Small Forest Streams Research Articles

Plant Community Assembly Along Dendritic Networks of Small Forest Streams

Although insight into local and regional factors that structure communities is growing, the specific contribution of each of these factors generally remains unknown. Moreover, the extent to which community assembly is intrinsically indeterministic (i.e., the degree to which community composition depends on chance events) remains an open question. The complexity of this issue argues for field studies in a semicontrolled environment. We studied species richness and community composition of a guild of phreatophytes along dendritic networks of small forest streams in western Belgium. The streams, situated at the forest-covered headwaters of six different watersheds and characterized by homogeneous environmental conditions, impose spatial dispersal constraints to the plant species. This allowed us to assess the relative importance of deterministic processes guiding community assembly. More specifically, we focused on the role of species migration and colonization processes relative to local processes (competitive exclusion and passive habitat selection) on species richness and on community composition. Our analyses at three consecutive levels (species number, community composition, and species) revealed that plant community assembly along the stream systems is based on (1) historical and stochastic colonization events of species and (2) subsequent deterministic downstream dispersal processes. Apparently, due to the influence of historical chance events, deterministic processes do not necessarily result in community convergence. In addition we show that continuous downstream dispersal and colonization can compensate for local extinction processes. This is another piece of evidence that, when studying community composition, it is absolutely necessary to place communities in their spatial contexts.

Water temperature modelling in a small forested stream: implication of forest canopy and soil temperature

The demand for comprehensive environmental assessment of river ecosystem has increased for engineers and scientists. Accurate and versatile water temperature models are required to meet this demand. A number of hydrological models take vegetation and soil characteristics into account, but very few temperature models do. The objective of this paper is to incorporate soil temperature and vegetation as input variables in a deterministic heat budget model. The CEQUEAU hydrological and water temperature model was used to simulate water temperature in Catamaran Brook, a small catchment located in central New Brunswick. The model was modified by incorporating soil temperature as a parameter influencing the temperature of interflow, using the so-called force-restore method. Crown closure was also incorporated in the model as a factor influencing locally advected water using a negative exponential function. The modified model simulated daily water temperatures better than the original model. Root-mean-square error for a period of 5 years decreased from 2.10°C with the original model to 1.77°C with the modified model. Nash coefficient increased from 0.78 with the original model to 0.82 with the modified model. An analysis of residuals showed that the modified model is sensitive to additional parameters such as crown closure, especially for short time scales during periods of higher discharge and during extreme meteorological and hydrological events such as tropical storms.Key words: stream temperature, hydrology, deterministic model, CEQUEAU, forestry.

Ammonium and nitrate uptake lengths in a small forested stream determined by 15N tracer and short-term nutrient enrichment experiments

(2000). Ammonium and nitrate uptake lengths in a small forested stream determined by 15N tracer and short-term nutrient enrichment experiments. SIL Proceedings, 1922-2010: Vol. 27, No. 3, pp. 1320-1325.

Water temperature modelling in a small forested stream: implication of forest canopy and soil temperature

Water temperature modelling in a small forested stream: implication of forest canopy and soil temperature

Influence of salmon spawner densities on stream productivity in Southeast Alaska

We conducted this study to determine the relationship between salmon spawner abundance and stream biofilm and benthic macroinvertebrate abundance in Southeast Alaska. Experiments took place in outdoor artificial and natural streams. Six pink salmon (Oncorhynchus gorbuscha) carcass treatments (0.00, 1.45, 2.90, 4.35, 5.80, and 7.25 kg wet mass) placed in artificial channels were subsampled repeatedly for biofilm ash-free dry mass (AFDM), chlorophyll a, and macroinvertebrates. In a small (nonanadromous) forest stream, we sampled benthos throughout a 66-m reach 17 days after distributing 60 carcasses along the lower half of that reach. All response variables significantly increased in response to carcass additions in both artificial and natural streams. Chlorophyll a continued to increase across all loading rates, while AFDM and total macroinvertebrate densities showed no further response to loading beyond the first treatment (1.45 kg) in artificial streams. In the natural stream, AFDM and chironomid densities continued increasing across loading levels. These results indicated that increased spawner densities increased lower trophic level abundance until a trophic capacity was reached. Salmon escapement goals should consider food web effects, especially on trophic levels that support juvenile salmonids, that ultimately affect freshwater salmon production.

