Episodes of stream acidification are suspected to be the primary cause of the extirpation of native southern brook trout (Salvelinus fontinalis) from six headwater streams in the Great Smoky Mountains National Park (GRSM). During periods of increased flow from storm events, stream pH can drop below 5.0 (minimum of 4.0) for 2-days or longer. To provide evidence that native brook trout are impacted by stream acidification, in situ bioassay experiments were conducted. Changes in stream water chemistry and brook trout physiology were determined during a 36-hour acidic episode at three remote headwater stream sites in the Middle Prong of the Little Pigeon River watershed. Conductivity, pH, turbidity, stage height and temperature were monitored continuously; and water samples were collected for laboratory analyses (metals, cations, anions, ANC). Native brook trout were put in cages at the three sites and fish were sampled before and after the acid storm event. Physiological stress in brook trout was assessed by measuring whole-body sodium in individual fish sampled before and after the stormflow, and evaluating whole-body sodium loss as a response to acid conditions. The pH decreased at all three sites during the acidic episode. Stream pH dropped to approximately 5.0 at two sites and 4.66 at the third site. Prior to the storm, there was no difference in the whole-body sodium concentrations in trout between the three sites. Following the storm event, in trout from the site that experienced the lowest pH, whole-body sodium levels were reduced significantly relative to a) the pre-storm condition and b) trout from the other sites. Results demonstrate that stream acidification can negatively affect native southern brook trout physiology in the GRSM under actual field conditions. Trout lose the ability to regulate critical blood ions, as exemplified by a loss of whole-body sodium, when stream pH was less than 5.0 for 20 hours. Loss of sodium is an important indication of physiological stress in fish exposed to acid waters. This observation supports the hypothesis that episodic acidification of streams could be limiting native brook trout from occupying headwater streams in the GRSM.

Episodes of stream acidification are suspected to be the primary cause of the extirpation of native southern brook trout (Salvelinus fontinalis) from six headwater streams in the Great Smoky Mountains National Park (GRSM). During periods of increased flow from storm events, stream pH can drop below 5.0 (minimum of 4.0) for 2-days or longer. To provide evidence that native brook trout are impacted by stream acidification, in situ bioassay experiments were conducted. Changes in stream water chemistry and brook trout physiology were determined during a 36-hour acidic episode at three remote headwater stream sites in the Middle Prong of the Little Pigeon River watershed.Conductivity, pH, turbidity, stage height and temperature were monitored continuously; and water samples were collected for laboratory analyses (metals, cations, anions, ANC). Native brook trout were put in cages at the three sites and fish were sampled before and after the acid storm event. Physiological stress in brook trout was assessed by measuring whole-body sodium in individual fish sampled before and after the stormflow, and evaluating whole-body sodium loss as a response to acid conditions.The pH decreased at all three sites during the acidic episode. Stream pH dropped to approximately 5.0 at two sites and 4.66 at the third site. Prior to the storm, there was no difference in the whole-body sodium concentrations in trout between the three sites. Following the storm event, in trout from the site that experienced the lowest pH, whole-body sodium levels were reduced significantly relative to a) the pre-storm condition and b) trout from the other sites.Results demonstrate that stream acidification can negatively affect native southern brook trout physiology in the GRSM under actual field conditions. Trout lose the ability to regulate critical blood ions, as exemplified by a loss of whole-body sodium, when stream pH was less than 5.0 for 20 hours. Loss of sodium is an important indication of physiological stress in fish exposed to acid waters. This observation supports the hypothesis that episodic acidification of streams could be limiting native brook trout from occupying headwater streams in the GRSM.

