Habitat Characterizations Underestimate the Role of Edaphic Factors Controlling the Distribution of Entandrophragma

Abstract

Numerous theories have been developed and tested to explain the high botanical diversity in tropical forests, ranging from nonequilibrium theories emphasizing the importance of chance to equilibrium theories depicting highly specialized species occupying narrow ecological niches. Niche-based theories have most often evaluated species adaptation to different light environments, but some studies have evaluated the importance of edaphic attributes in controlling species distributions. We evaluated the role of edaphic factors in controlling the distribution of African mahogany in the genus Entandrophragma on a 100-ha plot in the Dzanga-Sangha Dense Forest Reserve, Central African Republic. This study went beyond simple characterization of edaphic conditions in topographic or other classes to test for specific associations with chemical and physical soil parameters known to be important to plant growth. Trees Ն30 cm dbh of the four species of Entandrophragma evaluated were nonrandomly distributed in the forest. Torus translation tests indicated that none of the species exhibited any topographic preferences. However, three of the four species had significant associations with at least two soil chemical attributes. Randomization tests evaluating links between soil chemical and physical properties and topographic position underscored the complexity of the relationship and suggest that inferring edaphic attributes from broadly and simply defined habitat classes may significantly underestimate the importance of soil heterogeneity in contributing to species coexistence.

Seed and seedling survival of African mahogany (Entandrophragma spp.) in the Central African Republic: Implications for forest management

“…Seedlings of these species have been shown experimentally to develop best in approximately 25% full sunlight (Synnott, 1975;Pieters, 1976;Swaine et al, 1997;Agyeman et al, 1999;Hall et al, 2003c). Hall et al (2004) linked adult meso-scale spatial distribution patterns of three of these four Entandrophragma spp. (E. angolense, E. candollei, and E. cylindricum) to edaphic factors and suggested that growth performance helps explain adult tree distribution of E. candollei and E. cylindricum seedlings in relation to soil fertility (Hall et al, 2003a).…”

“…(Carroll, 1997); mean temperature varies between 24 8C (December) and 29 8C (April). Soils within the study area are generally classed as oxisols but with important variability in fertility within the study site (see Hall et al (2004) for further description).…”

Soil nutrients influence spatial distributions of tropical tree species

“…Although the importance of edaphic factors in maintaining local diversity has long been recognized (29,30), a thorough, quantitative assessment of the importance of soil resources on tropical tree distributions for entire communities has not been undertaken. Typically, studies have either focused on a small fraction of the tree species in any community (31)(32)(33) or related community-wide tree species distributions to topographical variables whose relationships with underlying soil resources are unknown (28,34,35). To test relationships between species distributions and soil resource availability, soil resources and species distributions need to be mapped at high spatial resolution for entire communities in plots large enough to span substantial spatial heterogeneity in soil factors.…”

Habitat partitioning among neotropical pioneers: a consequence of differential susceptibility to browsing herbivores?

“…Shorea, Polyalthia and Aporosa in S.E. Asia, Ashton 1988;Rogstad 1990;Debski et al 2002; Entandrophragma in the Central African Republic, Hall et al 2004; Rinorea in Ecuador, Valencia et al 2004).…”