VTechWorks Repository :: Browsing by Author "Dolloff, C. Andrew"

Browsing by Author "Dolloff, C. Andrew"

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American Eel Distibution and Growth in Selected Tributaries of the James River
Strickland, Patrick Andrew (Virginia Tech, 2002-08-16)
In July of 1999, a team of researchers from the Virginia Department of Game and Inland Fisheries (VDGIF) and the United States Forest Service (USFS) electrofished a 2-km reach of Shoe Creek, Virginia, and captured 66 American eels. Eels were weighed (g) and measured (mm) and 61 individuals were implanted with Passive Integrated Transponders (PIT). Size distribution of the tagged eels ranged from 174-775 mm total length. The team returned to Shoe Creek in October of 1999 for a recapture survey, but captured only seven eels in the same 2-km reach with no recaptures. This sparked considerable interest among the biologists of VDGIF and USFS. Goals of the biologists included identifying daily movement, seasonal distribution, relative abundance, habitat use, and growth of American eels in Virginia headwater streams. This information was needed for the protection of eel habitat and migration corridors, as well as development of restoration plans for eels. Seasonal movement of thirty-three American eels Anguilla rostrata was monitored from July 2000 through September 2001 via radio telemetry. South Fork Piney River, South Fork Tye River, and Shoe Creek, Virginia were the streams chosen for eel research. Eels exhibited the greatest amount of movement in summer 2000 and the least amount of movement in winter 2000-01. Diel activity was significantly lowest in winter 2000-01 and highest in spring 2001. From late October 2000 through May 2001, eels appeared to be buried within the interstitial spaces of the stream bottom and under stream banks. Habitat preference (average depth, dominant substrate, and pool vs. riffle) was also determined over multiple seasons via radio telemetry. When a preference was detected, eels always preferred pools and the deepest water available relative to each stream. Eels preferred cobble as the dominant substrate during all seasons in S.F. Tye River. Eels showed no preference for substrate in S.F. Piney River. Substrate preference varied among seasons in Shoe Creek. Estimates of 12, 41, and 25 eels/ha were calculated for S.F. Piney River, S.F. Tye River, and Shoe Creek, respectively, in summer 2000. There was a significantly higher density of eels in S.F. Tye River when compared to S.F. Piney River in summer 2000. Estimates of 7, 54, and 15 eels/ha were calculated for S.F. Piney River, S.F. Tye River, and Shoe Creek, respectively, in summer 2001. There was a significantly higher density of eels in S.F. Tye River when compared to both S.F. Piney River and Shoe Creek in summer 2001. Growth in total length (TL) was determined in S.F. Piney River, S.F. Tye River, and Shoe Creek from summer 2000 to summer 2001. Growth in TL for S.F. Piney River, S.F. Tye River, and Shoe Creek was 18, 23, and 21 mm/year, respectively. Growth in TL for Shoe Creek was also calculated from 1999-2000 (43 mm/year) and 1999-2001 (32 mm/year). There was a significant difference in growth between Shoe Creek 1999-2000 and Shoe Creek 2000-01 as well as Shoe Creek 1999-2000 and S.F. Tye River 2000-01. Growth in weight was also determined in S.F. Piney River, S.F. Tye River, and Shoe Creek from summer 2000 to summer 2001. Growth in weight for S.F. Piney River, S.F. Tye River, and Shoe Creek was 24, 21, and 27 g/year, respectively. Growth in weight for Shoe Creek was also calculated from 1999-2000 (50 g/year) and 1999-2001 (40 g/year). There was a significant difference in growth between Shoe Creek 1999-2000 and Shoe Creek 2000-01 as well as Shoe Creek 1999-2000 and S.F. Tye River 2000-01. Our results have contributed to knowledge of the biology and ecology of the American eel in the upper James River drainage, including diel activity, seasonal movements, habitat use, densities, and growth. Eels were more active during spring and summer, particularly at night. They demonstrated very little movement throughout the other seasons of the year. The majority of eels displayed a behavior similar to hibernation, burying in the substrate and under the banks of the stream from mid-fall through mid-spring. Eels showed a trend to use deep pools with large substrate throughout the majority of this study. Eel densities seemed to vary among streams, with higher growth in streams with lower eel densities and a higher average water temperature.
American Eel Subpopulation Characteristics in the Potomac River Drainage, Virginia
Goodwin, Kevin R. (Virginia Tech, 1999-06-23)
The demographic characteristics of American eels (Anguilla rostrata) are believed to vary with latitude and distance inland from the ocean; eels are generally thought to increase in length, age, and the proportion of females in inland and more northerly areas. Understanding this variation is necessary for the sound management of eels, but investigations into characteristics on a broad scale within drainages are scarce. Eels in the Potomac River drainage, Virginia, were sampled over a two-year period in both near-coastal and inland areas to describe characteristics in each area as well as to understand drainage-wide patterns. Inland data resulted from sampling in the Shenandoah River drainage and near-coastal data resulted from sampling tributaries to the lower Potomac River. Movement and growth were also investigated in inland areas. Eels from the Shenandoah River drainage were significantly longer (median = 763 mm TL) and older (median = 11.5) than those found in the Potomac River tributary sites (median = 142 mm TL; median = 2.0, respectively). Both total length and age increased with increasing distance inland and sex ratio shifted from varying ratios of males:females in Potomac River tributaries to all females in the Shenandoah River drainage. Movements confirmed through mark-recapture over periods ranging up to one year were short, generally <100 m, with the longest detected movement being 1.5 km. Recapture rates were low and may be due either to low sampling efficiency, long-distance movements, or a combination of these factors. Growth and 95% confidence interval from five eels recaptured after approximately one year was 43.0 +/- 29.7 mm/year. CPUE decreased with increasing distance inland, confirming information reported by others for Virginia streams.
