Forest densification in response to a century of fire suppression in Sierra Nevada mixed conifer forests has decreased conifer regeneration and survival. Increases in overstory biomass and decreases in canopy heterogeneity, along with decreases in shrub cover in the understory, has created unfavorable establishment site conditions for conifer species. Establishment site conditions are key in promoting germination and establishment of conifers seeds and in determining the survival of these seedlings into the overstory. These changes in establishment site suitability resulting from the removal of disturbance from these forests has decreased conifer regeneration and survival into other age classes. In Sierra Nevada mixed-conifer forests, the relationship between establishment site conditions and conifer regeneration is multifaceted, and changes to microsite conditions as a result of fire suppression further confounds our understanding of conifer regeneration requirements and survival probability. Additionally, the relationship between Sierra Nevada shrubs and conifer seedlings is complex and not clearly understood, as these studies have been over relatively short time frames, and no research has examined the relationship between shrub cover and conifer seedlings throughout time in the Sierra Nevada. Using a historic dataset beginning 85 years ago and a re-measurement of the same plots, I examined changes to conifer regeneration dynamics from historic to current forests in response to forest densification following a century of fire suppression. I also analyzed the importance of establishment conditions on seedling survival into the canopy and how these factors have changed throughout time. The relationships between seedlings and their establishment site conditions will influence regeneration and survival, which will ultimately determine the structure and composition of future forests.

Climate change assessments predict that rates of relative sea level rise will increase in the future, leading to enhanced inundation of low-lying coastal regions and a 20 – 50 % decline in salt marsh area by 2100. Global sea level rise began accelerating in the late 19th to early 20th century, and local rates along the U.S. mid-Atlantic coast are twice as fast as global estimates. Frequent flooding and salt stress associated with sea level rise lead to coastal transgression, and the survival of ecosystems depends on their ability to migrate inland faster than they erode and submerge. Here, I compared aerial imagery analyses and field measurements to test the hypothesis that marsh migration into retreating terrestrial forests is fundamentally tied to sea level rise, and that sea level rise does not necessarily lead to overall habitat loss. For my first chapter, I compared the areal salt marsh extent between historical topographic maps and modern aerial imageries across the entire Chesapeake Bay, and found that marsh migration into terrestrial forests largely compensated for marsh erosion at the seaward edge during the last century. This emphasizes that the location of coastal ecosystems changes rapidly on centennial timescales, and that sea level rise does not necessarily lead to overall habitat loss. For my second chapter, I reconstructed the position of coastal treelines through time at five study sites along the U.S. mid-Atlantic coast to identify long- and short- term drivers of coastal forest retreat. My findings suggest that 20th century migration rates greatly exceed pre-industrial rates (< 1875 CE), and have generally accelerated throughout the last century in parallel with accelerating rates of relative sea level rise. Previous work predicts widespread marsh loss as a response to sea level rise, but underestimates the potential for marshes to migrate inland. Although anthropogenic barriers may locally prevent marsh migration into retreating coastal forests, my work finds that about 400 km2 (100,000 acres) of uplands have converted to marshes in the Chesapeake region since the late 1800s, and that this process was responsible for the formation of about 1/3 of all marsh area. Beyond the Chesapeake, my work reveals that forest retreat is fundamentally tied to the rate of sea level rise, and is accelerating through time. Therefore, management efforts that allow marshes to migrate into adjacent uplands may help preserve marshes by exploiting their ability to quickly adapt to environmental change.

Juvenile weakfish Cynoscion regalis, life history was studied in the York River estuary, Virginia. to verify daily aging methods of juvenile fish, both male and female adults were induced to spawn by injection of 200 IU Human chorionic gonadotropin/Kg wet weight. Subsequent larval and juvenile fish were reared up to 275 days with wild plankton and a daily rotating diet of squid, liver, Anchoa mitchilli, and Menidia menidia. Otoliths and scales were examined for daily microincrements patterns. Otolith ring counts were highly variable (31% varied by &>& 15% among 3 counts). Two problems were evident: (1) Microincrements frequently split to form two increments; and (2) Otoliths from a size series of fish (6.12-13.1 mm) indicated that weakfish otoliths grew by bud formation rather than concentric deposition. Scale circuli showed little variation between counts (99.5% of 2 counts from an individual scale were the same). Daily scale deposition was suggested by rearing up to 100 days, after which ring deposition was less than daily, however further research is needed because only one fish was reared past 25 days. The advantages of scale circuli counting over otolith increment counting were increased precision and ease of preparation. Field samples were collected weekly from the York River channel, at night using a 4.9 m, 1.5 mm cod end, trawl, during the weakfish nursery period (Aug-Oct 1983). The new technique of daily aging by scales, was applied to 845 of 922 weakfish collected. Counts ranged from 3 to 100 circuli/scale. Three cohorts were defined from the 1983 0-age fish. Growth rates estimated from scales (0.76-1.13 mm/d) were similar to those from length frequencies (1.0-1.2 mm/d). Analysis of covariance showed a significant difference (0.05 level) in growth rates among cohorts and among stations, but third order interactions (station, cohort, growth rate) were not detected. Mortality/migration rates estimated from decline in mean catch were significantly different between cohorts 1 and 2 (0.05 level, t-test). Weakfish were first abundant as new recruits at the river mouth, and moved upriver as they grew. In the fall a reverse migration occurred. Birthdate frequency by station and date indicated that different cohorts used different areas of the York River.

