OVERGRAZING. 



299 



three groups comprise the characteristic relict indicators, and for the most 

 part mark the early stages of overgrazing. The annuals and weeds are typical 

 of the later and final stages, while the shrub indicators are typical of savannahs 

 and other ecotones where grass and scrub mix. The increased importance of 

 societies marks the beginning of overgrazing in those associations where they 

 are regularly present. These consist for the most part of climax herbs, but 

 subclimax half-shrubs and grasses, such as Gutierrezia and Aristida, are often 

 of especial significance. Moreover, many of the herbs, though regularly 

 present in the climax, have subclimax qualities also, as is readily understood 

 from their competitive relations to the grasses. Practically all the societies 

 listed under the various associations of the grassland, as well as those of the 

 other climaxes, have some value as indicators of overgrazing. In most cases 

 this value is overshadowed by that of the most controlling and extensive 

 societies, and the latter alone need to be taken into account. 



In the following list the general order is that of importance, but this 

 naturally varies with the locality and the season. The composites and other 

 late-blooming species are especially serviceable, owing to their persistence 

 (plate 75). 



Artemisia gnaphalodes. 

 Artemisia dracunculoides. 

 Artemisia canadensis. 

 Grindelia squarrosa. 

 Solidago rigida. 

 Solidago missoiiriensis. 

 Solidago speciosa. 

 Solidago canadensis. 

 Solidago mollis. 

 Liatris pimctata. 

 Liatris scariosa. 

 Liatris spicata. 

 Liatris pycnostachya. 

 Lepachys columnaris. 

 Kuhnia glutinosa. 

 Malvastnim coccineum. 

 Vernonia fasciculata. 

 Vemonia baldwinii. 

 Achillea millefolium. 

 H^anthus rigidua. 

 Csrduus imdulatus. 



Senecio douglasii. 

 Aster multiflorus. 

 Aster oblongifolius. 

 Aster sericeus. 

 Senecio aureus. 

 Balsamorhiza sagittata. 

 Balsamorhiza deltoidea. 

 Psoralea tenuiflora. 

 Psoralea argophylla. 

 Petalostemon candidus. 

 Petalostemon purpureus. 

 Amorpha canescens. 

 Amorpha nana. 

 Dalea laziflora. 

 Tradescantia virginiana. 

 Verbena striata. 

 Verbena hastata. 

 Glycyrhiza lepidota. 

 Braimeria pallida. 

 Chrysopsia villosa. 



Lygodesmia juncea. 

 Aragalus lamberti. 

 Polygala alba. 

 Antennaria dioeca. 

 Astragalus mollissimus. 

 Astragalus bisulcatus. 

 Astragalus racemosus. 

 Astragalus crassicarpus. 

 Lupinus plattensis. 

 Erigeron ramosus. 

 Haplopappus spinulosua. 

 Hymenopappua tenuifolius. 

 Rosa arkansana. 

 Euphorbia corollata. 

 Salvia azurea. 

 Asclepias verticillata. 

 Monarda fistulosa. 

 Baptisia leucophaea. 

 Castilleia sessiliflora. 

 Allium canadenae. 



Ilalfshrubs as indicators. Halfshmbs are best developed in the South- 

 west, where they are typical indicators of overgrazing in both the desert scrub 

 and the desert plains. A few attain even greater importance in the short- 

 grass plains and the mixed prairies. These are Gutierrezia sarothrae, Artemi- 

 sia frigida, and Yucca glauca. The relation of the first two to grazing in a 

 short-grass cover has been shown by Shantz (1911:42). Over the central 

 portion of the Great Plains they are associated as the two most serviceable and 

 universal of overgrazing indicators. Artemisia is more abundant to the 

 northward, and Gutierrezia to the southward, but they indicate essentially the 

 same conditions whether alone or mixed. Differences in the degree of over- 

 grazing are designated by variations in the density and vigor of the plants. 

 In rough or sandy r^ons Yucca glauca is an indicator of overgrazing, though 

 it is less important than the two just mentioned, largely because the flower- 

 clusters are often eaten by cattle. Eriogonum microthecum and its variety 

 effusum are conmion indicators in the central Great Plains, especially in more 