Amphibian Population and Community Characteristics, Habitat Relationships, and First-Year Responses to Clearcutting in a Central Appalachian Industrial Forest
Williams, Lori Ann (Virginia Tech, 2003-05-08)
The overall goal of this project was to provide baseline data on amphibian species richness, relative abundance, and habitat use for a long-term landscape ecology study on MeadWestvaco industrial forest in the Allegheny Highlands of West Virginia. From results of area-constrained daytime searches (10 m x 10 m plots) across the landscape, I developed 9 regression models to predict amphibian relative abundance. I constructed models for each year for all plots on all habitat types, plots that were in a Stream Management Zone (SMZ), and plots that were in upland, or non-SMZ, habitat. Distance to perennial or ephemeral streams or perennial ponds (SMZ classification), the amount of available rocks along transects, and site index were the 3 most important habitat variables in models for all plots combined and were responsible for 24-32% of the inherent variation in population relative abundance. Other habitat variables that were significant in models were year, % canopy cover, the amount of available woody debris of decomposition classes 3-5 along transects, % woody stems (<7.5 cm DBH), soil pH, and % herbaceous vegetation. R2PRESS values for all 9 models ranged from 0.08 to 0.35. Amphibian relative abundance showed positive relationships with all significant habitat variables with the exception of year and % woody stems. In natural cover object use/availability analyses, I discovered salamanders preferred rocks over woody debris, relative to the amount available of each. Salamanders preferred flat rocks to any other shape, flagstones to any other type of rock, and rock lengths in the 31-40 cm class. Preferred wood widths were in class 5-10 cm, while preferred wood lengths were in class <50 cm; salamanders exhibited strong preferences for wood in higher states of decomposition (class 3-5). I provided baseline, preharvest data for 28-acre reference areas on 9 forest compartments scheduled for clearcuts. I sampled all 9 reference areas preharvest and sampled 3 during year 1 postharvest using coverboard and night plot surveys. On these 3 areas, species richness declined from preharvest to postharvest, but species diversity showed little change. Overall relative abundance declined significantly preharvest to postharvest with coverboard sampling (p=0.0172) and night plot sampling (p=0.0113). At coverboard stations, relative abundance declined significantly from preharvest to postharvest at a distance of 5-10 m (p=0.0163) and 40-50 m (p=0.0193) away from adjacent mature forest. Finally, using Pianka's index, I compared the night plot and coverboard sampling techniques in terms of proportions of the 4 most common species captured. These sampling techniques on average were >80% similar for all reference areas.
An Analysis of the Ecology and Public Perception of Coarse Woody Debris in Virginia
Fuhrman, Nicholas E. (Virginia Tech, 2004-07-07)
Coarse woody debris (CWD) is an important habitat component for wildlife, fish, and plants and is important in nutrient cycling and soil formation. Knowledge of the volume, distribution, and use of CWD across Virginia would be useful to forest managers modeling nutrient budgets in southeastern forests and is important to wildlife management efforts. Knowledge of the effectiveness of informational brochures and cooperative learning activities/presentations at influencing public perception of CWD is important to program design and evaluation efforts in teaching and extension. The objectives of this study were to quantify the relationship between forest cover type and CWD volume, correlate CWD volume with small mammal and bird activity, distribute information on the advantages and disadvantages of CWD using informational brochures and cooperative learning activities/presentations, and compare the effectiveness of such teaching techniques at influencing public perception of CWD. The volume and wildlife use of CWD was assessed within 12 mature second-growth stands in Virginia. Volume of CWD was measured using fixed-area plots. Use of CWD by small mammals and birds was assessed by noting bodily, foraging, or movement evidence. Pre- and post-survey instruments were used to evaluate how perceptions were altered in first year college students who either reviewed an informational brochure or participated in a cooperative learning activity/presentation. Results suggested that the management of CWD for wildlife was most needed in southeastern Virginia where CWD volumes were lowest and that the value of CWD for wildlife was best conveyed through cooperative learning activities/presentations and may be important to landowner education efforts. Results suggested that management efforts to increase CWD volumes in Virginia should focus on coniferous dominated stands where CWD volumes were lowest. Such a finding, combined with the knowledge that the value of CWD was best conveyed through presentations, suggests that landowners of coniferous woodlots could be effectively educated with presentations. Given that brochures were more effective for females than males, brochures addressing natural resource issues might be the most appropriate, cost effective method of education at events that target female audiences. Knowledge gained from this study that CWD management for wildlife would be most appropriate in western Virginia where CWD was most used by wildlife for travel and that presentations were most effective at reaching suburban participants may be important to outreach program design efforts. Regardless of academic major, presentations were more effective at generating positive attitudes toward CWD. The results of this study suggest that the choice between informational brochures and presentations for influencing public perceptions of CWD will likely be influenced by the demographics of the target audience and the relevance of the topic locally.
