VI 



CONTENTS. 



PAGE. 



II. Bases and Criteria — Continued. 



indicator criteria — continued. 



Growth-Forms. 



Nature 68 



Kinds 69 



Indicator relations 69 



Standard plants for growth correlations . . 70 

 Competition-forms 71 



Communities as Indicators. 



Value 72 



Kinds of communities 72 



Community structures 73 



Alternes 73 



Layers 74 



Aspects 75 



III. Kinds of Indicators. 



Basis of distinction 76 



factor indicators. 



Basis and kinds 76 



Quantitative sequences 77 



Climatic and edaphic indicators 77 



Water indicators 78 



Light indicators 79 



Temperature indicators 81 



Indicators of solutes '. . . 83 



Saline indicators 83 



Lime indicators 84 



Aeration indicators 85 



Indicators of factor-complexes 88 



Soil indicators 88 



Slope-exposure indicators 88 



Altitude indicators 89 



Oi ganism indicators 90 



process indicators. 



Nature 91 



Kinds 91 



Fire indicators 92 



Lumbering indicators 93 



Cultivation indicators 93 



Grazing indicators 94 



Indicators of irrigation and drainage 95 



Construction indicators 96 



Physiographic indicators 97 



Climatic indicators 97 



PRACTICE INDICATORS. 



Nature and kinds 98 



PALEIC INDICATORS. 



Paleo-ecology 99 



Nature of paleic indicators 100 



Kinds 101 



Paleic indicators of climates and cycles. . . 103 



Paleic indicators of succession 103 



Plant indicators of animals 104 



Animal indicators of plants 104 



IV. Climax Formations of Western 

 North America. 



Nature 105 



Tests of a climax 105 



Structure and development 106 



PAGE. 



IV. Climax Formations of Western 

 North America — Continued. 



Societies 107 



Names of climax communities 109 



Serai communities 109 



Indicator significance of climax formations 111 



Significance of succession Ill 



Indicator value of disturbed areas 112 



Summary of the climax formations 113 



the grassland climax. 

 Stipa-Bouteloua Formation. 



General relations 114 



Unity of the grassland 115 



Correlation with climate 116 



Use of weather records 116 



Relationship of associations 118 



Floristic relations 119 



Ecological relations 120 



Subdominants 120 



Developmental relations 121 



the true prairie. 

 Stipa-Koeleria Association. 



Extent 121 



Factor relations 123 



Sequence of dominants 123 



Societies. 



Nature 125 



Control of dominants 125 



Relation to consociation 126 



Origin 126 



Mixed societies 127 



Aspects 127 



Zones and alternes 128 



Studies of prairie societies 129 



Clans. 



Vernal clans 131 



Estival clans 131 



Serotinal clans 131 



the subclimax prairie. 

 Andropogon Associes. 



Nature 131 



Range 132 



Factor relations 133 



Sequence 133 



Grouping 134 



Societies and Clans. 



the mixed prairie. 



Stipa-Bouteloua Association. 



Nature 135 



Effect of grazing and climatic cycles 135 



Range 136 



Grouping 137 



Sequence of dominants 138 



Societies of the Mixed Prairie. 



Prevernal societies 139 



Vernal societies 139 



Estival societies 139 



Serotinal societies 139 