Stream lighting in five regions of North Island, New Zealand: Control by channel size and riparian vegetation

Lighting of streams profoundly influences their ecology, particularly through primary production and thermal behaviour. We used paired canopy analysers, instruments with fish‐eye lens imaging, to measure sunlight exposure of streams in five regions of North Island, New Zealand. Reach‐averaged stream lighting, at both water and bank level, was strongly influenced by riparian vegetation type. Pasture streams had comparatively high light exposure (median water level lighting = 45% of ambient), with most shading contributed by banks and overhanging herbs. Lighting was low in small forest streams (median = 1.3% for native forest, 1.2% for pine plantations), but increased sharply as the gap in the canopy widened with increase in channel width above c. 3.5 m. The understorey in pine plantations contributed more shade than the pines themselves: damage to this understorey (e.g., by goat browsing or floods) increased lighting markedly. Harvesting of pine plantations exposed streams to high light levels except where a riparian buffer was maintained. Periphyton biomass, varying over more than four orders of magnitude in the study streams, correlated broadly with lighting.

Use of the Wesche Method to Evaluate Fine-Sediment Dynamics in Small Boreal Forest Headwater Streams

Fine-sediment infiltration was monitored by the Wesche sediment method in the Copper Lake watershed, Newfoundland, Canada, from June 1993 to October 1994 as part of a multidisciplinary forest harvesting buffer zone research project. Initial study in Copper Lake has focused on evaluating the ability of this method to measure sediment dynamics in small boreal forest streams and in developing methods for data analyses and interpretation. The Wesche method discerned expected differences in sediment yield among sites due to logging-road construction and seasonal trends. Stream reaches impacted by bridge construction and culvert installation had significantly higher sediment accumulation than streams not affected by road construction. The Wesche method was a relatively simple and inexpensive way to compare fine sediment yield in streams with similar hydrologic regimes and was easily used in remote locations. Due to the nonparametric nature of the data collected with this method, randomization techniques were used to develop 95% confidence intervals around the mean. Use of these statistics allowed a significance level to be used in comparisons between stream reaches, an approach easily understood by the multidisciplinary audience interested in fishery–forestry research and management.

Plecopteran communities and annual emergence in five forest streams and two lake outlet streams of central Finland

The plecopteran fauna was studied by means of slit traps and hand net during the summers of 1982-1987. A total of 19 plecopteran species comprising c. 4 500 adults and c. 2 900 larvae were sampled in streams. Of these, Capnia atra, Capnopsis schilleri, Nemurella pictetii and Isoperla difformis were recorded for the first time in the streams of the province Pohjois-Häme (Tb). The plecopteran fauna was richest in the small forest streams and relatively poor in the largest outlet. Both, the character of the stream bed and the quantity and quality of food available seemed to be the most important factors affecting the occurrence of the plecopteran species. In the brooks the emergence of stoneflies had two clear maxima: one in spring and another in late autumn. Vernal species were Taeniopteryx nebulosa, Isoperla difformis, Nemoura avicularis, N. flexuosa and Leuctra hippo pus. Dominant species in the autumnal cathes were Leuctrafusca and Leuctra digitata. In the outlet streams the succession of emergence was somewhat different owing to the weak emergence and due to the cold summer with strong floods in 1987. The slit trap method worked well in the catching of stoneflies except during the snow melting seasons and the flood periods.

Factors influencing invertebrate drift in small forest streams, south-eastern Queensland

Aspects of invertebrate drift were investigated in four small rainforest streams in south-eastern Queensland. Hourly sampling in two streams revealed low drift rates and no distinct diel patterns. This may have been a consequence of the low flows experienced during the study period. The drift was dominated by Simuliidae, Chironomidae and to a lesser extent Tasmanocoenis sp. (Caenidae) and Cheumatopsyche sp. 6 (Hydropsychidae). Additional studies were undertaken to examine why some individuals of particular taxa drift while others (of the same taxa) remain in or on the substratum. Analysis of the relative gut fullness of simuliid and chironomid larvae showed that a higher proportion of non-drifting individuals had full or nearly full guts compared with those in the drift. Hungrier individuals of these two taxa may enter the drift as a food searching mechanism. An analysis of limb loss of hexapod nymphs indicated that a disproportionate number of individuals in the drift had one or more limbs missing compared with those that remained in the benthos. These data support the hypothesis that invertebrates present in the drift are less fit than non-drifters.

Problems of estimating population parameters and production of fish in a tropical rain forest stream, North Venezuela

The River Todasana is a small rain tropical forest stream emptying to the Caribbean Sea (Venezuela). Fish were sampled by electrofishing at three contiguous sites (pool, riffle, raceway). Nine species were recorded. Their mean biomass and production were: 43.72 kg ha−1 and 36.94 kg ha−1 yr−1, maximum: 55.47 kg ha−1 and 42.33 kg ha−1 yr−1, respectively.

