Understory vegetation in old and young Douglas-fir forests of western Oregon

Bailey, John D.; Mayrsohn, Cheryl; Doescher, Paul S.; Pierre, Elizabeth St.; Tappeiner, John C.

doi:10.1016/s0378-1127(98)00408-3

Cited by 106 publications

(81 citation statements)

References 19 publications

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“…Many of the species in this study develop abundant and persistent seed banks in the soil, which may allow them to respond quickly to changes in conditions (Hodgson, 1968;van Baalen, 1982;Crompton et aL, 1988;Doucet and Cavers, 1996). A study of thinning in stands in western Oregon also found greater richness of nonnative species in thinned stands than in unthinned stands, even 10--24 yr after thinning (Bailey et al, 1998).…”

Section: An Graymentioning

confidence: 56%

Eight nonnative plants in western Oregon forests: Associations with environment and management

Gray

2005

Environ Monit Assess

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Abstract. Nonnative plants have tremendous ecological and economic impacts on plant communities globally, but comprehensive data on the distribution and ecological relationships of individual species is often scarce or nonexistent. The objective of this study was to assess the influence of vegetation type, climate, topography, and management history on the distribution and abundance of eight selected nonnative plant taxa in forests in western Oregon. These eight taxa were selected as being reliably detected by a multi-resource inventory of 1127 systematically-placed plots on nonfederal forest lands from 1995 to 1997 by the USFS Forest Inventory and Analysis (FIA) program. One or more of the eight nonnative taxa studied were found on 20% of the sampled subplots in the study area, but relatively few stands were dominated by them. Overall abundance of nonnative taxa was likely much greater, because few composites and graminoids were identified to species in this general-purpose inventory. Distribution of most taxa was more closely associated with low density of overstory trees than with climate. Nonnative taxa were significantly more abundant in stands that had been recently clearcut or thinned than in stands that had not. Frequencies of several taxa decreased with elevation, which may reflect proximity to source populations and intensive land use rather than any climatic constraints. Although the greatest potential for displacement of native forest species appears to be in early-successional communities, the potential for spread of some shade-tolerant evergreen shrubs also seems high.

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Section: An Graymentioning

confidence: 56%

Eight nonnative plants in western Oregon forests: Associations with environment and management

Gray

2005

Environ Monit Assess

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“…They may have interesting attributes for forest health and conservation. Stands with lower initial densities may develop old-growth characteristics more quickly than stands with higher initial densities (Acker et al 1998, Bailey et al 1998. And a lower density of trees might allow a lengthy shrub phase of succession, where nitrogen-fixing shrubs like Ceanothus enhance soil nutrients.…”

Section: Future Development and Management Implicationsmentioning

confidence: 99%

Natural tree regeneration and coarse woody debris dynamics after a forest fire in the western Cascade Range

Brown¹,

Kertis²,

Huff³

2013

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Cover photosPlot number 16 at 7 and 14 years after fire. At 7 years, there is abundant regeneration of Pseudotsuga menziesii under a canopy of snags. At 14 years, the snag canopy is thinning out owing to snag fall and fragmentation; tree, shrub, and herb regeneration mix but trees are the tallest elements.This work was performed under USDA Forest Service PO AG-04T0-P-10-0057. We monitored coarse woody debris dynamics and natural tree regeneration over a 14-year period after the 1991 Warner Creek Fire, a 3631-ha (8,972-ac) mixedseverity fire in the western Cascade Range of Oregon. Rates for tree mortality in the fire, postfire mortality, snag fall, and snag fragmentation all showed distinct patterns by tree diameter and species, with Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) more likely to survive a fire, and to remain standing as a snag, than other common tree species. Natural seedling regeneration was abundant, rapid, and highly variable in space. Densities of seedlings >10 cm height at 14 years postfire ranged from 1,530 to 392,000 per ha. Seedling establishment was not concentrated in a single year, and did not appear to be limited by the abundant growth of shrubs.The simultaneous processes of mortality, snag fall, and tree regeneration increased the variety of many measures of forest structure. The singular event of the fire has increased the structural diversity of the landscape.Keywords: Fire severity, monitoring, coarse woody debris, reforestation, snag recruitment, regeneration. SummaryWe monitored natural tree regeneration and coarse woody debris dynamics over 14 years following the 1991 Warner Creek Fire, a 3,631-ha (8,972-ac) mixed-severity fire in the western Cascade Range of Oregon. The results provide a detailed picture of the variety of natural postfire conditions in westside Cascade forests, and demonstrate how a single mixed-severity fire can increase variety in forest structures.We studied 24 permanent plots representative of the burned area and its mix of fire severities, which ranged from 0.1 to 100 percent of prefire canopy killed. Plots This postfire mortality rate was higher in plots with higher initial fire severity.Much of the new snag volume quickly transferred to the ground via snag fall and fragmentation. Small snags, and A. amabilis snags, were more likely to fall. Larger snags were more likely to fragment.Natural seedling regeneration was abundant, and highly variable in space. Densities of seedlings >10 cm height at 14 years postfire ranged from 1,670 to 392,000 per ha in the higher elevation zone, and from 1,530 to 47,500 per ha in the lower zone. New seedlings were observed over all study visits, in patterns demonstrating that establishment was not concentrated in a single year. The growth of shrubs was abundant but did not appear to be limiting tree regeneration. The mixed-severity fire, followed by variable mortality, snag fall, and tree regeneration, led to an increase in variability, among plots, of several metrics of forest structure. The prominence of P. menziesii ...

