• A Comparison Of The Effects Of Analysis Techniques And Computer Systems In Remote Sensing Technology And A Reference Data Collection Technique

      Spencer, Joellen Page (1981)
      A technique for collecting and recording reference data which considers the spectral and spatial characteristics of Landsat data, the computer system being used, and the gradient nature of wildland vegetation was developed and described. Different analysis techniques for four critical factors affecting the accuracy of computer-aided analysis products were evaluated. Comparisons were made on the basis of accuracy evaluations of two methods of data/analyst interface, three methods of deriving training statistics, three methods of spectral class descriptions, and two levels of map category detail. The primary data set used was digital Landsat multispectral data for a study area around Fairbanks, Alaska. Reference data were developed from field work and photo-interpretation. The training methods compared were supervised, unsupervised, and modified clustering. The three spectral class description methods were: (1) labels derived from the training data; (2) the color display screen; and (3) from ground plot data. Community level cover types were compared with generalized map categories. The effect of post-classification stratification was evaluated. The reference data technique provides geographically located stands and cover types identifications with a flexible coding system that can be aggregated to correspond to the spectral data categories. No difference in classification accuracy was found for an experienced analyst using a printout oriented system such as EDITOR or a screen oriented system such as IDIMS. The modified cluster method of developing training statistics was more effective and efficient than supervised or unsupervised training methods. The use of ground plot data and subsequent stratification improved the descriptions of spectral classes. Generalized mapping categories were more accurate than detailed mapping categories. Knowledge of the ecologic, floristic, and spectral characteristics of the cover types in the study area is necessary to develop spectral class descriptions and stratification criteria.
    • Applied Range Ecology Of Reindeer (Rangifer Tarandus Tarandus) On The Seward Peninsula, Alaska

      Finstad, Gregory Lawrence; Kielland, Knut; Harris, Norman (2008)
      Linking variation of the environment to animal production is key to successful range management. Ecological site descriptions (ESDs) are landscape units used by land managers for the grazing management of domestic reindeer ( Rangifer tarandus tarandus) on the Seward Peninsula, Alaska. This study investigated the appropriateness of using ESDs for the grazing management of reindeer and explored the use of alternate units to link landscape variation to animal production. ESD composition of reindeer ranges varied across the Seward Peninsula, but there was no relationship to either animal production, estimated by June calf weight and cow/calf ratios, or reindeer serum and tissue mineral concentrations. I have shown that reindeer do not graze uniformly across ESDs, but are selective, both temporally and spatially, in what they consume. Reindeer diet selection and animal production appear to be driven by temporal variation in the nutritional characteristics of individual forage species. Biomass production and seasonal nutritional characteristics of forage species were used develop a computerized mapping program for reindeer producers to identify high quality grazing areas. Production among herds was related with identified forage sources of protein in the diet. Reindeer in herds with smaller June calves consumed more catkins, stems and leaf buds of shrubs in May, presumably to compensate for lower protein reserves. Diets of reindeer and June calf weight were significantly predicted by the delta15N ‰ differential between antler core (AC) and antler periosteum (AP). Although animal production was related to landscape stratification at the species level, data showed that weather patterns affected forage nutrient concentration and foraging accessibility at a landscape level. Body weight and growth of female calves and the proportion of yearlings lactating the next summer were positively correlated with spring temperature and negatively correlated with winter severity and summer temperature. Land managers are using ESDs to monitor and assess the impact of grazing, but I have shown that landscape variation described at a multitude of scales other than ESD are linked to grazing patterns and animal production. I concluded that these alternative landscape units be integrated into reindeer range management currently being practiced on the Seward Peninsula.
    • Assessing The Health Of Harbor Seals In Alaska

