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Stream Temperature Change Detection for State and Private Forests in the Oregon Coast Range
Abstract
Oregon's forested coastal watersheds support important cold-water fisheries of salmon and steelhead (Oncorhynchus spp.) as well as forestry-dependent local economies. Riparian timber harvest restrictions in Oregon and elsewhere are designed to protect stream habitat characteristics while enabling upland timber harvest. We present an assessment of riparian leave tree rule effectiveness at protecting streams from temperature increases in the Oregon Coast Range. We evaluated temperature responses to timber harvest at 33 privately owned and state forest sites with Oregon's water quality temperature antidegradation standard, the Protecting Cold Water (PCW) criterion. At each site we evaluated stream temperature patterns before and after harvest upstream, within, and downstream of harvest units. We developed a method for detecting stream temperature change between years that adhered as closely as possible to Oregon's water quality rule language. The procedure provided an exceedance history across sites that allowed us to quantify background and treatment (timber harvest) PCW exceedance rates. For streams adjacent to harvested areas on privately owned lands, preharvest to postharvest year comparisons exhibited a 40% probability of exceedance. Sites managed according to the more stringent state forest riparian standards did not exhibit exceedance rates that differed from preharvest, control, or downstream rates (5%). These results will inform policy discussion regarding the sufficiency of Oregon's forest practices regulation at protecting stream temperature. The analysis process itself may assist other states and countries in developing and evaluating their forest management and water quality antidegradation regulations.
... Dent et al. (2008) described pre-harvest RipStream riparian conditions and stream temperatures. Groom et al. (2011a) found an increased probability of PCW exceedance on privately-owned land. They did not find similar evidence on land managed by the state. ...
... The Oregon Board of Forestry (Board), whose decisions can alter the FPA, reviewed the findings from Groom et al. (2011a) and ruled that degradation of cold water had occurred on private lands (ODF, 2012). The ruling triggered a procedure (Oregon Revised Statutes 527.714 (5a); ODF, 2014) whose provisions required any alterations to existing rules reflect available scientific information, the results of relevant monitoring, the effectiveness of alternative strategies, and effectively mitigate the issue at hand. ...
... The analysis by Groom et al. (2011a) indicated that temperature increases above ODEQ threshold levels were occurring on privatelyowned timberland and Groom et al. (2011b) provided two models that linked temperature change within a reach to shade [1], and shade values post-harvest to basal area and tree height. Combining the two analyses of temperature-shade and shade-site factors in a Bayesian hierarchical model allows for the direct prediction of temperature responses from different simulated harvests of the vegetation plot data. ...
In 2012 the Oregon Board of Forestry (Board) determined that current forestry rules were insufficient at preventing the degradation of cold water in salmonid-bearing streams. Consequently, the Oregon Department of Forestry required a means for evaluating and comparing the effectiveness of newly-proposed harvest scenarios. We derived a field-data based method for simulating riparian harvest and modeling the resulting effects on stream temperature that could be used for evaluating different harvest scenarios. We simulated prescribed harvests by using previously-collected riparian stand data. To create a predictive model, we modified and joined two earlier stream temperature and shade models from Groom et al. (2011b) into a Bayesian hierarchical model. The predictive model produced parameter estimates and temperature change metrics that aligned with the previous findings. The model predicted that harvest according to a full implementation of the State forest harvest plan would on average result in a 0.19 °C increase, while the model predicted that a similarly-scaled harvest to current private forest regulation specifications would lead to an average increase of 1.45 °C. Further simulations suggested that employing a no-cut slope-distance riparian zone of 27.4 m would result in average warming below 0.3 °C of unharvested conditions. The Board considered these results along with other information and directed the Oregon Department of Forestry to develop harvest rule revisions. Those revisions became effective as of July 2017.
... The FMP prescribes three management zones for small and medium streams, measured as distance from the stream's bankfull width edge: an 8 m no-harvest zone adjacent to the stream, a middle zone from 8 to 30 m that is only entered to advance the stand toward a mature forest condition, and an outer zone, from 30 to 51 m in which harvest intensity depends on riparian stand characteristics (ODF, 2001). At RipStream sites, mean buffer widths for State and private sites ranged from 25 to 61 m and 19 to 41 m, respectively (Groom et al., 2011a). ...
... Groom et al. (2011b) performed a programmatic evaluation of site stream temperatures relative to the Protecting Cold Water criterion and found that harvest on privately owned forests increased the frequency of criterion exceedances, while harvest on State-owned forests did not. Groom et al. (2011a) evaluated site characteristics associated with observed temperatures before and after harvest, and estimated the magnitude of stream temperature change related to harvest after controlling for site features. On privately owned sites, maximum stream temperatures increased on average 0.7°C (range = À0.9 to 2.5°C). ...
... Current forest harvest practices on State and private forests in western Oregon have resulted in smaller increases of temperature than occurred with historical forest practices (Levno and Rothacher, 1967;Brown and Krygier, 1970;Hewlett and Fortson, 1982). Groom et al. (2011a) found small average increases in maximum daily temperatures (mean increase for State sites = 0.0°C, private sites = 0.7°C). The magnitude of temperature exceedances was much smaller than following previous forest harvest activities, demonstrating a substantial improvement in protection of water quality during forest management. ...
... Clearcut logging without buffers reduces instream LWD loading over a long period (Ͼ100 years) Koski 1989, McHenry et al. 1998) and can increase stream temperature between 2.7 and 14.4°F (Meehan et al. 1969, Brown and Krygier 1970, Feller 1981, Rishel et al. 1982, Murray et al. 2000, Moore et al. 2005, Gomi et al. 2006, Janisch et al. 2012. In contrast, riparian buffers can limit temperature increases to between 0 and 2°F (Brown and Krygier 1970, Dent and Walsh 1997, Zwieniecki and Newton 1999, Gomi et al. 2006, Groom et al. 2011a, 2011b, Janisch et al. 2012. Riparian buffers have also been shown to reduce or eliminate reductions in LWD recruitment (Teply et al. 2007), although effects can be variable: short-term increases in LWD recruitment can occur due to windthrow along cut-block edges (Grizzel and Wolff 1998, Martin and Grotefendt 2007, Schuett-Hames et al. 2012, and if riparian buffers are too narrow, LWD recruitment is decreased (Grizzel et al. 2000). ...
... To validate simulated shade loss occurring from narrowing of the riparian buffers, we identified four riparian effectiveness monitoring projects conducted in the Pa-cific Northwest for which shade and adjacent stand data were reported (Eddie Cupp, Terrapin Environmental, pers. comm., July 25, 2012, Sugden and Steiner 2005, Groom et al. 2011a, 2011b, Janisch et al. 2012. Harvest operations used in these studies narrowed riparian buffers to 75 ft and/or 50 ft with minimal feathering (i.e., thinning of trees within the riparian buffer and/or retention of thinned trees outside the buffer). ...
... Riparian effectiveness monitoring studies of operational timber harvests in Washington (Eddie Cupp, Terrapin Environmental, pers. comm., July 25, 2012), Oregon (Groom et al. 2011a(Groom et al. , 2011b, and Montana (Sugden and Steiner 2005) all report residual stocking levels greater than required under their state rules. Although greater tree removal is allowed, operational considerations (e.g., the greater cost required to remove trees in near-stream equipment exclusion zones) are a key factor limiting riparian tree harvest. ...
Providing stream shade and woody debris, while also allowing for active management of riparian areas, is a nationwide challenge for meeting Clean Water Act requirements. This is a case study of developing simulation models to evaluate effectiveness of buffer strip prescriptions in meeting multiple objectives. It was conducted in Idaho, where a state forest practices act requires buffer strips as a best management practice. This approach could be applied in other states where riparian management practices are required as a matter of regulation or as voluntary practices and where forest inventory data are available for a range of forest stand conditions. Prescriptions were simulated on uncut stands and varied by the total width of the riparian buffer, widths of inner and outer zones within the riparian buffer, and residual stocking within each buffer zone. Simulation models were shown to account for fine-scale differences in riparian function produced by a series of prescriptions that were examined. Alternative riparian buffer prescriptions were evaluated, comparing their ability to meet four objectives: protection of aquatic resources, economic viability, silvicultural sufficiency, and the ability to operate throughout the riparian buffer. Potential impacts on stream shade were most constraining. We found that thinning throughout the buffer (i.e., up to the stream bank) and very narrow buffers (e.g., 50 ft or less) led to unacceptable decreases in shade. However, we also found that the portion of the stand immediately adjacent to the stream was very important to stream shade. Harvest restrictions in a stream-adjacent buffer could permit greater overall management flexibility. However, there still was the desire to operate throughout the buffer. We found that by thinning lightly in the inner 25-ft buffer zone, with heavier thinning in an outer 50-ft zone, these multiple objectives could be achieved. Similar principles underlie riparian forest practice regulations in other states (e.g., Washington and Oregon). However, use of our framework could permit development of fine-scale site-specific prescriptions or be used for rule revision, including consideration of near-stream harvest. Overall, simulation modeling allowed evaluation of a range of riparian prescriptions that would be impractical in a field experiment. In addition, simulation results form the basis for hypotheses to be tested through effectiveness monitoring.
... Only studies that employed a Before-After-Control-Impact design and conducted in Pacific Northwest forests are included. Bayesian modeling results (and 90% credible intervals) were derived from data collected as part of Groom et al. (2011). A change of 1°C is equivalent to a 1. ...
... Shade unit is percent from completely shaded. Bayesian modeling results (and 90% credible intervals) were derived from data collected as part ofGroom et al. (2011). Analyses provided by P. Leinenbach, USEPA Region 10.the time of hatching (i.e., duration of incubation) of salmonid eggs is largely determined by their thermal exposure during incubation. ...
This report contains reviews and syntheses of scientific literature for the purpose of informing the development of policies related to management of riparian areas and watersheds of Washington State.
... We focused on four key metrics that apply most directly to management regulations in quantifying the stream temperature responses to riparian canopy gaps. We first used the 15min data to calculate daily mean and daily maximum temperatures for each logger location for the same 40-day period (from July 22 to August 31) where we have consistent data at all locations during both years, and which typically encompasses the time of maximum temperatures in streams of this region (Groom et al., 2011a, Arismendi et al., 2013. ...
... Further, to visualize and quantify gap effects over the full 40-day survey period on daily temperature metrics, we used a regression approach to compare the relationships between reaches during each summer period to evaluate the difference in warming within the reference and treatment reaches between years. This approach treats the reference reach as the independent variable and the treatment reach as the dependent variable and has been used in multiple other temperature assessment studies to capture processes occurring over a summer season, rather than compressing data to a single value (Groom et al. 2011a, Kibler et al. 2013, Bladon et al. 2016). In each periodpre-and post-treatmentthe regressions evaluated the relationship between daily temperature (maximum and mean) at the downstream end (meter 90) of the reference reach and the downstream end of the treatment reach. ...
... We examined accuracy and precision by submerging nine of each logger model simultaneously into an isothermal water bath contained by a 38-L glass aquarium where the loggers remained submerged and free to circulate for the duration of this experiment. Loggers recorded temperature at one-minute intervals and were held for 10 minutes at each of eight target temperatures (5,10,15,20,25,30,35, and 40 °C). The 10-minute period was initiated after the reference thermometer had registered the target temperature for a period of several minutes. ...