Life on the edge: the ecology and life history of the tropidurine iguanid lizard Uranoscodon superciliosum

An Amazonian population of the iguanid lizard Uranoscodon superciliosum was studied in lowland tropical wet forest in central Pará, Brazil. These nonheliothermic lizards are restricted to densely vegetated habitats near (often over) water, particularly riverbanks and small forest streams, where they utilize small-diameter perches and feed on a wide variety of invertebrates, apparently at the water's edge. They mature at moderate to large size at an age of about 1.5 years. Production of moderate-sized clutches of eggs is seasonal, and reproduction and fat storage both cycle in association with rainfall and flooding. Although they occur in fairly high densities, social interaction is uncommon and sexual dimorphism is not pronounced. The ecology and life history of this lizard seem to be strongly influenced by the unusual habitat specialization.

Cost-Effective Selection of Culverts for Small Forest Streams

Cost-Effective Selection of Culverts for Small Forest Streams

The Foliage-as-Fruit Hypothesis and the Feeding Behavior of South Asian Ungulates

The foliage-as-fruit hypothesis argues that some plants may actually promote herbivory by large ungulates at the time of seed set to achieve seed dispersal. I examined a minimum condition of this hypothesis, that large herbivores actually ingest and pass small seeds from non-fleshy-fruited plants, by screening the dung of large indigenous mammals at the time of seed set. In a lowland reserve in South Asia, I examined the dung of Greater One-Horned Rhinoceros, Indian bison, and four native cervids for seeds from plants not producing fleshy fruits but found no obvious examples supporting the foliage-as-fruit hypothesis. Frequent, predictable, and widespread disturbance of grasslands by annual flooding and periodic fires provides sufficient microsites for the propagation of annual plants. Under this disturbance regime, selection pressure for megafauna-mediated dispersal, as described by the foliage-as-fruit hypothesis, is not apparent in plants of South Asian flood plains. JANZEN (1984) SUGGESTED THAT THE FOLIAGE of smallseeded plants may function ecologically as fruit, attracting large herbivores just as arils and fleshy berries attract and reward frugivores. In this intriguing evolutionary scenario, large ungulates, lured by a nutritious fodder bait, ingested minute seeds and fruiting stalks cloaked in leaf tissues. Long coexistence with a herbivorous megafauna provided small-seeded plants with a unique dispersal guild of wide-roaming mammals that defecated seeds into favorable germination sites (e.g., edges of game trails, small forest openings, wallow edges, river and stream banks). Implicit in the foliage-as-fruit (FAF) hypothesis is the prediction that plants subjected to herbivory are compensated by effective dispersal and recruitment away from the parent. Selection for tough, digestion-resistant seeds would increase survival past the Scylla and Charybdis of megafaunal dispersal: massive, grinding molars and lengthy gut

Three-component tracer model for stormflow on a small Appalachian forested catchment

A three-component 18O tracer model recognizing contributions of groundwater, soil water and channel precipitation was used to represent stormflow in Fish Run, a small Appalachian Plateau forest stream. The traditional two-component model recognizing “old” and “new” water stormflow sources failed to explain runoff events in Fish Run, often giving “old” water percentages of stormflow exceeding 100%. With the three-component model, channel precipitation contributions were computed from measured throughfall intensity and channel area. Example computations for a low-intensity frontal rainfall event using the three-component model gave stormflow contributions of 0.9% for channel precipitation, 24.1% for soil water and 75% for groundwater. Contributions of soil water to stormflows may explain levels of dissolved aluminum toxic to fish found in several Appalachian Plateau streams.

Processing of leaf litter in a northern jarrah forest stream, Western Australia: I. Seasonal differences

Seasonal differences in the processing of jarrah (Eucalyptus marginata) leaves were examined in a small forest stream of the Darling Range, Western Australia. Processing rates in both summer and winter were very low, placing this species in the ‘slow’ category (k < 0.005) of Petersen & Cummins (1974).

Processing of leaf litter in two northern jarrah forest streams, Western Australia: II. The role of macroinvertebrates and the influence of soluble polyphenols and inorganic sediment

The long-term processing of jarrah (Eucalyptus marginata) leaves was examined in a small forest stream to determine the role played by macroinvertebrates and the influence of soluble polyphenols in the leaves. The widely used exponential model of litter processing was inadequate in describing the fate of jarrah leaves. Decomposition occurred in three distinct phases and was best described by a quadratic model. After a substantial and rapid loss due to leaching, processing was virtually inhibited during summer and autumn, with no associated increase in the organic nitrogen content. Macroinvertebrates played a significant role in the latter part of the year, processing approximately 25% of the initial leaf mass. High levels of soluble polyphenols in the leaves had an inhibitory effect on the microbial colonization of jarrah leaves, as indicated by the organic nitrogen content. However, pre-leaching of these compounds had no effect on the rate of decomposition nor on the leaf bag fauna. Polyphenols released into the stream during summer, when flows are low, may reach high concentrations and contribute to the slow processing at this time. Leaf litter processing in a nearby sedimented stream was compared with that in the undisturbed stream. Sediment disrupted litter processing, virtually eliminating the contribution made by invertebrates. Smothered leaf bags became anoxic, restricting microbial activity and reducing leaf quality. The low processing rate of leaves in the sedimented stream was attributed to differences in the leaf bag fauna. Leaf bags in the sedimented stream had more animals but shredders were poorly represented and predators were the most abundant feeding group. The low density of shredders was more likely to be a result of the reduced availability of detritus rather than selective predation. Whatever the reason, invertebrates in the sedimented stream were denied access to an important source of energy. Inorganic sediment can have a profound effect on stream function by interfering with the shredder-CPOM pathway.