Applying ecological models to positive interactions among lotic fishes: implications for population and community regulation at multiple spatial scales
Peoples, Brandon Kevin (Virginia Tech, 2015-05-06)
Positive biotic interactions such as mutualism, commensalism and facilitation are ubiquitous in nature, but historically have received considerably less research attention than negative interactions such as competition, predation and parasitism. The paucity of research on positive interactions is particularly evident in stream ecosystems and in vertebrate communities. Stream fishes clearly provide an ideal system for advancing research on positive interactions. Many minnows (Cyprinidae) of eastern North America engage in a potentially mutualistic reproductive interaction known as nest association, in which individuals of one species (nest associates) spawn in nests constructed by host species. In nest association, hosts provide unsilted gravel substrate for spawning nest associates, and increased parental care to associate broods. High associate: host egg ratios can create a dilution effect, reducing the probability that host eggs will be preyed upon by egg predators. Nest associative interactions are common, but are relatively understudied compared to other interactions among stream fishes. The goals of this study were to apply general ecological models to this novel system to (a) gain new insight into the mechanisms structuring nest associative stream fish communities, and (b) to use inference from stream fish communities to potentially expand and improve the general ecological models. These goals required completion of three objectives, including (1) examining the influence of abiotic and biotic contexts on reproductive behavior and fitness outcomes between a cyprinid host and associate, using the biological markets model to generate predictions; (2) examining the utility of the nest web framework (previously only used for cavity nesting vertebrate communities) and the stress gradient hypothesis (previously applied almost exclusively to plant communities) for predicting which associate species spawn on nests built by various nest building species, and the consequences of these choices, respectively; and (3) using two-species occupancy modeling to determine the relative influence of biotic interactions and habitat covariates on the co-occurrence of a host and two nest associates. To accomplish these goals, I conducted a large-scale experiment to manipulate presence of mutualists (Nocomis leptocephalus, host; Chrosomus oreas, associate), egg predators (biotic context) and habitat quality (abiotic context). I conducted behavioral nest observations and conducted repeated stream fish stream fish community surveys to collect demographic data. I constructed a nest web from observational data, and implemented structural equation modeling through an information-theoretic framework to identify nest web plausibility across a large spatial extent. I tested some predictions of the stress gradient hypothesis by regressing juveniles-per-nest and a metric of cyprinid community structure on a composite measure of physical stress (scaled gradients of catchment-scale agricultural land use and catchment area). I used two-species occupancy modeling to model co-occurrence of N. leptocephalus hosts and two associates, C. oreas and Clinostomus funduloides, and used an information-theoretic framework to compare hypotheses representing the importance of biotic interactions, habitat covariates or both at determining species co-occurrence. Results corroborated some (but not all) model predictions, and identified room for improvement in each of the general models. Nest associative spawning by C. oreas was not context dependent; C. oreas did not spawn in the absence of a reproductively active male N. leptocephalus at any treatment level. However, the net fitness outcome of host and associate species was mutualistic, and the interaction outcome switched from commensalistic to mutualistic with abiotic context. N. leptocephalus reproductive success was improved by C. oreas presence in less-silted habitats, but not in heavily-silted habitats. This is most likely because broods were subject to predation in both habitat types, but were also negatively affected by siltation in silted habitats. Accordingly, egg dilution by associates was not sufficient to support a mutualistic relationship in less favorable habitats. Results suggest that the biological markets model may be a useful tool for predicting fitness outcomes of nest associative mutualism, but may not be as useful for predicting the behavioral outcomes of obligate mutualisms. Future applications of the biological markets model should carefully consider species traits, specifically the degree to which trading behavior is obligate for participants. Future work with this model will yield more insight by considering highly facultative associates. Nest webs constructed from nest observational data suggested an interaction topology in which strong (nearly-obligate) associates relied most frequently on N. leptocephalus nests, and less frequently on nests constructed by Campostoma anomalum. Weak (facultative) associates were seldom associated with nests constructed by either species, and probably spawned before hosts began nesting activity. Structural equation models corroborated this topology throughout the New River basin, although some less-supported model evidence specified some nest association by weak associates. Juveniles-per-nest of strong associates responded positively to physical stress, while this metric for other cyprinid reproductive groups showed no relationship. Proportional representation of Nocomis and strong associates also increased predictably with physical stress. This study suggests that the nest web framework can be informative to systems outside the ones for which it was developed; future studies may be able to use this framework to better understand the role of habitat-modifying species in communities other than cavity nesting terrestrial vertebrates and nest associative stream fishes. This work extended the nest web framework by (a) modeling the outcomes of interactions instead of the interactions themselves, and (b) by using structural equation modeling to test nest web predictions with an information-theoretic framework. This study also suggests that the stress gradient hypothesis can be useful for understanding interaction dynamics in vertebrate communities; this represents the first direct evidence that this model can be used in vertebrate communities. Further, I demonstrate that the stress gradient hypothesis may be extended to predict community structure. However, more research in a diversity of systems will be needed to determine the extent to which this can be applied. This study provides some of the first evidence of large-scale positive co-occurrence patterns in vertebrates. However, the precise roles of habitat covariates and biotic interactions were species-specific. Occupancy results suggest that co-occurrence between N. leptocephalus and nest associate C. funduloides is driven only by reproductive behavioral interactions. Alternatively, evidence suggests that co-occurrence between N. leptocephalus and C. oreas is driven by both nest association and habitat covariates. That two-species occupancy modeling can be a useful tool for comparing difficult-to-test hypotheses involving biotic interactions at large spatial scales. This study represents the first quantitative, multi-scale treatment of positive interactions in stream ecosystems. This study demonstrates that applying general ecological models to stream fish communities can yield new insights about both the study system and the models themselves. While models of negative interactions, food webs and dispersal have been applied to stream fishes, we stand to gain much ground by also considering positive biotic interactions. In doing so, stream fish ecologists will also be able to contribute to the advancement of general ecology, and thus raise awareness for these understudied ecosystems and taxa.
