Dipterocarp Forest In Sarawak Research Articles

Erratum to: Dynamics of mineral nutrient storage for mast reproduction in the tropical emergent tree Dryobalanops aromatica

Limitations in resources are considered to be important in mass-fruiting trees, based on the speculation that they need to consume a large amount of stored resources in a very short period. To test this hypothesis, we studied the total reproductive costs per individual of the tree Dryobalanops aromatica (Dipterocarpaceae), and the dynamics of stored mineral nutrients, specifically nitrogen, phosphorus, and potassium; we then estimated the contribution of each of the stored resources to reproduction in a lowland dipterocarp forest in Sarawak, Malaysia. D. aromatica is an emergent and masting tree species, and it produced a large amount of mature fruit in a masting period running 2001–2002. The dynamics patterns were markedly different for each of the stored nutrients. The phosphorus concentration clearly decreased in the branch, stem and root during reproduction, but nitrogen fluctuated by only a small amount in any organ during this period. The potassium concentration fell in all organs during flowering, but even increased during fruit development. Stored phosphorus accounted for 67.7% of the total phosphorus requirements for reproduction, but nitrogen accounted for only 19.7%. Stored potassium did not appear to contribute anything, at least to fruit production. Our results suggest that D. aromatica supplies phosphorus needed for reproduction mainly from stored resources in the tree, unlike nitrogen or potassium. The accumulation of phosphorus could be the decisive factor in the occurrence and frequency of mast reproduction in the relatively poor soil conditions prevailing in the tropical rain forests of Southeast Asia.

Dynamics of mineral nutrient storage for mast reproduction in the tropical emergent tree Dryobalanops aromatica

AbstractLimitations in resources are considered to be important in mass‐fruiting trees, based on the speculation that they need to consume a large amount of stored resources in a very short period. To test this hypothesis, we studied the total reproductive costs per individual of the tree Dryobalanops aromatica (Dipterocarpaceae), and the dynamics of stored mineral nutrients, specifically nitrogen, phosphorus, and potassium; we then estimated the contribution of each of the stored resources to reproduction in a lowland dipterocarp forest in Sarawak, Malaysia. D. aromatica is an emergent and masting tree species, and it produced a large amount of mature fruit in a masting period running 2001–2002. The dynamics patterns were markedly different for each of the stored nutrients. The phosphorus concentration clearly decreased in the branch, stem and root during reproduction, but nitrogen fluctuated by only a small amount in any organ during this period. The potassium concentration fell in all organs during flowering, but even increased during fruit development. Stored phosphorus accounted for 67.7% of the total phosphorus requirements for reproduction, but nitrogen accounted for only 19.7%. Stored potassium did not appear to contribute anything, at least to fruit production. Our results suggest that D. aromatica supplies phosphorus needed for reproduction mainly from stored resources in the tree, unlike nitrogen or potassium. The accumulation of phosphorus could be the decisive factor in the occurrence and frequency of mast reproduction in the relatively poor soil conditions prevailing in the tropical rain forests of Southeast Asia.

Diversity of Bats at two contrasting elevations in a protected dipterocarp forest in Sarawak, Boneo

We present an assessment of the diversity of Bornean bats at two contrasting elevations (119 m and 787 m) in Kubah National Park surveyed between August and December 2006. Three hundred and eighty-two individuals of bats from 26 species representing six families were recorded using 20 mist nets and three harp traps. The most commonly caught bat was 'Hipposideros cervinus' (Gould, 1863) (n = 168) followed by 'Penthetor lucasi' (Dobson, 1880) (n = 55), and they were also the most commonly detected species at low and high elevation sites, respectively. This survey yielded the first recorded specimen of 'Pipistrellus cuprosus' Hill and Francis, 1984 for Sarawak. Analysis of daily cumulative capture rates indicated that further effort at these sites may not yield additional species if sampling techniques and locations are maintained. Species diversity index of Megachiroptera was higher at high elevations (H' = 0.567 versus H' = 0.466) whereas the species diversity index of Microchiroptera was greatest at low elevations (H'= 0.905 vs H' = 1.225).

