Within Southern Ontario urban development is rapidly devouring headwater systems, and this can have significant repercussions to the health of entire river networks. The ecological contributions of headwaters to downstream aquatic systems are poorly understood. The relationships between exported organic material (invertebrates, organic detritus) and land use were examined from 16 headwater systems (13 ephemeral channels, 3 intermittent channels) located in and around the Toronto Region. Drift traps, precipitation and crest stage gauges were installed at each location to capture exported materials, measure rainfall and estimate peak flow, respectively. Samples were collected during runoff events, snow melt or precipitation from March through November 2008. The amount of snow melt or precipitation necessary to trigger surface runoff was found to be highly dependent on land use and antecedent conditions. Invertebrates of aquatic and terrestrial origin were collected, with aquatic animals comprising 43% and 87% of the total from ephemeral and intermittent headwaters, respectively. The mean export of organic materials was 963 invertebrates per event (0.65 g) and 32.0 g of plant matter per event. The amount of materials transported was highly variable among samples (1 – 13,751 invertebrates per event). Within ephemeral channels, Annelida, Insecta and Chironomidae were the most numerous aquatic taxa (representing 40%, 24% and 23% of the total number of invertebrates transported per event, respectively), while Mollusca, Arachnida and Insecta were the most numerous terrestrial taxa (representing 35%, 21% and 16% of the total number of invertebrates transported per event, respectively). Earthworms contributed 64% of the total invertebrate volume collected per event. Chironomidae, Crustacea and Trichoptera were the most numerous aquatic taxa collected from intermittent channels (representing 55%, 27% and 8% of the total number of invertebrates transported per event, respectively), whereas Arachnida, Insecta, and Collembola were the most numerous terrestrial taxa (representing 52%, 19% and 13% of the total number of invertebrates transported per event, respectively). Trichoptera accounted for 59% of the total aquatic invertebrate volume collected per event. Preliminary results suggest that the ecological contributions of headwaters to downstream systems are considerable and their importance should not be overlooked.

Within Southern Ontario urban development is rapidly devouring headwater systems, and this can have significant repercussions to the health of entire river networks. The ecological contributions of headwaters to downstream aquatic systems are poorly understood. The relationships between exported organic material (invertebrates, organic detritus) and land use were examined from 16 headwater systems (13 ephemeral channels, 3 intermittent channels) located in and around the Toronto Region. Drift traps, precipitation and crest stage gauges were installed at each location to capture exported materials, measure rainfall and estimate peak flow, respectively. Samples were collected during runoff events, snow melt or precipitation from March through November 2008. The amount of snow melt or precipitation necessary to trigger surface runoff was found to be highly dependent on land use and antecedent conditions. Invertebrates of aquatic and terrestrial origin were collected, with aquatic animals comprising 43% and 87% of the total from ephemeral and intermittent headwaters, respectively. The mean export of organic materials was 963 invertebrates per event (0.65 g) and 32.0 g of plant matter per event. The amount of materials transported was highly variable among samples (1 – 13,751 invertebrates per event). Within ephemeral channels, Annelida, Insecta and Chironomidae were the most numerous aquatic taxa (representing 40%, 24% and 23% of the total number of invertebrates transported per event, respectively), while Mollusca, Arachnida and Insecta were the most numerous terrestrial taxa (representing 35%, 21% and 16% of the total number of invertebrates transported per event, respectively). Earthworms contributed 64% of the total invertebrate volume collected per event. Chironomidae, Crustacea and Trichoptera were the most numerous aquatic taxa collected from intermittent channels (representing 55%, 27% and 8% of the total number of invertebrates transported per event, respectively), whereas Arachnida, Insecta, and Collembola were the most numerous terrestrial taxa (representing 52%, 19% and 13% of the total number of invertebrates transported per event, respectively). Trichoptera accounted for 59% of the total aquatic invertebrate volume collected per event. Preliminary results suggest that the ecological contributions of headwaters to downstream systems are considerable and their importance should not be overlooked.

