Mixed Dipterocarp Forest Research Articles

Tree growth is related to light interception and wood density in two mixed dipterocarp forests of Malaysia

Summary The development of simple predictors of tree growth is important in understanding forest dynamics. For this purpose, tree height, crown width in two perpendicular directions, trunk diameter at 1·3 m height (d.b.h.) and crown illumination index (CI) were determined for 727 pole‐sized trees (8–20 cm d.b.h.) of 21 species, on forest dynamics plots at Pasoh Forest Reserve, Peninsular Malaysia and Lambir Hills National Park, Sarawak, Malaysia. A light‐interception index (LI = AcrCI2, where Acr is crown area) was calculated for each tree, and wood density (stem wood dry mass/fresh volume) was estimated for each species from reported values. Diameter growth rates were linearly correlated with LI (mean per species r2 = 0·45, excluding substantially damaged and vine‐covered trees). Among trees of all species, diameter growth rate was highly correlated with LI/wood density. Mean growth rate per species varied 10‐fold among the study species, but increased linearly with mean LI/wood density ratio (r2 = 0·78), consistent with the previous pattern. Thus much of the variability in tree growth rates, both within and among species, can be accounted for by the simple mechanistic assumption that, within a given size class, growth is proportional to light interception/wood density.

Soil Characteristics under Three Vegetation Types Associated with Shifting Cultivation in a Mixed Dipterocarp Forest in Sarawak, Malaysia

In order to provide appropriate soil information for the rehabilitation of tropical rainforest ecosystems, we examined the soil morphological, physico-chemical, mineralogical properties and charge characteristics in a degraded mixed dipterocarp forest with three type of vegetation, namely grassland, secondary forest, and remnant forest in Japan Sarawak Friendship Forest, Sarawak, Malaysia. We compared the soil properties at six representative locations differing in topography and vegetation types, with special reference to the effect of anthropogenic activities on the catenary sequence. All the soils were acidic or weakly acidic. Contents of clay, exchangeable Al, Alo, Ald and Fed and the values of the cation exchange capacity and Al saturation increased with depth. The clay mineral composition was dominated by kaolin minerals. The value of point of zero salt effect ranged from 3.0 to 4.0, indicating that the soil was not yet strongly weathered. A catenary sequence of the soils was observed; softer in soil hardness, higher contents of total exchangeable bases in the lower slope plots than in the upper slope plots and higher values of Feo/Fed in the surface horizon in the lower slope plots than in the upper slope plots. However, the effect of anthropogenic activities was observed; higher contents of total exchangeable bases in the grassland than in the other vegetation types. Based on the stable condition on weathering and erosion, the upper slope plot of the remnant forest exhibited a thicker O horizon, lower Feo/Fed values and a relatively high amount of chlorite. Soil variability should be taken into account for appropriate management of rehabilitation in tropical rainforests.

Resource allocation to reproductive organs during masting in the tropical emergent tree, Dipterocarpus tempehes

Some tree species exhibit large year-to-year variation in seed production, a phenomenon known as masting (Kelly 1994, Kelly & Sork 2002). Even in tropical rain forests, in which the climate is suitable for plant growth all year round with little seasonal variation (Whitmore 1998), there are many reports of masting (Appanah 1993, Hart 1995, Newbery et al. 1998, Newstrom et al. 1994, Wheelwright 1986). In particular, Dipterocarpaceae, the dominant family in lowland mixed dipterocarp forests in South-East Asia, undergo mast fruiting following mass-flowering with strong interspecific synchronization in aseasonal western Malesia (Appanah 1985, 1993; Ashton 1989, Ashton et al. 1988, Curran et al. 1999, Janzen 1974, Medway 1972, Sakai et al. 1999, Whitmore 1998, Wood 1956). In mixed-dipterocarp forests, dipterocarp species contribute more than 70% of the canopy biomass (Bruenig 1996, Curran & Leighton 2000). Masting of dipterocarp species is therefore likely to have a major impact on animal populations, and also on the nutrient cycle in such forest ecosystems by causing fluctuations in the availability of resources (Sakai 2002).