Spatial and topographic patterns of canopy gap formation in a mixed dipterocarp forest in Sarawak, Malaysia

We observed spatial and topographic patterns of canopy gap formation in a mixed dipterocarp forest over 4 years (1993-1996) (new gaps) and before 1993 (old gaps) in a 24-ha plot in Sarawak, Malaysia. Results showed a much lower canopy gap-formation rate (0.63 gaps ha-1; mean gap area: 49.4 m2 ha-1, gap formation ratio: 0.067% year-1 for ≤2-m gaps) than the range reported for tropical forests in the Neotropics. The spatial aggregation of new canopy gaps and old large-scale gaps on steep back slopes suggests that canopy gaps are closely linked to topography, especially to landslides. Uprooted trees were concentrated on steeper and more concave slopes and at more intermediate elevations than expected by chance, and occasionally caused landslides. Broken trees, including standing dead trees, were distributed at higher altitudes and on more convex slopes than uprooted trees. A variety of species-specific modes of gap makers between the two types of treefall suggest a degree of predictability in the type of treefall that will be present at different topographic positions. The marked differences in frequency distributions of area ratios of ≤2-m gaps to ≤5-m gaps within each gap showed temporal and spatial heterogeneity of vegetation recovery between new and old gaps. Thus, a forest with low gap-formation rates and abundant and nonrandom distribution of small-scale disturbances suggests spatial heterogeneity of vegetation recovery and contributes to a variable distribution of habitat specialists in canopy gaps.

How does Dryobalanops aromatica supply carbohydrate resources for reproduction in a masting year?

The effect on reproduction of the dynamics of resource allocation was studied in an emergent and masting tree species, Dryobalanops aromatica (Dipterocarpaceae), in a lowland dipterocarp forest in Sarawak, Malaysia. Girdling of the reproductive shoots (5 mm diameter) caused an increase in abortion during the flowering period, but did not affect the fruit set at the middle or final stages of seed maturation. In contrast, 50% defoliation significantly affected fruit setting, but had little effect on flowering. The total leaf area of reproductive shoots was significantly correlated with final fruit set and total fruit mass. Control of the carbohydrate supply to reproductive shoots by girdling and defoliation made no difference to fruit size, but the fruit number was highly sensitive to carbohydrate availability. Total non-structural carbohydrate (TNC) decreased during the flowering period mainly in the branch (P<0.05), but fluctuated little in any organs during fruit maturation. Leaf nitrogen and photosynthetic capacity of the reproductive shoots were not significant variables for reproduction. Our results suggest that D. aromatica uses current photosynthates in the leaves of reproductive shoots as a carbon source during fruit development, but requires stored assimilates in the branch for flowering. However, since TNC was still present in all organs even after flowering, our study also suggests that storage of carbohydrate resources might not be the decisive factor in the occurrence or frequency of flowering in this species.

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.

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.

Resource use of insect seed predators during general flowering and seeding events in a Bornean dipterocarp rain forest.

Insect seed predators of 24 dipterocarp species (including the genera ot Dipterocarpus, Dryobalanops and Shorea) and five species belonging to the Moraceae, Myrtaceae, Celastraceae and Sapotaceae were investigated. In a tropical lowland dipterocarp forest in Sarawak, Malaysia, these trees produces seeds irregularly by intensely during general flowering and seeding events in 1996 and/or 1998. Dipterocarp seeds were preyed on by 51 insect species (11 families), which were roughly classified into three taxonomic groups: smaller moths (Trotricidae, Pyralidae, Crambidae, Immidae, Sesiidae, and Cosmopterigidae), scolytids (Scolydae) and weevils (Curdulionidae, Apionidae, Anthribidae, and Attelabidae). Although the host-specificity of invertebrate seed predators has been assumed to be high in tropical forests, it was found that the diet ranges of some insect predators were relatively wide and overlapped one another. Most seed predators that were collected in both study years changes their diets between general flowering and seeding events. The results of cluster analyses based on the number of adult of each predator species that emerged from 100 seeds of each tree species, suggested that the dominant species was not consistent, alternating between the two years.