An assessment of the transferability of habitat suitability criteria for smallmouth bass, Micropterus dolomieu
Groshens, Thomas P. (Virginia Tech, 1993-01-05)
The purpose of this study was to determine if habitat suitability criteria developed in the summer months for sma11mouth bass were transferable among streams representing different eco regions. Habitat suitability criteria were developed for depth, mean column velocity, cover and substrate for two size classes of sma1lmouth bass, 100-199mm and >200mm, in the North Anna River and Craig Creek, Virginia. Criteria that accurately describe habitat selection by a species or guild in a system different from where the criteria were developed are said to be transferable to that system. The transferability of suitability criteria between the North Anna River and Craig Creek, as well as depth and velocity criteria from Minnesota, the Huron River, Michigan and the Upper James River, Virginia, to the North Anna River and Craig Creek were tested using a 2x2 contingency table analysis. Depth criteria for the smaller sizes of sma1lmouth bass did not transfer well between regions; 4 of the 8 transferability tests (50%) failed. Depth criteria for larger sma1lmouth bass transferred to the North Anna River and Craig Creek in all cases. Velocity criteria developed for the smaller size classes did not transfer well among regions; only 3 of the 8 transferability tests were positive. Likewise, velocity criteria for larger sizes of smallmouth bass did not transfer well; only 1 of 8 tests were positive. General criteria were developed for depth and mean column velocity by averaging the suitability values reported from this and 3 other studies. General depth and velocity criteria transferred well to the North Anna River and Craig Creek for both the larger and smaller size classes of smallmouth bass; all depth tests were positive and 3 of 4 velocity tests were positive. The improved success of transferability warrants investigation of developing general criteria for smallmouth bass. Cover criteria for both size classes of smallmouth bass were transferable from the North Anna River to Craig Creek but not vice versa. Substrate heterogeneity criteria were not transferable between the North Anna River and Craig Creek for either size class of smallmouth bass. Criteria developed for the percentage of substrate particles >15cm (smallmouth bass >200mm only) were transferable from Craig Creek to the North Anna River but not vice versa. The transferability of habitat suitability criteria among regions was inconsistent and it is recommended that site-specific criteria be developed for each stream to which habitat assessments are applied. Additionally, nose velocities used were more consistent between the North Anna River and Craig Creek than were mean column velocities used. Hence, it is recommended that information on nose (focal point) velocities be incorporated into habitat studies to more accurately describe smallmouth bass velocity requirements.
Bivariate functional data clustering: grouping streams based on a varying coefficient model of the stream water and air temperature relationship
Li, H.; Deng, Xinwei; Dolloff, C. Andrew; Smith, Eric P. (2016-02)
A novel clustering method for bivariate functional data is proposed to group streams based on their water-air temperature relationship. A distance measure is developed for bivariate curves by using a time-varying coefficient model and a weighting scheme. This distance is also adjusted by spatial correlation of streams via the variogram. Therefore, the proposed distance not only measures the difference among the streams with respect to their water-air temperature relationship but also accounts for spatial correlation among the streams. The proposed clustering method is applied to 62 streams in Southeast US that have paired air-water temperature measured over a ten-month period. The results show that streams in the same cluster reflect common characteristics such as solar radiation, percent forest and elevation. Copyright (C) 2015 John Wiley & Sons, Ltd
Boundary Shear Stress Along Vegetated Streambanks
Hopkinson, Leslie (Virginia Tech, 2009-10-20)
This research is intended to determine the role of riparian vegetation in stream morphology. This experiment examined the effects of riparian vegetation on boundary shear stress (BSS) by completing the following objectives: (1) evaluating the effects of streambank vegetation on near-bank velocity and turbulence; (2) determining a method for measuring BSS; and, (3) examining the effects of streambank vegetation on BSS using an existing model. A second order prototype stream, with individual reaches dominated by the three vegetation types (trees, shrubs, and grass) was modeled using a fixed-bed Froude-scale modeling technique. One model streambank of the prototype stream was constructed for each vegetation type in addition to one bank with only grain roughness. Velocity profiles were measured using an acoustic Doppler velocimeter (ADV) and a miniature propeller (MP). A flush-mounted Dantec MiniCTA system was used to measure shear stress at the streambank wall. The addition of vegetation on a sloping streambank increased the streamwise free stream velocity and decreased the near-bank streamwise velocity. The turbulence caused by the upright shrub treatment increased turbulent kinetic energy and Reynolds stresses near the streambank toe, an area susceptible to fluvial erosion. The presence of dense, semi-rigid vegetation may encourage the formation of a wider channel with a vertical streambank. The small range of CTA shear stress measurements (0.02—2.14 Pa) suggested that one estimate can describe a streambank. The law of the wall technique is not appropriate because the velocity profiles did not follow the necessary logarithmic shape. Vegetative roughness present in channels created secondary flow; turbulence characteristics more appropriately estimated BSS. The BSS model predicted velocity fields in similar distribution to that measured by the ADV and MP. BSS calculated using the ray-isovel method for both velocity measurement devices were different than the measured BSS values, likely due to distortions in the measured velocity field. In general, the predicted BSS distribution increased with water depth and decreased with increasing vegetation density. The predicted BSS at the shrub toe indicated a spike in shear stress consistent with TKE estimates.
Brook Trout Population Genetic Tools for Natural Barriers in Fragmented Subwatersheds
Timm, Anne Louise (Virginia Tech, 2010-09-08)
Barriers to fish movement can cause aquatic habitat fragmentation by reducing the amount of available habitat. The primary goal of my research was to investigate applications of population genetic analysis tools as indicators of barrier effects on brook trout populations in fragmented subwatersheds. In chapter1, I tested the hypothesis that brook trout population genetic differentiation (FST) above and below barriers will differ in relation to barrier height and gradient. I also tested the hypothesis that average gene diversity per locus (H) and the numbers of alleles (A) differed between samples below and above each barrier. There was no significant difference in average number of alleles (A) or average gene diversity per locus (H) between the above- and below-barrier samples, but linear regression identified a statistically significant relationship between barrier height and FST values. Unrooted neighbor-joining consensus trees of Cavalli-Sforza and Edwards (1967) chord distances provided evidence of genetic differentiation between samples of resident brook trout above and below natural barriers. Additionally, average total allelic diversity (A), average gene diversity per locus (H), average number of private alleles per locus per sample, and total alleles per sample differed between Level III Ecoregions. In chapter 2 I tested the hypothesis that the presence of a barrier, total habitat potentially isolated above a barrier (km), road density, and percent forest cover within a subwatershed (USGS 6th-level Hydrologic Units) were significant habitat fragmentation factors affecting the effective population size (Ne) of brook trout in the Blue Ridge Level III Ecoregion. Multivariable linear regression indicated that total habitat above the barrier (km) and road density were significant variables retained in the model to predict Ne. In chapter 3, the objective of the study was to infer relationships between barriers and family structure in brook trout populations. Maximum likelihood analysis of pairwise kinship relationships between above- and below-barrier individuals indicated the presence of parent-offspring relationships between above- and below-barrier individuals at six sites in the Blue Ridge Level III Ecoregion and five sites in the Northern Lakes and Forests Level III Ecoregion, which indicated movement of individuals between the above- and below-barrier locations.
