The Plecoptera community of a small stream in Oregon,U.S.A. *

The Plecoptera community of a small woodland stream in Oregon was studied by examining density and species composition. Four sites were studied using benthos sampling for larvae and emergence trap collections for adults. Sixteen genera and forty-three species were identified with most species occurring in relatively low numbers. A comparison with the species list from an earlier study suggested that the species composition has not changed markedly in 40 years but there were several changes in relative abundance. Species diversity of stoneflies decreased with distance from the headwaters. These changes were correlated with decrease in habitat complexity, decrease in stability of the substrate, and increase in water depth. Examples of longitudinal succession are given as a method enabling the large number of species to partition the habitat. Concurrent benthos and emergence sampling demonstrated differences in emergence success that were correlated with habitat suitability.     

Emergence,maturation and upstream oviposition flights of Plecoptera from the Breitenbach,with notes on the adult phase as a possible control of stream insect populations

Upstream oviposition flights of several Plecoptera species of the genera Leuctra, Nemoura, Isoperla and Siphonoperla along the Breitenbach, Hesse, Germany are inferred from 1. oviposition occuring upstream from emergence areas; 2. size differences and size-shifts between emerging and egg-laying females; 3. concentration of oviposition in upstream sections of the emergence area. The last point relies on direct catches of egg-laying females with sticky traps, and on over-representation of old, mature females in upstream emergence traps towards the end of, or even after actual emergence periods. Criteria for age class discrimination of the respective taxa are described. The validity of the present and of other indirect evidence for directed adult flights and the significance of adult upstream displacement are discussed. Optical orientation cues are suggested. Females of Leuctra prima and Siphonoperla torrentium are shown to gain 25–50% dry weight by feeding in the terrestrial environment; general information indicates many other Plecoptera may be similar in this respect. Terrestrial adult life is shown to last for 3–8 weeks. This long time, evidence of important flight activity and feeding together suggest that the terrestrial phase is spent as an active adult, the inevitable risks of which may form an important control of population dynamics.     

Diurnal cortisol rhythms among Latino immigrants in Oregon, USA

ABSTRACT: One of the most commonly used stress biomarkers is cortisol, a glucocorticoid hormone released by the adrenal glands that is central to the physiological stress response. Free cortisol can be measured in saliva and has been the biomarker of choice in stress studies measuring the function of the hypothalamic-pituitary-adrenal axis. Chronic psychosocial stress can lead to dysregulation of hypothalamic-pituitary-adrenal axis function and result in an abnormal diurnal cortisol profile. Little is known about objectively measured stress and health in Latino populations in the United States, yet this is likely an important factor in understanding health disparities that exist between Latinos and whites. The present study was designed to measure cortisol profiles among Latino immigrant farmworkers in Oregon (USA), and to compare quantitative and qualitative measures of stress in this population. Our results indicate that there were no sex differences in average cortisol AUCg (area under the curve with respect to the ground) over two days (AvgAUCg; males = 1.38, females = 1.60; p = 0.415). AUCg1 (Day 1 AUCg) and AvgAUCg were significantly negatively associated with age in men (p < 0.05). AUCg1 was negatively associated with weight (p < 0.05), waist circumference (p < 0.01) and waist-to-stature ratio (p < 0.05) in women, which is opposite to the expected relationship between cortisol and waist-to-stature ratio, possibly indicating hypothalamic-pituitary-adrenal axis dysregulation. Among men, more time in the United States and immigration to the United States at older ages predicted greater AvgAUCg. Among women, higher lifestyle incongruity was significantly related to greater AvgAUCg. Although preliminary, these results suggest that chronic psychosocial stress plays an important role in health risk in this population. (271 words).     