Soil macro-fauna in an Acacia mangium plantation in comparison to that in a primary mixed dipterocarp forest in the lowlands of Sarawak, Malaysia

Summary Sustainable ecosystem management of Acacia mangium plantation, the area of which is rapidly increasing in the tropics, especially in Indonesia and Malaysia, becomes more and more important. In this context, abundance, biomass and vertical distribution of soil macro-invertebrates were investigated in a mature plantation of A. mangium in Sarawak, Malaysia. In the present paper, in order to reveal the changes in soil macro-fauna caused by conversion of natural forests to A. mangium plantations, the results were compared with those from a nearby primary forest. While total abundance of soil macro-invertebrates was similar, total biomass was much larger in the plantation than in the primary forest. The prominent factor for such a large total biomass in the plantation was the high abundance of earthworms, followed by isopods and harvestmen with much smaller contributions. The common feature of the communities of these three taxa in the plantation was the absolute dominance by single species. The dominant earthworm species was of the endogeic type that was absent from the primary forest and thought to be introduced with A. mangium seedlings from outside. The isopod flushed in the plantation was a pill bug that occurred in the primary forest, too, and might have been pre-adapted to the vegetation change. The dominant harvestman in the plantation was of the life form different from that of the other species found, and was thought to be supported by the explosive increase in biomass of earthworm and/or pill bug. On the other hand, communities of termites, ants, fly larvae, click beetle larvae and other beetle larvae were depressed by the vegetation change. Thus the major consequence of the conversion of natural forest to A. mangium plantation was simplification of community structure in many taxonomic groups. The major points of the simplification in turn were the explosive increase in biomass of the soil processing earthworm and the litter processing pill bug which may accelerate the mineralization processes. The need for a careful monitoring on sustainability of soil fertility was concluded.

Short-term drought causes synchronous leaf shedding and flushing in a lowland mixed dipterocarp forest, Sarawak, Malaysia

Tropical rain forests are evergreen and experience a climate suitable for plant growth year round (Whitmore 1998). However, most tropical rain-forest trees display periodic shoot growth (Borchert 1991) and show synchronous leaf flushing at the community level (Itioka & Yamauti in press, Medway 1972, Ng 1981). Synchronous leaf flushing may have a great impact on animal population such as herbivores, because young leaves are suitable food resources for many herbivores (Aide 1988, 1992; Coley 1983, Itioka & Yamauti 2004, Lowman 1985).

Annual water balance and seasonality of evapotranspiration in a Bornean tropical rainforest

This study presents the results of 2 years combined field measurements of water vapor exchange with the atmosphere and simplified model calculations at Lambir Hills National Park, Sarawak, Malaysia (4°12′N, 114°02′E). The study site was located in a lowland mixed dipterocarp forest, a major type of Bornean tropical rainforest, where there is no clear seasonality in environmental factors such as radiation, temperature, vapor pressure deficits and precipitation; instead, unpredictable dry spells often occur throughout the year. Modified [Priestley, C.H.B., Taylor, R.J. (1972). On the assessment of surface heat flux and evaporation using large-scale parameters, Mon. Weather Rev. 100, pp. 81–92] and equilibrium evaporation expressions enabled us to understand further the environmental control of water vapor exchanges with the atmosphere and to produce a complete gap-filled data set of the hydrologic fluxes within this environment. The equilibrium evaporation from a well-watered surface sufficiently reproduced the transpiration rate ( T r ); any discrepancies between the equilibrium and actual evaporation rates were caused by unpredictable intra-annual dry spells, which reduced transpiration. There were some discrepancies during the study period because of exceptional dry sequences, but in normal years the annual transpiration rate can be obtained from the equilibrium evaporation expression. The estimated annual T r (1193.1 mm) and evapotranspiration (1545.0 mm) rates were nearly identical to the highest values reported for some humid tropical forests. Although, there were exceptional dry sequences during the study period, the annual average fraction of available energy dissipated by T r at this site (0.69) was almost the same as the medium value between the dry and wet seasons in Amazonian tropical forests. This implies that the annual dynamics of the latent heat flux for this tropical rainforest are under more humid conditions than those of other tropical rainforests.

