The boreal forest is a carbon reservoir containing roughly 40% of the world's reactive soil carbon, which is mainly cycled by wildland fires. Climate warming in boreal Alaska has changed the wildfire regime such that an increase in broadleaf forest relative to conifer forest is likely, which may reduce landscape flammability. However, the current and future flammability of broadleaf forest in a warming climate is not well understood. We used pre-fire and post-fire geospatial data to investigate the flammability of upland boreal forest patches in Interior Alaska in relation to summer weather conditions. Our objectives were to assess burning of broadleaf forest patches during "Normal" vs. "Large Fire Years", by week within a fire season, and by topographic position. Using 30-meter land-cover and fire-severity grids, we estimated the flammability of upland broadleaf forest patches during Large and Normal Fire Years. We then tested for topographic effects using a solar radiation index to eliminate potential deviations within the vegetation. Finally, Moderate Resolution Imaging Spectroradiometer (MODIS) hotspots were used to track the spatial extent of burns during the fire season by examining the periods of fire activity and intensity. Flammability of broadleaf forest patches varied both in time and space. Even during Normal Fire Years, broadleaf forest patches exhibited substantial flammability, with a mean of over 50% patch area burned. Patch flammability was significantly higher during Large Fire Years. Burning of broadleaf patches varied with topographic position and correlated with potential insolation. Broadleaf forest patches burned most frequently in late June-early July. Contrary to "conventional wisdom", broadleaf forest patches in boreal Alaska are susceptible to burning even during Normal Fire Years. With climate warming, the flammability of broadleaf forest is likely to increase due to more extreme fire weather events. Thus, although the frequency of broadleaf forest patches on the landscape is likely to increase with more frequent and severe wildfires, their effectiveness as a fire break may decrease in the future.

The objective of this study was to identify a rapid laboratory technique to predict potentially mineralizable organic N for subarctic Alaska soils. Soil samples were taken from major agricultural area of subarctic Alaska. Laboratory incubation followed by kinetic model fit was first used to select a best model to estimate potential soil N mineralization. By correlating the model estimated organic N pool sizes and different chemical extracted organic N, I then found the best chemical method to estimate soil potentially mineralizable N. Spectroscopic properties of water extractable organic matter were also determined and correlated with model estimated organic N pool sizes in order to improve the estimation of soil mineralizable N pool. Finally, the best chemical method and spectroscopic property were used in the selected best kinetic model for the prediction of soil N mineralization in field incubation. Model comparisons showed that models with fixed rate constants were better than that the ones with rate constants estimated from simulation. Among models with fixed rate constants, fixed double exponential model was best. This model differentiated active mineralizable organic N pool with a fixed rate constant of 0.693 week-1 and slow mineralizable organic N pool with a fixed rate constant of 0.051 week-1. By correlating model estimated organic N pool size and chemical extracted organic N amount, I found that the potentially mineralizable organic N size was closely correlated with hot (80 �C) water extractable organic N or 1 M NaOH hydrolysable organic N. By correlating model estimated organic N size and spectroscopic characteristics of water extractable organic matter, I found that the active mineralizable organic N pool was correlated with humification index in cold (22 �C) water extraction (R 2=0.89, p<0.05), which indicates that characterizing extracted organic matter was a useful tool to improve the estimation of soil organic N pools. In summary, potential mineralizable organic N in soils from subarctic Alaska can be estimated by hot water extractable organic matter or 1 M NaOH hydrolysable organic N, which accounted for 70% and 63% of the variation in potentially mineralizable organic N, respectively. This approach will provide fundamental insight for farmers to manage N fertilizer application in agricultural land and also provide some basic information for ecologists on predicting N release from Alaska soil that can be used for assessing the N impact on ecosystem.

