Comparisons of Structure Among Mixed Dipterocarp Forests of North-Western Borneo

Published Date

Published by: British Ecological Society

DOI: 10.2307/2260691

Stable URL: http://www.jstor.org/stable/2260691

Page Count: 23

Author

Peter S. Ashton and Pamela Hall

Journal of Ecology

Vol. 80, No. 3 (Sep., 1992), pp. 459-481

Abstract

1. Relationships between lowland rain-forest structure, dynamics and site conditions were examined by the establishment of plots and profile diagrams within mature-phase forest at 13 sites and with permanent plots at three of these sites where trees have been enumerated over 20 years. 2. Most forest structural measures were intercorrelated but forest stature was uncorrelated with HCl-extractable soil nutrient concentrations and was apparently related to topography, soil depth and soil water. The relationship between diameter and height varied between forests and was correlated with HCl-extractable P and Mg for dry-land sites. 3. Tall forests generally had more slender canopy trees for a given height than short forests. Vertical stratification was associated with the presence and stand density of emergent trees, which comprise an architecturally and floristically distinct guild. Where emergents are scattered or absent, the main canopy and understorey were dense and no vertical stratification of crowns was perceptible; where emergents formed a continuous canopy, the main canopy was sparse, the understorey less dense and tree crowns were more separated into two horizontal strata. This type of forest appears to be confined to continuously moist soils on lower slopes, flat or undulating land. 4. Leaf size in the subcanopy was positively correlated with measured soil nutrients, and with the relationship between diameter and height. Among canopy trees it was not correlated with soil nutrients, nor with other aspects of forest structure. 5. Plots were originally established within mature phase, avoiding canopy gaps. Since establishment, gaps have accumulated within the permanent plots. Tree mortality was significantly clustered on clay soils, but not on sandy soils where windthrow was apparently less frequent and trees more often died standing. 6. Mean proportional diameter increments of large trees were not correlated with measured soil nutrients; but mean proportional diameter increments of recruits were correlated with measured soil nutrients. 7. A guild of tree species with the seed and/or seedling characteristics and the fast growth of pioneers, but with plagiotropic branching and crowns which reach the forest canopy or even emerge above it, was an important component of the building phase on soils with high mineral concentrations, but was sparsely distributed on other soils. 8. Standing volume and net volume increment were dominated by the mature phase; but soil nutrients probably influenced volume increment in the building phase. 9. Two inland forests, Bukit Mersing and Lambir, exhibited no net change in stand volume over 20 years. At Bako, a coastal forest on shallow freely draining soils, stand volume increased by 15.9% of the initial measurement. This increment occurred among trees of the largest diameter class while there was a net loss of volume in the small classes.

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