Biogeochemistry of unpolluted forested watersheds in the Oregon Cascades: temporal patterns of precipitation and stream nitrogen fluxes

We analyzed long-term organic and inorganic nitrogen inputs and outputs in precipitation and streamwater in six watersheds at the H.J. Andrews Experimental Forest in the central Cascade Mountains of Oregon. Total bulk N deposition, averaging 1.6 to 2.0 kg N ha^–1 yr^–1, is low compared to other sites in the United States and little influenced by anthropogenic N sources. Streamwater N export is also low, averaging <1 kg ha^–1 yr^–1. DON is the predominant form of N exported from all watersheds, followed by PON, NH₄-N, and NO₃-N. Total annual stream discharge was a positive predictor of annual DON output in all six watersheds, suggesting that DON export is related to regional precipitation. In contrast, annual discharge was a positive predictor of annual NO₃-N output in one watershed, annual NH₄-N output in three watersheds, and annual PON output in three watersheds. Of the four forms of N, only DON had consistent seasonal concentration patterns in all watersheds. Peak streamwater DON concentrations occurred in November-December after the onset of fall rains but before the peak in the hydrograph, probably due to flushing of products of decomposition that had built up during the dry summer. Multiple biotic controls on the more labile nitrate and ammonium concentrations in streams may obscure temporal DIN flux patterns from the terrestrial environment. Results from this study underscore the value of using several watersheds from a single climatic zone to make inferences about controls on stream N chemistry; analysis of a single watershed may preclude identification of geographically extensive mechanisms controlling N dynamics.     

Drift patterns in a high Andean stream

The drifting of invertebrates was sampled for six 24-hour periods from September 1976 to July 1977 in a small stream of the paramo of the Ecuadorian Andes. The composition of the drift is similar to that of the benthos, though percentages may differ markedly. Drift is relatively constant throughout the year, except in March when unusually high rates were noted; at this same period a marked reduction in the benthos was also observed. Diel periodicities in the drift are unclear, although on the whole drift is more important during the daytime; when individual data series are analyzed, weak patterns of day or night drifting can be recognized in some groups. The input of insects through drift from the small streams is thought to be an important source of food for the salmonid fish inhabiting the larger torrents.     

Pathways of soil genesis in the Coast Range of Oregon, USA

Background and Aims

Soil chronosequences on marine terraces along the Pacific Coast of California and Oregon show evidence of podzolization, though soils ultimately evolve to Ultisols. It is not clear if this pathway of soil evolution can be extended to the humid, inland Oregon Coast Range.

Methods

We analyzed soil properties for a fluvial terrace chronosequence sampled along the Siuslaw River (Oregon, USA) about 50 km from the Pacific coast. The seven terraces ranged in age from <3.5 ky to nearly 1,000 ky.

Results

There was no evidence of early podsolization. Instead, evidence was found that andisolization starts early and occurs even in older soils when pedogenic iron accumulation and clay synthesis and illuviation dominate. Soils develop the morphology characteristic of Ultisols sometime between 20 and 70 ky, but high levels of oxalate extractable iron and aluminum satisfy criteria of an andic subgroup. Alfisols are not formed as an intermediary stage.

Conclusions

The lack of Spodosols inland is due to the inland shift from udic to ustic or xeric moisture regime, which favors summer drying and ripening of short-range order minerals rather than deep leaching or translocation. Other factors are higher pH, different organic chemistry and faster calcium cycling under the Douglas fir inland when compared to the Sitka spruce of the coastal terraces.     

Spatial variation of modern pollen in Oregon and southern Washington, USA

Surface sediments from 95 lakes provide information on the spatial variation of modern pollen spectra in Oregon and southern Washington. Percentages for 13 pollen types were compared within and between vegetation zones to characterize regional patterns of pollen spectra. The percentage data were also compared with climate variables to determine relationships between pollen percentages and regional climate gradients. The composition of modern pollen spectra corresponds well with the distribution of the pollen producers. Most pollen assemblages were generally dominated by Pinus, but those west of the Cascade Range were dominated by Alnus. Low percentages of Pseudotsuga/Larix, Tsuga mertensiana, Abies, and Picea pollen coincided with local occurrence of the trees. The distributions of the pollen data were arranged along gradients of temperature and effective moisture. West of the Cascade Range, Alnus, Tsuga heterophylla, Pseudotsuga/Larix, and Cupressaceae pollen were abundant and correlate well with moderate temperature and high effective moisture. In the shrub-steppe and woodlands east of the Cascade Range, where effective moisture is low, Artemisia, Cupressaceae, and Pinus pollen were dominant. At high elevations, Pinus, T. mertensiana, Abies, and Picea were common pollen types in areas with short growing seasons and high effective moisture. Pollen percentages collected from lake surface sediments, moss polsters, and soils were compared within a number of vegetation types to assess their similarity. The three types of sample yielded similar results for forested areas, but lake sediment samples from upper- and lower-treeline sites captured a more regional picture of the vegetation.     