It is estimated that the globe must produce 100% more food in the next 50 years to meet growing demand while addressing the compounding challenge of climate change. One potential solution to this challenge is to produce more on existing agricultural lands and put more land into production. The extremely cold and dry climate that characterizes much of Alaska has all but removed the state from the state and national discussions of agricultural production and development. Yet despite this apparent incompatibility with traditional agricultural models, some of the largest wild herds of grazing ungulates are indigenous to Alaska - and thriving. This is both a testament to the resilience of grazing systems in general as well as a statement to the suitability of grazing systems specifically for Alaska. To shift the paradigm towards ecological and economic sustainability, we need to develop sustainable agricultural strategies that are specific to this unique ecosystem. A two-fold approach was used in this body of research: Is there an indigenous livestock species that could be economically feasible enterprise option? Is there a grazing management regime for subarctic Alaska that would improve ecosystem services and optimize pasture resources? I conducted an economic feasibility study of farming muskoxen (Ovibos moschatus), a uniquely adapted Arctic ungulate, to address the first question. An enterprise budget was used to estimate the fixed and variable costs and to model different revenue scenarios using six different combinations of qiviut, sold as raw fiber or value added yarn, and livestock sales to estimate the total economic potential of farming muskoxen at two scales, 36 and 72 muskoxen. Farming muskoxen was economically sustainable under several revenue scenarios. The most profitable scenario for either herd size was selling all the qiviut as value added yarn coupled with livestock sales. The enterprise was profitable at either scale assuming all the yarn sold at full retail price. If no livestock were sold, selling the total qiviut harvest as yarn was the only profitable option. When selling raw fiber alone, the break-even point was at a herd size of 124 muskoxen. Economies of scale accounted for a decrease in costs of approximately 21% overall, 30% in labor, and 23% in herd health, as the herd doubled in size. To address the need for grazing management strategies that are both environmentally and economically sustainable in Alaska, I conducted a study to evaluate the potential of intensively managed rotational grazing (IMRG) regimes on sub-arctic pasture. This regime is designed to mimic the short but intense grazing of wild, migratory ungulates that could enhance ecosystem function while optimizing pasture usage and forage growth. I conducted simulated grazing, applied using IMRG methodology, to evaluate above and below ground response to an IMRG regime and to gain insight on the role of grazing disturbance mechanisms on sub-arctic soil and plant health. A full factorial experiment of muskox dung/urine deposition (M), simulated trampling (T), and herbivory (H) (forage clipping), mimicking IMRG timing and intensity, was conducted at the Large Animal Research Station (LARS), UAF. I used a randomized block design with 96-1 m² plots in two established pastures with different soil types, over the 2014 and 2015 grazing seasons. I documented a treatment effect on soil parameters, forage growth, and percentage of bare soil (p<0.05). Soil nitrogen cycling and the Haney Soil Health Index both increased in plots that received a combination M and T or MT and H. The forage yield was consistently increased by MH, MTH, and H treatments. Although the MT and T treatments had a negative impact on forage yield, they had the largest reduction in the amount of bare ground. The data from this simulated study suggest that theories that underpin the IMRG method are potentially useful to producers, in the unique Alaskan subarctic environment.

A collection of essays is presented that are a contribution toward a biology of eelgrass (Zostera marina L.) in Alaska. Eelgrass is the most abundant seagrass on the coast of Alaska. The distribution of the plant in Alaska is disjunct and extends from Kotzebue Sound to the southern border of the state. The present circumboreal distribution is thought to be the result of dispersal from a west Pacific origin around the Pacific rim and through the Arctic into the Atlantic. Ten widely scattered eelgrass populations in Alaska have been sampled for quantitative comparison. The highest standing stocks (1510 g dry wt/m²) were found in Kinzarof and Izembek lagoons on the Alaska Peninsula. The caloric content, chlorophyll a concentration, turion density, and leaf size varied greatly among the populations. The eelgrass in Safety Lagoon survives the arctic winter under one meter of sea ice in conditions of extremely low light intensity and anoxic water. In chemical composition, eelgrass is similar to other angiosperms, but it also reflects adaptation to the marine environment. Trace elements are accumulated in the plant in proportion to their concentration in the sea. The roots as well as the leaves function as the sites for the uptake of phosphate. Using radioactive phosphate it was shown that phosphate was absorbed greatest in the light and transported throughout the plant; a portion of the phosphate removed from solution by the roots was lost across the leaves. The metabolism of eelgrass in the dark is extremely dependent on temperature. Physiological differences exist between shallow water and deep water plants and between summer and winter plants. A depressed rate of respiration in winter is an adaptation enhancing survival in high latitudes.

The dioecious, neotropical plant species Clusia grandiflora produces two major pools of secondary metabolites, latex and floral resin. Latex serves as a defense against herbivory and floral resin as a pollinator reward. This reward is gathered by bees who use it as a nest construction material. Nuclear magnetic resonance and mass spectral studies show that C. grandiflora latex and resin share two classes of compounds, poly-isoprenylated benzophenones and tocotrienoic acids as major or minor components. The close chemical correspondence between latex and resin indicate that they are evolutionarily related. Though the tocotrienes were not found to have biological activity, benzophenones with potent bactericidal activity were isolated from both latex and resin. Bioassays show that these compounds are especially toxic to the honeybee pathogens Paenibacillus larvae and P. alvei. In pollinator reward resin, bioactive benzophenones are major components, whereas in latex they are minor components. Since latex is ancestral to resin in Clusia, it appears that the pollinator reward system may have arisen from the defensive system through modification of latex-producing tissues in the flower. Subsequent selective pressure from bee pollinators, who benefited from bactericidal activity in the reward, caused resin chemistry to diverge from its latex-like ancestral form. This selection has resulted in the high levels of activity observed in modern resin. In populations of C. grandifora growing in southeastern Venezuela, male and female resins exhibit a pronounced dimorphism in chemical makeup. Female resin possesses a single benophenone and male resin numerous benzophenones. Female resin is more bioactive and hardens quickly; male resin remains pliable for weeks. Female resin composition more closely resembles modern latex than does male resin. Assuming that latex has not evolved substantially since the point at which resin and latex diverged, it appears that male resin has undergone more extensive evolutionary modification than female, a result of selection for progressively earlier flowering times and of necessity a lower viscosity resin reward. The research presented here provides the first detailed chemical evidence of a functional switch in secondary metabolite pathway from the production of defensive compounds to the production of a pollinator reward.