Journal Articles

Three Responses to Small Changes in Stream Temperature by Autumn-Emerging Aquatic Insects
Li, J., S.L. Johnson, J.B. Sobota

In this experimental study, we examined how small increases in summer water temperatures affected aquatic insect growth and autumn emergence. We maintained naturally fluctuating temperatures from 2 nearby streams and a 3rd regime, naturally fluctuating temperatures warmed by 3–5 degrees Celsius, in flow-through troughs from mid-summer until autumn. We added selected abundant Ephemeroptera, Plecoptera, and Trichoptera species to the 3 treatments in late July and observed emergence until early December. We described the taxon-specific responses of the caddisfly Psychoglypha bella and the mayfly Paraleptophlebia bicornuta, both of which survived well in the troughs (67–86%), and the stonefly Mesocapnia projecta, which we did not collect in mid-summer but had colonized all experimental troughs by October. We observed primarily phenological rather than morphological responses to higher water temperatures. The most synchronous emergence of male and female P. bella and P. bicornuta occurred in the trough with the coolest temperatures. Only P. bella emerged asynchronously from the trough with the warmest temperatures. The decreases in synchrony were largely the result of earlier emergence of males. Paraleptophlebia bicornuta were larger and tended towards asynchrony in the trough with water (and temperatures) from their natal stream. Individuals in the trough with the warmest temperature were smaller than individuals in other troughs, but did not but did not emerge earlier.

DISCIPLINE: Aquatic Invertebrates    STUDY: Trask    TYPE: Journal Articles    TAGS: autumn emergence, aquatic insect growth, asynchronous emergence, water temperatures
Short-Term Response of Dicamptodon tenebrosus Larvae to Timber Management in Southwestern Oregon
Leuthold N., M.J. Adams, J.P. Hayes

In the Pacific Northwest, previous studies have found a negative effect of timber management on the abundance of stream amphibians, but results have been variable and region specific. These studies have generally used survey methods that did not account for differences in capture probability and focused on stands that were harvested under older management practices. We examined the influences of contemporary forest practices on larval Dicamptodon tenebrosus as part of the Hinkle Creek paired watershed study. We used a mark–recapture analysis to estimate D. tenebrosus density at 100 1-m sites spread throughout the basin and used extended linear models that accounted for correlation resulting from the repeated surveys at sites across years. Density was associated with substrate, but we found no evidence of an effect of harvest. While holding other factors constant, the model-averaged estimates indicated; 1) each 10% increase in small cobble or larger substrate increased median density of D. tenebrosus 1.05 times, 2) each 100-ha increase in the upstream area drained decreased median density of D. tenebrosus 0.96 times, and 3) increasing the fish density in the 40 m around a site by 0.01 increased median salamander density 1.01 times. Although this study took place in a single basin, it suggests that timber management in similar third-order basins of the southwestern Oregon Cascade foothills is unlikely to have short-term effects of D. tenebrosus larvae. 

DISCIPLINE: Amphibians    STUDY: Hinkle Creek    TYPE: Journal Articles    TAGS: Timber Management, Capture Probability, Harvest, Larva
Sampling Headwater Stream Networks for Spatial Autocorrelation Detection and Autocovariance Parameter Estimation
Som, N., L.M. Ganio, R.E. Gresswell, D. Hockman-Wert

Spatial autocorrelation is common in data collected for ecological studies, and the use of statistical models for spatial autocorrelation has evolved. Initially, these models were used to improve linear model parameter estimation uncertainty, but more recently ecologists have considered spatial autocorrelation as a valuable tool for describing ecological patterns. The structure and water-driven continuity of stream-networks makes these landscapes unique, and has prompted development of new models for describing spatial autocorrelation within these networks. We evaluate the spatial autocorrelation detection and parameter estimation of four sampling protocols applied to complete censuses of coastal cutthroat trout (Oncorhynchus clarkii clarkii) habitat unit fish counts. We consider two cluster- and two non cluster-based sampling protocols. Spatially distributed clusters were the most apt to contain spatial autocorrelation. Spatial autocorrelation detection was also associated with headwater basin attributes. Differences among sampling protocols in regards to autocorrelation parameter estimation were less distinct.

DISCIPLINE: Fisheries    STUDY: Hinkle Creek    TYPE: Journal Articles    TAGS: Spatial autocorrelation, parameter estimation, cluster-based sampling protocols
Effect of contemporary forest harvesting practices on headwater stream temperatures: Initial response of the Hinkle Creek catchment, Pacific Northwest
Kibler Kelly M., Skaugset, Arne, Ganio, Lisa M., Huso, Manuela M.

We investigated the effect of contemporary forest harvesting practices on warm-season thermal regimes of headwater streams using a Before-After-Control-Intervention (BACI) design within a nested, paired watershed study. We applied harvesting treatments to four headwater tributaries of Hinkle Creek, designed in accordance with the Oregon Forest Practices Act. Therefore, fixed-width buffer strips containing overstory merchantable trees were not left adjacent to the four non-fish-bearing streams. The summer following harvesting, we observed a variable temperature response across the four harvested streams. Mean maximum daily stream temperatures ranged from 1.5 C cooler to 1.0 C warmer relative to pre-harvest years. We also observed significantly lower minimum and mean daily stream temperatures, and recorded particularly low temperatures in treatment streams on days that minimum stream temperatures in reference streams were high. At the watershed scale, we did not observe cumulative stream temperature effects related to harvesting 14% of the watershed area in multiple, spatially-distributed harvest units across four headwater catchments. At the watershed outlet, we observed no change to maximum, mean, or minimum daily stream temperatures. We attribute the lack of consistent temperature increases in headwater streams to shading provided by a layer of logging slash that deposited over the streams during harvesting, and to increased summer baseflows.

DISCIPLINE: Hydrology & Water Quality    STUDY: Hinkle Creek    TYPE: Journal Articles    TAGS: Stream temperature, Forest management, Canopy closure, Impact assessment, Headwater streams, Cumulative effects, Hinkle, Oregon, Paired Watershed, Forest Hydrology
Arthropod Prey for Riparian Associated Birds in Headwater Forests of the Oregon Coast Range
Hagar J.C., J. Li, J. Sobota, S. Jenkins

Streamside habitat is important for many terrestrial wildlife species. However, mechanisms underlying the riparian associations of some terrestrial species have not been well studied, particularly for headwater drainages. We investigated the diets of and food availability for four bird species associated with riparian habitats in montane coastal forests of western Oregon, USA. We examined variation in the availability of arthropod prey as a function of distance from stream. Specifically, we tested the hypotheses that (1) emergent aquatic insects were a food source for insectivorous birds in headwater riparian areas, and (2) the abundances of aquatic and terrestrial arthropod prey did not differ between streamside and upland areas during the bird breeding season. We found that although adult aquatic insects were available for consumption throughout the study period, they represented a relatively small proportion of available prey abundance and biomass and were present in only 1% of the diet samples from only one of the four riparian-associated bird species. Nonetheless, arthropod prey, comprised primarily of insects of terrestrial origin, was more abundant in streamside than upland samples. We conclude that food resources for birds in headwater riparian areas are primarily associated with terrestrial vegetation, and that bird distributions along the gradient from streamside to upland may be related to variation in arthropod prey availability.

DISCIPLINE: Wildlife    STUDY: Trask    TYPE: Journal Articles    TAGS: Bird, arthropod prey, aquatic insects, understory


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