The diversity of hemi-epiphytic figs (Ficus ; Moraceae) in a Bornean lowland rain forest

The diversity and niche specificity of hemi-epiphytic figs in a lowland dipterocarp forest in Sarawak were investigated in 1998. Twenty-seven fig species (264 individuals, c. 120 ha) colonized a diversity of host taxa (35 families), but densities were very low and only 1.77% of trees> 30 cm d.b.h. were occupied. There were no significant associations with host taxa or host-bark roughness but among 11 common species (≥9 individuals) the distributions of all other parameters (host-d.b.h., height and position of colonization, crown illumination, soil-texture and slope-angle) were significantly different, and we identified five fig guilds. The guilds corresponded to canopy strata, and appeared to reflect the establishment microsite requirements of different species. A fundamental trade-off within the hemi-epiphytic habit was revealed: Species colonizing larger hosts were rarer, because of lower host densities and more specific microsite requirements, but had better light environments and attained a larger maximum size. The single strangler species appeared to escape many of these constraints, and an important source of mortality caused by host-toppling, indicating the advantages of this strategy. Thus, the hemi-epiphytic figs in this community have come to fill a remarkable diversity of niches, despite low levels of competition, through the exigencies of a complex environment. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78, 439–455

Bird‐pollination of threeDuriospecies (Bombacaceae) in a tropical rainforest in Sarawak, Malaysia

Pollination ecology of three Durio species, D. grandiflorus, D. oblongus, and D. kutejensis (Bombacaceae), was studied in a lowland dipterocarp forest in Sarawak, Malaysia, during a peak flowering period when at least 305 species of plants bloomed in 1996. Durio has been reported to be pollinated by bats in Peninsular Malaysia. However, my observations of flower visitors and pollination experiments indicated that two species, D. grandiflorus and D. oblongus, were pollinated by spiderhunters (Nectariniidae) and that the other species, D. kutejensis, was pollinated by giant honey bees and bats as well as birds. Hand-pollination experiments showed that all three species were obligate outbreeders. A resource limitation in fruit production was suggested. The former two species were visited only by spiderhunters, and the bagged flowers that were opened for animal visitors only at night bore no fruit, while those that were opened only during the day bore fruits, at comparable fruiting ratios to open pollination. Durio kutejensis was observed to be visited by giant honey bees, birds, and bats at different times of day, and three series of bagged experiments that exposed the flowers to animal visitors at different times of day bore fruits at a comparable ratio to open-pollination.

Various population fluctuation patterns of light‐attracted beetles in a tropical lowland dipterocarp forest in Sarawak

AbstractThe population fluctuation pattern of light‐attracted beetles was studied from August 1992 to September 1998 (for 73 months) using ultraviolet light‐traps set at three vertical levels in a tropical lowland dipterocarp forest in Sarawak, Malaysia. During our study, a general flowering occurred from April to July in 1996, and flowering on a small scale in 1997 and 1998. We analyzed the data for eight scarabaeid and six meloid species, some of which were anthophilous species. Various fluctuation patterns were observed among the beetle species in aspects of both seasonality and correlation with the supraannual phenological pattern. Three large chafer species (Scarabaeidae, Melolonthini) showed a clear seasonal fluctuation pattern with a peak once from March to May every year, the peak monthly catch greatly fluctuating annually. Other scarabaeid beetles did not show such a clear seasonal population pattern and hardly fluctuated annually. Populations of an anthophilous scarabaeid species, Parastasia bimaculata, a specific pollinator of Homalomena propinqua (Araceae), hardly fluctuated, probably because of its response to the constant flowering of its floral hosts. Monthly catches of an anthophilous scarabaeid, Anomala sp., and meloid beetles showed clear supraannual patterns in response to the general flowering and were significantly correlated with the flowering intensity with or without a lag of a month. The fluctuation pattern of meloids suggests a supraannual population fluctuation pattern of their hosts, i.e., megachilid/anthophorid bees.

