Bergman and StaUard: climax formations 357 



forest undergrowth, various species of Cladonia, especially C. 

 gracilis. C. cristatella, C. finibriata, C. pyxidata and C. verticillata, 

 appear on the partly burned stumps and half -buried trunks and 

 branches of trees. Scattered lichens and mosses may occur also 

 over the surface of the ground, which is otherwise bare. Succes- 

 sions beginning with this stage, however, are rather rare, owing to 

 the ease with which herbaceous or woody invaders may enter. 



(2) The Herbaceous Associes 



The usual point at which secondary sviccession begins after a 

 fire is with the appearance of herbs and grasses. In the northern 

 and northeastern part of the state, Chamaenerion is often the domi- 

 nant species. With this in greater or lesser abundance are to be 

 found species of Aster and Solidago. In some places, indeed, the 

 latter genera vie with Chamaenerion as to abundance. Grasses such 

 as Agrostis hienialis, Muhlenbergia mexicana, Panicnm xanthophy- 

 sum, Agropyron tenerum, and Elynnis canadensis are nearly always 

 present. Agrostis is usually the most abundant. 



Other species usually present with the above are : 



Anaphalis margaritacea Leptilon canadense 

 Cardnns altissiniiis Onagra biennis 



Lactuca sp. Pteris aquilina 



In places where the soil is very sandy, the succession shows con- 

 siderable difference from the above. In such places the secondary 

 succession after fire or clearing begins with grasses. Danthonia 

 spicata is often dominant, occurring alone or with an intermixture 

 of Fesiica ovina. In places not occupied by grass, Arctostaphylos 

 uva-ursi is often found, at times spreading over quite extensive 

 patches. Other plants occurring with these are the following : 



Antennaria canadensis Oryzopsis micrantha 



Aster laevis Panicnm xanthophysum 



Lacinaria scariosa Solidago nemoralis 

 Lechea strict a 



A third variation in sequence is found to exist. This, too, is 

 found in sandy soil and near the southern limit of the pine forest 

 approaching the prairie. Here a burned or cleared area soon passes 

 into an Andropogon socies with A. furcatns as the dominant species. 

 A. scoparius, Stipa sparfea, Agropyron caninnm and Poa nemoralis 