Bed load transport regime of a small forest stream

Bed load transport in a small gravel‐bedded stream on Chichagof Island, Alaska, was measured for 33 autumn storm flows during 1980 through 1985 to determine temporal and spatial trends within a riffle‐pool‐riffle sequence. The transport of fine sediment was more frequent than coarse sediment. Scouring of coarse material in the reach appeared to be triggered only by high flows with Tr ≥ 5 years. Within a given storm season, both antecedent storm history and cumulative flow (above the threshold for bed load transport, 0.25 m3 s−1) influenced bed load transport; however, the effects of these seasonal factors changed from year to year, presumably in response to storage and release of sediment around large organic debris upstream. Hysteresis loops existed in bed load transport versus flow plots for many storms. Fine bed load material was more subject to such differential transport over the storm hydrograph than was coarse material. During the 6‐year period, both riffles scoured along most of the channel width while the middle portion of the pool filled.

Diets of Amazonian Crocodilians

Differences in diets among Amazonian crocodilians can largely be related to habitat selec- tion. Caiman crocodilus, Melanosuchus niger and Paleosuchus palpebrosus, which occur around rivers and lakes have similar diets: small individuals eat invertebrates and large individuals eat invertebrates and fish. Juvenile Paleosuchus trigonatus, which live in small forest streams, eat larger numbers of terrestrial vertebrates than other similar-sized crocodilians. Large P. trigonatus eat many snakes and mammals but few fish. Mean, minimum, and maximum sizes of most prey types increase with crocodilian size for all species. There is an inverse relationship between the number of terrestrial invertebrates eaten and the number of fish eaten by different size classes of Caiman crocodilus, suggesting that mutually exclusive foraging modes are used for those prey categories.

Correlates of habitat favourability for benthic macroinvertebrates at five stream sites in an Appalachian Mountain drainage basin, U.S.A.

SUMMARY. Based on monthly samples taken over a 1‐year period, average density (individuals m‐2). average standing biomass and annual production of benthic macroinvertebrates were estimated at five sites within an Appalachian Mountain drainage basin. Two sites were on first order streams and differed from the three second order sites: they were smaller and more shallow and they were depressed in pH and chemical richness. Patterns of abundance of individual taxa, of higher taxonomic groups and of functional (feeding) groups differed according to whether abundance was measured as density, as standing biomass or as annual production. Standing biomass was chosen as the measure of macroinvertebrate abundance because available evidence indicates that only standing biomass is consistently, positively correlated with survivorship, and thus with habitat favourability. Two non‐insect taxa (the crayfish Cambarus and the snail Leptoxis carinata) dominated standing biomass at each site. Consequently, differences among sites in total macroinvertebrate standing biomass and differences within and among sites in standing biomass of functional groups were determined by differences in estimated standing biomass of these two taxa. Differences in estimates of crayfish standing biomass were consistent with an explanation based on the availability of refuges created by large substrate particles. The abundance of L. carinata appeared to be controlled primarily by water chemistry and possibly secondarily by predators. A number of insect taxa exhibited patterns of standing biomass consistent with hypotheses based on effects of annual depth‐flow regimes. Hypotheses based on differences in food resource and on competition appeared, in general, to be inconsistent with observed patterns of macroinvertebrate abundance. Contrary to predictions of the River Continuum Concept, the shredder functional group in the Guys Run drainage and in other temperate woodland streams was found to be a minor part of total macroinvertebrate standing biomass. Further, in a majority of small forested stream sites studied to date, standing biomass of grazers has been determined to be greater than that of shredders.

Emergence of blackflies (Diptera: Simuliidae) from a small forested stream in Ontario

Three species of blackflies were found in emergence-trap samples taken overa period of 8 months from a second-order, forested, cold-stenothermal stream in southern Ontario. The emergence phenologies of the two common species, Prosimulium mixtum and Stegopterna mutata, are described and compared with their phenologies in other streams in North America. Hypotheses are presented for the poor faunal diversity and prolonged emergence of the two species in the stream studied. Emergence data are used to describe the pupal distribution in the stream.