384 



THE STUDY OF PLANT COMMUNITIES 



Salt spray, effects, 102, 103 



distribution of vegetation, 51, 52 

 Salt tolerance, 184-185 



zonation, 185 

 Sample plots, 35 

 Sampling, ecological, 35-54 

 efficiency, 45-47 

 random versus systematic, 49, 50 

 Sand dunes, 111-115, 149-150 

 as plant habitats, 150 

 blowouts, 150 

 moisture conditions, 171 

 stabilization, 111, 113, 114, 115 

 Sandhills, Nebraska, 296 

 Saprophytes, 26-27 

 Indian pipe, 27 

 squaw root, 27 

 Sarcobatus vermiculatus, 185, 286 

 Savannah, 253, 254 

 and fire, 254, 256 

 Sclerophyll, anatomical characteris- 

 tics, 140 

 Seasonal 

 aspect, 65, 67 

 dominance, 65 

 Secondary succession, 214-215, 221- 

 225 

 after cultivation, 221-222 

 after fire, 215, 254 

 old fields, 221-222 

 rate, 215 

 Selaginella acanthonota, 257 

 Selectives (fidelity), 72 

 Self pruning, 137 

 Sequoia gigantea, 273, 274 



sempervirens, 278, 279 

 Shade 



and seed production, 140 

 leaves 

 characteristics, 137-139 

 where found, 137 

 plants, 132 

 tolerance 



and photosvnthetic efficiency, 



134 

 practical considerations, 134 

 relation to succession, 134 

 water versus light, 134, 135 

 Sierra Nevada forest complex, 269- 

 276 

 east slope, 275-276 

 foothills (woodland) zone, 274, 



275-276 

 montane zone, 274 



range, climate, altitudes, 269-271 

 subalpine zone, 270, 271-274 

 Silvics and ecology, 317-321 

 artificial forest types, 317-319-320 

 continuous production, 320 

 plant sucession, 317, 320 

 pure and mixed stands, 317 

 virgin and climax forests, 321 

 Short grass plains, 295, 296-297, 312 

 Sisymbrium altissimum, 206 

 Sleet, 90 

 Slope 

 exposure, 124, 125, 133 

 relation to light and temperature, 

 133 

 Smilax laurifolia, 257 

 Snow 

 as an insulator, 127 

 effects on water supply, 68, 69 

 in subalpine areas, 91-92 

 measurement of fall, 94-95 

 Sierra Nevada, 92, 271 

 source of soil moisture, 90-91 

 water content, 95 

 Sociability, gregariousness, disper- 

 sion, 64 

 Sociological analysis 

 objectives and procedure, 74 

 summary of concepts, 73 

 Sociological data, application, 56 

 Soil, 144-161 

 acidity, 178-179 



and soil organisms, 178 

 decreases with depth, 1 78 

 H ion concentration, 178 

 relation to precipitation, 1 78 

 acid or alkaline reaction, 145-146 

 aeration 



poorer with depth, 1 74 



root growth and distribution, 



174-175 

 type of vegetation, 175 

 air analysis, 177 

 air capacity, 175, 177 

 aggregation and alkalinity, 183 

 alkali, 184 

 alkalinity, 183 

 animals, 200-201 

 atmosphere, 76-77, 148, 174-177 

 and root growth, 77 

 and soil organisms, 77 

 changes with depth, 174 

 determination of volume and 



composition, 177 

 relation to water content, 177 