      Trumble, Stephen John; Castellini, Michael (2003)
      Declining populations of pinnipeds in the Gulf of Alaska, possibly resulting from changes in prey quality, prompted research to determine the population health status of harbor seals (Phoca vitulina) using blood chemistry and digestive constraints. Blood chemistry and morphology reference range values between two harbor seal pup populations in Alaska, one population in continued decline, Prince William Sound, and another in recent increase, Tugidak Island, offered clues that blood values can vary on the population scale and that health assessment must utilize an appropriate set of reference values for valid comparisons. Subsequently, a captive study involving harbor seals yielded changes in ten blood chemistry or hematology values as a function of season and diet. These data provided evidence that populations may have distinct "identities" based on blood chemistry values. The "metabolic identity" of a population provides evidence of the relationship between environmental stressors and the genetic capacity of the animal to respond to metabolic demands. This made it possible to better understand population level differentiation in plasma chemistry values and thus assess the health of animals occupying the outlier regions of populations, since these regions are often suggestive of poor health. A captive study involving harbor seals, which are known to consume the low quality prey (pollock) implicated in the declines of many species of birds and mammals in the Gulf of Alaska, yielded consistent dry matter digestibility resulting in greater gut fill from pollock than from herring. Digestible energy intakes from pollock were greater than from either herring or the mixed diet. Lipid digestibility of herring declined from 90% to 50% when lipid intake exceeded 60 g kg -0.75 d-1. Results of this study imply that a flexible digestive system for harbor seals can compensate for ingesting a prey of low energy density by increasing gut fill and enhancing protein and lipid assimilation, to sustain digestible energy intake. In other words, harbor seals can offset differences in prey quality if prey availability and abundance does not limit the physiological plasticity of their digestive system to maintain their supply of energy and nutrients.
    • Biological impacts and recovery from marine disposal of metal mining waste

      Kline, Edward R. (1998)
      Waste from coastal, metal mining operations may be disposed of in the ocean. Studies were conducted using tailings and wastewater (effluent) from a proposed gold mine that is located near Juneau, Alaska, USA. The ability of invertebrates to colonize tailings after obliteration by submarine tailings disposal (STD) was assessed through a field experiment. Trays of tailings and reference sediment were placed on the sea floor and retrieved over a 22 month period. The taxonomic composition, abundance, and biomass of invertebrates that colonized tailings and reference sediment were similar. Therefore, recolonization of invertebrates after obliteration by STD should not be inhibited by the presence of these tailings as a bottom substrate. In a laboratory study, the toxicity of effluent from the milling process was compared for early life stage fish and crustaceans. Common reference species and species that are indigenous to southern Alaska were exposed to effluent. The relationship between effluent concentration and organism response was established for immobilization, paralysis, and death. For each response, the sensitivity of the reference species bracketed that of the indigenous species. An overall ranking of species sensitivity could not be made because it depended on the response that was compared. The source of effluent toxicity was determined for one of the reference species, a crustacean. A simulated effluent was created to duplicate the ionic composition of the actual effluent. Toxicity was compared in effluent, effluent with increased salinity, simulated effluent, and solutions with adjusted concentrations of ions. Calcium was in excess in the effluent, relative to seawater, and was isolated as the source of toxicity. Sodium deficiency in the effluent, relative to seawater, reduced calcium toxicity.
    • Body Condition And Food Resources Of White-Tailed Deer On Anticosti Island, Quebec

      Huot, Jean (1982)
      A study was conducted on relationships between seasonal variation in body condition of white-tailed deer (Odocoileus virginianus borealis) and food resources on Anticosti Island, Quebec. Results of the vegetation surveys show that food resources are extremely limited in abundance and variety as snow covers the ground vegetation in winter. Excluding Picea spp., Abies balsamea is by far the most available browse species, accounting for approximately 95% of the available browse biomass in February and March. Analysis of rumen contents suggests that this species accounts for 98.5% of the browse eaten by inland deer between February and mid-April. Lichens account for 9.5% of the dry weight of the rumen content at that time. During the snow-free period, forbs dominate the diet. Both sexes and all age classes show a well defined pattern in body composition with maximum fat levels occurring between September and mid-December and minimum levels between mid-April and mid-June. Fat reserves (ether extraction) in fawns vary from a maximum of 15.3% in fall to a minimum of 0.2% in spring as they lose 41% of their ingesta-free body weight. Composition of the winter body weight loss varies according to sex and age, fat represents 31.7% to 58.9% of the loss and protein 17.8% to 23.0%, water is inversely correlated with fat and ash is a minor part of the loss. The caloric content of the weight loss on an ingesta-free weight basis is lowest in 3-year-old males (3.95 kcal/g) and highest in 2-year-old females (6.86 kcal/g). It is concluded that in association with their low productivity in summer, Anticosti deer must base their winter survival strategy primarily on energy conservation and secondarily on food acquisition during that season.
    • Carbon Cycling In Three Mature Black Spruce ( Picea Mariana [Mill.] B.S.P.) Forests In Interior Alaska

