Author: Forrest Hoffman
Organization: Oak Ridge National Laboratory
Abstract: Natural and anthropogenic disturbances can amplify the highly uncertain climate-carbon cycle feedbacks induced by rapidly increasing atmospheric carbon dioxide (CO2) concentrations. In order to reduce the range of uncertainty in projections of future climate and atmospheric CO2 concentrations, Earth System Model (ESM) representations of feedbacks must be improved through comparison with contemporary observations. Presented will be an evaluation of ocean and terrestrial model responses to El Niño-Southern Oscillation (ENSO) disturbances constrained by atmospheric CO2 observations.
Author: Matthew D. Hurteau
Organization: School of Forest Resources, Pennsylvania State Univ.
Position: Assistant Professor
Title: Accounting for risk in valuing forest carbon offsets
Abstract: The recent increase in large and severe fires represents risk in forest carbon offset investment. We used LANDFIRE data products to quantify the value of forest carbon as a function of the risk of loss due to wildfire. Our results indicate that carbon value varies as a function of forest type and condition. The metric accounts for management-driven changes in condition, allowing for site specific quantification of the carbon value of that management action.
Author: Hanna Lee
Organization: Climate & Global Dynamics Division, National Center for Atmospheric Research
Position: Postdoctoral Research Associate
Title: Changes in ecosystem C cycling in the arctic under thawing permafrost and the desert under drought
Abstract: I investigated the effects of permafrost thaw on ecosystem carbon balance at an Alaskan tundra site under a natural gradient of permafrost thaw. Currently, I am working on incorporating permafrost thawing and thermokarst in the Community Earth System Model to improve the applicability of terrestrial biogeochemical cycles within the model. In addition, I investigated the implications of severe drought on carbon cycles in desert ecosystems via understanding the balance between biotic and abiotic decomposition pathways. View PDF
Authors: Michael M. Loranty1, Scott J. Goetz1, Michelle C. Mack2, Heather D. Alexander2, Pieter S.A. Beck1
Organization: 1The Woods Hole Research Center; 2 Univ. of Florida, Dept. of Biology
Position: Postdoctoral Fellow
Title: Measuring and modeling the effects of alternate post-fire successional trajectories on boreal forest carbon dynamics in central Alaska
Abstract: Recent field studies in central Alaskan boreal forests show that residual soil organic layer depth decreases as fire severity increases, resulting in increased establishment of deciduous seedlings and altered post-fire stand composition with increased deciduous dominance. It is therefore necessary to quantify differences in ecosystem carbon dynamics between forest successional trajectories in response to burn severity in order to understand changes in regional or global feedbacks between boreal forests and climate.
Authors: Alison Munson
Organization : Centre d'étude de la forêt (CEF); Faculté de foresterie, de géographie et de géomatique ; Université Laval
Position : Professeure, Écologie forestiére
Title: Measuring and modelling carbon storage in Quebec boreal black spruce ecosystems under varying fire regimes: Projet C*FIRE
Abstract: Our multidisciplinary team is measuring key elements of carbon dynamics in boreal forests and subsequently integrating this information via a modeling exercise. We are examining the relationship between fire severity and the quantity and quality of charcoal produced. Fire severity effects on regeneration and early response of understory vegetation is evaluated and integrated into the modeling exercise. We will identify abiotic factors that may interact with severity to control succession, productivity and carbon storage.
Authors: Shuli Niu, Yiqi Luo et al.
Title: State Changes in Terrestrial Ecosystem Carbon Cycling after Recovering from Disturbance
Abstract: We synthesized a total of 90 case studies that examined ecosystem recovery following disturbances. The results showed that recovery times changed greatly among variables and disturbance types, which were related to disturbance severity. States that ecosystems recovered to after disturbances were different from the pre-disturbance ones for most disturbance types and variables, suggesting that ecosystems were on a return trajectory to a different states after disturbance.
Authors: O'Halloran, T.L., Law, B.E., Wang, Z., Barr, J.G., Schaaf, C., Brown, M., Goulden, M.L., Fuentes, J.D., Göckede, M., Black, A., Engel, V.
Organization: Sweet Briar College, Environmental Sciences
Position: Tom O'Halloran, Visiting Assistant Professor
Title: Albedo and CO2 radiative forcing of forest mortality from fire, beetles, and hurricane wind-throw
Abstract: Albedo radiative forcing following fire is well known. However, here we show that significant albedo change can occur after beetle mortality and hurricane wind-throw in forests as well. In all three cases, the calculated radiative forcing from the albedo change is on the same order of magnitude as the CO2 forcing. In high latitude cases, where snow is present, the albedo radiative forcing offsets the CO2 forcing. In contrast, hurricane defoliation of a mangrove forest provides an example where albedo decreases and therefore exacerbates heating. All three of these disturbance types are likely sensitive to climate change.
Authors: N. Pederson, Tree Ring Laboratory, Lamont-Doherty Earth Observatory
James M. Dyer, Dept. of Geography, Ohio Univ.
Ryan W. McEwan, Dept. of Biology, Univ. of Dayton
Amy Hessl, Dept. of Geography and Geology, West Virginia Univ.
Cary Mock, Dept. of Geography, Univ. of South Carolina
David Orwig, Harvard Forest, Harvard Univ.
Ben Cook, NASA GISS
Title: Episodic, regional-scale dynamics across a mesic, temperate forest
Abstract: Tree-ring data covering 840,000 km2 and 5.3k tree recruitment dates spanning 1.4 million km2 revealed: 1) the occurrence of simultaneous canopy accession events driven partially by drought, and 2) a large-scale tree recruitment event that seems to occur during a highly-variable century of hydroclimate. These results challenge traditional views regarding characteristic disturbance regime in humid temperate forests, and speak to the importance of punctuated climatic events in shaping centennial-scale forest structure and function.
Author: Rodrigo Vargas
Organization: Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE)
Position: Investigador Titular
Abstract: Hurricanes are infrequent disturbances that affect ecosystems and have evident (e.g. uprooting of trees) and less evident or invisible (e.g., changes in belowground processes) effects. The objective of this study was to explore the temporal trends of extreme soil CO2 efflux, as an invisible effect, following a hurricane disturbance. I used over two years of measurements of soil CO2 efflux, following the pass of a hurricane in a tropical forest, to calculate the 95th percentile using extreme-value distribution theory. First, the data were used to determine how the probability of extreme CO2 efflux events changed following a large-scale disturbance (i.e. hurricane). Second, I study the how the ratio between 30-day mean and extreme CO2 efflux events change with time. Third, I explore the spectral properties of the complete time series and of the extreme CO2 efflux events. Annual emissions for the first year following the hurricane disturbance were 3933 gC m2 y-1 whereas for the second year emissions were 1656 gC m2 y-1, representing a reduction of nearly 58%.