Digital Commons Network^™

Unraveling The Mystery Of Leaf Reddening In Seagrasses, Alyssa B. Novak

Doctoral Dissertations

Seagrass meadows around the world are declining due to natural and anthropogenic stressors, including global climate change. Recently, more attention has been given to identifying responses that offer resistance to stressors so that researchers can better manage seagrasses for resilience to environmental change. Leaf reddening, the expression of red coloration in leaves, is a well-documented response in terrestrial plants that has been shown to increase resilience to stress, but has been poorly understood in seagrasses. To increase our understanding of the prevalence, causes, and function of leaf in seagrasses, surveys were conducted in the world's six seagrass bioregions and a …

Assessing Social-Ecological Resilience And Adaptive Capacity In The Face Of Climate Change: An Examination Of Three Communities In The Crown Of The Continent Ecosystem, Bradley B. Johnson

Doctoral Dissertations

This research examines the social-ecological resilience and adaptive capacity of the Crown of the Continent Ecosystem through a suite of three case study communities and the impacts of climate change on the ecosystem's hydrologic regime. The Crown of the Continent Ecosystem spans the U.S.-Canadian border; case study communities composed of Kalispell and Choteau, Montana and Fernie, British Columbia fall on both sides of the border.

Primary data was gathered through a "bottom-up" qualitative approach utilizing an online survey followed by a semi-structured interview process with stakeholders in natural resource dependant industries and government at the local, state, and federal levels …

Detection Of Mortality In Tropical Forests Using Remote Sensing: From Treefall Gaps To Large Disturbances, Fernando Del Bon Espirito-Santo

Doctoral Dissertations

The frequency, severity, and intensity of natural disturbances in tropical forests continually re-shape forest structure. At small scale, branch or tree-falls gaps and subsequent recovery are important mechanisms for carbon cycling. At landscape scale, large disturbances (blow-downs) may also play a role on the structure and composition of tropical forests. Quantitative studies of natural disturbances across the occurrence spectrum (branch fall-gaps to blow-downs) are rare for the Amazon. Remote sensing coupled with intense field work data collection provides the means to analyze the dynamic of tropical forests at multiple scales. In this dissertation three aspects of natural disturbances were examined: …

Seasonal, Biogeochemical, And Microbial Response Of Soils To Simultaneous Warming And Nitrogen Additions, Alexandra R. Contosta

Doctoral Dissertations

Climate warming and nitrogen deposition are global environmental threats that could alter soil microbial communities and the biogeochemical processes they perform. Few studies have examined interactive effects of elevated temperatures and nitrogen inputs. Many studies have also not considered the role that season plays in mediating the response of soils to warming and nitrogen. Finally, most research has not linked changes in the soil microbial community with ecosystem-scale dynamics. One objective of this dissertation was to examine season-specific microbial and biogeochemical responses to simultaneous warming and nitrogen additions. Another aim was to investigate whether warming and nitrogen can restructure microbial …

Assessing Relationships Of Moose Populations, Winter Ticks, And Forest Regeneration In Northern New Hampshire, Daniel Henry Bergeron

Master's Theses and Capstones

This study examined relationships among winter ticks, weather, and the nutritional and reproductive status of moose, and the impact of moose on regeneration of commercial forests in northern New Hampshire. Three methods were evaluated to assess their usefulness as indices of relative winter tick abundance, and predictors of tick epizootics: tick counts on harvested moose and roadside, spring hair-loss surveys were considered time and cost effective to index winter tick abundance. Physical characteristics of harvested moose (1988--2009) indicated ovulation rates (∼20%), and mean body weight (<200 kg) of yearlings declined since 1988; because adult body weight and ovulation rates remained stable, habitat quality was unlikely related. Winter tick epizootics are likely influenced by abnormal large scale weather events, as evident in the widespread die-off in 2002 associated with warm snowless conditions into mid-December 2001 that extended tick transmission to moose. Spring and fall weather should be monitored for unusual conditions causing high tick abundance and tick loads, particularly warm and snowless conditions in April and December. Mean stocking rate of all age classes of commercial tree species was above the threshold in all regions (49--87%); forest regeneration was not considered a regional problem at any moose density.

Interactions Between Adaptive Mutations In The Environment And The Consequences For Adaptation In Escherichia Coli, Kenneth Mark Flynn

Master's Theses and Capstones

Phenotypic plasticity, epistasis or both are expected to influence the adaptive value of mutations and, by extension, how organisms adapt to new environments. We investigated interactions among five mutations that arose and fixed in a laboratory-evolved population of E. coli in a variety of different external environments. Overall, we found that positive pleiotropy tended to be positive rather than antagonistic and that epistatic interactions were common regardless of the external environment. The nature of the epistatic interactions depended strongly on the external environment and altered which adaptive paths were selectively accessible. Ultimately, achieving high fitness in a new environment was …

The Effects Of Historic Earthen Barriers On Northern New England Tital Marshes, Jordan W. Mora

Master's Theses and Capstones

Berms, defined as historic earthen barriers, represent one type of hydrological modification introduced by humans in the tidal marshes of northern New England. Three different research approaches were applied to study the impact of berms on various tidal marsh dynamics. The descriptive study shows that restricted flooding from berm interference can result in significantly altered physical gradients in addition to landward subsidence and pool development. The results from the transplant experiment indicate that the altered landward structure affects the relative importance of biological interactions, namely herbivory, in controlling plant species distribution. The predictive GIS analyses illustrate the location of 34 …

The Spatial And Temporal Distribution, Population Growth Strategies And Options For The Removal Of The Invasive Shore Crab Carcinus Maenas In Two New Hampshire Estuaries, Beth Allison Fulton

Master's Theses and Capstones

The spatial and temporal distribution of the green crab, Carcinus maenas, along with various green crab population parameters, were studied in two New Hampshire estuaries over a one-year period from November 2009 to October 2010. Results show that foraging activity in Great Bay Estuary peaked in December and March, and in HSE, in April and November. Crabs in both estuaries experienced synchronous breeding periods. Males experienced two molts per year in April and November, while females molted synchronously in June. Embryogenesis was accomplished within the month of June. Minimum size at maturity for females in New Hampshire was larger than …

Herbage Mass Accumulation In An Intensive Rotational Grazing System At Unh's Organic Dairy Research Facility, Ashley Green

Master's Theses and Capstones

Pasture-based animal management in the Northeast U.S. relies on the ability to efficiently estimate pasture production and animal intake. Accuracy and precision of a rising plate meter, NDVI meter, and height measurements for estimating pasture biomass were compared relative to hand-clipped samples. Pasture measurements were used to describe biomass accumulation, lactating dairy herd intakes, and re-growth patterns for intensively rotated pastures. Pastures were measured from May-September, 2009 at the UNH Organic Dairy Research Facility in Lee, NH. The rising plate meter provided the most robust estimates of biomass (R²=0.58, SEE=2.73). Forty-seven paddocks were measured for 82 total grazing events; grazing …