Canopy leaves assimilate CO₂ more efficiently than leaves of under canopy. Since the canopy heights of tropical rain forests are high, the knowledge on the rate of photosynthesis in canopy leaves is limited. Thus, we focused on leaves of tropical canopy plants and measured diurnal changes of photosynthesis and stomatal conductance at Pasoh, Peninsula Malaysia. Access to the canopy level was performed by using a canopy walk way. The maximum photosynthetic rates were within the range detected in a number of temperate evergreen species. The maximum diurnal photosynthetic rate and stomatal conductance occurred in the early to mid-morning and then declined. The midday decrease in photosynthesis was caused by stomatal closure and also by biochemical limitations of photosynthesis. No marked differences in maximum rates of photosynthesis were not observed between dry and wet seasons. Furthermore, no seasonal changes of diurnal trends of photosynthesis and stomatal conductance were detected. From these results, we speculate that the annual photosynthetic rates of canopy leaves in tropical rain forests should be higher than the rates of leaves in temperate forests.

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The specific characteristics of photosynthesis of canopy tree species and other key tree species in Sarawak rain forest were studied with reference to the light adaptation mechanism. The change of the light-photosynthesis curve according to the light gradient from the upper canopy to the forest floor was compared among canopy species, lower layer species, and gap species. Shorea fallax and Dipterocarpus pachyphyllus were selected for the canopy species. Mallotus leptophyllus and Elaeocarpus beccarii for the lower layer species, and Macaranga triloba and Macaranga winkleri for the gap species. The saturation rate of the photosynthesis in canopy species increased with relative light intensity (RLI) and the initial gradient increased with decreasing RLI. They can shift the light photosynthesiscurve from the seedling to the canopy tree, and they can adapt to both shaded and exposed environment. The seedlings can survive on the shaded forest floor with performing the high initial gradient. When they reach the canopy surface, they can perform high values of photosynthetic production by the high saturation rate and strong sun light. The canopy species successfully adapted to the changes of the light environment throughout their life. Both the saturation rate and the initial gradient in lower layer species decreased in the darker environment. They cannot shift the light- photosynthesis curve like canopy species in the darker environment. But they keep the higher light saturation point even in the dark environment. They can respond immediately to strong light of the sunflex and perform high photosynthetic production. This suggests their survival under canopy may depend on the sun flex. The saturation rate in gap species decreased with decreasing RLI but the initial gradient did not increased. They can perform high photosynthetic rates at exposed environment but cannot survive in the shaded environment.

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Mixed dipterocarp forests in Sarawak are the richest tropical rainforests in the world with quite high species diversity of trees. Previously, Sarawak was believed to be under a stable, warm, humid climate throughout the year. Recently, however, it has been found that unstable, global environmental changes such as the El Nino Southern Oscillation have a strong influence even on tropical rainforests in Sarawak and the other regions of South-east Asia. Our research, the Canopy Biology Program in Sarawak, aims to clarify (1) how unstable environmental changes at the global level influence phenology and reproductive systems, from flowering to seed dispersal, of component plants in the mixed dipterocarp forests and (2) how life history strategy and population dynamics of animals that build mutualistic relationships with plants (pollinators, seed dispersers and ant-mutualists) and feed on materials produced by plants (phytophagous animals) are affected by the environmental changes directly or indirectly through plant phenology. The importance of such studies has recently been pointed out by many scientists but technical difficulty inhibits progress of studies because long-term stay on the canopy of the mixed dipterocarp forests that reaches up to 70 m above the ground is quite difficult, although plant reproduction is mostly done in the forest canopy. Overcoming such difficulties, we constructed two tree towers (35 m and 50 m in height) and nine spans of walkway (300 m in total length) in the Lambir Hills National Park in Sarawak, Malaysia, to observe plant phenology and plant-animal interactions. Reproductive and flushing phenology of 485 plant individuals and the seasonal change of insect abundance using various kinds of traps have been monitoring for 30 months. Many new observations on plant-animal interactions have been made; e.g. insect-pollination of Gnetum gnemon, pollination process of emergent trees and epiphytes, behavior of stingless bees, nomadic ants with aphids and so on. Now we intend to clarify the genetic structure of various plants using allozyme and DNA markers, and the mechanisms of the creation and maintenance of biodiversity in the tropical rainforests.

