We shall limit our observations to the conditions in natural ecosystems, since it would be beyond the scope of this book to embark upon a consideration of secondary, man-made ecosystems. 2. Classification of the Geo-biosphere into Zonobiomes The biosphere is the thin layer of the earth's surface to which the phenomena connected with living matter are confined. On land, this comprises the lowest layer of the atmosphere permanently inhabited by living organisms and into which plants extend, as well as the root-containing portion of the lithosphere, which we term the soil. Living organisms are also found in all bodies of water, to the very depths of the oceans. In a watery medium, however, cycling of material is achieved by means other than those on land, and the organisms (plankton) are so different that aquatic ecosystems have to be dealt with separately. The biosphere is therefore subdivided into (a) the geo-biosphere comprising terrestrial ecosystems, and (b) the hydro-biosphere, comprising aquatic ecosystems, which is the field of hydrobiologists (oceanographers and limnologists) . Our studies are confined to the geo-biosphere (Walter 1976), which constitutes the habitat of man and is, therefore, of special interest. The prevailing climate, being the primary independent factor in the environment, can be used as a basis for further subdivision of the geo-biosphere since the formation of soil and type of vegetation are dependent upon it (see p. 3), and it has not yet been substantially influenced by man.

Phytomass and Primary Production of the Various Vegetational Zones and of the Entire Biosphere The biosphere is that thin layer at the earth's surface in which living organisms exist and biological cycling takes place. It includes the upper horizons of the soil in which plants root, the atmosphere near the ground, (insofar as organisms penetrate this space), and all the surface waters. More than 99% of the earth's biomass is phytomass, to which we shall limit our discussion. Amounts of phytomass are distinctly related to vegeta tional zones. Because accurate determination of phytomass and primary production is difficult, only gross estimates have been available until recently. However, in 1970, Bazilevich et al. published (in Russian) more accurate calculations, based on the rapidly accumulating literature, for the various thermal zones and bioclimatic regions of the earth. These authors calculated mean phyto mass and mean annual primary production for the various regions as dry mass (in tons) per hectare. On the basis of measurements of the areas covered by the individual regions, excluding rivers, lakes, glaciers, and permanent snow, total phytomass and total annual primary production for the various regions were obtained (see table). The sum of these figures is the phytomass and annual production of the land surface of the earth. In addition, the table gives corresponding data for the waters of the earth. The values involved are potential i. e. , they are based on natural vegetation uninfluenced by man.

Zonobiome, desert, Tundra, Taiga, laurel, ecosystem, grassland, climate, forest, tropical, woodlands, rain.

Starting with an account of the history and distribution of the conifers, this volume describes the most important areas in Asia, Europe, North and South America with conifer forests. The last in the "Ecosystem of the World" series, it deals with the functional aspects of the conifer forests, such as physiology, production, biomass, and more.

Changing desert areas for land use implies a lot of ecological problems. These and related ones are dealt with in this book covering various interdisciplinary and international aspects. Large areas in arid and semi-arid regions are already polluted in various ways. One of the biggest problems is the anthropogenic salinization by inadequate means of agriculture and irrigation. Additionally, most arid areas in the world are dramatically overgrazed. Methods and practices of a sustainable land use in deserts are urgently needed in many arid regions. This book gives a broad survey on some of the affected regions of the world as well as some case studies from elsewhere (Aral Sea, Negev desert, Namib desert etc.). Thus, basic and applied sciences are brought together. Water management in deserts, grazing systems or reclamation of desertified areas are among the topics of this book, as well as social and economic aspects.