AUTUMNAL LEAF CONDUCTANCE AND APPARENT PHOTOSYNTHESIS BY SAPLINGS AND SPROUTS IN A RECENTLY DISTURBED NORTHERN HARDWOOD FOREST

Leaf surface conductance and apparent photosynthesis were measured during late summer and autumn on saplings and sprouts of pin cherry (Prunus pensylvanica), yellow birch (Betula alleghaniensis), American beech (Fagus grandifolia), and sugar maple (Acer saccharum) naturally revegetating a site in the northern hardwood forest 5 years following a commercial whole-tree harvest. Prior to the disturbance (i.e., the harvest) the site was codominated by American beech, sugar maple, and yellow birch, whereas after the disturbance pin cherry was the dominant species. Conductance and photosynthetic rate of pin cherry leaves were comparatively high while those of American beech and sugar maple were low. Pin cherry retained green, physiologically active leaves longer into autumn than American beech and sugar maple. The rates and seasonal duration of leaf gas exchange on the disturbed site were therefore greater than they would have been had the site not become dominated by pin cherry. © 1990 Springer-Verlag.