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Though pollinating and wood boring insects play important roles in regeneration and decomposition processes in tropical rain forests, many such insects inhabit the forest canopy. Many methods such as chemical fogging, climbing techniques and large towers or cranes have been used to study canopy insects. A giant balloon air ship to bring researchers on a flexible raft up to the forest canopy was developed by Hallé. However, each method has disadvantages. Tree climbing methods are dangerous and require climbing skills. Building a tower or crane in a tropical forest is costly, disturbs the forest ecosystem and limits the research area. Chemical fogging is inadequate for determining the vertical distribution of insects and also disturbs the natural environment. Hallé’s air ship system is expensive and requires a large number of staff. Therefore an inexpensive and movable balloon system in combination with attractant traps was developed and the effectiveness of the system was examined in a lowland tropical rain forest canopy in Pasoh Forest Reserve, Peninsular Malaysia. The balloons, 2.5 m in diameter, were filled with helium gas for levitation and moored in different directions by three pieces of thin rope. Traps with benzyl acetate and ethanol used as attractants for the pollinators and wood borers respectively were suspended from the balloon at different heights. The balloon system remained effective throughout the ten days that it was in use. The traps yielded beetles from thirteen families, but the dominant flower visiting genera attracted to benzyl acetate were Dasyvalgus, Mecinonota (Scarabaeidae) and Endaeus (Curculionidae), while the dominant wood borer attracted to ethanol was Xylosandrus crassiusculus (Scolytidae). A much larger number of individuals were trapped at 15 m ht. than at 1.5 and 7 m ht., particularly in Dasyvalgus sp.l. The trapping results show that the balloon system can be used for studying canopy insects, especially coleopteran pollinators, and their vertical distribution on a spatial and temporal scale. The vertical distribution pattern obtained by trapping

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In Japan, arboreal arthropod densities have been estimated in various forest types using the insecticide fogging method. In addition, aerial spraying of insecticides has been practiced on a large scale in western Japan since the early 1970›s to control pine-wilt disease caused by the pine-wood nematode. Using these occasions, many estimations of the density of arboreal arthropods in different pine stands have been done.
The densities of arboreal arthropods in pine stands varied greatly ranging from 36.2 to 1,467/m². Densities of arthropods were usually high in evergreen coniferous forests than deciduous broad-leaved forests, probably due to lack of food and shelter in winter on the trees.
Densities of arthropods in a dry (seasonal) evergreen forest in northeast Thailand were estimated at 256.4 and 140.4 in the dry season, and 195.2 and 123.1/m² in the rainy season by fogging method. No distinct differences are recognized between the seasons.
In any case, major components are Collembola and Acari(Oribatei), regardless of the forest type. Many of them evidently go up and come down along the tree trunk between soil surface and canopy.

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In this paper, three-dimensional space use patterns, interspecific interactions, anti-predator vocalizations, and social structures were compared among three species of tree squirrels (Callosciurus caniceps, C. notatus, and C. nigroviUatus) in lowland forests of West Malaysia. These sympatric species had each different space demands in respect of tree height or forest structure, and interspecific interactions were infrequent. Therefore, they were able to coexist in the tropical forests that consist of tall trees and have complex habitat structures. Anti-predator vocalizations and social structures differed among the three species, and this may be correlated to the habitat structure of each species: C. caniceps predominated in a bushy area and more subtly used auditory communication in predator avoidance than did the other two species.

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Although some primate species in Africa and Asia are terrestrial, most primates in the world are arboreal and important consumers in tropical forests. In various habitats, several to ten-odd primate species inhabit sympatrically. Comparative studies of forest utilization of a local primate community are important to focus on relationships of arboreal animal community and plants in tropical forests. Ten species of Neotropical primate are confirmed in a study area in northern Bolivia, and two Callitrichidae monkeys, Saguinus fuscicollis and S. labiatus, inhabit sympatrically in the area. The unit group of both sprecies was a family group consisting of two to seven individuals. Home ranges of the family groups of both species were overlapped and the two species frequently made polyspecific associations, but both species preferred. different layers of the forest for traveling and showed different foraging behaviors in the study area. S. fuscicollis tended to utilize the lower layer of the forest, jump from a trunk to a trunk for traveling and forage large-size invertebrates, whereas S. labiatus mainly utilized the middle layer of the forest, jumped from a branch to a branch and foraged small-size invertebrates. Seven species of Cebidae monkeys were distributed in a study area of the Macarena National Park in the upper River Duda Basin in Colombia. Callicebus moloch and Cebus apella usually moved in the lower layer of the forest and used small-size trees for traveling, whereas Alouatta seniculus and Ateles belzebuth tended to use the higher layer of the forest and used large trees for moving support and resting in the area. Differences of height preference in forest utilization, traveling mode and foraging behavior are usually recognized in sympatric monkeys, and small-size species tend to use the lower layer than large ones. Cebidae monkeys inhabit from Argentina to Mexico, but the distribution area of Callitrichidae monkeys is restricted to lower latitude area and the range of genera of the family is bordered by major rivers in the Neotropical area. The author considers that the distribution pattern of both primate families and the differences of forest utilization of a primate community are prescribed by recent species compositions and forest types that were determined by refuge distribution of the tropical humid forest in the last ice age in the Amazon area.

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