A study on forest vegetation along an altitudinal gradient was conducted in Doi Inthanon National Park, Chiangmai, Thailand. The purpose of the study was to elucidate how community characteristics change from lowland to mountain vegetation in the tropical monsoon climatic zone in mainland Southeast Asia by using floristic composition and species abundance data collected from forty five plots at different altitudes and forest types.
Community classification by cluster analysis suggested 45 sample stands to be classified floristically into three forest zones along an altitudinal gradient: (1) lowland forest (400-850 m asl) composed of 2 forest groups: (a) deciduous dipterocarp forest group dominated by Shorea siamensis, Canarium subulatum, and Shorea obtusa and (b) mixed deciduous forest group dominated by Teetana grandis, Xylia xylocarpa, Lagerstroemia calyculata, and Millettia leueantha. (2) Transition forest (850-1,400 m asl), in the intermediate zone between the lowland and montane zones composed of 2 forest groups: (a) pine-dipterocarp forest and pine-oak forest groups dominated by Pinus kesiya, Dipterocarpus tuberculatus, Aporusa villosa, Wendlandia tinctoria, Schima wallichii, and Helicia nilagiriea and (b) lower montane forest group dominated by Schima wallichii, Castanopsis /erox, Castanopsis tribuloides, and Helicia nilagirica. And, (3) montane forest (1,400-2,500 m asl), in the uppermost zone composed of 2 forest groups of both montane forest dominated by (a) Mastixia euonymoides, Castanopsis calathi/ormis, and Drypetes indica and (b) Neolitsea pallens, Actinodaphne henryi, and Rapanea yunnanensis.
Tree density and basal area increases with rising altitude. Diversity of trees sharply increases from the lowland zone to an altitude of 1,800 m asl and gradually decreases at an altitude above 1,800 m asl shown by low species richness indices at high altitudes. In contrast, evenness indices were not greatly different along the altitudinal gradient.

抄録全体を表示

Agroforestry is not a new concept to Sri Lankan people, Intt rather has been a part of their lives for many years. People of Sri Lanka understand the importance of trees for human survival. Therefore, they have protected forests and natural habitats, conserve trees in their farming systems ,and utilize them sustainably. During the past fifty years, Sri Lanka has set up many development programmes, however, little attention was paid to the environment, resulting in environmental damage. However, local people know more about their local environment than far-off government employees, and do realize how to make rational choices. This paper investigates how people in a traditional dry zone village of Sri Lanka use an agroforestry system to meet their needs despite economic and social changes. Research was conducted in Kalegama, in the dry zone of Sri Lanka. Questionnaires, informal discussions, personal observations, and secondary sources were usedfor data collection.

抄録全体を表示

In order to clarify the detailed dynamics of litter production and its nutrient characteristics in a super wet tropical rainforest, a study was conducted using twelve litter traps installed in a one ha study plot at PinangPinang, in West Sumatra, Indonesia. The trapped litter was collected monthly in two different years (December 1997 to November 1998 and December 1999 to November 2(00). The annual mean litter production in 1997/98 was 12.2 Mg ha^-1 and in 199912000 was 11.8 Mg ha^-1, The contribution of leaf litter to the totallitterlall was significantly greater (64.8%) than that of the other components i.e., twigs, branches and fruits. The totallitterlall and leaf litter production ranged from 0.16 to 1.98 and from 0.10 to 1.30 Mg ha^-1 month^-1, respectively, during the two observation periods. The seasonal pattern of leaf litter production showed a strong positive correlation with mean monthly temperature. Since the mean monthly temperature showed a negative correlation to monthly precipitation, the monthly leaf litter production also showed a negative correlation to the monthly precipitation. The negative correlation between leaf litter production and monthly precipitation was, however, less significant than the positive correlation of leaf litter production to temperature. This finding suggests that, although the mechanism is unknown, leaf litter production is strongly regulated by slight fluctuations in monthly mean temperature, within the range of 25-28 °C in this super wet tropical rainforest. A positive correlation between temperature and litter production was also observed for the total litter and for the other litter components. However, the correlation was less significant for these other litter categories than for leaf litter. Among the litter components (leaf, twigs, branches and fruit), leaf litter showed the highest concentration of nitrogen (N), magnesium (Mg) and sulfur (S). The reproductive structure (fruit) had a significantly higher concentration of P and K than leaf litter, but the fruit's concentration of Ca was lower than those of the other components of the litter. The concentrations of Ca in leaf litter showed a positive correlation to rainfall and a negative correlation to temperature, while the concentration of K in leaf litter showed the reverse trend. The trend of N concentration in leaf litter was somewhat similar to Ca. These trends might be due to the effect of dilution on Ca and N, remobilization on N, and the leaching by rainfall on K.

