Material Spiraling in Stream Corridors: A Telescoping Ecosystem Model |
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Authors: | Stuart G Fisher Nancy B Grimm Eugènia Martí Robert M Holmes Jeremy B Jones Jr |
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Institution: | (1) Department of Biology, Arizona State University, Tempe, Arizona 85287, USA , US |
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Abstract: | Stream ecosystems consist of several subsystems that are spatially distributed concentrically, analogous to the elements
of a simple telescope. Subsystems include the central surface stream, vertically and laterally arrayed saturated sediments
(hyporheic and parafluvial zones), and the most distal element, the riparian zone. These zones are hydrologically connected;
thus water and its dissolved and suspended load move through all of these subsystems as it flows downstream. In any given
subsystem, chemical transformations result in a change in the quantity of materials in transport. Processing length is the length of subsystem required to “process” an amount of substrate equal to advective input. Long processing lengths
reflect low rates of material cycling. Processing length provides the length dimension of each cylindrical element of the
telescope and is specific to subsystem (for example, the surface stream), substrate (for instance, nitrate), and process (denitrification,
for example). Disturbance causes processing length to increase. Processing length decreases during succession following disturbance.
The whole stream-corridor ecosystem consists of several nested cylindrical elements that extend and retract, much as would
a telescope, in response to disturbance regime. This telescoping ecosystem model (TEM) can improve understanding of material
retention in running water systems; that is, their “nutrient filtration” capacity. We hypothesize that disturbance by flooding
alters this capacity in proportion to both intensity of disturbance and to the relative effect of disturbance on each subsystem.
We would expect more distal subsystems (for example, the riparian zone) to show the highest resistance to floods. In contrast,
we predict that postflood recovery of functions such as material processing (that is, resilience) will be highest in central
elements and decrease laterally. Resistance and resilience of subsystems are thus both inversely correlated and spatially
separated. We further hypothesize that cross-linkages between adjacent subsystems will enhance resilience of the system as
a whole. Whole-ecosystem retention, transformation, and transport are thus viewed as a function of subsystem extent, lateral
and vertical linkage, and disturbance regime.
Received 15 April 1997; accepted 1 September 1997. |
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Keywords: | : stream riparian disturbance nutrients hyporheic hydrology telescoping ecosystem |
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