THE DECIDUOUS FOEEST CLIMAX. 211 



deepens, grasses enter, especially Andropogon scoparius and Poa compressa, 

 together with Antennaria, Aster, Lespedeza, etc. The shrub stage which suc- 

 ceeds is characterized by Ceanothus, Gaylussacia, Myrica, Prunus, Qiiercus, 

 Rhus, Rosa, and Vacdnium. The first trees to appear are Juniperus virginiana 

 and Quercus stellata. These are followed by Qiiereus prinus and Carya glabra, 

 with which are later associated Acer rubrum, Carya alia, C. ovata, Pinus 

 strdms, and Qmrcus alba, cocdnea, rubra, and velutina. Under favorable con- 

 ditions, the oak-hickory forest gives way to the cl imax of Castanea dentata 

 and lAriodendron tulipifera, with which occur Acer, Fagus, Tilia, Tsuga, 

 Fraxinus, and Prunus, mostly scattered or abundant locally. 



Roberts (1914 : 443) has summed up her study of succession in the Holyoke 

 Range of Massachusetts as follows : 



"1. The region is a mountain range of trap rock. 



"2. The climax forest of the region is of the beech-maple-hemlock type. 



"3. The successions may be classified as: 



"I. Xerarch successions: (1) trap slope successions; (2) trap cliff succes- 

 sions; (3) talus successions. 



"II. Hydrarch successions: (1) ravine successions; (2) brook successions. 



"4. The terms initial and repetitive seem to be better than primary and 

 secondary in conveying the idea of often-repeated successions such as are 

 found in a frequently deforested area (c/. p. 170). 



"5. The east-facing and the south-facing trap slopes have the same succes- 

 sions. Castanea dentata seems to present a temporary cUmax. 



"6. The trap cliff doubtless presents an initial succession in which the east 

 and north cMs have similar first stages, but the second stage on the east is 

 Pinus strobus and Pinus resinosa, whole on the north it is Tsuga canadensis." 



Fuller (1911, 1912, 1914) has measured the evaporation and water-content 

 in various associes of the dune sere of Lake Michigan, and has embodied his 

 results in the following summary: 



" 1. These data represent the evaporation rates in the lower aerial stratum 

 and the range of soil moisture in the upper subterranean strata of the vegeta- 

 tion of the various associations, but these must be regarded as critical regions, 

 since within them develop the seedlings which determine the character of 

 succeeding vegetation. 



"2. Evaporation at different stations in the same plant association exhibits 

 variations similar in character and degree. 



"3. The rate of evaporation in the cottonwood dune association, both by 

 its great amount and by its excessive variation, seems a quite siifficient cause 

 for the xerophytic character of the vegetation and for the absence of under- 

 growth, in spite of the constant presence of growth-water. 



"4. The pine and oak dune associations resemble one another closely both 

 in their mean evaporation rates and in their supply of growth-water. The 

 former is slightly more xerophytic during the midsummer weeks. 



"5. The vernal vegetation of the pine dune is quite as mesophytic as that 

 of the succeeding association, thus agreeing with its lower evaporation rate 

 during that portion of the year. 



"6. The evapora,tion rates and the amount of growth-water in the various 

 associations vary directly with the order of their occurrence in the succession 

 the pioneer being the most xerophytic in both respects. ' 



"7. The ratios between evaporation and growth-water in the beech-maple 

 forest, oak-hickory forest, oak dune, pine dune, and cottonwood dune asso- 



n 



