Mixed Dipterocarp Forest Research Articles

Orchid diversity across different forest types on Mt. Malindang, Philippines

Abstract. Labajo-Villantes Y, Cootes J, Luo Y-B, Nuneza OM. 2024. Orchid diversity across different forest types on Mt. Malindang, Philippines. Biodiversitas 25: 605-615. Mt. Malindang Range Natural Park is one of the most significant biodiversity and conservation areas and is considered a biodiversity hotspot. There have been many biodiversity studies on Mt. Malindang, but information on orchid taxonomy and distribution is limited. This study aimed to conduct a comprehensive inventory of orchids using an exploratory method. Samplings were conducted in different forest types: montane, mossy, dipterocarp, mixed dipterocarp, and almaciga. A total of 114 orchid species with 55 endemics were recorded. Three of these (Phalaenopsis x intermedia Lindl., Paphiopedilum hennisianum (M.W.Wood) Fowlie, and Paphiopedilum haynaldianum (Rchb.f.) Stein) were under Appendix I (can only be exported under specific circumstances). At the same time, 78 were under the Appendix II (follow controlled trades) categories of the Convention on International Trade in Endangered Species of Wild Fauna and Flora. P. hennisianum and P. haynaldianum, listed as endangered species globally, were observed in montane and mossy forests, respectively. Among the six sampling sites, the montane forest was the most species-rich, with the most endemics, followed by the mossy forest. Almaciga and mixed dipterocarp forests were closely related with 100% similarity. The results of this study are valuable to Mt. Malindang's ecological profile for more effective protection and conservation plans.

Old-growth mixed dipterocarp forests show variable losses and gains in aboveground biomass and standing carbon over forty years

BackgroundNo studies have documented long-term trends in aboveground biomass (AGB) for mixed-dipterocarp forests (MDF), the dominant rain forest type in tropical wet equatorial Asia. In our study, we sought to document such trends over forty years across three sites representing lowland to lower montane elevations. MethodsTo do this, we established fifty 100 ​m ​× ​25 ​m plots in 1978 across three sites sampled along an elevation gradient, identified as mature old-growth forest. We measured trees for diameter at breast height that we identified to species and tagged. We took wood samples to calculate species wood-specific gravity. We re-measured plots in 1998 and again in 2018. ResultsWe show standing AGB for all sites combined to be 517.52 ​Mg⋅ha−1 in 1978, but this declined by 17% over 40 years to 430.11 ​Mg⋅ha−1. No differences exist among sites in AGB primarily because of considerable within site variation; but interactions of time with site show declines across sites were not uniform, one remained about the same. Relatively few species represented a high proportion of the AGB with the top five species comprising between 34% and 65%, depending upon site and year sampled. One species, Mesua nagassarium, represented a disproportionately large amount of AGB and decline over time, particularly at the low elevation site. ConclusionsOur results are directly relevant to estimating AGB and standing carbon sequestered in MDF. Our study is the first to demonstrate varying but overall, declining trends in amounts of AGB among forests making predictions of biomass and standing carbon in MDF difficult over wide regions.

Current State Of Knowledge On The Orchids Of Sarawak's Peat Swamps

Sarawak’s peat swamp orchids are considered to be understudied, as most of the related research are favoured to the orchid species from mixed dipterocarp forests. Furthermore, distruptions of their natural habitat caused by various anthropogenic activities have made the orchid assessment studies, especially on the inventory and diversity, to be difficult. Consequently, it widens the knowledge gaps of the orchids’ natural history, current conservation status and their future in the peat swamp areas. Therefore, this inventory was conducted to compile and propose a provisional checklist of orchids distributed in the peat swamps of Sarawak. In total, 52 species from 26 genera of orchids were successfully compiled from the peat swamp areas located at lowlands and coastal plains of Betong, Bintulu, Kota Samarahan, Kuching, Limbang, Miri, Mukah, Sarikei, Sibu and Sri Aman districts. From the account, 10 species are endemic to Borneo. Current conservation status of the recorded species was assessed, and the significant roles of peat swamp areas as orchids natural habitat were further discussed. This compilation provides a glimpse on the current state of knowledge on the peat swamp orchids of Sarawak, thus serves as evidence to preserve the areas in their pristine conditions.

