376 Proceedings Portland Society Natural History 



Soon various grasses begin to invade the area and as 

 these become more and more firmly established they replace 

 the herbs as dominant forms. Conspicuous species are Poa 

 pratensis, Agrostis alba, Agrostis hyemalis, Anthoxanthum 

 od oration and Phleum pratense. Gradually a solid turf is 

 formed and this furnishes a habitat for other herbaceous 

 plants, such as Fragaria virginiana, Trifolium procumbens, 

 Hliinantlins Crista-galli, Euphrasia americana, Anaphalis 

 magaritacea and Hieracinni pratense. In this condition 

 the area closely resembles the abandoned fields to be de- 

 scribed below ; and the further stages in development are 

 also similar. 



Association-types of abandoned fields 



When a pasture or hay field is abandoned it grows up 

 chiefly to grasses, as indicated above. In some instances, 

 where there is but little soil, the prominent species are Fes- 

 ttica rubra and Danthonia spicata, and with them various 

 polytrichums and lichens. The first change to be noted in 

 the vegetation of these abandoned fields is the appearance of 

 shrubs and seedling trees, a condition illustrated by Figure 

 23. Among the conspicuous species may be mentioned 

 Juniperus communis var. depressa, the sweet fern (Myrica 

 asplenifolia), blueberries (Vaccinium pennsylvanicum and 

 V. canadense), gray birch, paper birch, and in the moister 

 places Alnus crispa var. mollis. Where this latter species 

 occurs it always spreads very rapidly and soon forms a sol- 

 id thicket, which prevents the invasion of other woody forms. 

 In other cases the shrubs are destined to be succeeded by 

 coniferous trees, which seed in from neighboring areas. The 

 species of most frequent occurrence is the white spruce, 

 which often forms pure stands, one of which is shown in Fig- 

 ure 24. Another common tree is the tamarack (Larix 

 laricina), which exhibits a surprising ability to colonize 

 these old fields. Still again the red spruce and balsam fir 

 may be present. As the conifers increase in number and in 



