INDICATOR SIGNIFICANCE OF NATIVE VEGETATION 285 



Geranium richardsonii, Viola neomexicana, Amarella scopulorum, 

 Gentiana bigelowii, Prunella vulgaris, Mimulus langsdorfii, 

 Penstemon virgatus, Campanula petiolata, and Solidago neo- 

 mexicana. Site II bears such transitory species and xerophytes 

 as Poa rupicola, Commelina dianthifolia, Yucca sp., Quercus 

 grisea, Portulaca oleracea, Heterolhrix longifolia, Cercocarpus 

 breviflorus, and Hymenopappus radiatus. The moss (Mnium sp.) 

 was only found in cool, moist and shaded situations, thereby 

 indicating unusually favorable site conditions. The monkey 

 flower (Mimulus langsdorfii) was the only plant which was 

 confined to the proximity of water, indicating excessive soil 

 moisture conditions. 



Practically all of the species listed as occurring entirely on 

 Site II, which do not overlap on other sites, were found in hot, 

 dry and unshaded situations and might be regarded tentatively 

 as indicators of poor western yellow pine sites in the San Mateo 

 Mountains. The mesophytes listed as possible Site I indicators 

 were not found on poorer sites in this locality. However, it may 

 be true that further detailed studies in the San Mateo Mountains 

 might require a different listing of the vegetation than that here 

 given. A number of the species listed as occurring on only one 

 site are, to the writer's personal knowledge, known to occur on 

 different sites in other parts of the Southwest. The vegetation 

 on Site II was comparatively sparse and more open than on 

 Site I where it was also more luxuriant and vigorous. Those 

 species which were found to overlap on both sites normally made 

 their optimum development on Site I. Approximately twice 

 as many species were found on Site I as on Site II. It is there- 

 fore with some reluctance that certain opinions are advanced 

 regarding the indicator significance of the natural vegetation. 

 The writer is not attempting, however, to state that certain 

 species are positive site indicators or that others are negative 

 indicators. The rather superficial nature of the field observa- 

 tions will only permit of a few more or less general statements 

 concerning the latent possibilities in the use of the native vege- 

 tation in the classification of forest sites and in the determina- 

 tion of their productivity. 



