SOME RIPARIAN DEFINITIONS

The following definitions and the conceptual frame they provide were used both in the design of the conference and the preparation of this volume. While the editors did not attempt to achieve absolute uniformity of definition in order to accommodate strong author terminological preferences, considerable effort was made to minimize ambiguity and approach standardization of the most widely used descriptors. While all readers may not agree or be comfortable with all definitions, all will at least understand what the authors are trying to say.

It is important to discern at the outset that the "riparian" concept has had a specific ecological context for well over two thousand years. The present day riparian concept and its derivative terms (riparian, riparial, riparious) all come from the Latin Riparius , which itself derives from the Latin Ripa (Pl. Ripae ) meaning bank or shore, as of a stream or river. The original meaning has been largely retained through subsequent history, i.e., pertaining to the terrestrial, moist soil zone immediately landward of aquatic wetlands, other freshwater bodies, both perennial and intermittent watercourses, and many estuaries.

While the original Latin usage apparently related to freshwater/upland and estuarine/upland interfaces, the term has occasionally been applied to coastal shore zones. There is presently no clear concensus as to its applicability to coastal shorelines, but a conservative interpretation (which we prefer) would probably exclude them.

Despite numerous attempts, no single purely descriptive definition embracing riparian systems—that is, one that attempts to define by listing all the different types of riparian phenomena—has proven successful. There are far too many types of riparian systems to be encompassed in a single descriptive statement. Such all-inclusive descriptive definitions have inevitably proven both too unwieldy and less than totally encompassing of all significant riparian phenomena.

Last, it is useful to recognize that the term "riparian" isanadjective . The term, once defined, can thus usefully modify a multitude of other well-accepted terms. This process leads in a straight-forward manner to a set of riparian definitions that is functional and easily understood. The linch-pin or common denominator is of course the term "riparian." Once that has been adequately defined, everything else falls into place. Proceeding in a sequence that builds logically, the following definitions are offered.

RIPARIAN: pertaining to the banks and other adjacent terrestrial (as opposed to aquatic) environs of freshwater bodies, watercourses, estuaries, and surface-emergent aquifers (springs, seeps, oases), whose transported freshwaters provide soil moisture sufficiently in excess of that otherwise available through local precipitation to potentially support the growth of mesic vegetation.

AQUATIC: growing or living in or frequenting water; taking place in or on water.

ZONE: an area surrounde by boundary lines; a region or area set off as distinct from surrounding or adjoining parts.

WETLAND: a zone that is periodically, seasonally, or continuously submerged or which has high soil moisture; which may have both aquatic and riparian components, and which is maintained by transported water supplies significantly in excess of those otherwise available through local precipitation.

UPLAND: the ground above a floodplain; that zone sufficiently above and/or away from transported waters as to be dependent upon local precipitation for its water supplies.

POPULATION: a group of individuals of the same species inhabiting a specific zone or system.

HABITAT: the ecological and/or physical place determined and bounded by the needs and the presence of a specific plant or animal population, which contains a particular combination of environmental conditions sufficient for that population's survival. Similar or equivalent to "niche".

VEGETATION: the total plant cover or plant life of a zone or area.

FAUNATION: the total animal life of a zone or area; the animal equivalent of vegetation.

ASSOCIATION: a collection of units or parts into a mass or whole (e.g., a group of animals, plants, or both). A statement of physical proximity or grouping, without necessarily requiring or implying interactions between units of the group, in contrast to "community", which does. Similar or equivalent to "aggregation."

COMMUNITY: an association of living organisms having mutual relationships among themselves and to their environment and thus functioning, at least to some degree, as an ecological unit.

SYSTEM: a group of related natural objects and/or forces within a defined zone; a regularly interacting or interdependent group of items forming a unified whole; a more general and less rigorous term than "ecosystem".

ENVIRONMENT: the complex of factors that act upon an organism or an ecological community and ultimately determine its form and survival.

ECOSYSTEM: the interacting complex of a community and its environment functioning as an ecological unit in nature. Differs from "system" in being a more rigorous definition that encompasses and requires assumptions of energetics, ecological interactions, species adaptations, and so forth.

A RIPARIAN ZONE is thus a delimited of riparian (moist soil) substrate, within whose boundaries may grow a RIPARIAN VEGETATION, which in turn may support a RIPARIAN FAUNATION. The riparian vegetation and riparian faunation in turn comprise one or more plant, animal, or biotic RIPARIAN ASSOCIATIONS, which, if the populations are known to interact and to have mutual relationships among themselves and their environments, constitute a RIPARIAN COMMUNITY. Each POPULATION of plant or animal so involved has its own population-specific HABITAT, determined and delimited by the specific physiological and ecological requirements of that population. All are part of and exploit a RIPARIAN ENVIRONMENT, and in so doing become parts of a RIPARIAN ECOSYSTEM. A RIPARIAN SYSTEM denotes, in a generalized way, a site-specific set of riparian phenomena without necessarily connoting an entire riparian ecosystem. Where the riparian plant and aminal life has been stripped off or otherwise destroyed, the remnant riparian system may consist of only the remaining geologic riparian zone. The riparian zone in turn may be reduced or even destroyed by the diversion or other loss of its transported water supplies.

Applying this terminology with respect to wetlands, there are permanently inundated AQUATIC WETLANDS (having water depths of two meters or less) with saturated soils and hydrophytic plants; and less frequently to never inundated RIPARIAN WETLANDS with moist soils and mesophytic plants. Riparian wetlands are bounded on their outer or drier sides by yet more xeric UPLANDS, which are usually higher in elevation and still further removed from the transported water supplies.