Pacific Northwest Research Station

Title: Age-class differences in shoot photosynthesis and water relations of Fraser fir (Abies fraseri), southern Appalachian Mountains, USA

Author: Reinhardt, Keith; Johnson, Daniel M.; Smith, William K.

Date: 2009

Source: Canadian Journal of Forest Research. 39: 1-5 DOI 10.1139/X08-163

Description: Fraser fir (Abies fraseri (Pursh) Poir.) is an endemic tree species found only in refugial mountain-top forests in the southern Appalachian Mountains, USA. Very few studies have investigated the ecophysiology of this species in its natural environment. We measured and compared photosynthetic gas exchange and water relations of understory germinant seedlings <3 cm height), older seedlings (>3 years old and ~0.15 to 1 m tall), and saplings (>10 years old and ~1 to 2 m tall) on a leaf-level basis. No significant differences in gas exchange were found among the age classes, although midday xylem water potentials were significantly different among the age classes. Differences in maximum photosynthesis (A_max) were <13 percent, ranging between 2.4 and 2.7 μmol·m^-2·s^-1 (P = 0.26). Maximum leaf conductances (g_max) were between 0.16 and 0.18 mol·m^-2·s^-1, varying less than 13 percent (P = 0.15). Midday xylem water potentials were similar between SE and SA (-1.2 to -1.4 MPa), but GS values were significantly less negative (-0.2 to -0.5 MPa). Thus, gas exchange and water relations in these understory age classes appeared similar, indicating no particular limitation to advanced regeneration between age classes.

Keywords: Fraser fir, photosynthesis, gas exchange

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Citation

Reinhardt, Keith; Johnson, Daniel M.; Smith, William K.  2009.  Age-class differences in shoot photosynthesis and water relations of Fraser fir (Abies fraseri), southern Appalachian Mountains, USA.   Canadian Journal of Forest Research. 39: 1-5 DOI 10.1139/X08-163.