Hydrological pathways and episodic stream acidification were investigated by monitoring water quality in the Coalbum catchment during the later stage of canopy closure. Coalburn is a long-running experimental site, almost completely covered by a commercial coniferous plantation (part of the Kielder Forest in northern England). Regular sampling, event sampling and continuous monitoring were used to establish an extensive water quality data-base between 1993 and 1997. Cloud mist and precipitation at Coalburn are slightly acidic and the catchment can receive moderate levels of dry and wet acid deposition when the winds have tracked from an easterly direction. Coalburn streamwater chemistry displays well-buffered base-flows and acid episodes during high flows. Duration-frequency-magnitude analysis of the Coalburn acid episodes reveals they were less frequent than expected but had a longer duration. The acid events exceeded environment quality standards for freshwaters: pH and aluminium concentrations suggest a toxic impact on freshwater biota. However, the elevated calcium concentrations and presence of humic substances reduce the biological impact. The chemical signatures and variations in solutes were identified and used to postulate the causal mechanisms of the hydrochemical response and to produce the conceptual Coalburn runoff model. Mixing modelling was then applied to introduce a robust analysis into the process and produce the simplified Coalburn Model of acidification. Broadly, the Coalburn hydrochemical response can be explained by pre-event water sources and 'normal' catchment processes. However, during extreme events catchment conditioning and event-water can also influence the response. In improving knowledge of the likely water quality effects of coniferous plantation afforestation, the Coalburn study has contributed to calibrating the temporal and spatial variability of headwater acidification (and hence risks). This allows policy makers and environment managers to make informed decisions about land use/management and to apply the precautionary principle; the research findings were used to suggest a basic policy framework and protocols for catchment assessments to manage acidification issues through the cropping cycle within a headwater catchment.

Headwater watersheds initiate material export to downstream environments. A nested headwater study examined the flux and source of dissolved constituents and water from a perennial stream and four ephemeral/intermittent streams in the Upper Gulf Coastal Plain, Mississippi. Water was collected during storm and baseflow conditions. Multiple linear regression was used to model constituent concentration and calculate flux. Source of water was determined using principle components analysis and end-member mixing analysis. Rain was the major source of water discharged from the ephemeral and intermittent streams, while groundwater was the major source for water discharged by the perennial stream during events. Baseflow from both stream types was dominated by groundwater sources. The perennial stream had an area weighted average yields of 10.1, 0.01, 1.0, 0.6, and 0.03 kg-1 ha-1 yr-1 of DON, NO3--N, NH4+-N, PO4-3, and DOC,respectively. This research highlights the interaction of source water and dissolved constituent flux.

Headwaters, which are the most common stream order in the landscape, are mostly dependent on energy produced in the terrestrial system, largely consisting of leaf litter from riparian vegetation. The aim of this study was to investigate the decomposition in headwaters of leaf litter from three native (alder, birch, spruce) and one non-native (lodgepole pine) species and how decomposition responds to changes in the environment. Further, microbial and shredder influences on leaf-litter decomposition and aquatic decomposer ability to adapt to non-native species was investigated. By using field-data from this study, calculations were made to assess if microbes and shredders are resource limited. Litterbags were placed in 20 headwater streams in northern Sweden that varied in water chemistry, stream physical characteristics and riparian vegetation. The results revealed that species litter decomposition of different plant species was affected differently by changes in environmental variables. Alder and birch decomposition were positively associated, whereas lodgepole pine deviated from the other species in decomposition and its relationship with important environmental variables, indicating that the ability of the boreal aquatic systems to decompose litter differs between introduced and native species. When including macroinvertebrates, shredder fragmentation generally increased decomposition, but was not significant for all sites. Resource availability for microbes and shredders was controlled by litter input, and no risk of resource limitations was evident during the study period. These findings highlight a complexity of the decomposition process that needs to be considered when predicting changes due to human activities.

Ephemeral streams are small headwater streams that only experience streamflow in response to a precipitation event. Due to their highly complex and dynamic spatial and temporal nature, ephemeral streams have been difficult to monitor and are in general poorly understood. This research implemented an extensive network of recently developed electrical resistance sensors to monitor ephemeral streamflow in a Southern Ontario watershed, located in Guelph, Ontario. From this data, patterns of stream network expansion and contraction were determined. Further analysis examined a series of spatial and temporal variables that were monitored to explain the occurrence of ephemeral channel activity through binary logistic regression. The results suggest that the most common patterns of network expansion and contraction at the study site are incomplete coalescence and disintegration, respectively. Analysis of the primary controls on ephemeral streamflow showed only weak relationships, suggesting that there are more complex processes at work in these ephemeral streams. This research has implications for improving ephemeral streamflow monitoring in the future, which will be important for developing and implementing meaningful conservation and management strategies.