Carbon Pools and Fluxes as an Indicator of Riparian Restoration
Giese, Laura (Virginia Tech, 2001-01-12)
Riparian forests are integral components of the landscape. The inherent biogeochemical processes that occur in such forests provide numerous benefits to wildlife and society. Maintaining good water quality is a major benefit from riparian forests and therefore, the maintenance, creation, or restoration of riparian forests is indispensable. This study was designed to broaden current knowledge of the complex, interrelated biogeochemical processes and determine indices for riparian forest restoration based on the various carbon pools/fluxes that may represent restoration success. This study was implemented on the Savannah River Site, an Environmental Research Park, where several riparian forests are recovering from thermal disturbances. The streams in these forests were subjected to thermal discharges that increased flows and resulted in removal of soil and a decline in the amount of woody vegetation. Two of these riparian forests are at different ages post-disturbance and represent different stages of recovery, which provides an exceptional opportunity to study successional processes in riparian forests and enhance restoration efforts. Linear transects perpendicular to the main stream channels were established in 2 recovering riparian forests of different ages (two areas in Pen Branch ~ 8 years post-disturbance; Fourmile Branch ~ 12 years post disturbance) and an undisturbed (thermally) more mature riparian forest (Meyer's Branch ~ 60 years). Along these transects quantitative data were obtained on above and belowground carbon pools and fluxes. Carbon pools exhibited a close correlation with riparian forest development. Biomass and carbon pools increased with increasing riparian forest stand age. The importance of the herbaceous carbon pool declined relative to the total above ground biomass, and the root carbon pool increased with forest age/succession. In general, net primary production (NPP) in young riparian forests (~8-10 years) rapidly approached and even exceeded NPP of more mature riparian forests. Once the herbaceous stage of succession was surpassed, the litterfall component of NPP plays a greater role riparian forests. As a woody overstory became established (after ~ 8-10 years), annual litterfall rates as a function of NPP were independent of forest age. Establishment of woody species occurred ~8 to 10 years after thermal disturbance and litterfall amount in young riparian forests rapidly became comparable to mature riparian forests. Lateral litter movement from the riparian forest toward the stream was less than the amount of litter (carbon pool) deposited from upstream into the riparian forest during a flood event. Overall lateral litter movement supplied less energy to the stream system than vertical inputs. A decline in riparian forest floor biomass was observed with increasing riparian forest development. However, a difference in foliar forest floor percent carbon lended itself to a minimal increase in the forest floor carbon pool with increasing riparian forest age. Woody debris in riparian forests comprised a relatively small carbon pool compared to tree and soil carbon pools. The species composition of litter appeared to be more of an overriding factor influencing decomposition rates than forest age. The influence of litter quality was evident in the decomposition rates of the different litter composites used in this study. In all 4 sites the litter composite from the mature riparian forest decomposed significantly more than the litter composites from the younger riparian forests. The fairly rapid decomposition of red maple (Acer rubrum L.), which was one of the main components in the mature riparian forest litter composite, influenced the greater decomposition rate. The litter composites from the younger riparian forests were similar and both included more decomposition resistant litter types, specifically waxmyrtle (Myrica cerifera L.) and alder (Alnus serrulata (Ait.) Willd.). Decomposition rates did not differ between the individual successional stages. Riparian forests are intimately associated with their hydroperiod. During flood events the riparian forest receives inputs of organic matter and sediment, and the amount of deposition may decrease along a distance gradient from the main stream channel. The differential amount of inputs could affect forest productivity. However, in these riparian forests, a distance gradient effect was not observed. Trends in herbaceous biomass were evident along a microtopographic moisture gradient. The ridge and swale microtopography prevalent in the younger riparian forests counteracted a distance from the stream channel gradient effect across the riparian forest. This study provided knowledge of how carbon pools and fluxes change with riparian forest recovery from disturbance as well as through different seral stages. Implementing the findings of this study will enhance restoration evaluation efforts to ensure that these areas continue to provide the numerous benefits gleamed from them.
