Agarwood, a valuable non-timber forest product, is threatened by depletion owing to overharvesting. Northeastern Kalimantan collectors in Indonesia practice the selective felling of agarwood-producing trees (Aquilaria spp.). Although this practice has received attention as a sustainable harvesting, some have questioned it. This study aimed to elucidate the effects of selective felling on Aquilaria populations and intentions of local collectors to perform selective felling in Apo Kayan. We examined harvesting practices, Aquilaria populations, felling pressures, local knowledge, changes in felling criteria over time, and customary rules. Observation of harvesting practices revealed that the felling rate of selective felling was <10 % of all encountered trees, which was much lower than that of indiscriminate felling but higher than that of supposed sustainable harvesting. The annual felling pressure was estimated to be 2.3−4.8 % of the total population, but varied widely by location. Local knowledge enabled collectors to detect the possible presence of agarwood based on the appearance of each tree, facilitating a labor-saving and less-destructive harvest. However, local collectors began felling trees that rarely contained agarwood as agarwood became rarer, indicating that they consistently tried to get the highest return on each trip rather than maintaining Aquilaria population. The customary rule for reserving valuable trees does not apply to Aquilaria; thus, local collectors have no restrictions on felling. Accordingly, we conclude that selective felling is intended to maximize short-term returns by saving labor, incidentally resulting in less-destructive, if not sustainable, effects. Further research and dialogue among stakeholders is required to achieve sustainable harvesting.

Tropical rainforests in Southeast Asia are globally recognized as biodiversity hotspots. However, floristic inventories are limited, particularly for hemiparasites growing in forest canopies. This study presents a checklist of showy mistletoe (Loranthaceae) from the Lambir Hills National Park located in the Miri district, Sarawak, northern Borneo, Malaysia. The data were obtained from our intensive field surveys in the national park from 2016 to 2022, and analysis of the herbaria of The Sarawak Herbarium, The Kyoto University Museum, and the Botanical Research Centre in the Semenggoh Wildlife Centre in Sarawak, Malaysia.

A total of 21 species belonging to 10 genera of Loranthaceae were enumerated, along with ecological information for each species. Of these, 15 species were identified at the species level and 6 were identified at the genus level. The occurrence of Macrosolen brunsing Y. W. Low & Ariffin, formerly known only from Brunei Darussalam, was confirmed and represents the first record of the flora in Malaysia. In addition, Lepidaria vaginata Tiegh., formerly known only from its type locality, Mt. Matang, was confirmed. We show that Lambir Hills National Park is the second locality for this species.

The genus Macaranga (Euphorbiaceae) includes myrmecophytes that allow symbiotic ants to nest inside their hollow stems. The plant exhibits a mutualistic relationship with the ants by providing them with so-called “food bodies.” Such symbiotic ants, called “plant-ants,” patrol the surface of the host plants to repel herbivorous insects from the host plants. The ratio of the food body produced by the host plant for the plant-ants to the host plant’s above-ground biomass decreased as the plant grew in Macaranga bancana, a myrmecophytic species. This phenomenon led us to predict that the average number of plant-ants per leaf would decrease as the host plant grew. To test this hypothesis, we counted plant-ant workers on the leaf surface of M. bancana at various stages of its growth in a lowland rainforest in Borneo. We examined the relationship between the number of plant-ant workers per leaf and host plant size. The number of ants per leaf decreased significantly with increasing host plant size. Additionally, the number of plant-ant workers attending to a leaf was significantly higher on younger leaves than on older leaves. However, these differences became significantly smaller as the plants grew. These observations suggest that the need for anti-herbivore defense by plant-ants decreases with increasing tree size and leaf age.

Bamboo species are common in Myanmar forests. They are monocarpic and some (but not all) conspecific bamboo clumps in a forest flower concurrently. The timing of flowering usually differs among bamboo species. Therefore, when flowering occurs in a forest, some spaces within a forest are expected to be occupied by conspecific and/or heterospecific nonflowering clumps of bamboo species. This may lead to the competition for space between seedlings and nonflowering clumps. Two species of bamboo, Cephalostachyum pergracile Munro and Bambusa polymorpha Munro were distributed in a commercial mixed-deciduous plantation forest in Myanmar. In 1997, some clumps of C. pergracile flowered but B. polymorpha did not. We analyzed the spatial relationships between C. pergracile seedlings generated in 1997 flowering and large conspecific and heterospecific bamboo clumps that must not have flowered in that flowering event. The present spatial analysis showed that bamboo seedlings were exclusively distributed in relation to conspecific large clumps and large clumps of counterpart species. Given that bamboo species are early successional and shade intolerant, these pre-empted spaces occupied by nonflowering clumps are assumed to be unsuitable for regeneration of the cohort that will be generated by the flowering event. In this manner, the occupation of spaces by nonflowering clumps during a flowering event will limit the space available for regeneration. Therefore, it was concluded that pre-emption by nonflowering clumps likely plays an important role in shaping the distribution of the two bamboo species in the forest.