Plants have evolved a wide variety of physical and biochemical defense mechanisms to protect against herbivores and pathogens. When wounded, hybrid poplar (Populus trichocarpa X P. deltoides) upregulates a suite of defense-related genes, some of which encode anti-herbivore proteins. Among the most strongly insect- and wound- induced genes in poplar is an acid phosphatase gene (AP). APs are enzymes that function in hydrolyzing phosphate from P-monoesters and anhydrides and are involved in the remobilization of phosphate from these pools. However, APs may also play a role in the defense against insects by acting as anti-insect proteins. In poplar, AP mRNA induction occurs within 1.5 hours, which is similar to other known poplar defense genes. In the work described in this thesis, a 2 to 3-fold increase in the extractable AP activity was demonstrated in the leaves of saplings 4 days post wounding. These results suggest the poplar AP is part of the defense response against leaf-eating herbivores. In another type of defense reaction, when hybrid poplar is infected by the pathogen Melampsora medusae, which causes poplar leaf rust, flavonoid pathway genes are induced. This induction leads to the accumulation of proanthocyanidins (PAs), compounds with antimicrobial activity. The expression of several flavonoid-specific glycosyltransferase (UGTs) genes were correlated with these PA genes, suggesting a role for them in PA biosynthesis. Therefore, the second objective of this thesis was to functionally analyze these UGT genes. UGTs are enzymes which catalyze glycosylation reactions, which is typically one of the last steps in the biosynthesis of plant phenolic compounds. Active recombinant proteins for two highly induced poplar UGTs (PtUGT1 and PtUGT2) were generated, and sequence analysis grouped these proteins with others involved in the glycosylation of flavonols and anthocyanidins (UGT78 family), and not PA precursors as expected from microarray data. Enzymatic analysis of one of these proteins (PtUGT1) supports this phylogenetic grouping. By contrast, PtUGT2 does not use any known flavonoid substrates. To investigate the role of PtUGT1 in planta, transgenic poplars were produced that suppressed the expression of this gene using RNA interference. Phytochemical analysis of these knockdown plants were found to display decreased levels of PAs. Tissue survey analysis also implicates the PtUGT1 gene in PA biosynthesis since phytochemical analysis correlates with gene expression of PtUGT1 in the various tissues tested. Thus the data suggests that this UGT gene may be involved in PA biosynthesis. / Graduate

Contiguous macroscopic charcoal analyses were performed on a 9.03 m long lake sediment core from Roe Lake on Pender Island in the Gulf Islands National Park Reserve of British Columbia, Canada to reconstruct the island’s fire history over the last 10,000 years. Charcoal particles >150μm were counted to quantify charcoal concentrations, charcoal accumulation rates and mean fire return intervals. Results show that the early Holocene was characterized by high charcoal accumulation rates and frequent low-severity fire with a mean fire return interval of 100 ± 29 years. Forests at the time were dominated by Pseudotsuga menziesii with an open canopy and fern taxa, particularly Pteridium aquilinum, being common in the understorey. This open vegetation, coupled with warm and dry summer climate, likely created conditions conducive to this fire regime. Charcoal accumulation rates decreased in the middle to late Holocene, and fire frequency decreased, resulting in a mean fire return interval of 167 ± 43 years. Climate cooled and moistened along with a decrease in seasonality during this time and the canopy closed, establishing closed-canopy Pseudotsuga menziesii forests. Climate appears to be the primary factor controlling fire regimes near Roe Lake for most of the Holocene. At times, shifts in the fire regime cannot be explained by changes in climate. Fire frequency increased between 7000-5000 cal yr BP, coincident with a peak in Quercus garryana pollen, despite cooling and moistening climate. Fire likely maintained patches of Q. garryana savanna during this time. Fire again became more common contrary to trends in climate after ~2500 cal yr BP. This late Holocene increase in fire is also seen elsewhere in the Pacific Northwest and may be a reflection of increased climate variability due to more frequent El Niño events or an increase in human-lit fires. Indigenous populations on southern Vancouver Island commonly used fire as a resource management tool and it is likely that people on Pender Island did as well. As fire management practices shift from fire suppression to more sustainable practices, this study offers the Gulf Islands National Park Reserve important baseline information on the area’s natural fire regime to help guide future conservation efforts. / Graduate / 2023-04-07

No description available.

