Peat fire in tropical peatland not only releases a large amount of carbon into the atmosphere, but also causes significant damage to peatland ecology and the landscape. It is important to understand peat fire and to establish more effective methods to control peat fire. In this paper, the results of field and laboratory research elucidate the combustion and thermal characteristics of peat fire. Field studies were carried out at 9 study plots in actual peat fire areas along the Trans Kalimantan Highway of Central Kalimantan in 2002. Laboratory analyses using a bomb calorimeter and TG-DTA were carried out to obtain low and high ignition temperatures and calorific values of various peat fire fuels. Results of field studies on weather conditions, temperatures in peat layers during fire, patterns of peat fire fronts, peat fire spreading speeds, fuel composition, moisture contents and fuel losses during fires are described in this paper. This study clarified the nature of fire movement and the smoldering process in an actual peat fire in tropical peatland. Based on our results, a more effective method for controlling peat fire can be developed.

抄録全体を表示

An investigation was conducted on Kandelia candel plantations in Namdinh Province, Northern Vietnam to elucidate the influences of stand-age and inundation on carbon accumulation in mangrove soil. The research plots were set according to stand-age and inundation. Carbon accumulation in the soil was estimated. There was a depth-related distribution of C content in mangrove soil. In the surface soil layer, carbon content seemed to increase gradually with the growth of mangroves. It was implied that the vertical profile of C content might reflect potential carbon accumulation caused by the former mangrove vegetation, decomposition of subsurface accumulation induced by root development of newly planted mangroves, and re-accumulation of organic matter from new plantations. Carbon accumulation of the studied mangrove area was considerably high, ranging from 71 to 82 ton C ha^-1. The total C accumulation (including plant C) appeared to increase exponentially with vegetation age, with an annual rate of 9.7 %. The effect of stand-age could be explained by biomass and anaerobic decomposition that occurred in the sediment. Results of this survey concerning inundation clearly show that carbon accumulation in the soil of a plantation grown in low intertidal elevation was high and low in mangroves grown in high intertidal elevation. Different inundation conditions would cause different biomass and anaerobic conditions. Thus, inundation plays an essential role in the process of carbon storage in mangrove soil.

抄録全体を表示

Multivariate profiling of soil bacterial communities provides information that will possibly contribute to the conservation and rehabilitation of the environment. In the Sakaerat Environmental Research Station, Thailand, the land degradation gradient, represented by a dry evergreen forest (DEF) and bare ground (BG) as a result of deforestation and subsequent land degradation was determined. Profiling was done with the antibiotic resistance most probable number (MPN) method (method 1), the antibiotic disc diffusion method (method 2) and the Biolog method. Compread to the DEF soil, the BG soil had significantly lower moisture content and pH values (at p=0.05), and total C and bacterial MPN count (at p=0.10). Profiles of the soils obtained by the antibiotic and the Biolog methods were analyzed. The profiling methods scored Wilk’s lambda values of 0.001 (method 1, p=0.086), 0.004 (method 2, p=0.157) and 0.000 to 0.110 (Biolog, p=0.040 to 0.708 at 0.2 to 1.4 average well color development values, AWCDs), then gave principal component score plots showing that all the methods successfully determined the degradation gradient with comparable efficiency. Redundancy analysis ordination diagrams for the above data sets indicated that the soil environmental factors that significantly correlated to the bacterial community profiles were: moisture content (p<0.05, method 1); moisture and total nitrogen (TN) contents (p<0.05, method 2); moisture content and C/N ratio (p<0.05, Biolog 0.2 AWCD); moisture and TN contents (p<0.05) and bulk density (BD, p<0.1, 0.6 AWCD); pH (p<0.05, 1.0 AWCD); and moisture and TN contents (p<0.05, 1.4 AWCD). The soil moisture gradient was shown to be the most decisive determinant of the changes in soil bacterial community profile associated with deforestation. The changes in TN, pH and BD were thought to be possible causes and/or effects of the variations of multivariate soil bacterial profiles in association with the degradation.

