SURFACE AREA RELATIONS OF WOODY PLANTS AND FOREST COMMUNITIES

A B S T R A C T Surface area of wood and bark is an important dimension of forests, with implications fol respiration rate, energy exchange, and water and mineral budgets. Surface area of stem wood and bark can be estimated effectively from linear regressions on conic surface (one-half basal circumference times tree height) or from regressions of the logarithm of area on the logarithm of diameter at breast height. Branch surface can be estimated from a formula using branch basal diameter, length, and number of current twigs, and from logarithmic regressions of branch bark surface on basal diameter of branches and breast-height diameter of trees. In temperate deciduous forests several square meters of plant surface occur above each square meter of ground surface; these plant surfaces include 0.3-0.6 m2 of stem bark, 1.2-2.2 m2 of branch bark, and 3.0-6.0 m2 of leaf blades. Branch bark surface increases more rapidly than leaf surface with increasing size of branches and trees. Growth and aging of trees, and maturation of forests, imply increasing ratios of bark (and wood) surface to the photosynthetic leaf surface which supports its growth and respiration. ONE OF THE MOST difficult dimensions of an organism to measure is that which might seem most accessible to measurement-the area of its outer surface. Evolution of the form of the surface tends normally toward the minimum area of protective covering consistent with the organism's structural design and requirements for interchange with environment. Economy in surface of a complex structure is likely to imply geometric complexity of the surface. Is it possible, without full solution of this geometric complexity, to find reasonable approximations of surface area? Estimates are likely to involve either logarithmic regressions of surface area on diameter or other easily measured dimensions, or correction factors from surface area estimates based on a simplified geometry of the organism, or combinations of these. This paper considers ways of estimating above-ground surface areas of woody plants and the interest of these surface areas for the functional ecology of forests and shrublands.