Geology topics

Thomas A. Hanley

Publications and source records attributed to Thomas A. Hanley.

4 recordsLinked to original sources

USGS2011

Evidence and implications of recent and projected climate change in Alaska's forest ecosystems

The structure and function of Alaska's forests have changed significantly in response to a changing climate, including alterations in species composition and climate feedbacks (e.g., carbon, radiation budgets) that have important regional societal consequences and human feedbacks to forest ecosystems. In this paper we present the first comprehensive synthesis of climate-change impacts on all forested ecosystems of Alaska, highlighting changes in the most critical biophysical factors of each region. We developed a conceptual framework describing climate drivers, biophysical factors and types of change to illustrate how the biophysical and social subsystems of Alaskan forests interact and respond directly and indirectly to a changing climate. We then identify the regional and global implications to the climate system and associated socio-economic impacts, as presented in the current literature. Projections of temperature and precipitation suggest wildfire will continue to be the dominant biophysical factor in the Interior-boreal forest, leading to shifts from conifer- to deciduous-dominated forests. Based on existing research, projected increases in temperature in the Southcentral- and Kenai-boreal forests will likely increase the frequency and severity of insect outbreaks and associated wildfires, and increase the probability of establishment by invasive plant species. In the Coastal-temperate forest region snow and ice is regarded as the dominant biophysical factor. With continued warming, hydrologic changes related to more rapidly melting glaciers and rising elevation of the winter snowline will alter discharge in many rivers, which will have important consequences for terrestrial and marine ecosystem productivity. These climate-related changes will affect plant species distribution and wildlife habitat, which have regional societal consequences, and trace-gas emissions and radiation budgets, which are globally important. Our conceptual framework facilitates assessment of current and future consequences of a changing climate, emphasizes regional differences in biophysical factors, and points to linkages that may exist but that currently lack supporting research. The framework also serves as a visual tool for resource managers and policy makers to develop regional and global management strategies and to inform policies related to climate mitigation and adaptation.

Alaska↗

USGS2000

Effect of hibernation and reproductive status on body mass and condition of coastal brown bears

We investigated the effect of hibernation and reproductive status on changes in body mass and composition of adult female brown bears (Ursus arctos) on the Kenai Peninsula, Alaska. This information is fundamental to understanding nutritional ecology of wild brown bear populations. Six adult females handled in the fall and following spring (paired samples) lost 73 ± 22 kg (x̄ ± SD; 32 ± 10%) of fall body mass over 208 ± 19 days. Of this mass loss, 56 ± 22% (55 ± 22 kg) was lipid and 44 ± 22% (43 ± 21 kg) was lean body mass. Catabolism of lipid stores accounted for 88.4 ± 8.1% of the body energy used to meet maintenance demands. Overwinter differences in body composition of adult females assessed only once in either the fall (n = 21) or spring (n = 32) were similar to those of paired samples. Relative fatness of bears entering the den was positively related to the contribution of fat (%) to body mass (P < 0.01) and body energy (P < 0.01) losses during hibernation. Thus, relative fatness at the onset of fasting influences the relative proportion of lipid stores and lean body mass catabolized to meet protein and energy demands during hibernation. In the spring, lone females had greater body and lean masses than females with cubs of the year or yearlings. Lipid content was greatest in lone females in the fall. Studies using body mass and composition as indices of population health should consider season or reproductive class.

Journal of Wildlife Management↗

USGS1999

Role of brown bears ( Ursus arctos ) in the flow of marine nitrogen into a terrestrial ecosystem

We quantified the amount, spatial distribution, and importance of salmon ( Oncorhynchus spp.)-derived nitrogen (N) by brown bears ( Ursus arctos ) on the Kenai Peninsula, Alaska. We tested and confirmed the hypothesis that the stable isotope signature (δ 15 N) of N in foliage of white spruce ( Picea glauca ) was inversely proportional to the distance from salmon-spawning streams ( r =–0.99 and P <0.05 in two separate watersheds). Locations of radio-collared brown bears, relative to their distance from a stream, were highly correlated with δ 15 N depletion of foliage across the same gradient ( r =–0.98 and –0.96 and P <0.05 in the same two separate watersheds). Mean rates of redistribution of salmon-derived N by adult female brown bears were 37.2±2.9 kg/year per bear (range 23.1–56.3), of which 96% (35.7±2.7 kg/year per bear) was excreted in urine, 3% (1.1±0.1 kg/year per bear) was excreted in feces, and <1% (0.3± 0.1 kg/year per bear) was retained in the body. On an area basis, salmon-N redistribution rates were as high as 5.1±0.7 mg/m 2 per year per bear within 500 m of the stream but dropped off greatly with increasing distance. We estimated that 15.5–17.8% of the total N in spruce foliage within 500 m of the stream was derived from salmon. Of that, bears had distributed 83–84%. Thus, brown bears can be an important vector of salmon-derived N into riparian ecosystems, but their effects are highly variable spatially and a function of bear density.

Alaska↗

USGS1999

Effect of seasonal differences in dietary meat intake on changes in body mass and composition in wild and captive brown bears

The influence of seasonal dietary meat intake on changes in body mass and composition in wild and captive brown bears ( Ursus arctos ) was investigated because the importance and availability of meat to brown bear populations is currently an important management consideration in several North American ecosystems. Adult female brown bears on the Kenai Peninsula, Alaska, utilized meat heavily in both spring and fall. Meat accounted for 76.2 ± 26.0% (mean ± 1 SD; primarily moose carrion and calves) of assimilated carbon and nitrogen in the spring and 80.4 ± 22.2% (primarily salmon) in the fall. Mass increases in the spring (71.8 ± 28.2%) were mostly lean body mass, but increases in the fall (81.0 ± 19.5%) were primarily fat. Daily intake by captive brown bears fed meat ad libitum during 12-day trials was positively related to body mass. Mass change was positively related to intake in both seasons, but the composition of the gain varied by season, with spring gains primarily lean body mass (64.2 ± 9.4%), while fall gains were 78.8 ± 19.6% lipid. Absolute rates of gain by wild bears occasionally equaled, but were usually much less than, those of captive bears. This was likely due to a combination of factors, which included the time required to locate and handle meat resources, the limited availability of or access to meat resources, and (or) the duration of meat resource availability. Estimated intake by bears not feeding selectively on high-energy components of moose and salmon were 8.5 ± 1.5 kg/day and 541 ± 156 kg/year and 10.8 ± 4.6 kg/day and 1003 ± 489 kg/year, respectively. Intake would drop by as much as 58% for bears feeding exclusively on salmon roe. Management strategies for areas with brown bears that consume significant amounts of meat should address the perpetuation and availability of these meat resources.

Alaska↗