Differential Impacts of Acacia Invasion on Nutrient Fluxes in Two Distinct Bornean Lowland Tropical Rain Forests

Invasive Acacia species can alter nutrient cycling processes in forest ecosystems, particularly affecting total litterfall production and litter decomposition patterns. This study examined the effects of exotic Acacia mangium Willd. on total litterfall production, nutrient concentrations in leaf litterfall fractions, leaf litter decomposition, and nutrient release in lowland heath (HF) and mixed dipterocarp forests (MDF) in Brunei Darussalam, Borneo. Above-ground litterfall traps were installed in HF and MDF with and without invasive Acacia present, representing four habitat types in total, and monthly collections were conducted for 12 months. Litter decomposition bags were deployed to determine the rates of decomposition and nutrient release. Habitats invaded by Acacia exhibited higher total litterfall production, increased leaf litter concentrations of nitrogen, potassium, and calcium, and increased addition of all nutrients measured in litter (nitrogen, phosphorus, potassium, calcium, and magnesium, especially in the Acacia-invaded mixed dipterocarp forest (AMDF) and nitrogen and potassium in Acacia-invaded heath forest (AHF)), reduced nitrogen and potassium use efficiencies in AHF, and reduced stand-level nitrogen and calcium use efficiencies in AMDF. Litter decomposition rates and nutrient release were lower in AMDF than in the three other habitats. The significantly higher total litterfall production coupled with higher nutrient addition in the two Acacia-invaded habitats is expected to progressively increase the abilities of these habitats to produce large quantities of nutrient-rich litter and will likely eventually lead to an enrichment of nutrients in the soil, thus facilitating further invasion by Acacia, particularly in the MDF.

Soil Carbon Pool and Carbon Fluxes Estimation in 26 Years after Selective Logging Tropical Forest at Sabah, Malaysia

The soil carbon pool holds an enormous amount of carbon, making it the largest reservoir in the terrestrial ecosystem. However, there is growing concern that unsustainable logging methods damage the soil ecosystem, thus triggering the release of soil carbon into the atmosphere hence contributing to ongoing climate change. This study uses a replicated (n = 4) logging experiment to examine the impact of supervised logging with climber cutting (SLCC) and conventional logging (CL) on basic soil characteristics, litter input to soils, soil carbon pools, and soil respiration in a mixed dipterocarp forest 26 years after logging. This study found that there was no significant difference observed in the soil physicochemical properties and total carbon pools between the logging treatments and the virgin forest. Soil carbon pools dominated the total carbon pools, and the highest mean value was recorded in SLCC (87.95 ± 13.67 Mg C ha−1). Conventional logging had a lower mean value (71.17 ± 12.09 Mg C ha−1) than virgin forest (83.20 ± 11.97 Mg C ha−1). SLCC also shows a higher value of soil respiration rate (161.75 ± 21.67 mg C m−2 h−1) than CL (140.54 ± 12.54 mg C m−2 h−1). These findings highlight the importance of accurate quantification of the effect of different logging methods on the forest’s carbon pools.

Mapping of Shorea kunstleri King in mixed dipterocarp forest using remote sensing technology

The conventional method used in forest inventory is time-consuming, especially in field surveying and requires an expert’s knowledge and observation to do species identification. This standard method can be facilitated by advances in remote sensing technology. An airborne hyperspectral image mosaic was utilised in the research to evaluate the ability of this high spectral fidelity dataset that was incorporated into a feature extraction Support Vector Machine (SVM) classifier to successfully detect and map a tree species of interest (Shorea kunstleri King) within the mixed dipterocarp forest stand of the Lambir Hills National Park. In this study, two types of feature extraction Principal Component Analysis (PCA) and Spectral Derivative (SD) were applied to classifiers SVM. To demonstrate the effect, classification of the hyperspectral image with no feature extraction was done. The accuracies achieved from different feature extraction were compared statistically. Based on the results, Shorea kunstleri King was able to be discriminated against within 53 species of Shorea. SVM classifier is known for its ability to generalise well even with limited training samples and is commonly used in image classification. The Kernel parameter in SVM classifier alongside feature extraction significantly affects the classification accuracy. Therefore, feature extraction does affect the classification accuracy, but it depends on the morphology of the study area. It is concluded that the SVM method with SD feature extraction could detect tree crowns of Shorea kunstleri with a Kappa coefficient of 0.8126 which showed a great agreement with the observed samples and overall accuracy of 89.89% that shows the accuracy of the final map.

