382 



THE STUDY OF PLANT COMMUNITIES 



Poa, 268 



pratejisis, 292, 293 

 Pocosins, 257 

 Podsolization, 155-156 

 Pollen, wind-borne, 107-108 



amounts, 107-108 



characteristics, 108 



distances, 107-108 

 Pollen analysis, 304-307 



correlation with climate, 306-307 



methods, 305-306 



peat sampler, 304 



pollen diagrams, 305, 306, 307 



theory, 304-305 

 Pollination 



animals, 198 



devices, 190 



wind, 107-108 

 Polyclimax versus monoclimax, 226- 



229 

 Polygonella polygama, 257 

 Polystichum spp., 278 

 Population balance, 207-209 

 Populus acuminata, 266 



angustifolia, 266 



sargentii, 266 



tremuloides, 243, 244, 262, 266 

 mycorhiza, 194 

 Porcupine, damage, 202 

 Postclimax and preclimax 



in altitudinal zonation, 227-228 



in latitudinal zonation, 227-228 



relicts, 228 

 Postglacial vegetation, 301-314 



progressive changes, 305, 306, 307 



reconstruction of (see Pollen an- 

 alvsis) 

 Prairie "peninsula," 293-294 

 Precipitation 



and base exchange, 181 



and runoff, 93-94 



average annual, for U.S., 96 



causes, 88-89 



effectiveness, 93, 163 



evaporation ratio, 96, 97 



forms of, 89-90 



interception by vegetation, 93-94 



measurement, 93-95 



seasonal distribution, 93 



seasonal variation, 96, 97 



source of, 88 



records, 95-97 



polygonal diagrams, 95, 96 

 seasonal, 95-96 

 Preclimax, 227-229 



Predators, destruction of, 208 

 Preferents (fidelity), 72 

 Presence, 69-71 



diagram, 71 



scale of, 69 



tabulation, 70 

 Primary succession, 213-214 



hydrarch, 216-217 



xerarch, 218-219-221 

 Profile diagrams 



topographic, 50 



vegetational, 54 

 Prosopis chilensis, 288, 289 



juliflora, 289 

 Primus serotina, 249 

 Pseudotsuga, 277, 278, 279 



mucronata, 194 

 mycorhiza, 194 



taxifolia, 262, 264 

 Psychotria punctata, 196 

 Psychrometer, 81 

 Pulpwood forest, Maine 



composition by phytographs, 63 

 Purshia, 268 



tride?itata, 269, 286 



Quadrats, 36-51 

 kinds, 36-43 



chart, 36, 37, 38 



experimental, 41 



list-count, 36 



permanent, 36, 40 

 mapping, 37, 38 



by pantograph, 39 

 marking, 36, 37, 39, 40, 41 

 photographing, 38, 39 

 methods 



distribution, 49, 50 



in stratified vegetation, 48 

 nested, 48 



random versus systematic, 49, 50 

 relation of shape to efficiency, 44 

 shape, 43-44 



size and number, 44-49, 46, 48 

 spacing, 51 

 Qualitative sociological characters, 



64-68 

 dispersion, 64 

 periodicity, 65 

 stratification, 65 

 sociability, 64 

 vitality, 64 

 Quantitative sociological characters 

 abundance, 56-57 



