Peatlands cover ~4 million km2 and have accumulated ~500 Pg C over the past ~10-20 thousand years, almost entirely as peat (organic soil). For comparison, the ~40 million km2 of global forests have ~200 Pg C aboveground woody biomass, mostly accumulated within the past few hundred years. The majority of peatland area and peatland carbon is north of 45°N, where warming is projected to be greater than the global mean. About one-third of northern peatlands are associated with permafrost. Peatlands influence the global carbon-climate system primarily through the net exchange of two greenhouse gases – CO2 (peatlands are typically a sink) and CH4 (peatlands are typically a source). The net climate impact of a peatland depends primarily on its hydrological setting, vegetation composition, and the time horizon chosen for impact assessment – in the short term CH4 is important, while over centuries to millennia the CO2 balance dominates. There is no strong evidence that peatlands significantly contributed to 20th century changes in the atmospheric burden of CO2, CH4, or N2O; will this picture change in the 21st century? A review of experimental and observational studies of peatland dynamics indicates that the main global change impacts on peatlands that may have significant climate impacts are (1) drainage, especially in the tropics; (2) widespread permafrost thaw; and (3) increased fire intensity and frequency as a result of drier climatic conditions and/or drainage. Quantitative estimates of global change impacts are limited by the sparse field data (particularly in the tropics), the large variability present in existing data, uncertainties in the future trajectory of peatland use, interactive effects of individual impacts, and the unprecedented rates of climate change expected in the 21st century.
(hosted by Serita Frey)

Locally extensive pre-Columbian human occupation and modification occurred in the forests of the central and eastern Amazon Basin, but whether comparable impacts extend westward and into the vast terra firme (interfluvial) zones, remains unclear. We analyzed soils from 55 sites across central and western Amazonia to assess the history of human occupation through charcoal and phytolith analyses. Sparse occurrences of charcoal and the lack of phytoliths from agricultural and disturbance species in the soils during pre-Columbian times indicated that human impacts on interfluvial forests were small, infrequent, and highly localized. No human artifacts or modified soils were found at any site surveyed. Riverine bluff areas also appeared less heavily occupied and disturbed in the western-most forests than similar settings from eastern Amazonia. Our data indicate human impacts on Amazonian forests were heterogeneous across this vast landscape. Environmental and climatic gradients may drive the gradient of prehistoric human occupation, and we are modeling the probability of cultural features across the Amazon basin based on a suite of 30 parameters.
(hosted by Mike Palace)

Infectious disease has recently joined poaching and habitat loss as a major threat to African apes. Both ''naturally'' occurring pathogens, such as Ebola and Simian Immunodeficiency Virus (SIV), and respiratory pathogens transmitted from humans, have been confirmed as important sources of mortality in wild gorillas and chimpanzees. While awareness of the threat has increased, interventions such as vaccination and treatment remain controversial. Here we explore both the risk of disease to African apes, and the status of potential responses. Through synthesis of published data, we summarize prior disease impact on African apes, and then use a simple demographic model to illustrate the resilience of a well-known gorilla population to disease, modeled on prior documented outbreaks. We found that the predicted recovery time for this specific gorilla population from a single outbreak ranged from 5 years for a low mortality (4%) respiratory outbreak, to 131 years for an Ebola outbreak that killed 96% of the population. This shows that mortality rates comparable to those recently reported for disease outbreaks in wild populations are not sustainable. This is particularly troubling given the rising pathogen risk created by increasing habituation of wild apes for tourism, and the growth of human populations surrounding protected areas. We assess potential future disease spillover risk in terms of vaccination rates amongst humans that may come into contact with wild apes, and the availability of vaccines against potentially threatening diseases. We discuss and evaluate non-interventionist responses such as limiting tourist access to apes, community health programs, and safety, logistic, and cost issues that constrain the potential of vaccination.
(hosted by Joel Hartter)

Stream-groundwater interactions underpin many ecological functions and services of streams. Until recently, investigating these interactions has been done from either the stream's perspective, by adding tracers and interpreting downstream tracer breakthrough curves, or from generating numerical groundwater flow models of the channel and adjacent aquifers. Our research group has been collaboratively developing several new approaches to interpreting stream tracer experimental data and new geophysical techniques to determine the extent of stream water movement into the subsurface. In this presentation, I will discuss new approaches to advancing hydrologic science through these new methods.
(hosted by Shan Zuidema)