The Distribution and Community's Perception of Flying Fox, Pteropus vampyrus in Limbang, a Transboundary Area in Sarawak.

Flying foxes are threatened throughout their geographic range, and there are large gaps in the understanding of their landscape-scale habitat use. This study identified potential habitats in Limbang, Sarawak and informed potential distribution based on dispersal and interview surveys. Here, biological surveys were combined with interviews of local communities in Limbang Mangrove National Park (LMNP), Sarawak to illustrate distribution and the communities' perception on the protected flying fox (Pteropus vampyrus). Mangrove forest areas were surveyed for for the presence of flying foxes and villagers were interviewed regarding the use by flying foxes of agricultural areas and instances of conflict. Boat and questionnaire surveys were conducted for nine days from 18 to 27 February 2021. The surveys did not record any flying fox roosting sites within the national park and was instead observed to fly from Menunggul Island, Brunei into the national park in the evenings and back to Brunei in the mornings. A total of 27 flying foxes were recorded during the boat survey. Flying foxes were detected from 8/154 survey points and their spatial distribution appeared to be concentrated along Sungai Limpaku Pinang. Most respondents were aware of the species while some have directly observed them in fruit orchards, mangroves, rivers and mixed dipterocarp forests. Eleven perception-based questions were presented, and results showed that locality and income were the most influential parameters exhibiting conservation awareness through Boosted Regression Trees (BRT) analysis. Most respondents believe that flying foxes can uplift the local economy through ecotourism opportunities. However, these findings need to be carefully interpreted as the species has a large home range. Hence, long-term monitoring should be established to generate a larger dataset for stronger analysis to better represent the distribution and occurrence of this species in LMNP.

Acaciainvasion differentially impacts soil properties of two contrasting tropical lowland forests in Brunei Darussalam

AbstractInvasiveAcaciaspecies are known to modify soil properties, although effects are often site-specific. We examined the impact ofAcaciaspecies on the soils of intact and invaded habitats of two contrasting tropical lowland rain forest types in Brunei Darussalam: heath forest (HF) and mixed dipterocarp forest (MDF). Impacts on soil properties differed between the two forest types. Overall,Acacia-invaded HF soil recorded significantly higher gravimetric water content, pH and total P, K and Ca compared to the intact HF soil. In contrast, invaded MDF soil exhibited significantly higher organic matter content and total soil N, P, K and Mg compared to its intact habitat.Acacia-invaded MDF soils were more nutrient-enriched thanAcacia-invaded HF soils by the addition of threefold, threefold and fourfold total soil P, K and Mg, respectively. The positive effect of addition of total soil Ca was, however, fourfold greater in HF soil than MDF soil, indicating that the magnitude of impact on soil properties was strongly site-specific. Overall,Acaciainvasion significantly impacted soil properties in nutrient-rich MDF more than those of nutrient-poor HFs, indicating a potential vulnerability of MDFs to invasion.

Roles of Heterogeneous Habitat for Conservation of Nymphalidae in Sarawak (East Malaysia)