Emergence chronology of brook charr,Salvenus fontinalis,alevins in an acidic stream

Synopsis The emergence chronology of brook charr alevins in the Chikanishing River, Ontario, Canada and the concurrent changes in stream chemistry resulting from acidic snowmelt runoff were examined during the spring, 1986–1988. Emergence patterns were similar among years with the most intense emergence (> 70%) occurring during the declining stream discharge following the spring flood. This period coincided with stream pH depressions (minimum pH 5.2) in 2 of 3 years, suggesting emergence behaviour frequently subjects the earliest free-swimming life interval of brook charr to episodic acidification events.     

Probabilistic modeling and mapping of plant indicator species in a Northeast Oregon industrial forest,USA

Managing forest ecosystems for sustainable, multiple use requires forest resource managers to understand and predict how plant species composition and distribution varies across environmental gradients and responds to landscape scale disturbances. This study demonstrates predictive vegetation modeling and mapping for a Northeast Oregon forest using non-parametric Multiplicative Regression (NPMR) with presence/absence data for the species Clintonia uniflora (CLUN) and a set of stand structural and raster-based predictor variables. NPMR is a flexible probability modeling system that can find the best subset of habitat factors influencing species occurrence. NPMR was compared with logistic regression (LR) by building reduced models from variables selected as best by NPMR and full models from variables identified as significant with a forward stepwise process and further manual testing. log β was used to select models with the highest predictive capability. NPMR models were less complex and had higher predictive capability than LR for all modeling approaches. Spatial coordinates were among the most powerful predictors and the modeling approach with physiographic and stand structural variables together was the most improved relative to the average frequency of occurrence. GIS probability maps produced with the application of the physiographic models showed good spatial congruence between high probability values and plots that contained CLUN. NPMR proved to be a reliable probability modeling and mapping tool that could be used as the analytical link between monitoring and quantifying the status and trends of vegetation resources.     

Life Cycles and Emergence of Ephemeroptera and Plecoptera from Myrkdalsvatn,an Oligotrophic Lake in Western Norway

Comparative data are presented on nymphal growth and adult emergence for Nemoura avicularis, N. cinerea (Plecoptera), Siphlonurus aestivalis, S. lacustris and Leptophlebia vespertina (Ephemeroptera) from lake Myrkdalsvatn, western Norway. These species are all univoltine in Myrkdalsvatn. However, they show different nymphal growth patterns and emergence periods. The timing of emergence in Plecoptera was largely determined by water temperature, and in the Ephemeroptera by changes in both water temperature and cloud cover.     

Riverscape-level patterns of riparian plant diversity along a successional gradient, Willamette river, Oregon

Riparian forest communities dominated by Populus balsamifera ssp. trichocarpa L. (Torr. and Gray ex Hook.) Brayshaw are important contributors to biodiversity in terrestrial and aquatic ecosystems of the Western United States. Species composition along a successional gradient from stand initiation to late-succession of P. balsamifera-dominated riparian forests was investigated along 145 km of the Willamette River, Oregon. There were 151 total species encountered across 28 stands and a mean species richness of 33.3 species per stand. Young stands were dominated by P. balsamifera and Salix tree spp. and opportunistic herbaceous species. Understory trees, shrubs, and herbaceous species as well as late-successional tree species established 12–15 years after stand initiation. Fraxinus latifolia Benth. was the dominant late-successional tree species. Vertical structural diversity, P. balsamifera mean diameter at breast height, large tree biomass, and stand age were strongly correlated with understory species presence and abundance based on non-metric multidimensional scaling (NMS) ordination. There were no young stands on mid and high terraces and this was reflected in geomorphic position being strongly correlated with the stand age gradient. Abundance of Phalaris arundinacea L. an invasive grass species, was also significantly correlated with plant species composition and abundance. This study indicates that Willamette River riparian forests are diverse and therefore important to the biodiversity of the Willamette River valley and that their presence as a mosaic of communities of different successional stages may be threatened by human interventions, including influences exerted by introduced plant species.     

