Dead logs as a substrate for rain forest trees in Dominica

Abstract

Dead logs, or 'nurse logs', have been reported as an important substrate for germination and establishment of a few tree species in wet temperate forests of New Zealand (Beveridge 1973) and coastal Washington, USA (Franklin & Dyrness 1973) and in an exposed cloud forest in Costa Rica (Lawton & Putz 1988). These environments are con-tin-uously wet and, in all, dead logs are a prominent feature on the ground. Hartshorn (1980) stated that dead logs were not important as sites for tree regeneration in lowland Neotropical rain forests except in swamps, but in rain forests in the Commonwealth of Dominica (West Indies), the common tree Miconia mirabilis (Aubl.) L.O.Wms. had a complex system of stilt roots that sometimes appeared to penetrate dead wood (Figure 1). As part of a study on forest dynamics an investigation was made to see whether this, or any other species, was associated with dead wood as a substrate. Four sites in different parts of the island were studied, totalling 7500 m' and ranging from 300 m to 650 m in altitude. These had the 'rain forest' to 'lower montane rain forest' formations of Beard (1948), dominated particularly by Dacryodes excelsa Vahl.. The forests remain fairly wet throughout the year, but there is a distinct dry season in most years. They are never waterlogged (personal observation and discussion with Forestry Division staff). The canopy, at 3040 m, was fairly complete in sites 2 and 3, but in site 1 had been broken up by hurricane 'David' in 1979 (see Lugo el al. 1983) and, in site 4, this hurricane had destroyed all but a few canopy trees (most regrowth was c. 10 m high). Four common species of Melastomataceae were studied, Miconia mirabilis (Aubl.) L.O.Wms. (syn. M. guianensis Cogn. of Beard 1948), a tree up to 18 m in height, Miconia furfuracea (Vahl.) Griseb. and Miconia trichotoma (Desr.) DC., both large shrubs up to 10 n in height and Clidemia umbrosa (Sw.) Cogn., an undershrub up to 3 m, along with Cecropia sc/zreberiana Miq. (Cecropiaceae), a