I conducted 6 years of field work to evaluate the habitat use and population dynamics of an experimental release of elk (Cervus elaphus) into Great Smoky Mountains National Park (Park). Elk exhibited relatively small home ranges (female: 10.4 km2 and males: 22.4 km2) and movement distances decreased over time. I calculated survival rates (x = 0.73–0.93) and litter production rates (x = 0.73) for the population. To assess the potential for a long-term elk population, I incorporated those vital rates into the population modeling software Riskman and tested its sensitivity to any given vital rate. The projected population growth was positive (1.03, SD = 0.001) and the probability of extinction in 100 years was minimal (1%, SD = 0.001). However, the model was sensitive to adult female survival, and the simulated annual deaths of only 4 adult females increased the probability of extinction to 45% (SD = 0.021). Compositional analysis detected a strong preference for grassland areas by elk in the Park. I used spatial data to identify potential habitat for elk on a multivariate level by calculating the Mahalanobis distance (D2) statistic based on the relationship between elk locations and 7 landscape variables. The D2 model indicated that the best elk habitat primarily occurred in areas of moderate landscape complexity and edge denisty and gentle slope, and was limited in the Park. At the current small population density, elk had minimal impact on vegetation inside the Park and their diet consisted primarily of graminoids. The elk population at Great Smoky Mountains National Park will likely remain small and vulnerable to extinction for some time due to low growth rates, high environmental stochasticity, and limited habitat. Active management (e.g. predator management, prescribed burning, and mowing) will be required to maintain this population until the population grows to more sustainable levels.

No description available.

No description available.

The purpose of this study was to estimate statewide and local economic impact resulting from snowmobiling activities in Utah to gain a better understanding of preferences and opinions of Utah snowmobilers. The results will provide valuable information for snowmobiling management. The survey instrument was designed to describe trip behavior, snowmobiling-related trip and annual expenditures, level of satisfaction with Utah snowmobiling opportunities, and demographics. A telephone survey was conducted with randomly selected households with registered snowmobiles during the period from April to June 2000. A 54.5% response rate yielded 373 usable completed questionnaires for data analysis. For economic impact analysis, an input-output model was applied using IMPLANTM software using the Utah Cross Industrial Matrix in 1999. From the survey, statewide trip and annual snowmobiling associated expenditures data were estimated. Then output, value added, employment, income, and tax impacts were estimated using IMPLAN. For trip characteristics, level of satisfaction, and demographics, analyses were made using descriptive statistics for quantitative data and content analysis for qualitative data. The results indicate that average household per trip and annual expenditures were $126 and $2,932, respectively. About $53 million of reported expenditures created $34 million in local output impact. Total output impact was largest in the Wasatch Front and Mountain Lands planning districts and smallest in the Southeast and Uintah Basin. These results also indicate that the most popular snowmobiling area, Hardware Ranch, Monte Cristo, and Logan Canyon area in the Bear River planning district, had not necessarily received a large economic gain. The survey participants were moderately satisfied with snowmobiling facilities and services in Utah. However, there were still needed improvements in facilities and services, especially parking space availability and trail grooming.

No description available.