      Vogel, Jason Gene; Valentine, David (2004)
      Climate warming in high latitudes is expected to alter the carbon cycle of the boreal forest. Warming will likely increase the rate of organic matter decomposition and microbial respiration. Faster organic matter decomposition should increase plant available nutrients and stimulate plant growth. I examined these predicted relationships between C cycle components in three similar black spruce forests (Picea mariana [Mill] B.S.P) near Fairbanks, Alaska, that differed in soil environment and in-situ decomposition. As predicted, greater in-situ decomposition rates corresponded to greater microbial respiration and black spruce aboveground growth. However root and soil respiration were both greater at the site where decomposition was slowest, indicating greater C allocation to root processes with slower decomposition. It is unclear what environmental factor controls spruce allocation. Low temperature or moisture could cause spruce to increase belowground allocation because slower decomposition leads to low N availability, but foliar N concentration was similar across sites and root N concentration greater at the slow decomposition site. The foliar isotopic composition of 13C indicated soil moisture was lower at the site with greater root and soil respiration. From a literature review of mature black spruce forests, it appears drier (e.g. Alaska) regions of the boreal forest have greater soil respiration because of greater black spruce C allocation belowground. Organic matter characteristics identified with pyrolysis gas chromatography-mass spectrometry correlated with microbial processes, but organic matter chemistry less influenced C and N mineralization than did temperature. Also, differences among sites in C and net N mineralization rates were few and difficult to explain from soil characteristics. Warming had a greater influence on C and N mineralization than the mediatory effect of soil organic matter chemistry. In this study, spruce root C allocation varied more among the three stands than other ecosystem components of C cycling. Spruce root growth most affected the annual C balance by controlling forest floor C accumulation, which was remarkably sensitive to root severing. Predicting the response of black spruce to climate change will require an understanding of how spruce C allocation responds to available moisture and soil temperature.
    • Chemical Defense Of Boreal Woody Plants Against Vertebrate Herbivores (Snowshoe Hare, Defense, Secondary Metabolite)

      Bryant, John Philip (1984)
      Snowshoe hares avoid feeding upon winter-dormant woody plant species, growth stages and parts that contain high concentrations of deterrent secondary plant metabolites. Winter browse that is highly palatable to showshoe hares is also high quality food for these hares: snowshoe hares maintain weight in winter when fed highly palatable browse, but do not maintain weight when fed unpalatable browse. A theory is presented that accounts for the allocation of resources to secondary plant metabolites on both evolutionary and physiological time scales. This theory predicts that: (1) Slowly growing woody plants adapted to growth on nutrient-deficient soils or in deep shade will have more effective constitutive antiherbivore defenses than more rapidly growing woody plants adapted to growth in early stages of succession on fertile soils. (2) Juvenile woody plants will be more strongly selected for antiherbivore defenses than adult woody plants. (3) Ontogenetic variation in the effectiveness of antiherbivore defenses will usually be greater in rapidly growing than slowly growing woody plants. (4) A widespread juvenile reversion of rapidly growing woody plants caused by severe winter hare browsing in the peak phase of the hare cycle is a partial cause of the cycle. Evidence for this theory is presented.
    • Community Structure And Longitudinal Patterns Of Benthic Invertebrates In A Heavy-Metal Contaminated Alaskan River System

      Brown, Barry Neil (1987)
      Community structure of stream invertebrates was investigated in a heavy-metal contaminated watershed in Denali National Park, Alaska. Three sites were located on Stampede Creek, with one station above an antimony mine (active 1916-1970) and two stations below. An additional site was located on the Clearwater Fork of the Toklat River downstream from the Stampede Creek confluence. Quantitative samples of benthic invertebrates and associated coarse ($>$1 mm) detritus were obtained in late June (early spring), late July (summer), and late August (early fall).<p> Gut analyses allowed categorization of insects to functional feeding groups. Water temperatures increased and detrital storage generally decreased downstream. Abundance of shredders was positively correlated with abundance of coarse detritus at the headwater site. Longitudinal changes in functional group composition were consistent with the River Continuum Concept. Heavy metal contamination appeared to affect taxonomic and functional groups differentially. Grazers and predators were severely underrepresented directly downstream from the mine. <p>
    • Comparative foraging ecology and social dynamics of caribou (Rangifer tarandus)

