COMPARATIVE WATER‐USE OF SOFTWOOD PLANTATIONS AND BAMBOO FOREST

Abstract

SummaryWater‐use of indigenous bamboo forest was compared with that of pine and cypress plantations, in an area where both evaporation and strongly seasonal rainfall have average annual totals of about 45 inches. Water‐use was determined by a combination of continuous soil‐moisture tension records with seasonal, well‐replicated soil samplings, to a depth of 6 ft. from 1948 to 1950 and 10 ft. from 1951 to 1961. Root bisects and profiles of physical properties of the soil are illustrated and the soil moisture tension profiles are summarized in a diagram.Continuous canopies of 120‐ft.‐high Radiata pine, 50‐ft.‐high Monterey cypress, 40‐ft.‐high bamboo thicket, and 20‐ft.‐high young Patula pine all used about the same amounts of water, which were approximately 90 per cent. of that evaporated from an open water surface. Tall woody weeds, which invaded clearings and young pine plantations before the latter had achieved closed canopies, proved equally effective in removing water. Water is saved over 2 to 3 years and soil‐moisture tensions remain low enough throughout the profile to permit recharge of groundwater when the felling and replanting are accomplished under conditions of clean cultivation.