Species diversity characterises an area or a targeted habitat and provides information on the species assemblages, which is a primary reflection of habitat diversity. It incorporates both species richness and abundance and may rely on factors, such as host-plant availability and food resources. Kubah National Park is a lowland mixed dipterocarp forest, and uniquely offers various vegetation types, which includes heath and submontane forests. In the present study, four contrasting forest habitats were selected along forest trails, namely, primary forests, secondary forests, heath forests and forest edges. Forty baited traps were used within a six-months of sampling period. The highest abundance was recorded at the heath forest while the least was at the secondary forest. However, there was no significant difference in terms of species abundance between forest habitats for subfamilies, as well as for the 15 most abundant nymphalid species sampled, except for Mycalesis mnasicles. This satyrine was regarded as being able to differentiate habitat, apart from sensitive to canopy openings. Secondary forest provides a heterogeneous habitat for nymphalids, and thus highest diversity was observed here. This study implies that habitat association of the family is crucial, as it will provide information for both species inventory as well as the fluctuation patterns of the nymphalids diversity. Similar study is suggested to be carried out in the future, which incorporates more than one habitat types and in a more extensive period.

Characteristics of Soil Respiration and Its Components of a Mixed Dipterocarp Forest in China

Background: Although numerous studies have been carried out in recent decades, soil respiration remains one of the less understood elements in global carbon budget research. Tropical forests store a considerable amount of carbon, and a well-established knowledge of the patterns, components, and controls of soil respiration in these forests will be crucial in global change research. Methods: Soil respiration was separated into two components using the trenching method. Each component was measured at multiple temporal scales and in different microhabitats. A commercial soil efflux system (Li8100/8150) was used to accomplish soil respiration monitoring. Four commonly used models were compared that described the temperature dependence of soil heterotrophic respiration using nonlinear statistics. Results and Conclusions: Trenching has a limited effect on soil temperature but considerably affects soil water content due to the exclusion of water loss via tree transpiration. Soil respiration decreased gradually from 8 to 4 μmol·m−2·s−1 6 days after trenching. Soil autotrophic (Ra) and heterotrophic respiration (Rh) have contrasting diel patterns and different responses to temperature. Rh was negatively correlated with temperature but positively correlated with relative humidity. Both Ra and Rh varied dramatically among microhabitats. The Q10 value of Rh derived using the Q10 model was 2.54. The Kirschbaum–O’Connell model, which implied a strong decrease of Q10 with temperature, worked best in describing temperature dependence of Rh. Heterotrophic respiration accounted for nearly half of the total soil efflux. We found an unexpected diurnal pattern in soil heterotrophic respiration which might be related to diurnal moisture dynamics. Temperature, but not soil moisture, was the major controller of seasonal variation of soil respiration in both autotrophic and heterotrophic components. From a statistical perspective, the best model to describe the temperature sensitivity of soil respiration was the Kirschbaum–O’Connell model. Soil respiration varied strongly among the microhabitats and played a crucial role in stand-level ecosystem carbon balance assessment.

Effects of El Niño drought on tree mortality and growth across forest types at different elevations in Borneo

The 2015–2016 El Niño drought had a strong impact on tropical forest tree dynamics in Borneo. To assess the effects of the drought on trees growing in different environments, we examined differences in tree mortality and growth before and during the drought at two elevations (ca. 500 m vs. 1000 m a.s.l.) and among forest types (mainly heath forest on sandy soils and mixed dipterocarp forest) in Sabah, Borneo. We hypothesized that the effects of the drought on trees would be greater at low elevation than at high elevation, and in mixed dipterocarp forest than in heath forest, since tree species in heath forest are likely to adapt to stressful conditions.Tree mortality in heath and mixed dipterocarp forests was higher during the drought than before the drought. In addition, tree mortality was markedly higher at low elevation than at high elevation in both forest types. There was no significant interaction between drought and elevation, indicating that the drought and elevation independently affected tree mortality. Contrary to our expectation, at low elevation, heath forest trees showed comparable or higher mortality than mixed dipterocarp forest trees. Moreover, diameter and basal area growth rates were higher during the drought than before, particularly at low elevation, probably owing to the improved light conditions for surviving trees after the death of surrounding trees. Species-level wood density did not significantly affect tree mortality in our sites. Species mean stem growth rates before the drought negatively affected tree mortality, suggesting that species with higher tree mortality had reduced stem growth prior to the severe drought period.Our results show that the El Niño-induced drought increased mortality and growth of heath forest trees on sandy soils as well as in mixed dipterocarp forest trees. The results also suggest that markedly high tree mortality at low elevation was caused by the additive effect of drought and elevation.