The thesis explores various aspects of ecology of endangered damselfly Coenagrion ornatum, the specialists for lowland headwaters, in post-mining streams of Radovesicka spoil. The first part of thesis is manuscript which has been already submitted in Journal of Insect Conservation. In the first part, we focused on population estimate of the local population using capture-recapture method, and explored its habitat requirements across life stages and spatial scales. In the next part, I assess mobility of the focal species and reveals basic distribution patterns. Finally, the thesis suggest various implications for restoration of post-mining freshwaters and conservation of the studied species.

The headwaters of the Bear River in the Uinta Mountains of Utah provide a good setting in which to examine the influence of geological materials on stream chemistry. Ionic contributions to the stream-water from soils, vegetation, and the atmosphere generally are sparse enough that they do not mask the geologic contributions. Samples from 37 sites on the four major headwater streams and several minor tributaries were examined geochemically. Data derived from the samples allowed the construction of a hydrogeochemical weathering model specific to the study area. A significant feature of this model is that carbonic acid is the dominant chemical agent involved in geochemical weathering. The aim of this study was to examine the geologic influences on river chemistry. However, atmospheric contributions dominate the hydrochemistry through at least the first 10 kilometers of stream length for the easternmost three of the four major headwater streams. Except for the atmospheric contribution, surface-water chemistry is dominated by the groundwater chemistry, which is indelibly marked by the lithology the groundwater passes through. Other geologic factors in the study area that appear to influence groundwater chemistry, and hence stream chemistry, are the glacial till and outwash deposits and a major zone of east-west trending high-angle thrust faults. A technique for estimating the hydrochemistry of the groundwater based on surface-water chemistry and flow measurements was developed in this study.

Many ecosystems are losing biodiversity, raising concern for the services they provide. However, the extent of loss is uncertain, especially for insects that use freshwater during their life. Further study is needed to assess freshwater insect abundances and diversity. In Central Appalachian streams, macroinvertebrate diversity declines in response to mining-induced salinization and resulting changes to ecosystem processes remain largely unknown, such as how the availability and movement of macroinvertebrate biomass is altered in stream food webs. However, taxa observed are dependent upon sampling effort that could bias diversity-process interpretation. Taxon sampling curves can be used to estimate sampling effort that maximizes the probability of complete community characterization. We sampled six streams in the Central Appalachian region for benthic macroinvertebrates and explored the number of samples needed to capture taxonomic richness in salinized streams. Sampling effort did not differ between reference and salinized streams, though more uneven distributions of macroinvertebrates in salinized streams seemed to necessitate greater sampling effort relative to reference streams. We also used taxon and trait-based sampling curves to expand our understanding of biodiversity and functional responses to environmental change. Because macroinvertebrate biomass and emergence can assess the movement and changes in organic material and energy in response to a salinization gradient, we added them as additional metrics. Macroinvertebrates may have varied responses to a stressor dependent upon life stage, suggesting that assessments relying only on immatures may not fully characterize the effects of salinization. We sampled benthic macroinvertebrate biomass and emergent insect biomass from six streams in the Central Appalachian region to be representative of a salinization gradient. We predicted benthic biomass would either decrease, be maintained by greater density and biomass of salt-tolerant taxa, or increase from a salt subsidy effect, while emergent biomass would decrease disproportionately relative to benthic biomass due to late instar and pupae succumbing to stress. Our results suggest that total benthic macroinvertebrate biomass is maintained along a salinization gradient despite the loss of salt-sensitive mayflies due to compensation by salt-tolerant taxa that experience a subsidizing effect. Emergent biomass was variable among streams with peak emergence occurring in spring, with no apparent negative response to increasing conductivity. The present study can help to further develop metrics of stream ecosystem processes in response to a disturbance gradient. / Master of Science in Life Sciences / Freshwater salinization is a growing, global concern. Pollution and accelerated weathering of rock, caused by human activities, introduce salts to streams and other freshwaters. Surface coal mining is a common land use in the Central Appalachian region and increases leaching of sulfate and other major ions that increase stream salinity, leading to losses of aquatic insect species. Aquatic insects are important to stream processes, such as providing food to other animals, and they can serve as the bioassessments when impacts are suspected. For example, the impacts of salinization on streams are not fully understood despite bioassessments. We sampled aquatic insects from six Appalachian streams with varying levels of salinity. We estimated the sampling effort needed to characterize aquatic larval insect communities in streams with low salinity compared to streams with high salinity. We found that about six samples captured 80 percent of estimated total taxa and that insect communities with greater unevenness required more sampling effort. Such comparisons will allow us to make more informed decisions when sampling aquatic insects and assessing the effects of salts on streams. We also estimated insect biomass in streams using two life stages, larvae and adults, to determine if these life stages would respond differently to salinization. As we expected, total larval biomass slightly increased as the concentration of salt increased, but mayfly biomass decreased. Mayflies are an important and diverse group of insects in Appalachian streams and decreases in their biomass can have consequences for insect communities and stream food webs. Even though emergent insect biomass was found to represent only a small proportion of the larval biomass observed in streams, they represent critical food for terrestrial animals. Estimates of benthic and emergent biomass could be considered to refine bioassessments that support future management and policy regarding surface mining and the rising issue of freshwater salinization.

