The variation in the morphological and physico-chemical properties of soils of Acacia mangium plantations were studied in South Sumatra, Indonesia in order to understand how these might affect plantation productivity. Representative soils consisting of four high productivity sites (HPS) and five low productivity sites (LPS) were selected. The main difference between the two productivity classes was in subsoil morphology. HPS soils had deep pisoplinthic horizons and were classified into Pisoplinthic Acrisols, LPS soils had shallow plinthic horizons and were classified into Acric Plinthosols. Differences in redox environments and water drainage in subsoil were the most likely factor creating the differences in morphology. Lower Fe_o/ Fe_d values in HPS subsoil indicated that better drainage facilitated the dehydration and crystallization of iron oxides to convert plinthic into pisoplinthic. Productivity of Acacia plantations was correlated with subsoil characteristics. Subsoil of LPS with lower porosity and higher penetration resistance restricted deep root development, and consequently growth of Acacia, while that of HPS with higher porosity did not. The chemical characteristics of soils were also related to Acacia growth; subsoil of HPS had lower exchangeable Al, Al saturation, and higher soil pH; meanwhile T-C, T-N, T-P, available P and exchangeable cations of HPS and LPS were not significant different. Site classification based on subsoil characteristics, especially water drainage, and subsoil management to avoid soil compaction will be crucial for site selection and sustainable productivity of Acacia plantations.

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The application of phosphorus (P) fertilization on industrial tropical leguminous forest plantations may affect methane (CH₄) exchange between the soil surface and the atmosphere, by influencing microbial methanotrophic and methanogenesis activity and root growth. In this study, we examined the effects of P fertilization on CH₄ fluxes in an Acacia mangium plantation in South Sumatra, Indonesia. To understand the role of microbial and plant root activities separately, we prepared both root-excluded and root-existing plots. Two-way (root exclusion and P application) ANOVA showed that P application significantly stimulated the CH₄ uptake at day 106 (P=0.032), and tended to stimulate mean CH₄ uptake during the experiment (P=0.071). The result could be attributed to stimulated methanotrophic activites and/or inhibited methanogenesis activities by P application. However, the change in CH₄ fluxes by P application was not clear in the root-existing plots. These results imply that, in the root-existing plots, the effects of P application might be reduced by P utilization by root or stimulated methanogenesis by increased carbon supply of root residue. We suggest that the effects of P application on CH₄ fluxes in a tropical leguminous plantation are trivial.

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Microfungal populations associated with the domatia and food bodies of Macaranga bancana (Euphorbiaceae) and its obligate symbiotic ant Crematogaster borneensis were examined using culture-dependent methods. Forty-four fungal isolates were obtained and grouped into 15 operational taxonomic units (OTUs): 11 in Sordariomycetes and two each in Dothideomycetes and Eurotiomycetes. Hypocreales sp.3 (OTU3) was the commonest OTU isolated using the moist chamber method, followed by Paecilomyces sp. (OTU7), Chaetosphaeriaceae sp. (OTU10), Botryosphaeriaceae sp. (OTU12), and Aspergillus sp. (OTU15). Hypocreales sp.1 (OTU1) was the commonest OTU isolated by direct inoculation of the food bodies of M. bancana, darkened domatia materials, and ants and scale insects inside the domatia, followed by Hypocreales sp.3 (OTU3) and Chloridium sp. (OTU11). Molecular phylogenetic affinities of the 15 OTUs suggested that the closest relatives of three, nine, and 13 OTUs were known as insect-associated fungi, plant pathogens, and saprobic fungi, respectively. The possible role of these fungi is discussed.

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Epiphytes show complex spatial distribution patterns at various scales, and the description of their distribution patterns, for example, on a tree, is quite difficult. In this study, by using a three-dimensional tree-form mapping method, the tree form of a 47 m-high emergent tree in a tropical montane forest of northern Thailand was measured and reconstructed, and the distribution of epiphytes on the tree was accurately recorded. The epiphytic matter, which consists of epiphytes and canopy humus, on the tree was classified into six types on the basis of its physiognomy, and destructive sampling of the epiphytic matter was performed for each type with three or four replications. The total epiphyte biomass and canopy humus on the tree were 158.2 kg and 381.3 kg, respectively. Approximately 96 % of the epiphyte biomass was concentrated in the tree crown, above 20 m. The distribution of epiphytic matter types was found to depend on branch diameter, and their spatial distribution from the outer crown to the inner crown was visualized on the three-dimensional reconstructed form of the tree.

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