On the Water Contents of the Uppermost Soil Layers of Sabo Forests (Erosion Control Forests)

In this paper were examined the relationships between the water content of the uppermost soil layer and the meteorological factors.<br> The investigated areas were 20-28, 6-7, and 2-3 years Sabô-forests (Erosion control forests), 25-65 and 5-15 years natural stands and the devastated bare areas in Ueno regions, Mie Prefecture. Parent rocks of all those areas are granites.<br> The water content of soils was measured half-monthly from March to October in 1959.<br> The examined meteorological factors were as follows:<br> a) P: Gross precipitation.…… The amount of precipitation measured in the open.<br> b) P': Adjusted precipitation.…… The estimated amount of precipitation which contri-butes to the increase of the mineral soil moisture. It was estimated from the precipitation after correction in a way that the portion of the precipitation which exceeds 60mm or reaches less than 3mm should be disregarded.<br> c) P' -E: A kind of net income of water.<br> d) E: Amount of evaporation.<br> e) Ts: Soil temperature at the 10cm depth from the surface at 3 p.m.<br> f) Ta: Daily mean atmospheric temperature measured in the open.<br> Statistical analyses were made by the integrating values of those six factors for 5, 10, and 15 days before the soil moisture measuring day.<br> The results were as follows:<br> 1. The correlation coefficients between soil moisture and the above-mentioned factors did not differ significantly among different integrating days, except only one example of the well grown young natural stand.<br> 2. In all kinds of stands, the soil moisture had the highly significant correlation with the amount of evaporation, the soil temperature and the atmospheric temperature which have a great influence upon the amount of water loss.<br> 3. The correlation between soil moisture and the adjusted precipitation was not signifi-cant in the well-established natural stands and the bare areas, contrary to the remaining stands.<br> The identical method in adjusting precipitation seemed to be not well adapted to those areas which have extreme values of A_o layer thickness and mineral soil depth.<br> 4. Precipitation had no significant correlation with the surface soil moisture in most of the studied areas.<br> 5. It was found that in many investigated areas the factors referring to water loss, such as atmospheric temperature, soil temperature, or evaporation, have the most close partial correlation with soil moisture among six meteorological factors studied.