The purposes of this study were to determine if Rhododendron macrophyllum has the potential to inhibit the growth of other species through the production of water-soluble toxins which are leached out of its litter by rainfall, and to determine if this potential is realized in the field. The study was therefore composed of two part: 1) a series of bioassays to determine the presence an activity of water-soluble phytotoxins in R. macrophyllum leaf litter, and 2) a field study to describe vegetational patterns associated with R. macrophyllum in a western Cascades clearcut.

Pikas from four colonies in the Cascade Mountains of Oregon were examined. Two colonies were chosen from within the geographical distribution of two nominal subspecies. A discriminate analysis of morphological measurements taken from the specimens showed that each colony could be distinguished from each other. Each colony studied showed more intra-colony similarity than inter-colony similarity regardless of distance separating the colonies or subspecies designations. The results indicate that the validity of subspecies designations for this species can be questioned.

Changes in land use such as mountaintop removal mining with valley fills (MTR/VF) affect chemical, physical, and hydrological properties of headwater streams. Although numerous stream taxa have experienced significant declines from MTR/VF, stream salamanders appear to be particularly sensitive. Yet, the specific mechanism(s) responsible for the population declines has eluded researchers. We sampled salamander assemblages across a continuous specific conductivity (SC) gradient in southeastern Kentucky and estimated occupancy rates and abundance estimates along this gradient. We also examined the diet of larval and adult salamanders to determine if autochthony (A/T prey), total prey volume, and body condition is influenced by SC. As SC increased, occupancy and abundance declined consistently among all salamander species and life stages. Diet composition explained the declines; for example, larval salamanders experienced a 12−fold decline in autochthony, a 4.2−fold decline in total prey volume, and a rapid decline in body condition as SC increased. Our results indicate that SC indirectly affects stream salamander populations by eliminating an adequate availability of aquatic prey for salamanders, which in turn lead may lead to reduced population persistence in streams with elevated SC.

Forests are an important component of the global carbon (C) cycle and contribute to climate change mitigation through atmospheric C uptake and storage in biomass and soils. However, the forest C sink is susceptible to disturbance, which modifies physical and biological structure and limits spatial extent of forests. Unlike severe, stand-replacing disturbances that reset forest successional trajectories and may simplify ecosystem structure, moderate severity disturbances may instead introduce complexity in ways that sustain net primary production (NPP), leading to the phenomenon of “NPP resilience.” In this study, we examined the linkage between disturbance severity and ecosystem biological and physical structural change, and implications for NPP within an experimentally disturbed forest in northern Michigan, USA. We computed spatially resolved and spatially agnostic metrics of forest biological and physical structure before and 10 years after disturbance across a continuum of severity. We found that while biological structure did not change in response to disturbance, three of four physical structural measures increased or were unimodally related to disturbance severity. Physical structural shifts mediated by disturbance were not found to directly influence processes coupled with NPP. However, decadal changes in the spatial aggregation index of Clark and Evans, though not a function of disturbance severity, were found to predict canopy light uptake, leaf physiological variability, and relative NPP within plots. We conclude that ecosystem structural shifts across disturbance severity continua are variable and differ in their relationship to NPP resilience.

One serious problem faced by the forest industry in the Pacific Northwest is poor regeneration of commercial trees on land which is harvested and subsequently dominated by brush species. In Coastal Oregon, salmonberry is one of these brush species. Detailed investigations of field sites indicate that light intensity in the brush stands was low but sufficient for germination and early growth of Douglas-fir seedlings and soil moisture percentages and nutrient levels were high enough to support early Douglas-fir growth. Laboratory tests demonstrated the presence of leachable phytotoxins in the leaves of salmonberry. The hypothesis resulting from this study is that salmonberry releases a phytotoxin that in synergism with environmental stresses (i.e., light), suppresses germination and growth of Douglas-fir seedlings in the field.