Minor Successions from the Cladonia Mat in Sandy 

 Upland Soil in Northern Michigan 



C[-:dkic L. P()Rti:r and Makjorik L. Woollktt 



During the course of study of the effect of Cladonia and 

 moss mats upon the germination and establishment of seed- 

 lings in the sandy pineland aspen areas at the University of 

 Michigan Biological Station in Cheboygan County, Michigan, 

 during 1927, certain successions were noticed which are here 

 dealt with separately. 



The Cladonia areas undergo distinct succession stages and 

 represent minor associations in themselves. The succession 

 is not always the same, but generally follows one of two courses, 

 (a) If the area be open and unshaded by surrounding trees, 

 the Cladonia will survive for a long period of time. Invasion 

 by other plants is limited to those reproducing by rootstocks, 

 or by a few seedlings which have become established in the 

 cracks between the mounds or cushions of Cladonia. In the 

 area studied these invading plants from rootstocks were limited 

 to Pteris aquilina, Diervilla lonicera, and Vaccinium angiisti- 

 folium. The seedlings found were chiefly of Melampyrum 

 lineare, and occasional seedlings of Aster laevis and Aster 

 macrophyllus. These plants, chiefly the Pteris, slowly drive 

 out the Cladonia by producing shade, and other less tolerant 

 seedlings become established under them. Late stages in this 

 succession show such plants as Oryzopsis asperifolia, Solidago 

 hispida, Aster laevis, Carex wnbellata, and Gaultheria procitmbens 

 well established along with the Pteris and Vaccinium. Thus 

 the Cladonia is gradually broken up and disintegrated, allowing 

 any available seeds to germinate and become established where 

 formerly they would not have had a chance. 



(b) The other type of succession is found in areas where 

 the soil is richer and a little more shaded. In the pure beds of 

 Cladonia rangiferina come up innumerable moss plants, mostly 

 of Polytrichum j uniperinum and Ceratodon piirpureiis. During 

 a wet spell, the spores, lighting on the damp spongy Cladonia 

 find ideal conditions for germination. The protonema grows all 

 through the Cladonia, contact with the soil being unnecessary 

 for their development. From this come up innumerable leafy 

 moss plants which soon begin to crowd out the Cladonia. 



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