Tropical habitats have high taxonomic and ecological diversity, but they are currently subject to high rates of extinction. Amphibian populations are declining globally and while we have some understanding of the causes of these declines, it is unclear how these losses will influence ecosystem structure and function. Secondary production and trophic basis of production analyses link consumers to energy flow and reflect the relative importance of various energy sources and energy flow pathways in food webs. These techniques can yield valuable information on the roles of individual consumers in ecosystem function, and thus the ecological consequences of extinction and extirpation events. I estimated the trophic basis of production in a Panamanian headwater stream to identify major sources of energy, measure energy flow through consumers, and characterize interactions among trophic levels and functional feeding groups. I examined gut contents of 19 dominant macroinvertebrate and two dominant tadpole taxa collected during dry and wet seasons before an amphibian decline. I used previously published estimates of secondary production, assimilation efficiencies, and net production efficiencies, along with gut content data, to quantify food web structure and energy flow pathways. Overall consumption of allochthonous materials was greater than autochthonous (p < 0.001), and the dominant food sources were non-algal biofilm and vascular plant detritus. Autochthonous materials were consumed at higher rates during the dry season (p = 0.012). Total consumption rates varied within and among shredders (0.85 - 12.10 g/m2/yr), scrapers (0.46 - 0.91 g/m2/yr), filterers (1.20 - 4.67 g/m2/yr), gatherers (0.43 - 2.44 g/m2/yr) and predators (0.05 - 0.95 g/m2/yr). Overall consumption rates in pool habitats were higher compared to riffles. The degree of omnivory in the food web was much higher than has been observed in similar temperate streams. Omnivory was prevalent across all functional feeding groups, but more pronounced in predators, especially Anacroneuria (55% animal and 45% plant materials in guts). There was also an ontogenetic shift among most dominant macroinvertebrates from smaller, energy rich food sources (e.g., non-algal biofilm) to larger, less nutritious materials (e.g., vascular plant material) with increase in size. My research is the first to provide quantitative estimates of energy flow through a neotropical headwater stream food web. Information from this study is central to understanding and conserving tropical headwater streams. Further, my results, along with post-amphibian decline analyses from the same stream, will allow for a comprehensive assessment of the ecological consequences of amphibian declines.

Rapid field-based assessment methods for classifying stream permanence in headwater streams are needed to accurately inform regulatory decisions regarding which streams are protected under the Clean Water Act. In North Carolina, a rapid field-based assessment method for identification of intermittent and perennial streams has been developed. The North Carolina Method (NC method) uses 26 attributes divided into three categories geomorphology, hydrology, and biology to assess a particular study reach's flow permanence. In this method, the attribute scores for a given study reach are totaled and the sum of the score is used to rank the reach as ephemeral, intermittent, or perennial. The study objective were to (1) evaluate the NC method's ability to classify the flow permanence of agricultural, low order, study reaches in Southern Illinois and (2) create empirical models that predict flow permanence at a given stream location. The results of the study show the NC method successfully differentiated ephemeral from intermittent and perennial study reaches 100% of the time. However, there was lower fidelity in differentiating between intermittent and perennial study reaches and correctly determined flow permanence 82% of the time. In two of the cases where the NC method categorized the streams incorrectly, the score was on the threshold between intermittent and ephemeral. If these study reaches were categorized during a drier period they may have scored correctly. These results suggest the NC method would be a strong foundation for the development of a rapid field-based assessment protocol method for Illinois. Regression models were developed to predict NC method scores using a variety of hydrologic, geomorphic, and land-cover metrics. Two statistically significant models (>95% confidence interval) for estimating NC method stream permanence scores were developed using these physical parameters. One of the significant regression models developed used watershed area alone as a predictor of the NC method stream permanence scores. The second significant regression model employed bankfull width, upslope surface-water area, and upslope area of grass lands. These models explained 61% and 69% of the variance in the NC method stream-permanence scores, respectively. While the regression models develop here are not capable of explicitly modeling stream-permanence class with a high degree of accuracy, they are useful for guiding stream-permanence study-site selection.

