Comparative ecology of 11 sympatric species of Macaranga in Borneo: tree distribution in relation to horizontal and vertical resource heterogeneity

Abstract

1 Horizontal and vertical heterogeneity of resource availability, coupled with the specialized use of resources by tree species, results in complex patterns of tree species distributions in tropical rain forests. We studied the horizontal and vertical distributions of 4014 individuals in 11 species of early successional Macaranga (Euphorbiaceae) in tropical rain forest in Sarawak, Malaysia. 2 The horizontal distribution of individual trees was assessed with respect to crown light levels, establishment microsites, and broader scale variation in soil textural properties. Vertical distribution was assessed using an allometric approach to estimate maximum tree height (Hmax) and the slope of the sapling height–diameter relationship. 3 Average light levels intercepted and the proportion of individuals in each of five crown illumination classes varied significantly among the 11 species. Species ranged from extremely high‐light demanding, to quite shade tolerant. Average light levels intercepted by trees generally increased through ontogeny, but the ranking of species did not change significantly. 4 Fewer individuals of the more shade‐tolerant species established on disturbed microsites, irrespective of light levels. Among the more high‐light demanding species, the proportion of trees on different types of disturbed sites varied. 5 Trees of seven species were significantly more common on clay‐rich soils, two preferred sand‐rich soils, and two were not strongly affected by soil texture. 6 Hmax ranged from 5.5 to 31.3 m and was negatively correlated with shade tolerance among species, although among the more high‐light demanding species there was a wide range of tree sizes. Among species, Hmax was negatively correlated with both the slope and y‐intercept of the sapling height–diameter relationship, indicating that small‐statured species (also more shade tolerant) had more slender saplings than larger statured species. 7 Heterogeneity of resource availability leads to differences in horizontal and vertical tree distribution, which are important for the coexistence of 11 Macaranga species.

Leaf size and leaf display of thirty-eight tropical tree species

“…The CE varies from 1, if a tree does not receive any direct light, to 2 if it receives lateral light, 3 if it receives overhead light on part of the crown (10-90% of vertical projection of the crown exposed to vertical light), 4 when it receives full overhead light on the whole crown (>90% of vertical projection of the crown exposed to vertical light), and 5 when it has an emergent crown that has no obstructing foliage over an upward facing cone encompassing the crown, with angles of 45° from horizontal. The CE can be measured repeatedly (average diVerence between two independent observers is 0.1 § 0.01 SE), and there is a good relation between CE and both canopy openness and incident radiation (Davies et al 1998;Clark et al 1993;Keeling and Phillips 2007). For each species the CE was related to tree height, using a multinomial regression analysis (Poorter et al , 2006a(Poorter et al , 2006b).…”

Habitat niche partitioning by 16 species of Myristicaceae in Amazonian Ecuador

“…CII quantifies the light available to a tree by estimating the exposure of the crown on a scale of 1-5: no vertical light and minimal lateral light (1), no vertical light and medium lateral light (2), crown exposed to some vertical and some lateral light (3), crown exposed to vertical and some lateral light (4), crown completely exposed vertically and laterally (5), CII correlates with canopy openness values obtained from hemispherical photographs (Davies et al 1998) and is a rapid and repeatable way of estimating light availability on tree canopies (Keeling and Phillips 2007).…”

Dendrometry and litterfall of neotropical pioneer and early secondary tree species

“…There can be a more pronounced investment in height, in stem structure or in lateral ramifications, which could modify the relative crown width. The h/w index is sometimes used to evaluate the growth features of the trees, and may be related to the successional status (Davies et al 1998;Barbosa 2000, Yamada et al 2000.…”

“…greater height for a given stem diameter, which could be an adaptation to the light competition during early life stage and/or early succession stage. High h/d ratio is positively related with shade tolerance (Davies et al 1998). These species may not require full sunlight to the initial growth and thus may develop in more shaded forest environments, a feature typical of non-pioneer tree species (Denslow 1980, Gandolfi 2000, Yamada et al 2000.…”