Landscape rehabilitation of degraded tropical forest ecosystems: Case study of the CIFOR/Japan project in Indonesia and Peru

Tropical forest area is disappearing at the rate of 13.5 million ha each year, due mainly to clearing for agriculture and shifting cultivation. Timber harvesting results in more than 5 million ha of tropical forest annually being transformed into degraded, poorly managed, logged-over forests. The reduction and degradation caused by anthropological activities affect not only the sustainable production of timber but also the global environment. Accurate scientific information will enable managers to devise silvicultural systems to enhance soil properties and forest resources important for sustainable production and to minimize deleterious impacts of harvesting and short-rotation plantations. Ultimately, rehabilitation can increase the area of forest as well as conserve remaining primary forests and environmental quality. Rehabilitation aims to improve biological diversity, increase commercial value of timber and non-timber products, increase forest functions and improve soil fertility. Technical advances will reduce logging impacts, accelerate natural regeneration and improve species selection, enrichment, sustainable site management, catalytic planting and site evaluation and classification. Socio-economic reform should focus on local community participation and acceptance. The CIFOR/Japan project has undertaken research in many countries to evaluate impacts of harvesting and fires on forest ecosystems and to develop methods to rehabilitate logged-over forests and degraded forestlands in ways that are biologically successful as well as socio-economically acceptable. In Indonesia, CIFOR collaborates with Universitas Mulawarman at the Bukit Soeharto Education Forest, a mixed dipterocarp forest logged by INHUTANI I in 1976. The approach to rehabilitation has been through the “ taungya” system whereby farmers grow annual crops among newly planted trees. With the Instituto Nacional de Investigacion Agraria (INIA), Peru, the project is trialling revegetation of fallow fields abandoned after agricultural use in the Ucayali region of the Peruvian Amazon. There is specific interest in selecting tree species with high economic value that grow rapidly in abandoned agricultural land and on infertile soils. Early results point to promising species. The project also involves small farmers in silvicultural activities and species selection.

Plant reproductive interval and population density in aseasonal tropics

In some tropical areas, annual cycles in the environment and plant phenology are not clearly detectable. In such aseasonal tropics, it was found that plant population density is associated with flowering intervals within the same habitats and within the same pollination guilds, if some conditions are satisfied. This finding is based on observations of flowering phenology of butterfly‐pollinated understory shrubs of the genus Ixora (Rubiaceae) for 36 months in a mixed dipterocarp forest in Sarawak, northwest Borneo. Plants did not receive sufficient pollination services and fruit set was pollination‐limited. Under such conditions, it is theoretically predicted that the plant types that reproduce frequently would have higher population density than those that reproduce less frequently, because common types must avoid competition for pollinators and rare types can have a large floral display by storing resources during long reproductive intervals to attract pollinators efficiently. Observed relationships among plant reproductive intervals, pollinator attractions and population densities in Ixora are consistent with theoretical predictions. Based on the theory proposed in this paper, I discuss a factor promoting diversification of the genus Ixora and other taxa.

