Author: Nicholas T. Dosch Publisher: ISBN: Category : Carbon cycle (Biogeochemistry) Languages : en Pages : 107
Book Description
We examined the spatial and temporal variability of stream carbon dioxide (CO2) and the drivers of these variations in a headwater catchment. To examine temporal variation and drivers, we measured stream and hyporheic pCO2 at high temporal resolution over 11 months in a 95.9-ha forested headwater catchment in the Western Cascades of Central Oregon, USA. Stream and hyporheic pCO2 showed high seasonal and event-scale variability with distinct stream and hyporheic dynamics during storm discharge events. Hyporheic exchange flow exported 37.5 kg-C yr−1 per watershed hectare (confidence interval 4.0-122.3 kg-C ha−1 yr−1) from the riparian zone to the stream. Summing CO2 evasion and downstream advection suggests that one third of inorganic carbon export originated in the hyporheic zone. Hyporheic exchange flow had greatest influence over stream pCO2 during low and high baseflow, while CO2 evasion had greatest influence during storm discharge events. These findings suggest that the hyporheic zone actively participates in carbon cycling in this headwater stream and continuously replenishes stream CO2. To examine spatial variation and drivers, we measured stream CO2 at monthly intervals from July 2013 through July 2014 at 38 locations across the 6400-ha HJ Andrews Experimental Forest. Stream pCO2 was consistently supersaturated with respect to atmospheric concentrations. Stream pCO2 ranged from atmospheric (~400 [micro]atm) to 20 times atmospheric concentrations (8150 [micro]atm) and exhibited strong spatial and temporal variability. The distribution of pCO2 over the study period was different in small and large streams within the drainage network. At the watershed scale, pCO2 decreased with distance downstream. At the reach scale, we did not detect clear patterns in the downstream direction. However, individual transects displayed persistent profile shape, with consistent high and low pCO2 locations. We found negative relationships between stream pCO2 and stream discharge, mean velocity and the carbon dioxide gas transfer velocity. Stream pCO2 exhibited changes over short distances, with large changes in pCO2 over less than 50 m. Longitudinal variability indicates spatial variability of in-stream controls on pCO2 at this scale. Stream pCO2 shows generally higher concentrations during the summer and lower concentrations in the winter, with considerable intrannual variability.
Author: Matthew J. Kaylor Publisher: ISBN: Category : Fish culture Languages : en Pages : 0
Book Description
Humans have drastically altered the physical habitat and food web structure of stream ecosystems. Two major impacts humans have had on Pacific Northwest streams are modification of streamside forests (as a result of agriculture, land development, and timber harvest), and declines in the return of wild anadromous salmon to headwater ecosystems (due to a range of habitat degradation, dams, harvest, and hatcheries). Riparian forest impacts have altered stream light dynamics, while the loss of salmon has led to declines in the delivery of nutrients from the ocean to streams. While the initial impacts of the modifications took place decades or even centuries ago, they can have lasting effects on stream ecosystems and food webs. This dissertation evaluates 1) influences of long-term recovery from historic riparian harvesting on stream light, habitat, and food webs, and 2) how reduced salmon subsidies to streams may be impacting stream productivity and food webs. Today most streams in the Pacific Northwest, and indeed across much of North America, have buffers of riparian forests that are regenerating from earlier land clearing. As stands recover, the trajectories of stand development will affect forest structure, which in turn affects stream light regimes. In the first half of my dissertation, I explore how stand age and structure relates to stream light availability and then how spatial differences and temporal changes in stream light influence stream food webs and higher trophic level biomass in headwater streams. In Chapter 2, I explore how stream light availability differs with the age and stage of riparian forests. I found that stream light flux was generally lower and less variable when bordered by second-growth forests compared to old-growth forests within a stream network and more broadly across forests west of the Cascade Mountains. Numerous studies have