The taungya method is usually defined as a reforestation method in which tree seedlings and agricultural crops are simultaneously planted at the initial stage of reforestation until the amount of crop harvest decrease due to crown closure. After that only the trees are left, with the final aim to establish man-made forests. The reforestation method “Yakihata-zorin (Kobasaku or Kirikaebata) in Japan is virtually the same as the taungya method and dates back to the early 1700s prior to establishment of the taungya method in Burma (Myanmar). This method is still being practiced in the Sampoku region, Niigata prefecture. At present, instead of buckwheat or millet, red turnip (Brassica campestris var. glabra), which is processed into pickles, is cultivated with Sugi (Cryptomeria japonica) seedlings. When land owners permit cultivation of turnip they can save on land preparation and weeding expenses in the first year and also save weeding costs in the second year by cultivating azuki beans. The yakihata-zorin method practiced in Japan has potential for improvement of taungya method practiced in tropical countries.

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A preliminary survey of abundance and species richness of galling insects on dipterocarps was conducted in the forest canopy and forest floor of the Pasoh Forest Reserve in Peninsular Malaysia. At least 120 individuals and 13 sorts of galls were collected from canopy crowns of 15 of 26 dipterocarp trees (10 species) surveyed. In contrast, only one individual coccoid gall was found on the forest floor, despite careful searches of about a hundred seedlings, saplings, and young trees. This result shows that galls on dipterocarps are concentrated in the forest canopy, where young shoots suitable for gall induction and development are abundant. Although insect inhabitants obtained from the galls were not numerous, most of the galls were supposed to have been induced by dipteran or hymenopteran insects, and the rest proved to have been caused by beesoniid coccoids (Homoptera). This study suggests that dipterocarps harbor diverse galling insect species, of which the main domain is in the forest canopy.

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The floristic composition, woody species diversity, and spatial distribution of trees in a subtropical evergreen broadleaf forest on Ishigaki Island, Japan, were investigated based on architectural stratification. Five architectural layers made up the forest stand. The floristic composition was almost similar between the third and the bottom layers, whereas it was almost exclusive between the top and the lower four layers. The fourth layer contained the highest potential number of species (90). Castanopsis sieboldii, Daphniphyllum teijmannii, Neolitsea aciculata, and Distylium racemosum were typical facultative shade species that appeared in all layers. Ardisia quinquegona was the most dominant species, as it had the highest importance value at the stand level; it was also considered a small climax species because of its disappearance in the top layer but higher importance value in the lower four layers. The values of Shannon’s index H’ and Pielou’s index J’ were 4.36 bit and 0.69, respectively, for the entire stand; these values tended to increase from the bottom layer upward, except for the H' -value of the top layer. Furthermore, woody species diversity was higher in the upper strata than the lower strata. The spatial distribution of trees was random in each layer, except in the bottom layer where trees were aggregately distributed. The degree of overlap in tree habitats differed among layers, and the results suggested that trees in the second layer could capture moderate light, while light could not easily penetrate the lower three layers. Therefore, most species in the lower layers must be shade-tolerant. The mean tree weight of each layer decreased from the top layer to the bottom layer, whereas the corresponding tree density increased. We concluded that this trend might be a general phenomenon in subtropical evergreen broadleaf forests of the Ryukyu Archipelago, and we designated this trend as the quasi mean tree weight-density trajectory of forest stratification. The relationship of mean tree height to tree density for the upper two layers supported Yamakura’s quasi -3/2 power law system.

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This study was conducted in order to evaluate the vegetation conditions and soil fertility status of fallow lands under intensive shifting cultivation systems in the Engkari river area in Sarawak, Malaysia. The shifting cultivation by the several Iban communities selected at Engkari area for upland rice farming were currently being conducted with 2 to 7 years of continuous cropping followed by 1 to 6 years of fallow with application of chemical fertilizers and agrochemicals. Since agricultural management methods and land productivity under the current shifting cultivation systems conducted by the Iban farmer were our concerns, we carried out vegetation and soil surveys on fallow lands of which suitability for rice cropping using shifting cultivation had been classified by Iban landowners from their knowledge of vegetation conditions; 20 suitable and 20 unsuitable sites were analyzed. The results of our vegetation survey showed no substantial differences between suitable and unsuitable sites in the species composition and the sizes of tree species, as measured by the stem diameter at breast height (DBH). The plant density of grass and fern groups tended to be higher in most of the sites even after extensive fallow duration. As compared to our previous studies, the DBH of the trees in most of the Engkari area study sites was small even after extensive fallow duration. The soil properties in the study sites could be characterized by a strongly acidic nature with low levels of exchangeable bases. No substantial differences were found in the soil properties in terms of site suitability and fallow duration. Our results suggest that the rationality of farmers’ traditional knowledge related to vegetation-based site selection is no longer applicable under intensive shifting cultivation practices in the Engkari area. Considering the high acidity and poor nutrient contents of the soils, as well as poor aboveground biomass added to soil as ash during burning, certain measures will be necessary for the farmers in the Engkari area to continue rice cropping through the intensive shifting cultivation system. These include effective types of fertilizer and appropriate application methods as well as countermeasures to soil erosion in order to prevent the loss of fertilizer nutrients from soil ecosystems.

