36 research outputs found
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Leaf litter chemistry and decomposition in a Pacific Northwest Coniferous forest ecosystem
No full textThe effects of initial leaf litter chemistry of 16 common coniferous and deciduous hardwoods and shrubs on their annual decomposition patterns were studied on the H.J. Andrews Experimental Forest (Oregon). Leaf litters were characterized by their chemical qualities, which included measurement of elemental fractions (C, N, P, K, Ca, Mg), proximate fractions (non-polar, polar, acid-soluble extractives, acid-soluble lignin and acid-insoluble "Klason lignin"), and colorimetric characters (total phenolics, reactive polyphenolics, water-soluble carbohydrates, water-soluble condensed tannins, and water and acid-insoluble condensed tannins). These analytical methods improve upon traditional proximate analysis (Ryan et al. 1990) used to characterize leaf litters, through measurement of reactive and residual phenolic fractions and acid-soluble lignin. This paper discusses the procedures that are involved in improving proximate analysis and the link between leaf chemistry and one year
decomposition rates. Significant differences were found in leaf litter qualities and in
decomposition rates (expressed as decay) among species. The annual decay (k) for the leaf litter ranged from 0.27 to 1.02. The decay values for all species combined had highly significant (p [less than or equal to] 0.0001) correlations with 29 out of the 36 initial chemistry variables tested. The three highest correlations were with acid-insoluble
condensed tannins (r= 0.83 p [less than or equal to] 0.0001 n=339), the lignocellulose index (r= -0.81 p[less than or equal to] 0.0001, n=339) and acid-insoluble residue or 'Klason lignin" (r= -0.80 p [less than or equal to] 0.0001, n=339). A multiple regression model with all 16 species suggested that annual decomposition was best related to acid-insoluble condensed tannins, Klason lignin, water-insoluble condensed tannins, Ca and total phenolic:N ( R²=0.84, p [less than or equal] 0.0001, n= 339). Correlation and multiple linear regression models with each species' decay rate revealed that no one single initial chemical predictor could best explain the decomposition rates for each of the 16 species and that there were a wide range of chemical predictors related to the patterns of decomposition for each species
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Traditional ecological knowledge to develop and maintain fire regimes in northwestern California, Klamath-Siskiyou bioregion : management and restoration of culturally significant habitats
No full textThe use of Native American fire regimes evolved in the Klamath-Siskiyou bioregion over millennia. A mixture of Native American and Euro-American socio-cultural management has developed from adaptations to climate, topography, ecological processes, and land use practices. This research incorporates Traditional Ecological Knowledge (TEK) to partially examine the role of tribal fire uses and ethnobotany. Research methods use an interdisciplinary approach to characterize fuels and fire management issues in culturally significant riparian and terrestrial habitats. Tribal fuels and fire management practices were investigated. Understanding past tribal fire management systems is needed to place contemporary Native American fuels and fire management issues in to context for government agencies and private interest that have altered tribal opportunities to continue fire uses.
This study examined fire effects on sandbar willow (Salix exigua) in valley riparian zones along the lower mid-Klamath River. Prescribed fire was used to induce sprouting of sandbar willow and reduce insect populations to improve basket material quantity and quality. Results indicate that flooding had greater affects on the structure, composition, and abundance of vegetation and fuels than prescribed fire. A second experiment to compare the effect of propane burning and pruning sandbar willow indicated that propane burning was less effective than pruning to improve stem morphology for basket weaving. Consultation with tribal basket weavers and research of the proportion of useable willow shoots, amount of insect damage and the relationship of stem diameter and length revealed these attributes were important criteria for determining usability for weaving. This research also included other basketry plants.
