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1

Digitale Medien

Decomposition of standing dead trees in the southern Appalachian Mountains (1982)

Harmon, Mark E.

Springer

Oecologia 52 (1982), S. 214-215

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ISSN: 1432-1939

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Decomposition of standing dead trees that were killed by fire was examined for 10 species in the Great Smoky Mountains National Park. The decrease in wood density as fire age increased was used to estimate decomposition rates. Quercus prinus had the fastest decay rate (11% yr-1) while Pinus virginiana had the slowest decay rate (3.6% yr-1) for standing dead wood. Decay rates were intermediate between those reported in western USA and tropics for wood.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00363839

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2

Digitale Medien

Plant-pest interactions in time and space: A Douglas-fir bark beetle outbreak as a case study (1999)

Powers, Jennifer Sarah ; Sollins, Phillip ; Harmon, Mark E. ; [weitere]

Springer

Landscape ecology 14 (1999), S. 105-120

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ISSN: 1572-9761

Schlagwort(e): bark beetle epidemic ; Douglas-fir ; hierarchy theory ; multiple spatial and temporal scales

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract A conceptual model of Douglas-fir bark beetle (Dendroctonus pseudotsugae) dynamics and associated host tree mortality across multiple spatial and temporal scales was developed, then used to guide a study of the association between the occurrence of beetle- killed trees and factors that might render trees more susceptible to attack. Long-term records of beetle kill showed that beetle epidemics were associated with windstorms and drought at statewide and local spatial scales. At the landscape scale, beetle kill was associated with (i) portions of the landscape that were potentially drier (southern aspects, lower elevations) and (ii) portions of the landscape that had more mature and old-growth conifer vegetation. The patches of beetle-killed trees were aggregated with respect to other patches at scales of approximately 1 and 4 km. At the scale of the individual tree, there was not a strong relationship between beetle kill and resistance to attack measured by tree growth rate prior to attack. Our results show that landscape-scale phenomena and temporal patterns were more strongly correlated with beetle-kill events than was recent growth history at the scale of individual trees. We suggest that the multi-scale approach we employed is useful for elucidating the relative roles of fine- versus coarse-scale constraints on ecological processes.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1008017711917

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3

Digitale Medien

Firewood-gathering impacts in backcountry campsites in Great Smoky Mountains national park (1982)

Bratton, Susan P. ; Stromberg, Linda L. ; Harmon, Mark E.

Springer

Environmental management 6 (1982), S. 63-71

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ISSN: 1432-1009

Quelle: Springer Online Journal Archives 1860-2000

Thema: Energietechnik

Notizen: Abstract The effects of human trampling and firewood gathering on eight backcountry campsites in the Great Smoky Mountains were surveyed. Sample plots were classified as sitecenter, transition, firewood-gathering area, and control. The canopy in the center of the sites tended to be more open than that of control plots, with the greatest openings occurring at shelter sites in spruce-fir forest. Intensive human trampling in the center of the sites inhibited reproduction of tree species, whereas firewood gathering alone did not. In some cases where canopy opening had occurred, there was an increase in shrub and tree reproduction around the edge of the site. Reduction in the basal area of standing deadwood varied with the type of site; older growth stands were less depleted. Injuries to trees increased tenfold from control areas to the center of the campsites. Smaller fuels were more strongly impacted by trampling and little impacted by firewood gathering. Woody fuels in the 2.5- to 7.6-cm size class were preferred for firewood. A previously constructed carbon cycling model was modified to incorporate removal of firewood and litter on campsites. The model suggested that after extended removal of leaf litter, soil carbon takes 12 to 50 years to recover, but this hypothesis remains to be tested in the field.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01866808

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4

Digitale Medien

Modeling carbon stores in Oregon and Washington forest products: 1900–1992 (1996)

Harmon, Mark E. ; Harmon, Janice M. ; Ferrell, William K. ; [weitere]

Springer

Climatic change 33 (1996), S. 521-550

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ISSN: 1573-1480

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Physik

Notizen: Abstract A new model, FORPROD, for estimating the carbon stored in forest products, considers both the manufacture of the raw logs into products and the fate of the products during use and disposal. Data for historical patterns of harvest, manufacturing efficiencies, and product use and disposal were used for estimating the accumulation of carbon in Oregon and Washington forest products from 1900 to 1992. Pools examined were long- and short-term structures, paper supplies, mulch, open dumps, and landfills. The analysis indicated that of the 1,692 Tg of carbon harvested during the selected period, only 396 Tg, or 23%, is currently stored. Long-term structures and landfills contain the largest fraction of that store, holding 74% and 20%, respectively. Landfills currently have the highest rates of accumulation, but total landfill stores are relatively low because they have been used only in the last 40 years. Most carbon release has occurred during manufacturing, 45% to 60% lost to the atmosphere, depending upon the year. Sensitivity analyses of the effects of recycling, landfill decomposition, and replacement rates of long-term structures indicate that changing these parameters by a factor of two changes the estimated fraction of total carbon stored less than 2%.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00141703

