Stand Structure and Dynamics in the Temperate Rain Forests of Chiloe Archipelago, Chile

Abstract

We compared the structure and dynamics of selected stands (c. 0.8 ha) of rain forest in four islands (Alao, Chaulinec, Talcain, and Isla Grande) of the Chiloe Archipelago (c. 42? 30' S). In each forest stand, we tallied and measured the diameter at breast height (d.b.h.) of all canopy trees (>10 cm d.b.h.) within two 20x20 m plots. We also esti- mated the abundance of seedlings and saplings in each plot. The stands were dominated by broad-leaved evergreen trees and had in common the presence of several species of Myrtaceous trees in their canopies. Nothofagus spp. were absent from all but one stand. Structurally, the forests were dominated by different species, although overall species composition was similar. Drimys winteri was dominant in Talc'an and Chaulinec, Aextoxicon punctatum was dominant in Alao, and Amomyrtus luma was dominant in Isla Grande. Laurelia philippiana, A. luma, and Myrceugenia planipes were common to all forests. Nothofagus dombeyi was only present in Talc'an, represented by a few, large emergent trees. The distribution of individuals by d.b.h. classes (every 5 cm, from 10 to >40) showed that the forests of Alao and Chaulinec are dominated by individuals in the smallest d.b.h. class (about 50% of all stems). In the other forests, those individuals made up only 20% of the canopy, and larger trees were more common. Because of the smaller size and relative isolation of the forest patches in Alao and Chaulinec, this pattern might be attributed to invasion of these stands by species from surrounding second- growth forest. Comparison of tree species densities between plots 1 and 2 in each forest revealed that the distribution of young (<15 cm d.b.h.) individuals is highly patchy within a stand for all dominant species. This result is consistent with the hypothesis that the regeneration of dominant species is favoured within tree fall gaps. A broader scale of patchiness, related to the episodic occurrence of stand-devastating disturbances, could explain the persistence of Nothofagus dombeyi populations in Talc'an. Recruitment of seedlings and saplings in the forests studied was positively correlated with the abundance of each species in the canopy. Accordingly, dominance will be maintained in these forests in the absence of stand- disrupting disturbances.