DEVELOPMENT OF ASSOCIATION AND CLIMAX CONCEPTS 33 1 



istics and, according to the nomenclature so far suggested, may be called an 

 association. Are they distinct and separate units, or are they related one to 

 another? The primary pin oak association is normally an open forest of 

 large trees occupying poorly drained areas wet or swampy in spring. Pin oak 

 is an intolerant species — in spots between the large old trees may be seen 

 younger individuals of this species, but in shady spots beneath the canopy 

 formed by groups of pin oaks, other species occur, shagbark hickory and 

 perhaps an occasional white oak or beech. As long as open spots remain, ecesis 

 of pin oak is possible, but when the canopies of primary trees and older 

 reproduction join, further ecesis of pin oak ceases. Gradually the older pin 

 oak trees die out and the older individuals of other species of the understory 

 replace them. Vegetational change is taking place, succession is in progress. 

 Replacement takes place individual by individual — there is no jump from 

 pin oak dominance to dominance by another species. Wherever a pin oak 

 started in an open spot it may persist along with the new entrants which 

 are changing the habitat by their deeper shade and their different leaf litter. 

 After many forest generations and centuries of occupancy, a forest in which 

 white oak is dominant may come into being. The old white oak forest, with 

 trees 3 to 4 feet in diameter, again reveals evidence of change. Beech trees 

 of various ages are interspersed, but white oak is absent from lower layers. 

 Gradual dying out of white oak and growing to maturity of beech leads to 

 the establishment of a beech forest. Beech, the most tolerant species of the 

 area, is able to reproduce and perpetuate itself. Succession has been taking 

 place because of biotic forces at work and has apparently ended in an un- 

 changing or very slowly changing community — a climax of some sort. 



Within any single forest tract the distribution of earlier and later develop- 

 mental stages appears to be related to almost imperceptible topographic dif- 

 ferences — depressions and swells differing but a few inches in elevation. But 

 comparison with another tract may disclose that "earlier" stages are lacking 

 and that "later" ones may occupy a greater variety of sites. The whole tract 

 appears as a mixed forest, its unlike component communities often small in 

 extent. It is a pattern of intergrading developmental and climax communities, 

 not a climax pattern due to micro-relief (as suggested by Whittaker, 1953, 

 p. 45). When analyzed by statistical methods of recent years, with quadrats 

 laid out arbitrarily in a grid pattern (as has been done), with all trees above 

 a certain diameter counted, and with basal areas determined, evidence of 

 unlike communities within the tract is obscured and evidence of succession 

 is lost. With this loss, the most fundamental concepts of vegetation are en- 

 dangered. 



Only after repeated field surveys of such tracts and only after the processes 

 at work are thoroughly understood and the relationships of parts of the 

 forest determined, could statistical methods be applied. Continuous transects, 

 with vegetation related in so far as possible to environment, supply the most 



