The growth condition of
T. dolabrata var.
hondai as understory trees which had been naturally regenerated in a
C. japonica planted forest was compared with that of
C. japonica as understory trees in relation to crown structure and function. Although relative light intensities received by the understory trees were almost the same between the two species at more than 10%, height and diameter growths of
T. dolabrata as understory trees were smaller, being below 10cm in annual height growth, than those of
C. japonica.
T. dolabrata understory trees had longer crown lengths, on their lower height of crown base, and had more crown leaf masses, with higher leaf mass densities in spite of their lower branch densities. On the other hand,
T. dolabrata understory trees showed lower leaf nitrogen contents in either of surface, medium, and inner parts of the crowns; the inter-specific difference was pronounced in the surface part. The low growth performance of
T. dolabrata understory trees was therefore due to the content level and the allocation pattern of nitrogen among the crown leaves. In practicing multi-storied forest managements by introducing
T. dolabrata as understory trees, it would be necessary to take notice of the fact that the inactive growth was observed under the relatively high light conditions.
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