Treesearch

Abstract - Sediment transport capacity mediates the transfer and storage of bed material between alluvial reservoirs in a drainage system. At intermediate time scales corresponding to the evolution of sediment pulses, conditions governing bed-material transport capacity under the hydrologic regime respond to variations in storage and sediment flux as pulses extend, overlap, and attenuate through the network. Relations between transport and storage in degrading gravel-bed channels and general relations between bed-load transport rate and tractive force have similar inflection points marking...

Abstract - Channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low-order streams, to understand the temporal succession of channel morphology following disturbance, and to make inferences about processes associated with input and transport of sediment. Dendrochronology was used to estimate the time since the previous debris flow and the time since the last stand-replacement fire in unlogged basins in the central Coast Range of Oregon. Debris flow activity increased 42 per cent above the background...

Abstract - Large wood recruitment and redistribution mechanisms were investigated in a 3.9 km 2 basin with an old-growth Pseudotsuga menziesii (Mirb.) Franco and Tsuga heterophylla (Raf.) Sarg. Forest, located in the southern Coast Range of Oregon. Stream size and topographic setting strongly influenced processes that delivered wood to the channel network. In small colluvial channels draining steep hillslopes, processes associated with slope instability dominated large wood recruitment. In the larger alluvial channel, windthrow was the dominant recruitment process from the local riparian...

Abstract. Human-caused fragmentation of habitats is threatening an increasing number of animal and plant species, making an understanding of the factors influencing patch occupancy ever more important. The overall goal of the current study was to develop probabilistic models of patch occupancy for the mountain yellow-legged frog (Rana muscosa). This once-common species has declined dramatically, at least in part as a result of habitat fragmentation resulting from the introduction of predatory fish. We first describe a model of frog patch occupancy developed using semiparametric logistic...

A macro time-series model and a micro GIS model were used to estimate a production function relating deer harvest response to prescribed fire, holding constant other environmental variables. The macro time-series model showed a marginal increase in deer harvested of 33 for an increase of 1,100 acres of prescribed burn. The marginal deer increase for the micro GIS model was 16. An additional 3,710 acres of prescribed burn would produce an additional eight deer harvested regardless of the model. For an additional 3,700 acres more of prescribed burn the marginal increase in deer harvested is...

On a poor site in northern California, a mature brushfield was treated in various ways that left initial density categories of light, medium, and heavy shrubs. Density, foliar cover, and height of seven shrub species (alone and combined) and ponderosa pine seedlings in these categories were quantified from 1967 through 1978. Heretofore, density and development data for five of the seven shrub species were unavailable. From the beginning to the end of the study, vegetation in the plantation was subjected to damage from insects, disease, snow, wind cupping, winterburn, a parasitic vine...

ABSTRACT.—To determine the response of Mountain Yellow-Legged Frogs to short distance translocations, I placed transmitters on 20 adult frogs and moved them short distances from 144–630 m and monitored their responses for up to 30 days. Of the 20 translocated frogs, seven frogs returned to their original capture site, four frogs moved in the direction of their capture site but had not returned by the end of the study, and nine frogs did not return and were found at the translocation site. Apparently, displacing frogs was stressful, and translocated frogs lost body mass during the study...

Recent advances in earth system sciences have revealed significant new information relevant to rare plant ecology and conservation. Analysis of climate change at high resolution with new and precise proxies of paleotemperatures reveals a picture over the past two million years of oscillatory climate change operating simultaneously at multiple timescales. Low-frequency oscillations are paced by cycles of the earth’s orbit around the sun and the resulting solar heat that earth receives. These control multi-millennial cycles of glacial (~90,000 year) and interglacial (~10,000 year – the...

The genus Martes is circumboreal in distribution, with extensions into southern (M. gwatkinsii) and southeast Asia as far as 7°S latitude (M. flavigula; Anderson 1970). The fisher (subgenus Pekania) is endemic to the New World and restricted to mesic coniferous forest of the boreal zone and its southern peninsular extensions (Hagmeier 1956; Gibilisco 1994). The boreal forest martens, comprising four sibling species (M. martes, M. zibellina, M. melampus, M americana), are distributed parapatrically or allopatrically across the boreal zone from Ireland eastward across Eurasia to North...

The Nantucket pine tip moth, Rhyacionia frustrana (Comstock), an important pest of intensively-managed loblolly pine, Pinus taeda L., was first noted in the scientific literature in 1879. This pest gained notoriety with the establishment of loblolly pine monocultures throughout the southeastern United States during the 1950s. Current intensive forest management practices have led to increasing interest in managing this insect. Herein we review all Nantucket pine tip moth literature (1879-2002) by addressing the following subjects: biology and life history, natural enemies, sampling...