Conserving amphibians in a dynamic world: the introduction of the Northern red-legged frog to Haida Gwaii
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Agriculture is the primary cause of sedimentation, nutrient enrichment, and insecticide contamination of freshwater ecosystems. Despite the widespread co-occurrence of these ecological stressors, little is known about their potential interactive effects. I conducted three experiments manipulating combinations of these stressors in order to evaluate their cumulative effects on freshwater ecosystems at different scales of biological organization (community, ecosystem, meta-ecosystem). First, I evaluated stream invertebrate community responses to sedimentation, nutrient enrichment, and the insecticide chlorpyrifos using laboratory microcosms with distinct microhabitats. I demonstrated that chlorpyrifos can interact non-additively with fine sediment (reversal) and nutrients (antagonism), with potentially deleterious impacts on small-sized invertebrates. Furthermore, invertebrates in gravel microhabitats were more severely affected than those in leaf packs. Second, I manipulated levels of nutrients, sediment, and the insecticide imidacloprid in experimental pond ecosystems. I demonstrated these stressors had antagonistic effects on pelagic and benthic invertebrate diversity. Moreover, the results suggested imidacloprid increased ecosystem metabolism indirectly, through negative effects on invertebrate consumers. Finally, I explored processes at the scale of the river network meta-ecosystem. Using a network of experimental channels, I investigated how multiple-stressor interactions within tributaries affected downstream ecosystems. My results indicated that complex nutrient-sediment interactions within tributaries could strongly alter the flux of organisms from tributaries to downstream ecosystems. Furthermore, I observed that at small spatial scales, these alterations of within-network migration patterns could be more influential than the transport of the stressors from headwaters to recipient ecosystems. My research contributes novel evidence suggesting that complex interactions among nutrient enrichment, sedimentation, and insecticide contamination are frequent in freshwater ecosystems, and have distinct mechanisms operating at different scales. In particular, these findings underscore the importance of considering multiple-stressor interactions in insecticide environmental risk assessments; even at low concentrations, interactions with other stressors may result in unexpected negative effects for aquatic biota and ecosystem processes.
In tropical areas, deforestation and forest degradation are major threats to forests and the surrounding ecosystems, such as riparian forests and streams. These threats to riparian forests and streams in agricultural areas can be reduced by the implementation of riparian buffers. However, disturbances from cleared areas may still impact the forests due to the high edge-to-area ratio of buffers. Selective logging inside the buffers also has the potential to degrade riparian forests and streams. Forest regeneration has the potential to restore ecosystems in degraded lands, but disturbances from ongoing agriculture are expected to arrest or delay the regeneration process in the buffers. I evaluated the efficacy of two riparian buffer management strategies: (1) land abandonment for natural regeneration and (2) the maintenance of mature forest. I also sampled additional sites of different ages to evaluate where buffer treatments fit after riparian forest alterations. I hypothesized that the riparian buffers resulting from land abandonment would have less forest canopy, simpler stand structure, less large wood, higher primary production, and higher decomposition rates than a regenerated riparian forest that was surrounded by mature forest. I expected the same outcomes when comparing the riparian buffers of mature forest versus mature riparian reference sites. I found that forest structure did not differ significantly between riparian buffer management treatments, however, my ordination analysis revealed signs of forest degradation after selective logging in the riparian buffers of mature forest. I found no significant effect of riparian buffer management in any stream variable studied. Large wood was related to channel width and stem density. Stream respiration increased and primary production decreased as the regeneration process advances. Decomposition differed among species, apparently by differences on leaf structural compounds. My results show that both buffer management strategies can be effective for protection of riparian and stream ecosystem in agricultural landscapes. Land abandonment is a viable and inexpensive restoration action where ongoing disturbances are mild and the propagules for regeneration are available. While the implementation of riparian buffers of mature forests is an effective strategy, selective logging should be excluded from these areas as disturbances may intensify in the future.