... Our findings indicate the use of a variety of logger models in a study may alter the conclusions. Although the differences we detected between logger model measurements may seem small or biologically insignificant, these differences may be important in situations when a < 1 °C change in temperature has regulatory implications [5,6,25] or biological relevance such as near-freezing temperatures, initiation of reproductive and behavioral responses, or determination of thermal tolerance [26]. ...
Remote temperature loggers are often used to measure water temperatures for ecological studies and by regulatory agencies to determine whether water quality standards are being maintained. Equipment specifications are often given a cursory review in the methods; however, the effect of temperature logger model is rarely addressed in the discussion. In a laboratory environment, we compared measurements from three models of temperature loggers at 5 to 40 °C to better understand the utility of these devices. Mean water temperatures recorded by logger models differed statistically even for those with similar accuracy specifications, but were still within manufacturer accuracy specifications. Maximum mean temperature difference between models was 0.4 °C which could have regulatory and ecological implications, such as when a 0.3 °C temperature change triggers a water quality violation or increases species mortality rates. Additionally, precision should be reported as the overall precision (including a consideration of significant digits) for combined model types which in our experiment was 0.7 °C, not the ≤0.4 °C for individual models. Our results affirm that analyzing data collected by different logger models can result in potentially erroneous conclusions when <1 °C difference has regulatory compliance or ecological implications and that combining data from multiple logger models can reduce the overall precision of results.
... The pertinent information on field data collection for this analysis is described later. A full description of data collection and field protocols can be found in Groom et al. (2011b); also see Dent et al. (2008) for a map of the study area and full description of site selection criteria and Groom et al. (2011a) for a summary of the forest harvest reach site characteristics including channel and riparian vegetation statistics pre-harvest and post-harvest. The criteria for stream selection included no beaver influence (dams with ponds or disturbed vegetation), average annual flow rates of 283 l/s or less and treatment reaches harvested according to state and private forest prescriptions for fish-bearing streams, which require varying amounts of overstory tree retention depending on ownership and stream size. ...
... Shade was estimated by 1 À GSF, where GSF (global site factor) is the ratio of direct plus diffuse solar power below canopy to direct plus diffuse power above canopy. Further detail on the processing of these data is described in Groom et al. (2011a). ...
We adapted Newton's Law of Cooling to model downstream water temperature change in response to stream-adjacent forest harvest on small and medium streams (average 327 ha in size) throughout the Oregon Coast Range, USA. The model requires measured stream gradient, width, depth and upstream control reach temperatures as inputs and contains two free parameters which were determined by fitting the model to measured stream temperature data. This model reproduces the measured downstream temperature responses to within 0.4 C° for 15 of the 16 streams studied and provides insight into the physical sources of site-to-site variation among those responses. We also use the model to examine how the pre-to-post harvest change in daily maximum stream temperature depends on distance from the harvest reach. The model suggests that the pre-to-post harvest temperature change approximately 300 m downstream of the harvest will range from roughly 82% to less than 1% of that temperature change which occurred within the harvest reach, depending primarily on the downstream width, depth, and gradient. Using study-averaged values for these channel characteristics the model suggests that for a stream representative of those in the study, the temperature change approximately 300 m downstream of the harvest will be 56% of the temperature change which occurred within the harvest reach. This adapted Newton's Law of Cooling procedure represents a highly practical means for predicting stream temperature behavior downstream of timber harvests relative to conventional heat budget approaches, and is informative of the dominant processes affecting stream temperature. This article is protected by copyright. All rights reserved.
... However, the greatest proportion of harvests in the NWFP area occur as less intensive thinnings designed to meet ecological objectives consistent with late-successional or riparian reserve land designations. Two recent studies of stream temperature responses to harvest have demonstrated either increased buffer effectiveness with increased buffer width (Groom et al., 2011) or inconsistent effectiveness with varying longitudinal continuity of buffers (Janisch et al., 2012). While both of these studies provide useful information, the applicability to federal lands is compromised by context. ...
... While both of these studies provide useful information, the applicability to federal lands is compromised by context. The study of Groom et al. (2011) includes small and medium fish-bearing streams on private and state lands with 79% of the harvested study reaches being clearfelled. The study of Janisch et al. (2012) was conducted in western Washington in small headwater streams similar to those of the DMS, but again, the harvest activity adjacent to continuous buffer, patchy buffer or no buffer treatments was clearfelling. ...
The advent of the Northwest Forest Plan (NWFP) in the early 1990s signaled a new paradigm for management of 9.9 million ha of federal forest lands in western Washington and Oregon, USA. The emphasis shifted from commodity timber production to ensuring sustained ecological functioning to meet a broad array of ecosystem services including economic benefits. Under interim guidelines of the NWFP, approximately 1.1 million ha are allocated to riparian reserves intended to conserve the ecological functions and processes required to create and maintain habitat for aquatic and riparian-dependent organisms. The Density Management and Riparian Buffer Study (DMS), an operational-scale management experiment, has evaluated the effectiveness of alternative buffer widths in meeting ecological objectives for riparian areas in headwater forests subjected to spatially heterogeneous thinning. Observations in unthinned stream-reaches revealed spatial structuring of amphibian and invertebrate species assemblages in relation to headwater habitats. Riparian buffers defined by the transition between distinct riparian habitat features and upslope forest were sufficient to moderate the effect of thinning on near-stream microclimates and wetted streambed temperatures. These same variable-width buffers were less effective when adjacent to 0.4-ha patch openings. Thinning had little impact on the abundance of aquatic amphibians and there was no evidence of species loss. Results of the study are being used to devise headwater forest management and species conservation strategies, and to improve monitoring methods and watershed assessment tools.
... Of obvious importance is the width of the riparian reserve (BMP), which may need to be in excess of 30 m to provide adequate protection (e.g., Sweeney and Newbold 2014). In one Oregon study, 21-m buffers led to a summer (mid-July to mid-August) stream temperature increase of 0.7°C, on average, whereas buffers of 52 m had no impact on stream temperatures (Groom et al. 2011a(Groom et al. , 2011b. Across forest ownerships, BMPs vary in extent, both laterally and longitudinally, with the upper extent of channels typically receiving less protection (Adams 2007), and it is in these habitats where substantial watershed biological diversity resides (Meyer et al. 2007;Olson et al. 2007). ...
... In Oregon coastal streams, mean stream temperature tends to increase with distance downstream as a result of exposure of the stream surface to solar radiation and warmer air temperatures (Sullivan et al. 1990, Dent et al. 2008, Groom et al. 2011. However, other work has shown that for some streams, longitudinal trends in temperature are more complex (Fullerton et al. 2015(Fullerton et al. , 2018. ...
We evaluated commonly used methods for monitoring stream restorations to inform and improve restoration monitoring and evaluation, using a headwater stream in the Oregon Coast Range as a case-study example. In-stream restoration projects are seldom monitored both pre- and post-restoration. In addition, frequently used low-cost methods may not provide sufficient data to effectively assess trends in stream temperature. Here, we examined what can be learned from temperature loggers installed in the same locations over multiple years in a restored stream. In-stream structures were installed between 2007 and 2011 along a 10-km length of South Sister Creek, Oregon for the purpose of enhancing in-stream habitat. Summer stream temperature data were collected using Hobo Pro-V temperature-logging thermistors at four locations in 2006, prior to restoration, as well as in 2012 and 2013. In 2013, additional temperature loggers were placed within 80 m of the four original loggers to investigate within-reach variability. Although median stream temperatures were highest in 2013 at all four multi-year sites, 7-day maximum temperatures were 4 to 5 C cooler in post-treatment years than in 2006. Inter-annual variability in stream temperature was more closely linked to inter-annual variability in air temperature and solar radiation than presence of in-stream structures. Thermal heterogeneity was greater in reaches with deeper pools than in bedrock-dominated reaches. Although in-stream structures can create cool microhabitats, they have little influence on mean stream temperature. Longer pre-restoration monitoring and sensor deployment in more varied in-stream habitats would improve our ability to evaluate restoration impacts.
... Shade was best predicted by riparian basal area and tree height. In a separate paper, Groom et al (2011a) found that typical logging practices on private land generally caused streams to exceed water quality thresholds, but that recent management rules successfully lowered this probability greatly. ...
... Furthermore, 7-day moving max temperatures in Needle Branch (Fig. 4) were well within the optimum growth temperature range (13-15 • C) reported for westslope cutthroat trout (Oncorhynchus clarkii lewisi), another headwater subspecies of cutthroat trout (Oncorhynchus clarkii). Our findings are similar to other studies that have reported small increases in water temperatures following logging associated with current forest practice rules for private lands in Oregon (Oregon Department of Forestry, 2006;Groom et al., 2011;Bladon et al., 2018). ...
Research dating back to the 1950 s has documented negative effects from harvesting of primeval forests on stream ecosystems of the Pacific Northwest. By the early 1990 s, state and federal forest practice rules governing timber harvest were modified throughout North America to better protect aquatic habitats and biotic resources, principally salmonids. These rules inspired a generation of studies using a before-after-control-impact (BACI) design to document the capacity of contemporary timber harvest rules to protect salmonids in headwater streams of second-growth forests. One important unanswered question concerns the potential effects of successive clearcuts in second growth forests. Consequently, we used a paired watershed approach to evaluate the effects of two successive clearcut harvests in the Alsea Watershed, site of the seminal Alsea Watershed Study that was conducted from 1958 to 1973, on relative biomass, movement, survival, and distribution of coastal cutthroat trout (Oncorhynchus clarkii clarkii) and three physical habitat characteristics (pool area and depth, and water temperature). Although the total clearcut harvest encompassed 87% of the treatment catchment in six years, no negative effects of logging were detected for either age-1 + coastal cutthroat trout or habitat variables. Comparisons between the harvested and reference catchments suggested the survival of coastal cutthroat trout (>94 mm fork length) and total catchment relative biomass of age-1+ (i.e., > 80 mm) exhibited similar patterns, increasing from the pre-logging period (2006-2009) through the Phase I post-logging period (2009-2014), and decreasing to levels observed in the pre-logging period during the Phase II post-logging period (2014-2017). Additionally, there was no evidence for differences in movement of coastal cutthroat trout related to the harvesting treatment. In terms of habitat variables, there was a relative increase in annual total pool area in the harvested catchment during the Phase II post-logging period, but there was no evidence the 7-day moving mean maximum stream temperature changed after the Phase I and Phase II harvests. Moreover, stream water temperatures never exceeded the criterion designed to protect core coldwater habitat for salmonids (16 • C). As such, it is unlikely that cutthroat trout experienced thermal stress following either harvest. More generally, results from this and other recent studies suggest that forest practice rules developed in conjunction with current best management practices for logging in headwater catchments have substantially improved outcomes for stream biota relative to unregulated forest harvest, at least for short periods of time after logging (i.e., ≤ 8 years).
... The Oregon Department of Forestry's Riparian Function and Stream Temperature (RipStream) project provides a framework to evaluate the effectiveness of forest practices rules and strategies at protecting stream thermal conditions for fish and wildlife habitat. The RipStream project examines the effects of timber harvest on stream temperature pre-and post-harvest in 33 harvested reaches (Dent et al., 2008;Groom et al., 2011a;Groom et al., 2011b) and in a subset of unharvested downstream reaches (Davis et al., 2015). Specifically, Dent et al. (2008) describe pre-harvest spatial and temporal patterns of stream temperature. ...