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5

Digitale Medien

Water balance of conifer logs in early stages of decomposition (1995)

Harmon, Mark E. ; Sexton, Jay

Springer

Plant and soil 172 (1995), S. 141-152

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ISSN: 1573-5036

Schlagwort(e): coarse woody debris ; evaporation ; interception ; leaching ; runoff

Quelle: Springer Online Journal Archives 1860-2000

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract Seasonal and long-term changes in the water balance of conifer logs during the first 8 years of decomposition were studied in an old-growth Pseudotsuga/Tsuga forest in the Oregon Cascade Mountains. Measurements were made of the moisture content of outer bark, inner bark, sapwood, and heartwood and of the flow of water into and out of logs of four species (Abies amabilis, Pseudotsuga menziesii, Thuja plicata, and Tsuga heterophylla). After the logs had decomposed from 1 to 2 years, 38–47% of the canopy throughfall landing upon them ran off the surface, 29–34% leached from the bottom, and 21–30% was absorbed and evaporated. After 8 years of decomposition, water entering and then leaching from logs increased 1.3 times while runoff decreased a similar amount. The proportion of water stored by and evaporated from logs in this study indicates that in old growth forests they may intercept 2–5% of the canopy throughfall to the forest floor and that, even in early stages of decomposition, they may affect the hydrological cycle of Pacific Northwest old-growth forests.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00020868

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6

Digitale Medien

Potential response of pacific northwestern forests to climatic change, effects of stand age and initial composition (1993)

Urban, Dean L. ; Harmon, Mark E. ; Halpern, Charles B.

Springer

Climatic change 23 (1993), S. 247-266

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ISSN: 1573-1480

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Physik

Notizen: Abstract We used an individual-based forest simulator (a gap model) to assess the potential effects of anthropogenic climatic change on conifer forests of the Pacific Northwestern United States. Steady-state simulations suggested that forest zones could be shifted on the order of 500–1000 m in elevation, which could lead to the local extirpation of some high-altitude species. For low-elevation sites, species which currently are more abundant hundreds of kilometers to the south would be favored under greenhouse scenarios. Simulations of transient responses suggested that forest stands could show complex responses depending on initial species composition, stand age and canopy development, and the magnitude and duration of climatic warming. Assumptions about species response to temperature, which are crucial to the model's behaviors, were evaluated using data on species temperature limits inferred from regional distributions. The high level of within-species variability in these data, and other confounding factors influencing species distributions, argue against over-interpreting simulations. We suggest how we might resolve critical uncertainties with further research.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01091618

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7

Digitale Medien

Acetylene reduction in conifer logs during early stages of decomposition (1993)

Griffiths, Robert P. ; Harmon, Mark E. ; Caldwell, Bruce A. ; [weitere]

Springer

Plant and soil 148 (1993), S. 53-61

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ISSN: 1573-5036

Schlagwort(e): acetylene reduction ; conifer log ; coarse woody debris ; decay ; decomposition

Quelle: Springer Online Journal Archives 1860-2000

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract Acetylene reduction was examined periodically for as long as 68 months in the outer and inner bark, sapwood, and heartwood of decaying logs of western hemlock [Tsuga heterophylla (Raf.) Sarg.] western redcedar (Thuja plicata D. Don), Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco], and Pacific silver fir (Abies amabilis Dougl. ex Forbes) in the western Oregon Cascade Mountains. Tissues from freshly cut logs from sound trees were unable to reduce acetylene. However, after 18 months of decomposition, acetylene reduction was found in all log tissues except heartwood. Over the 68-month study period, no significant relationship between reduction rate and tissue moisture was found. Acetylene reduction rates differed significantly among tissues, log species, and time of exposure to decomposers. Although acetylene reduction generally showed a steady increase with time, tissues of some species showed a more complex, nonlinear pattern of change. Although the amount of nitrogen fixed is low compared to the total present in decaying logs, it might be an important source of readily available nitrogen for the microbiota responsible for decomposition.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02185384

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