Heil Clifford W.

No Thumbnail Available
Last Name
Heil
First Name
Clifford W.
ORCID

Filters

2016 - 2019 2
2
2
Reset filters

Settings

Search Results

Now showing 1 - 2 of 2
  • Article
    CO2 and fire influence tropical ecosystem stability in response to climate change
    (Nature Publishing Group, 2016-07-18) Shanahan, Timothy ; Hughen, Konrad A. ; McKay, Nicholas ; Overpeck, Jonathan T. ; Scholz, Christopher A. ; Gosling, William D. ; Miller, Charlotte S. ; Peck, John A. ; King, John W. ; Heil, Clifford W.
    Interactions between climate, fire and CO2 are believed to play a crucial role in controlling the distributions of tropical woodlands and savannas, but our understanding of these processes is limited by the paucity of data from undisturbed tropical ecosystems. Here we use a 28,000-year integrated record of vegetation, climate and fire from West Africa to examine the role of these interactions on tropical ecosystem stability. We find that increased aridity between 28–15 kyr B.P. led to the widespread expansion of tropical grasslands, but that frequent fires and low CO2 played a crucial role in stabilizing these ecosystems, even as humidity changed. This resulted in an unstable ecosystem state, which transitioned abruptly from grassland to woodlands as gradual changes in CO2 and fire shifted the balance in favor of woody plants. Since then, high atmospheric CO2 has stabilized tropical forests by promoting woody plant growth, despite increased aridity. Our results indicate that the interactions between climate, CO2 and fire can make tropical ecosystems more resilient to change, but that these systems are dynamically unstable and potentially susceptible to abrupt shifts between woodland and grassland dominated states in the future.
  • Article
    The mighty Susquehanna-extreme floods in Eastern North America during the past two millennia
    (American Geophysical Union, 2019-02-19) Toomey, Michael R. ; Cantwell, Meagan ; Colman, Steven ; Cronin, Thomas M. ; Donnelly, Jeffrey P. ; Giosan, Liviu ; Heil, Clifford W. ; Korty, Robert ; Marot, Marci ; Willard, D. A.
    The hazards posed by infrequent major floods to communities along the Susquehanna River and the ecological health of Chesapeake Bay remain largely unconstrained due to the short length of streamgage records. Here we develop a history of high‐flow events on the Susquehanna River during the late Holocene from flood deposits contained in MD99‐2209, a sediment core recovered in 26 m of water from Chesapeake Bay near Annapolis, Maryland, United States. We identify coarse‐grained deposits left by Hurricane Agnes (1972) and the Great Flood of 1936, as well as during three intervals that predate instrumental flood records (~1800–1500, 1300–1100, and 400–0 CE). Comparison to sedimentary proxy data (pollen and ostracode Mg/Ca ratios) from the same core site indicates that prehistoric flooding on the Susquehanna often accompanied cooler‐than‐usual winter/spring temperatures near Chesapeake Bay—typical of negative phases of the North Atlantic Oscillation and conditions thought to foster hurricane landfalls along the East Coast.