Artocarpus (Moraceae)–gall midge pollination mutualism mediated by a male‐flower parasitic fungus

A previously undescribed pollination system involving a monoecious tree species, Artocarpus integer (Moraceae), pollinator gall midges, and fungi is reported from a mixed dipterocarp forest in Sarawak, Borneo. The fungus Choanephora sp. (Choanephoraceae, Mucorales, Zygomycetes) infects male inflorescences of A. integer, and gall midges (Contarinia spp., Cecidomyiinae, Diptera) feed on the fungal mycelia and oviposit on the inflorescence. Their larvae also feed on the mycelia and pupate in the inflorescence. The gall midges are also attracted by female inflorescences lacking mycelia, probably due to a floral fragrance similar to that of male inflorescences. Because of the sticky pollen, dominance of Contarinia spp. in flower visitors, and pollen load observed on Contarinia spp. collected on both male and female inflorescences, Artocarpus integer is thought to be pollinated by the gall midges. Although several pathogenic fungi have been reported to have interactions with pollinators, this is the first report on a pollination mutualism in which a fungus plays an indispensable role. The pollination system described here suggests that we should be more aware of the roles fungi can play in pollinations.

Various population fluctuation patterns of light-attracted beetles in a tropical lowland dipterocarp forest in Sarawak

Various population fluctuation patterns of light-attracted beetles in a tropical lowland dipterocarp forest in Sarawak

Beetle pollination of Shorea parvifolia (section Mutica, Dipterocarpaceae) in a general flowering period in Sarawak, Malaysia

Pollination ecology of an emergent tree species, Shorea (section Mutica) parvifolia (Dipterocarpaceae), was studied using the canopy observation system in a lowland dipterocarp forest in Sarawak, Malaysia, during a general flowering period in 1996. Although the species has been reported to be pollinated by thrips in Peninsular Malaysia, our observations of flower visitors and pollination experiments indicated that beetles (Chrysomelidae and Curculionidae, Coleoptera) contributed to pollination of S. parvifolia in Sarawak. Beetles accounted for 74% of the flower visitors collected by net-sweeping, and 30% of the beetles carried pollen, while thrips accounted for 16% of the visitors, and 12% of the thrips carried pollen. The apical parts of the petals and pollen served as a reward for the beetles. Thrips stayed inside the flower almost continuously after arrival, and movements among flowers were rare. Fruit set was significantly increased by introduction of beetles to bagged flowers, but not by introduction of thrips. Hand-pollination experiments and comparison of fruit set in untreated, bagged, and open flowers suggested that S. parvifolia was mainly outbreeding.

Plant reproductive intervals and pollinators in the aseasonal tropics: a new model

What factors determine reproductive intervals and modes of pollination in plants of the aseasonal tropics? To answer this general question, we present a new explanation for some community patterns of plant reproductive intervals and pollinators observed in a lowland dipterocarp forest in Sarawak, Malaysia, using a mathematical model featuring different display effects for different types of pollinators. Predictions from the model matched with the following observed patterns: (i) flowering intervals were different among forest strata (forest floor < understorey < canopy < subcanopy and emergent), and not in the exact order of stratum height; (ii) among generalist pollinators, the proportion of social foragers was maximum in intermediate forest stratum; and (iii) plants pollinated by specialist pollinators were found on the forest floor and in gaps.

Pollination biology in a lowland dipterocarp forest in Sarawak, Malaysia. I. Characteristics of the plant‐pollinator community in a lowland dipterocarp forest

Flowerings and flower visitors were observed continuously in alowland dipterocarp forest in Sarawak, Malaysia, for 53 mo in1992-1996. Flower visitors of 270 plant species were observed orcollected, and pollinators were assessed by observing body contact tostigmas and anthers. We recognized 12 categories of pollination systems.Among them, plants pollinated by social bees included the largest numberof species (32%) and were followed by beetle-pollinated species(20%). Pollination systems were significantly related with somefloral characters (flowering time of day, reward, and floral shape), butnot with floral color. Based on the relationships between pollinatorsand floral characters, we described pollination syndromes found in alowland dipterocarp forest. The dominance of social bees and beetlesamong pollinators is discussed in relation to the general floweringobserved in dipterocarp forests of West Malesia. In spite of high plantspecies diversity and consequent low population densities of lowlanddipterocarp forests, long-distance-specific pollinators were uncommoncompared with theNeotropics.