Channel Morphology and Riparian Vegetation Influences on Fluvial Aquatic Habitat
Kozarek, Jessica Lindberg (Virginia Tech, 2011-01-14)
As public awareness of river degradation has grown in recent years, the number of stream restoration activities has increased dramatically. Anthropogenic influences at a range of spatial scales from watershed landuse to riparian vegetation management to local channel morphology can have hierarchical relationships to local (meso- and macro-) in-stream habitat characteristics. This research examined these influences first by examining the influence of complex channel morphology on meso-scale brook trout (Salvelinus fontinalis) habitat in Shenandoah National Park, VA, and then by examining the combined influence of watershed urbanization and riparian vegetation (100-200 m reaches) on stream temperature. Moving beyond one-dimensional (1D) averaged representations of fish habitat, this research explored the distribution of two-dimensional (2D) flow complexity metrics at the meso-habitat scale as explanatory variables for brook trout habitat preferences and as potential metrics to evaluate habitat restoration design. Spatial hydraulic complexity metrics, including area-weighted circulation and kinetic energy gradients, were calculated based on 2D depth averaged modeled velocity distributions in two 100-m reaches on the Staunton River. While there were no statistically significant correlations between kinetic energy gradients or area-weighted circulation and fish density, fish density was positively correlated to the percent of the channel dominated by protruding boulders. The structural complexity of areas with protruding boulders create complex flow patterns suggesting that flow complexity plays an important role in available brook trout habitat preferences at the local scale, although the 2D depth averaged model may not have adequately represented this complexity. The 2D distribution of flow characteristics was then investigated further to quantify areas of flow refugia (low velocity shelters) and the relationship between these areas, traditional measures of habitat quality, and fish biomass. Flow complexity in the vicinity of flow obstructions (in this case, boulders) was investigated further using patch classification and landscape ecology metrics. The relative influence of riparian vegetation on stream temperature (another important habitat characteristic) in urban and nonurban watersheds was investigated in 27 paired forested and nonforested reaches in PA, MD, and DE. Riparian vegetation and watershed-scale urbanization both influence stream temperature, which can have profound impacts on in-stream ecosystems. Generally, increased urbanization and removal of riparian forest influenced maximum stream temperatures resulting in higher maximum summer stream temperatures (up to 1.8°C); however, the influence of riparian forests (at at 100-200 m reach scale) decreased with increasing urbanization. Extreme maximum summer temperatures, which are a concern for aquatic biota, increased in both frequency and duration in urban nonforested reaches relative to forested reaches indicating that the addition of a forested 100-200 m long buffer partially mitigated these temperature extremes even in urban watersheds. Overall, changes to channel morphology and riparian vegetation had measurable local effects on stream habitat (temperature and hydraulic complexity) yet the implications of restoration efforts at the local scale on ecosystem services at a larger (km +) scale requires further study.
Characterizing and modeling wet stream length dynamics in Appalachian headwaters
Jensen, Carrie Killeen (Virginia Tech, 2018-05-03)
Headwater streams change in wet length in response to storm events and seasonal moisture conditions. These low-order channels with temporary flow are pervasive across arid and humid environments yet receive little attention in comparison to perennial waterways. This dissertation examines headwater stream length dynamics at multiple spatial and temporal scales across the Appalachians. I mapped wet stream length in four Appalachian physiographic provinces--the Appalachian Plateau, Blue Ridge, New England, and Valley and Ridge--to characterize seasonal expansion and contraction of the wet network at a broad, regional scale. Conversely, most existing field studies of stream length in headwaters are limited to a single study area or geographic setting. Field mappings showed that wet stream length varies widely within the Appalachians; network dynamics correlated with regional geology as well as local site lithology, geologic structure, and the depth, size, and spatial distribution of surficial sediment deposits. I used the field data to create logistic regression models of the wet network in each physiographic province at high and low runoffs. Topographic metrics derived from elevation data were able to explain the discontinuous pattern of headwater streams at different flow conditions with high classification accuracy. Finally, I used flow intermittency sensors in a single Valley and Ridge catchment to record channel wetting and drying at a high temporal resolution. The sensors indicated stream length hysteresis during storms with low antecedent moisture, with a higher wet network proportion on the rising limb than on the falling limb of events. As a result, maximum network extension can precede peak runoff by minutes to hours. Accurate maps of headwater streams and an understanding of wet network dynamics through time are invaluable for applications surrounding watershed management and environmental policy. These findings will contribute to the burgeoning research on temporary streams and are additionally relevant for studies of runoff generation, biogeochemical cycling, and mass fluxes of material from headwaters.
Comparison of Underwater Video with Electrofishing and Dive Counts for Stream Fish Abundance Estimation
Hitt, Nathaniel P.; Rogers, Karli M.; Snyder, Craig D.; Dolloff, C. Andrew (2021-01)
Advances in video technology enable new strategies for stream fish research. We compared juvenile (age-0) and adult (age-1 and older) Brook Trout Salvelinus fontinalis abundance estimates from underwater video with those from backpack electrofishing and dive count methods across a series of stream pools in Shenandoah National Park, Virginia (n = 41). Video methods estimated greater mean abundance of adult trout than did one-pass electrofishing, but video estimates of adult abundance were not different than estimates from three-pass electrofishing or dive count methods. In contrast, videos underestimated the abundance of juvenile trout; we suggest that this is because predator avoidance behaviors by juvenile trout limit their use of microhabitat locations visible to cameras. Integrated abundance estimates from two cameras increased correspondence to comparison methods relative to estimates from single cameras, demonstrating the importance of an expanded field of view for video sampling in streams. Geomorphic features helped to explain methodwise differences: more adult Brook Trout were estimated with video than with three-pass electrofishing as riffle crest depth and boulder composition increased, indicating habitat associations with trout escapement from electrofishing. Our results demonstrated that video techniques can provide a robust alternative or supplement to traditional methods for estimating adult trout abundance in stream pools.
Defining rarity and determining the mechanisms of rarity for North American freshwater fishes
Pritt, Jeremy Joseph (Virginia Tech, 2010-01-06)
Conserving rare species and protecting biodiversity depends on sound information on the nature of rarity. Rarity is multidimensional, presenting the need for a quantitative classification scheme by which to label species as rare or common. I defined rarity for freshwater fishes based on the range extents, habitat breadths, and site abundance and examined the relationship between these dimensions of rarity and imperilment. Imperiled fishes were most often rare by all three dimensions, whereas undesignated species were most often common by all three dimensions. Next, I examined the effect of sampling intensity on observed rarity of stream fish using different numerical and proportional rarity criteria and found that increasing sampling intensity increased the number of species labelled as rare with proportional criteria but did not affect the number of species labelled as rare with numerical criteria. Additional electrofishing passes within a fixed reach increases the likelihood of detecting rare and endemic species. A tradeoff between information collected and sampling resources should be carefully considered in the context of objectives when sampling for rare species. Finally, I examined the effect of regional and watershed habitat variables, biotic interaction variables, and instream habitat variables, on the rare or common status on 23 North American freshwater fishes. I also compared biological and reproductive traits among species classified into the rarity framework. Rarity was successfully explained in 19 of the 23 species and I found that regional and watershed habitat variables were the most important predictors of rarity. I also found that species large body size, high fecundity, and long age at maturity were generally more common by range extent and site abundance while those species that did not guard nests were more frequently rare by site abundance. These results indicate that large-scale variables can be used to successfully predict species rarity and rare fishes differ in their biology and reproduction from common fishes.
