TYPE STAGES OF INDICATOR PLANTS 107 



palatable perennials. The conspicuous presence of vegetation 

 of this kind indicates severe overgrazing. It occurs character- 

 istically on badly eroded areas and on long-used sheep trails and 

 bed grounds. The indicators of overgrazing here enumerated 

 are found on lands in the advanced stages of depletion. 



Indicators of Slight Departures in Grazing Capacity. — A 

 large number of plants that occur on range and pasture are 

 valuable as indicators of the early or moderate stages of over- 

 grazing. Two sets of plants, however, namely, those that are 

 palatable to stock, and those that are known to occupy inferior 

 soils, are the most reliable indicators. Overstocking or some 

 other form of overgrazing is indicated whenever the highly 

 palatable species are so closely cropped that their luxuriance of 

 growth and ability to reproduce are impaired. The inferior plant 

 forms, or those that characteristically inhabit eroded, heavily 

 packed, or otherwise impaired soils, are valuable as indicators of 

 moderate overgrazing, as well as of serious depletion, because 

 they invariably appear as soon as the original cover of desirable 

 plants is even slightly weakened or opened up. After the de- 

 struction of the palatable perennial plants, the annual or short- 

 lived perennial weeds of the lower stage make their appearance. 

 They reproduce abundantly and make good growth because of 

 the larger share of water and light which they receive in the 

 absence of the former cover. 



Type Stages of Indicator Plants. — A careful classification of 

 the vegetation up and down the scale of successional develop- 

 ment into divisions which can readily be recognized justifies 

 grouping herbaceous pasture vegetation into four stages. In 

 his study of the application of the principles of plant succession 

 to natural range reseeding in the Wasatch Mountains in central 

 Utah, the author classified the developmental stages as follows:^ 

 (i) Climax herbaceous stage (the wheatgrass cover); (2) mixed 

 grass and weed stage (the porcupinegrass-yellowbrush cover); 



' Sampson, .^thur W., "Plant Succession in Relation to Range Management." 

 U. S. Dept. of Agr. Bui. ygi, p. 7, 1919. The principles developed in the inves- 

 tigations reported in this bulletin, covering about thirteen years of study in the 

 West, are applicable to pasture lands generally, and hence are briefly reviewed 

 here. 



