On the multiple ecological roles of water in river networks
Abstract
The distribution and movement of water can influence the state and dynamics of terrestrial
and aquatic ecosystems through a diversity of mechanisms. These mechanisms can be
organized into three general categories wherein water acts as (1) a resource or habitat
for biota, (2) a vector for connectivity and exchange of energy, materials, and organisms,
and (3) as an agent of geomorphic change and disturbance. These latter two roles are
highlighted in current models, which emphasize hydrologic connectivity and geomorphic
change as determinants of the spatial and temporal distributions of species and processes
in river systems. Water availability, on the other hand, has received less attention
as a driver of ecological pattern, despite the prevalence of intermittent streams,
and strong potential for environmental change to alter the spatial extent of drying
in many regions. Here we summarize long-term research from a Sonoran Desert watershed
to illustrate how spatial patterns of ecosystem structure and functioning reflect
shifts in the relative importance of different 'roles of water' across scales of drainage
size. These roles are distributed and interact hierarchically in the landscape, and
for the bulk of the drainage network it is the duration of water availability that
represents the primary determinant of ecological processes. Only for the largest catchments,
with the most permanent flow regimes, do flood-associated disturbances and hydrologic
exchange emerge as important drivers of local dynamics. While desert basins represent
an extreme case, the diversity of mechanisms by which the availability and flow of
water influence ecosystem structure and functioning are general. Predicting how river
ecosystems may respond to future environmental pressures will require clear understanding
of how changes in the spatial extent and relative overlap of these different roles
of water shape ecological patterns. © 2013 Sponseller et al.
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https://hdl.handle.net/10161/8358Published Version (Please cite this version)
10.1890/ES12-00225.1Publication Info
Sponseller, RA; Heffernan, JB; & Fisher, SG (2013). On the multiple ecological roles of water in river networks. Ecosphere, 4(2). 10.1890/ES12-00225.1. Retrieved from https://hdl.handle.net/10161/8358.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
James Brendan Heffernan
Associate Professor of Ecosystem Ecology and Ecohydrology
I am interested in major changes in ecosystem structure, particularly in streams,
rivers and wetlands. My work focuses on feedbacks among ecological, physical, and
biogeochemical processes, and uses a wide range of tools and approaches. I am particularly
interested in projects that address both basic ecological theory and pressing environmental
problems. Increasingly, we are applying tools and theories developed for local ecosystems
to better understand ecological patterns and mechanisms at regi

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