TEK is used to better understand fire effects on culturally significant resources and the consequences of fire suppression on terrestrial and riparian habitats. The mechanisms of how fire suppression impacts tribes, resources and tribal land uses are presented. Recommendations are presented for additional research to improve collaboration with tribes, tribal organizations and communities based on contemporary tribal values and priorities for fuels and fire management
Mass, Nutrient Content, and Decay Rate of Dead Boles in Rain Forests of Olympic National Park
No full textAnalysis of the distribution of dead boles of Picea sitchensis and Tsuga heterophylla in open- and closed-canopy forests of the Olympic Peninsula, Washington, USA showed that T. heterophylla mortality in both forest types resulted mainly from windthrow, whereas P. sitchensis typically died upright. The open forest contained 120 t/ha and the closed forest 161 t/ha of dead bole wood. Boles of T. heterophylla decayed more rapidly than larger boles of P. sitchensis, though both showed considerable variation. Nutrient contents of dead boles in kg/ha for open- and closed-canopy (brackets) forests were: N 146 (223); Ca 147 (197); K 39 (61); Mg 18 (29) Na 6 (14); and P 17 (29). Except for N and Mg, nutrient concentration of the wood were not significantly different after 33-68 yr of decay. The N : P ratios increased with decay for both species. From authors\u27 summary
Long-term effects of prescribed underburning on litter decomposition and nutrient release in ponderosa pine stands in central Oregon
No full textThe effects of low-intensity prescribed underburning on the rates of litter decomposition and N and P release in ponderosa pine (Pinus ponderosa Dougl. ex. Laws) stands were studied by a litter-bag technique for 18 months in sites burned 0.3, 5, or 12 years earlier. Litter decomposition rates (k) were low, between 0.15 and 0.28 year-1, and were significantly (P < 0.1) reduced by prescribed fire on the sites burned 0.3 and 12 years earlier. However, the reduction in decomposition rates was small, from 0.22 to 0.19 year-1 on the sites burned 12 years earlier, and from 0.172 to 0.167 year-1 on the sites burned 0.3 year earlier. Nitrogen tended to be immobilized in the decomposing litter, while P was rapidly released, suggesting that these ecosystems are limited by N but not by P. Nitrogen showed a distinctive seasonal pattern of net immobilization during winter and a net release during summer. Prescribed burning significantly increased the release of N and P from the litter on the sites burned 5 years earlier, a pattern that may indicate changes in microbial activity in the forest floor. However, there were no significant differences in nutrient dynamics on the remaining sites. © 1996 Elsevier Science B.V. All rights reserved
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The effects of natural fire and recreational disturbance on montane forest ecosystem composition, structure and nitrogen dynamics, Crater Lake National Park, Oregon
No full textDisturbance, whether natural or of human origin, modifies to varying degrees
many ecosystem attributes. Fire is a natural process in the montane forests of southern
Oregon but for much of the 20th century fire was viewed as an apocalypse and thus
fervently suppressed. Effective natural resource management requires an
understanding of how ecosystems function, including the ecological response to the
natural disturbance regime or anthropogenically altered conditions.
To describe the effects of natural fire and ecosystem changes with time
following fire, I examined plant composition, structure, biomass and soil nitrogen
using a chronosequence of sites ranging in age from 1 to >300 years. The ecological
importance of human activity is a function of the magnitude and permanence of its
effects which were described at active and abandoned recreation sites.
Stand-replacing fires killed virtually 100% of the overstory trees, consumed
87% of the forest floor and resulted in a 27% loss in total aboveground biomass. A
pulse of mineralized nitrogen was still apparent 2 years following fire.
Two years following fire, little plant colonization was established. The
availability of local seed sources, particularly seedbanking species, appears to have
been an important determinant of the early-successional community composition. The
developing community was dominated by nitrogen-fixing species which may play an
important role in the post-fire nitrogen dynamics in these ecosystems. Conifer
seedling densities measured 667 individuals/ha 8 years following fire and 1714
individuals/ha 24 years after fire.
Extended tree maturation and variation in composition characterized the forest
structure and composition during secondary succession. Total aboveground biomass
remained high and accumulation followed a general U-shaped curve.
Recreational use resulted in a reduction in tree density and biomass at all active
sites. The greatest reductions occurred at sites set in late-successional forests.
Compositional change was also greatest at sites established in late-successional forest
with increased dominance of lodgepole pine and graminoids. Within 40 years the
abandoned, mid-successional sites had recovered from most of the recreational
impacts; however 40 years was not sufficient for late-successional forest recovery.
These results suggest that the stage of succession should be considered when assessing
potential recreational impacts
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Effects of burrowing by mountain beaver (Aplodontia rufa) on soil in a young forest in the Oregon Coast Range
No full textSoil effects from mountain beaver (Aplodontia rufa ) burrowing were
investigated in Oregon Coast Range soils formed from Tyee sandstone. The potential
for observed changes in soil to affect productivity was assessed. Soil horizons from
mountain beaver mound soil and adjacent unmounded profiles were collected with a
monolith-type quantitative sampler. Bulk density, changes in soil depth, soil C
(estimated from LOI), Kjeldahl-N, Kjeldahl-P, and Oxalate extractable P and K were
measured. Results from these analyses were normalized for differences in organic
material by calculating variables as a mass per hectare per fixed weight of ashed soil.
This approach combined the advantages of sampling by individual soil horizons, with
statistical tools to compare soil profiles with dissimilar horizonal arrangements.
