PROCESS INDICATORS. 93 



readily after fire, thus furnishing a large number of seeds for immediate ecesis. 

 Three important species of this type occur in western North America, namely, 

 lodgepole pine, Pinus contorta, jack pine, P. divaricata, and knobcone pine, 

 P. attenuata. These are all typical fire trees, and form subclimaxes of great 

 extent and duration in areas frequently swept by fire (Clements, 1910). In 

 the Coast forest, Larix occidentalis and Pseudotsuga mucronata likewise owe 

 their dominance in large measure to fire, though for reasons partly connected 

 with their intolerance. 



Among herbaceous plants the number of fire indicators is legion. A large 

 number of these are annuals and biennials, but some of the most widespread 

 are perennials, such as Epilobium spicatum and Pteris aquilina. They are not 

 restricted to flowering plants, but are represented by Pyronema confluens 

 among the fungi, Marchantia polymorpha among the liverworts, and Bryum 

 argenteum and Funaria hygrometrica among the mosses. The most typical 

 fire-grass is Agrostis hiemalis, while among the composites, Anaphalis mar- 

 garitacea, Achillea millefolium, Arnica cordifolia, Erigeron acris, and species 

 of Carduus, Senecio, and Solidago are especially important. In severe burns, 

 the germules may be largely destroyed, and the resulting subsere shows 

 distinct stages of which Agrostis hiemalis is the first community and Epilo- 

 bium the second. Very often, however, the dominants of the various stages 

 appear during the first two years, and the successional movement consists 

 chiefly of the successive dominance of annuals, biennials, perennials, bushes, 

 and trees, as they replace or overtop each other. Many of the herbs and 

 bushes persist as layers if the shade permits, suggesting that they were origi- 

 nally derived from such. In most cases, their continued persistence as societies 

 is connected with occasional ground fires. In such instances, the evidence 

 furnished by their presence can be checked by means of fire-scars, the age of 

 burned seedlings, and the presence of charcoal in the soil. 



Lumbering indicators. — As a general rule, the indicators of lumbering 

 operations are of much less importance than those of fire. This is due to the 

 fact that the direct evidence afforded by stumps and relict trees is altogether 

 conclusive, and that furnished by the herbs and shrubs is superfluous. In 

 spite of this, there are not infrequent cases where the clearing has been so 

 complete that the usual woody relicts are absent. Many of these are com- 

 plicated by fire or cultivation, and some by both. However, in the midst of 

 virgin forest, clearings occur in which the evidence as to the agent must be 

 sought from the species in possession. In all clearings due to the ax, whether 

 the direct evidence is still available or not, many of the dominants are the 

 same as in burns. The chief difference in the two communities lies in the 

 greater selection exerted by fire, with the result that the dominants are fewer 

 in number and more controlling. For the same region, the major dominants 

 are the same for both, particularly where fire has followed lumbering, as has 

 been the rule. 



Cultivation indicators. — As suggested previously, these might well be called 

 indexes rather than indicators, since they are the consequence of cultivation 

 instead of an indication of its possibility. The number of such indicators is 

 very large and they vary from one climax to another in accordance with the 

 flora. Many of them are introduced weeds, but the majority are subruderal 

 species derived from the adjacent vegetation. The relative importance of 