Temperature is a fundamental driver of aquatic environments. Changes in thermal regimes due to timber harvest may be detrimental for cold-water instream biota. Although it is understood that stream temperature may increase immediately below timber harvest operations, the understanding of how thermal responses propagate
downstream is less clear. Here, we examine the effects of timber harvest on stream temperature pre (2–3 years) and post-harvest (5 years) at 16 sites (average annual streamflow rates <0.283 m3 s−1) located in the Coast Range, Oregon, USA. At each site, an array of temperature sensors were deployed on the extremes of three consecutive reaches: an upstream unharvested reference reach, a treatment reach, and a downstream unharvested reach.We used several metrics to describe and evaluate changes over time and space focusing on the responses of downstream reaches. Primarily, we evaluated the differences over time in daily maximum temperature
between the two sensors located at the downstream unharvested reach. Furthermore, using a statistical ordination technique, we examined the spatial and temporal variability of an array of sensors for daily maximum temperature.Moreover,we assessed distributional shifts (statistical moments) of hourly temperature differences
between the two sensors at the downstream unharvested reach over time. Lastly, we used a combination of statistical moments and the ordination technique to provide an index that describes the behavior of site-specific thermal disturbance over time.We found that stream reaches responded differently to upstream timber harvest operations between pre and post-harvest summer seasons. In addition, we showed distinct patterns of longitudinal variability of temperature across sites and summer seasons with increases, decreases or mixed responses including no change downstream. Overall, the net change of daily maximum temperature at the downstream reach revealed that the highest difference occurred during the first and second year post-harvest and, in some cases, a distinctive shift in streamwarming and cooling occurred between the day and the night. Observed temperature patterns in downstream reaches were most similar to the pre-harvest conditions at the fifth year post-harvest. Collectively, we offer a novel approach for assessing stream temperature regime change using multiple metrics that can improve our understanding of thermal effects downstream of timber harvest, taking in consideration
idiosyncratic responses across sites and time.
... Furthermore, 7-day moving max temperatures in Needle Branch (Fig. 4) were well within the optimum growth temperature range (13-15 • C) reported for westslope cutthroat trout (Oncorhynchus clarkii lewisi), another headwater subspecies of cutthroat trout (Oncorhynchus clarkii). Our findings are similar to other studies that have reported small increases in water temperatures following logging associated with current forest practice rules for private lands in Oregon (Oregon Department of Forestry, 2006;Groom et al., 2011;Bladon et al., 2018). ...
We used a paired-watershed approach to investigate the effects of contemporary logging practices on headwater populations of coastal cutthroat trout (Oncorhynchus clarkii clarkii) and juvenile coho salmon (Oncorhynchus kisutch) in a second-growth Douglas-fir forested catchment in Oregon. Stream habitat and fish population characteristics, including biomass, abundance, growth, size, and movement, were assessed over a 9-year period (4 years pre-and 5 years postlogging). The logged catchment was located on private industrial forestland and had been previously logged in 1966. The reference catchment was covered by an unharvested, fire-regenerated forest approximately 150-160 years old, which was unroaded and managed as a Research Natural Area by the USDA Forest Service. A single clearcut harvest unit of the upper 40% of the treatment catchment was implemented following current forest practice regulations, including the retention of riparian buffer of standing trees adjacent to fish bearing channels. No statistically significant negative effects on coastal cutthroat trout or coho salmon occurred following logging, and in fact, both late-summer density and total biomass of age-1+ coastal cutthroat trout increased in the logged catchment following logging. Increases in age-1+ coastal cut-throat were greatest closest to the harvest area and declined downstream as distance from the logged area increased. In contrast to the previous timber harvest in the catchment when few logging regulations existed, current forest practice regulations and logging techniques appear to have reduced acute negative effects on coastal cutthroat trout.
... For the mid-term fire effects, we used least squares regression with added autoregressive ('p') and moving average ('q') terms to evaluate stream temperature exceedances of observed stream temperature (Groom et al., 2011) from three sites in Willow and Whitehorse creeks (i.e. Whitehorse-01, Whitehorse-10, Willow-27; Fig. 2) against those predicted by the Little Blitzen River reference site. ...
... The study by Gravelle and Link (2007) was primarily focused on forest harvesting, the study by Snyder et al. (2015) focused on a two month summer period in the Appalachian Mountains, and the other two headwater network studies were conducted in glaciated environments Cadbury et al. 2008), hence their inference to other environments and seasons may be limited. A broader set of studies has been conducted on headwater catchments within the context of forest harvesting (Moore et al. 2005a;Anderson et al. 2007;Rykken et al. 2007;Groom et al. 2011); however, these studies were focused on the response to harvesting for individual reaches and did not consider thermal variability across headwater networks. ...
... PCWS in Oregon is an example of an ambient-based water quality standard [79]. The criteria in PCWS set a limit of 0.3°C for the allowed post-harvesting increase in stream temperatures in fish bearing water bodies when compared to natural reference temperatures that are typical to the area in question. ...
Forest policies have typically relied on prescriptive standards to mitigate various nonpoint negative externalities, whereas more recent approaches have focused on the use of incentive-based policies, such as payments for environmental services (PES), to encourage activities associated with positive externalities. We provide a general review on the current state of knowledge concerning prescriptive standards and incentive-based policies in the context of nonpoint and point source externalities that are typical in industrial and nonindustrial forestry. Our specific focus is on reviewing and assessing the current and future applications of performance bonding in forest policy. We argue that bonds can be viewed either as an enforcement mechanism to achieve compliance with standards, or alternatively, as a deposit-refund instrument that imposes a tax on harmful activities while subsidizing beneficial ones in the form of a refund. Four forest policy settings are considered: best management practices (BMP) for protecting the integrity of water resources, reduced impact logging (RIL) standards in industrial concessions, fire-fuel mitigation in wildland-urban interface (WUI), and carbon sequestration in standing forests and soils. Unique challenges that the successful design of performance bonding present are used as motivation for future research.
... The study by Gravelle and Link (2007) was primarily focused on forest harvesting, the study by Snyder et al. (2015) focused on a two month summer period in the Appalachian Mountains, and the other two headwater network studies were conducted in glaciated environments Cadbury et al. 2008), hence their inference to other environments and seasons may be limited. A broader set of studies has been conducted on headwater catchments within the context of forest harvesting (Moore et al. 2005a;Anderson et al. 2007;Rykken et al. 2007;Groom et al. 2011); however, these studies were focused on the response to harvesting for individual reaches and did not consider thermal variability across headwater networks. ...
Free copy available on Treesearch: https://www.fs.usda.gov/treesearch/pubs/54675------------------------------------------------------------------------------------------------------------------Thermal regimes of forested headwater streams control the growth and distribution of various aquatic organisms. In a western Oregon, USA, case study we examined: (1) forested headwater stream temperature variability in space and time; (2) relationships between stream temperature patterns and weather, above-stream canopy cover, and geomorphic attributes; and (3) the predictive ability of a regional stream temperature model to account for headwater stream temperature heterogeneity. Stream temperature observations were collected at 48 sites within a 128-ha managed forest in western Oregon during 2012 and 2013. Headwater stream temperatures showed the greatest spatial variability during summer (range up to 10 \(^\circ\)C) and during cold and dry winter periods (range up to 7.5 \(^\circ\)C), but showed less spatial variability during spring, fall and wet winter periods (range between 2 and 5 \(^\circ\)C). Distinct thermal regimes among sites were identified; however, geomorphic attributes typically used in regional stream temperature models were not good predictors of thermal variability at headwater scales. A regional stream temperature model captured the mode of mean August temperatures observed across the study area, but overpredicted temperatures for a quarter of the sites by up to 2.8 \(^\circ\)C. This study indicates considerable spatial thermal variability may occur at scales not resolved by regional stream temperature models. Recognizing this sub-landscape variability may be important when predicting distributions of aquatic organisms and their habitat under climate and environment change scenarios.
... Although the paired-watershed design can facilitate the exploration of causal 614 mechanisms associated with observed effects of contemporary logging practices on second 615 growth forests, this type of experiment must be replicated across the landscape to gain a broader 616 interpretation (e.g., De Groot et al. 2007; Gravelle and Link 2007, Leach et al. 2022). In recent 617years, multi-catchment regional studies focused on logging in second growth forests have 618 become more common (e.g.,Groom et al. 2011, Janisch et al. 2012, and although this approach 619 has limited potential to rigorously explore cause and effect, it will undoubtedly expand the 620Page 29 of 60 Can. J. Fish. ...
To investigate effects of headwater logging on downstream coastal cutthroat trout 17 Oncorhynchus clarkii clarkii populations, we monitored stream habitat and biotic indicators 18 including biomass, abundance, growth, movement, and survival over 8 years using a paired-19 watershed approach. Reference and logged catchments were located on private industrial 20 forestland on ~ 60-yr harvest rotation. Five clearcuts (14% of the logged catchment area) were 21 adjacent to fishless portions of the headwater streams, and contemporary regulations did not 22 require riparian forest buffers in the treatment catchment. Logging did not have significant 23 negative effects on downstream coastal cutthroat trout populations for the duration of the sample 24 period. Indeed, the only statistically significant response of fish populations following logging 25 in fishless headwaters was an increase in late-summer biomass (g·m-2) of age-1+ coastal 26 cutthroat trout in tributaries. Ultimately, the ability to make broad generalizations concerning 27 effects of timber harvest is difficult because response to disturbance (anthropogenically 28 influenced or not) in aquatic systems is complex and context dependent, but our findings provide 29 one example of environmentally compatible commercial logging in a regenerated forest setting.
... It may be beneficial to plan the timing of management activities so they do not disturb streams during low-flow periods and to avoid vulnerable areas during droughts. Since removal and alteration of riparian vegetation can increase stream temperature (Beschta et al., 1987;Dunham et al., 2007;Groom et al., 2011;Isaak et al., 2010;Sun et al., 2004;Swift and Messer, 1971;Swift, 1973;Wooldridge and Stern, 1979), maintaining or increasing shading from solar radiation through riparian buffer conservation and restoration (Burton and Likens, 1973;Swift, 1973;Peterson and Kwak, 1999;Kaushal et al., 2010) may buffer stream temperatures against drought. Other mitigation strategies, such as releases of cold-water from the hypolimnions of deep reservoirs can have a significant cooling effect in downstream reaches (Null et al., 2013) as can discharge of municipal wastewater from underground pipes, which may cool streams in the summer (Bogan et al., 2003). ...