Untangling the mechanisms linking the physical world to ecological processes is paramount for effectively conserving and restoring habitat for threatened species. Pacific salmon rearing in small streams have been particularly well studied in this regard given that physical habitat features (e.g., velocity) strongly influence their performance and that habitat alteration is a major cause of their decline in many areas. However, despite strong evidence that stream salmonids are food limited, we lack commensurate understanding of how habitat influences their food supply - suspended invertebrates drifting downstream (invertebrate drift). Consequently, the mechanisms linking physical habitat structure to salmonid production remain unclear. My dissertation attempts to address this issue. First, in Chapter 2, I review and synthesize the mechanisms underlying invertebrate drift, discuss potential caveats in methodology, and identify key knowledge gaps. I particularly highlight how the physical and behavioural processes governing drift entry are highly dependent on context-specific abiotic and biotic attributes (e.g., hydraulics, individual condition). In Chapter 3, I use flow manipulation experiments to show that some of this context dependency can be explained by considering behavioural and morphological traits of invertebrate taxa, which underlie their tendencies to drift behaviourally or passively; for instance, body shape predicted the magnitude of responses to increased flows. In Chapter 4, I show that aggregate community-level drift rates vary spatially in streams over scales relevant to individual drift-feeding salmonids. Specifically, I measured spatially explicit rates of drift production, demonstrating that shallow high velocity riffles and deep low velocity pools form distinct sources and sinks of drift within stream networks. In Chapter 5 I build on this result to show that drift generation in riffles coupled with strong preferences for low velocity pools by salmonids leads to maximum fish production occurring in habitats with intermediate ratios of pool-riffle areas; in essence, a trade-off between increasing space but declining food as pool area increases. I extend these results with bioenergetic simulations to show that the shape of this trade-off is sensitive to alternative modes of prey delivery (e.g., aerial inputs of terrestrial invertebrates), which may be decoupled from in-stream habitat conditions.
Freshwater ecosystems are important natural emitters of the greenhouse gas CO₂. The magnitude and direction of the exchange of CO₂ between freshwaters and the atmosphere, or flux, is influenced by the concentration of CO₂ in the water. Every organism within a freshwater ecosystem influences the net CO₂ balance of that ecosystem either through respiration, photosynthesis or both. Thus, large changes in populations due to natural or anthropogenic stressors and the underlying food web structure of the ecosystem have the potential to alter CO₂ fluxes of aquatic ecosystems. To evaluate the influences of species loss on food web structure and CO₂ fluxes of aquatic ecosystems, I experimentally manipulated species from different consumer trophic levels (predator, grazer, or detritivore) and tested the effects of these losses on CO₂ fluxes of experimental streams, ponds and bromeliads. In streams, I found that influences on CO₂ emissions were most sensitive to the loss of a predatory insect compared to other trophic levels, including a tadpole grazer and an insect detritivore. Similarly, the removal of a fish predator to ponds or an insect predator to bromeliads resulted in trophic cascades that significantly influenced the CO₂ flux of the ecosystem. Both the identity of the predator and interspecific competition among predatory insects influenced the strengths of cascading effects of predators on CO₂ emissions from bromeliads. However, across all three ecosystems (streams, ponds, and bromeliads) predators, via trophic cascades, had surprisingly consistent effects on the CO₂ flux of the ecosystem. Finally, as alterations to predator abundance often occurs in concert with increasing water temperatures and nutrient loading, I determined the individual and interactive effects of these stressors on pond communities. I found that nutrients often increased top-down control of predators on CO₂ fluxes, but the individual effect of warming and its combined effects with nutrients had negative effects on both consumers and primary producers making predictions about CO₂ fluxes complicated. My results provide novel insights into the influence of predators and food web structure on CO₂ fluxes and the potential for predator loss to markedly alter CO₂ fluxes of freshwaters.