Desired Future Conditions of Riparian Areas on Southeastern National Forests
Pert, Heather Anne (Virginia Tech, 2000-12-06)
Development of goals (desired future conditions (DFCs)) based on substantial public involvement is critical to the success of ecosystem management on public lands. I evaluated DFCs of riparian areas on national forests in the southern Appalachian mountains and evaluated a process for involving the public in development of DFCs for riparian areas on the Jefferson National Forest. First, I identified the major components, structures, and functions that are essential to riparian health through a literature review. Second, I examined how the key components, structures, and functions identified in the literature review were addressed in the DFCs and standards and guidelines for eight southeastern national forest management plans. In reviewing forest plans, I found a clear shift from emphasizing water quality in older forest plans to a more comprehensive incorporation of the values and functions of riparian areas in more recent plans. Riparian attributes included in DFCs varied widely and disparities between DFCs for forest plans and measurable criteria in the standards and guidelines often occurred. Finally, I designed, tested, and evaluated a public involvement process that identified public values for use in the development of DFCs for riparian areas on the Jefferson National Forest. I used a combination of alternative dispute resolution techniques and the Analytic Hierarchy Process (AHP), a participatory decision-making tool. I used surveys before and after the riparian meetings to evaluate the effectiveness of the public involvement process. Survey respondents generally were middle-aged, well-educated, high-income males who were long-time residents of the area. Riparian meeting participants indicated that the DFC for riparian areas on the JNF should strongly emphasize water quality and quantity, protection of riparian-dependent species and their habitats, and maintenance of the integrity of the relationship between riparian areas and the surrounding environment. Participants indicated recreational and commodity uses of riparian areas could occur as long as they did not negatively affect the other, more highly valued characteristics of riparian areas. Participants felt that the meetings were fair, that diverse interests were represented, that they had enough information to participate in the process, and that it was a wise use of their time.
Detection probabilities and local population demographics of fishes in urbanized and forested streams of the New River basin, Virginia
Peoples, Brandon Kevin (Virginia Tech, 2009-12-15)
Aquatic biodiversity continues to decline as humans modify the landscape. A population-level approach is necessary to address the mechanisms of impairment in urban stream habitats. When estimating population-level parameters, incomplete detection of individuals must be accounted for to ensure unbiased estimates. In this thesis, I examined differences in the detection probabilities of stream fishes, and used estimates of size/age-specific detection probabilities to reduce bias in estimates of the reproductive success of various fish species in urban and forested stream habitats. In Chapter 1, I examined differences in detection probabilities of stream fishes among electrofishing passes and size/age groups in the middle New River basin, Virginia. I also examined differences in detection probabilities between two physiographic regions: the middle New River basin, and the upper Wabash River basin, Indiana; and evaluated differences between single- and multiple-season estimation methods. I found that for most species, detection probabilities do not differ among electrofishing passes, size/age classes, between the two regions, or between single- and multiple-season estimation methods. I used size/age-specific estimates of detection probabilities to remove bias from relative abundance estimates of steam fish populations in Chapter 2. In Chapter 2, I examined the reproductive success of six lithophilic and speleophilic fishes in urban and forested reaches of 2nd-4th Strahler-order streams in the middle New River basin. I found that binary classification is a poor method of quantifying reproductive success, that the age distributions of many lithophilic and speleophilic species are dominated by adult individuals in urban habitats, and that the population growth rates of speleophils is reduced in urban habitats. These results suggest that although detection probabilities may be equal among various sources of variation, managers should verify this assumption before assuming equal detectability. The results also suggest that reduced reproductive success of speleophilic and lithophilic species in urban stream habitats may be a mechanism of their impairment.
Developing an index of biotic integrity (IBI) for warmwater wadeable streams in Virginia
Smogor, Roy A. (Virginia Tech, 1996)
The index of biotic integrity (IBI) comprises several fish-assemblage attributes, called metrics, that reflect how a site differs from least-disturbed (by anthropogenic influences) conditions. Understanding how metrics at least-disturbed sites vary across landscape classes (e.g., physiographies, ecoregions) and stream sizes helps one determine appropriate regions and stream-size ranges in which to develop and use the IBI. The IBI’s utility depends on how accurately and reliably each metric reflects disturbance. I make recommendations for developing the IBI for use in Virginia. I examined metric variation across landscape classes: physiographies, ecoregions, and drainage groups; and across stream sizes. I examined intra-region relations between metrics and disturbance measures and whether relations met conventional IBI assumptions. Taxonomic metrics (e.g., number of native minnow species) and reproductive metrics (e.g., proportion of individuals as lithophils) varied more across physiographies than across ecoregions or drainages. Trophic metrics (e.g., proportion as invertivores) varied least across landscape classes and most with stream size. For Virginia, I recommend three regions: Coastal Plain, Piedmont, and Mountain, in which to develop and use distinct versions of the IBI. In Coastal Plain, disturbance-vs-metric relations were mostly contrary to IBI assumptions. In Piedmont, trophic and tolerance metrics best reflected disturbance and met IBI assumptions; in Mountain, reproductive metrics did so. Disturbance measures accounted for about 20% of the variance in metrics, suggesting that my data incompletely represented disturbance effects on fish. Until further validation, I recommend that each regional IBI retain at least two taxonomic, two trophic, two reproductive, and one tolerance metric.
