TABLE 8-2 Ecological seasons (Ma 



Aspect Sector 



Characteristics 



Early November to late March. 



Hiemine Deciduous trees nearly bare, 



herbs mostly dead except for 

 winter-green species (Beatley 

 1956); Insects, other inverte- 

 brates, some mammals, going 

 into hibernation or dormancy; 

 last migrant birds disappear. 



Hibernine Deep winter condition, little 

 animal activity evident except 

 winter resident birds in shel- 

 tered locations and a few 

 mammals. 



Emerginine Some buds swell and subterra- 

 nean sprouts begin to appear 

 above ground, earliest migrant 

 birds appear, animals begin- 

 ning to emerge from hiber- 

 nation. 



Early April to late May. 



Prevernine First appearance of flowers 

 both of herbaceous and tree 

 species; mammals and perma- 

 nent resident birds begin re- 

 productive activities; sala- 

 manders go to ponds and lay 

 their eggs; all insects, snails, 

 and other invertebrates come 

 out of hibernation. 



Vernine Deciduous trees now fully foli- 



ated, early spring flowers re- 

 placed by species that tolerate 

 shading; bird migration reaches 

 its peak; insects and inverte- 

 brates become abundant in all 

 strata. 



and arctic regions, seasonal differences in length of 

 day and temperature become increasingly great the 

 closer the region lies toward a pole. 



Correlated with seasonal changes in climate are 

 adaptive adjustments of metabolism and energy bal- 

 ances, regulation of breeding time, change in food 

 habits, and migration or hibernation. Birds breed in 

 the spring and early summer, since lengthening daily 

 photoperiods stimulate maturing of the gonads 

 (Burger 1949). Photoperiodism also controls the 

 breeding time of some mammals, fish, and inverte- 

 brates as well as plants. However, in some species, 

 say trout and deer, shortening rather than lengthen- 

 ing photoperiods are stimulating, and such species 

 regularly breed during the autumn. 



In deciduous forests, seasonal differences in the 

 development of the foliage greatly affect animals. 

 When trees are bare, sunlight penetrates to the forest 

 floor more readily than when foliage is in full devel- 

 opment. Foliage is important because it is protective 

 cover from weather and offers refuge and conceal- 

 ment from predators ; to many species it is a direct 

 source of food. 



Four main ecological seasons, or aspects, may be 

 recognized ; each aspect is divisible into secondary 

 periods, or sectors (Table 8-2). These periods are 

 best developed in the temperate deciduous forest but 

 also occur in modified form in other communities as 

 well. The beginning and end of any aspect cannot be 

 set with exactness, since aspects vary from year to 

 year, with latitude and type of community. 



Substratum 



Early June to middle August. 

 Reduced number of flowering 

 herbs but vegetative growth at 

 maximum, birds at height of 

 nesting. 



Deciduous forest becomes hot 

 and dry, many ground plants 

 dry up; birds quiet and entering 

 molt, molluscs aestivate, foli- 

 age insects attain maximum 

 populations. 



Middle August to early No- 

 vember. 



Fruits and nuts ripen, autumn 

 flowers come into bloom, birds 

 at height of southward migra- 

 tion, mammals reach maximum 

 populations but invertebrates 

 decreasing. 



Foliage of deciduous trees 

 changes color and falls, insect 

 and spider populations shift 

 from higher strata to the 

 ground. 



The substratum greatly influences the kind of 

 plants and animals that occur in the pioneer stages 

 of succession. Bare rock presents one extreme physi- 

 cal habitat, sand another, and clay yet another. The 

 substratum affects animals indirectly in terms of the 

 kinds of plants it supports and the variety of niches 

 it affords. Differences between early sere stages not- 

 withstanding, later ones tend to be more and more 

 alike so that convergence occurs. In temperate hu- 

 mid regions, where the seres pass through several 

 stages, the climax communities of all seres are very 

 much alike regardless of the type of bare area on 

 which they originated. 



ROCK SERE 



Plant communities 



Stages in the plant sere on bare rock are 

 lichens, mosses, annual herbs and grasses, shrubs. 



102 Habitats, communities, succession 