The relationships among drought, surface water flow, and groundwater recharge are not straightforward for most forest ecosystems due to the strong role that vegetation plays in the forest water balance. Hydrologic responses to drought can be either mitigated or exacerbated by forest vegetation depending upon vegetation water use and how forest population dynamics respond to drought. Understanding how drought impacts ecosystems requires understanding how drought impacts ecohydrological processes. Because different species and functional groups vary in their ecophysiological traits that influence water use patterns, changes in species assemblages can alter hydrological processes from the stand to the watershed scales. Recent warming trends and more prolonged and frequent droughts have accelerated the spread and intensity of insect attacks in the western US that kill nearly all of the canopy trees within forest stands, changing the energy balance of the land surface and affecting many hydrologic processes. In contrast, some eastern forest tree species and size classes can tolerate drought better than others, suggesting the potential for drought-mediated shifts in both species composition and structure. Predicting how these changes will impact hydrologic processes at larger spatial and temporal scales presents a considerable challenge. The biogeochemical consequences of drought, such as changes in stream chemistry, are closely linked to vegetation dynamics and hydrologic responses. As with other natural disturbances, droughts are difficult to prepare for because they are unpredictable. However, there are management options that may be implemented to minimize the impacts of drought on water quantity and quality. Examples include reducing leaf area by thinning and regenerating cut forests with species that consume less water, although a high level of uncertainty in both drought projections and anticipated responses suggests the need for monitoring and adaptive management.
... This type of analysis assumes that in the future the watershed will have similar land use/ cover as presently exists. Studies have demonstrated that forestry harvest may result in increased stream temperature (Groom et al., 2011). If there are changes in landuse and in the amount of vegetation in riparian buffers, there may be further increases in stream heating above those suggested in this paper. ...
There is increasing evidence that our planet is warming and this warming is also resulting in rising sea levels. Estuaries which are located at the interface between land and ocean are impacted by these changes. We used CE-QUAL-W2 water quality model to predict changes in water temperature as a function of increasing air temperatures and rising sea level for the Yaquina Estuary, Oregon (USA). Annual average air temperature in the Yaquina watershed is expected to increase about 0.3 °C per decade by 2040–2069. An air temperature increase of 3 °C in the Yaquina watershed is likely to result in estuarine water temperature increasing by 0.7–1.6 °C. Largest water temperature increases are expected in the upper portion of the estuary, while sea level rise may mitigate some of the warming in the lower portion of the estuary. Smallest changes in water temperature are predicted to occur in the summer, and maximum changes during the winter and spring. Increases in air temperature may result in an increase in the number of days per year that the 7-day maximum average temperature exceeds 18 °C (criterion for protection of rearing and migration of salmonids and trout) as well as other water quality concerns. In the upstream portion of the estuary, a 4 °C increase in air temperature is predicted to cause an increase of 40 days not meeting the temperature criterion, while in the lower estuary the increase will depend upon rate of sea level rise (ranging from 31 to 19 days).
... Retention of ecological services provided by freshwater aquatic systems in forests epitomizes these challenges, because aquatic-dependent species, functions and processes can be directly and indirectly affected by traditional timber-harvest practices (e.g., [21][22][23][24][25]). Concerns for forest aquatic resources include maintenance or restoration of water quality (temperature [26][27][28][29][30]; sedimentation [31][32][33][34]) and suitable habitats for biodiversity (e.g., leaf litter inputs [35][36][37]; down wood [38][39][40][41]). ...
We examined the effects of a second-thinning harvest with alternative riparian
buffer management approaches on headwater stream habitats and associated vertebrates
in western Oregon, USA. Our analyses showed that stream reaches were generally
distinguished primarily by average width and depth, along with the percentage of the dry
reach length, and secondarily, by the volume of down wood. In the first year post-harvest,
we observed no effects of buffer treatment on stream habitat attributes after moderate levels
of thinning. One of two “thin-through” riparian treatments showed stronger trends for
enlarged stream channels, likely due to harvest disturbances. The effects of buffer
treatments on salamanders varied among species and with habitat structure. Densities of
Plethodon dunni and Rhyacotriton species increased post-harvest in the moderate-density
thinning with no-entry buffers in wider streams with more pools and narrower streams with
more down wood, respectively. However, Rhyacotriton densities decreased along streams
with the narrowest buffer, 6 m, and P. dunni and Dicamptodon tenebrosus densities
decreased in thin-through buffers. Our study supports the use of a 15-m or wider buffer to
retain sensitive headwater stream amphibians.
... Specifically, correlations are typically weak at a daily time scale (e.g., Erickson and Stefan 2000) whereas a coarser time scale (e.g., monthly) can lead to the compression of variability and thus, a loss of potentially relevant information. Accordingly, weekly time scales have been widely adopted for regulatory purposes (Groom et al 2011) and biological relevance , Mantua et al 2010. Thus, to be most comparable to published models of stream-air relationships, we calculated mean weekly air and water temperatures from the daily values at each of the 25 sites. ...
Worldwide, lack of data on stream temperature has motivated the use of regression-based statistical models to predict stream temperatures based on more widely available data on air temperatures. Such models have been widely applied to project responses of stream temperatures under climate change, but the performance of these models has not been fully evaluated. To address this knowledge gap, we examined the performance of two widely used linear and nonlinear regression models that predict stream temperatures based on air temperatures. We evaluated model performance and temporal stability of model parameters in a suite of regulated and unregulated streams with 11–44 years of stream temperature data. Although such models may have validity when predicting stream temperatures within the span of time that corresponds to the data used to develop them, model predictions did not transfer well to other time periods. Validation of model predictions of most recent stream temperatures, based on air temperature–stream temperature relationships from previous time periods often showed poor performance when compared with observed stream temperatures. Overall, model predictions were less robust in regulated streams and they frequently failed in detecting the coldest and warmest temperatures within all sites. In many cases, the magnitude of errors in these predictions falls within a range that equals or exceeds the magnitude of future projections of climate-related changes in stream temperatures reported for the region we studied (between 0.5 and 3.0 °C by 2080). The limited ability of regression-based statistical models to accurately project stream temperatures over time likely stems from the fact that underlying processes at play, namely the heat budgets of air and water, are distinctive in each medium and vary among localities and through time. S Online supplementary data available from stacks.iop.org/ERL/9/084015/mmedia
... 127 3. Quantify riparian characteristics that predict shade retention after harvesting. 128 We expand our assessment of stream temperature beyond the water quality standard-focused 129 weekly maximum temperatures reported by Groom et al. (2011) and examine daily maximum, 130 minimum, and mean temperatures as well as diurnal fluctuation, in order to better capture the 131 spectrum of temperature changes following harvest. The implications of findings for this study 132 likely extend to other regions with similar physical and biological characteristics, stream 133 temperature concerns, cold-water fisheries, and prescriptive riparian zone protections such as 134 Idaho, Alaska, British Columbia, Washington, and California. ...
A replicated before–after-control-impact study was used to test effectiveness of Oregon’s (USA) riparian protection measures at minimizing increases in summer stream temperature associated with timber harvest. Sites were located on private and state forest land. Practices on private forests require riparian management areas around fish-bearing streams; state forest’s prescriptions are similar but wider. Overall we found no change in maximum temperatures for state forest streams while private sites increased pre-harvest to post-harvest on average by 0.7°C with an observed range of response from −0.9 to 2.5°C. The observed increases are less than changes observed with historic management practices. The observed changes in stream temperature were most strongly correlated with shade levels measured before and after harvest. Treatment reach length, stream gradient, and changes in the upstream reach stream temperature were additionally useful in explaining treatment reach temperature change. Our models indicated that maximum, mean, minimum, and diel fluctuations in summer stream temperature increased with a reduction in shade, longer treatment reaches, and low gradient. Shade was best predicted by riparian basal area and tree height. Findings suggest that riparian protection measures that maintain higher shade such as the state forests were more likely to maintain stream temperatures similar to control conditions.
We employed a systematic evidence review to evaluate empirical scientific evidence for the effectiveness of buffering headwater (typically non-fish-bearing) streams to maintain stream temperature and stream-associated amphibian populations in the Pacific Northwest of Canada and the United States. To address our synthesis objective, we identified thirteen temperature, seven amphibian, and two temperature/amphibian primary research studies that met objective inclusion criteria. We evaluated external validity for how study treatments inform or were linked to causal factors influencing temperature response (a) and how the sampled population represented or provided inference to an intended target population or landscape (b). The evidence indicated substantial variability in the temperature response to streamside buffers. The effect size for the mean 7-day maximum temperature metric showed a positive association when comparing no-buffers (clearcut) to treatments with wide buffers (≥30 m). However, this effect varied substantially and overlap existed in effect sizes among no-cut buffers, no-cut plus variable retention buffers, and no-cut patch buffers all ≤20 m wide. Large variability in effect size among treatments obscured any potential trend between effect size for the seasonal (summer) mean daily maximum temperature metric and buffer width. Shade was correlated with temperature response within several studies, but direct comparisons of treatment effectiveness among studies as a function of shade was confounded by different measurement methods. The evidence also indicated that variation in temperature response among studies may be associated with multiple factors (geology, hydrology, topography, latitude, and stream azimuth) that influence thermal sensitivity of streams to shade loss. For amphibians, we found mixed evidence for relationships between population responses and buffers maintained along streams after forest harvest. Specifically, we did not find evidence to support the contention that positive population responses are associated consistently with larger buffers. Also, considerable uncertainty exists about which environmental covariates reliably explain variation in amphibian population responses. Collectively, our results indicate that evidence is weak to address questions most relevant to policy discussions concerning effectiveness of alternative riparian management schemes. Future studies should test effectiveness of alternative treatments with either experimental or purposefully structured observational studies to develop tools and derive guidelines for how to achieve management goals based on site and landscape characteristics.
How much stream temperatures increase within riparian canopy openings and whether stream temperatures cool downstream of these openings both have important policy implications. Past studies of stream cooling downstream of riparian openings have found mixed results including rapid, slow, and no cooling. We collected longitudinal profiles of stream temperatures above, within, and below riparian forest openings along stream segments within otherwise forested riparian conditions to evaluate how sensitivity of stream temperatures to riparian conditions varied across landscape factors. We conducted these temperature surveys across openings in 12 wadeable streams within and near the Upper Little Tennessee River Basin in western North Carolina and northeastern Georgia. Basin areas ranged from 74 to 6913 hectares, and bankfull channel widths varied from 3.4 to 16.4 meters. Stream temperatures were collected every fifteen‐minutes using HOBO® data loggers for two weeks in each stream, repeated later in summer in some streams. Reference temperatures were highest in stream reaches at low elevations and with large drainage areas. Stream temperature increases in the middle of riparian gaps were highest when streams drained small high‐elevation watersheds, and increases at the end of openings were highest when the opening length was large relative to watershed size. Downstream from openings, cooling rates were greatest in small, high‐elevation headwater streams and also increased with larger increases in canopy cover. Stream segments that warmed the most within openings also featured higher cooling rates downstream. The data show that stream temperature sensitivity to canopy change is highly dependent on network position and watershed size. A better understanding of stream temperature responses to riparian vegetation may be useful to land managers and landowners prioritizing riparian forest restoration. This article is protected by copyright. All rights reserved.
The Trask River Watershed Study in the northern Oregon Coast Range was designed to examine physical, chemical and biological effects of contemporary forest management practices on aquatic ecosystems. We measured stream temperature for 11 summers in 15 small watersheds, eight of which were harvested in 2012. Three riparian buffer treatments, which varied by landowner, were implemented. Using half‐hourly data, we characterized summer water temperature distributions with five percentiles: 5th, 25th, 50th, 75th, and 95th. Each percentile was analyzed as a separate response variable using a linear mixed model. After harvest, streams without overstory buffer requirements showed shifts in all the percentiles of the temperature distribution; the largest increase (3.6°C) occurred at the 95th percentile. Sites with narrow riparian buffers showed little to no change. We also calculated changes in duration of thermal exposure above 15°C and 16°C for two species of native stream amphibians; these temperatures occurred 4.7% and 1.3% of the time post‐harvest in the sites clearcut with no buffer. Analysis of distributions of summer temperatures pre‐ and post‐harvest enabled us to more fully characterize site‐to‐site variability and responses to forest management.
