© 2006 Heron Publishing—Victoria, Canada
Differential light responses of Mediterranean tree saplings: linking ecophysiology with regeneration niche in four co-occurring
species
Lorena Gómez-Aparicio (1, 2, 4), Fernando Valladares (3) and Regino Zamora (1)
1. Dpto. Ecología, Facultad de Ciencias, Universidad de Granada, Granada, E-1807, Spain / 2. Institute of Ecosystem Studies, 65 Sharon Turnpike, P.O. Box AB, Millbrook, New York 12545-0129, USA / 3. Centro de Ciencias Medioambientales-CSIC, Serrano 115, Madrid, E-28006, Spain / 4. Corresponding author (gomezl@ecostudies.org) / Received April 4, 2005; accepted September 21, 2005; published online April 3, 2006
Summary
The ecophysiological mechanisms underlying plant–plant interactions and forest regeneration processes in Mediterranean ecosystems
are poorly understood, and the experimental evidence for the role of light availability in these processes is particularly
scant. We analyzed the effects of high and low irradiances on 31 ecological, morphological and physiological variables in
saplings of four late-successional Mediterranean trees, two deciduous (Acer opalus subsp. granatense (Boiss.) Font Quer & Rothm. and Quercus pyrenaica Willd.) and two evergreen (Pinus nigra Arnold subsp. salzmannii (Dunal) Franco and Quercus ilex L.), which coexist in mature montane forests. Species differed in both their capacity to withstand high radiation and in
their shade tolerance. The two deciduous species were the least tolerant to high radiation, exhibiting both dynamic and chronic
photoinhibition in full sunlight, with severe implications for gas exchange and photosynthetic performance. Excess light severely
limited the survival of A. opalus subsp. granatense, even minor reductions of excessive radiation (from full sunlight to 80% sunlight) being crucial for sapling survival. Among
species, P. nigra was the most tolerant of high irradiances but showed the poorest shade acclimation. Interspecific differences in the mechanisms
of response to light provide a partial explanation of the differential regeneration patterns previously reported for these
species, with shade-tolerant plants (i.e., deciduous broadleaf species) benefiting the most from associations with nurse plants.
We conclude that light availability is an important environmental factor defining the regeneration niche of Mediterranean
woody species.
Keywords:
Acer opalus subsp. granatense, photoinhibition, photosynthetic light response, Pinus nigra, Quercus ilex, Quercus pyrenaica, shade tolerance.