Plant–pollinator interactions in the understory of a lowland mixed dipterocarp forest in Sarawak

Pollination biology of 41 plants species of 21 families blooming in the forest understory was investigated in a lowland mixed diplerocarp forest in Lambir Hills National Park, Sarawak. Among these species, 29 species (71%) were pollinated by bees, four (10%) by nectariniid birds, three by small dipterans, and others by moths, butterflies, syrphid flies, wasps, and beetles. The 29 bee‐pollinated species consisted of five distinct pollination guilds: ten species pollinated by medium traplining bees (two Amegilla species), nine by small traplining bees (three halictid and a xylocopine species), two by stingless bees and beetles, seven by stingless bees, and one by megachilid bees. The bees constituting the first two guilds were shade‐loving, swiftly flying, long‐tongued trapliners. Proboscis lengths of these pollinators correlated with flower depth of the host plant. Pollination systems in the forest understory were distinguished from that in the canopy by the prevalence of specific interactions, the number of traplining solitary bees, and lack of pollination systems by mass‐recruiting eusocial bees, large Xylocopa bees, thrips, bats, and wind. These characteristics are largely similar between the Palaeotropics and the Neotropics through convergence of nectarivorous birds (spiderhunters vs. hummingbirds) and traplining bees (Amegilla vs. euglossine bees).

Plant-Pollinator Interactions in the Understory of a Lowland Mixed Dipterocarp Forest in Sarawak

Pollination biology of 41 plants species of 21 families blooming in the forest understory was investigated in a lowland mixed diplerocarp forest in Lambir Hills National Park, Sarawak. Among these species, 29 species (71%) were pollinated by bees, four (10%) by nectariniid birds, three by small dipterans, and others by moths, butterflies, syrphid flies, wasps, and beetles. The 29 bee-pollinated species consisted of five distinct pollination guilds: ten species pollinated by medium traplining bees (two Amegilla species), nine by small traplining bees (three halictid and a xylocopine species), two by stingless bees and beetles, seven by stingless bees, and one by megachilid bees. The bees constituting the first two guilds were shade-loving, swiftly flying, long-tongued trapliners. Proboscis lengths of these pollinators correlated with flower depth of the host plant. Pollination systems in the forest understory were distinguished from that in the canopy by the prevalence of specific interactions, the number of traplining solitary bees, and lack of pollination systems by mass-recruiting eusocial bees, large Xylocopa bees, thrips, bats, and wind. These characteristics are largely similar between the Palaeotropics and the Neotropics through convergence of nectarivorous birds (spiderhunters vs. hummingbirds) and traplining bees (Amegilla vs. euglossine bees).

Concentrations of Chemical Elements in Different Tree Compartments Grown in a Mixed Dipterocarp Forest in Sarawak, Malaysia.

The distribution of mineral elements in different compartments of trees grown in a mixed dipterocarp forest in the Lambir Hills National Park, Miri, Sarawak was studied. 514 samples mainly of leaves, twigs and trunks, partly of roots, barks and litter were collected from 101 different trees of 62 species of 25 families. The samples were analyzed for 28 chemical elements, i.e. N, K, Ca, Mg, Mn, Na, AI, Br, Fe, B, Sr, Ba, Zn, Rb, Cu, Ni, Co, Ti, Sc, Cr, Pb, Ce, Li, As, Cs, V, Mo and Th. Essential elements as N, K, Mg, Mn, Fe, Band Ni showed higher concentrations in the leaves. Ca, Zn and Cu were found significantly higher in the twigs. These elements are known to be related to the auxin metabolism effective to the induction of the cell lignification. The elements with no characteristic concern to any physiological processes behaved as if they underwent passive uptake. The uptake of elements with toxic or negative effects to plants, e.g., AI, Pb or As seemed to be either blocked by the roots or they were safely stored in those organs as trunks and barks. Taken the fact into account that those elements actively associated with plant physiological processes are accumulated in the living plant organs, due attention should be paid to the high concentrations of Ba (Gluta oba), Co (Koilodepas laevigatum, Trigonostemon capilli pes , Allantospermum borneense) or Sr (Koilodepas laevigatum).