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<br />00281! <br /> <br />. <br /> <br />. <br /> <br />flowing through arid areas will greatly reduce evapotranspiration losses has <br /> <br />been often emphasized but has not yet been demonstrated. <br /> <br />WHAT WE ARE DOING NOW <br /> <br />The rapidly increasing need for more water has focused attention on <br /> <br />the possibilities for improving water yield. This is a more complex subject <br />than originally visualized and far more difficult to put into practice. <br />Much more is involved than simply cutting all the tree or some percent of the <br /> <br />stand. Too much attention has been given to the vegetation cut and too little <br /> <br />attention paid to what vegetation should remain. The real need is to spell <br /> <br />out what kind, size, age, and arrangement of plant cover is the most effective <br /> <br />for specific: situations. This is the sort of information that land managers <br /> <br />can use. <br /> <br />Research on plants.--To get such information more attention must be <br /> <br />given to the differences in transpiration rates, season of water use, and <br /> <br />efficiency of soil moisture extraction among the different kinds of plants. <br /> <br />Some specific items are: <br /> <br />1. Measurements of albedo and energy exchange for individual <br /> <br />species and for various stand structures. We are learning <br /> <br />to answer such questions as: Does spruce trap more energy <br /> <br />for transpiration than pine; do uniform even-aged stands <br /> <br />absort more energy than the variable uneven-aged stands; do <br /> <br />young stands have less heat for transpiration than do taller <br /> <br />older stands; what arrangements of openings give maximum <br /> <br />protection from sun and wind? <br /> <br />- 7 - <br /> <br />