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Abstract How much stream temperatures increase within riparian canopy openings and whether stream temperatures cool downstream of these openings both have important policy implications. Past studies of stream cooling downstream of riparian openings have found mixed results including rapid, slow, and no cooling. We collected longitudinal profiles of stream temperatures above, within, and below riparian forest openings along stream segments within otherwise forested riparian conditions to evaluate how sensitivity of stream temperatures to riparian conditions varied across landscape factors. We conducted these temperature surveys across openings in 12 wadeable streams within and near the Upper Little Tennessee River Basin in western North Carolina and northeastern Georgia. Basin areas ranged from 74 to 6,913 ha, and bankfull channel widths varied from 3.4 to 16.4 m. Stream temperatures were collected every 15 min using HOBO® data loggers for 2 weeks in each stream, repeated later in summer in some streams. Reference temperatures were highest in stream reaches at low elevations and with large drainage areas. Stream temperature increases in the middle of riparian gaps were highest when streams drained small high‐elevation watersheds, and increases at the end of openings were highest when the opening length was large relative to watershed size. Downstream from openings, cooling rates were greatest in small, high‐elevation headwater streams and also increased with larger increases in canopy cover. Stream segments that warmed the most within openings also featured higher cooling rates downstream. The data show that stream temperature sensitivity to canopy change is highly dependent on network position and watershed size. A better understanding of stream temperature responses to riparian vegetation may be useful to land managers and landowners prioritizing riparian forest restoration.
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Grass versus trees: A proxy debate for deeper anxieties about competing stream worlds
Stream restoration has become an increasingly important focus in southwestern Wisconsin's Driftless Area, an unglaciated, hilly pocket of the Upper Mississippi River Basin rich in groundwater-driven coldwater streams, recreationally important trout species, and agricultural communities. Climate change is driving a major increase in precipitation and flooding across this rural and often under-resourced region, effects complicated by the ongoing legacies of white settlement and the changes it wrought to area streams, including the burial of floodplains in sediment displaced off area hillslopes. As managers work to consider how to “restore” Driftless streams, riparian vegetation—grass versus trees—has become a central and surprisingly controversial node. Current stream restoration practice typically includes the removal of riparian trees, though that practice has come under increasing criticism. Grounded in more than 5 years of qualitative and biophysical fieldwork in the region, we build from interviews gathered with 18 Driftless Area stream restoration managers from 2018 to 2020 to point to the ways that managers leverage arguments about erosion, flooding, habitat, and angler access, among other things, in service of grass and trees. Indexing the surface flows and underflows of this restoration debate, we introduce the rhetorical concept of the proxy debate to argue that debates about grass versus trees are tethered to competing perspectives on scale, temporality, and dynamism, surficial distractions from much deeper anxieties about what a stream is and should be. We turn to the ways that these distractions serve to further distance the stream restoration enterprise from acknowledging the ongoing human and hydrologic legacies of settler colonialism, and we close by suggesting that careful attention to rhetorical power—both to what arguments say and do, and to what they elide—offers a tentative first step toward restoring lands and relations by questioning what is taken for granted and what lies beneath.
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- Award ID(s):
- 2009353
- PAR ID:
- 10472403
- Publisher / Repository:
- SAGE Publications
- Date Published:
- Journal Name:
- Environment and Planning E: Nature and Space
- Volume:
- 7
- Issue:
- 2
- ISSN:
- 2514-8486
- Format(s):
- Medium: X Size: p. 479-497
- Size(s):
- p. 479-497
- Sponsoring Org:
- National Science Foundation
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