The role of vegetation in meteorology, soil mechanics and hydrology

Plants transpire large quantities of water at a rate primarily dependent upon weather conditions, and calculable from easily measured weather elements. They therefore play a dominant part in the water and heat balances of the earth's surface, and affect land drainage, underground storage and river flow. Calculation of the transpiration rate can be made the basis of controlled irrigation to produce maximum growth without waste of water, and it is shown that the principle can be applied equally successfully to a field, to a catchment area and to the British Isles as a whole. When the plants grow in a clay soil, shrinkage may occur as the soil dries, with damaging results on roads or buildings carried on the soil.