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Dendrographic records for four tropical rainforest trees, collected by Drs K. Yoda and H. Sato at the Pasoh Forest Reserve in June 1971, suggested the rhythmic diurnal changes in trunk radii. The Fourier transform (FT) was applied to the radius oscillations of the four sample trees for understanding the trunk behavior in frequency domains. The maximum FT amplitude occurred at a specific frequency (f^*) of 0.0469 h^-1 in all trees and suggested consistent diurnal changes in trunk radii, although f^* = 0.0469 ^-1 does not correspond to the ideal period of 24 h. The phase angle at a given frequency (f), or θ_i(f), for an individual tree with identification number (i) was not significantly correlated with θ_i(f) for another individual with the identification number j (i≠j, p> 0.05). Autocorrelation coefficients between θ_i(f) and θ_i(f + Δf), designated with f and the lag frequency Δf, were not significant for most Δf, suggesting a lack of order in θ_i(f) with respect to f. The frequency distribution of θ_i(f) followed a uniform distribution within the range of ±π(± 12 h d^-1), where π is the circular constant. These traits of θ_i(f) associated with trunk radii corresponded well with the traits of a different θ_i(f) calculated from sap flow sequences of conifers, implying temporal partitioning of soil-water resources among trees. The ecological significance of temporal resource partitioning on an hourly basis within small land areas is discussed with reference to hydraulic architecture and hydraulic lift (or redistribution), which are known to be important mechanisms facilitating the coexistence of competing plant species or individuals within a forest stand.

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The guild composition of a hill dipterocarp forest was examined using growth traits of 1566 trees comprising 422 species through field observation at a 6-ha plot for 6 years in Sumatra. Three parameters, intrinsic growth rate, attainable maximum stem diameter, and stem hardness, were used for guild determination. The intrinsic growth rate showed a significant correlation with stem hardness, which suggested a trade-off between volume growth and architectural strength under the restraint of photosynthetic products. Four major guilds were determined, characterized as Soft wood-Small size-Fast growth, Soft-Big-Fast, Hard-Big-Slow, and Hard-Small-Slow traits. Ecological niches of these guilds were related to the large variance of resources in time and space of a tropical rain forest. A secondary forest part in the 6-ha plot retained high species diversity, but species composition was largely different from that of the mature stand. Human activities biased guild composition to reinforce the Soft-Small-Fast guild, with a reduction in the Hard-Big-Slow guild that included many marketable timber trees. Logging impacts on dipterocarp and fagaceous trees were assessed with reference to their spatial distribution and attributes of guilds.

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Intensification of farmers’ land use with perennial crops is expected to prevent the destruction of forests caused by their extensive slash-and-burn cultivation in the tropics. However, effects of tree crops on natural forests are controversial, affected by various socio-economic factors. This article discusses impacts of farmers’ crop cultivation on natural forest conversion by examining a case study from West Sumatra, Indonesia. Sample farmers cultivated lowland paddy fields and upland non-paddy fields. They cleared natural forests merely to grow perennial cash crops such as coffee, rubber, and cinnamon, some of whom may have migrated to forest areas. Coffee was productive in assarted plots that sample farmers originally converted from natural forests, as preferring pristine soils. Rubber and cinnamon occurred commonly in plots outside forests that other farmers already cultivated and transferred to sample farmers with considerable profits, though planted on assarted plots as well. Single or mixed cultivation of these tree crops was not yet optimal, incurring land degradation at times. Some farmers grew profitable but laborious non-rice food crops on small lowland fields by converting insufficient paddy fields, encouraged by good markets. Their concentration on lowland farming alleviated destruction of upland natural forests noticeably. Farmers utilized profits from surplus rice harvests to expand tree crop cultivation in upland forest areas for future income, while substituting non-rice food crops for lowland rice for their subsistence. Perennial cash crops generally aggravate farmers’ forest clearance rather than commercial non-rice food crops grown intensively outside forests. However, impacts of different tree crops vary on forest conversion. Fast-growing pioneer tree crops like coffee bring about more extensive conversion than slow-growing follow-up tree crops like rubber or cinnamon which can be grown in any land conditions. Forest clearance for tree planting could be alleviated by intensifying farmers’ land use outside forests through flexible combination of tree crops and food crops adaptive to various land conditions, provided substantial crop profits and equitable land allocation.

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