Transpiration, canopy conductance and the decoupling coefficient of a lowland mixed dipterocarp forest in Sarawak, Borneo: dry spell effects

Tropical rainforests are among the most important biomes in terms of annual primary productivity and water cycling. However, the materials-exchange properties of Southeast Asian forests in their significant functions are less studied. We investigate key factors controlling materials-exchange, such as canopy ( g c) and aerodynamic conductance ( g a) and the decoupling coefficient (Ω) in an intact lowland mixed dipterocarp forest in Sarawak, Borneo. We operated an eddy covariance system above the canopy to measure canopy transpiration rate ( E c) using an 80-m-tall canopy crane, and made concurrent meteorological measurements. In this region, solar radiation and air temperature have small seasonal variations, and annual rainfall is distributed evenly throughout the year, with some unpredictable intra-annual dry spells. We define three specific periods A, B and C as medium dry, heavy dry and wet periods, respectively, for analyses of the environmental control on E c, according to their dryness level. The mean daily E c, g c and Ω were higher in the wet period C than in the dry periods A and B. Also, each g c in its diurnal variation was much higher in the wet period C than in the dry periods A and B, where diurnal variations of g c were almost the same. Both the value of g c and its sensitivity to environmental variables were higher in the wet period C than in the dry periods A and B. The peak of Ω was higher in the wet period C than in the dry periods A and B because of a higher value of g c in period C. However, the higher values of g c in the wet period C did not cause a higher E c compared to in the dry periods A and B.

Towards sustainable management of mixed dipterocarp forests of South-east Asia: moving beyond minimum diameter cutting limits

Selective logging applied in tropical forests is based on one universal criterion: a minimum diameter cutting limit for all commercial timber species. Minimum diameter cutting limits in mixed dipterocarp forests of the Malesia region lead to high felling intensities (10–20+ trees ha−1). Such extraction rates create massive stand damage (>50% of the remaining tree population), which has a negative impact on the regeneration and growth of many harvested dipterocarp species. As such, the minimum diameter cutting limit approach is seldom compatible with sustainable forest management. Where basic ecological characteristics of the commercial species are considered in timber harvesting prescriptions, mixed dipterocarp forests appear capable of sustained timber yields, habitat conservation, and providing other goods and services. This paper first presents the main silvicultural systems developed in mixed dipterocarp forests of Western Malesia and then reviews current knowledge of dipterocarp biology to finally develop guidelines aimed at improving the ecological sustainability of production forests of Western Malesia. These guidelines, a pragmatic reflection of science and ‘best guess’ judgement, include: (1) integration of reduced-impact logging practices into normal management operations; (2) cutting of eight trees ha−1 or less (with a felling cycle of 40–60 years to be determined according to local conditions); (3) defining minimum diameter cutting limits according to the structure, density and diameter at reproduction of target species; (4) avoiding harvesting species with less than one adult tree ha−1 (diameter at breast height [dbh] ≥ 50 cm over an area of 50–100 ha); (5) minimizing the size and connectivity of gaps (<600 m2 whenever possible); (6) refraining from treatments such as understorey clearing; and (7) providing explicit protection for key forest species and the ecological processes they perform. Further refinement is encouraged to allow for local conditions, and for other forest types.

Sustainable cutting cycle and yields in a lowland mixed dipterocarp forest of Borneo

En nous basant sur un suivi de 6 ans de la dynamique d'une foret mixte a Dipterocarpacees, de Kalimantan Est (1990-1996), nous avons construit un modele matriciel pour etablir la periode de rotation durable en fonction de l'intensite de l'exploitation et des degâts engendres. Les parcelles ont ete classees dans trois groupes de degâts et d'intensites d'exploitation. Le groupe G1 rassemble des parcelles ayant subi des degâts peu importants et ayant conserve une surface terriere ≥ 80 % de l'originale (intensite moyenne d'exploitation = 6 arbres ha -1 ). Les parcelles de G2 ont une surface terriere residuelle variant entre 70 et 79 % de l'originale (intensite moyenne = 8 arbres ha -1 ). Enfin G3 regroupe des parcelles fortement perturbees avec une surface terriere inferieure a 70 % de l'originale et ayant subi une intensite d'exploitation beaucoup plus elevee (14 arbres ha -1 ). Les durees moyennes de rotation dans les trois groupes sont significativement differentes et s'elevent a 27, 41 et 89 ans respectivement dans G1, G2 et G 3. Cependant, les volumes annuels preleves sont statistiquement similaires: 1.6, 1.8 et 1.4 m 3 ha -1 an -1 , respectivement dans G1, G2 et G3. Le modele suggere qu'un cycle de 40 ans, avec une extraction moyenne de 8 arbres ha -1 (60 m 3 ha -1 ) et un volume annuel preleve de 1.5 m 3 ha -1 an -1 constitue la meilleure option permettant d'assurer l'integrite ecologique de la foret, ainsi qu'une production constante et, selon les etudes de couts existantes, economiquement rentable sur le long terme. Ce resultat conforte par ailleurs les etudes precedentes ayant demontre que les degâts d'exploitation ne pouvaient etre reduits de facon significative grâce a l'EFI (exploitation a faible impact) qu'a condition de limiter l'intensite d'extraction a 8 arbres ha -1 . Des regles simples permettent de respecter cette intensite.