      Post, Eric Stephen; Klein, David R. (1995)
      The Southern Alaska Peninsula Caribou (Rangifer tarandus) Herd (SAPCH) and its two sub-groups were the focus of a study addressing the hypotheses: (1) food limitation during winter caused a decline in the herd; and, (2) higher calf productivity within the Caribou River group than within the Black Hill group was related to greater forage availability on the seasonal ranges of the Caribou River group. Intense, systematic range and calving surveys in 1991 and 1992 supported the hypothesis of food limitation during winter, and indicated that greater calf production in the Caribou River group was related to earlier commencement of the season of plant growth and greater forage availability on the summer range of that group, coupled with earlier parturition among females of the Caribou River herd. In a comparative study involving the two SAPCH groups and the West Greenland Caribou Herd, daily variation in sizes of foraging groups, densities of caribou within feeding sites, distances between individuals within feeding sites, distances moved by foraging groups, and frequency of group movement was modeled using the following ecological parameters: predation risk, insect harassment (by mosquitos), range patchiness, feeding-site patchiness, feeding-site area, and range-wide density of caribou. Models revealed that intraseasonal social dynamics of foraging caribou were governed in most instances by patterns of forage availability and distribution across landscapes and within feeding sites, in some instances by insect harassment and social pressures, but in no instance by levels of predation risk inherent to the ranges on which they foraged. In a study of the interrelationships between characteristics of graminoids and intensity of grazing by caribou, vegetation on each of the Black Hill and Caribou River ranges was sampled and tested for responses to clipping. Biomass density (g/m$\sp3$) of forage, shoot density (#/m$\sp2$), and nutrient and mineral densities (g/m$\sp3$) and concentrations (g/100g tissue) correlated positively with use of sites by caribou. Productivity and responses to clipping were independent of previous use, but consistent within ranges. These results indicate that caribou are sensitive to local variation in forage quantity and quality, and preferentially use sites with higher returns of nutrients and minerals.
    • Constructed Wetlands For Wastewater Treatment In The Subarctic

      Maddux, David Charles; Sparrow, Stephen D. (2002)
      This research had two basic objectives: to assess the capability of macrophytes indigenous to the subarctic in removal of heavy metals from wastewater and to determine the feasibility of using constructed wetlands for sewage wastewater treatment in a subarctic environment with a focus on rural application. The research consisted of two parts: a greenhouse study in which indigenous macrophytes were subjected to heavy metal pollutants similar to those found in roadway runoff and a constructed wetland built to treat sewage wastewater. Five species of plants were tested in both projects: Arctophila fulva, Carex rhynchophysa, Menyanthes trifoliate, Scirpus validus and Typha latifolia . In the greenhouse study, the plants were exposed to four heavy metals: cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) over a 68-day period. The plants were grown under a photoperiod of 20 hours light:4 hours dark. There were significant differences in metal uptake among species and more metals were stored in below-ground plant parts than in above-ground plant parts. In separate experiments, plants took up zinc in greater quantities than the other metals except A. fulva which took up copper in the greatest quantity. Effects of phytotoxicity from the metal concentrations were apparent only in M. trifoliata. The constructed wetland study consisted of a five-cell system. Biological oxygen demand (BOD), total suspended solids (TSS), fecal coliforms (FC), total phosphorus (TP), total Kjeldahl nitrogen (TKN) and ammonium nitrogen (NH4+) were measured bi-weekly during each growing season over a three-year period. Reduction efficiencies, averaged over the ice-free season, ranged from 24--67% for BOD; 38--62% for TSS; 93--99% for FC; 21--60% for TP; 43--76% for TKN; and 50--92% for NH4+. The reduction of pollutants indicated the ability of constructed wetlands to work well in the subarctic. Vegetation colonized the constructed wetland rapidly, with a complex community structure emerging over the study period. Pollutant reduction appeared to be limited by the size of the constructed wetland and not by the extreme climatic conditions.
    • Demographic components of philopatry and nest-site fidelity of Pacific black brant

