Primary production: Terrestrial ecosystems

Abstract

The history of growth in understanding of primary productivity and in making estimates of biosphere production is reviewed. Two approaches to estimation of land production are discussed. Production may first be estimated by mean values for ecosystem types and the areas of these. A total production of 100×10 9 tons/year is thus estimated for the continents, making up 29% of the earth's surface. The energy content of net primary production is 426×1018 cal for the continents and 261×1018 cal for the seas, implying a biosphere energy efficiency of 0.13% relative to incident sunlight of the full spectrum at the earth's surface. As a second approach, the relation of productivity to mean annual temperature and precipitation is analyzed. On the basis of these relationships, a “Miami model” map of primary productivity of the continents is presented.