evaluated how large differences in light availability (e.g. fully forested compared to complete removal of riparian forests) influence stream food webs, but smaller differences in light availability, such as those found in Chapter 2, have received less consideration. In Chapter 3, I conducted surveys across 18 stream reaches and evaluated how variables associated with stream habitat, light, primary production, and macroinvertebrate biomass account for variability in the biomass of cutthroat trout and total vertebrates (fish and salamanders). Habitat metrics were not well correlated with higher trophic level biomass. In contrast, factors associated with resource availability -- as regulated through bottom-up, autotrophic pathways -- were closely related to the biomass of fish and other consumers. In Chapter 4, I quantified long-term responses of stream biota to the regeneration of riparian forests following clear-cut harvest. I resampled five stream reach pairs that were originally sampled in 1976 shortly after canopy removal. This initial survey showed that periphyton chlorophyll a, predatory invertebrate biomass, and cutthroat trout (Oncorhynchus clarkii clarkii) biomass were elevated in harvested reaches relative to reference reaches. After four decades of riparian regeneration, mean canopy openness, chlorophyll a, predatory invertebrate biomass, and cutthroat trout biomass declined in harvested reaches relative to paired old-growth reference reaches. Changes in canopy cover were consistent with biotic responses and suggest that changes in light availability as stands regenerated exerted control on biota through bottom-up pathways in these streams. While spatial and temporal light dynamics appear as important regulators of stream food webs in small forested streams of western Oregon, other factors may emerge as important constraints on food web productivity across stream networks in other regions. In the second half of my dissertation, I explore bottom-up drivers of fish production in a river network in eastern Oregon where canopies are more open than small western Oregon streams. I focus on nutrient and carbon subsides in this study as the loss of returning anadromous fish has been hypothesized as a key factor contributing to poor recovery of ESA-listed salmonids. In chapter 5, I evaluate network-scale spatial patterns of primary production, potential drivers of primary production, and juvenile salmonid abundance throughout two NE Oregon sub-basins. Primary production rates increased with watershed area and we were able to explain 72% of the variation in primary production across these basins using a combination of fixed-effects (e.g. light, nutrients, and temperature) and spatial autocorrelation. In contrast to other studies, juvenile salmonid abundance was greatest in cool headwaters where nutrient concentrations and rates of primary production were very low. To test the hypothesis that growth of juvenile salmonids and other biota in these low-productivity stream sections may be inhibited by the reduction of returning adult salmon and the associated loss of nutrient subsidies, I conducted a carcasses addition experiment in three locations of the Upper Grand Ronde River. In chapter 6, I focused on the responses of juvenile Chinook (Oncorhynchus tshawytsca) and steelhead (O. mykiss). Chinook and steelhead consumed an abundance of eggs and carcass tissue which resulted in greater growth rates and body condition of fish in treatment reaches relative to controls. To contextualize potential effects of increased growth on Chinook survival, I used an 18 year tagging and detection dataset to evaluate Chinook length-survival relationships. The positive association between length and survival suggests that actions resulting in larger Chinook lead to increased survival rates. In chapter 7, I evaluate carcass addition effects on the broader food web. Periphyton, aquatic invertebrates, and non-salmonid fish assimilated carcass nitrogen, but enrichment was far less than observed in juvenile salmonids. In contrast to salmonids, diet analysis and stable isotope patterns indicated that non-salmonids were not consuming eggs and carcass material, suggesting carcass nitrogen assimilation occurred through bottom-up pathways. These results suggest that salmon subsidies have the potential to broadly impact stream food webs in this region, but that species able to directly consume eggs and carcass material (i.e. juvenile salmonids) clearly benefit more from these subsidies.
