Comparative crown form and branching pattern of four coexisting tree species in an old-growth Pseudotsuga-Tsuga forest

Abstract We compared crown expansion rates and branching pattern among four coexisting canopy tree species in a 450-year-old Pseudotsuga menziesii - Tsuga heteroplylla forest in southwestern Washington State, USA. Branch terminal shoot elongation and new shoot production were low at all canopy level...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Veröffentlicht in:Eurasian journal of forest research 2003-09, Vol.6
Hauptverfasser: Ishii, H. (University of Washington, Seattle), Ford, E.D, Sprugel, D.G
Format: Artikel
Sprache:eng
Schlagworte:
Online-Zugang:Volltext
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Beschreibung
Zusammenfassung:Abstract We compared crown expansion rates and branching pattern among four coexisting canopy tree species in a 450-year-old Pseudotsuga menziesii - Tsuga heteroplylla forest in southwestern Washington State, USA. Branch terminal shoot elongation and new shoot production were low at all canopy levels for trees of all species taller than 45 m despite favorable light conditions in the upper canopy. This indicated that the negative effects of physiological aging and increasing size are more important in controlling crown expansion rate than local light conditions. Branch terminal shoot elongation rates were high for the upper-crown branches of short trees despite low irradiance. There may be little crown competition among tall trees in this forest, whereas for the short trees, allocation to shoot elongation in the upper-crown is important for crown expansion and survival. Branching patterns were similar among P. menziesii, A. amabilis, and A. grandis. These three species showed excurrent, symmetrical branching patterns with few internodal shoots and less differentiation among shoots in their elongation rate and bifurcation ratio. In contrast, T. heterophylla showed a reiterating branching pattern where distal shoots on each annual increment were longer and had higher bifurcation ratios than the proximal shoots. When compared with young trees, old trees of T. heterophylla maintain a similar branching pattern, whereas, branching pattern of old P. menziesii trees is markedly different from that of young trees. The changes in branching pattern from young to old P. menziesii trees reflect morphological acclimation to changing stand light conditions as shade-tolerant species invade the stand. This, combined with initial dominance in the upper-canopy where crown competition is less intense, may contribute to the long-term survival of P. menziesii in old-growth forest.
ISSN:1345-8221