Atriplex Communities: Regional Environments and Their Ecological Analysis

Abstract

Judged against the variable background of evolutionary and systematic relationships of Atriplex discussed in the previous three chapters, and the very diverse viewpoints adopted by different authors who have prepared monographs describing regional floristic and vegetation types, there are many ways of preparing a coherent account of Atriplex communities on a global basis. Just as we have taken a rather liberal and pragmatic approach to the systematics of the genus, we shall in this chapter explore some of the more generally recognized vegetation types (“communities”) and environments in which species of Atriplex commonly occur. The difficulties of generalization are exaggerated if one attempts to categorize Atriplex communities in terms of the definition offered by Walter, since it seems unlikely from our field experience that many species of Atriplex are found in “stable combinations” or indeed in “ecological equilibrium” with their environments. Initially we will consider some of the apparent, qualitative relationships between the vegetational and environmental features of these communities, and attempt to distinguish in very general terms the principal environmental factors that appear to be most significant in each vegetation type. In the latter part of this chapter we shall examine some approaches that have been made toward a quantitative analysis of these relationships, approaches that seek to provide a preliminary coupling between states and processes of the vegetation and environment appropriate to nodes in the span 10⁶–10¹¹ of our space-time scale.

“A plant community is understood to be a more or less stable combination of naturally occurring species, which are in an ecological equilibrium with one another and their environment.” (Walter, 1971)