Abstract Detail

Ecophysiology

Bobich, Edward [1].

Growth and Physiological Ecology of Coastal Pygmy Oaks and Inland Oaks in a Low Rainfall Year.

Quercus agrifolia, the coast live oak, is a common tree in the woodlands of California.  The species can be up to 25 m tall, but takes on a pygmy growth form on the sand dunes of the El Moro Elfin Forest near the Morro Bay Estuary, where it typically grows no taller than 6 m.  In this study, the physiological ecology and growth of the pygmy oaks in the Elfin Forest were compared to that of an inland grove of coast live oaks in Pomona, California during a low rainfall year (July 2012-June 2013) to assess the stresses experienced by both growth forms in their respective environments.  In addition, different groves of pygmy oaks within the Elfin Forest were studied to determine if exposure and proximity to the water in the estuary affects their physiology and growth.  It was hypothesized that the pygmy oaks would grow less, experience salinity stress, and have lower photosynthetic rates than oaks growing inland.  In addition, pygmy oaks growing on more exposed sites in the Elfin Forest were believed to experience less growth and photosynthesize at lower rates than more protected pygmy oaks because of greater water stress in exposed sites.  Results indicated that pygmy oaks experienced greater overall growth than inland oaks and that pygmy oaks in exposed locations experienced significant leaf loss from spring through the late summer, whereas the inland oaks and pygmy oaks in protected groves experienced almost no leaf loss during this time.  Photosynthesis was greatest for pygmy oaks in protected locations and lowest for both pygmy oaks in exposed groves and inland oaks.  Interestingly, predawn water potentials of pygmy oaks did not change from spring though late summer, whereas inland oaks experienced a significant decrease in predawn water potential.  Midday water potential was highest for the most protected grove, lowest for inland oaks, and intermediate for pygmy oaks on exposed sites.  Finally, salinity does not appear to have an effect on the physiology or growth of pygmy oaks compared with inland oaks, as the osmotic pressure of the xylem of trees in both locations was similar.  Thus, the short stature of the pygmy oaks of the El Moro Elfin Forest is not related to low yearly productivity, salinity, or even water stress, indicating that other factors, including high winds, may determine this unusual form of Q. agrifolia at the edge of Morro Bay.

1 - California State Polytechnic University, Pomona, Biological Sciences, 3801 W. Temple Ave., Pomona, CA, 91768, USA

Keywords:
Physiological ecology
Gas exchange
Water relations
Pygmy.

Presentation Type: Oral Paper:Papers for Topics
Session: 15
Location: Firs South/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 9:00 AM
Number: 15005
Abstract ID:891
Candidate for Awards:None