      Lindberg, Mark Steven; Sedinger, James S. (1996)
      I investigated demographic components of nest-site fidelity and philopatry of Pacific black brant (Branta bernicla nigricans). My analyses included data I collected during summer 1990-1993, and also incorporated data obtained between 1986-1989. My studies of nest-site fidelity were limited to the Tutakoke River colony, Yukon-Kuskokwim River Delta, Alaska. Studies of philopatry and dispersal among colonies included observations at 7 breeding colonies of brant marked with tarsal tags (n = 20,147). I observed strong evidence that philopatry of brant was female biased. Probability of breeding philopatry, which was estimated with multi-state modeling techniques, was high (>0.9) and dispersal of adults among breeding colonies was rare. I developed an ad hoc estimator for natal philopatry that was unbiased by a confounding of homing, survival, and detection probabilities. Probability of natal philopatry for females was both age and density dependent. The density-dependent decline in natal philopatry may result from increased rate of permanent nonbreeding or increased probability of dispersal. Observed probability of natal philopatry for males was approximately equivalent to the relative size of their natal colony, suggesting that males pair at random with females from other colonies. Gene flow among populations of brant is largely male mediated, and I predict populations of brant will exhibit distinct mitochondrial DNAs if populations have been reproductively isolated for an adequate period of time. Probability of fidelity to previous nest sites for adults was high (>0.7). Probability of nest-site fidelity was affected by previous nesting success, age, and availability of nest sites. Phenology of nesting, nest-site selection, and clutch size of brant was affected by spring snowmelt. Dispersal of brant from traditional nest sites in years with late springs may represent a tradeoff between site fidelity and timing of nest initiation. Movement of young females from natal nest sites was a mechanism for colony expansion. I observed little evidence that site fidelity was advantageous, and concluded that quality of individual bird, environmental conditions, and demographic status may be more important determinants of breeding performance.
    • Distribution of large calanoid copepods in relation to physical oceanographic conditions and foraging auklets in the western Aleutian Islands

      Coyle, Kenneth Orval (1997)
      Acoustic measurements and net sampling were used to estimate zooplankton abundance and biomass relative to water mass types and flow fields in the western Aleutian Islands during June and July, 1992 and 1993. Observations are interpreted relative to the distribution and abundance of least auklets (Aethia pusilla), which forage on zooplankton. Highest zooplankton biomass (up to 7 g m$\sp{-3}$) occurred during June 1992, in the pycnocline separating the upper mixed layer from the cold intermediate layer north of a front separating Bering Sea and Alaska Stream water. The large calanoid Neocalanus flemingeri had highest abundance but the larger Neocalanus cristatus accounted for most of the biomass. N. cristatus and N. flemingeri were absent south of the Bering Sea front, where the community was dominated by Neocalanus plumchrus and Eucalanus bungii. Auklets were foraging almost exclusively north of the Bering Sea front. Neocalanus spp. abundance in the upper mixed layer was much lower in July 1993, than in June 1992. Neocalanus occurred primarily in scattered aggregates near the pycnocline over Bering Sea Intermediate water and at the surface in Pacific water. Auklets shifted their foraging activities to passes and shelf areas among the islands, where tidally generated divergences and convergences upwelled and concentrated prey into patches in the mixed layer. Elevated densities of Neocalanus were observed in convergence zones in Delarov Pass and over a ridge south of Kiska Island. Convergence zones were identified by intense sound scattering from entrained bubbles and by deceleration of the horizontal velocity components in acoustic doppler current data, a record of current speed and direction beneath the vessel. Densities of auklet prey in the study area during June were apparently influenced by the position of the front between Bering Sea and Pacific water masses. The position of the front was influenced by Alaska Stream flow anomalies lasting for several years. Prey densities on the shelves and in the passes during July were influenced by tidal currents at spatial scales of tens of meters to ten kilometers and lasting one tidal cycle.
    • Dynamics of nutrient cycling on postharvested white spruce sites in interior Alaska