抄録全体を表示

A fire-history study of the tropical peatland of Central Kalimantan has been conducted using charcoal and organic geochemical analyses. A-153 cm core was taken from Kalampangan. Charcoal analysis and ¹⁴C dating were used to understand the fire pattern, and organic geochemical analysis was used to identify environmental changes caused by fires. The peat formed from 9472 - 8981 to 7624 - 7424 cal. yr BP (calendar years before present) coeval with the development of the wet and warm climate of the Southeast Asia region. Fire frequently occurred in the study area during the peat formation. The fire intensity must have been low to have allowed continous peat formation. The record indicated that two comparatively severe fires, or fire periods, occurred in the study area between ca. 7500 and ca. 7600 cal BP and between ca. 6400 and ca. 6500 cal. yr BP. In addition, several fires caused nitrogen loss from the peatland and destroyed the plant communities. Re-established plant communities gained nitrogen for photosynthesis from the atmosphere through bacterial fixation. As a consequence, low quality litters with more negative δ¹⁵N were produced.

抄録全体を表示

Crown architecture of a ginger, Alpinia scabra (Zingiberaceae), was studied on Mount Halimun in a tropical submontane forest in West Java, Indonesia. An aboveground shoot of A. scabra consists of one pseudostem and many leaves distributed along the pseudostem. The pseudostem is up to ca. 2 m long. The number of nodes per pseudostem increases, up to 25, with increasing pseudostem length. Pseudostems of smaller A. scabra stand vertically, while those of larger A. scabra bend. On the contrary, the leaf surface is horizontally oriented, irrespective of the pseudostem angle at each node. The horizontal orientation of leaf surface is thought to be effective for capturing the most light per unit leaf area. The internode length decreases from the base of the pseudostem to the tip, i.e., the internode length decreases with increasing pseudostem length, accompanied with stem bending. The ontogenic changes of leaf size in large individuals of A. scabra show that leaf size increases from the base of the pseudostem to the mid-point of pseudostem, and levels off or slightly decreases thenceforth. Thus, leaves were small near the base, where pseudostems stood vertically, and increased in size with pseudostem bending. The combination of an erect pseudostem and small leaves near the base contributes to less vertical overlap of leaves there. The results of this study suggest that A. scabra distributes leaves for efficient light capture by adjusting the internode length, leaf angle, pseudostem angle, and leaf size along the pseudostem.

抄録全体を表示

Degrees of genetic variation accumulated in four dipterocarp species in Lambir Hills National Park, Sarawak, Malaysia were estimated and compared with those in a man-made forest in Bakam Experimental Reserve using microsatellite and AFLP markers. By using 2 to 3 microsatellite loci, 9 to 14 alleles were detected. The average observed heterozygosities for Dryobalanops lanceolata, D. aromatica, Shorea beccariana and S. macrophylla in the natural population were 0.400, 0.400, 0.580 and 0.516, respectively, and expected heterozygosities were 0.603, 0.461, 0.685 and 0.745, respectively. In all of the four species, excess homozygotes were observed. Significant deviation from the Hardy-Weinberg equilibrium was detected in D. lanceolata and S. beccariana. AFLP analysis in the natural population revealed that 94.6 to 99.7% of the fragments were polymorphic. The average heterozygosities for these species were 0.220, 0.232, 0.221 and 0.211, respectively. These values were much larger than those obtained in tree populations such as Japanese beech and Japanese oak populations in temperate deciduous broad leaf forests.
Genetic variation in the artificial population was compared with that in the natural population. Both the average expected heterozygosities and the number of alleles in the microsatellite loci were reduced in the artificial population. Some distortions such as linkage disequilibrium and the deviation from the Hardy-Weinberg equilibrium appeared in the artificial population of S. beccariana. The use of seeds collected from a limited number of mother trees to make the experimental site is thought to be the cause of the loss of genetic variation.