Research about nonindustrial private forest (NIPF) landowners’ perspectives on voluntary conservation-based programs continues to proliferate. However, there is a gap in understanding NIPF landowner perspectives about the social and ecological outcomes of mandatory conservation-based regulations. We sent questionnaires to Oregon NIPF landowners to understand their beliefs about potential outcomes of proposed state regulations that strengthen mandatory riparian buffer habitat protection requirements. Factor analysis and multiple regression techniques revealed the most important variables that influence those beliefs. Overall, respondents believed that the socioeconomic outcomes were negative and the ecological outcomes were neutral or slightly positive. Respondents with more conservative political attitudes who owned larger properties were more likely to believe that the outcomes would be negative. As the importance of maintaining property for future generations and increasing timber productivity increased, respondents believed the potential outcomes would be increasingly negative. As the importance of improving water quality, increasing carbon storage, and improving recreational use on the property increased, respondents believed that the outcomes would be increasingly positive. We discuss management and policy implications, including communication strategies aimed at engaging with NIPF landowners to highlight the purpose and potential outcomes of forest and riparian management regulations.
Light availability influences temperature, primary production, nutrient dynamics, and secondary production in aquatic ecosystems. In forested freshwater ecosystems, shading by streamside (riparian) vegetation is a dominant control on light flux and represents an important interaction at the aquatic–terrestrial interface. Changes in forest structure over time, particularly tree mortality processes that gradually increase light penetration through maturing forest canopies, are likely to influence stream light fluxes and associated ecosystem functions. We provide a set of conceptual models describing how stream light dynamics change with the development of complex canopy structure and how changes in light availability are likely to affect stream ecosystem processes. Shortly after a stand-replacing event, light flux to the stream is high, but light fluxes decline as canopies reestablish and close. Tree density, the degree of understory growth, patterns of tree mortality, and small-scale disturbances interact as drivers of multiple pathways of forest structural development. Changes in canopy structure will, in turn, influence stream light, which is expected to impact primary production and stream nutrient dynamics as well as the amount of autochthonous carbon supporting aquatic food webs. Ultimately, these conceptual models stress the importance of recovery from historic forest disturbances as well as future forest change as important factors influencing the long-term trajectories of ecosystem processes in headwaters.
One objective of the Oregon State Forest riparian management strategies is to provide a long-term supply of wood to streams. We explored this objective as a case study by comparing the predicted wood loads from a riparian forest managed in accordance with Northwest Oregon State Forest Management Plan to an unmanaged riparian forest. We obtained riparian tree inventories of plots from an Oregon Department of Forestry's Riparian Function and Stream Temperature Study site. The site's overstory was measured before and after harvest conducted according to the riparian management strategies. We used the pre- and post-treatment data as initial conditions for 200-year growth simulations in the forest growth model PNW Zelig. The forest model results were then used to predict wood volume in the stream from two riparian management scenarios using the model OSU StreamWood. We found that the stream wood volumes were almost identical in the two simulations, suggesting that at least for this particular site, Oregon's state riparian regulations are predicted to provide a long-term supply of wood to streams similar to that in an unmanaged riparian forest.
Stream temperature changes as a result of forest practices have been a concern in the Pacific Northwest for several decades. As a result of this concern, stream protection requirements for forest lands were first adopted in the early 1970s and have become progressively more stringent. While there have been multiple studies examining the effects of stream protection buffers on water temperature, there are few studies examining temperature patterns over long periods on intensively managed forests. Water temperature in the upper Deschutes River watershed, Washington has been monitored since 1975 and represents one of the longest studies of water quality on managed forests in the Pacific Northwest. This data record, collected from basins of varying sizes, has enabled us to examine the combined effects of hydro-climatic patterns and forest management on stream temperature. Effects of harvest conducted prior to buffer regulations were clearly identifiable and most pronounced on smaller streams. We were not able to detect any response on larger channels to more recent timber harvest where riparian buffers were required. This analysis also emphasizes that it is critical to account for changing climate when examining long-term temperature patterns. We found that in many cases the temperature improvements associated with more stringent buffer requirements implemented over the last 35 years in the Deschutes watershed have been offset by warming climatic conditions.
Stream temperatures were monitored on seven low-elevation western Oregon streams immediately after clearcut harvesting and 14‐17 years later in two studies that examined buffer designs. One study on four streams used no-tree buffers with all trees next to the stream harvested
within the clearcut units. The second study on three streams examined partial buffers designed to shade the stream only from direct sun. Streams with no-tree buffers in clearcuts 90 or 180 m long mostly exhibited significantly less warming 16‐17 years after harvest than 1‐5 years
after harvest. Streams with partial buffers had originally shown slight response to harvest, and 14‐15 years after harvest temperature trends were not different from preharvest trends. Percent cover and estimated radiation 14‐17 years after harvesting were mostly similar in harvested
and uncut areas. The exceptions were areas close to the streams that were cleared by beavers (Castor canadensis), where streams were wide resulting in canopy openings, and where gravel bars with minimal plant development occurred. Planted conifers in no-tree riparian areas provided
less shade than hardwoods and were mostly suppressed by hardwoods or damaged by beavers.
Determining the effectiveness of different riparian buffers for mitigating forest-harvesting impacts on stream temperatures continues to be of interest throughout the world. Four small, low or medium elevation streams in managed western Oregon forests were studied to determine how the arrangement and amount of streamside retention strips (buffers) in clear-cut units influenced stream temperatures. Buffers included (i) no tree, (ii) predominantly sun-sided 12 m wide partial, and (iii) two-sided (Best Management Practice, (BMP)) 15-30 m wide buffers. Harvested units alternated with uncut units along 1800-2600 m study reaches. Impacts of harvesting on stream temperatures were determined by time series comparisons of postharvest and preharvest regressions. Trends for daily maximum and mean stream temperature significantly increased after harvest in no tree buffer units. Partial buffers led to slight (<2 degrees C) or no increased warming. BMP units led to significantly increased warming, slight, or no increased warming. Temperature responses in uncut units appeared to be linked to responses in upstream harvested units. In many instances, when harvested units exhibited significantly higher postharvest trends, lower trends were observed in the uncut units downstream. Stream temperature trends of 7 day moving maxima indicated warming through the no tree buffer units and some of the BMP units. Peaks in maxima were not maintained in downstream units. Stream temperature responses were related to buffer implementation and stream features, relating to cooling and warming.
Data from a paired-catchment study in south coastal British Columbia, Canada, were analyzed to assess the thermal effects of clearcut harvesting with no riparian buffer on a fish-bearing headwater stream. The approach used time series of daily mean water temperatures for East Creek (control) and A Creek (treatment), both before and after harvest. Statistical models were developed to predict (a) what the temperatures would have been in the post-harvest period had harvesting not occurred, and (b) what temperatures would have been in the pre-harvest period had harvesting already occurred. The Wisconsin Bioenergetics Model was used to simulate growth of coastal cutthroat trout (Oncorhynchus clarki clarki) for the first year following fry emergence using the predicted and observed stream temperatures to generate scenarios representing with-harvest and no-harvest thermal regimes. A Monte Carlo approach was used to quantify the effects of uncertainty associated with the regression models on predicted stream temperature and trout growth. Summer daily mean temperatures in the with-harvest scenario were up to
$5^{\circ}\hbox{C}$
higher than those for the no-harvest scenario. Harvesting-induced warming reduced growth rates during summer, but increased growth rates during autumn and spring. In the with-harvest scenario, trout were 0.2–2.0 g (absolute weight) smaller throughout the winter period than in the no-harvest scenario. However, the bioenergetic simulations suggest that trout growth may be more sensitive to potential changes in food supply following harvesting than to direct impacts of stream temperature changes.
This study focused on a headwater forest stream in coastal British Columbia, Canada. Air temperature, humidity and wind speed were measured at a height of 1.5 m above the stream and at a control site within a clearcut located approximately 1 km from the study stream, both before and after partial-retention forest harvesting along the stream. A specially designed evaporimeter was used to measure evaporation. Laboratory trials confirmed the reliability of evaporimeter measurements. Prior to harvesting, wind speeds were low and vapour pressure gradients above the stream were weak, leading to low rates of evaporation. Following harvesting, the decreased shading and increased ventilation over the stream led to higher wind speeds, lower vapour pressures, higher daily maximum air temperatures, higher stream temperatures and surface vapour pressures, and higher rates of evaporation. A wind function that has been used to estimate stream evaporation in a number of previous studies, but which had not been compared to measured stream evaporation, was found to overestimate evaporation. An empirical wind function fitted to the evaporimeter data differed from three others that have been derived for predicting stream evaporation in that our data did not support the inclusion of an intercept. It is hypothesized that the lack of an intercept for our data reflects the strongly stable conditions over the stream. Further research should measure stream evaporation over a broad range of streamflow and meteorological conditions, with particular attention to the role of atmospheric stability.
Declines in cold-water habitat and fisheries have generated stream-temperature monitoring
efforts across Northern California and the western United States. We demonstrate a
statistical analysis approach to facilitate the interpretation and application of
these data sets to achieve monitoring objectives. Specifically, we used data collected
from the Willow and Lassen creek watersheds in Modoc County to demonstrate a method
for identifying and quantifying potential relationships between stream temperature
and factors such as stream flow, canopy cover and air temperature. Our monitoring
data clearly indicated that a combination of management practices to increase both
in-stream flow and canopy cover can be expected to reduce stream temperature on the
watersheds studied.
This study examined water temperature patterns and their physical controls for two small, clearing-heated streams in shaded reaches downstream of all forestry activity. Field observations were made during July-August 2000 in the central interior of British Columbia, Canada. For both reaches, downstream cooling of up to 4°C had been ob- served during daytime over distances of ~200 m. Radiative and convective exchanges of energy at heavily shaded sites on both reaches represented a net input of heat during most afternoons and therefore could not explain the observed cooling. In one stream, the greatest downstream cooling occurred when streamflow at the upstream site dropped below about 5 L·s-1. At those times, temperatures at the downstream site were controlled mainly by local inflow of ground- water, because the warmer water from upstream was lost by infiltration in the upper 150 m of the reach. Warming of- ten occurred in the upper subreach, where cool groundwater did not interact with the channel. At the second stream, creek temperature patterns were comparatively stable. Energy balance estimates from one afternoon suggested that groundwater inflow caused about 40% of the ~3°C gross cooling effect in the daily maximum temperature, whereas bed heat conduction and hyporheic exchange caused about 60%.
