Is the Longleaf Type a Climax?

What is a climax? The commonly accepted definition is, a type of vegetation which has adapted itself over a long period to a set of environmental conditions, so completely that it is stabilized as long as those conditions remain unchanged. In a narrower sense, a climax type assumes adaptation to a given set of conditions excluding other conditions. The conditions excluded are those which would usually result in disturbance of this stability or equilibrium. These are; fire, under the conception that fire acts to destroy the stand; insects, when epidemic; destructive winds. The effect of imported diseases and insects, or of man's interference in lumbering, destroys the balance and the type may completely change. Climax types may therefore yield at any time to new conditions to which they are not adapted. Excluding the above factors, there would remain only the climatic and soil factors of site. These factors, isolated from the effects of the so-called destructive group, would finally establish a forest type in which the only surviving species would be those capable of enduring the shade of a forest cover during their establishment. This condition necessitates the elimination of fire, wind, insect epidemics and disease for periods longer than the life span of species which cannot endure shade. When, as with Douglas fir, this span is from 300 to 500 years, and the environmental conditions are such as to create extreme conflagration hazard at intervals of from 3 to io years, the establishment of climax types of more shade-enduring species, which are usually inferior in utility, is a pure accident. In the life span of the species, any factor, such as fire, which can be depended on to occur even once within that period, and create conditions favorable to its reproduction, may become the determining factor in its perpetuation as against shadeenduring or so-called climax types. The characteristics of such a relationship are that while fire is required (or its man-made substitute, lumbering) for the removal of the overwood shade and establishment of reproduction, the total exclusion of subsequent fires is equally necessary for survival of this reproduction. The distribution and composition of the forest types in such a region is, therefore, very irregular, much young growth is destroyed prematurely, and here and there a patch may finally attain the climax or shade-enduring type. If for any reason the normal or natural frequency of fire is increased so that its chance of occurrence on any given area becomes once in IO to i5 years, the only hope for survival of the tree species is ability to develop a fire resistant bark within such a period and the fact that the fires when they do occur will