Headwater streams drain the majority of the landscape, yet little is known about their form and function in comparison to lowland rivers. Better understanding of their morphology and sediment transport processes will improve understanding of landscape evolution and promote a more complete view of fluvial systems. Therefore, the goal of my project was to determine controls on headwater channel form and function in the humid, moderate-relief drainage basins of the Valley and Ridge and Blue Ridge provinces in the southern Appalachian Mountains. I surveyed nine headwater (0.33 - 2 km2 drainage area) streams in a variety of bedrock, climate, base level, and land use conditions and produced a high-resolution dataset on their longitudinal and cross sectional form. This data was analyzed empirically to determine controls on channel form, and used in hydrologic modeling to determine the ability of the channels to erode their beds during regularly recurring flows as well as the recurrence interval of bankfull flows. Field survey results demonstrate that the channels are dominantly alluvial and vary greatly between and within channels in their overall longitudinal form, channel slope values, and grain size. These variations are due to differences in bedrock resistance at the formation level as well as at short wavelengths. Bedrock also controls channel form through its influence on local and regional base level, channel initiation processes, and log jam abundance. Hydraulic geometry, steam competence and bankfull flow recurrence also vary greatly between and within channels. This variation is due to the high sensitivity of the streams to hillslope influences such as bedrock resistance, boulder influx, and soil profile development. Increases in bedrock resistance within a channel create knickpoints that lower stream competence and slow hilllslope erosion. Stream competence is generally higher in channels with erodable bedrock and lower in channels with resistant bedrock, but most channels could entrain the majority of the grains on their bed at 2-year stormflows. Bankfull is a larger, less frequent flow than the 2-year storm at very small drainage areas (<0.4 km2), but is approximately a 2-year recurrence flow at larger drainage areas. Bankfull occurs less frequently in North Carolina Blue Ridge streams, due to deep soils that form on metamorphic bedrock under an more intense precipitation regime and have high rainfall storage capacity. Results indicate that variability is a fundamental feature of headwater streams and that they do not follow channel slope, hydraulic geometry, and bankfull relations developed in lowland river systems. / Master of Science

Intermittent headwater streams serve important functions in semi-arid rangelands, both for humans and wildlife. However, few studies have assessed species-environment relationships for fish and benthic macroinvertebrate assemblages in these systems. Additionally, no published studies could be found that addressed the influence of juniper coverage in watersheds on assemblage structure of these taxa. Increased juniper coverage in recent decades is believed to be associated with decreased water yields in central Texas streams. During summer 2003 and spring 2004, I examined potential effects of juniper cover on aquatic ecology. Fishes, benthic macroinvertebrates, and the physicochemical habitat were investigated in spring-fed headwater tributaries of the Pedernales River. My objectives were to: 1) describe the typical fish and benthic macroinvertebrate assemblages in headwater creeks of the Pedernales River basin; 2) compare seasonal variability of fish and benthic macroinvertebrate assemblages; 3) identify species-environment relationships in this river basin; and 4) evaluate the influence of juniper coverage in the watershed, relative tolocal and landscape-level environmental factors, on the structure of fish and benthic macroinvertebrate assemblages. A total of 4,181 individual fish were collected in summer 2003 samples, 551 fish were collected in spring 2004, 59,555 macroinvertebrates were captured in summer 2003 samples, and 51,500 macroinvertebrates were collected in spring 2004. Assemblages were typical for the area and habitat conditions. Faunal richness was lower in spring than in summer, possibly due to a combination of sampling after a relatively dry period in the spring, and lack of winter refugia in the form of deep pools. Fish assemblages may structure based principally on abiotic factors in spring, the harsher season (less available water), whereas predation pressure may influence structure in summer. Another important environmental gradient for both fish and invertebrate assemblages contrasts pool and run mesohabitats. In general, juniper cover was weakly associated with fish and invertebrate assemblages, although it tended to be associated with relatively high quality habitat for sensitive taxa (flowing runs with coarse substrate; deep, connected pools). In these intermittent streams, local-scale environmental factors probably are the dominant influences on fish and benthic macroinvertebrate assemblages. Implications for future studies are discussed.

Forestry affects most of the forest-covered land in Sweden. In the landscape, the most common stream type is headwaters, which are important sites for many processes and organisms in both the terrestrial and the aquatic ecosystems. The aim of this study was to investigate how the abundance of benthic invertebrate functional feeding groups in headwater streams develops after clear-cutting and if it also is possible to detect a change in the composition of feeding groups. The study also attempts to determine what factors have an effect on temporal changes in abundance of these groups. For the study, 11 sites in northern Sweden were sampled for benthic invertebrates using a Surber-sampler, and for each site canopy-cover and pH was obtained. Further, the age of the surrounding forest at each was visually assessed and created a 100-year gradient along which temporal changes in abundance of the functional feeding groups were investigated. The results revealed that the total abundance of organisms was the highest short after clear-cutting and afterward decreased to the lowest level in streams with the highest age of surrounding forest. Significant results for the functional feeding groups were found for predators, shredders and scrapers, which also had the highest levels of abundance early after clear-cutting and thereafter decreased. The result shows that clear-cutting, not only changes the fundamental terrestrial conditions, but also has an impact on the abundance of different benthic functional feeding group.

