Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim study area, e...Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim study area, erosion by ephemeral streams shortly after the eruption disrupted the lateral continuity of the 270 to 300 cm-thick pumice deposit. Co-evolution of the surface- and ground-water systems in a low-relief, low-slope landscape allowed diffuse groundwater discharge from the banks of the evolving stream system. Accumulation of organic material from groundwater dependent ecosystems at these sites of discharge allowed peat deposits to form on gently sloping erosion surfaces cut into the pumice deposit. Following early stream incision, fine-grained, silt-rich deposits accumulated in valleys and contributed permeability barriers to the lateral migration of water in the pumice aquifer. Fens discharge from the pumice aquifer through gently sloping surfaces patterned after the slope of the erosion surface cut into the pumice deposit and overlain by approximately 1 m of peat on the sloping surface and alluvium or iron-cemented pumice overlain by alluvium at the toe of the slope. The predominant source of groundwater is snowmelt which infiltrates the pumice deposit during the freshet. However, shallow groundwater flow also takes place along permeable pathways in bedrock units. Locally, low volume discharge takes place along faults. The snowmelt-dependent hydrologic system that supports the fens of the Walker Rim study area occurs at elevations primarily above 1585 m.展开更多
Plinian pumice fall from the Holocene eruption of Mount Mazama in the Cascade volcanic arc is an unconfined, perched aquifer in south-central Oregon. The pumice aquifer provides near-surface groundwater storage that m...Plinian pumice fall from the Holocene eruption of Mount Mazama in the Cascade volcanic arc is an unconfined, perched aquifer in south-central Oregon. The pumice aquifer provides near-surface groundwater storage that maintains biologically diverse wetland environments. Wetland environments reflect post-eruption disruption of the once uniform pumice blanket by fluvial and lacustrine processes operating within the template of the pre-eruption landscape. In the 8.6 km<sup>2</sup> Round Meadow watershed the pumice aquifer interacts with a seasonally flooded meadow, fen, springs, and perennial stream. The laterally uniform, isotropic pumice aquifer is disrupted by flat-bottomed ephemeral stream valleys that drain to the seasonally flooded meadow. Surface water levels in the seasonally flooded meadow are controlled by a knickpoint developed on bedrock. The underlying aquifer is confined by a layer of glass-rich diatomaceous silt grading upward to organic-rich silt. Here, the aquifer is comprised of remnants of the pumice deposit, lag sand, and reworked pumice. The water level in the confined aquifer is maintained by recharge from the unconfined pumice aquifer following flow pathways beneath ephemeral stream valleys. The fen is developed on a down-thrown block of welded tuff and pre-eruption diatomaceous silt. Water levels in the fen are sensitive to inter-annual variations in precipitation. Low discharge, low temperature (5.0°C to 6.5°C), and low conductivity (30 to 50 μS/cm) springs appear to be fracture controlled and rising through welded tuff. Spring discharge and seepage through pumice from the welded tuff support perennial flow in the creek that also carries discharge from the seasonally flooded meadow when water levels are high enough to cross the knickpoint.展开更多
Many aquatic habitats in coastal Oregon have been impacted by historic land use practices that led to losses of in-stream wood and associated degraded fish habitats. Many of these streams are now bordered by stands of...Many aquatic habitats in coastal Oregon have been impacted by historic land use practices that led to losses of in-stream wood and associated degraded fish habitats. Many of these streams are now bordered by stands of dense second growth forests（30–80 years） that are incorporated into riparian buffer zones with low wood recruitment and storage. Thinning in riparian zones is one management option to increase the rate of large tree growth and eventually larger in-stream wood, however, it raises concern about impacts on current wood recruitment, among other issues. Using a forest growth simulation model coupled to a model of in-stream wood recruitment, we explore riparian management alternatives in a Douglas-fir plantation in coastal Oregon. Alternatives included：（1） no treatment,（2） single and double entry thinning, without and with a 10-m buffer, and（3） thinning combined with mechanical introduction of some portion of the thinned trees into the stream（tree tipping）. Compared to no treatment, single and double entry thinning on one side of a channel, without a 10-m buffer, reduce cumulative instream wood volume by 33 and 42 %, respectively, after100 years（includes decay）. Maintaining a 10-m buffer reduces the in-stream wood loss to 7 %（single entry thin）and 11 %（double entry）. To completely offset the losses of in-stream wood in a single entry thin（on one or both sides of the stream）, in the absence or presence of a 10-m buffer,requires a 12–14 % rate of tree tipping. Relative to the notreatment alternative, cumulative in-stream wood storage can be increased up to 24 % in a double-entry thin with no buffer by tipping 15–20 % of the thinned trees（increased to 48 % if thinning and tipping simultaneously on both sides of the stream）. The predicted increases in in-stream wood that can occur during a thin with tree tipping may be effective for restoring fish habitat, particularly in aquatic systems that have poor habitat conditions and low levels of in-stream wood due to historic land use activities.展开更多
We studied the phase diagram Oregonator oscillator and calculated a chaos, R=0.1065, ω= 1. 25663706 and its dimensions D_c= 2.3746. We also studied the changes of f value from the stable state to the unstable.