The dynamics of old-growth Pseudotsuga forests in the western Cascade Range,Oregon, USA

Size and age structure, spatial analysis, and disturbance history were used to analyse the population structures and regeneration patterns of 8 conifer stands in the central western Cascade Range, Oregon, USA. Variation in forest structure reflected the effects of frequent (20–50 yr) low-intensity fires and treefalls, infrequent (100–200 yr) localised, intense fires, and extensive fires that resulted in stand replacement (every ca 400 yr?).The amount of canopy removed and the size of openings formed by fires and treefalls were important determinants of subsequent forest establishment. Single or several species stands of Pseudotsuga and/or Abies procera, or mixed species stands of Pseudotsuga, Abies procera, Tsuga heterophylla and Abies amabilis established in openings where intense fires had removed most of the canopy trees over several ha. Multi-tiered and multi-aged stands, often containing 400–500 yr-old Pseudotsuga and variously-sized more or less even-aged patches of younger shade tolerant Tsuga heterophylla and/or Abies amabilis, occurred where lower-intensity fires did not kill all overstorey trees or where treefalls occurred after the initial fire.Current regeneration processes are influenced by overstorey composition, the availability and size of canopy openings, and the availability of substrates suitable for regeneration. Tsuga heterophylla and Abies amabilis established under Pseudotsuga menziesii and Abies procera canopies and in small canopy openings (<400 m²) created by windfalls, but rarely under Tsuga. Down logs and stumps were favoured establishment sites for Tsuga.The disturbance regime of fires of low-to moderate-intensity, windfalls, and occasional fires that result in extensive stand replacement contrasts with the pattern of infrequent, catastrophic disturbances proposed for other areas of the Pacific Northwest. Although fires at stand establishment commonly determine much of the composition, structure, and subsequent stand development, canopy replacement by shade tolerant species occurs as the different life histories of the species are expressed in response to various disturbances differing in intensity and frequency. Such a non-equilibrium view of vegetation change is consistent with many other fire-dominated forests of the western United States.     

Emergence and lateral dispersal of adult Plecoptera and Trichoptera from Broadstone Stream, U.K.

1. Emergence and inland dispersal of adult stoneflies (Plecoptera) and caddisflies (Trichoptera) from Broadstone Stream, an acidic and iron-rich stream in southern England, were studied over 10 months in 1996–1997. Fifteen pyramidal emergence traps were placed randomly in a 200-m stretch. Three Malaise traps were placed above the stream and six more on each side (one wooded, one open) along a transect at distances of 1, 15, 30, 45, 60 and 75 m from the channel. 2. More than 16 000 stoneflies, belonging to 11 species, and just under 400 caddisflies (22 species) were caught. Four dominant stoneflies (Leuctra fusca, Leuctra nigra, Leuctra hippopus and Nemurella pictetii) accounted for 96% and 95% of the catches in the emergence and Malaise traps, respectively. Two caddisflies (Plectrocnemia conspersa and Potamophylax cingulatus) accounted for 63% of the catch in the Malaise traps. Few caddisflies were taken in emergence traps. 3. The emergence periods of L. fusca, L. nigra and L. hippopus were well-defined and unimodal, whereas that of N. pictetii was prolonged and erratic. Overall, more females (1285) emerged than males (740). 4. Female stoneflies and caddisflies were in the majority in the Malaise traps above the stream. On land, significantly more females than males of L. fusca, L. nigra and P. cingulatus were caught. The sex ratio of the remaining species did not deviate significantly from 1:1. 5. The three Malaise traps placed above the stream caught most of the stoneflies though there was also dispersal away from the channel, the numbers caught declining with distance. Exponential models explained between 67% and 99% of the variation in numbers of individuals with distance from the channel in the four common stoneflies. Half the individuals went less than 11–16 m from the stream, while 90% travelled less than 51 m. Significantly more L. nigra and N. pictetii were caught in the woodland than on the open side, whereas L. hippopus showed no overall preference for either side.     