Developing Habitat Suitability Criteria for Individual Species and Habitat Guilds in the Shenandoah River Basin
Persinger, Jason William (Virginia Tech, 2003-03-24)
The diversity of fish species found in warmwater stream systems provides a perplexing challenge when selecting species for Instream Flow Incremental Methodology (IFIM) studies. An often-suggested approach has been to use habitat guilds to incorporate the diversity found in these systems. My goal is to determine the feasibility of developing habitat suitability criteria (HSC) for the entire fish assemblage in the North and South Fork Shenandoah River, Virginia, using habitat guilds. I examined the strengths and weaknesses of direct underwater observation via snorkeling and throwable anode electrofishing to sample fish habitat use (e.g., depth, velocity, distance to cover, dominant and subdominant substrate, cover, and embeddedness) indicates that using the data collected from both techniques may produce better criteria than using just one of the two sampling techniques. To develop habitat suitability criteria using habitat guilds I placed each species a priori into a guild based on a hypothesized guild structure. Transitional life stages with significantly different habitat use were placed separately into the guild structure. The four guilds (riffle, fast generalist, pool-run, and pool-cover) were found to be significantly different from each other using the data collected for the species assigned to the guilds. Criteria were then developed for representative species from each guild and the entire guilds. Criteria developed for depth, velocity, Froude number, cover, distance to cover, substrate, and embeddedness were used to estimate a habitat response function (i.e., the relations between usable habitat and stream flow) for a representative species from each guild, the guild itself, and for a second species from each guild for comparisons. Both the representative species and guild criteria showed similar habitat response functions for the riffle guild, fast generalist guild, and pool-run guild. However, neither set of criteria performed well for the pool-cover guild. For guilds, other than pool-cover, either the guild or the representative species approach may be a viable option to developing habitat suitability criteria. The transferability tests were performed to determine if criteria developed in the North Fork Shenandoah River, Virginia would transfer to the South Fork Shenandoah River, Virginia. Only criteria for the margined madtom (Noturus insignis) and the juvenile smallmouth bass (Micropterus dolomieu) transferred for both suitable and optimal habitat. Criteria for mottled sculpin (Cottus bairdi), Cyprinella sp. (spotfin and satinfin shiners), river chub (Nocomis micropogon), adult and juvenile redbreast sunfish (Lepomis auritus), and adult smallmouth bass did not transfer. Only the pool-cover guild criteria transferred for both suitable and optimal habitat, while riffle guild, fast generalist guild, and pool-run guild criteria did not transfer. I recommend the use of site-specific criteria for the South Fork Shenandoah or different variable combinations.
Differential stability of spawning microhabitats of warmwater stream fishes
Smith, Ryan Kennerly (Virginia Tech, 1999-05-20)
I investigated streambed stability in spawning microhabitats of warmwater fishes in the upper Roanoke River, Virginia. Spawning microhabitats used by four reproductive guilds (egg-clusterers, mound-builders, egg-buriers, and pit-builders) were identified and ranges of 15 microhabitat variables used by each guild were compared to available microhabitat conditions to investigate habitat selection. Habitat usage by egg-clusterers was most characterized by selection for spawning rocks in the cobble size range, substrate roughness elements in the cobble to boulder size range, high roughness Reynolds number and moderate water column velocity. The mound-building bluehead chub (Nocomis leptocephalus) was distinct in its selection of substrate in the small gravel range, low water velocity and non-turbulent flow. Egg-buriers were the least distinct of the four guilds, exhibiting much variation in habitat use among the component species. However, all species used areas with small substrate (sand to gravel range), high velocity, and high turbulence. The pit-building central stoneroller (Campostoma anomalum) was distinct in its usage of areas with high velocity and turbulence, gravel sized substrate, and low embeddedness. Stability of each guild's spawning microhabitats was empirically evaluated through analysis of tracer particle movement and repeated surveying of bed elevation along stream transects. Logistic regression equations developed from tracer particle data predicted that microhabitats selected by egg-clusterers are among the most stable of all available habitats during high flows. Microhabitats utilized by mound-builders, egg-buriers, and pit-builders are predicted to be less stable. Repeat transect surveying corroborates model predictions in that egg-burier habitats experienced changes in bed elevation in high flows, while egg-clusterer habitats did not.
Distribution and Life History of Chrosomus sp. cf. saylori in the Upper Clinch River Watershed, Virginia
White, Shannon Lynn (Virginia Tech, 2012-12-21)
In 1999, a new species of minnow, Chrosomus sp. cf. saylori (Clinch dace), was discovered in the Tennessee drainage of Virginia. Chrosomus sp. cf. saylori are listed as a Federal Species of Concern and on Virginia\'s Wildlife Action Plan as Tier II- Very High Conservation Need because of potential threats from habitat degradation, high population fragmentation, and a largely unknown distribution. Consequently, a management plan for C. sp. cf. saylori is of utmost importance, but more information regarding its distribution and life history is required before such a plan can be implemented. In 2011 and 2012 I sampled 60 headwater streams in the upper Clinch River watershed, Virginia. From this and historical data, I conclude that C. sp. cf. saylori are restricted to eight small tributaries to the Clinch River. Multivariate analysis of habitat correlates indicated that C. sp. cf. saylori populations are found in small, high elevation streams with gravel substrate and forested watersheds. Three species distribution models were unable to predict C. sp. cf. saylori distribution. Morphological traits were significantly different between C. sp. cf. saylori and other Chrosomus, thereby providing an initial indication of speciation and differing niche roles. I observed a nest association with Campostoma anomalum. Gonad weight was lower for C. sp. cf. saylori than closely-related congeners. Together, this information indicates that C. sp. cf. saylori are narrowly distributed and populations are small, fragmented, and of questionable viability. In the future, long-term monitoring efforts and genetics analyses should be completed and additional protection measures pursued.

Browsing by Author "Dolloff, C. Andrew"

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