Cob is an earthen building material comprised of sand,clay,straw,and water used for millennia to construct dwellings.Although cob construction largely died out during the nineteenth century,it is experiencing a reviva...Cob is an earthen building material comprised of sand,clay,straw,and water used for millennia to construct dwellings.Although cob construction largely died out during the nineteenth century,it is experiencing a revival in England and the Pacific Northwest of the United States.Little scientific research has investigated the engineering properties of cob,knowledge of which is important for modern-day design practices and code requirements.Researchers at Oregon State University investigated six different Oregon cob mixtures using a series of standard soils and concrete tests adapted for this material.The objectives were to characterize the constituents,to establish estimates for the magnitude of,and degree of variability in,the mixture properties,and to develop correlations between the engineering properties and mixture composition.Results indicated low to moderate variation in basic mixture properties(i.e.,unit weight,moisture content,and sand equivalent),moderate variation in strength properties,and high variation in the elastic modulus.Several reasonable correlations were found between shrinkage,compressive strength,elastic modulus,and sand equivalent and between flexural strength and fiber tensile strength.展开更多
文摘Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim study area, erosion by ephemeral streams shortly after the eruption disrupted the lateral continuity of the 270 to 300 cm-thick pumice deposit. Co-evolution of the surface- and ground-water systems in a low-relief, low-slope landscape allowed diffuse groundwater discharge from the banks of the evolving stream system. Accumulation of organic material from groundwater dependent ecosystems at these sites of discharge allowed peat deposits to form on gently sloping erosion surfaces cut into the pumice deposit. Following early stream incision, fine-grained, silt-rich deposits accumulated in valleys and contributed permeability barriers to the lateral migration of water in the pumice aquifer. Fens discharge from the pumice aquifer through gently sloping surfaces patterned after the slope of the erosion surface cut into the pumice deposit and overlain by approximately 1 m of peat on the sloping surface and alluvium or iron-cemented pumice overlain by alluvium at the toe of the slope. The predominant source of groundwater is snowmelt which infiltrates the pumice deposit during the freshet. However, shallow groundwater flow also takes place along permeable pathways in bedrock units. Locally, low volume discharge takes place along faults. The snowmelt-dependent hydrologic system that supports the fens of the Walker Rim study area occurs at elevations primarily above 1585 m.