The temperature of stream water is an important control of many in-stream processes. To better understand the processes and consequences of solar energy inputs to streams, stream temperature dynamics were examined before, during, and after experimental shading of a 150-m reach of a second-order stream in the Oregon Cascade Range. Maximum water temperatures declined significantly in the shaded reach, but minimum and mean temperatures were not modified. Heat budget calculations before shading show the dominance of solar energy as an influence of stream tem-perature. The influence of substrate type on stream temperature was examined separately where the water flowed first over bedrock and then through alluvial substrates. Maximum temperatures in the upstream bedrock reach were up to 8.6 °C higher and 3.4 °C lower than downstream in the alluvial reach. Better understanding of factors that influence not only maximum but minimum temperatures as well as diurnal temperature variation will highlight types of reaches in which stream temperature would be most responsive to changes in shading. Many apparent discrepancies in stream temperature literature can be explained by considering variation in the relative importance of different stream temperature drivers within and among streams and over time.
We quantified distribution and behavior of adult spring chinook salmon (Oncorhynchus tshawytscha ) related to patterns of stream temperature and physical habitat at channel-unit, reach-, and section-level spatial scales in a wilderness stream and a disturbed stream in the John Day River basin in northeastern Oregon. We investigated the effectiveness of thermal remote sensing for analyzing spatial patterns of stream temperature and assessed habitat selection by spring chinook salmon, evaluating whether thermal refugia might be responsible for the persistence of these stocks in rivers where water temperatures frequently exceed their upper tolerance levels (258C) during spawning migration. By presenting stream temperature and the ecology of chinook salmon in a historical context, we could evaluate how changes in riverine habitat and thermal spatial structure, which can be caused by land- use practices, may influence distributional patterns of chinook salmon. Thermal remote sensing provided spatially continuous maps of stream temperature for reaches used by chinook salmon in the upper subbasins of the Middle Fork and North Fork John Day River. Electivity analysis and logistic regression were used to test for associations between the longitudinal distribution of salmon and cool-water areas and stream habitat characteristics. Chinook salmon were distributed nonuniformly in reaches throughout each stream. Salmon distribution and cool water temperature patterns were most strongly related at reach-level spatial scales in the warm stream, the Middle Fork (maximum likelihood ratio: P , 0.01), and most weakly related in the cold stream, the North Fork (P. 0.30). Pools were preferred by adult chinook salmon in both subbasins (Bonferroni confidence interval: P # 0.05); however, riffles were used proportionately more frequently in the North Fork than in the Middle Fork. Our observations of thermal refugia and their use by chinook salmon at multiple spatial scales reveal that, although heterogeneity in the longitudinal stream tem- perature profile may be viewed as an ecological warning sign, thermal patchiness in streams also should be recognized for its biological potential to provide habitat for species existing at the margin of their environmental tolerances.
The effect on removal of lower, mid, and upper slope vegetation on the diurnal variation in streamflow from a 46-ha catchment was observed. The diurnal variation in streamflow of the small stream was measurable during the late-spring-to-late-autumn period. The amplitude in streamflow variation reached a maximum in early summer and declined during autumn. Observation of diurnal variations during the periods of higher flow in winter and spring showed that they may occur but were masked by much larger variations associated with storm runoff. Simulation of the characteristics of the flow measurement system showed that diurnal variations can only be studied using V-notch weirs and float recorders during periods of low flow. No effect of the clearing of slope vegetation on the phase of the outflow could be found. However, there was evidence of a significant increase in amplitude, probably due to increased groundwater outflow from the slopes. It was concluded that the diurnal variation is due to transpiration by the riparian and near-riparian vegetation only, and that the lower to mid slope vegetation plays little role in this variation. Simulations suggested that increased amplitude is associated with increased flow rates, and that the amplitude is not directly affected by water use of vegetation on the catchment slopes. It was concluded that the amplitude of the variation is insensitive to changes in slope hydrology and cannot be used to provide insight into deep slope processes.
Riparian zones are vital components of the landscape. Much attention has been focused on the question of how wide a buffer is needed to protect the original riparian environment. We sampled five streams 2-4 m wide and associated riparian ecosystems before and after clearcutting in western Washington. Buffers ranging from 17 to 72 m wide were left intact at all sites when harvesting. Our objectives were: (1) to characterize pre- harvest microclimatic gradients across riparian ecosystems, from the stream to the upland; (2) to identify effects of harvesting on these gradients; and (3) to describe effects of buffer width and near-stream microclimate on stream microclimate. Six weather stations measuring air temperature, soil temperature, surface air temperature, relative humidity, short-wave solar radiation, and wind speed were installed along transects running across the stream and into the upland, and two reference stations were established, one in an upland clearcut and one in an upland interior forest. Pairwise comparison tests were used to evaluate statistical differences between stations along transects for determination of gradient extent. Pre-harvest riparian gradients existed for all variables except solar radiation and wind speed, and values generally approached forest interior values within 31-62 m from the stream. After harvesting, microclimate values at the buffer edge and each subsequent location toward the upland began to approximate clearcut values instead of forest interior values, indicating an interruption or elimination of the stream-upland gradient. In addition, re- gression analyses showed that stream microclimate was affected to some degree by buffer width and microclimate in the surrounding area. We conclude that a buffer at least 45 m on each side of the stream is necessary to maintain a natural riparian microclimatic en- vironment along the streams in our study, which were characterized by moderate to steep slopes, 70-80% overstory coverage (predominantly Douglas-fir and western hemlock), and a regional climate typified by hot, dry summers and mild, wet winters. This buffer width estimate is probably low, however, since it assumes that gradients stabilize within 30 m from the stream and that upslope edge effects extend no more than 15 m into the buffer (a low estimate based on other studies). Depending on the variable, required widths may extend up to 300 m, which is significantly greater than standard widths currently in use in the region (i.e., ;10-90 m). Our results indicate that even some of the more conservative standard buffer widths may not be adequate for preserving an unaltered microclimate near some streams. Additional site-specific data are needed for different site conditions in order to determine whether generalizations can be made regarding near-stream microclimate.
A numerical model based on a finite difference solution of the unsteady heat advection-dispersion equation is formulated to predict water temperatures in streams at time increments of 1 hour. An energy balance accounts for the effects of air temperature, solar radiation, relative humidity, cloud cover, and wind speed on the net rate of heat exchange through the water surface, and heat conduction between water and streambed. Continuous stream temperature recordings in shallow streams show strong dynamic behavior including diurnal variations of several degrees Celsius which are lost in the standard daily records. These measured water temperatures are used to calibrate the model for the optimum percentages of Sun shading and wind sheltering. Stream exposure to solar radiation is shown to vary from 30 to 100% and wind exposure from 10 to 30% depending on the character of the stream. Values are related to stream width and season because of variable leaf cover of trees on stream banks. After calibration, accuracies of hourly and daily water temperature predictions over periods of several weeks are of the order of 0.2 to 1°C. Solar (shortwave) radiation is shown to be the most important component of the heat flux across the stream water surface, but none of the other components, i.e., long-wave radiation, evaporation and convection to the atmosphere, are negligible. Conductive heat exchange between the streambed and the water is a significant heat balance component in shallow streams.
Heterogeneity in stream water temperatures created by local influx of cooler subsurface waters into geomorphically complex stream channels was associated with increased abundance of rainbow trout (Oncorhynchus mykiss) and chinook salmon (Oncorhynchus tshawytscha) in northeastern Oregon. The addition of cold water patch frequency and area as explanatory variables in salmonid habitat models indicated that doubling of cold water patch frequency was associated with increases in rainbow trout and chinook salmon abundances of 31% and 59%, respectively. Doubling of cold water patch area was associated with changes of 10% in rainbow trout abundance but was not associated with chinook abundance after accounting for other habitat factors. The physiognomy, distribution, and connectivity of cold water patches, important attributes determining the effectiveness of these habitats as thermal refuges for stream fishes, were associated with channel bedform and riparian features. Monitoring of thermal heterogeneity and salmonid populations in response to ongoing habitat restoration efforts will provide additional insights into causal relationships among these factors.
Wild salmon stocks in the Pacific Northwest are imperiled by a variety of anthropogenic environmental modifications, not the least of which is increasing maximum water temperatures. While many reports have been written on physiological or population-level influences of temperature in terms of the decline of wild salmon, synthesis of these diverse sources is needed for evaluation of numeric temperature criteria and their potential in salmon recovery planning. Various sensitive life stages and biological processes are impacted differently for different salmon species. This article reviews the literature for chinook, coho, chum, and steelhead, which are currently listed in the Columbia River Basin under the Endangered Species Act. Spawning, incubation and early fry development, juvenile rearing and growth, smoltification, and migration are considered. Swimming speed, disease susceptibility, chemical considerations, and lethality are also reviewed. Regional population growth and climate change will exacerbate the difficulties of recovering Northwestern salmon beyond remnant runs. Ethical analysis of the assumptions underlying recovery policy decisions, proposals for regime-based water quality standards, and a systems level vulnerability analysis are components of the recovery planning discussions. Specific numeric maximum temperature criteria that can be integrated into a broader recovery planning process are described for sensitive life stages of three species of Pacific Northwest salmon and steelhead.
Differing perceptions of the impacts on hydrological functions of tropical forest clearance and conversion to other land uses have given rise to growing and often heated debate about directions of public environmental policy in southeast Asia. In order to help bring more balance and clarity to such debate, this paper reviews a wide range of available scientific evidence with respect to the influence exerted by the presence or absence of a good forest cover on regional climate (rainfall), total and seasonal water yield (floods, low flows), as well as on different forms of erosion and catchment sediment yield under humid tropical conditions in general and in southeast Asia in particular. It is concluded that effects of forest disturbance and conversion on rainfall will be smaller than the average decrease of 8% predicted for a complete conversion to grassland in southeast Asia because the radiative properties of secondary regrowth quickly resemble those of the original forest again. In addition, under the prevailing 'maritime' climatic conditions, effects of land-cover change on climate can be expected to be less pronounced than those of changes in sea-surface temperatures. Total annual water yield is seen to increase with the percentage of forest biomass removed, with maximum gains in water yield upon total clearing. Actual amounts differ between sites and years due to differences in rainfall and degree of surface disturbance. As long as surface disturbance remains limited, the bulk of the annual increase in water yield occurs as baseflow (low flows), but often rainfall infiltration opportunities are reduced to the extent that groundwater reserves are replenished insufficiently during the rainy season, with strong declines in dry season flows as a result. Although reforestation and soil conservation measures are capable of reducing the enhanced peak flows and stormflows associated with soil degradation, no well-documented case exists where this has also produced a corresponding increase in low flows. To some extent this will reflect the higher water use of the newly planted trees but it cannot be ruled out that soil water storage opportunities may have declined too much as a result of soil erosion during the post-clearing phase for remediation to have a net positive effect. A good plant cover is generally capable of preventing surface erosion and, in the case of a well-developed tree cover, shallow landsliding as well, but more deep-seated (>3 m) slides are determined rather by geological and climatic factors. A survey of over 60 catchment sediment yield studies from southeast Asia demonstrates the very considerable effects of such common forest disturbances as selective logging and clearing for agriculture or plantations, and, above all, urbanisation, mining and road construction. The 'low flow problem' is identified as the single most important 'watershed' issue requiring further research, along with the evaluation of the time lag between upland soil conservation measures and any resulting changes in sediment yield at increasingly large distances downstream. It is recommended to conduct such future work within the context of the traditional paired catchment approach, complemented with process-based measuring and modelling techniques. Finally, more attention should be paid to the underlying geological * Tel. controls of catchment hydrological behaviour when analysing the effect of land use change on (low) flows or sediment production.