      Pare, David (1990)
      Various field and laboratory methods were used to characterize nutrient cycling on two mature white spruce sites, one recently harvested site and three 14-year-old harvested white spruce sites colonized by different plant communities and presenting different intensity of soil disturbance. Study sites were chosen on upland south facing sites and presented conditions of reduced environmental variability. Soil analysis showed no changes in pools of soil nutrient unless the forest floor was removed. On the other hand, some differences in the dynamics of nutrients were seen: (1) sites where the forest floor was removed showed low N mineralization rates; (2) N mineralization rates appeared faster in the surface soil of the recently harvested site than in mature white spruce sites; (3) the surface soil of sites regenerating to aspen showed the highest N mineralization rates of all 14-year-old sites. Field soil temperature, and field soil moisture content as well as N and lignin concentrations of the forest floor could not explain the differences in N mineralization rates between sites. This suggests that species colonization may influence N dynamics and that N cycling rate on regenerating sites is controlled by a small pool of rapidly cycling N. The determination of nutrient uptake and return by vegetation growing in the field indicated that nutrient cycling was much faster in 14-year-old aspen stands than on any other regenerating or mature site. The measurement of element availability with ion exchange resin bags indicated an increased leaching of nitrate, phosphate and sulfate at springtime, the second summer following harvesting. Poor correlations were obtained between conventional soil testing and ion exchange resin bag determinations. Comparisons between field and laboratory nutrient availability indices indicated that sites colonized by sprouting aspen exhibited the highest N cycling rates seen in this study. This observation makes aspen an interesting species to consider for mixed species management strategies.
    • Ecological and physiological aspects of caribou activity and responses to aircraft overflights

      Maier, Julie Ann Kitchens (1996)
      I investigated the use of remote-sensing of caribou (Rangifer tarandus) activity to assess disturbance of low-altitude overflights by jet aircraft. Resource management agencies are concerned about the potential effects of these overflights on important species of ungulates. I hypothesized that low-altitude overflights would affect activity and movements of caribou, and thereby constitute a disturbance with negative consequences on energetics. I used caribou of the Delta Herd (DCH) and captive animals at the Large Animal Research Station (LARS) to address the hypotheses: caribou (1) exhibit equal activity day and night; (2) do not time activity to light; and (3) activity patterns do not change seasonally in response to daylength. Caribou were nychthemeral and exhibited uniform activity with no apparent timing to light. DCH caribou responded to seasonal changes in the environment by modifying activity (increased activity in response to insect harassment), whereas LARS caribou altered activity in response to fluctuating physiological variables (increased activity during rut). Changes in daylength did not affect activity. Data on activity from LARS and DCH caribou were compared with extant data on caribou of the Denali and Porcupine herds. Poor quality forage in winter was inferred from long resting bouts, and low availability of forage was inferred from long active bouts of post-calving caribou of the DCH. In midsummer, caribou of the DCH exhibited significantly longer active and shorter resting bouts than did LARS caribou, consistent with a moderate level of insect harassment. Responses of caribou to overflights were mild in late winter and, thus, overflights did not constitute a disturbance. Post-calving caribou responded to overflights by increasing daily activity, linear movements, incremental energy cost, and average daily metabolic rate. Energetic responses and movements were significantly related to the loudest overflight of the day. In the insect season, activity levels increased significantly in response to overflights but with no corresponding increase in linear movements or energetics. My recommendations are to prohibit aircraft overflights of caribou during calving and post-calving periods and during key feeding times in insect harassment seasons. Research indicates the possibility of more severe effects in nutritionally stressed animals.
    • Ecological effects of spawning salmon on several southcentral Alaskan streams

