Trends Expected in Stressed Ecosystems

The term stress has been widely used for both cause and effect, stimulus and response, or input and output. Although some authors worry about this dual use of the word, I view stress as a syndrome comprising both input and output. One cannot have a response without a stimulus. One can easily identify which part of the syndrome is being singled out by using modifying adjectives, prefixes, or clauses; thus, stress as an input can be designated the stressor as contrasted to stress, the response, or output. (In referring to stress as a syndrome, I do not mean to imply a strict analogy with Selye's [19731 "general stress syndrome," although as recently noted by Rapport et al. 1985, there are interesting parallels between the physiological and community levels.) I believe that common words in everyday language, such as stress, competition, or community should not be given highly technical meanings, since this only serves to confuse the general reader; as already indicated, modifiers can restrict meanings. But we must recognize that these common terms have different meanings, and often different manifestations at different levels of organization. Allen (1984), in discussing hierarchical organization, pointed out that a disturbance detrimental at one level may be beneficial at a higher level. For example, periodic fire in the fire-adapted chaparral is a stress to many organisms