CLIMATIC CONTROL OF VEGETATION DISTRIBUTION - THE ROLE OF THE WATER-BALANCE

The water balance describes climate as it is sensed by plants, as the interaction of energy and water in the environment. Discriminant analysis showed that the distribution of North American plant formations was more highly correlated with water balance (actual evapotranspiration and deficit) than with the more traditional measures of climate (eg temperature and precipitation). Much of the improved correlation could be attributed to the ability of the water balance to distinguish between climates similar in mean annual energy and water supplies but different in the seasonal timing of the two. Consideration of the water balance aided in the interpretation of possible mechanisms controlling the distribution of plant formations, eg coniferous forest occurred at low actual evapotranspiration (low simultaneous availability of energy and water), consistent with the suggestion that conifers are better adapted than deciduous trees to environments with a low potential for primary production. Implications for vegetation response to climatic change are noted. -from Author