The Comparative Water Economy of Representative Evergreen Sclerophyll and Drought Deciduous Shrubs of Chile

A comparison was made of the drought responses of four shrubby species occurring in the mediterranean-climatic region of Chile Two of these species, Lithraea caustica and Kageneckia oblonga, which are evergreen sclerophylls, showed little tendency to conserve water until the annual summer drought period was considerably advanced. The morphological characteristics and the stomatal behavior of the leaves of these plants indicate features which would limit water loss during periods of drought but not during times of water availability. Two drought deciduous species studied, Proustia cinerea and Flourensia thurifera, which occur in more xeric habitats than the sclerophylls, responded to the drought primarily by the gradual reduction in leaf surface area of the entire shrub. One of these species, P. cinerea, showed no indications of stomatal regulation of water loss right up to the time when leaves abscissed during the drought period In contrast, plants of Flourensia had a drought response intermediate between the sclerophyll species and Proustia These plants showed active stomatal control of water loss, but earlier in the drought period than the sclerophylls. As the drought progressed they gradually reduced their leaf surface area These results are discussed in terms of the carbon balance of these species as it relates to their distribution