Freshwater ecosystems worldwide are degraded by habitat loss, fragmentation and conversion. The practice of ecological river restoration has developed to address degradation, but there has been limited monitoring and assessment of river restoration projects that could be used to improve the science of restoration ecology. I used meta-analysis and studied floodplain ponds restored for juvenile coho salmon (Oncorhynchus kisutch) in southwestern British Columbia, Canada to test ecological and conservation science hypotheses about how restoration projects are planned and assessed. I evaluated the efficacy of the umbrella species concept, which suggests that conservation strategies designed for one species may benefit co-occurring species, using meta-analysis. I empirically assessed the potential for coho to be an umbrella species in restored ponds. I studied the relationship between biodiversity and ecosystem function (i.e., standing biomass) and explicitly considered the role of habitat complexity in mediating that relationship. I evaluated the influence of habitat at different scales (watershed, pond and micro-habitat) on the abundance and biomass of juvenile coho and other aquatic vertebrates. I used standard meta-analytic techniques to assess the umbrella species concept and found conservation strategies designed for umbrella species generally benefit co-occurring species. For the empirical studies, I sampled vertebrates in 17 restored ponds in three watersheds three times over a year. I sampled benthic invertebrates and algae once and documented habitat (e.g., depth, cover) at the pond and trap scale. Coho abundance and biomass, as well as that of other aquatic species, varied across ponds indicating a gradient in response to restoration. There was a positive relationship between species diversity and standing biomass, although that relationship was not consistent across taxonomic groups or with respect to habitat complexity. There was a relationship between watershed-scale habitat features (e.g., landcover, elevation) and the relative abundance and biomass of species present, however, different species responded similarly to micro-habitat types suggesting that watershed scale factors acted as a filter for community composition. This study demonstrated that valuable insight into restoration can be gained by studying patterns from a broad study of restored systems and that restoration designed around a single species can benefit other species.
High altitude wetlands of the Central Andes Cordillera in South America are unique ecosystems with valuable ecosystem functions and one of the environments most threatened by climate change. They play a significant role in sustaining endemic biota, in providing the grasslands for herd of alpacas, llamas and vicuñas and by storing water and releasing it during the year to one of the driest regions on the earth, the Atacama Desert. This ecosystem is dependent on groundwater sources, and vegetation regulates the amount of water available during the dry periods. In Chile, the increasing demand for water requires more technical knowledge and research in order to prevent further degradation. The objective of this research is the description of Tarapacá and Atacama regions’ wetlands plant communities, the abiotic factors and human impacts that are more strongly associated with them by multivariate analysis and a remote sensing approach. Chapter 1 is a review of high altitude Andean wetlands and their importance. In Chapter 2, I identified differences in plant communities’ structure. Each region was distinguished by 5 different plant communities according to the vegetation wetland types. Abiotic factors and physical attributes that were more strongly associated with plant communities were the number and width of principal streams found on the wetland and amount of rocks, bare land and percent of organic matter along the vegetation transects. Using field work and remote sensing, in Chapter 3, I performed a spectral discrimination among plant communities using IKONOS-2 and Geoeye-1 high resolution satellites images. They were used to identify which bands and vegetation indices were the most effective for discriminating vegetation classes. Vegetation classes did express different spectral behaviors. The classes with more reflectance variation were mixed grasses with Oxychloe andina, mixed grasses with salt patches and mixed grasses with Zameioscirpus atacamensis, while classes dominated by O. andina, Z. atacamensis and Festuca chrysophylla expressed less variation on the spectral range. General Discriminant Analysis showed that the most important spectral bands and vegetation indices for distinguishing differences between vegetation classes were Band 1-blue, band 4-NIR and the Wide Dynamic Range Vegetation Index.
