Thesis Defense

Title:

Resource limitation of autotrophs and hetereotrophs in boreal headwater streams

Life Science Hour Seminar

Title:

Strontium isotopes within multi-isotope approaches to ecological and paleoecological research: A case study tracking the movement and feeding ecology of a 17,000-year-old woolly mammoth

Abstract:

There has been an exponential increase in applications of stable isotope ratios of carbon, nitrogen and oxygen in ecological and paleoecological research. More recent advances have included isotopic analyses of individual compounds, such as fatty acids and amino acids. Some researchers consider that we are now entering a ‘golden age’ of applying strontium isotope ratios alongside these more 'traditional' light isotope approaches within isotope ecology. I will present a case study employing strontium isotopes within a multi-isotope approach to examine the feeding ecology and movement of an ancient woolly mammoth (Mammuthus primigenius) from Arctic Alaska. Alaska is experiencing rapid environmental changes in response to recent warming. Radical environmental changes also occurred during and after the last glacial maximum (LGM, ~21,000 years ago). During the LGM, this region was inhabited by a variety of now extinct megafauna, including the iconic woolly mammoth. What caused the extinctions of these ice-age megafauna is still hotly debated. Although the life of mammoths has sometimes been portrayed as including large seasonal migrations, this inference remains untested and is based on the behavior of extant proboscideans rather than on paleo-data. To gain insight into the life history of a mammoth from the Arctic, we longitudinally split the curved, 1.5-meter-long tusk of a bull mammoth using a band saw. The specimen is one of two tusks associated with a skull from a single individual found north of the Brooks Range above the Arctic Circle. Calibrated radiocarbon dates from both the skull and one of the tusks indicate this bull mammoth died 17,000 calendar years ago during the closing millennium of the LGM in this part of the Arctic. After sectioning the tusk to reveal annual growth bands, we used sequential samples taken from along the entire length of the exposed inner surface of the tusk for stable isotope analyses (N and C on the organic fraction and C and O on the inorganic fraction) as well as strontium isotope ratio (Sr 87 /Sr 86 ) analysis in order to reconstruct the animal’s feeding ecology, environment, as well as its movements through the course of its life. This temporally precise, multi-isotope reconstruction is providing insight into the life history of a woolly mammoth between birth and death, including its diet, changing nutritional state, and geographic movement. Based on histological and seasonal isotopic oscillations, we estimate this mammoth was ca. 30 years old when it died and that he wandered extensively during several, multi-year periods of his life. Death seems to have followed an extended period of starvation. I will close by briefly providing examples of the wide array of other applications of strontium isotopes in ecological and paleoecological research – food for thought.

Life Science Hour Seminar

Title:

The enemy within: Impacts of the aspen leaf miner in interior Alaska

Abstract:

Patterns of insect attack on forest trees in Alaska are changing. Several large-scale outbreaks of herbivorous insects have arisen in the past 20 years, causing severe vegetation damage. Understanding how insects impact forest tree performance and physiology, and how these effects interact with changes in climate, is critical to predicting future changes to the ecology of the boreal forest. One of the most dramatic examples of insect disturbance in recent years is the persistent and widespread outbreak of the aspen leaf miner (Phyllocnistis populiella), which arose around year 2000 and has caused conspicuous damage to aspen within Alaska and NW Canada nearly every year since. In this talk I will review several factors that may contribute to the prolonged nature of the outbreak, including the behavior of the insect and the life history of both insect and plant, and detail the impacts of leaf mining damage to aspen growth and physiology. The aspen leaf miner has an unusual mode of feeding that destroys cells of a single leaf tissue: the epidermis. At a leaf level, epidermal mining both depresses photosynthesis by impairing the function of stomata and increases foliar water loss by compromising the integrity of the leaf cuticle. At a tree level, these physiological effects lead to reduced growth and dieback of aspen trees. Over larger spatial and temporal scales, remotely sensed measurements of productivity are negatively associated with average leaf mining intensity across years. Tree ring studies from our study sites and elsewhere in Alaska show that the negative impacts of leaf mining are intensified by low water availability and high evaporative demand. Taken together, the results underscore the importance of insect outbreaks and their interaction with climate to understanding the changing boreal forest.

