Southeast Asian forests are globally important for their high species richness and endemicity of plant species. However, the region has suffered from high rates of deforestation, which potentially reduces the availability of habitat for tree species and other components of biodiversity. As a result many species may be at risk of extinction, but the extent of this problem has not been addressed systematically. In this thesis I conduct conservation assessments for multiple tree species in the Dipterocarpaceae growing in Sabah and the Philippines to determine the extent of extinction risk arising from loss of primary forest cover. I used the ecological niche modelling algorithm MAXENT to predict the extent of the historic species distribution and then overlaid contemporary land use maps to estimate the amount of habitat loss for 15 dipterocarps in Sabah and 27 species in the Philippines. Conservation assessments were made by reference to the thresholds of habitat loss required to assign the various categories of threat used in the IUCN Red List. The specific objectives of this thesis were (a) to reconstruct the temporal pattern of loss of primary forest cover in Sabah over the last 25 years using published vegetation maps derived from aerial photography and satellite images; (b) to determine whether habitat loss and conservation assessments estimated using ecological niche models are sensitive to the resolution of data on the distribution of soils within the sampling window; (c) to determine whether estimates of habitat loss and conservation assessments are sensitive to decisions over land use classification from satellite images; and (d) to compare conservation assessments based on ecological niche models to assessments derived from reduction in the extent of occurrence (EOO) and the area of occupancy (AOO), which are the traditional techniques recommended by the IUCN. The ultimate aim of the thesis was to refine the methodology for conducting rapid species conservation assessments for endangered tropical tree species. The rate of loss of primary forest cover in Sabah between the mid 1980s and 2010 was estimated at 0.6 % yr-1. This value obscures substantial variation between consecutive intervals over this period, which ranged from a minimum of 0.2 % yr-1 to a maximum of 8.4 % yr-1. The estimated impact of this loss of primary forest on the amount of habitat available for species of Dipterocarpaceae was dependent on the method used for predicting species distributions. Ecological niche models (ENMs) that incorporated a high resolution of soil information predicted a lower mean area within the historic distribution and a lower amount of remaining habitat area than ENMs developed using either low resolution or no soil data. Percentage habitat loss (mean 71- 75 %) did not differ in response to the spatial resolution of soil data in ENMs. Similarly, estimated amounts and percentages of remaining habitat were strongly dependent on whether secondary vegetation was considered to be suitable habitat for dipterocarps. In general, conservation assessments derived from ENMs were more conservative (i.e. predicted a higher degree of threat) than those developed using the traditional methods based on computing the extent of occurrence and area of occupancy. Ecological niche modelling represents a powerful new tool for implementing rapid conservation assessments of tropical forest trees, but this thesis has identified caveats that must be considered before they can be routinely applied. In particular, many species are under-collected or the distribution of samples is biased, and significant up-scaling of collection effort is required before reliable ENMs can be obtained.

Southeast Asian forests are among the most species rich in the world and are an important source of timber. However, these forests have been severely deforested and more than 70% of remaining forests are degraded. The future of these forests relies on successful regeneration, particularly in human-modified landscapes. Therefore, the aim of this study was to investigate the constraints on reproduction of trees in the Dipterocarpaceae family, which dominate lowland forests in Southeast Asia. Specifically, I aimed to understand the influence of flowering intensity, disturbance history, and genetic diversity of offspring. The proportion of flowers pollinated was higher in larger flowering events for three of the seven species investigated suggesting that flowering intensity may influence pollination. However, further research is required to clarify these results and should include other factors that influence pollination. Disturbance did not negatively affect reproduction in the two species investigated. Parashorea tomentella trees in the disturbed forest produced more flowers (per m2) but had (12%) lower pollination success. However, there was no difference in viable fruit production or seedling establishment. Shorea xanthophylla trees in the disturbed forest produced more flowers (per tree and per m2) and despite having (3%) lower pollination success produced more viable fruit and established more seedlings. My findings indicate that reproduction of some species might be resilient to some types of disturbance and suggest that disturbance to these forests is not used as a pretext to convert them to other land-uses. Finally, the multi-locus heterozygosity (genetic diversity) of offspring was positively related to seedling survival, but did not influence germination or growth. The effect of MLH on survival was greatest in the forest, suggesting that inbreeding depression is stronger under natural growing conditions. Therefore seedlings grown under forest conditions may make better candidates for restoration projects than those grown in a nursery.

