Longitudinal profiles of mountain rivers have been thought to be controlled by the type of bedrock. Thus we verified the relation between the rock properties and the longitudinal profiles of river beds by field measurements and laboratory tests. We chose two rivers which have basins of almost equivalent sizes (2 km²) and relative heights (700 m), located near each other in Niigata Prefecture, central Japan (Fig. 1). The studied reaches in both basins are 900 m in horizontal length and 130‰ in gradient. They differ only in the bedrock type, and are approximately the same in other characteristics, including climatological and geomorphological ones.
A field survey of longitudinal profiles showed that a stepwise longitudinal profile, with a number of falls, formed of bedrock not of gravel, was found in succession in the granite basin, while a smooth and straight profile without a fall was found in the Paleozoic sedimentary rock basin (Fig. 2, Photo 1-a, b).
Compressive strengths (S_c) and tensile strengths (S_t) of Paleozoic sedimentary rocks were 3 or 4 times stronger, respectively, than granite (Table 1). These values were obtained for cylindrical specimens by measurement in a laboratory. Schmidt rebound numbers also are large for Paleozoic sedimentary rocks, in which no fall was found (Fig. 3). In the reach of the granite, the histogram of longitudinal wave velocity measured in the field shows that there are at least two parts with high frequency (Fig. 4): the part with lower velocities (0.9-1.5km/s) to fracture zones or open jointed rocks, and that with higher velocities (1.8-2.1km/s) to intact or jointed rocks. On the other hand, the histogram for Paleozoic sedimentary rocks shows that the frequency tends to increase as the velocity decreases (Fig. 4). Weathering properties obtained by wetting-drying tests (Fig. 5) and dissolution tests (Fig. 6) indicated that both rock types were almost equally resistant to weathering. Therefore it is presumed that the formation of falls is not related to the strength of fresh rock specimens or susceptibility to weathering.
Fracture zones or open joints were found at intervals of 10_??_20 meters in the reach of granite. On the contrary, no significant fracture zones could be found in the reach of Paleozoic sedimentary rocks, which existed as bedding planes densely at intervals of several centimeters. Hence, it can be said that weak zones such as joint planes, bedding planes and fracture zones in the Granite reach are distributed clearly in a different mode from that in the Paleozoic sedimentary rock reach.
It is an empirical fact that discontinuities such as joint planes, bedding planes and fracture zones slow the longitudinal wave velocity in the rock mass. Index K, which expresses the degree of fissuring, is given by V_pf/V_pl, in which V_pf is the longitudinal wave velocity of bedrock measured in the field and V_pl is that of cubical specimens without visible discontinuities. We can express the rock mass strength (S_tm) affected by discontinuities as follows
S_tm =K²×S_tl,
where S_tl is the mechanical strength measured for cylindrical specimens without visible discontinuities (Ikeda, 1979).
Applying index K, we can calculate values of two other quantities K²×S_c and K²×S_t, which express the rock mass strength for each rock facies (Table 2). In the reach of granite the rock mass strength of intact rocks or jointed rocks was 10_??_25 times as large as that of fracture zones or open jointed rocks.

View full abstract

This paper deals with the managerial characteristics and economic infrastructure of urban farmers from the three aspects of labor composition, mobilization of farmland, and multi-purpose land utilization; it examines the fruit-growers in the Tanaka area, Isehara city, Kanagawa Prefecture, a western suburb of Tokyo, with the intention of reviewing the effect of partitioning in compliance with the New Urban Planning Act.
Reorganization of deciduous fruit-growers farmers took place in Old Isehara town, Isehara City, during the 1970-1975 period. As a result, areas with late-coming fruit-growers farmers outside the Tanaka area suffered erosion of the agricultural infrastructure by waves of urbanization, becoming non-agricultural areas. On the other hand, fruit-growing farmers whose villages and arable lands were incorporated only partially into the urbanized district made the best of the exclusive urban land utilization value of farmland inside the urbanized district made available to them through partitioning. At the beginning of 1970, they started stable real estate management, establishing the base for a farm economy. On the basis of the foundation thus generated, they achieved the efficient management of fruit farms in the coordination area and high-level farming through a rational directselling system. Moreover, they enhanced the probability of survival of farmlands and farming in the Tanaka area by maintaining the high value of the produce of fruit trees and gardens as the property of the village as a whole or in a form of a complex.
It may be concluded from the case study in the Tanaka area of Isehara City that, when partitioning is done in compliance with the New Urban Planning Act, with major allowance for the urbanization coordination sector, in farming villages with firm agricultural infrastructure and strong will to continue the farm management, the village will demonstrate a greater than conventional competitiveness in the face of the progress of urbanization.

View full abstract

The turbulent fluxes of carbon dioxide and water vapor within rice plant canopies were measured over water surfaces which were covered and uncovered with duckweed (Lemna paucicostata). Observations were made by the eddy correlation technique with three-dimensional sonic anemometer thermometers and infrared carbon dioxide-humidity fluctuation meters. The amount of photosynthesis of an individual frond was measured with a portable chamber. The results are summarized as follows:
1) The turbulent flux of carbon dioxide at a height of 20 cm caused by the photosynthesis of duckweed was about -0.1-0.2mg/m²•s in daytime and about one-tenth of that in a rice stand.
2) The turbulent water vapor flux measured over the water surface covered by duckweed was slightly greater than that over the uncovered water surface.
3) The amount of photosynthesis of an individual frond was 0.14-0.17mg/m²•s at about 250-600, μmol/m²•s and 30°C conditions, and its value was nearly equal to that of the carbon dioxide flux above the duckweed community.

View full abstract