Aquatic ecosystems play a substantial role in global cycling of carbon (C), despite covering only about 4% of the earth surface. They emit large amounts of greenhouse gases (GHG) to the atmosphere, comparable to the amount of C stored annually in terrestrial ecosystems. In addition, C can be buried in lake sediments. Headwater systems are located at the interface of the terrestrial and aquatic environment, and are first in line to process terrestrial C and throughout its journey through the aquatic continuum. The uncertainties in global estimates of aquatic GHG emissions are largely related to these headwater systems, as they are highly variable in time and space, and underrepresented in global assessments. The overall aim of this thesis was therefore to study GHG exchange between sediment, water and air in headwater systems, from both an ecosystem perspective and at the small scale of physical drivers of gas exchange. This thesis demonstrates that carbon dioxide (CO2) emission from headwater systems, especially streams, was the main pathway of C loss from surface waters from a lake catchment. Of the total aquatic CO2-emission of the catchment, 65% originated from stream systems that covered only 0.1% of the total catchment area. The gas transfer velocity (k) was the main driver of stream CO2-emission, but there was a high variability in k on small spatial scales (meters). This variability may have implications for upscaling GHG emissions, especially when using scaled k estimates. Lake sediments only contributed 16% to total lake C emission, but in reality, sediment C emission is probably even lower because experimentally determined sediment C flux returns high estimates that are biased since artificially induced turbulence enhances C flux rates beyond in-situ conditions. When sediment C flux is estimated in-situ, in natural bottom water turbulence conditions, flux rates were lower than those estimated experimentally. Conclusively, this thesis shows that GHG emissions from small aquatic ecosystems are dominant over other aquatic C fluxes and that our current knowledge regarding the physical processes controlling gas exchange from different small aquatic systems is limited, implying an inherent uncertainty of GHG emission estimates from small aquatic ecosystems.

Forest management practices usually preserves riparian buffers along watercourses in order to protect stream water from physical, chemical and ecological changes caused by clear-cutting. The purpose of this thesis was to investigate whether there is a relationship between the size of the riparian buffer zone along small streams, i.e., headwaters, and a number of physical and chemical attributes of these streams. Twelve headwaters in the Västerbotten county and twelve in Jönköpings county were investigated. These headwaters had a range of buffer widths from “No buffer” (no trees left), Thin buffer” (< 5 m wide), to “Moderate buffer” (>5 m wide) and “Reference” (no harvest) streams were also included. Tested physical and chemical conditions were light in the riparian zone, air and water temperature, stream bed cover and water chemistry. Buffer width had a significant effect on reducing light levels and temperature in the riparian zone; a buffer width over 13 m on each side of the stream was needed to maintain light and air temperature as in reference conditions. Regarding water temperature, increasing sedimentation and water quality, no significant reducing effect of increasing riparian buffer width was found.

This study investigates the effects of forestry on leaf litter decomposition in small forest streams. Riparian forest, that is the land closest to the stream, maintain shading, water temperature and energy supply through litter fall. If the riparian zone is deforested, many riparian functions important for the integrity of the stream ecology, hydrology and biogeochemistry can be lost or modified. Leaf litter decomposition can be used as an integrated measure of the physical and biological changes following forestry perturbations.  This study was conducted in 11 northern and 12 southern Swedish streams to address; 1) How is leaf litter decomposition in small streams affected by forestry by measuring leaf litter decomposition in streams with different buffer widths, and; 2) How other environmental variables, such as  stream bottom substrate, canopy openness, water temperature and stream velocity affected leaf litter decomposition. Buffer width had no effect on decomposition. Temperature and proportion organic bottom substrate had respectively positive and negative trends with decomposition in the southern Swedish sites which suggests the importance of forestry targeting these riparian functions especially when managing small streams. At the northern sites, velocity showed a positive, and temperature a negative trend with leaf litter decomposition but none of these were significant. It is possible that the extraordinarily warm and dry weather before and during the study was conducted affected aquatic organisms to the degree that decomposition was inhibited, and most trends became too small to detect or that buffer width is less important in a warmer climate.