Climate-Driven Impacts of Warming and Grazing on Sub-Arctic Coastal Wetlands in Alaska

Climate change is rapidly warming the Arctic, especially at lower latitudes. Warmer temperatures and earlier springs are altering the timing of plants and animals, especially for long-distance migratory herbivores. Changes in the timing of both plants and herbivores have the potential to impact plant productivity and nutrient cycling, while also altering plant community diversity and composition. In chapter 2, I conducted a field experiment to investigate how earlier growing seasons and differences in arrival times of migratory geese influence physical traits of sedge forage species. I found that both an earlier growing season and late grazing by geese had similar effects on plant traits but delays in grazing had a greater effect than a change in spring. In chapter 3, I examined how earlier springs and differences in timing of goose herbivores affect soil nitrogen availability in sedge grazing lawns. I found that both earlier growing season and early grazing by geese increased soil nitrogen, while late grazing decreased soil nitrogen. However, early grazing resulted in a greater increase in soil nitrogen than an earlier growing season. In chapter 4, I investigated how warming and grazing interact to affect plant community diversity and composition in three different coastal wetland plant communities. I found that both warming and grazing increase community diversity but can also interact to mediate or synergistically increase community effects. Grazing decreased dominant grasses but increased low-lying forbs, while warming had little effect on functional groups across different communities

Interactions among climate, topography and herbivory control greenhouse gas (CO2, CH4 and N2O) fluxes in a subarctic coastal wetland

High-latitude ecosystems are experiencing the most rapid climate changes globally, and in many areas these changes are concurrent with shifts in patterns of herbivory. Individually, climate and herbivory are known to influence biosphere-atmosphere greenhouse gas (GHG) exchange; however, the interactive effects of climate and herbivory in driving GHG fluxes have been poorly quantified, especially in coastal systems that support large populations of migratory waterfowl. We investigated the magnitude and the climatic and physical controls of GHG exchange within the Yukon-Kuskokwim Delta in western Alaska across four distinct vegetation communities formed by herbivory and local microtopography. Net CO2 flux was greatest in the ungrazed Carex meadow community (3.97 ± 0.58 [SE] µmol CO2 m−2 s−1), but CH4 flux was greatest in the grazed community (14.00 ± 6.56 nmol CH4 m−2 s−1). The grazed community is also the only vegetation type where CH4 was a larger contributor than CO2 to overall GHG forcing. We found that vegetation community was an important predictor of CO2 and CH4 exchange, demonstrating that variation in regional gas exchange is best explained when the effect of grazing, determined by the difference between grazed and ungrazed communities, is included. Further, we identified an interaction between temperature and vegetation community, indicating that grazed regions could experience the greatest increases in CH4 emissions with warming. These results suggest that future GHG fluxes could be influenced by both climate and by changes in herbivore population dynamics that expand or contract the vegetation community most responsive to future temperature change

Early Goose Arrival Increases Soil Nitrogen Availability More Than an Advancing Spring in Coastal Western Alaska

An understudied aspect of climate change-induced phenological mismatch is its effect on ecosystem functioning, such as nitrogen (N) cycling. Migratory herbivore arrival time may alter N inputs and plant–herbivore feedbacks, whereas earlier springs are predicted to increase N cycling rates through warmer temperatures. However, the relative importance of these shifts in timing and how they interact to affect N cycling are largely unknown. We conducted a 3-year factorial experiment in coastal western Alaska that simulated different timings of Pacific black brant (Branta bernicla nigricans) arrival (3 weeks early, typical, 3 weeks late, or no-grazing) and the growing season (ca. 3 weeks advanced and ambient) on adsorbed and mobile inorganic (NH4+–N, NO3-–N) and mobile organic N (amino acid) pools. Early grazing increased NH4+–N, NO3-–N, and amino acids by 103%, 119%, and 7%, respectively, whereas late grazing reduced adsorbed NH4+–N and NO3−–N by 16% and 17%, respectively. In comparison, the advanced growing season increased mobile NH4+–N by 26%. The arrival time by geese and the start of the season did not interact to influence soil N availability. While the onset of spring in our system is advancing at twice the rate of migratory goose arrival, earlier goose migration is likely to be more significant than the advances in springs in influencing soil N, although both early goose arrival and advanced springs are likely to increase N availability in the future. This increase in soil N resources can have a lasting impact on plant community composition and productivity in this N-limited ecosystem

Development of a Culturally Appropriate Smokeless Tobacco Cessation Program for American Indians

This study describes a multiphasic approach to the development of a smokeless tobacco cessation program targeted for American Indians (AI) of different tribal nations. The authors gathered formative data from a series of focus groups and interviews to investigate the knowledge, attitudes, and beliefs of AI and smokeless tobacco (SLT) use. Predominant themes emerged from four major topic areas (SLT use, initiation and barriers, policy, and program development) across both studies. This study further assessed educational materials developed for the cessation program for scientific accuracy, readability, and cultural appropriateness. Program materials were scientifically accurate and culturally appropriate. The average corrected reading grade level was 6.3 using the Fry formula and 7.1 using the SMOG formula. Based on this research, a detailed approach to formative research can be used in combination with input from community members to develop health interventions that address health disparities for a specific population

ABRF Proteome Informatics Research Group (iPRG) 2016 Study: Inferring Proteoforms from Bottom-up Proteomics Data.

This report presents the results from the 2016 Association of Biomolecular Resource Facilities Proteome Informatics Research Group (iPRG) study on proteoform inference and false discovery rate (FDR) estimation from bottom-up proteomics data. For this study, 3 replicate Q Exactive Orbitrap liquid chromatography-tandom mass spectrometry datasets were generated from each of

Cloud Cover and Delayed Herbivory Relative to Timing of Spring Onset Interact to Dampen Climate Change Impacts on Net Ecosystem Exchange in a Coastal Alaskan Wetland

Rapid warming in northern ecosystems over the past four decades has resulted in earlier spring, increased precipitation, and altered timing of plant–animal interactions, such as herbivory. Advanced spring phenology can lead to longer growing seasons and increased carbon (C) uptake. Greater precipitation coincides with greater cloud cover possibly suppressing photosynthesis. Timing of herbivory relative to spring phenology influences plant biomass. None of these changes are mutually exclusive and their interactions could lead to unexpected consequences for Arctic ecosystem function. We examined the influence of advanced spring phenology, cloud cover, and timing of grazing on C exchange in the Yukon–Kuskokwim Delta of western Alaska for three years. We combined advancement of the growing season using passive-warming open-top chambers (OTC) with controlled timing of goose grazing (early, typical, and late season) and removal of grazing. We also monitored natural variation in incident sunlight to examine the C exchange consequences of these interacting forcings. We monitored net ecosystem exchange of C (NEE) hourly using an autochamber system. Data were used to construct daily light curves for each experimental plot and sunlight data coupled with a clear-sky model was used to quantify daily and seasonal NEE over a range of incident sunlight conditions. Cloudy days resulted in the largest suppression of NEE, reducing C uptake by approximately 2 g C m−2 d−1 regardless of the timing of the season or timing of grazing. Delaying grazing enhanced C uptake by approximately 3 g C m−2 d−1. Advancing spring phenology reduced C uptake by approximately 1.5 g C m−2 d−1, but only when plots were directly warmed by the OTCs; spring advancement did not have a long-term influence on NEE. Consequently, the two strongest drivers of NEE, cloud cover and grazing, can have opposing effects and thus future growing season NEE will depend on the magnitude of change in timing of grazing and incident sunlight