抄録全体を表示

The micro spatial distribution of the litterfall and nutrient flux in relation to tree composition and soil chemical properties was investigated within a one-hectare study plot with 115 subplots (10 m × 10 m) in a super wet tropical rain forest in West Sumatra, Indonesia. Litterfall production and its nutrient flux throughout a one-year period were determined using 63 circular litter traps installed in 63 subplots among the 115 subplots. The aim of this study was to qualify the micro spatial distribution of the litterfall production and nutrient flux in relation to tree composition and soil chemical properties among the 63 subplots within the study plot. To characterize the relationship among the micro spatial distribution of the litterfall, nutrient flux and tree composition and/or soil chemical properties, the correlation coefficients and omega index of Iwao (1977) were determined. The mean litterfall was 11.4 Mg ha^-1 y^-1 and the litterfall varied among the 63 subplots within the range of 7.4 - 16.3 Mg ha^-1 y^-1. The variations in litterfall were positively correlated (P = 0.01) to tree density and the number of tree species in the subplots. Based on the nutrient contents and the production of leaf litter, the nutrient fluxes in the 63 subplots were calculated, and were found to vary significantly within the subplots as follows: N, 54-140; P, 1.4-4.5; K, 8.8-27.5; Ca, 71-207; Mg, 6.2-17.7; AI, 3.2-26.4; Fe, 0.7-3.5; and S, 6.2-16.4 (kg ha-1y^-1). The amount of each nutrient flux was strongly affected by the amount of litterfall production, and was, in turn, positively correlated with tree density and the number of tree species in each subplot. The micro spatial distributions of nutrient flux showed significant positive correlations with the soil chemical properties of total Nand 0.1 M HCl extractable K at the surface (0-5 cm) soil of each subplot. However, for the other major elements such as Ca and Mg, no correlation was shown. The micro spatial tree species diversity, i.e., the number of species per subplot, showed a significant positive correlation to tree density, litterfall production and Nand Ca flux. However, as Kubota et al.(2000) and results in this paper, show, the micro spatial distribution of soil fertility parameters, except for the 0.1 M HCl extractable Fe in topsoil, had a negative correlation to the number of tree species. These results suggest that in this super wet tropical rain forest, tree species diversity with diverse tree nutritional characteristics may contribute to create the diversity of an edaphic niche, rather than increase the soil fertility level through nutrient cycling via litterfall.

抄録全体を表示

Site-independent allometric relationships for above-ground weight were studied for three groups of mangroves: Rhizophora, Bruguiera, and other species. A hundred and one tree samples were collected from five forest sites where a major difference is geographical locality. For stem weight, a site-independent allometric relationship using the variable DBH²H or D_R0.3²H (D_R0.3, = stem diameter at 30 cm above the highest prop root) was attained for each group, because the specific gravity of wood and overall stem shape are identical among the trees of the different sites. Although some mangroves showed difference in specific gravity of wood among different sites, this difference was not large enough to effect the site segregation of the allometric relationship for stem weight. The allometric relationships for the branch and leaf weights of all studied mangroves differed by site when we used DBH²H or D_R0.3²H as an independent variable. However, when we used the stem diameter at the height of the lowest branch D_B as an independent variable, the difference in allometric relationships for both branch and leaf weights among sites became smaller. We discussed the application of the Pipe Model (Shinozaki et ai. 1964) for establishing site-independent allometric relationships common to a variety of geographically distinct mangroves.

抄録全体を表示

Strains of wild rice (Oryza rufipogon) distributed in mainland Southeast Asia have been classified into perennial type and annual type, based on their reproductive systems and habitats. However, only a few attempts have so far been made at evaluating genetic structure within, and among, populations. The purpose of this paper is to analyze the genetic structures of a total of seven wild rice populations in mainland Southeast Asia. These seven populations are composed of three perennial populations and four annual populations. Microsatellite (SSR) polymorphisms were used to estimate dynamics within, and among, populations through several statistical parameters. Results reveal that within-population genetic structures of the two types are different. The outcrossing rate of perennial populations, estimated by fixation index, ranged from 49% to 72%. The outcrossing rate for annual populations varied from 5% to 29%. Genetic variability between the two types, a high degree of gene differentiation was observed among annual populations (C_ST = 0.59) compared with among perennial populations (C_ST = 0.22), due to differential gene diversity within populations (Hs = 0.32 and 0.67, in annual and perennial populations, respectively), as well as gene diversity for all populations (H_T = 0.80 and 0.86, in annual and perennial populations, respectively). SSR analysis revealed that the populations analyzed could be classified into three clades according to their geographic origin: those from the middle Mekong basin, the lower Mekong basin, and the Chao-Phraya basin. The results indicate not only that the mating systems within populations and genetic differentiation among populations are both clearly differentiated between perennials and annuals, but also that geographical differentiation occurs along major river basin systems in mainland Southeast Asia.

抄録全体を表示

We studied the role of adventitious roots in supplying water to Ipomoea pes-caprae growing on sand dunes at Yagaji, Okinawa, Japan. For this purpose, all of the adventitious roots were dug up and the diurnal changes in stomatal conductance (at 7:00, 12:00 and 17:00) and leaf water potential (at predawn and 12:00) were measured at various distances from the taproot in January and June. Digging up roots had significant influences on stomatal conductance (at 7:00 in January and at 17:00 in June) and water potential (except for predawn water potential in January), though no significant differences could be detected in stomatal conductance and water potential between the control and treated plants in other measurements. Moreover, a close linear relationship between water potential and distance from the taproot could not be detected. These results suggest that the adventitious roots are not so useful for supplying water to the mother plant and the demand of water in leaves attached at every position on the vine was supplied from the taproot.

抄録全体を表示