Search

Managers need information about the vulnerability of historical plant communities, and their potential future conditions, to respond appropriately to landscape change driven by global climate change. We model the climate envelopes of plant communities on the Kenai Peninsula in Southcentral Alaska and forecast to 2020, 2050, and 2080. We assess 6 model outputs representing downscaled climate data from 3 global climate model outputs and 2 representative concentration pathways. We use two lines of evidence, model convergence and empirically measured rates of change, to identify the following plausible ecological trajectories for the peninsula: (1.) alpine tundra and sub-alpine shrub decrease, (2.) perennial snow and ice decrease, (3.) forests remain on the Kenai Lowlands, (4.) the contiguous white-Lutz-Sitka spruce complex declines, and (5.) mixed conifer afforestation occurs along the Gulf of Alaska coast. We suggest that converging models in the context of other lines of evidence is a viable approach to increase certainty for adaptation planning. Extremely dynamic areas with multiple outcomes (i.e., disagreement) among models represent ecological risk, but may also represent opportunities for facilitated adaptation and other managerial approaches to help tip the balance one way or another. By reducing uncertainty, this eclectic approach can be used to inform expectations about the future. [ABSTRACT FROM AUTHOR]

Rapidly changing environmental conditions are influencing distributions of wildlife species in Alaska. Due to strict physiological requirements, the distribution of American martens (Martes americana) is theorized to be driven by changing habitat, climate, and other anthropogenic conditions. We aimed to quantify marten distributions on the Kenai Peninsula, Alaska, and compared historic and contemporary occurrence records. To illustrate changing distribution patterns, we developed predictive niche models for 2 decades and investigated patterns by relating environmental trends with predicted distributions. Museum and trapping records, supplemented by aerial videography detections for martens on the Kenai over the past century, served to train Random Forests based niche models for 1988-2001 and 2002-2010. Change-detection analyses revealed an ongoing westward expansion of likely marten distribution on the Kenai Peninsula since at least 1988, and historic records indicated longer-term growth. Top predictors in the models included soil ecotype, landcover, distance to trails, and distance to recreation sites. Our research suggests that on the Kenai Peninsula, marten distribution is responding to a combination of landscape and climate effects that have contributed to expanding marten distributions over the past century. [ABSTRACT FROM AUTHOR]

Comprehension of basic stream ecosystem function relies on an understanding of aquatic-terrestrial linkages. One major component of such linkages is the incorporation of landscape-derived energy and nutrients into the aquatic food web via microbes. In many boreal streams, wetlands and alder are known to be primary sources of dissolved organic carbon (DOC) and dissolved inorganic nitrogen (DIN), respectively. To simulate the influence of the highly labile portion of wetland-derived DOC subsidies on microbial production and ecosystem processes in a stream with high landscape-derived nutrient inputs, we enriched a boreal headwater stream situated in a high-alder, low-wetland cover catchment (i.e., high DIN, low DOC) with low levels (~0.25 mg/L) of labile DOC (as acetate-C) for 9 weeks. We compared nutrient uptake, bacterial biomass production, and photosynthesis of periphyton and ecosystem metabolism in physicochemically similar upstream (reference) and downstream (treatment) reaches. DIN uptake was greater in the treatment than in reference reach on six out of nine dates during the dosing period. Bacterial biomass production positively responded to C enrichment. Ecosystem respiration increased up to ~50% after dosing began. Gross primary production responded positively to DOC enrichment early in the study when riparian vegetation did not limit light availability, but negatively later on in the growing season. We conclude that even low levels of labile DOC may act as a strong subsidy to headwater stream ecosystems, particularly those with high levels of DIN inputs from alder. Headwater streams influenced by high contributions of both alder and wetlands may represent biogeochemical hotspots, and these landscape features should be viewed as vital and complementary in their roles for ecosystem function. [ABSTRACT FROM AUTHOR]

Headwater streams are the most numerous in terms of both number and length in the conterminous United States and play important roles as spawning and rearing grounds for numerous species of anadromous fish. Stream temperature is a controlling variable for many physical, chemical, and biological processes and plays a critical role in the overall health and integrity of a stream. We investigated the controls on stream temperature in salmon-bearing headwater streams in two common hydrogeologic settings on the Kenai Peninsula, Alaska: (1) drainage-ways, which are low-gradient streams that flow through broad valleys; and (2) discharge-slopes, which are high gradient streams that flow through narrow valleys. We hypothesize local geomorphology strongly influences surface-water and groundwater interactions, which control streamflow at the network scale and stream temperatures at the reach scale. The results of this study showed significant differences in stream temperatures between the two hydrogeologic settings. Observed stream temperatures were higher in drainage-way sites than in discharge-slope sites, and showed strong correlations as a continuous function with the calculated topographic metric flow-weighted slope. Additionally, modeling results indicated the potential for groundwater discharge to moderate stream temperature is not equal between the two hydrogeologic settings, with groundwater having a greater moderating effect on stream temperature at the drainage-way sites. [ABSTRACT FROM AUTHOR]