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Project ID: 15-1-07-22

Year: 2015

Date Started: 06/01/2016

Ending Date:  12/31/2017

Title: Pines vs. Oaks Revisited: Forest Type Conversion Due to High-severity Fire in Madrean Woodlands

Project Proposal Abstract: We propose to investigate the long-term consequences of high-severity fire for Madrean pine-oak woodlands in the Sky Islands of Arizona. Type conversion from pine forest to oak shrubland after stand-replacing fire is a key land management concern in the Southwest, yet Madrean pine-oak communities have received relatively little attention on the issue. Like ponderosa pine forests, these woodlands were characterized by frequent, low-severity surface fires before Euro-American settlement. However, after more than a century of fire suppression, large, high-severity fires have become common. Continued fire suppression and projections for increased aridity suggest that this new fire regime is likely to persist. Our past research in the Chiricahua Mountains in southeastern Arizona revealed conversion of Madrean pine-oak woodland to oak shrubland over the first decade in high-severity parts of the 1994 Rattlesnake Fire. To assess the long-term persistence of this conversion, we propose to resample plots from two studies: 48 plots sampled in 1999 and 2003 in the Rattlesnake Fire and an additional 30 plots established in 1986 before any major crown fires. These 78 plots occur across broad physiographic and fire severity gradients. We will re-measure a large suite of variables related to physiography (e.g., elevation, topographic position, etc.), biophysical conditions (e.g., incident radiation, litter), and stand structure (surviving stems, recruits from seed, resprouts, height growth of recruits vs. sprouts). An important value-added component to this study, for which we are not seeking funding, is the investigation of physiological traits underlying post-fire vegetation responses and successional trajectories. We propose to address four sets of questions. Question 1: Does conversion of Madrean pine-oak to oak shrubland after high-severity fire persist over the long term (> 20 years)? Nine years after the fire, prolific oak resprouts had formed an incipient canopy, but pine recruitment from seed was very low. We will examine the extent to which these patterns continue 22 years post-fire. Question 2: Does resprouting in P. leiophylla rescue populations of this species in high-severity fire environments? In 2003, we documented modest resprouting of P. leiophylla after the Rattlesnake Fire, and these individuals were thriving. We will assess the performance of resprouts 22 years after fire to examine the extent to which they are maintaining a small but stable population of pines in an otherwise homogeneous oak woodland. Question 3: How does pine and oak regeneration vary across the fire severity gradient, and to what extent are these responses mediated by site characteristics? In particular, to what extent does pine regeneration after high-severity fire depend on site physiography and biophysical conditions? A key research goal in the Southwest is to explain why pine regeneration after high-severity fire varies across sites. Because our plots occur across broad gradients of site and fire severity, we will be able to analyze the independent effects of these multiple variables on the response of pine-oak woodland after fire. Question 4: To what extent do plant functional traits and tree ecophysiology influence the long-term post-fire response of vegetation to high-severity fire? Vegetation response to fire is influenced by differences in physiological traits among species and between forms of regeneration (recruits from seeds vs. resprouts). We have access to an array of physiological equipment, which we will use to explore the role of these differences in the patterns of response and succession in Madrean pine-oak woodlands after high-severity fire. We will measure carbon assimilation (A), stomatal conductance (g), intracellular CO2 concentrations (Ci), instantaneous water use efficiency, chlorophyll fluorescence (Fv/Fm), and internal water use efficiency via tree rings and ´13C and ´18O isotope analyses.

Principal Investigator: Andrew M. Barton

Agency/Organization: University of Maine

Branch or Dept: Farmington campus

Other Project Collaborators




Branch or Dept

Agreements Contact

Laurie A. Gardner

University of Maine

Farmington campus

Budget Contact

Kathleen P. Falco

University of Maine

Farmington campus

Co-Principal Investigator

Graeme P. Berlyn

Yale University

College of the Environment

Co-Principal Investigator

Helen M. Poulos

Yale University

College of the Environment

Project Locations

Fire Science Exchange Network









Coronado National Forest

Project Deliverables

There is no final report available for this project.
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Supporting Documents

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