Thesis Defense

Title:

First machine learning-based model predictions of Great Gray Owl (Strix nebulosa) distribution in Alaska: A primer for supporting conservation governance

Life Science Hour Seminar

Title:

Navigating the New Arctic: Landscape evolution and adapting to change in ice-rich permafrost systems

Abstract:

Ice-rich permafrost (IRP) is perhaps the most vulnerable element of the rapidly evolving New Arctic. Much of the response to permafrost-related damage has been incremental actions driven by the necessity to repair and stabilize existing roads and structures. There is a need to develop more strategic approaches to mitigation and adaptation informed by science and engineering in collaboration with local observations, knowledge, and preferences. Massive ground ice is at the center of a web of interacting ecosystem components that we call the IRP system (IRPS), which requires a complex-systems approach to understand. Our key questions are: How are climate change and infrastructure affecting IRPS? What roles do ecosystems play in the development and degradation of IRP? and How can people and their infrastructure adapt to changing IRP systems? We are particularly interested in how differences in vegetation, water, and time influence the accumulation and degradation of ground ice in IRP landscapes, and how the loss of ground ice can radically change these landscapes, their components, and the infrastructure built on them. Our ultimate goal is to understand IRPS at local, regional and circumpolar scales. The project is divided into two principal components: "Landscape evolution” and “Adaptation to change”.

Our initial foci for field research are the Prudhoe Bay oil field and the village of Point Lay, Alaska, where permafrost temperatures are changing rapidly with large impacts to ecosystems and infrastructure. Both areas provide excellent examples of IRP-related issues relevant to many other areas of Alaska and the Arctic. We will develop three IRP observatories: 1) Roadside IRP Observatory in the Prudhoe Bay oilfield; 2) Natural IRP Observatory remote from infrastructure; and 3) Village IRP Observatory at Point Lay. The Prudhoe Bay region has the best historical record of geoecological change within the Arctic with key legacy datasets and good collaboration between industry and science. We will revisit permanent plots and remap Prudhoe Bay vegetation and landscapes first studied in the 1970s. We will characterize and compare the permafrost, hydrology, vegetation, and greenhouse gas (GHG) fluxes of IRPS in three main situations: 1) disturbance gradients adjacent to heavily traveled roads in the Prudhoe Bay oilfield; 2) undisturbed tundra first mapped in the 1970s in a relatively undisturbed landscape consisting of drained lake basins and residual surfaces unaffected by thaw lake processes; and 3) extremely-ice-rich yedoma soils in the village of Point Lay, which are similar to several other coastal villages in northwest Alaska. We will use a multidimensional remote-sensing time-series to measure and monitor changes to microtopography, water, snow cover, vegetation, thermokarst, and thermo-erosional features. We will use the field observations, detailed geoecological maps, and remote-sensing products to provide input for improved permafrost and hydrology models to predict permafrost degradation over the next century under different GHG emission scenarios.

Point Lay has received less research and agency attention than other climate-impacted communities, yet its thaw-related issues are among the most critical. Researchers from the UAF Institute of Northern Engineering, Geophysical Institute, Institute of Arctic Biology, and International Arctic Research Center will combine their expertise to address IRPS-related questions in collaboration with project partners. We will work with the Cold Climate Housing Research Center, The North Slope Regional Housing Authority, and the Point Lay community to collaboratively produce adaptive housing strategies and knowledge regarding other forms of infrastructure-ground-ice interactions that are also relevant to other arctic villages. The project is a component of the International Arctic Research Committee (IASC) Rapid Arctic Transitions due to Infrastructure and Climate (RATIC) initiative and the Infrastructure Action Group of the Multidisciplinary distributed Observatories for the Study of Arctic Connections (T-MOSAiC) project.