Patterns of soil mixing due to mountain beaver, as well as dimensions and arrangement
of a single burrow are described. Mountain beaver mixing altered the depth distribution
of C, N, and P, increased soil depth, and reduced bulk density. The distribution of
gravel in unmounded profiles suggested a history of soil mixing on this site that
obscured mixing effects attributable to recent mountain beaver activity. Colluvial
action, windthrow, and past animal activity are the most likely causes of background mixing in unmounded profiles. Soil mixing attributed to mountain beavers has the
potential to increase site production by increasing soil depth and decreasing bulk
density, which can in turn affect moisture holding capacity and rooting depth. Results
suggest that mountain-beaver mixing did not change site capital of plant nutrients but
altered their distribution within the soil. Potential effects of described changes on
short-term and long-term weathering release of plant nutrients is discussed. Mountain
beaver mixing resulted in exposure of loose mineral soil on the surface which may
increase dry ravel erosion. Thus, burrowing animal activity may represent an important
sediment export mechanism from managed stands
A regional approach to litter dynamics in Southern Appalachian forests
No full text Foliage litterfall, Ol litter mass, and its Mg, P, and K content were estimated for six forest types in the Southern Appalachian region using 252 forest survey plots of the USDA Forest Service. General allometric equations were used to compute foliage litterfall, and average species foliage elemental concentrations were used for litterfall elemental content. Exponential decay rate constants (k) of foliage mass and elements were estimated from foliage lignin concentrations. The procedure was tested with measured litterfall and Ol litter at Coweeta Hydrologic Laboratory and selected Forest Service plots in Macon County, North Carolina. Litterfall and Ol litter mass were accurately computed. Elemental content of litterfall and Mg and K mineralization rates were overestimated; P mineralization rate was underestimated. First-year immobilization of Ca may render the exponential decay model invalid for Ca. </jats:p
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Leaf litter chemistry controls on decomposition of Pacific Northwest trees and woody shrubs
No full textThe effects of initial leaf litter chemistry on first-year decomposition rates were studied for 16 common Pacific
Northwest conifers, hardwoods, and shrubs at the H.J. Andrews Experimental Forest in western Oregon. Leaf litters were analyzed for C, N, P, K, Ca, Mg, proximate organic fractions (nonpolar, polar, acid-hydrolyzable extractives, acid-hydrolyzable lignin, and acid-unhydrolyzable residue, previously termed “Klason lignin”), and biochemical components (total phenolics, reactive polyphenols, water-soluble carbohydrates, water-soluble proanthocyanidins, and waterand acid-unhydrolyzable proanthocyanidins). By including measurements of reactive and residual phenolic fractions and acid-hydrolyzable lignin, these analytical methods improve upon traditional proximate leaf litter analyses. Significant differences in litter chemistries and decomposition rates were found between species. For all species combined, the 1-year decay rate (k) values had highly significant correlations (P < 0.001) with 30 out of the 36 initial chemistry variables tested in this study. The three highest correlations were with acid-unhydrolyzable proanthocyanidins, lignocellulose index, and acid-unhydrolyzable residue (r = 0.83, –0.81, –0.80, respectively, with P < 0.0001 and n = 339). We found
that no single litter chemistry variable was a universal predictor of the 1-year k value for each of the individual 16 species studied, though phenolic components were more frequent significant (P < 0.001) predictors of decomposition rate
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Autecological studies of two annual herbs, Senecio sylvaticus and Epilobium paniculatum : effects of biotic and abiotic factors
No full textI used greenhouse and field studies to investigate how intraspecific and
interspecific competition, soil disturbance, and fertilization affect the biomass and
reproductive output of Senecio sylvaticus and Epilobium paniculatum, common winter
annuals which invade and dominate western Cascades forests during the first two seasons
after clearcutting and slashburning.
Field work experiments were conducted separately for each species on two
clearcuts in their third and fourth growing seasons post-disturbance. The clearcuts were
located in the Willamette National Forest near Blue River, Oregon. Experiments were
conducted fall 1992 through summer 1993. Research goals were to determine the effects
of nutrient availability, interspecific competition, and ground disturbance on the
establishment, growth, and reproductive output of Senecio sylvaticus and Epilobium
paniculatum and to determine if the typical decline of Senecio sylvaticus in the third and
fourth growing seasons is prevented by these treatments. One treatment was fertilization
of plots; treated plots were fertilized with 300 kg of N, 11.9 kg P, and 22.6 kg K per
hectare. The other treatment was above-ground removal of interspecific competition
(community removal) or soil disturbance.
Community removal and soil disturbance had significant effects on many
production and reproduction variables for one or both species, whereas fertilizer had
minimal impact. For the site in its fourth growing season post-burning, which was
accidentally broadcast fertilized after project establishment, community removal and soil
disturbance significantly increased the above-ground biomass per square meter of Senecio on the site, but plant density was not significantly affected. In addition, community
removal and soil disturbance increased the estimated number of Senecio seeds per square
meter by over thirty times and increased the total number of pods per square meter by
over ten times on the same site. While community removal and soil disturbance response
variables were significantly different from the control, they were not significantly different
from each other.