Tree species differentiation in growth, recruitment and allometry in relation to maximum height in a Bornean mixed dipterocarp forest

Summary 1 Maximum attainable height varies greatly between tree species in tropical rain forests and covaries with demographic and allometric traits. We examined these relationships in 27 abundant tree species in a mixed dipterocarp forest. These species were monitored over 3 years in two 1-ha plots in western Borneo. A 95-percentile upper height limit was used to represent maximum height, to avoid sample size differences among populations. 2 Average growth rate in trunk diameter was regressed against trunk diameter using a maximum likelihood model and assuming that growth rates were exponentially distributed around the average. Estimated average growth rate at small trunk diameters (up to 11 cm) was independent of maximum height among the 27 species, while the degree of growth reduction at larger diameters was larger for species with smaller maximum height. 3 The recruitment rate efficiency of saplings was negatively correlated with maximum height, regardless of the measure used to assess species abundance. In particular, sapling recruitment per unit basal area declined greatly with increasing maximum height, consistent with model predictions of the traits required for the stable coexistence of species at different heights within the canopy. 4 Allometric analyses showed that understorey species had shorter heights at the same trunk diameter, and deeper crowns at the same tree height, than canopy species. Therefore, understorey species showed adaptive morphology to deep shade. 5 The regressed size-dependent pattern of average growth rate and an assumption that the population was in a steady state readily explained the observed trunk diameter distributions for 21 species among 27 examined. These species, for which the projected size distribution hardly changed when the natural increase or decrease of the population was set at γ = ±0.005 year−1, had mortality rates of more than four times the value of γ.

Regeneration methods for dipterocarp forests of wet tropical Asia

Dipterocarp forests of the Asian wet tropics have a long history of silvicultural research. This paper provides a review of this history and a summary of the ecological principles guiding the regeneration methods used. Dipterocarp forests are here defined as those of the seasonally wet regions of Thailand, Burma, and India, and those that are considered of the mixed dipterocarp forest type that dominate the aseasonal wet regions of Sri Lanka, Malaysia, and parts of Indonesia and the Philippines. Two silvicultural regeneration methods are described, shelterwoods and their variants, and selection systems. Both systems can be justified but emphasis is given to the development of shelterwood and selection regeneration methods that are tailored to the particular biological and social context at hand. The paper concludes with a call for improved land-use planning and stand typing to better integrate service and protection values with those values focused on commodity production. Key words: Dipterocarpus, hill forest, non-timber forest products, polycyclic, regeneration, selection, shelterwood, Shorea

The relationship between N, P returned via litter production and nutrient use efficiency of heath and peat swamp forests in Central Kalimantan

The study of nutrient use efficiency in a heath and a peat swamp forest was carried out in Palangkaraya, Central Kalimantan. There was a stronger correlation in the heath forest between nitrogen and phosphorus in above ground litterfall than in the peat swamp forest, and higher positive correlation between litterfall mass and nitrogen return via litterfall in the heath than in the peat swamp forest, compared to phosphorus. The heath forest used nutrient more efficiently than the peat swamp forest and thus was more efficient in retranslocating nutrients. This phenomenon is important for plants to adapt to the heath forest conditions. Both the heath and peat swamp forests in this study were more efficient in their nutrient use than the mixed dipterocarp forests. There was a specific pattern of NUEP (phosphorus used efficiency): the NUEP was higher when P in litterfall was low, suggesting a seasonal effect. Thus in the heath and peat swamp forests, plants use interesting and important nutrient use strategy to adapt to seasonal change.

