of this process are rare. We use long‐term data from 188 plots to explore patterns and correlates of variation in understory richness and abundance 15–45 years after clear‐cut logging and burning of two experimental watersheds in western Oregon, USA. We test whether variation in the temporal dynamics of plots can be explained by topoedaphic factors that influence resource availability (insolation and soil moisture), variation in the pace and intensity of overstory development, or characteristics of the vegetation prior to canopy closure. Changes in forest structure were substantial over the study period; canopy cover increased fourfold, stem density by 75%, and bole biomass by two orders of magnitude, although trends were highly variable among individual plots. In contrast, understory richness, foliar cover, and biomass declined only 30–40%, driven by loss of early‐seral colonists, not residual forest species. Canopy closure occurred earlier on north aspects but declines in understory biomass, reflecting loss of colonizing shrubs (without concomitant increases in forest shrubs), were limited to south aspects. In contrast, variation in effective soil moisture had little influence on the pace of decline. Temporal trends were highly asynchronous among plots: nearly 50% of plots experienced some form of decline, but >35% showed no discernible trend. Declines were more likely in plots with greater tree influence before or at peak overstory development, but also in plots with greater understory development prior to canopy closure. Quantile regression models indicated weak relationships between understory biomass and overstory structure at most points in time. Our long‐term data support a model of understory dynamics in which characteristics of the pre‐closure vegetation are as important as overstory structure in determining the timing and nature of decline. Long‐term studies are critical for elucidating patterns and processes that cannot be inferred from short‐term experiments or space‐for‐time substitutions.

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“…The units were selected from among a larger number of units used in an earlier study that described the status of regeneration in mixed conifer communities in the Cascade Range in Oregon. The sampling design and criteria for selecting these units are given in earlier reports (Seidel 1979a(Seidel , 1979b.…”

Section: Methodsmentioning

confidence: 99%

Growth response of suppressed true fir and mountain hemlock after release.

Seidel¹

1985

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The diameter and height growth of advance reproduction of suppressed true fir (Abies spp.) and mountain hemlock (Tsuga mertensiana (Bong.) Carr.) was measured in south-central Oregon after release by overstory removal in clearcuttings, shelterwood units, and uncut stands. Postrelease growth was greatest in clearcuttings, intermediate in shelterwood cuttings, and slowest in uncut stands. Multiple regression analyses were used to predict growth response as a function of tree and stand variables. Overstory basal area, live crown ratio, and past 5-year height growth accounted for the most variation in diameter and height growth after release. Vigorous advance reproduction having live crown ratios greater than 50 percent are the best candidates for crop trees.Keywords: Growth response, release, suppression (tree), advance growth, true fir, mountain hemlock.In 1983 and 1984, a study was conducted in the Cascade Range in south-central Oregon to obtain information about the diameter and height growth response of suppressed advance reproduction of grand fir (Abies grandis (Dougl. ex D. Don) Lindl.), Shasta red fir (Abies magnifica var. shastensis Lemm.), and mountain hemlock (Tsuga mertensiana (Bong.) Carr.) after release by removal of the overstory. The purpose was to compare rates of diameter and height growth before and after release, to determine when increased growth occurs, and to develop models to predict diameter and height growth after release as a function of tree and stand variables, such as live crown ratio and basal area.The study areas were clearcut and shelterwood units and uncut stands in upper slope, mixed conifer/snowbrush-chinkapin and mountain hemlock/grouse huckleberry communities in the Deschutes and Winema National Forests, south-central Oregon. Growth patterns 5 years before and 10 to 20 years after release of the trees were determined by sectioning trees.Both diameter and height growth increased after release from two to four times the prerelease rate for both fir and hemlock. Acceleration of growth generally occurred within 5 years after release with the most rapid growth occurring on clearcut units. Growth curves had a sigmoid form showing constant growth before release, a rapid acceleration during the first 8 to 9 years after release, followed by a flattening of the curves from 10 to 20 years after release.Residual overstory basal area, live crown ratio, and past 5-year height growth were the three variables accounting for most of the variation in diameter and height growth after release. Growth of the advance reproduction after release was directly proportional to live crown ratio or past height growth and inversely proportional to overstory stand density. Both fir and hemlock responded to release regardless of age.The.best potential crop trees are vigorous advance reproduction having live crown ratios greater than 50 percent and those with the greatest height growth before release. Releasing these trees by removing the overstory and by thinning when needed will not only greatly increase grow...

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Regeneration in mixed conifer clearcuts in the Cascade Range and the Blue Mountains of Eastern Oregon /

Cited by 9 publications

References 0 publications

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Canopy closure exerts weak controls on understory dynamics: a 30‐year study of overstory–understory interactions

Growth response of suppressed true fir and mountain hemlock after release.

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