Long-term patterns of invertebrate stream drift in an Australian temperate stream

1. Invertebrate stream drift was sampled bimonthly in the Acheron River, Victoria, Australia, over a period of 18 months. Replicated hourly samples were collected over a 25-h period on each sampling date. A total of 194 taxa were identified in the drift. However, total drift density was dominated by few taxa. 2. Some evidence was obtained for a seasonal pattern in drift: this was most pronounced in relative abundances of individual taxa and the composition of the drift, rather than in total drift densities. Most of the commonly collected taxa reflected the seasonal pattern of total drift. However, some of the common taxa did not. 3. A small number of taxa showed behavioral drift, with a nocturnal increase in drift densities. One species of ‘Baetis’ drifted in high densities over short periods of time around dusk and dawn. It did not drift in higher densities during the night than during the day. The results emphasize the need for drift studies to be more rigorously designed than is typically the case.     

Assessing channel-forming characteristics of an impacted headwater stream in Ohio, USA

Since the start of European settlement in Ohio the landscape has been greatly modified to accommodate anthropogenic land uses. This, in turn, has altered the hydrologic characteristics of many streams from those that are stable channel systems in dynamic equilibrium to those of modified incised channels that are more characteristic of anthropogenic influences. As stream restoration practices gain importance and prevalence there is a need to prioritize project funds based on the restoration potential of a stream. Regional curves that relate channel-forming geometry to drainage area, and applications of channel-forming discharge concepts, are tools that are used in making restoration and management decisions. Regional curves are usually developed for unmodified natural streams and/or gaged river systems and not for small, ungaged modified channels that are common throughout agricultural areas or mixed use watersheds. This study focuses on the development and potential usefulness of regional curves and channel-forming discharge concepts for Mac-o-chee Creek, a small, ungaged headwater stream system in Ohio. Results show that these approaches and a weight of evidence analysis could be useful in providing information for management and restoration decisions on these small stream systems as well as aiding in the assessment and modeling of trends within these streams with dynamic hydrologic conditions due to changes in land use/land cover.     

Movement patterns and ecology of Pteronarcys nymphs (Plecoptera)

SUMMARY. 1. Individually tagged Pteronarcys californica (Newport) nymphs were caught and recaptured over a 3-month period to determine their movement patterns and home range size. Sex/age structure, population density, and food habits (from gut contents) were also recorded. More than 1000 nymphs were tagged of which 256 (25%) were recaptured at least once. Tagged insects were confined to contiguous fast water, cobble riffles. Low velocity, silt-bottomed pools acted as barriers.
2. This stonefly has a 3-year life cycle although only the two oldest nymphet size-classes were tagged. Females were larger than males at all ages. The population sex ratio was skewed 60:40 towards females. Densities averaged 1.7 m⁻²±0.17 SE (range 0–19 m⁻²).
3. Most movements were short, indicating that a majority of the stoneflies stayed within a few meters of their first capture point (mean 1.8 m downstream ±0.51 SE, range 44 m downstream to 40 m upstream). Significant patch size is a stream reach 24 m long that would contain 85% of the average individual's movements. Time between captures averaged 16 d ±0.734 SE (maximum 81 d). Eight individuals were notable for extremely rapid upstream movements ranging from 6 to 22 m d⁻¹.
4. Frequency of movements up and downstream differed significantly between the sexes. Pteronarcys distribution was clumped with certain quadrate representing'zones of attraction.'The stoneflies moved rapidly between zones, then stayed many days in those areas. Movements differed significantly from random walk models.
5. Guts contained 75% diatoms, 15% vascular plant material, and 8% animal remains. Females ate significantly more diatoms than males on a volumetric basis.     