Reduced-impact logging in Indonesian Borneo: some results confirming the need for new silvicultural prescriptions

Reduced-impact logging (RIL) and conventional techniques (CNV) were compared in a mixed dipterocarp hill forest in East Kalimantan in three blocks of about 100 ha each. Damage was evaluated using pre- and post-harvesting assessments in 24 one-hectare sample plots. RIL techniques nearly halved the number of trees destroyed (36 vs 60 trees/ha). RIL’s main benefit was in the reduction of skidding damage (9.5% of the original tree population in RIL vs 25% in CNV). Before logging, mean canopy openness in CNV (three plots only) and RIL (9 plots) was similar (3.6 and 3.1%) and not significantly different ( χ 2=2.73, P=0.254). After logging, the mean canopy openness was 19.2% in CNV ( n=9 plots) and 13.3% in RIL ( n=8 plots), and the distributions of the canopy class in RIL and CNV significantly different ( χ 2=43.56, P<0.001). CNV plots showed a higher proportion of measurements in the most open class ≥30% than in RIL. At a larger scale, the area of skidtrail per unit timber volume extracted was halved in the RIL compartment (15 m 2 vs 27 m 2 m −3 for CNV). However, under high felling intensity (>8 trees/ha), both stand damage and canopy disturbance in RIL approached those recorded in CNV under low or moderate felling regime. Over this felling intensity threshold the effectiveness of RIL in reducing tree damage is limited. In mixed dipterocarp forest where harvestable timber density generally exceeds 10 trees/ha, a minimum diameter felling limit is clearly insufficient to keep extraction rates below 8 trees/ha. Based on these new results and previous studies in Borneo, we suggest three silvicultural rules: (1) to keep a minimum distance between stumps of ca. 40 m, (2) to ensure only single tree gaps using directional felling, (3) to harvest only stems with 60–100 cm dbh. Foresters, policy makers and certifiers should consider these as criteria for sustainable forest management. We emphasise the need to expand harvesting studies to look at impacts and trade-offs across larger forest landscapes, to expand RIL beyond silvicultural concepts and to include the maintenance of other forest goods and services.

HABITAT PATTERNS IN TROPICAL RAIN FORESTS: A COMPARISON OF 105 PLOTS IN NORTHWEST BORNEO

Understanding the maintenance of high tropical tree species diversity requires disentangling the effects of habitat vs. geographic distance. Using floristic, topographic, and soil nutrient data from 105 0.6-ha plots in mixed dipterocarp forest throughout Sarawak, Malaysian Borneo, we explore the degree to which floristic patterns are habitat-driven from local to landscape scales. We assess how the floristic influence of geographic distance vs. abiotic factors varies from local to regional scales. We employ several multivariate analytical techniques and perform a hierarchical clustering of the research plots using the Steinhaus index of floristic dissimilarity, as well as Mantel analyses on matrices of floristic, habitat, and geographic distance. These analyses indicate that floristic variation is more strongly correlated with habitat than with geographic distance on the regional scale. On the local- landscape to community scale, we find evidence of a resource threshold above which habitat effects weaken; that is, below the resource threshold floristic similarity between sites is dominated by habitat effects, while above the threshold floristic similarity between sites is dominated by geographic-distance effects. We also find evidence that topography and soil nutrients correlate in part independently with floristics. These results, together with previous studies in the Neotropics, emphasize that tree species distribution and community com- position are variously influenced by the interplay of both habitat and dispersal-driven effects.