Understanding the impacts of hydrological drought is crucial to the conservation of freshwater fishes. In British Columbia, Nooksack dace (Cyprinidae: Rhinichthys cataractae) are an endangered riffle specialist and are threatened by extremely low summer flows. The purpose of this thesis was to explore the impacts of drought on Nooksack dace, whether pool habitats may act as refugia to mitigate these impacts, and to define minimum environmental flow requirements. The first two objectives were addressed using a combination of field survey and experimental manipulations. A reduction in Nooksack dace population size with declining summer flow in Bertrand Creek, and a marked decrease in growth at low discharge in experimental riffles, indicated that low discharge has negative impacts on dace at both population and individual levels. Pool habitats were found to play a minor role in mitigating the negative impacts of hydrological drought (e.g., decreased growth rate), save as a refuge from stranding when riffles dewater. The third objective was addressed using the Instream Flow Incremental Methodology (IFIM). Because this study involved an endangered species an emphasis was placed on evaluating two fundamental assumptions of the methodology. Experimental results for Nooksack dace growth at different depths and velocities provided support for the first assumption, that density-based Habitat Suitability Curves (HSCs) accurately reflect habitat quality, but only for the lower limits of the HSCs. Next, a significant positive relationship between Weighted Usable Area (WUA) and dace biomass was found, supporting the assumption that such a relationship exists. However, this relationship was weak indicating a high degree of uncertainty in how Nooksack dace biomass will respond at high discharges. The IFIM model predicted that habitat availability for Nooksack dace begins to decline most rapidly at discharges of 0.12 m³.s-¹. As there is low confidence in upper ranges of the HSCs this low flow threshold may underestimate declines with discharge, and therefore protection of at least 0.12 m³.s-¹ is considered necessary for the persistence of Nooksack dace individuals and populations. Compared to conventional instream flow criteria, 0.12 m³.s-¹ represents ~10% mean annual discharge which is the threshold for severely degraded habitat.
Pacific salmon (Oncorhynchus spp.) life cycles involve completion of several developmental stages including the alevin stage. As alevins, sockeye salmon are found within freshwater gravel redds where they utilise yolk sacs for nutrition, growth and development. Flow mediated scour events pose a common threat of destruction to both redds and fragile alevins during a several month period of winter incubation. However, to date, there is very little research on the impacts of early forced emergence of alevins. Using sockeye salmon (Oncorhynchus nerka) as a model, simulated elevated discharge event (SEDE) experiments were conducted to examine the relationship between sockeye alevin development, SEDE exposure and alevin survival. Following five weeks of SEDE experiments, survival rates were found to be significantly correlated to both alevin developmental stage and length of elevated discharge exposure. SEDE experiments were followed by experiments designed to investigate the ecological competence level of alevins following forced early dislodgement. Repeated tests during a five week interval immediately following egg hatch indicated that alevins subjected to SEDE exposure took longer than unexposed alevins to rebury in gravel. Alevins exposed to SEDEs took longer to rebury as they developed, but increased their overall ability to rebury. Neither SEDE exposed or unexposed alevins exhibited abilities to initiate exogenous feeding given forced, early emergence. Survival rates of sockeye salmon alevins both during and after SEDE testing increased significantly with advances of developmental stage. Older, larger alevins also exhibited improved performance in responding to ecological challenges presented in laboratory experiments. Knowledge gained from this research has practical implications for water managers and suggests that: (a) the probability of scour induced mortality of both unhatched eggs and alevins is likely similar up to at least 3 weeks after egg hatch, (b) survival rates and ecological competence of alevins has improved significantly by four weeks following egg hatch, and (c) survival of alevins forced into an epibenthic or water column environment as late as one week before volitional emergence is unlikely to differ greatly from that of unforced emergent fry.