Species Composition and Ecological Distribution of the Subfamily Cicindelinae Latreille, 1801 (Coleoptera: Carabidae) Based on Voucher Specimens in Sarawak

The subfamily Cicindelinae which belongs to the family Carabidae are commonly known as tiger beetles. Despite the recent studies conducted on this taxon, current ecological knowledge on tiger beetles is limited. Thus, this study aimed to provide a current checklist of tiger beetles as well as their species distribution, abundances and habitat preferences in Sarawak based on voucher specimens from Universiti Malaysia Sarawak Insect Reference Collection (UIRC). A total of 76 specimens of tiger beetles were examined in which comprising of seven genera from eight species. The genus Neocollyris was represented with two species, namely Neocollyris (s. str.) ermaginata and Neocollyris (Stenocollyris) sarawakensis macrodera, while the other genera were represented by only one species, respectively. The most abundant species with 64 individuals (84.21%) were represented by Cosmodela aurulenta, followed by Abroscelis tenuipes araneipes and Therates labiatus with three individuals (3.95%) and N. ermaginata with two individuals (2.63%). In this study, there were eight ecological habitats being identified, namely heath forest, limestone forest, littoral forest, mixed dipterocarp forest, oil palm plantation, peat swamp forest, riverine forest and urban area. The data indicates that C. aurulenta being recorded at seven ecological habitats suggesting this species to have a wide distribution capability while species such as A. tenuipes araneipes, Callytron doriai, Cicindela sp., Myriochila (s. str.) specularis brevipennis, N. ermaginata and N. s. macrodera suggesting these species to have a very narrow habitat specialisation. The results of this preliminary study provide evidence on the need to conduct further studies on the ecological aspects of tiger beetles in Sarawak.
 
 Keywords: Cicindelinae, ecological distribution, Sarawak, tiger beetles, voucher specimens

Foraging Behaviour of Three Sympatric Babblers (Family: Timaliidae)

We investigated the foraging ecology of three species of babblers in Kampung Gumbang, Kampung Padang Pan and Dered Krian National Park, Bau. Vegetation in Kampung Gumbang include tall trees, shrubs and patches of kerangas. Dered Kerian National Park consists of mixed dipterocarp forest and limestone forest, which is surrounded by orchards and few villages. In Kampung Padang Pan, the vegetation is a mixed fruit orchard and secondary forest. Foraging data were obtained to compare foraging behaviour in three species. From 133 observations, suspended dead leaves was the most frequently used substrate by the three species. Stachyris maculate showed the most general foraging behavior, and it adopted probing strategy. Cyanoderma erythropterum and Mixnornis gularis obtained food items by gleaning. These three babblers utilize different foraging strategies and substrates, irrespective of their resemblances in other characteristics. C. erythropterum and S. maculate forage mainly among dead and curled, twisted leaves in understory vegetation at significantly different heights. M. gularis forages on dead and living leaves and this species can be found abundantly in disturbed forest and plantation or farm habitats. All the three areas were observed never lacked falling leaves and structural complexity required as foraging substrates by those three babbler species. All three babblers occupy different foraging niches, and therefore interspecific competitions among themselves are minimized.

Diplodiscus latifii (Malvaceae-Brownlowioideae), a new species from Sabah, Malaysia.

A new species of Diplodiscus is described and illustrated from one collection made in lowland mixed dipterocarp forest in Sabah, Malaysia. Conspicuous by its twig colour, leaf shape and indumentum, it is probably allied to D. longifolius, but differs in sufficient characters (shape, indumentum, apex and venation of blade, flower bud shape and size, petal diameter, ovary shape and fruit shape and size) to be a species in its own right. A key to the species of Diplodiscus in Malaysia also is provided.