Foraging activity and pollen diets of subterranean stingless bee colonies in response to general flowering in Sarawak, Malaysia

General flowering is a type of supra-annual mast flowering at community level in South- east Asia, which occurred in 1996 after a four-year interval in northern Sarawak, Malaysia. To exam- ine foraging responses to general flowering, foraging activity and pollen diets of subterranean stingless bee (Trigona spp.) colonies were compared over 3 periods in 1994 and 1996. Among vari- ables of foraging activity (frequency of forager returns, proportions of nectar and pollen foragers), only the frequency of forager returns was significantly higher in 1996 than in 1994. The proportion of nectar foragers differed significantly among periods within a year. Among variables of pollen diet breadth (pollen type richness, diversity and evenness indices), none differed significantly between years or among periods. Pollen diet similarity between colonies did not differ significantly between years, although it differed among periods. lowland mixed dipterocarp forests / foraging / general flowering / nectar / pollen diet / Sarawak / Trigona

General flowering in lowland mixed dipterocarp forests of South-east Asia

General flowering in lowland mixed dipterocarp forests of South-east Asia

General flowering in lowland mixed dipterocarp forests of South-east Asia

The general flowering (GF) events of forests in south-east Asia are perhaps the most spectacular phenomena in tropical biology. GF events occur at multiyear intervals. In GF, most dipterocarp species and many plants of other families come into flower and set fruit massively; these species and plants rarely flower except during GF events. GF is unique, because it can occur over thousands of kilometers and involve hundreds of plant species representing diverse families and lifeforms. It also involves strict mast fruiting. Satiation of generalist seed predators has been considered a primary force for GF. However, recent observations indicate that several selective agents rather than a single major factor may shape GF. In addition to the satiation of generalist predators, promotion of pollination could be one of the selective factors for GF, since synchronized flowering of many species causes an increase in pollinator activity through immigration and population growth. Although environmental prediction for better establishment of seedlings may also be involved in GF, no field data have been reported to support this idea. Long-term monitoring and further understanding of GF are essential for the conservation of this unique and diverse tropical forest in south-east Asia, especially in a period of global climatic change. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 75, 233–247.

North—South Patterns within Arboreal Ant Assemblages from Rain Forests in Eastern Australia1

ABSTRACTThis paper describes the ant assemblages sampled from rain forest canopies ranging from southern Victoria through to Cape York Peninsula, Australia, and also in Brunei. Specifically, it examines the influence of decreasing latitude and variations in elevation on the character, richness, and abundance of the arboreal rain forest ant fauna, and also the relative contribution of ants to the total arthropod community. The sites that were examined included: cool temperate Nothofagus cunninghamii forest from a range of locations in Victoria; cool temperate N. moorei forest at both Werrikimbe and Styx River, New South Wales; notophyll vine forest in Lamington National Park, southeast Queensland; high elevation notophyll vine forest in Eungella National Park, central Queensland; complex notophyll vine forest at Robson Creek, Atherton Tablelands, north Queensland; complex mesophyll vine forest at Cape Tribulation, north Queensland; and mixed dipterocarp forest in Brunei. Although these sites represent a gradient increasingly tropical in character, botanically speaking, Eungella is less tropical than Lamington because of its high elevation. All samples were obtained by fogging the canopy with a rapid‐knockdown pyrethrin pesticide. In all cases, circular funnels were suspended beneath the foliage of individual trees or small plots of mixed canopy. Arthropods were collected four hours after fogging. Following ordinal sorting, ants were identified and counted to morphospecies level. The resulting catch were then standardized across sites as numbers caught per 0.5 m2 sampling funnel. Generic and species richness were higher at the lowland tropical Cape Tribulation sites than at the sites to the south and was comparable with values in the Brunei site. Species richness was negatively correlated with latitude and elevation. Within the Australian rain forest, the lowland/highland break appears to be the strongest predictor of ant relative abundance, with a weaker latitudinal relationship superimposed.