The alluvial forest of the Carmanah River valley on the west coast of Vancouver Island, British Columbia, was studied to examine the role of hydrogeomorphic disturbance in perpetuating the shifting-mosaic of habitats within this diverse ecosystem. Field-based research was complemented by a landscape-scale analysis that examined changes in the extent of specific forest types using a 70-year aerial photographic record. Thirty-eight plots containing 4509 trees were sampled for forest structure, composition, age, understory composition, and elevation above the contemporary channel. These field data, including a vegetation chronosequence spanning over 500 years, were used to examine vegetation dynamics. Over the past century, Carmanah River has eroded nearly 30% of the alluvial forest in this study area – 65% over the past 500 years. High magnitude floods result in diminished floodplain forest area by converting forests to channel. This results in a subsequent course of vegetation succession and geomorphic development. Fluvial deposits are colonized by a high density of Alnus rubra accompanied by a subcanopy of Picea sitchensis individuals. As Alnus die off after 60-100 years, Picea increasingly dominates the canopy while Tsuga heterophylla regenerate within the understory. The original cohort of Picea dies off after 300-500 years, which allows Tsuga to dominate old growth terrace forests. Picea or Alnus do not tend to regenerate under these dense canopies and without disturbance Tsuga may remain dominant indefinitely. Understory composition was related to landform age, however species distributions at low elevation floodplain sites were also driven by elevation above thalweg and flood frequency. Light availability was also a significant factor in driving community composition. It appears that understory dynamics were linked to overstory succession and geomorphic development processes, which alter environmental conditions at the understory level. That is, species distributions are driven by dynamic environmental filters, which change as a result of biogeomorphic succession. Mature forest patches tended to persist longer than young forests. The landscape composition reflects a balance between episodes of hydrogeomorphic disturbance and periods of successional development. Increased hydrogeomorphic disturbance rates due to climate change have the capacity to alter the landscape composition resulting in diminished mature forest area.
Multi induction-motor (IM) drives are commonly used to share a mechanical load in a wide range of industrial applications. In many existing auxiliary applications, the traditional low-cost Volts-per-Hertz (V/F) drives are typically used in speed control mode to simultaneously operate several IMs. In multi-machine load-sharing applications, it is preferred to have number of identical IMs to share the load equally. Under ideal conditions, the identical IMs would operate with equal loading. However, in practice deviations of the load sharing among the IMs is possible due to many factors including variations in internal or external parameters and operating conditions of each individual IM. Such deviations may result in disproportionate sharing of the mechanical load and even overloading one or several machines while some machines may be under-loaded. The basic low-cost variable frequency drives (VFDs) with traditional open-loop V/F control scheme fail to share the load under such conditions.In this Thesis, two new methods are proposed to address the load sharing problems under an internal disturbances (such as rotor resistance variations) and external disturbances (such as wheel slippage due to snow/water/oil etc.). The new methods are shown to be effective in sharing the load under disturbances. Moreover, the proposed methodologies may be readily extended to an arbitrary number of motors driving a common mechanical load, and are easy to implement with traditional/existing low-cost VFDs, which may be advantageous for many existing or legacy applications.
Streams are strongly linked to their terrestrial environments through processes which influence habitat structure and food availability at several, nested scales. While forest practices can affect the hydrological, sedimentation and disturbance regimes, the relationship between community structure and forest practices across broad scales of natural environments is not well understood. In this study, the relative influence of environment and forest harvest attributes on stream community composition was examined in 143 unique 1st to 6th order streams, across a broad geographic scale in northwest B.C. Environment and forest harvest variables explained unique aspects of the community composition using canonical correspondence analysis (CCA), although landscape level environmental variables representing catchment topography and hydrology were selected first using a stepwise procedure. Using partial CCA, 20% of the variation in community structure between sites was explained by environment variables, 12% by forest harvest variables, and 4% was shared between the two sets of variables. The low proportion of shared variance suggested low redundancy between the two sets of variables. Variables describing recent forest harvest (15 years prior to sampling or less) explained unique aspects of the community composition compared to variables describing older forest harvest (more than 15 years prior to sampling), perhaps suggesting partial recovery of the stream community after 15 years. The 143 stream sites were sorted into three LAND USE groups based on the proportion of forest harvest within the catchment basin. Using catchment area as a covariate, relative abundance and rarified taxa richness increased by 30% and 20% respectively, while the proportion of EPT individuals decreased, in catchments with > 15% harvest compared to undisturbed catchments. Distance-based ordination scores (nonmetric multidimensional scaling) changed significantly between the three LAND USE classes of forest harvest on both axes.The effects of forest harvest on streams were confounded with natural environmental gradients. Generally, the catchment basins with >15% harvest were larger, with less topographic relief, more lakes and wetlands, and less rapid drainage characteristics when compared to undisturbed catchments.