抄録全体を表示

Taungya teak reforestation in Myanmar has a long history and is considered an exceptionally successful example of tropical plantations. However, after one cycle of taungya teak reforestation, soil quality would deteriorate as large volumes of biomass are removed from the forest ecosystem through the harvesting of teak. Therefore, the recovery of soil productivity during the period of teak growth is crucial to the successive rotation of the system. In this study, the dynamics of soil organic matter (SOM) and litter were investigated during the teak growth period to evaluate the long-term sustainability of taungya teak reforestation from the viewpoint of SOM conservation. Especially, the effect of forest fires on SOM dynamics and litter was investigated. In Kabaung Reserved Forest and Bondaung Reserved Forest, where teak reforestation has been practiced since 1884, surface soil samples were collected from teak plantations of different ages (0-96 years) for total carbon and nitrogen content analyses. In mature teak plantations, litter production and decomposition rates of leaf litter were also measured. Accretion of SOM was not observed in any of the teak plantations, even 96 years after reforestation. This absence of SOM accretion was attributed to the combustion of forest floor litter - a main source of SOM - by forest fires. Given that the occurrence of forest fires overlapped the defoliation period of teak, most of the teak litter that had accumulated on the forest floor was easily burnt. The strong positive correlation between total carbon content and the C/N ratio of surface soil in teak plantations suggested that the effect of forest fires on the long-term dynamics of soil carbon was marked. We conclude that forest fires have a detrimental effect on the long-term sustainability of taungya teak reforestation.

抄録全体を表示

Recovery assessment of the logged lowland dipterocarp forests based on phytosociological studies conducted in the state of Negeri Sembilan, Malaysia, showed that the recovery rate of the logged areas depends on the state and degree of harvesting carried out on the stands. The stands that were harvested from 1963 to 1973 under the Malayan Uniform System (MUS) have shown a relatively slow recovery rate. The sites have small average coverage by emergent (ST) trees, ranging from 8% to 14%, and only a few dipterocarps occupy this layer. On the other hand, the stands harvested in the 1950s have recovered towards their original state prior to harvest. The stands recorded an average ST-layer coverage of 24%, T1 layer (57%) and T2 layer (45%). The analysis of species composition recovery and species abundance showed similar trends, with F50 stands appearing similar to the primary forest. The study shows that it takes at least approximately 40 years for the logged-over stands under the MUS to recover to their original state.

抄録全体を表示

Morphological characters were studied in 90 accessions of Capsicum frutescens in Southeast and East Asia, and cluster analysis was carried out to qualitatively and quantitatively assess the characters. Four major clusters appeared both in the qualitative characters (XA, XB, XC and XD) and quantitative characters (YA, YA, YC and YD), and 90 accessions were classified into 9 types based on cluster combinations. Four major types (XAYB, XAYC, XBYB and XBYD) including 61 accessions were distributed evenly in Southeast Asia. Five minor types, on the other hand, were distributed unevenly: XAYA in the Ryukyu Islands, Indonesia, northern Thailand; XBYA in Indonesia, southern Thailand, Vietnam; XCYD in northern and southern Thailand; XCYD in Vietnam and Laos; XDYD in southern Thailand.
Morphological characters were more diversified in Thailand. This is partly because C. frutescens is used more frequently in Thailand than in other regions. All 17 accessions from the Ryukyu Islands, on the contrary, showed exactly the same qualitative characters and high similarity in quantitative characters. These results agree with the results of biochemical analyses. Accessions from the Ryukyu Islands were both morphologically and biochemically very close to each other, indicating that the Ryukyu Islands is the end of the dispersal route of C. frutescens in Southeast and East Asia.

抄録全体を表示

To estimate the aboveground biomass of tropical secondary forests dominated by pioneer species, allometric equations to relate diameter at breast height with the dry mass of the aboveground organs of several pioneer species were developed. The aboveground biomass of secondary forests was estimated using four methods based on the allometric equations. Biomass estimated with an allometric equation for all species combined was equivalent to that estimated with species-specific allometric equations. However, the estimated biomass based on a general-purpose allometric equation was substantially higher than that using other allometric equations. The allometric equation for all species combined is suitable for estimating the biomass of a secondary forest from the view points of accuracy and labor.

抄録全体を表示

For the assessment and proper use of tropical peatlands, chemical problems such as nutrient deficiencies and toxicities should be solved. The concentration of the essential trace element boron, which is in tropical peat soil, is very low (about 1⁄10 of the cultivated mineral soil in Japan), however, in layers below 40 cm depth of inland peat B is abundantly fixed. The effect of sea water was estimated, because the water soluble Na content in these layers was high and the water soluble Mg/Ca ratio in them was as high as that of sea water. Therefore, in these layers the B appears to be fixing the high levels of B in the sea water. Various gaps have developed in the lower layer of the inland peat indicating that the sea water can infiltrate with the pressure of the flood-tide.

抄録全体を表示