Cool summertime stream temperature is an important component of high quality aquatic habitat in Oregon coastal streams. Within the Oregon Coast Range, small headwater streams make up a majority of the stream network; yet, little information is available on temperature patterns and the longitudinal variability for these streams. In this paper we describe preharvest spatial and temporal patterns in summer stream temperature for small streams of the Oregon Coast Range in forests managed for timber production. We also explore relationships between stream and riparian attributes and observed stream temperature conditions and patterns. Summer stream temperature, channel, and riparian data were collected on 36 headwater streams in 2002, 2003, and 2004. Mean stream temperatures were consistent among summers and generally warmed in a downstream direction. However, longitudinal trends in maximum temperatures were more variable. At the reach scale of 0.5-1.7 km, maximum temperatures increased in 17 streams, decreased in seven streams and did not change in three reaches. At the subreach scale (0.1-1.5 km), maximum temperatures increased in 28 subreaches, decreased in 14, and did not change in 12 subreaches. Models of increasing temperature in a downstream direction may oversimplify fine-scale patterns in small streams. Stream and riparian attributes that correlated with observed temperature patterns included cover, channel substrate, channel gradient, instream wood jam volume, riparian stand density, and geology type. Longitudinal patterns of stream temperature are an important consideration for background characterization of water quality. Studies attempting to evaluate stream temperature response to timber harvest or other modifications should quantify variability in longitudinal patterns of stream temperature prior to logging.
Retaining streamside buffers has become a common way of protecting streams during timber harvest operations. Trees within forest buffers help stabilize streambanks, provide shade, and serve as a source of large woody debris. However, buffer trees are often subject to increased levels of windthrow which may impair some buffer functions. Forty (40) forest buffers bordering small, non-fish bearing streams in northwest Washington were assessed to quantify the level and in-stream effects of windthrow 1 to 3 years after clearcut harvest of adjacent timber. On average, windthrow affected 33 percent of buffer trees and ranged from 2 to 92 percent across the 40 sites. Sixty-seven percent of windthrown trees fell to the north, northeast, or northwest, while only three percent of the total fell towards the south. Large woody debris present in streams at the time of harvest was significantly larger than debris recruited as a result of buffer windthrow (t-test; p<0.01). Windthrow increased total in-stream large woody debris piece counts by 52 percent. Seventy-five percent of in-stream large woody debris pieces recruited to streams post-harvest were suspended above the bankfull channel while four percent stored sediment. Seventeen percent of uprooted trees delivered sediment to stream channels. The average volume input was 0.16 cubic meters per uprooted tree and 0.48 cubic meters per 100 meters of stream channel at 39 sites where mass wasting did not occur. At most sites, the volume of sediment input to streams was small relative to the amount stored behind obstructions. Large woody debris was the primary component of 93 percent of in-stream obstructions which stored sediment.
Stream temperatures, chemistry and turbidity were monitored in two partially harvested (7-33%) watersheds, Rock and Tower creeks, and an uncut old-growth watershed, West Twin Creek in the Hoh River Valley on the Olympic Peninsula, Washington. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was replanted in the harvested areas and red alder (Alnus rubra Bong.), a nitrogen fixer, dominated the riparian areas in the sampling sites on Rock and Tower creeks. We collected grab stream water samples monthly, from May 1996 to June 1998 and analyzed them for pH, electrical conductivity, total N and P, and major cations and anions. Stream temperatures were monitored continuously and turbidity was monitored monthly from May 1997 to June 1998. Partial harvesting had little influence on stream temperature, chemistry and turbidity 11-15 years after harvesting. Stream temperatures were more seasonally variable in the harvested streams compared to the unharvested old-growth site with an average summertime maximum elevated by 3.5°C. Maximum stream temperatures did not exceed 16°C in any stream and therefore salmonid species are not likely to be affected. There were significant differences in concentrations of some cations, anions and EC between the old-growth and the partially harvested watershed streams, but in most cases concentrations were actually higher in the unharvested watershed. Nitrate concentrations and stream turbidity were not significantly higher in the harvested watersheds.
Temperature is known to be an important mechanism affecting the growth and distribution of stream insects. However, little information exists that describes how variable temperatures are among streams of similar size, especially in physically heterogeneous landscapes. We measured summer daytime temperature and the structure of riffle benthic insect assemblages from 45 montane streams in California. Summer stream temperature was nearly randomly distributed across large-scale geographic gradients of latitude (6°) and elevation (2000 m). The lack of geographic trends in summertime stream temperature appeared to be caused by the strong relationship between local channel morphology and summer water temperature. Mean daytime water temperature was most strongly related to the % of the channel present as pools, which did not vary systematically with either latitude or elevation. We used multiple multivariate regression analysis, non-metric multidimensional scaling (NMDS), and graphical techniques to both quantify differences in insect assemblage structure among streams and to determine the degree to which assemblage structure was related to temperature. NMDS analyses were conducted on 3 similarity matrices based on: 1) presence and absence of all aquatic insect taxa encountered during the study, 2) densities of the 16 most numerically abundant taxa, and 3) population biomasses of the 16 most common taxa. All 3 analyses showed that variation in assemblage structure among streams was significantly related to temperature, although assemblage structure was most strongly related to sampling date--a consequence of sampling over a 98-d period. Temperature probably influenced assemblage structure in 2 ways: 1) by influencing developmental rates of individual taxa and overall assemblage phenology, thus affecting the relative abundances of taxa found on a specific sampling date, and 2) by excluding taxa unable to tolerate certain temperature ranges. Because of the strong dependency of assemblage structure on temperature and the lack of strong geographic trends in temperature among these streams, much of the measured variation in assemblage structure appeared to be unrelated to latitude or elevation. These results have important implications for both our understanding of natural biogeographic patterns of lotic organisms and our ability to detect and model the effects of climate change and other thermal alterations on stream ecosystems.
Plots, probability plots and regression tests tests using moments other tests for univariate normality goodness of fit tests testing for outliers in univariate samples power comparisons for univariate tests for normality testing for normalitywith censored data assessing multivariate normality testing for multivariate outliers testing for normal mixtures robust methods computational methods and issues. Appendices: data sets used in examples critical values for tests.
Riparian zones are vital components of the landscape. Much attention has been focused on the question of how wide a buffer is needed to protect the original riparian environment. We sampled five streams 2-4 m wide and associated riparian ecosystems before and after clearcutting in western Washington. Buffers ranging from 17 to 72 m wide were left intact at all sites when harvesting. Our objectives were: (1) to characterize pre- harvest microclimatic gradients across riparian ecosystems, from the stream to the upland; (2) to identify effects of harvesting on these gradients; and (3) to describe effects of buffer width and near-stream microclimate on stream microclimate. Six weather stations measuring air temperature, soil temperature, surface air temperature, relative humidity, short-wave solar radiation, and wind speed were installed along transects running across the stream and into the upland, and two reference stations were established, one in an upland clearcut and one in an upland interior forest. Pairwise comparison tests were used to evaluate statistical differences between stations along transects for determination of gradient extent. Pre-harvest riparian gradients existed for all variables except solar radiation and wind speed, and values generally approached forest interior values within 31-62 m from the stream. After harvesting, microclimate values at the buffer edge and each subsequent location toward the upland began to approximate clearcut values instead of forest interior values, indicating an interruption or elimination of the stream-upland gradient. In addition, re- gression analyses showed that stream microclimate was affected to some degree by buffer width and microclimate in the surrounding area. We conclude that a buffer at least 45 m on each side of the stream is necessary to maintain a natural riparian microclimatic en- vironment along the streams in our study, which were characterized by moderate to steep slopes, 70-80% overstory coverage (predominantly Douglas-fir and western hemlock), and a regional climate typified by hot, dry summers and mild, wet winters. This buffer width estimate is probably low, however, since it assumes that gradients stabilize within 30 m from the stream and that upslope edge effects extend no more than 15 m into the buffer (a low estimate based on other studies). Depending on the variable, required widths may extend up to 300 m, which is significantly greater than standard widths currently in use in the region (i.e., -10-90 m). Our results indicate that even some of the more conservative standard buffer widths may not be adequate for preserving an unaltered microclimate near some streams. Additional site-specific data are needed for different site conditions in order to determine whether generalizations can be made regarding near-stream microclimate.
Although the future timber supply in the northern hemisphere is expected to come from boreal and subboreal forests, little research has been conducted in these regions that examines the temperature responses of small, lake- headed streams to streamside timber harvesting. We examined the temperature patterns of two subboreal outlet streams in north-central British Columbia for 1 year before and 3 years after clearcut logging and found only modest changes (averaging 0.05-1.1°C) with respect to summer daily maximum and minimum temperatures, diurnal fluctuations, and stream cooling. A multistream comparative survey conducted in the same geographic region revealed that streams headed by small lakes or swamps tended to cool as they flowed downstream, and headwater streams warmed, regard- less of whether or not timber harvesting took place. Stream cooling was attributed to a combination of warm outlet temperatures (promoted by the presence of the lakes) and cold groundwater inflows. A regression model revealed that summertime downstream warming or cooling in headwater and outlet streams could be predicted by upstream maxi- mum summer temperatures and canopy cover. Lentic water bodies and groundwater inflows are important determinants of stream temperature patterns in subboreal forests and may subsequently moderate their responses to streamside har- vesting. Résumé : Bien que les sources futures de bois dans l'hémisphère nord doivent, pense-t-on, provenir surtout des forêts
A 6-year study documented the effects of clear-cut harvesting with and without riparian buffers (10 m and 30 m wide) on headwater stream temperature in coastal British Columbia. The experiment involved a replicated paired catchment design. Pretreatment calibration relations between the treatment and control streams were fitted using time series of daily minimum, mean, and maximum temperatures. Generalized least squares (GLS) regression was used to account for autocorrelation in the residuals. While water temperature in streams with 10 and 30 m buffers did not exhibit marked warming, daily maximum temperature in summer increased by up to 2°-8°C in the streams with no buffer. The effectiveness of the buffers may have been maximized by the north-south orientation of the streams, which meant that the streams would be well shaded from late morning to early afternoon by the overhead canopy, even under the 10 m buffer. The variation in response for the no-buffer treatments is consistent with the differences in channel morphology that influence their exposure to solar radiation and their depth. Relations between treatment effect and daily maximum air temperature suggested that recovery toward preharvest temperature conditions was occurring, with rates appearing to vary with stream and by season.
Daily and seasonal water temperature patterns were investigated at 22 habitats in five geomorphic reaches along an Alpine-Mediterranean river. Study reaches spanned 2nd- to 7th-order river segments. Habitats included headwater streams, main and secondary channels, backwaters, and isolated pools. Multiple linear regression analyses extracted elevation and azimuth (aspect) out of eight geographical and environmental variables to explain average daily temperature patterns among habitats. Azimuth and, to a lesser degree, slope, depth, velocity, and canopy were primary determinants of diel temperature amplitude and maximum rates of diel heating and cooling. Within lowland floodplain reaches, the relative influence of groundwater and surface water varied substantially among habitats. Thermal variation among habitats was greatest in lowland floodplain reaches (nearly 15 degreesC difference). In summer and autumn, variation between lowland floodplain aquatic habitats exceeded thermal variation observed in the main channel along the entire river corridor (120 km; 5-1100 m above sea level). Spatiotemporal variation in temperature was greatest in lower reaches owing to the interaction of water level and connectivity of isolated water bodies. Influence of groundwater and cool-water tributaries exemplified the importance of local factors (geomorphology and hydrology) superimposed on regional factors (climate and altitude) in determining large-scale thermal patterns.
