Distribution of colluvia and saprolites and their physical properties in a zero-order basin in Okinawa, southwestern Japan

Ohnuki, Yasuhiro; Terazono, Ryuichi; Ikuzawa, Hitoshi; Hirata, Isao; Kanna, Kensaku; Utagawa, Hirokatsu

doi:10.1016/s0016-7061(97)00076-1

Cited by 13 publications

(15 citation statements)

References 8 publications

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“…The microtopography of the habitat in which the host trees were located was defined on the basis of data collected previously (Sato et al 1999), namely: crestslope, upper sideslope, lower sideslope, headmost wall, head hollow, footslope, and bottomland (Tamura and Takeuchi 1980;Tamura 1987;Ohnuki et al 1997; Fig. 1).…”

Section: Host Tree Traits and Epiphyte Species Richnessmentioning

confidence: 99%

Host trait preferences and distribution of vascular epiphytes in a warm-temperate forest

2008

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To illustrate the ecological factors and process leading to the observed diversity patterns of vascular epiphytes, we examined the effect and importance of host tree traits on epiphyte richness and spatial aggregation of epiphytes. The study was conducted in warm-temperate forest in Japan. The recorded host traits were diameter, height, species, habitat topography, and growth rate, and we analyzed the effects and importance of these traits on three species groups: total epiphytic species, epiphytic orchid species, and epiphytic pteridophyte species. Diameter and species of host trees had the greatest influence on epiphytes and their magnitudes were roughly similar in all species groups. Growth rate and topography were less important than host size and species. Growth rate had a negative effect on all three groups, and topography was important for pteridophytes. Epiphyte richness did not exhibit clear spatial aggregation. Our results suggest that size, stability, and quality of the host are equally important in determining epiphyte colonization.

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Section: Host Tree Traits and Epiphyte Species Richnessmentioning

confidence: 99%

Host trait preferences and distribution of vascular epiphytes in a warm-temperate forest

2008

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“…In temperate humid Japan, several studies have examined the distribution of soil thickness (colluvium C saprolite) and soil physical properties in small basins in coniferous and deciduous forests (e.g. Ohnuki et al, 1994Ohnuki et al, , 1997Ohnuki et al, , 1999. However, soil thickness or soil hardness data for the Mekong River Basin have been lacking.…”

Section: Introductionmentioning

confidence: 99%

“…Considering these limitations of field methods, we investigated the structure of soil layers using a handy dynamic cone penetrometer (Iida and Okunishi, 1983;Onda, 1992;Ohnuki et al, 1997Ohnuki et al, , 1999, often used in landslide surveys in Japan. By applying this method at many points, areal interpretations of the internal structure of an unchannelized valley can be made.…”

Section: Introductionmentioning

confidence: 99%

Distribution and characteristics of soil thickness and effects upon water storage in forested areas of Cambodia

Ohnuki

Kimhean

Shinomiya

et al. 2008

Hydrological Processes

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Abstract:Soil layers play an important role in hydrological processes, particularly in forested basins. For example, thick soil layers can store rainwater temporarily and drain it gradually. In the Mekong River Basin, especially in Cambodia, evergreen and deciduous forests are widely distributed. However, we have no data on soil conditions such as thickness and hardness that affect water storage capacity in forested areas. To clarify the water storage role of forest soils in the lower reaches of the Mekong River Basin, we investigated the distribution of soil thickness using a handy dynamic cone penetrometer in three Cambodian provinces: Kampong Thom, Kratie, and Mondul Kiri. Soil thickness was greater than 8 m in a deciduous forest in Kampong Thom. In some evergreen forests, apparent soil thickness varied from the rainy to dry seasons because of specific grain size distributions; for example, the soils were rock hard in the dry season and soft in the rainy season. In Kratie, deciduous forests prevailed and soil thickness was shallow at less than 3 m. In Mondul Kiri, forests were mainly formed on a basaltic plateau, and soil thickness was greater than 7 m. Soil thickness and hardness differed among the soil types in these three provinces, as did water storage capacity. The maximum water storage capacity was 1350 mm in an evergreen forest distributed on Acrisols in Kampong Thom. In contrast, the minimum water storage capacity was 225 mm in a deciduous forest distributed on Leptosols in Mondul Kiri. We constructed a soil thickness map for the study area in Kampong Thom that was mainly covered with evergreen forest; the distribution of soil thickness was related to elevation, with soil thickness increasing 0Ð13 m per 1 m increase in elevation, except in a deciduous mixed swamp forest area.

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“…Yellow soils are found on crest slopes, upper side slopes and head hollows. Surface-gleyed red and yellow (Ohnuki et al 1997). …”

Section: Area Descriptionmentioning

confidence: 99%

Experimental studies on rain splash erosion of forest soils after clearing in Okinawa using an artificial rainfall apparatus

Ohnuki

Shimizu

2004

Journal of Forest Research

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The main island of Okinawa, in southwestern Japan, is characterized by a subtropical climate, coral reefs, and "reddish soils," which contain Acrisols and Cambisols (FAO/UNESCO classifications). Recently, due to soil erosion on hilly lands, the coral reefs have been damaged by an inflow of reddish soil. Forest clearing is thought to one of the factors increasing rain splash erosion rates on hilly lands, because it is believed that clearing disturbs the forest floor and causes the supply of litter to stop. After clearing, A0, A and B horizons will be denuded, one after the other, by rain splash. In this study, we measured rain splash erosion rates of undisturbed samples of A0, A and B horizons using an artificial rainfall apparatus. The results of experiments on rain splash erosion clarified several aspects of the erosion process in a clearing site. First, it was found that the rain splash erosion rates were higher in fresh litter than in decomposed litter, in decomposed litter than in the A horizon, and in the A horizon than in the B horizon. Thus, the erosion rate increases with soil depth. Secondly, surfacegleyed red and yellow soils are mostly vulnerable to rain splash erosion. The erosion rates of these soils are two to three times higher than those of the red soil and the yellow soils. Thirdly, the erosion rates are affected mainly by bulk density and saturated hydraulic conductivity, not by clay ratio and dispersion ratio. Lastly, the difference between erosion rates of surface-gleyed red and yellow soils and other soils will be even greater if a soil crust has formed, because the formation of a soil crust increases the rain splash erosion rate.

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Distribution of colluvia and saprolites and their physical properties in a zero-order basin in Okinawa, southwestern Japan

Cited by 13 publications

References 8 publications

Host trait preferences and distribution of vascular epiphytes in a warm-temperate forest

Host trait preferences and distribution of vascular epiphytes in a warm-temperate forest

Distribution and characteristics of soil thickness and effects upon water storage in forested areas of Cambodia

Experimental studies on rain splash erosion of forest soils after clearing in Okinawa using an artificial rainfall apparatus

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