THE DECIDUOUS FOEEST CLIMAX. 189 



Helianthus, and Urtica. At this point the east section became pasture, in 

 which Carduus Ixmceolatus promised to become dominant. Five species of 

 Salix had appeared in the west section, together with a few thrifty individuals 

 of Cottonwood and aspen, one Po-pxdus halsamifera, and one Ulmus fulva. 

 Although Rhits, Corylus, Acer, Viburnum, Carnus, and QiLercus grew within 

 a stone's throw of the island, not one individual had appeared upon it. 



Livingston (1902, 1903) has studied the upland and lowland communities of 

 Kent County, Michigan, with respect to water relations, and has pointed out 

 their general place in the succession. The upland societies are five, as follows : 



The oak-pine-sassafras society, dominated by Quercus alba, Q. rubra, Pinv^s 

 strobus, and Sassafras, is foimd in the deepest "oak openings," as well as in 

 areas once covered by white pine. The oak-hazel society is a mere variant 

 of this, it seems, and the oak-hickory society, consisting of Q. alba, Q. rubra, 

 Carya alba, and C. pordna, apparently represents a somewhat later stage of 

 the same association. This is followed by the maple-ehn-agrimony society, 

 dominated by Acer saccharum, Ulmus americana, and U. racemosa, which is 

 found in the heavier soils where it represents a transition to the final stage, the 

 beech-maple society {Fagus ferruginea and Acer saccharum), on heavy clay 

 soils as a rule. The sequence of the lowland societies is less definite, but the 

 initial stages are represented by the Chara-Nymphaea society of ponds or 

 lakes, and the Potamogeton-MyriophyUumr-Elodea society of lakes and rivers. 

 The Carex-Sphagnum-Larix society is evidently a complex of stages, as is also 

 true of the Salix-Fraxinus-TJlmus society. The Tilior-CeUis-Phlox society is 

 typical of the river flood-plain, and is a subclimax. 



Reed (1902) has studied the development of vegetation of a glacial lake in 

 Michigan, describing in it five concentric zones : 



The center, characterized by Chara and Potamogeton in other lakes, is with- 

 out vegetation, probably owing to the feeble illumination below 20 feet. The 

 inner zone consists almost whoUy of Potamogeton zosteraefolius with some P. 

 lucens. This zone is about 30 feet wide and extends from 6 to 18 feet in depth. 

 The second zone of Nuphar advena is from 30 to 70 feet wide and extends from 

 the water's edge to 6 feet in depth. The associated plants are Potamogeton, 

 Chara, Dulichium, and Typha. The third zone of Carex and Sphagnum extends 

 landwards from the water's edge, from 6 to 25 feet. The soU imderlying it is 

 composed entirely of black muck with much decaying vegetable matter. The 

 characteristic plants are Carex filiformis. Sphagnum, and Potentilla palustris. 

 The fourth zone consists of Salix alba vitellina, S. lucida, S. myrtilloides, 

 Populus tremuloides, and XRmus americana. The fifth zone of grasses and 

 composites especially, is a transition to the surrounding vegetation. 



The various zones are slowly encroaching upon the lake and fillin g it with 

 the soil they produce. Each community forms soil more or less actively in 

 its reaction upon its particular area. The author states that the intense com- 

 petition of the Nuphar zone produces a constant tendency to move in the 

 direction of least resistance, namely, into the Potamogeton zone. This is 

 obviously a figurative way of sasing that the propagules which find their way 

 into the Potamogeton zone have the best chance of establishment. Wherever 

 the bottom is built up to within 3 or 4 inches of the surface, Carex establishes 

 itself, covering the soft muck with a quaking mat of vegetation. Sdrpus 

 lacustris is one of the foremost plants in this advance, but is finally crowded 

 out by Salix rostrata and Betula pumila. Ultimately the lake entirely dis- 

 appears and the zones alone indicate its original position. 