To have greater predictive abilities for informed resource management guidelines for freshwater species protection and management, we need to increase our limited knowledge of the many aquatic species that inhabit small coastal streams. Coastal cutthroat trout (Oncorhynchus clarkii clarkii) are common to small streams in the Pacific Northwest and are a species of concern or threatened throughout their native range. To address knowledge needs I (1) examined the seasonal variation in survival rates of coastal cutthroat trout across a size gradient of smaller streams in coastal BC; and (2) contrasted 10th year post-harvest seasonal trout body condition and relative abundances, and thermal and physical habitats with pre-harvest and 4th year post-harvest values in small streams. The survival study used a robust mark-recapture design stratified seasonally to estimate monthly survival rates; and the streamside harvest study used a multi-year, replicated, before-after-control-impact design. Within the size range of smaller streams studied (n = 7), availability of aquatic habitat (i.e., residual depth) at low-flows was the best predictor of monthly survival rates (p = 0.011), supporting my hypothesis that greater availability of habitat confers higher survival in trout. In addition, a fitted curve suggested an asymptotic relation between water depth and survival rates; where beyond 25 cm of water, greater depth did not confer greater benefits to trout survival. Survival estimates also showed that the summer season had the lowest monthly survival rates across all streams in our study area. Post-harvest effects were not detected in trout relative abundances in the 10th year; however body condition had significantly (p
The following is a selection of grants for which the faculty member was principal investigator or co-investigator. Currently, the list only covers Canadian Tri-Agency grants from years 2013/14-2016/17 and excludes grants from any other agencies.
Dudaniec, Rachael Y. and Richardson, John S.
Herpetological Conservation and Biology 7 (1) 1-15
Atwood, Trisha and Richardson, John S.
Insects 3 (2) 432-441
Deguise, Isabelle and Richardson, John S.
Northwestern Naturalist 90 (1) 35-38
Richardson, John S. and Thompson, Ross M.
Conservation Biology Series (Cambridge) 16 244-263
Richardson, John S.
Canadian Entomologist 140 (4) 495-509
Richardson, John S. and Danehy, Robert J.
Forest Science 53 (2) 131-147
Marczak, Laurie B. and Richardson, John S. and Classen, Marie-Claire
Canadian Field-Naturalist 120 (3) 347-350
Gomi, T. and Sidle, R. C. and Richardson, J. S. and Moore, R. D.
American Fisheries Society Annual Meeting 133 202
Richardson, John S. and Jackson, Michael J.
Handbook of ecological restoration. Volume 1: principles of restoration. 300-323
Rowe, L and Richardson, JS
Oecologia 129 (3) 473-480
Kiffney, PM and Richardson, JS and Feller, MC
Archiv Fur Hydrobiologie 149 (1) 109-129
Richardson, JS and Neill, WE
Northwest Science 72 122-123
Healey, M.C. and Richardson, J.S.
Archiv fuer Hydrobiologie Supplement 113 (1-4) 279-290
PERRIN C J and WILKES B and RICHARDSON J S
Canadian Technical Report of Fisheries and Aquatic Sciences 1774 (1-2) 555-576
RICHARDSON J S
Bulletin of the Ecological Society of America 71 (2 SUP) 302
RICHARDSON J S
Bournaud, M. and H. Tachet (Ed.). Series Entomologica (the Hague), Vol. 39. Proceedings of the Fifth International Symposium on Trichoptera; Lyon, France, July 21-26, 1986. Xxiii+397p. Kluwer Academic Publishers: Dordrecht, Netherlands; Boston, Massachuse 211-216
WIGGINS G B and RICHARDSON J S
Psyche (Cambridge) 93 (3-4) 187-216
RICHARDSON, JS and MACKAY, RJ
Archiv Fur Hydrobiologie 99 (4) 515-528
Canadian Journal of Zoology-Revue Canadienne De Zoologie 62 (8) 1561-1565
RICHARDSON, JS and CLIFFORD, HF
Canadian Journal of Zoology-Revue Canadienne De Zoologie 61 (11) 2434-2445