Assessing tree species diversity and structure of mixed dipterocarp forest remnants in a fragmented landscape of north-western Borneo, Sarawak, Malaysia

Abstract As forest fragmentation continues in many parts of the tropics, the conservation value of forest remnants remains controversial. Our study aimed to assess the structure and tree species diversity of mixed dipterocarp forest remnants from the Planted Forest Zone (PFZ) located in the Bintulu Division, Sarawak, compared with a forest considered relatively undisturbed (i.e. that has experienced no recent logging activities). We also compared three plot methods (50 × 50 m, 20 × 50 m and 10 × 50 m plots) in order to evaluate which could be used for time- and cost-effective inventories of structure and tree species diversity in fragmented forests. No significant differences were found between the fragmented forests and the relatively undisturbed forest for stem density, species richness and diversity indices (Shannon and Simpson). Dissimilarities in species, genus and family composition were observed between fragmented and relatively undisturbed forest, as well as between forest remnants themselves. These dissimilarities were likely to be related to intrinsic variation in these highly diverse tropical forests. However, an unusually high abundance of pioneer species (i.e. Macaranga) was found in plots from forest remnants. The forest remnants also had significantly lower basal areas due to a lack of trees in large diameter classes, which is likely a result of impacts from past logging activities. Otherwise, our results highlight the current high conservation value of the forest remnants—although the studied communities are likely to experience time-delayed shifts in species composition and/or extinctions in the future, with the effect of fragmentation on biodiversity being currently underestimated. Finally, for further studies of fragmented forests we recommend the use of 10 × 50 m plots which are faster and easier to implement in the field while providing estimates of structure and tree species diversity that are consistent with those from larger plots.

Spatial variations of litterfall silicon flux and plant-available silicon in highly weathered soil in a lowland mixed dipterocarp forest of Lambir Hills National Park in Borneo

Spatial variations of litterfall silicon flux and plant-available silicon in highly weathered soil in a lowland mixed dipterocarp forest of Lambir Hills National Park in Borneo

Changes in tree structure, composition, and diversity of a mixed-dipterocarp rainforest over a 40-year period

Little work has examined the spatial and temporal changes of a tropical rain forest for long time periods. Here, we present an analysis of long-term plot data from a Sri Lankan Mixed-Dipterocarp forest (MDF). The plots were established in 1978 at three different elevations (low - 335m, medium - 560 m, and high - 915 m). At each site we measured all trees ≥ 10 cm DBH in 16 or 18 plots. The total area sampled amounted to 12.5 ha. We recorded 166 tree species, with each site comprising between 95 and 121 species. Stem densities and basal areas were different among sites, and declined over the period from 642.8 stems ha−1 and 41.8 m2 ha−1 for the 1978 census, to 496.2 stems ha−1 and 35.2 m2 ha−1 for the 2018 census. The lowest elevation exhibited the highest recruitment, mortality and turnover among sites but patterns changed and became less marked over time. Forest wide tree recruitment was about 1% y−1, while mortality was twice as much averaging about 2% y−1. Four families made up between 44% (1978 census) and 54% (2018 census) of the trees sampled. Two families – Clusiaceae, Dipterocarpaceae contributed up to 33.4% and 37.3% respectively, depending upon site and year of census. The five most common species represent between 31 and 54% of the basal area and between 25 and 66% of the stem density depending upon site. Percentage dominance by the most common species increased over the 40-year time period. Though many trees showed some degree of spatial differentiation, canopy trees showed greater site overlap in their distribution than understory and sub-canopy species. Our results provide an improved picture of variations in MDF structure and composition across the ever-wet realms of equatorial south and southeast Asia. We suggest that dominance in dipterocarps and the degree of closed canopy structure, as measured by basal area, is influenced by time, elevation, the degree of topographic variability within elevation, and topographic interactions with variabilities in climate (drought and windstorms). We propose higher standing basal areas and super dominance of dipterocarps in MDF are linked to site, succession, and landform stability. Dipterocarps increase in dominance with succession (time), with topography (ridges greater than valleys) and with elevation (lowland < hill < lower montane).

