LIFE ZONE ECOLOGY by L.R. Holdridge With Photographic Supplement Prepared by Joseph A. Tosi, Jr. REVISED EDITION TROPICAL SCIENCE CENTER SAN JOSE, COSTA RICA © TABLE OF CONTENTS TROPICAL SCIENCE CENTER.................................................................................1 INTRODUCTION........................................................................................................1 THE LIFE ZONE.........................................................................................................7 Selection of a basic unit in ecology .........................................................................7 Grouping of basic units ...........................................................................................7 Past attempts at classification...............................................................................10 Considerations of past classification attempts ......................................................11 The Holdridge life zone classification....................................................................13 THE LIFE ZONE CHART.........................................................................................19 Heat ......................................................................................................................20 Altitudinal and Latitudinal Ranges of Vegetation Zones:.......................................25 Precipitation ..........................................................................................................27 Moisture ................................................................................................................28 Determination of the life Zone from Climatic Data.................................................29 THE ASSOCIATION.................................................................................................32 Division of a Life Zone into Associations...............................................................32 The Association Unit .............................................................................................34 Classes of Associations ........................................................................................35 Naming of Associations ........................................................................................37 Association Description Methods..........................................................................39 Animal Activity in Association Descriptions...........................................................48 Association Niches................................................................................................48 Physiognomic Data needed for Associations and Subdivisions............................51 SUCCESSION..........................................................................................................53 Definition...............................................................................................................53 Evolutionary Succession.......................................................................................53 Primary Succession ..............................................................................................55 Secondary Succession .........................................................................................59 Succession in Land Management.........................................................................62 Future Research Needs........................................................................................63 THE SOIL .................................................................................................................66 Soil as a Part of the Ecosystem ............................................................................66 Attempts to Develop Soil Classification Systems..................................................67 Soil Series.............................................................................................................68 Soil Type...............................................................................................................69 Correlation of Soils with Vegetation ......................................................................70 Correlation of Classifications in various Disciplines ..............................................70 Zonal Soils ............................................................................................................71 Aging of Soils........................................................................................................72 Productivity ...........................................................................................................73 THE ATMOSPHERE ................................................................................................76 Composition of the Air...........................................................................................76 Density and Height of the Atmosphere .................................................................76 Water Vapor Content of the Atmosphere ..............................................................77 Other Atmospheric Conditions ..............................................................................82 WATER ....................................................................................................................83 Water, as essential for Life....................................................................................83 Measurements and Attempts to Measure Atmospheric Water Movements ..........84 Transpiration.........................................................................................................89 Potential Evapotranspiration .................................................................................92 Nomogram of Water Movements in Climatic Associations....................................94 Use of the Nomogram...........................................................................................98 Calculations of Water Movements from Other kinds of Associations....................99 HUMAN ECOLOGY................................................................................................103 Man's Original Niche in Warm Climates..............................................................103 Extension of Man’s Area .....................................................................................103 Development of a Separate Human Ecological System......................................105 The Population Explosion ...................................................................................108 The Approaching Crisis of Overpopulation..........................................................110 Territoriality .........................................................................................................111 The Future ..........................................................................................................112 LAND USE PLANNING ..........................................................................................114 Land Use Methods of Little Significance in Man’s Early History..........................114 Factors which affect Land Use............................................................................115 Effects of Overpopulation....................................................................................116 Major Divisions of Land Use ...............................................................................117 Actual vs. potential use .......................................................................................119 PRODUCTIVITY.....................................................................................................121 Definitions ...........................................................................................................121 Discussion of the Three Methods of Measuring Productivity...............................122 Method of Rating Commodity Productivity ..........................................................124 Use of Productivity Information ...........................................................................126 The Three Major Land Use Systems ..................................................................126 Comparisons of Commodity Productivity with Basic Natural Productivity ...........129 Balance Between Population Growth and Productivity .......................................131 EVAPOTRANSPIRATION EQUILIBRIUM IN A CLOUD CHAPPARAL ASSOCIATION OF COASTAL PERU ....................................................................132 A COMPARATIVE PHOTOGRAPHIC STUDY.......................................................139 SELECTED BIBLIOGRAPHY.................................................................................140 I CHAPTER I INTRODUCTION Like a bit of bright blue sky propelled erratically through the forest, a wide- winged Morpho butterfly rises and dips and moves rapidly across the varied shades of green and leaf-patterns. Also conspicuous, but on a smaller, slower scale, Dendrobates, a bright red frog with dark blue legs hops about on the fallen leaves and bare patches of moist soil. All about, mostly gray-and smooth-barked trees rise up through the heavy shade, some of majestic proportions with huge plank buttresses angling out from the trunks, others with terete or angled boles disappearing above in the general mass of foliage. Tall trees, short trees only a few meters high, long slender-holed palms, some perched low or high on a mass of arching stilts, dwarf palms, banana-leaved Heliconias,