      Piorkowski, Robert Joseph (1995)
      The ecological effects of salmon (Oncorhynchus spp.) carcasses on southcentral Alaskan streams were studied by: (1) observing salmon carcass decomposition and use; (2) comparing the macroinvertebrate community structure of streams receiving different inputs of salmon carcasses; and (3) quantifying the amount of marine-derived nitrogen (MDN) entering stream food webs using stable-isotope analysis. Abiotic mechanisms, such as large woody debris and the slow waters of stream margins and eddies were important in initial retention of salmon carcasses. Once entrained, carcasses decayed rapidly due to intense microbial processing. Stream insects and fishes were observed consuming carcasses, eggs, and smolts. Macroinvertebrate communities in streams receiving runs of salmon or in lake outlet streams were more diverse taxonomically. One functional feeding group, filterers (including net-spinning caddisflies (Hydropsychidae) uncommon in Alaska), increased in relative abundance. Although many other taxa also responded positively to enrichment, some taxa responded negatively. A significant difference existed in $\partial\sp{15}$N values between MDN and terrestrial sources but natural dissolved inorganic nitrogen contributions to stream food webs ($\approx$90-95% of total N) from groundwater generally overwhelmed the marine signal ($\approx$5-10% of total N). $\partial\sp{15}$N values generally suggested that some MDN ($\approx$15% of total N) entered into food webs after its incorporation into algal biomass but values for certain macroinvertebrate taxa (Arctopsyche and Plumiperla), salmon fry (Oncorhynchus spp.) grayling (Thymallus arcticus), rainbow trout (O. mykiss) and American dippers (Cinclus mexicanus) suggest these biota directly consume substantial amounts (40%-90%) of salmon protein. $\partial\sp{15}$N values in individual macroinvertebrate taxa usually cycled seasonally. All three elements of this investigation support the hypothesis that salmon carcasses can be important in structuring aquatic food webs.
    • Ecology of birch litter decomposition and forest floor processes in the Alaskan taiga

      Wagener, Stephen Mitchell (1995)
      Our view of an ecological process is influenced by the scale of our hypotheses and experiments. The forest floor can be examined as a system, where processes that affect ecosystem carbon and nutrient cycling are controlled by macroscale variables (seasonal climatic changes), which in turn affect microscale controls over microbial activity. In the forest floor of Alaskan taiga, annual layers of Equisetum (horsetail) litter demarcate cohorts of birch litter. We collected samples of the forest floor monthly during September 1992, and in June-September 1993. Forest floor material was separated into each of the three most recent litter cohorts, plus the Oe layer, and the Oa layer. Overall, respiration potential decreased with depth of litter (litter age), but showed no change over time. Nitrogen mineralization potential increased with depth, and fluctuated over time. Microbial biomass did not vary with depth, but did increase greatly in September in conjunction with increased litter moisture. Litter C:N ratio decreased with time and varied with depth according to the year-to-year variation in litter quality. Our hypothesis that microbial activity on a particular litter cohort is a function of the litter quality, the vertical position of the litter in the forest floor, and the timing of the observation within seasonal macroclimatic cycles was supported. The distribution of some taxa of soil fauna correlated with depth. In these cases, the fauna were likely constrained mostly by differences in the microclimate of the forest floor strata. Other soil fauna varied over time, likely in response to differences in the microbial community. Yet other faunal distributions showed an interaction between depth and time, apparently responding to a combination of changes in microclimate and changes in food availability. The creatures that live in water pores may also have responded to an increase in habitat space as the top-most litter strata became wetter. "Cascading" microcosms containing material from these forest floor strata showed a temporary suppression of respiration by leachates from the newer litter on underlying forest floor material. Traditional litterbag techniques were also used to show changes in nitrogen that indicate winter microbial activity.
    • Ecology Of Reindeer On Hagemeister Island, Alaska

      Stimmelmayr, Raphaela (1994)
      The objective of this study was to investigate and characterize the factors driving the Hagemeister Island reindeer population. A total of 144 reindeer were introduced to Hagemeister Island in 1965 and 1967. The herd initially increased in size to about 1,000 head and then fluctuated around 800 animals. In 1991-1992, a moderate winter die-off of primarily adult bulls ($>$90%) occurred. Adverse snow conditions and poor post rut conditions of bulls appeared to have facilitated the die-off. No conclusive evidence was found that the herd experienced effects of density-dependent food limitation despite poor winter lichen range. In 1993, conception was documented in calves and overall pregnancy rate was approximately 70%. Body size and condition was comparable to other arctic island reindeer herds. This suggests that reindeer on Hagemeister Island do not solely depend on lichen during winter but utilize other forages. <p>