Water temperature has profound effects on stream ecosystems. We studied effects of clear-fell logging Pinus radiata plantations on mid-summer water temperatures and recovery times in streams with 2–12m wide channels. Post-logging increases were 2–3.8°C for summer daily means and 4–7.3°C for summer daily maxima. Rates of recovery of thermal regimes after logging were strongly negatively correlated with stream size, as indexed by catchment area, channel width or baseflow (r2=0.80–0.93). Summer daily mean and maximum temperatures declined during the riparian vegetation regrowth phase by 0.18 and 0.47°Cyear−1, respectively, for the largest stream and 1.4 and 1.9°Cyear−1 in the smallest stream. Thermal regimes were restored in small streams (2–4m wide channels) about 6–8 years after clearfelling. In medium-sized streams (6–12m wide channels), we predict this recovery will take 12–16 years.
The principal source of energy for warming streams is the sun. The amount of sunlight reaching the stream may be increased after clear-cut logging. Average monthly maximum temperatures increased by 14°F and annual maximum temperatures increased from 57° to 85°F one year after clear-cut logging on a small watershed in Oregon's coast range. In a nearby watershed where strips of brush and trees separated logging units from the stream, no changes in temperature were observed that could be attributed to clear- cutting.
In linear mixed models, the Akaike information criterion (AIC) is of-ten used to decide on the inclusion of a random effect. An important special case is the choice between linear and nonparametric regression models estimated us-ing mixed model penalized splines. We investigate the behavior of two commonly used versions of the AIC, derived either from the implied marginal model or the conditional model formulation. We find that the marginal AIC is not asymp-totically unbiased for twice the expected relative Kullback-Leibler distance, and favors smaller models without random effects. For the conditional AIC, it is com-putationally costly for large sample sizes to correct for estimation uncertainty. However, ignoring it, as is common practice, induces a bias that yields the follow-ing behavior: Whenever the random effects variance estimate is positive (even if small), the more complex model is preferred. We illustrate our results in a simu-lation study, and investigate their impact in modeling childhood malnutrition in Zambia.
This study examined the thermal regime of a headwater stream within a clear-cut. The stream had a complex morphology dominated by step–pool features, many formed by sediment accumulation upstream of woody debris. Maximum daily temperatures increased up to 5 °C after logging, and were positively associated with maximum daily air temperature and negatively with discharge. Maximum daily temperatures generally increased with downstream distance through the cut block, but decreased with distance in two segments over distances of tens of metres, where the topography indicated relatively concentrated lateral inflow. Localized cool areas within a step–pool unit were associated with zones of concentrated upwelling. Bed temperatures tended to be higher and have greater ranges in areas of downwelling flow into the bed. Heat budget estimates were made using meteorological measurements over the water surface and a model of net radiation using canopy characteristics derived from fisheye photography. Heat exchange driven by hyporheic flow through the channel step was a cooling effect during daytime, with a magnitude up to approximately 25% that of net radiation during the period of maximum daytime warming. Heat budget calculations in these headwater streams are complicated by the heterogeneity of incident solar radiation and channel geometry, as well as uncertainty in estimating heat and water exchanges between the stream and the subsurface via hyporheic exchange and heat conduction. Copyright © 2005 John Wiley & Sons, Ltd.
The Salmon Creek Watershed drains 325 km2 of forested terrain in the Cascade Mountains of western Oregon. Over a 30–year period (from 1955 to 1984) average daily maximum and minimum stream temperatures, calculated from the 10 warmest days of each year, have risen 6°C and 2°C, respectively. In contrast, a small decrease in maximum air temperatures was found over the same period. Regression analysis indicated a highly significant (p < 0.01) relationship between a cumulative index of forest harvesting and maximum stream temperatures. Maximum temperatures also tended to increase for several years following major peak flow events. The interaction between harvest activity (logging and road construction), changing forest and riparian management practices and the occurrence of natural hydrologic events (peak flows and associated mass soil movements) tend to obscure specific cause-and-effect relationships regarding long-term changes in maximum stream temperature.
Summary1. The thermal regime of rivers plays an important role in the overall health of aquatic ecosystems, including water quality issues and the distribution of aquatic species within the river environment. Consequently, for conducting environmental impact assessments as well as for effective fisheries management, it is important to understand the thermal behaviour of rivers and related heat exchange processes.2. This study reviews the different river thermal processes responsible for water temperature variability on both the temporal (e.g. diel, daily, seasonal) and spatial scales, as well as providing information related to different water temperature models currently found in the literature.3. Water temperature models are generally classified into three groups: regression, stochastic and deterministic models. Deterministic models employ an energy budget approach to predict river water temperature, whereas regression and stochastic models generally rely on air to water temperature relationships.4. Water temperature variability can occur naturally or as a result of anthropogenic perturbations, such as thermal pollution, deforestation, flow modification and climate change. Literature information is provided on the thermal regime of rivers in relation to anthropogenic impacts and such information will contribute to the better protection of fish habitat and more efficient fisheries management.
In order to gain insight into the effect of watershed conditions on fluctuations in stream water temperature, we statistically analyzed water temperature data for 1 year, using root mean square (Rms) and harmonic (A Amplitude, φ delay time) methods. The average values of delay time (days) between air and water temperatures (T
a and T
w) of small (< 0.5 ha), medium (0.5–100 ha) and large (> 100 ha) watersheds were 4.53 ± 0.82 days, 11.83 ± 3.88 days and 4.45 ± 1.52 days, respectively. Fluctuations in stream water temperature expressed by Rms (Rms T
w/Rms T
a) and harmonic methods (A −T
w/A −T
a) in the medium-sized watersheds with moderate slope gradients were 0.37 ± 0.09 and 0.56 ± 0.14, respectively. These values increased in the larger watersheds with low slope gradients, including five large rivers covered by various landscapes, with their averages of 0.53 ± 0.09 and 0.78 ± 0.09, respectively, indicating the influences of solar radiation and heat transfer processes. In the smaller watersheds with high slope gradients, these values were 0.73 ± 0.02 and 0.87 ± 0.03, respectively, suggesting that shorter passage time affected water temperatures. With respect to forest type, these values at badly managed hinoki forest watersheds (0.45 ± 0.04 and 0.73 ± 0.07) were larger than those at broadleaf forest (0.34 ± 0.04 and 0.51 ± 0.12) and well-managed hinoki forest (0.33 ± 0.04 and 0.51 ± 0.07) watersheds, indicating different proportions of flow paths.
Spatial thermal patterns and the sources of those patterns were examined in four mountain streams in northeast Oregon and Idaho during hot summer days in 2001. Summer baseflow ranged from <0.007 to 0.22 m3/s. Maximum and minimum temperatures increased in the downstream direction, with the diurnal range decreasing with increasing stream size. Each stream was thermally diverse spatially, diurnally, and seasonally, with unique landform and geologic influences on the daily temperature maxima. Insolation was the most important predictor for maximum temperature at each stream. Minimum daily temperatures were less variable than maxima and followed a seasonal and elevation gradient, with minimum air temperature a more important predictor than either the insolation from the previous day or channel features. Models for each stream using insolation and physical habitat characteristics explain 32 to 67% of maximum temperature and 17 to 51% of minimum temperature variability. Groundwater inputs moderated thermal conditions, particularly local maxima, but did not subsume the predominant temperature range controls of insolation and air temperature.
Linear Mixed-Effects * Theory and Computational Methods for LME Models * Structure of Grouped Data * Fitting LME Models * Extending the Basic LME Model * Nonlinear Mixed-Effects * Theory and Computational Methods for NLME Models * Fitting NLME Models
estimate relative effects of channel morphologic features on the extent of the hyporheic zone, on hyporheic exchange flow, and on the residence time of stream water in the hyporheic zone. Four stream reaches were compared in order to examine the influence of stream size and channel constraint. Within stream reaches, the influence of pool-step or pool-riffle sequences, channel sinuosity, secondary channels, and channel splits was examined. Results showed that the way in which channel morphology controlled exchange flows differed with stream size and, in some cases, with channel constraint. Pool-step sequences drove hyporheic exchange in the second-order sites, creating exchange flows with relatively short residence times. Multiple features interacted to drive hyporheic exchange flow in the unconstrained fifth-order site, where pool-riffle sequences and a channel split created exchange flows with short residence times, whereas a secondary channel created exchange flows with long residence times. There was relatively little exchange flow in the bedrock-constrained fifth-order site. Groundwater flow models were effective in examining the morphologic features that controlled hyporheic exchange flow, and surface-visible channel morphologic features controlled the development of the hyporheic zone in these mountain streams. INDEX TERMS: 1824
While external factors (drivers) determine the net heat energy and water delivered to a stream, the internal structure of a stream determines how heat and water will be distributed within and exchanged among a stream's components (channel, alluvial aquifer, and riparian zone/floodplain). Therefore, the interaction between external drivers of stream temperature and the internal structure of integrated stream systems ultimately determines channel water temperature. This paper presents a synoptic, ecologically based discussion of the external drivers of stream temperature, the internal structures and processes that insulate and buffer stream temperatures, and the mechanisms of human influence on stream temperature. It provides a holistic perspective on the diversity of natural dynamics and human activities that influence stream temperature, including discussions of the role of the hyporheic zone. Key management implications include: (1) Protecting or reestablishing in-stream flow is critical for restoring desirable thermal regimes in streams. (2) Modified riparian vegetation, groundwater dynamics, and channel morphology are all important pathways of human influence on channel-water temperature and each pathway should be addressed in management plans. (3) Stream temperature research and monitoring programs will be jeopardized by an inaccurate or incomplete conceptual understanding of complex temporal and spatial stream temperature response patterns to anthropogenic influences. (4) Analyses of land-use history and the historical vs contemporary structure of the stream channel, riparian zone, and alluvial aquifer are important prerequisites for applying mechanistic temperature models to develop management prescriptions to meet in-channel temperature goals.
This paper focuses on the Akaike information criterion, AIC, for linear mixed-effects models in the analysis of clustered data. We make the distinction between questions regarding the
population and questions regarding the particular clusters in the data. We show that the AIC in current use is not appropriate for the focus on clusters, and we propose instead the conditional Akaike information and
its corresponding criterion, the conditional AIC, cAIC. The penalty term in cAIC is related to the effective degrees of freedom ρ for a linear mixed model proposed by Hodges & Sargent (2001); ρ reflects
an intermediate level of complexity between a fixed-effects model with no cluster effect and a corresponding model with fixed
cluster effects. The cAIC is defined for both maximum likelihood and residual maximum likelihood estimation. A pharmacokinetics data application is
used to illuminate the distinction between the two inference settings, and to illustrate the use of the conditional AIC in model selection.
Executive summary: Regional assessment of stream temperatures across northern California and their relationship to various landscape-level and site-specific attributes, Forest Science Project report
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Status review of chinook salmon from Washington
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L. J. Madsen, Department of Statistics, Oregon State University, 44