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Project ID: 12-1-01-17

Year: 2012

Date Started: 05/01/2012

Date Completed: 02/19/2016

Title: Exploring the Causes of Failed Oak Regeneration in Eastern Deciduous Forests: The Importance of Historic Disturbance Regimes

Project Proposal Abstract: Eastern deciduous forests are undergoing major changes in species composition and diversity that appear outside the expected successional trajectories and often result in impoverished forest biotas. Three changes from historical disturbance and browsing regimes are widespread and may contribute to these shifts: fire frequency is reduced, canopy gaps are smaller, and browsers are more abundant. Which of these factors is most responsible for ongoing changes in forest composition and diversity is a matter of great debate and their relative contribution remains unclear; at least in part because few studies have simultaneously investigated more than one process. We are currently engaged in a large-scale and long-term manipulative experiment near the eastern deciduous forests geographic center where we test whether once common disturbances and their interaction with the top-down influence of browsers can create conditions favorable for the maintenance of a rich understory layer and promote diverse regeneration. Our study, initiated in 1999, is centered at two sites in West Virginia (Fernow Experimental Forest and in the Monongahela National Forest) and consists of a fully-factorial experiment whereby we manipulated canopy gaps (present/absent) of a size typically found in old-growth stands, low intensity understory fire (burned/unburned), and manipulations of deer browsing (fenced/unfenced). This project design is unique in that it also allows the evaluation of interactions among these processes. Indeed, our preliminary published results show interactions among all three factors are pervasive and likely necessary to provide conditions for maintaining vegetative diversity. Our preliminary findings challenge views that fire or canopy gaps alone may maintain or promote diversity of eastern deciduous forest vegetation. We documented that increases in woody and herbaceous richness, abundance, and diversity following co-occurring fire and gaps exceeded that from either disturbance in isolation. Furthermore, the magnitude of the impacts of fire and gaps on diversity were conditional on the presence of deer browsing and on vegetative strata being examined: browsing augmented the effect of co-occurring disturbances on the herbaceous community, but dampened the magnitude of their effect on the regenerating tree community. While our results provide compelling evidence that historical disturbance regimes and moderate browsing maintain and promote plant diversity in the short term (<7 years), it remains unknown whether these effects will persist over a longer term. We propose continued re-measurement of this experiment as it enters its second decade following the prescribed fire treatment. Re-measurements at this time are particularly critical as the study areas transition from stand initiation into the stem exclusion phase  a period of intense competitive thinning among woody species and a concomitant collapse in herbaceous layer richness and abundance. Only by assessing these shifts in vegetation trajectories can we continue to tease apart the multiple ecological processes that are currently having a region-wide influence on forest biodiversity and composition in Eastern deciduous forests.

Principal Investigator: Alejandro A. Royo

Agency/Organization: Forest Service

Branch or Dept: NRS-Northern Research Station

Other Project Collaborators




Branch or Dept

Agreements Contact

David Garrison

Forest Service

NRS-Northern Research Station

Budget Contact

Debbie L. Giovanopoulos

Forest Service

NRS-Northern Research Station

Co-Principal Investigator

Mary B. Adams

Forest Service

NRS-Northern Research Station

Co-Principal Investigator

Walter P. Carson

University of Pittsburgh

Department of Biological Sciences

Co-Principal Investigator

Tim J. Nuttle

Indiana University of Pennsylvania

Department of Biology

Co-Principal Investigator

Melissa A. Thomas-Van Gundy

Forest Service

NRS-Northern Research Station

Project Locations

Fire Science Exchange Network









Project Deliverables

Final Report view or print

("Results presented in JFSP Final Reports may not have been peer-reviewed and should be interpreted as tentative until published in a peer-reviewed source.")

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Supporting Documents

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