Scientia Bruneiana

Fern diversity and distribution in the UBD campus

Daniele Cicuzza — 2020-08-07

Green areas and parks are important for maintaining local biodiversity in urbanised habitats. Recent studies have demonstrated that the biodiversity retained in these areas is also important for engaging citizen scientists in conservation projects. Most of the documentation on biodiversity is from temperate regions, whereas in the tropics this field is still in its infancy. This study documented the fern and fern allies richness and abundance within the Universiti Brunei Darussalam (UBD) campus, Brunei Darussalam. We found 39 species in total, belonging to 20 families and 28 genera. Although the total richness did not differ between forest and open plots, ordination showed that forested areas retained a different species composition. Although none of the identified species were IUCN listed, nearly half of the species were recorded once or twice, indicating small population sizes and the biological value of small forest fragments. Our study contributes to understanding the flora diversity of the UBD campus. These results can be used to minimise environmental degradation during infrastructure development on the UBD campus.

Post-fire impacts on tree diversity in coastal heath forests of Brunei Darussalam

Wardah Haji Tuah — 2020-08-07

The adverse impacts of fires on the diversity of native plants in forest ecosystems are well documented. Tree diversity was studied in coastal heath (Kerangas) forests of Brunei Darussalam, Northwest Borneo after fire events. Eight 20 x 20 m plots were set up in once-burnt (3 plots), twice-burnt (3 plots) and unburnt heath forests (2 plots). All trees (live and dead) with stem diameters of 1 cm and above were censused, and measures of percentage canopy openness and soil variables (pH, gravimetric water and organic matter content, and concentrations of total nitrogen and phosphorus) were determined. Soil pH, gravimetric water content and total nitrogen and phosphorus concentrations, and canopy openness were significantly higher in the burnt plots. Stem diameters were significantly higher in the unburnt heath forests, with mostly Acacia species recording smaller stem sizes (<10 cm dbh). Tree species richness and diversity were significantly lower in the once-burnt plots than in unburnt, intact heath forest plots indicating substantial loss of native tree diversity in fire-affected habitats. Tree community compositions of the once-burnt plots were dominated by invasive Acacia mangium. This study highlights the negative impact of fire on native tree diversity, soil properties and canopy openness of these coastal Kerangas forests, and further provides preliminary evidence that fire events have facilitated the successful establishment of invasive Acacia species.

Distribution of arboreal nocturnal mammals in northern Borneo

Dk Noor Ummiatul Afiqah Pg Zainalabidin — 2021-05-03

This study aimed to determine the distribution of arboreal nocturnal mammals in northern Borneo, in particular the Bornean Striped Palm Civet Arctogalidia stigmatica, Philippine Slow Loris Nycticebus menagensis, Western Tarsier Cephalophacus bancanus, Bornean Colugo Galeopterus borneanus and Island Palm Civet Paradoxurus philippinensis. Nocturnal mammals were surveyed at six sites in northern Borneo of varying habitat types and patterns of disturbance. Standardised point and line transects following predetermined paths were used and mammals searched for with the aid of a thermal imaging camera, a red-filtered head lamp and alternatively, a white light head lamp. With 49% of the observations, A. stigmatica (36 individuals/6 sites) was the most common species across the study sites, followed in abundance by N. menagensis (16/5), C. bancanus (14/3), G. borneanus (11/3) and P. philippinensis (2/2). The highest arboreal mammal density of 4.4 individuals/km was found at our Kiudang study site in Tutong District. In addition to the five focal arboreal mammals, 20 additional species were observed throughout the study. This study reveals variation in arboreal nocturnal mammal presence with habitat type that is likely influenced by diet preferences, habitat fragmentation, and the level of hunting pressure. Further surveys combined with arboreal camera trapping will be necessary to study the secretive and easily disturbed arboreal nocturnal mammals of Borneo.

Source and Reservoir Characteristics of the Eocene Mangahewa Formation in Taranaki Basin, New Zealand: Their implications on petroleum system

Mohamed Ragab Shalaby — 2021-01-30

The Middle to Late Eocene Mangahewa Formation in the Taranaki Basin has been evaluated for its petroleum system (source potential and reservoir qualities). The Mangahewa Formation is generally interpreted as an alternating marginal to shallow marine environment, with lithologies consisting of sandstone, siltstone, mudstone and bitumonius coal. The pyrolysis results show very good source rock generative potential with total organic carbon content of 0.8-90.02 wt. % and hydrogen index values in the range of 54- 491 mg HC/g TOC, with a predominance of oil- and/or gas-prone, mixed Type II-III kerogen. Organic petrographical data reveal that the humic nature of coals being rich in perhydrous vitrinite whereas shales are rich in alginite and bituminite desplaying frequent of migrabitumens. Biomarker analysis suggests predominantly terrigenous origin, whereas pyrolysis T_max data (414–447°C) and other maturity indicators such as biomarkers and vitrinite reflectance indicates immature and mature samples. Petrographic analyses show that the occurrence of compaction and cementation is succeeded by leaching of feldspars and dissolution of calcite cement. The reservoir samples exhibit largely good reservoir quality with porosity being the dominant feature. The average porosity value is 15.7%, with 21.4% average water saturation. The source and reservoir units are part of a complete petroleum system of the Mangahewa Formation, with the overlying Turi Formation seal rock. The petroleum processes of maturation, generation, and migration which started since Lower Miocene (18.8 Ma) have been recorded in many stratigraphic traps within the Mangahewa Formation or other faulted structural traps due to migration. The generation process is expected to continue to the present day as the source continues to attain maturity while it does not yet reach the peak generation.