Intermittent headwater streams serve important functions in semi-arid rangelands, both for humans and wildlife. However, few studies have assessed species-environment relationships for fish and benthic macroinvertebrate assemblages in these systems. Additionally, no published studies could be found that addressed the influence of juniper coverage in watersheds on assemblage structure of these taxa. Increased juniper coverage in recent decades is believed to be associated with decreased water yields in central Texas streams. During summer 2003 and spring 2004, I examined potential effects of juniper cover on aquatic ecology. Fishes, benthic macroinvertebrates, and the physicochemical habitat were investigated in spring-fed headwater tributaries of the Pedernales River. My objectives were to: 1) describe the typical fish and benthic macroinvertebrate assemblages in headwater creeks of the Pedernales River basin; 2) compare seasonal variability of fish and benthic macroinvertebrate assemblages; 3) identify species-environment relationships in this river basin; and 4) evaluate the influence of juniper coverage in the watershed, relative tolocal and landscape-level environmental factors, on the structure of fish and benthic macroinvertebrate assemblages. A total of 4,181 individual fish were collected in summer 2003 samples, 551 fish were collected in spring 2004, 59,555 macroinvertebrates were captured in summer 2003 samples, and 51,500 macroinvertebrates were collected in spring 2004. Assemblages were typical for the area and habitat conditions. Faunal richness was lower in spring than in summer, possibly due to a combination of sampling after a relatively dry period in the spring, and lack of winter refugia in the form of deep pools. Fish assemblages may structure based principally on abiotic factors in spring, the harsher season (less available water), whereas predation pressure may influence structure in summer. Another important environmental gradient for both fish and invertebrate assemblages contrasts pool and run mesohabitats. In general, juniper cover was weakly associated with fish and invertebrate assemblages, although it tended to be associated with relatively high quality habitat for sensitive taxa (flowing runs with coarse substrate; deep, connected pools). In these intermittent streams, local-scale environmental factors probably are the dominant influences on fish and benthic macroinvertebrate assemblages. Implications for future studies are discussed.

Headwater streams are considered to be the greatest contributor to nonpoint source and are a crucial part of overall watershed dynamics because they comprise more than 50-80% of stream networks and watershed land areas. This study addressed the influence of headwater areas (ephemeral and intermittent) on downstream hydrology and water quality following harvest as well as characteristics of vegetation communities within three first-order catchments in the Upper Gulf Coastal Plain of Mississippi. Four treatments representing a range of potential Best Management Practices (BMPs) for ephemeral drains were used: BMP1 - removal of all merchantable stems while leaving understory intact with minimum surface soil disturbance; BMP2 - same as BMP1 with the addition of logging debris to the drainage channel; No harvest - left uncut as a reference; Clearcut - total harvest with no BMPs applied. Harvested treatments caused the height of water table to increase up to 55 cm; however impacts of timber harvesting on peak discharge, storm discharge, and time of concentration were not consistent with water table response. Response time to stormflow was reduced significantly in harvested treatments (BMP2 and unrestricted harvest) as a result of decreased evapotranspiration and increased soil disturbance. Forest clearcutting in ephemeral drains caused intensive surface soil disturbance that resulted in substantial impacts to net soil erosion/deposition in both channel and hillslope positions and significantly increased total suspend sediment (TSS). There were no significant differences between two BMP and reference treatments in net soil erosion/deposition and TSS. Distinct vegetation communities between channel and hillslope positions in ephemeral-intermittent drains corresponded to water table gradients. Timber harvesting affected vegetation communities through direct and indirect disturbances. Four indicator species (V. blanda, L. glandulosa, A. gigantean, and P. acrostichoides) were identified as having a strong response to hydrologic gradients in ephemeral-intermittent drains.

No description available.