Author: Christine L. May Publisher: ISBN: Category : River sediments Languages : en Pages : 328
Book Description
Channels that were scoured to bedrock by debris flows provided unique opportunities to calculate the rate of sediment and wood accumulation, to make inferences about processes associated with input and transport of sediment, and to gain insight into the temporal succession of channel morphology following disturbance. In an intensive investigation of 13 channels the time since the previous debris flow was estimated using dendrochronology. The volume of wood in the channel was positively and linearly correlated with the time since the previous debris flow. The pattern of sediment accumulation was non-linear and appeared to increase as the storage capacity of the channel increased through time. Wood stored the majority of the sediment in these steep headwater streams, and landslides and wind throw were the dominant mechanisms for delivering wood to the channel. With an adequate supply of wood, small streams have the potential to store large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain. In an extensive investigation of 125 headwater streams, the spatial and temporal patterns of debris flow occurrence and deposition were investigated. The temporal distribution of debris flow occurrence varied with network structure and drainage area of the tributary basin. Network structure may affect the frequency of debris flows delivered to the mainstem river valley because it reflects the number of potential landslide source areas and the routing ability of the channel. Tributary basins with larger drainage areas and more convergent topography had a greater proportion of channels in the younger, post-debris flow age-classes compared to smaller basins with less convergent topography. The flux rate of material delivered to the confluence with the larger river also influenced the development of debris flow fans. Fans at the mouth of tributary basins with smaller drainage areas had a higher likelihood of being eroded in the interval between debris flows, while larger, more persistent fans were present at the mouth of bigger basins. Valley floor width of the mainstem river typically constrained fan development and was also an important predictor of fan size.
Author: Danielle D. Smith Publisher: ISBN: Category : Riparian plants Languages : en Pages : 338
Book Description
The role of riparian forests in maintaining temperatures of headwater streams is well established and is a foundation of forest practice rules designed to protect streamwater quality. However, detailed investigation is still needed quantifying specific characteristics of stream systems that affect streamwater temperature including riparian features, stream morphology, and subsurface interactions. The objectives of this research were to investigate summertime streamwater temperature patterns and identify characteristics within headwater streams and riparian zones that influence stream temperature. This study was designed to evaluate these relationships prior to logging in 38 perennial headwater catchments of the Oregon Coast Range. Stream reaches of greater than 1000 m were instrumented with temperature probes and selected stream and riparian characteristics were measured at 60-m intervals within each study reach in 2002 and 2003. A subset of the streams was examined in 2003 to determine the potential influence of streamwater residence time on temperature patterns. Findings suggest that canopy cover is the driving factor controlling summer stream temperature in these small headwater streams, but other stream and riparian characteristics should not be discarded. Longitudinal stream temperature patterns were quite variable for these forested streams and results suggest a high degree of complexity in small headwater streams. Maximum 7-day moving average temperatures ranged from 11.4°C to 16.8°C, with three streams above the standard 16°C threshold. Effects of stream and riparian characteristics on stream temperature were strongest when average of the weekly high temperature was assessed, suggesting this may be a more sensitive index of stream temperature than the commonly used maximum 7-day moving average. Results of tracer dilution tests were inconclusive in that temperature was not consistently correlated to residence time in streams.
Author: Cynthia L. Meays Publisher: ISBN: Category : Water temperature Languages : en Pages : 280
Book Description
A case study examining the relationship between stream temperatures and the thermal environment through which streams flow was conducted on the headwaters of 4 tributaries of the Burnt River (Barney, Elk, Greenhorn, and Stevens Creeks) in northeastern Oregon during July through August 1998 and 1999. Barney Creek and Stevens Creek are in adjacent drainages, both with northerly aspects. Barney Creek drainage was completely burned over in 1989 while Stevens Creek vegetation remained intact. Elk Creek had 2 cold water tributaries and groundwater inputs. Greenhorn Creek was much more variable in terms of disturbance and vegetation. Stream discharge and air, soil, and water temperature data were collected at 150 m increments from 1370 to 1830 m elevation on each stream. Analyses compared daily mean air, soil, and water temperatures at each elevation within each stream, year, and month. Mean daily minimum and daily maximum air and water temperatures were also analyzed. For all streams in this study. elevation was significantly associated with air, soil, and water temperatures (p
Author: Nicholas T. Dosch
Author: Asa Lovisa Viktoria Horgby
Author: Matthew J. Kaylor
Author: Christine L. May
Author: Fransiska Kate Dannemann
Author: Danielle D. Smith
Author: Ryan J. MacDonald
Author: Robert Speaker
Author: Cynthia L. Meays
Author: Oregon. Department of Geology and Mineral Industries