On the site in its third growing season post-disturbance, the community removal
increased the density of fall Senecio seedlings, but densities plummeted by spring and in
the summer densities were at or near zero for all treatment combinations. The small
number of plants made it impossible to analyze the data. The very low density was typical
for Senecio growing on clearcuts in their third and subsequent seasons post-disturbance,
and experimental treatments were unable to reverse this trend.
On the site in its fourth growing season post-disturbance, Epilobium paniculatum
final density was unaffected by community removal and soil disturbance, but above-ground
biomass per square meter increased by at least five times. The estimated number
of seeds per square meter had five to ten times the mean for the control; however, a
significant treatment interaction prevented mean separation.
The site in its third growing season post-disturbance exhibited decreased fall,
spring, and summer Epilobium densities for the soil disturbance treatment, likely because
the treatment buried seeds on this site which had abundant on-site seed sources in the
previous season. The estimated number of seeds and total number of pods per square
meter increased several-fold for community removal and soil disturbance treatments.
Fertilization significantly increased above-ground biomass, but not by a great magnitude.
The goal of the greenhouse studies was to determine how height, biomass, and
reproductive output of Senecio and Epilobium vary with increasing intraspecific
competition. Separate pot experiments were conducted for each species at Forest
Research Laboratory's greenhouse at Oregon State University, Corvallis, Oregon from
March through September of 1993.
Epilobium above-ground biomass and below-ground biomass per plant were
significantly affected by density by large magnitudes. In addition, pots with one plant had more above-ground biomass and below-ground biomass than all remaining treatments.
Reproductive output per pot was largely plastic for Epilobium; it remained similar across
all densities for total number of pods per pot and seeds per pod. Pots with one plant had
more estimated number of seeds than remaining treatments, but the magnitude was small.
On a per-plant basis, there were significant differences with large magnitudes for seeds per
plant and mean number of pods per plant.
Senecio growth and reproduction were significantly affected by plant density. All
treatments were significantly different from each other for both above-ground biomass per
plant and below-ground biomass per plant, with a ten-fold increase as density dropped
from 10 to 1 plant per pot. However, above-ground and below-ground biomass per pot
were not significantly different, indicating that biomass exhibited a plastic response to
density.
All reproductive variables were significant for Senecio. The magnitude of
difference between plants in the lowest density pots and plants in the highest density pots
was 100 times for biomass of reproductive parts per plant and 137 times for seeds per
plant. Unlike Epilobium, Senecio reproductive output was also highly sensitive to density
for estimated seeds per pot, total fruits per pot, and seeds per fruit. The estimated number
of seeds per pot exhibited a 10-fold magnitude of difference between pots with one plant
when compared with pots with ten plants.
Thus, increasing intraspecific competition had a much greater effect on the total
reproductive output of Senecio than on Epilobium. Whereas Epilobium reproductive
output is independent of density (within the range of densities tested), Senecio does not
exhibit plasticity in reproductive output and output declines with increasing density. If
these results are mirrored in the field, then Senecio may produce the greatest number of
seeds when not densely colonizing a clearcut
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Biomass dynamics of dead Douglas-fir and western hemlock boles in mid-elevation forests of the Cascade Range
No full textThe rate and manner of bioniass loss from decomposing Douglas-fir and western hemlock boles in mid-elevation forests of the central Cascade Range were measured. Bole bark and wood were considered separately. Loss of bole wood due to respiration was measured by change in bole wood density. Loss of bole wood due to fragmentation - was measured by change in bole volume. Bole species, position (upright or prostrate), and diameter affected the rate of bole decomposition with regard to both fragmentation and respiration. Douglas-fir boles decomposed slower than western hemlock boles. For both species, upright boles decomposed faster than prostrate boles (k 0.031 yr versus 0.012 for Douglas-fir wood and k= 0.090 yr versus 0.021 for western hemlock wood). Fragmentation proceeded at a faster rate than respiration for both prostrate and upright Douglas-fir boles. Decomposing prostrate boles of western hemlock did not fragment. Upright western hemlock boles had substantial fragmentation losses. Seven to thirteen percent of the wood of an upright western hemlock bole was lost each year to fragmentation. The relationship between bole size and decomposition rate was complex. For upright boles, decomposition rates increased as bole diameter decreased. Prostrate boles showed no relationship between bole diameter and decomposition rate. Bark loss rates of prostrate boles were similar for both species (k= 0.02 yr). Upright boles lost their bark faster than prostrate boles (k 0.038 yr to 0.14). Bark was lost faster from small than large boles. The decomposition data for all boles were quite variable. A computer simulation model was built to attempt to examine the question of how the quantity and type of wood and bark of dead boles would vary in a Douglas-fir/western hemlock forest as the stand developed. No age trends were apparent from the model output. The amount and type of dead bole wood fluctuated within a given range which was determined by the stochastic fluctuations in annual mortality
