Species (Conttn.) 



specificity of, 47, 80 



strange, 127 

 Spectrum, floristic, 94 

 Spitzbergen, 16, 34, 139 

 Sporobolus (Dropseeds) 



cryptandrus (sand D.), 85, 103; het- 

 erolepis (prairie D.), 71; micro- 

 spermus (six-weeks D.), 11 

 Spruce. See Picea 

 Square-foot density method, 103 

 Stability in vegetation, 150, 155, 158, 



159, 163, 164 

 Stabilization, 161 

 Stand, 24 



analysis of, 105, 109, 121, 125, 188 



classification, 68, 173-174 



definition, 66 



delimitation of, 171-172 



description of, 130, 172-173, 175, 

 178 



relation to habitat, 173 



table, 116-117, 121 



variation within, 96 

 Standing crop, 151 

 Steady-state, 136, 148, 149, 157, 159, 



162, 164, 165, 167 

 Stipa (Needlegrasses), 184 



comata (needle-and-thread), 23, 44, 

 47, 48, 62, 70, 73, 84, 92, 98, 

 104, 114, 129, 144, 172, 179, 185; 

 spartea (porcupine grass), 15, 71, 

 92, 128; vindula (green N.), 23, 

 107, 172 

 Strain of forage plants, 25, 32, 45, 51 

 Stratification, 77, 82-85, 130, 159, 



173 

 Stratum. See Layer 



Streptanthus arizonicus (Twistflower), 32 

 Structure of vegetation, 1, 66, 68, 92, 



163, 171, 172, 185 

 Suaeda depressa (Seepweed), 145 

 Subalpine, 58, 81 



scrub, 44 

 Subarctic region, 72, 80, 82, 137, 139, 



174 

 Subclimax stage, 184 

 Succession, 82, 148-156, 166, 183, 184 



and ecological efficiency, 22 



and formation of groupings, 64-65 



and population density, 101 



and sociability, 97 



and vitality, 90 



autogenic, 148, 150 



basis of classification of commu- 

 nities, 184, 188 



criteria of, 149-151 



deflected, 155 



influence of insects on, 48-49 



on solonchalk and solonetz soils, 144 



primary, 140, 175 



rate of, 158 



secondary, 41, 47, 64, 96, 97, 103, 

 112, 152, 175 

 old-field, 153, 184 



stages in, 22, 137, 150, 165, 167, 

 171, 173, 182 

 Sunflower. See Helianthus 

 Supercanopy trees, 82 

 Survival, 15 



basic needs for, 10 



in refuges, 158 

 Sweden, 146, 178 

 Sweet clover. See Melilotus 

 Switchgrass. See Panicum virgatum 

 Symbiosis, 26 

 Sympatric, 43 



Symphoricarpos (Snowberry), 185 

 Synchorology, 186 

 Syndynamics, 184 

 Synecology, 173, 181 

 Synsystematics, 175 

 Synthesis table, 121, 122 

 Synthetic characteristics, 77, 121-132 

 Synusiae, 84 

 System, cyclic, 143-146 



Table, synthesis, 121, 129 

 Tannin, 111 



Taxodium distichum (Bald cypress), 20 

 Temperature summation, 1 1 

 Texas, 12, 55, 118, 160 

 Therophyte, 93, 94 

 TUia (Basswoods, Lindens) 

 Jioridmna, 83; heterophylla (white B.), 

 83; neglecta, 83 

 Timothy (Phleum), 35 



216 * Index 