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“…In the Cascades and Coast Range, mature stands at 5 of the 6 sites were less than 70 years old and most likely established following clearcutting, while the 90 year old mature stand at the remaining locale could have resulted from either early logging or wildfire. Stand structure and vegetative composition were studied at eight of our nine locales by Bailey et al [21] and Bailey and Tappeiner [22].…”

Section: Methodsmentioning

confidence: 99%

“…Trees that experience an increase in light have been shown to increase allocation of carbon to roots and mycorrhizal fungi [52], which would lead to increased input of dead fine roots and hyphae, and greater understory biomass in thinned than unthinned stands [21] would likely include relatively shallow-rooted species. In any event, it seems likely that the relatively weak contribution of SOM to our multivariate models stemmed in part at least from mean SOM values in thinned stands that were intermediate between old growth and unthinned mature, something that was not true for the variables that contributed most significantly to the multivariate models.…”

Section: Differences In Stand Typesmentioning

confidence: 99%

“…Thinning younger stands has been proposed as a way to accelerate the development of OG characteristics and improve habitat for species that depend on structurally complex forests [19]. A number of studies have dealt with how thinning affects aboveground components of ecosystems, including understory vegetation [20,21], forest structure [22], and vertebrate habitat [23][24][25][26][27]. Effects on soils and soil/litter fauna, vital components of ecosystems, are less well researched.…”

Section: Introductionmentioning

confidence: 99%

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Abiotic and Biotic Soil Characteristics in Old Growth Forests and Thinned or Unthinned Mature Stands in Three Regions of Oregon

et al. 2012

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Abstract:We compared forest floor depth, soil organic matter, soil moisture, anaerobic mineralizable nitrogen (a measure of microbial biomass), denitrification potential, and soil/litter arthropod communities among old growth, unthinned mature stands, and thinned mature stands at nine sites (each with all three stand types) distributed among three regions of Oregon. Mineral soil measurements were restricted to the top 10 cm. Data were analyzed with both multivariate and univariate analyses of variance. Multivariate analyses were conducted with and without soil mesofauna or forest floor mesofauna, as data for those taxa were not collected on some sites. In multivariate analysis with soil mesofauna, the model giving the strongest separation among stand types (P = 0.019) included abundance and richness of soil mesofauna and anaerobic mineralizable nitrogen. The best model with forest floor mesofauna (P = 0.010) included anaerobic mineralizable nitrogen, soil moisture content, and richness of forest floor mesofauna. Old growth had the highest mean values for all variables, and in both models differed significantly from mature stands, while the latter did not differ. Old growth also averaged higher percent soil organic matter, and analysis including that variable was significant but not as strong as without it. Results of the multivariate analyses were mostly supported by univariate analyses, but there were some differences. In univariate analysis, the difference in percent soil organic matter between old growth and thinned mature was due to a single site in which the old growth had exceptionally high soil organic matter; without that site, percent soil organic matter did OPEN ACCESSDiversity 2012, 4 335 not differ between old growth and thinned mature, and a multivariate model containing soil organic matter was not statistically significant. In univariate analyses soil mesofauna had to be compared nonparametrically (because of heavy left-tails) and differed only in the Siskiyou Mountains, where they were most abundant and species rich in old growth forests. Species richness of mineral soil mesofauna correlated significantly (+) with percent soil organic matter and soil moisture, while richness of forest floor mesofauna correlated (+) with depth of the forest floor. Composition of forest floor and soil mesofauna suggest the two groups represent a single community. Soil moisture correlated highly with percent soil organic matter, with no evidence for drying in sites that were sampled relatively late in the summer drought, suggesting losses of surface soil moisture were at least partially replaced by hydraulic lift (which has been demonstrated in other forests of the region).

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Understory vegetation in old and young Douglas-fir forests of western Oregon

Cited by 106 publications

References 19 publications

Eight nonnative plants in western Oregon forests: Associations with environment and management

Eight nonnative plants in western Oregon forests: Associations with environment and management

Natural tree regeneration and coarse woody debris dynamics after a forest fire in the western Cascade Range

Abiotic and Biotic Soil Characteristics in Old Growth Forests and Thinned or Unthinned Mature Stands in Three Regions of Oregon

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