Ecological Aspects of Transpiration. II. Pike's Peak and Santa Barbara Regions: Edaphic and Climatic Aspects

1. Radiant energy seems to be the most important factor between sun and shade habitats. Shade vegetation does not respond to any one factor, however, but rather to all of the environmental conditions. 2. Although individual factors varied, the environmental complex at two different stations produced similar functional responses in the coastal chaparral association. 3. The xeric character of the vegetation of the sand dunes is due to an edaphic rather than to a climatic condition. 4. Soil temperature, below approximately 37-39⚬F., is an important factor in limiting transpiration. Water loss seems to be increased by higher soil temperatures up to a certain point where the curve flattens off. The effect of different soil temperatures requires further study. 5. Transpiration was found to be highest in soils of medium water content, next in saturated soils, and lowest in soils with low water contents. 6. Osmotic values showed a constant decrease with increased soil moisture.