Schedonnardus paniculatus (Tumhlegrass), 



49, 98, 145 

 Schimper, A. F. W., 186 

 Schoenus nigricans (Black bog-rush), 72 

 Scirpetum validi association (Bulrush 



association), 180 

 Scotland, 143, 181 



Sedge association. See Caricetum stridae 

 Sedge marsh, 140, 156 

 Sedum (Stonecrops), 95 



stenopetalum, 47 

 Seed, blind seed disease, 51 

 Selenium, 1 1 1 



Self-maintaining community, 150, 159 

 Senecio perplexus (Groundsel), 98 

 Sere, 188. See also Succession, stages in 

 Series of changes, downgrade, up- 

 grade, 143-146 

 Series, successional, 166, 184 

 Serotinal aspect, 87 

 Serpentine, 72 



Setaria viridis (Green bristlegrass), 184 

 Shiblyak, 64 



Shortgrass vegetation, 56, 89, 140, 185 

 Shrubland, 177, 185 

 Shrub stage in succession, 140, 155 

 Shrubs, 65, 187 



Sibbaldia procumbens (Sibbaldia), 58 

 Sierra Nevada Mountains, 13 

 Silene acaulis (Moss campion), 36 

 Silvicide, 62 



Similarity of communities, 126, 173- 

 174 



coefficient of, 1 74 



index of, 99 

 Site, 125, 159, 160. See also Habitat 

 Sloughgrass association. See Spartinetum 



pectinatae 

 Snow cover, 62, 157, 161, 174, 182 

 Sociability, 96-98, 130 



classes of, 96-97 

 Sociation, 126, 161 



use in classification, 178 

 Soil, 183, 186; alkah, 144 



brown group, 124 



chestnut group, 70 



development, 144, 150 



formation and gradients, 139 



gradient, 140 



improvement, 21 



infiltration, 22 



moisture, 69, 74 



profile, 61, 173 



saline, 144 



structure, 22, 69 



texture, 69 

 Solifluction, 158, 162 

 Solidago (Goldenrods) 



caesia (wreath G.), 83; latifolia 

 (broadleaf G.), 83; htrsutissima, 

 112; puberula (downy G.), 84 

 Solonchalk, 144 

 Solonetz, 144 

 Soloth, 144 

 Sorensen, Th., 99 



Sorgum halepense (Johnson grass), 112 

 South America, 92 



Spanish moss {Tillandsia usneoides), 52 

 Spartina (Cordgrasses), 56 



alterniflora (smooth C), 44; mantima, 

 44; townsendii, 44 

 Spartinetum pectinatae association 

 (Sloughgrass association), 180 



accidental, 127 

 Species, 



and phenology, 88 



association of, 98-100, 128, 137 



characteristic, 126, 127, 148, 172, 

 173, 178, 181, 188 



companion, 127 



constant, 125, 127, 172, 178, 181, 

 188 



differential, 173 



differentiating, 179 



dominant, 142, 148, 156, 173, 178, 

 188 



ecological characteristics, 7 



exclusive, 126, 128 



faithftil, 126 



indicator, 80, 121, 127, 140 



indifferent, 127 



number, 71, 78-79, 81, 89, 99, 114, 

 124 



preferential, 126, 127 



relict, 155 



selective, 126 



Inaex • 215 



