| Abstract: | At Bedgebury the rainfall in thirteen forest plots planted withdifferent tree species has been compared with that in the open.In all these forest plots the trees have closed canopy within20 years of planting and the canopies differ considerably intheir structure. From 6 to 93 per cent. of the gross rainfallmay be retained on the tree canopies and lost to the soil. Theproportion of precipitation intercepted is greatest in lightrains and least in heavy rains. During light showers considerablymore moisture is retained on the conifer than on the hardwoodcanopies. In the heavier showers rainwater flows down the stems,but stem flow represents a small proportion of the total waterreaching the forest floor. The amount of water which reachesthe ground along the trunks varies with the species and thecharacter of branching. Some raindrops penetrate directly throughthe canopy, but many are intercepted by the canopies and coalesceto fall as large drops on the forest floor. These large waterdropstend to fall continuously on the same spot so that in the plantationsthe water is distributed unevenly. In the winter months, whenthe deciduous species have shed their leaves, snow penetratesmore easily through their canopies than those of the evergreenconifers. |
