372 



THE STUDY OF PLANT COMMUNITIES 



Animals, as factors— Continued 

 pollination, 198 

 soil organisms, 200 

 as influents, 26 

 Animals, of soil, 200-201 

 macrofauna, 201 

 microfauna, 200 

 Applied ecology, 315-361 

 agriculture, 326-337 

 and secondary succession, 216 

 conservation, 337-347 

 forestry, 316-321 

 human ecology, 359-361 

 landscaping, 347-350 

 plant indicators, 350-359 

 range management, 321-326 

 Aquatic plants 

 aeration, 175-176 

 characteristics, 217 

 emergent, 217-218 

 floating leaved, 217-218 

 lacunar tissue, 175 

 Aralia nudicaulis, 241 

 Arbutus menziesii, 281 

 Arctic tundra, 238-239 



climax, 239 

 Arctostaphylos spp., 274, 275 

 glauca, 282 

 tomentosa, 139, 282 

 Aristida longiseta, 297 



stricta, 253, 256 

 Arte?nisia spp., 268, 286 

 tridentata, 284, 285 

 spine sc ens, 285 

 Artificial forest types, 317-319-320 

 Asclepias mexicana, 199 

 Aspect dominance, 67, 68 



in grassland, 297-298 

 Association, 225-226 



individual, 45 

 Aster, 221 



acuminatus, 241 

 Asymmetric growth and wind, 101- 



102-103 

 Atmometers, 85-86 



description and operation, 85-86 

 indicators of light, 85 

 Atmosphere 

 capacity to hold moisture, 78 

 gaseous content, 75-76 

 of the soil, 174-177 

 variations in composition, 76 

 water content, 77 

 Atmospheric moisture, condensation 



causes, 87 



clouds, 87-88 



cooling of air masses, 87 



fog, 87, 88, 89 



precipitation, 88-95 

 Atmospheric moisture 



and evaporation, 78, 79 



and vegetation, 95-97 



dew point, 86 



measurements, 81-82 



plant distribution, 96 



precipitation of, 77-78 



relationship to temperature, 77 



saturation, 77 



terminology of, 78-79 

 Atmospheric pressure, 97-98 



relation to wind, 97-98 



varying with temperature, 97 

 Atriplex spp., 286 



confertifolia, 285 



nuttallii, 356 

 Autecology, 17 



and physiology, 17 



in the field, 20 

 Auxins, 135-137 



and differential growth, 137 



formation of, 135-136 



relation to size, shape, 136 

 Available water, 170-171 



and root growth, 68, 164 



capillary rise, 164 



degrees of availability, 171 



in different soils, 171 



soil solution, 171 



soil temperature, 171 



B 



Bacteria, soil 

 nitrates, 196-198 

 nitrogen fixing, 196 

 nodule bacteria, 195-196 

 succession of bacteria, 197 



Balance of population, 207-209 

 biological control, 208 

 destruction of predators, 208 

 introduced species, 207-209 



Basal area, 59 

 determination, 62 

 in phytographs, 62, 63 

 relation to dominance, 62 



Base exchange, 179-182 



Batodendron arboreum, 259 



Beech-maple association, 249-250 



Betula lutea, 63, 245, 250 



