Tree dynamics in canopy gaps in old-growth forests of Nothofagus pumilio in Southern Chile

The gap dynamics of two Nothofagus pumilio (lenga) stands have been investigated. We evaluated and compared tree diameter distributions, spatial patterns, tree fall and gap characteristics and regeneration responses in gaps in two old-growth forests of Nothofagus pumilio in Southern Chile (Shangri-La: 36degrees 60' S, 71degrees30' W; Reserva Coyhaique: 45degrees52' S, 72degrees00' W). In addition, we describe relationships between gap size and regeneration characteristics. We detected some differences in tree and sapling densities between sites. The causes of gap formation and the gap size distribution, mean gap area, and gap fraction were similar, but gap abundance was different at the two sites. The Reserva Coyhaique site had 15 gaps/ha compared to 10 gaps/ha for Shangri-La. Sizes of clumps of trees were within the range of sizes of canopy gaps at both sites. The density of saplings was higher in gaps than under closed forest at R. Coyhaique, but not at Shangri-La. We found that sapling densities were unrelated to gap size in both sites. The lower sapling density in gaps at Shangri-La might be explained by the presence of Chusquea quila, a competitive pioneer bamboo species. The height increment was related to gap size at Shangri-La, but not at R. Coyhaique. Gap size itself does not account for all the variation in recruitment performance in these Southern beech stands.