文摘Plinian pumice fall from the Holocene eruption of Mount Mazama in the Cascade volcanic arc is an unconfined, perched aquifer in south-central Oregon. The pumice aquifer provides near-surface groundwater storage that maintains biologically diverse wetland environments. Wetland environments reflect post-eruption disruption of the once uniform pumice blanket by fluvial and lacustrine processes operating within the template of the pre-eruption landscape. In the 8.6 km<sup>2</sup> Round Meadow watershed the pumice aquifer interacts with a seasonally flooded meadow, fen, springs, and perennial stream. The laterally uniform, isotropic pumice aquifer is disrupted by flat-bottomed ephemeral stream valleys that drain to the seasonally flooded meadow. Surface water levels in the seasonally flooded meadow are controlled by a knickpoint developed on bedrock. The underlying aquifer is confined by a layer of glass-rich diatomaceous silt grading upward to organic-rich silt. Here, the aquifer is comprised of remnants of the pumice deposit, lag sand, and reworked pumice. The water level in the confined aquifer is maintained by recharge from the unconfined pumice aquifer following flow pathways beneath ephemeral stream valleys. The fen is developed on a down-thrown block of welded tuff and pre-eruption diatomaceous silt. Water levels in the fen are sensitive to inter-annual variations in precipitation. Low discharge, low temperature (5.0°C to 6.5°C), and low conductivity (30 to 50 μS/cm) springs appear to be fracture controlled and rising through welded tuff. Spring discharge and seepage through pumice from the welded tuff support perennial flow in the creek that also carries discharge from the seasonally flooded meadow when water levels are high enough to cross the knickpoint.
基金supported by the U.S.Forest Service,Pacific Northwest Research Station and Earth Systems Institute,Seattle Washington
文摘Many aquatic habitats in coastal Oregon have been impacted by historic land use practices that led to losses of in-stream wood and associated degraded fish habitats. Many of these streams are now bordered by stands of dense second growth forests（30–80 years） that are incorporated into riparian buffer zones with low wood recruitment and storage. Thinning in riparian zones is one management option to increase the rate of large tree growth and eventually larger in-stream wood, however, it raises concern about impacts on current wood recruitment, among other issues. Using a forest growth simulation model coupled to a model of in-stream wood recruitment, we explore riparian management alternatives in a Douglas-fir plantation in coastal Oregon. Alternatives included：（1） no treatment,（2） single and double entry thinning, without and with a 10-m buffer, and（3） thinning combined with mechanical introduction of some portion of the thinned trees into the stream（tree tipping）. Compared to no treatment, single and double entry thinning on one side of a channel, without a 10-m buffer, reduce cumulative instream wood volume by 33 and 42 %, respectively, after100 years（includes decay）. Maintaining a 10-m buffer reduces the in-stream wood loss to 7 %（single entry thin）and 11 %（double entry）. To completely offset the losses of in-stream wood in a single entry thin（on one or both sides of the stream）, in the absence or presence of a 10-m buffer,requires a 12–14 % rate of tree tipping. Relative to the notreatment alternative, cumulative in-stream wood storage can be increased up to 24 % in a double-entry thin with no buffer by tipping 15–20 % of the thinned trees（increased to 48 % if thinning and tipping simultaneously on both sides of the stream）. The predicted increases in in-stream wood that can occur during a thin with tree tipping may be effective for restoring fish habitat, particularly in aquatic systems that have poor habitat conditions and low levels of in-stream wood due to historic land use activities.
文摘We studied the phase diagram Oregonator oscillator and calculated a chaos, R=0.1065, ω= 1. 25663706 and its dimensions D_c= 2.3746. We also studied the changes of f value from the stable state to the unstable.
文摘Cob is an earthen building material comprised of sand,clay,straw,and water used for millennia to construct dwellings.Although cob construction largely died out during the nineteenth century,it is experiencing a revival in England and the Pacific Northwest of the United States.Little scientific research has investigated the engineering properties of cob,knowledge of which is important for modern-day design practices and code requirements.Researchers at Oregon State University investigated six different Oregon cob mixtures using a series of standard soils and concrete tests adapted for this material.The objectives were to characterize the constituents,to establish estimates for the magnitude of,and degree of variability in,the mixture properties,and to develop correlations between the engineering properties and mixture composition.Results indicated low to moderate variation in basic mixture properties(i.e.,unit weight,moisture content,and sand equivalent),moderate variation in strength properties,and high variation in the elastic modulus.Several reasonable correlations were found between shrinkage,compressive strength,elastic modulus,and sand equivalent and between flexural strength and fiber tensile strength.
