Various adverse soils; peat, podzolic sandy, acid sulfate and salted-affected acid sulfate soils were widely distributed throughout Southern Thailand. These soils were infertile and strongly acidic. Phosphorus fertility of these soils was low due to the low content of available phosphorus (0.31-3.70 mg kg^-1) especially in podzolic sandy soil. Acid sulfate soil and salt-affected acid sulfate soil contain relatively high level of exchangeable Al (13.3 and 9.87 cmolc kg^-1, respectively). However, some native plants; Melaleuca cajuputi, Melastoma malabathricum, Scleria sumatrensis and Oryza sativa grow well in these adverse soils. Since the adverse soils distributed there are phosphorus-unavailable soils. Hence, base on an idea that phosphate-solubilizing microorganism is a key factor for plant growth, such functional rhizospherous microorganisms were screened using modified Pikovskaya's media containing 5 mg l^-1 P in different phosphate forms, Al-PO₄, Fe-PO₄ and Na-phytate, and adjusted pH 4.0. The number of microorganisms in the rhizosphere tended to be lower than in the rhizoplane. Twelve isolates showed remarkable growth performance on these solid media. Among these selected, 5 strains were obtained from acid sulfate soil, suggesting acid sulfate soil-adapting plant is a good source of the phosphate-solubilizing microorganism.

抄録全体を表示

Survivorship and fertility schedules of two phytophagous lady beetle species, Epilachna vigintioctopunctata (hereafter abbreviated as EV) and E. enneasticta (EN), were studied under laboratory conditions in a Sumatran highland (Sukarami, 928 m altitude), Indonesia. In the study area, both species commonly occur together on the same solanaceous host plants such as egg plant and a weed, Solanum torvum. EV frequently reached a high density to deplete the plants, while EN remained at low levels. Duration of immature stages was 32.1 days (EV) and 35.3 days (EN). The mean longevity of EV (125.7 days and 90.8 for males and females, respectively) was much shorter than that of EN (149.6 and 124.4). Females of both species laid eggs until day 120 (EV) and 158 (EN) after emergence. Compared to EV, EN had a lower fertility (472.7 eggs per female vs. 787.2) and longer mean length of generation (T) (92.6 days vs. 72.9). The intrinsic rate of increase (r) of EV (0.082) was higher than that of EN (0.059), resulting from the faster developmental times (immature stages and female pre-reproductive period) and the larger fertility of EV than those of EN. The different r-values between the two species corresponded to the difference in the density levels in the field. We also compared the demographic traits of EV populations between the highland (present study) and lowland (previous study in Padang), and found that the former had longer developmental times than those of the latter but both had similar magnitude of fecundities. The r-value of the former was much smaller than that of the latter because of the longer developmental times due to lower temperature condition.

抄録全体を表示

The fruit visitation patterns of small mammals were investigated by camera trappings on the forest floor in a tropical seasonal forest of Thailand. A total of 3,165 visits were recorded for seven small mammal species. The four Muridae species, Rattus remotus, Niviventer fulvescens, Leopoldamys sabanus and Maxomys surifer, all of which were nocturnal, were almost completely temporally segregated from the tree shrew, Tupaia belangeri, and the two squirrels, Callosciurus finlaysonii and Menetes berdmorei, which were diurnal or crepuscular. We suggest that the temporal segregation reduced the interference competition between the four Muridae species and the tree shrew or squirrel for fruits on the forest floor. In addition, the visitation patterns for fruit species differed among the four Muridae species and between the tree shrew and the two squirrels, suggesting that the variation in the visitation patterns for fruit species helped to facilitate coexistence among these species. In contrast, the two squirrels were similar in their visitation patterns, both temporally and in their choice of fruit species.

抄録全体を表示

The relationships between plant and soil in peat swamp forests in two different growth stages, primary and secondary, were examined by analyzing nutritional characteristics (e.g. N, P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, Mo, Al, B, and Si concentrations) and natural abundances of ¹⁵N (δ¹⁵N) and ¹³C (δ¹³C) of plant and soils. Fifty-two plant species from primary forests and thirty from secondary forests were randomly sampled. Plants in both forests belonged to the phylogenic groups Euasterids II, Euasterids I, Ericales, Eurosids II, Eurosids I, Eudicots, and Magnoliids, which were from a newly evolved order. The results showed that Eurosids I plants in primary forests accumulated higher P, K, Mg, Fe, and B than those in secondary forests.
Other minerals did not limit plant growth at either forest type. For Eurosids I plants nutrients depended on soil K, Mg, and Fe, but for P and B they relied on their own nutrient acquisition. This is similar to other plant phylogenies in both forests whose nutrient contents reflected their own nutrient requirements rather than soil nutrients. Since the leaf δ ¹⁵N of plants in both forests is lower than soil δ ¹⁵N, N₂-fixing microorganism activity may be high. It can be hypothesized that peat swamp forests have developed symbiotic systems with N₂-fixing microorganisms, because of poor N nutrition.