Amphibian species diversity in the proposed extension of the Bukit Teraja Protection Forest, Brunei Darussalam

Amphibian species diversity was investigated within the lowland mixed-dipterocarp forest of the proposed extension of the Bukit Teraja Protection Forest (BTPF), Brunei Darussalam in north-west Borneo. A combination of both visual encounter and acoustic sampling techniques were conducted opportunistically as well as in six selected stream transects, each containing five 5x10m plots. A total of 39 species of frogs from seven families (Bufonidae, Ceratobatrachidae, Dicroglossidae, Megophryidae, Microhylidae, Ranidae, and Rhacophoridae) were identified from the BTPF. Most notably, four new records for Brunei were discovered: Hylarana nicobariensis, Kaloula baleata, Limnonectes malesianus, and Microhyla perparva. This brings the total number of amphibian species in Brunei Darussalam to 84. Canonical correspondence analysis showed that out of 13 measured environmental variables maximum stream depth and % soil/sand of ground cover were significantly correlated with anuran assemblage composition. Species overlap between the proposed extension of the Bukit Teraja Protection Forest and the Ulu Temburong National Park (UTNP) determined by the coefficient of biogeographic resemblance (CBR) showed low species complementarity between these two regions. This emphasizes the need to upgrade the proposed extension of the BTPF to a protection forest to ensure the conservation of regional amphibian biodiversity.

Ectomycorrhizal fungal communities of secondary tropical forests dominated by Tristaniopsis in Bangka Island, Indonesia.

In Southeast Asia, primary tropical rainforests are usually dominated by ectomycorrhizal (ECM) trees belonging to Dipterocarpaceae, although arbuscular mycorrhizal trees often outcompete them after disturbances such as forest fires and clear-cutting, thus preventing dipterocarp regeneration. In some secondary tropical forests, however, potentially ECM trees belonging to Tristaniopsis (Myrtaceae) become dominant and may help ECM dipterocarp forests to recover. However, we have no information about their mycorrhizal status in these settings. In this study, we analyzed ECM fungal communities in tropical secondary forests dominated by Tristaniopsis and investigated which ECM fungal species are shared with other tropical or temperate areas. In total, 100 samples were collected from four secondary forests dominated by Tristaniopsis on Bangka Island. ECM tips in the soil samples were subjected to molecular analyses to identify both ECM and host species. Based on a >97% ITS sequence similarity threshold, we identified 56 ECM fungal species dominated by Thelephoraceae, Russulaceae, and Clavulinaceae. Some of the ECM fungal species were shared between dominant Tristaniopsis and coexisting Eucalyptus or Quercus trees, including 5 common to ECM fungi recorded in a primary mixed dipterocarp forest at Lambir Hill, Malaysia. In contrast, no ECM fungal species were shared with other geographical regions, even with Tristaniopsis in New Caledonia. These results imply that secondary tropical forests dominated by Tristaniopsis harbor diverse ECM fungi, including those that inhabit primary dipterocarp forests in the same geographical region. They may function as refugia for ECM fungi, given that dipterocarp forests are disappearing quickly due to human activity.

Isolation and Identification of Culturable Bacteria and Fungi from Mixed Dipterocarp and Mangrove Forests of Brunei Darussalam

Unique forests comprise of culturable microbes with unique properties that are of potential biotechnological uses. Considering that the pristine mixed dipterocarp forest and mangrove forest in Brunei Darussalam located in northwest Borneo in Southeast Asia are not well explored concerning their microbial diversity, this study aims to isolate and identify the culturable bacteria and fungi from these forest ecosystems. Bacteria and fungi were isolated using nutrient agar and potato dextrose agar, respectively. Microbial identification was done by DNA barcoding using 16S rRNA for bacteria and rRNA-ITS marker for fungi and supplemented by Biolog. A total of 16 bacterial and 19 fungal isolates were obtained which were identified to six bacterial and four fungal genera. Mixed dipterocarp forest harbored six genera of bacteria (Agrobacterium, Bacillus, Ralstonia, Staphylococcus, Burkholderia, and Cedecea), whereas mangrove forest showed two genera (Bacillus and Staphylococcus). Both types of forests showed three genera of fungi which were Trichoderma, Penicillium, and Aspergillus, with Saksenaea isolated only from mangrove forests. This study not only enhances the understanding of the diversity of culturable microbes in Brunei’s forest ecosystems, which has been less investigated till date but also of their ecological and biotechnological value.