A 5.6 ha research plot in logged hill forest in central Peninsular Malaysia at Berkelah F. R., Pahang was set up to study the early establishment of dipterocarp species in the field. The site of the logged forest could be broadly grouped into three classes based on the degree of canopy opening and soil compaction: (1) categories B&A: open (25-55 % relative light intensity (RLI) as a high light level) and compacted or less compacted soil, respectively (2) category C: partial shade (8-9 % RLI as a medium) and less compacted soil, and (3) categories D&E: closed canopy (2-3 % RLI as a low light level) with high and low dipterocarp abundances, respectively. Planting trials in the field were conducted with two dipterocarp species, Hopea odorata and Dryobalanops oblongifolia. Application of Triple superphosphate (TSP), a fast-release fertiliser, (0.33 - 0.40 g per pot) in the nursery increased the P concentrations of the two dipterocarp species, Hopea odorata and Dryobalanops oblongifolia, and improved the performance of their seedlings when outplanted in the field plot. The growth of the species under high light level was greatly increased, but the concentration of foliar nutrients of the seedlings was correspondingly reduced. The order of performance in the field subplot categories was A&B>C>D&E and the order of foliar concentrations was D&E>C>A&B. The study of the effect of P fertiliser, light and types of soil on the growth was supplemented by nursery experiments using two dipterocarp species, Hopea odorata and Shorea acuminata. Soils from the plot and nursery soil as a control were used for potting the seedlings under two light levels, open (high) and shade (low). Adding P increased the infection of ectomycorrhizas (ECM) on the root tips and also increased the foliar P concentrations of Hopea odorata. Light appeared to reduce the infection of ECM. Experiments using sand cultures showed that P and Mg play an important role in influencing the growth of dipterocarp species. The growth of Hopea odorata significantly reduced when the concentrations of P was less than 2.07 mg 1.1 and when Mg was less than 3.63 mg 1-1 . The growth and the concentrations of foliar P and Mg of Hopea odorata were increased in response to an increase in external P and/or Mg supply. These results are interpreted as support for the hypothesis that P and maybe Mg availabilities would limit the establishment of the dipterocarp species. Based on these results, Hopea odorata is grouped as a light demanding species, Shorea acuminata is shade tolerant and Dryobalanops oblongifolia is intermediate species. Reforestation of the logged areas by means of enrichment planting with mixed species of different ecological requirements is one possible way of reclaiming the disturbed areas. Boosting P levels prior to planting may be an effective silvicultural approach in enrichment planting.

This thesis investigates the influence of niche specialisation on floristic composition and species distributions of the family Dipterocarpaceae along topographic gradients at two contrasting lowland Mixed Dipterocarp Forest sites in Brunei Darussalam: Andulau (overlying nutrient-poor sandy soils) and Belalong (overlying nutrient-rich clay soils). Dipterocarp tree density, species richness and diversity were higher at Andulau than Belalong, and were also higher on ridges than in slopes and valleys. Randomisation tests detected significant dipterocarp species associations with site and tomography. Dipterocarp floristic composition was strongly correlated with various habitat variables at Belalong, even after accounting for distance between samples. In contrast, fewer habitat variables were correlated with dipterocarp floristic composition at Andulau, implying weaker habitat effects in this more topographically homogeneous site. In a field-based transplant experiment, <i>Dryobalanops aromatica </i>and <i>Dryobalanops rappa </i>seedlings consistently showed higher growth rates and survival in gaps than in understorey plots. Higher survival and leaf production of <i>D. aromatica </i>seedlings at Andulau than Belalong provide evidence of a habitat preference. Growth and survival of <i>D. rappa</i> seedlings were similar at the two sites, but <i>D. rappa</i> seedlings grew significantly faster in height than <i>D. aromatica </i>seedlings on slopes at both sites. In conclusion, local and landscape scale variations in edaphic and environmental resources influence dipterocarp species distributions and floristic composition, as well as dipterocarp seedling growth and survival. Thus, niche specialisation is an important mechanism in the maintenance of species coexistence at Andulau and Belalong.

Thesis (Ph. D.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

The effects of site conditions on variation in the floristic composition, physiognomy and hollow decay of the Mixed Dipterocarp Forest of Sarawak are investigated. Studies were concentrated on two series of pre-existing plots. The results from the set of larger plots show that there is considerable association between the distribution of floristically defined forest types and site conditions. The results from the smaller plots show that there issome association of site conditions with the distribution of individual species, and also with intraspecific variation in hollow decay. Site effects on the basal areas of individual species, and the basal area and the severity of hollow decay in the forest as a whole are less marked. Interpretation of the results is complicated by the clustered distributions of both series of plots. The relative importance of site properties as determinants of forest floristic variation depends partly on the range of rock, soil and forest types sampled. Over the full range, properties closely related to soil parent material appear to predominate. The results do not indicate any major immediate modifications to current procedures in forest inventory, soil survey or intersectorial land allocation, but they do emphasise the value of interdisciplinary exchanges of information. If regeneration in the forest is to be assisted by planting, the results should be useful in indicating probably viable species/site combinations.

This study examines fruit predation of species in the family Dipterocarpaceae. It was conducted in Pasoh Forest Reserve, a Lowland Dipterocarp Rain Forest in West Malaysia. The work concentrates upon the pre-dispersal weevil predators, whose larvae develop within dipterocarp fruit. After describing the pre-dispersal predators the host specificity of their larvae is examined. A comparison of host records determined in this study with records in the literature demonstrates statistically significant generic specialization by the larvae of some weevil species. The larvae of other species are also restricted to hosts within one genus, but sampling effort was insufficient to demonstrate generic specialization. The most abundant pre-dispersal weevil predator was <i>Nanophyes shoreae</i>. Aspects of the biology of this species are described. These include: the activity of the adult weevils during dipterocarp flowering events; the timing of oviposition; the length of the pre-imaginal development period; the survivorship of adult beetles kept under laboratory conditions. The period of pre-imaginal development varied between host species but was consistent between trees of one species. Quantitative analyses of <i>Nanophyes shoreae's</i> pre-imaginal mortality are also described. The primary mortality factors were abortion of fruit containing eggs and consumption of pupae and III instar larvae by vertebrates. Adaptations that may reduce losses to these primary mortality factors are considered. They include oviposition within those fruit that are least likely to abort and variability in the length of the pre-imaginal development period, causing synchronous development in larvae developing from eggs that were deposited on different dates. None of the dipterocarp fruit predators could be located during periods when dipterocarp fruit were not available. Analyses of their population recruitment during fruiting events and of the availability of fruiting trees (as determined by a phenological survey of Pasoh Forest Reserve) indicates that they are unlikely to have dispersed widely in search of fruiting dipterocarps. The existence of an alternative larval or adult host is discussed.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin-Madison, 1995. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 116-124).

No description available.