抄録全体を表示

The losses of carbon and nitrogen by the forest fire were measured in a dry dipterocarp forest (DDF), northeast Thailand. Seasonal changes in the aboveground biomass of understorey grass and their nitrogen concentrations were measured. The aboveground biomass of grass was increased from March to July during the rainy season and reached the peak of 5.8 Mg ha^-1 in July. Then, the biomass gradually decreased to 2.5-2.6 Mg ha^-1 at the end of rainy season. The nitrogen concentration in grass biomass decreased gradually from 1.7 % at the beginning of rainy season to about 1 % at the end of rainy season, and dropped markedly to 0.4 % at the burning time in January. So about 60 % of the peak nitrogen mass (45 Kg ha^-1) were lost or retranslocated from the aboveground biomass to belowground. Carbon and nitrogen lost by the forest fire were 2.3 Mg ha^-1 and 28 kg ha^-1, respectively. The occurrence of forest fire synchronized with the senescent period of grasses, resulting in the minor loss of nitrogen in the forest ecosystem.

抄録全体を表示

We studied the growth and leaf demography of tree fern Cyathea spinulosa Wall. ex Hook at a 40 m×100 m plot with 163 tree ferns in lowland of Yakushima Island, southern Kyushu to clarify its life history. The 70 healthy individuals were periodically observed (16 times) from March 1997 to March 2000. The numbers and lengths of leaves on a stem increased with stem length up to 20 leaves of a maximum of 3 m in length. Most sporophylls flushed in spring and most trophophylls flushed in summer, although a few leaves emerged continuously all year around. Leaf death followed the annual pattern of emergence with some delay. Leaf longevity was greater on leaves that emerged in summer than those in other seasons; the average leaf longevity was 7.1 months. The growth rate of the stem decreased gradually as stem length increased; the average annual growth in stem length was 8.9 cm/year. The lifespan of individual tree ferns in Yakushima Island were estimated less than 50 years. The pattern of continuous leaf emergence and the short leaf longevity may result from its pioneer habit in the successional stage.

抄録全体を表示

During January and February 1963, there was some of the heaviest rainfall on record, causing disastrous flooding and numerous landslides in Sarawak. In this paper we assess the damage that this heavy rainfall caused to the mixed Dipterocarp forests of the Lambir Hills in northwestern Borneo. Using aerial photographs taken four months after this period of heavy rainfall (June 1963) and another taken 18 years later (July 1981), we evaluated its impact by examining the spatial patterns and scale of the landslides, as well as the processes of recovery in a 1905.5 ha area. In addition, the relationship between the occurrence of landslides and topography was analyzed in part of the sample area (843 ha). The occurrence of landslides was found to be strongly affected by the monoclinal structure of Tertiary sediments on an undulating, cuesta-like hilly terrain composed of dip and back slopes. Most of the 1963 landslide scars occurred on the back slopes and had an aggregated distribution. The area disturbed by the landslides was 2.5-2.91% of the area of the forest canopy [Landslide Formation Rate (LFR): 0.029 or 0.058% · year^-1]. Mean landslide area is 0.45±0.37 ha (max: 1.93 ha). By 1981 (after 18 years), 2.43% of the total area identified in 1963 as landslide area had been colonized with vegetation and 0.32% of the total landslide area was newly created [mean area=0.23±0.23 ha (max: 1.1 ha)] and mostly expanded from old landslides detected. The area class distribution of the disappeared landslide scars for the period skewed to smaller classes. Calculation of Revegetation Time (RevT) by a transition probability matrix model showed smallest landslide area class (0.4 ha) had re-vegetated 3.86 times faster than largest class (2.0 ha), and the total mean RevT is 16.6±13.2 years. The recurrence of large landslides during a catastrophic event depending on topography, therefore, has important ecological consequences of the accumulation of post-landslide vegetation leading to an increase in successional and non-climax phases in the forests, at the regional level. Thus the catastrophic landslides in 1963 caused disturbance on a considerable scale in the region, but the Total Area Disturbed [TAD=LFR · RevT (or Recovery Time (RecT))] values greatly fluctuated depending on degree of erosional landslide recurrence on particular topography and RevT (or RecT) after landslides.

抄録全体を表示

Pheromone components previously identified in various lymantriid moths were field tested in a trapping experiment near Padang, West Sumatra, Indonesia. Each of ten experimental replicates, consisting of four sticky traps, were deployed in complete randomized block and baited with one of four synthetic pheromone lures. Most interesting results include: (1) significant captures of male Lymantria brunneiplaga in traps baited with (+)- and (-)-xylinalure [(7R,8S)- and (7S,8R)-cis-7,8 epoxy-2-methyleicosane]; and (2) capture of male Lymantria subrosea singapura in traps baited with (+)-disparlure [(7R,8S)-cis-7,8-epoxy-2-methyloctadecane], (+)-monachalure [(7R,8S)-cis-7,8-epoxy-octadecane] and 2-methyl-Z7-octadecene. These results will allow an improve pheromone-based monitoring of L. brunneiplaga and L. subrosea singapura, respectively. Future studies should attempt to obtain virgin female moths of respective species for thorough laboratory analyses and field testing of candidate pheromone components. Males of L.beatrix (2) and Lymantria narindra (1) also responded to (+)-disparlure baited traps.

抄録全体を表示