Characteristics of Lotic Ecosystems and Consequences for Future Research Directions

摘要: Stream ecologists often have more problems than others in defining the boundaries of their operational unit “ecosystem” because running waters are essentially open systems: they closely linked to terrestrial ecosystems through long shoreline; and water ail streams earth has, statistically, a turnover rate about 2 weeks (Czaya 1981). Recent books (Barnes Minshall 1983; Fontaine Bartell Resh Rosenberg 1984) discussed various means by which stream communities respond this openness. This chapter concentrates on two major aspects response possibilities limitations ecosystem analyses largely depend: (1) that viewed as old, co-evolved well- adapted entities (Vannote et al. 1980), systems can adapt biological organization very fast changing environmental conditions (Townsend Hildrew 1984), or even physically biologically controlled (Reice 1985); (2) intermediate levels fluctuations disturbances produce high species diversity (intermediate disturbance hypothesis), maximum is expected mid-reaches watersheds 1980; Stanford Ward 1985).