Dr. Gordon Bonan (CV) is a Senior Scientist at the National Center for Atmospheric Research in Boulder, CO. Dr. Bonan's research examines the interactions of terrestrial ecosystems with climate. This research integrates ecological, hydrological, and atmospheric sciences to study terrestrial ecosystems, their responses to climate change, feedbacks that amplify or mitigate climate change, and human perturbations to ecosystems that alter climate. Gordon specializes in the development of and experimentation with coupled models of Earth's biosphere, atmosphere, hydrosphere, and geosphere system.
(hosted by Liz Burakowski)

The increase in atmospheric nitrogen (N) deposition from industrial pollution is of major concern in northern ecosystems, which are typically nutrient-limited. Previous studies have hypothesized that N deposition may increase the carbon dioxide (CO2) sink potential of northern ecosystems by stimulating plant productivity. Peatlands, in particular nutrient-limited bogs, have accumulated vast amounts of carbon (C) since deglaciation, yet the annual C balance is often a very small difference between plant production and soil decomposition. The main objective of my research program is to improve our understanding of complex feedbacks between peatland ecosystems and the atmosphere in response to increasing atmospheric N deposition and climate change. Does N deposition enhance or diminish the CO2 sink potential of nutrient-limited bog ecosystems? What are the positive and negative feedbacks of N deposition to net ecosystem CO2 exchange and climate change? How do changes in vegetation function and structure, as well as corresponding changes in microclimate (moisture, temperature, light interception), contribute to changes in the carbon balance? How will changes in leaf chemistry, phenology, and plant function affect the seasonality of CO2 exchange? Research has been conducted at long-term fertilization experiment at Mer Bleue Bog in Ottawa, Ontario, Canada. Treatments have included fertilization with varying levels of nitrogen, phosphorus, and potassium. The measurements and experiments include several field and laboratory components: ecosystem and leaf-level CO2 gas exchange of mosses and vascular plants at a range of light levels, leaf biochemistry to test stress responses to potential N saturation, above and belowground plant production and decomposition, and microclimate within the plant canopy and soil profile.
(hosted by Steve Frolking)

Peatlands are an important component of the Earth's carbon cycle, storing roughly one-third of the Earth's soil carbon and emitting more than half of all natural methane emissions. The degree to which peatlands act as carbon sources or sinks depends on the climate, which influences peatland hydrology, net primary productivity, and respiration rates. This talk focuses on the expansion of peatlands at the end of the Last Glacial Maximum (LGM), and using Alaska as an example, explores how the orbitally-forced Holocene Thermal Maximum in Alaska promoted peatland development and how regional changes in precipitation patterns influenced carbon accumulation rates. Finally, two case studies from the continuous and discontinuous permafrost zones of Alaska examine the impact of permafrost thaw on long-term carbon cycling in peatlands.
(hosted by Claire Treat)

Human induced environmental change has altered the distributions of many species, and in some cases, closely related species that were once allopatric have come into secondary contact. Following contact, competition and hybridization can further shape species distributions and potentially lead to extinction. Understanding the relative importance of environmental change and species interactions on population dynamics and distributions has important conservation implications. For example, the blue-winged warbler continues to expand its range into regions formerly occupied solely by the golden-winged warbler, yet the effect of the ensuing hybridization on the viability of the two species depends upon the degree to which they are able to adapt their distributions and maintain regions of sympatry. I will present results from an analysis of 45 years of data on these two species in order to shed light on the relative importance of environmental change and species interactions in shaping the distributions of the two species. I will also demonstrate how hierarchical models can be used to predict likely outcomes (e.g. extinction or coexistence) under future environmental scenarios.
(hosted by Dan Hocking)

Most of the ice mass lost from Antarctica occurs through basal melting and iceberg calving from ice shelves. Ice shelves are in direct contact with the ocean and are therefore more responsive to climate change than the rest of the grounded ice sheet. They also play an important role in buttressing their source glaciers, influencing their speed and the rate of ice-mass flux off of the continent. This presentation will provide an introduction to these sensitive regions and an overview of methods of investigating their dynamics, with a focus on the remote sensing of their grounding zones and calving fronts.
(hosted by Ryan Cassotto)

Abstract under development
(hosted by Serita Frey)