Laboratory studies of egg development and diapause in Isoperla obscura (Plecoptera) from a mountain stream in Norway

SUMMARY 1. A laboratory study of egg development of the stonefly Isoperla obscura (Zetterstedt) collected from the stream Flybekken (southern Norway, 61°25'N, 8°48'E, 1373 m a.s.l.) showed a short diapause followed by a prolonged period of postdiapause quiescence.
2. Diapause occurred over a wide range of temperatures (−20°C to +8°C), but 0–1°C was the most favourable for fast diapause development and successful hatching. Diapause development required temperatures below 12°C, but sub-zero diapause temperatures increased mortality during the postdiapause phase, as well as reducing hatching success.
3. The threshold for initiation of postdiapausal development was about 1–2°C. Development rate increased and variation in development time decreased at higher water temperatures. These may be important characteristics to ensure seasonal and geographical synchrony of development in individual populations. Low postdiapausal temperatures were unfavourable, despite a subsequent increase in water temperature. No response to postdiapausal photoperiod was detected.
4. The results agreed well with conditions noted in the natural environment, and with the abundance of this species at high altitudes and latitudes in Fennoscandia. Nevertheless, Isoperla obscura also occurs in streams in the maritime parts of western Norway. The results of the present study suggest that egg development in these populations will prove to be different.     

Biodiversity loss in Appalachian headwater streams (Kentucky,USA): Plecoptera and Trichoptera communities

Government and academic studies indicate that many streams in the Appalachian Mountains have degraded biological communities stemming from a variety of regional landuses. Headwater stonefly (Plecoptera) and caddisfly (Trichoptera) assemblages were assessed between 1999 and 2004 in relation to pervasive landuse disturbances (coal mining and residential) in mountainous areas of eastern Kentucky, USA. Indicator metrics (richness, abundance, tolerance, and an observed/expected (O/E) null model) were compared among 94 sites with different land use pressures including least disturbed reference, residential, mining, and mixed mining and residential categories. Thirty-three stonefly species from 26 genera and 9 families were identified; Leuctra, Acroneuria, Haploperla, and Isoperla comprised the core genera that commonly decreased with disturbance. Caddisflies were represented by 48 species, 32 genera, and 14 families. Core caddisfly genera (Neophylax, Pycnopsyche, Rhyacophila, Lepidostoma, and Wormaldia) were extirpated from most disturbed sites. Species richness was significantly higher at reference sites and reference site mean tolerance value was lowest compared to all other categories; relative abundance of both orders was variable between disturbance groups. Non-metric multidimensional scaling (for riffle-dwelling stonefly and caddisfly genera) clustered reference sites distinctly from most other sites. The O/E index was highly correlated with individual habitat and chemical stressors (pH, conductivity) and on average, it estimated ~ 70% loss of common stoneflies and caddisflies across all disturbed landuse categories. Expected plecopteran and trichopteran communities were radically altered in streams draining mining and residential disturbance. Long-term impacts incurred by both landuses will continue to depress these vulnerable indigenous fauna.     

Emergence of some caddisflies (Trichoptera) from a wooded stream in southern Ontario

Twenty-eight species of nine families of caddisflies (Trichoptera) were identified in 170 samples taken over an 8-month period from five emergence traps placed on a second-order, forested, cold-stenothermal stream on the Niagara Escarpment, Ontario, Canada.A mean of 980.9 caddisflies m^–2 of streambed was obtained over the entire sampling period. Eleven common species accounted for 92.8% of the total emergence with specific proportions ranging from 23.8% (Wormaldia moesta) to 0.11 % (Rhyacophila sp.). The use of various kinds of traps in other studies and their effects on the detection of species composition and abundance are discussed and compared with the present study.Although the distributions of all the common species were invariant over time, four species showed low to high degrees of patchiness in the streambed; the other seven common species were uniformly distributed. However, a large residual variance suggested a subtle mechanism of microhabitat selection by the larvae and (or) pupae, not detectable by even the small emergence traps used.Both sexes of 15 species, only males of 4 and only females of 9 species were collected. Eight of the eleven common species showed significant departures from a balanced sex ratio and five exhibited a protandry of from 1 to 3 weeks. Neither this study nor others have been able to establish a predictable pattern of sex ratios in Trichoptera.The emergence periods and patterns of the eleven common species are described and compared with other studies. Of these common species, one emerged in the spring, seven during the summer and three during the late summer or early fall. Ten species had a short emergence period with a distinct peak and a significantly skewed pattern. One species,Parapsyche apicalis, exhibited a prolonged emergence period, no distinct peak and a significantly platykurtotic² pattern. With the exception ofLepidostoma sp. A, the emergence patterns of the common species were unimodal.