340 ANNUAL BEPORT SMITHSONIAN INSTITUTION, 1913. 



The rate at which leaves decay is greatly inHiieiiced by tempera- 

 ture. In the cooler northern latitudes and at high elevations in 

 lower latitudes the rate of decay is slower and the formation of 

 upland peat is more general than in warmer climates. Except on 

 calcareous soils the higher Appalachian peaks, from 4,000 to 6,000 

 feet, bear an almost continuous layer of upland peat, from a few 

 inches to a foot or more in depth. Their great rhododendron 

 thickets are rooted in deep beds of upland peat. The spruce forests 

 of the higher New England mountains lay down a similar formation. 



In the treeless West the decay of leaves where it is not actually 

 suspended by dryness is rapid and complete. At the higher eleva- 

 tions, however, where the land begins to be timbered the organic 

 matter does not fully decay, and in the heavily timbered areas the 

 deposit of upland peat often becomes characteristically deep' and 

 continuous. In fighting creeping fires in the yellow pine forests at 

 the lower elevations the favorite and most effective tool is the rake, 

 which parts the light leaf litter and puts a stop to the progress of 

 the flames. But in the dense fir and spruce timber the forest ranger's 

 chief tools are the spade and the mattock, with which he must cut 

 through the thick layer of dry peat to the mineral soil beneath if he 

 IS to effectually combat a slowly creeping fire. 



So strong is the tendency to the formation of peat under the low 

 temperatures and heavy precipitation of the high mountains that 

 even on limestone soils a superficial layer of upland peat is sometimes 

 accumulated. Such a condition exists on innumerable areas at an 

 elevation of about 10,000 feet in the Manti National Forest of Utah. 

 On the basaltic plateau of extreme northeastern Oregon, where the 

 soil is naturally alkaline in reaction the lodgepole pine and Douglas 

 fir forests at elevations of 5,000 feet and over lay down a continuous 

 bed of peat which supports a characteristic acid flora. A quantita- 

 tive test of one of the acid flora soils of this region, at an elevation 

 of 8,000 feet, showed the customary high acidity at the surface, and 

 successively lower degrees of acidity underneath, until at the depth 

 of 5 feet, at the surface of the basaltic rock, the reaction was neutral. 



The group of plants that forms the best index to the acid char- 

 acter of a soil is the family Ericaceae, and the related families 

 Vacciniacese and Pyrolacese. "Wlien these occur in vigorous growth 

 on a calcareous soil or among calcareous rocks, as is sometimes 

 reported, one may expect to find, as the speaker in his own experience 

 has always found, that a layer of upland peat has been formed 

 above the calcareous substratum and that in this superficial layer the 

 roots of the plants find their nourishment, really in an acid medium, 

 notwithstanding the alkalinitj^ beneath. 



Continued observations on the association of certain types of 

 wild plants with acid and nonacid soils, supported by cultural experi- 