Eucalyptus pellita is a commercially important plantation hardwood species for the humid tropics of north Queensland. This species is favoured by both small-scale growers for use in mixed species woodlots targeting low-volume high-value sawn timber, and also by industrial forest companies growing monocultures for integrated pulp – sawn timber regimes. This study investigated whether mixed-species designs can increase the growth of this tropical eucalypt when compared to monocultures.A replacement series experiment with monocultures of Eucalyptus pellita (E) and Acacia peregrina (A) and mixtures in various proportions (75E:25A, 50E:50A, 25E:75A) was used to examine questions about growth and productivity. The trial was located on the Atherton Tablelands of north Queensland, Australia. High mortality in the establishment phase due to repeated damage by tropical cyclones altered the trial design. Effects of experimental designs on tree growth were estimated using a linear mixed effects model with restricted maximum likelihood analysis (REML). Volume growth of individual eucalypt trees were positively affected by the presence of acacia trees at age five years and this effect generally increased with time up to age 10 years. However, the stand volume and basal area increased with increasing proportions of E. pellita, due to its larger individual tree size. Conventional analysis did not offer convincing support for mixed-species designs. Preliminary individual-based modelling using a modified Hegyi competition index offered a solution and an equation that indicates acacias have positive ecological interactions (facilitation or competitive reduction), and definitely do not cause competition like E. pellita. These results suggest that significantly increased growth rates could be achieved with mixed-species designs over E. pellita monocultures. This statistical methodology could enable a better 4 understanding of species interactions in similarly altered experiments, or undesigned mixed-species plantations.The effects of trees on soils are highly variable and highly site and species specific. That trees can change soil chemistry over time is well established. The soil chemical properties under the eucalypt: acacia experiment were compared to several potential baseline data sources: the reference description of this soil type; those measured at 7 months after planting; and with those of soils under two adjacent vegetation types (forest and pasture) when the experiment was aged 9 years. At 9 years after planting soil total nitrogen increased with increasing proportion of acacias in the treatment. The mean total N under the acacia monoculture was significantly higher (P = 0.041) than that of either the eucalypt monoculture, or the surrounding pasture. The proportion of acacia in the treatment was positively linearly correlated with soil total N (r2 = 0.46; P = 0.018). Soils under the eucalypt monocultures were more similar to those under pasture for a range of soil chemical properties, compared with soils under treatments containing acacias. Results from this site show that the two species alter the soil chemistry in different ways. It is possible that the increased total N under the acacias could be facilitating the growth of the E. pellita, however without n-fixation analysis or tissue sampling it is not possible to confirm that the eucalypt is using the N. Similar cause and effect (or ‘supply and use’) questions also remain for soil pH and available phosphorus changes with increasing acacia in treatment. This study also demonstrates the difficulty in monitoring changes in soil properties over long cycles of forest plantations.The photosynthetic response to light was assessed in the stratified canopy of the mixed species field trial of the eucalypt: acacia experiment, and among commonly planted taxa of E. pellita in glasshouse pot trials. In the field trial photosynthetic capacity of fully5 expanded sun and shade leaves of both species was measured. E. pellita has a wide natural distribution with considerable variation in morphology and growth within the species, with several provenances commonly planted in north Queensland. Photosynthetic capacity and leaf nutrient content of three of these taxa (two from northern occurrences and one from southern occurrences of E. pellita) were measured on two occasions in glasshouse pot trials. A non rectangular hyperbolic function was used to describe the light response curves, and analysis of variance was used to determine differences in the biologically relevant curve parameters between treatments. In the field trial sun and shade leaves of E. pellita produced similar light saturated photosynthetic rates, and experienced little competition for light from the acacia crowns. In contrast there was significant variation in the photosynthetic response between acacia sun and shade leaves. In the glasshouse trials, differences in leaf and petiole morphology were observed, which were coupled with differences in leaf nutrient content and highly significant variation in light saturated photosynthetic rate between the three taxa. This study characterised the light response of E. pellita and suggests that differences in physiological responses to resource availability should be expected among taxa within this species, which may be important for forest productivity models which endeavour to predict tree growth and resource use.An empirical model of growth of E. pellita from a designed monocultures vs. mixedspecies experiment has been used to explore system behaviour rather than predict production of this species from specific forests. This approach has allowed examination of the effect of plantation design on competition, soil nutrient pool change with time and physiological responses to light; leading to a greater understanding of why mixtures can lead to greater productivity than monocultures.

Table Mountain pine is an Appalachian endemic that occurs in a patchy distribution from Georgia to Pennsylvania and is prolific at sites with a history of fire disturbance. The purpose of this dissertation was to reconstruct the fire regimes of Table Mountain pine stands in the Jefferson National Forest, Virginia. Sections from firescarred Table Mountain pines were collected at four sites to analyze fire history, while increment cores and stand composition information were collected from macroplots within each fire history site to investigate the possible influence of fires that were more ecologically severe. Results show that fire was frequent before the fire suppression era, with a Weibull median fire return interval between 2–3 years. The majority of fires occurred during the dormant season and beginning of the early growing season. Two of the four sites had a more even distribution of fire seasons, and these sites also had significant Table Mountain pine regeneration. Cohorts of tree establishment were visible in the fire charts of three of these sites, indicating fires that were likely moderate in severity. The canopy at three of the four sites is currently dominated by Table Mountain pine, but the understory at all sites has large numbers of fire-intolerant hardwoods and shrubs. These Table Mountain pine stands will likely succeed to xeric oak and fireintolerant hardwoods, such as red maple and black gum, in the future. Fire statistics indicate that all four sites currently exist outside their range of historical variation in fire occurrence.