Biogeochemical cycling constraints on stream ecosystem recovery |
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Authors: | D L DeAngelis P J Mulholland J W Elwood A V Palumbo A D Steinman |
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Institution: | (1) Environmental Sciences Division, Oak Ridge National Laboratory, 37831-6038 Oak Ridge, Tennessee, USA |
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Abstract: | In systems where production is limited by the availability of a nutrient, nutrient input to and recycling within the system
is related to the resilience, or speed of recovery, of a system to its steady state following a disturbance. In particular,
it is shown that the return timeT
s
of the system to steady state, or the inverse of the resilience, is approximately equal to the mean turnover time of the
limiting nutrient in the system. From this relationship, it is possible to understand and predict how various properties of
food webs and their environments affect resilience. These properties include nutrient input rate, loss rate, size of the detritus
compartment, and trophic structure. The effects of these properties on resilience are described by using simple mathematical
models.
To test model predictions, experimental studies of the response of periphyton-dominated stream ecosystems to disturbance are
being conducted on a set of laboratory streams in which nutrient inputs and grazing intensity are regulated at different levels.
In streams without snail grazers (low-grazed streams), 90% recirculation of stream water to reduce nutrient inputs resulted
in longer turnover times (T
r
) of phosphorus within the stream compared with once-through flow. However, in streams with snail grazers (high-grazed streams),
there were no differences in phosphorus turnover time between once-through and partially recirculated treatments. Results
on the rate of recovery of periphyton from a flood/scour disturbance to each stream partially support the model prediction
of a positive relationship between ecosystem return time (T
s
) and nutrient turnover time (T
r
) within the streams. |
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Keywords: | Nutrient limitation Streams Resilience Resistance Artificial streams Periphyton |
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