Natalie T. Boelman, Ph.D. - US grants

As a consequence of global warming, arctic North America has been ?greening? over the past several decades, with increases in relative abundance and size of shrubs documented in numerous locations. Much of the research on this topic examines how this shift toward more woody species affects element cycling, particularly carbon, with potential feedbacks to the atmosphere regionally and globally. To date, the response of higher trophic levels to such shifts in vegetation in the Arctic has not been well studied. One group that has been almost completely ignored is migratory songbirds; they have a complex relationship with shrubs that provide both shelter and food, both of which are directly affected by weather patterns. This research will characterize the interactions between tundra vegetation and migratory songbirds in habitats that differ in shrub dominance for five consecutive growing seasons that will differ in timing and severity of weather events. The team will 1) identify and characterize interactions between shrub dominance and weather to determine how these affect food and shelter availability for migratory songbirds; 2) examine how reproductive success of populations of two songbird species responds to variation in both shrub dominance and timing of spring snowmelt, and; 3) measure how both variation in shrub dominance and timing of spring snowmelt affect composition and size of the entire songbird community. The multi-year approach will allow for examination of how interannual variability in arctic seasonality, particularly the timing of snowmelt, impacts songbird communities. Because the increasing shrub dominance is occurring too slowly for organisms to respond to during the time period of a grant, the researchers will examine habitat usage in open tundra plots, moderate shrub dominance plots, and high shrub dominance plots, at each of four study sites on the North Slope of Alaska. These include Atigun Valley, one of the first tundra stops made by migratory songbirds as they travel north, and at Toolik Lake, farther north, including two additional sites farther north to increase the spatial scale of sampling. In five project years, they will sample intensively at all four field sites to investigate spatial and temporal variation in plant resources, arthropod abundance, songbird community composition, and the arrival, settlement and reproductive success of two songbird species. During five years they hope to capture a range of interannual variability in weather, onset of spring snowmelt, and biotic responses to provide and understanding of current relationships and to predict how future changes in climate and vegetation may affect these organisms. They also intend to verify the use of remote techniques for monitoring bird community attributes via bioacoustic recordings for conducting automated bird community censuses.

Small mammals graze on the vegetation of the Arctic tundra. Although this grazing may influence many aspects of tundra ecosystems, current models do not include grazing by small mammals. In this project, the abundance of voles and lemmings will be varied experimentally using fenced plots. The investigators will observe the responses in the plots, especially focusing on changes in the cycling of carbon and nitrogen. To understand how the current climate controls the importance of grazing by small mammals, the investigators will conduct their studies at three sites in Alaska located in the Seward Peninsula, the foothills of the Brooks Range, and on the Arctic coastal plain. The natural abundance of voles and lemmings will be studied at these sites to provide background for applying the experimental results throughout the Arctic. The results will be used to expand a mathematical model of tundra ecosystems to include grazing by small mammals, which will improve the predictions that can be made about how the Arctic may change in the future. The research will involve a number of undergraduate students and investigators will integrate their research into classes and other educational programs. In addition, they will present a radio program in Barrow, AK.

The investigators will investigate the importance of herbivory by small mammals in controlling the cycling of carbon and nutrients in the rapidly changing Arctic tundra. Through studies at three sites along a latitudinal gradient, the investigators will employ both observations and experiments to quantify the role of grazing by rodents (voles and lemmings) in the functioning of tundra ecosystems. The observations of rodent population dynamics along with ecosystem function will provide key new information relevant to understanding the feedbacks of the Arctic tundra to the global climate. The manipulation of rodent density through exclosures and enclosures will show how potential changes in rodent populations may influence the tundra ecosystem response. In corporation of the observational and experimental results into a quantitative ecosystem model will enhance predictions of future changes and feedbacks with climate.

Across North America, Arctic and boreal regions have been warming at a rate two to three times higher than the global average. At the same time, human development continues to encroach and intensify, primarily due to demand for natural resources, such as oil and gas. The vast and remote nature of Arctic-boreal regions typify their landscapes, environment, wildlife, and people, but their size and isolation also make it difficult to study how their ecosystems are changing. To overcome these challenges, autonomous recording networks can be used to characterize "soundscapes" - a collection of sounds that emanate from landscapes. Unlike traditional observing methods that are expensive, labor-intensive, and logistically challenging, sound-recording networks provide a cost-effective means to both monitor and understand the response of wildlife to environmental and anthropogenic changes across vast areas. One particular challenge with this sound-measurement approach is extracting useful ecological information from the large volumes of soundscape data that are collected. This project will develop the techniques necessary to overcome this challenge.

The researchers' goal is to understand the influence of both environmental dynamics and increasing anthropogenic activity on the behavior and phenology of migratory caribou (Rangifer tarandus), waterfowl, and songbird communities in Arctic-boreal Alaska and northwestern Canada. Through co-production of knowledge with local land managers and indigenous communities, the research team will combine field observations, modeling, and analyses that include: (1) soundscape measurements, (2) camera-trap observations, (3) automated soundscape analyses, (4) analyses of camera-trap caribou observations, (5) high-resolution modeling of environmental variables, (6) statistical analyses including wildlife occupancy, diversity, and phenology modeling, and (7) a human-computation game to collect descriptions of our acoustic recordings that allows for the participation of local and Indigenous players of the game. The project will contribute understanding of how both avian communities and caribou populations are responding to spatiotemporal variations in environmental conditions and increasing development of the oil and gas industry in a region where such comprehensive, large-scale research has rarely been possible. Further, at the request of various Tribal organizations, our research will provide insight into how industrial noise influences traditional practices. In addition, our research will provide baseline data on all natural sounds, including data on bird and caribou activity, in the Arctic National Wildlife Refuge prior to oil and gas development. These datasets will be available to inform Indigenous practices and natural resource management, as well as facilitate future Environmental Assessments required by land managers and oil and gas developers.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.