Relationship of Riparian Buffer Type to Water Temperature in the Driftless Area Ecoregion of Minnesota

Abstract

We used the U.S. Fish and Wildlife Service's Stream Network Temperature Model to examine the role of riparian buffer type in mediating summer water temperatures for the reintroduction of brook trout Salvelinus fontinalis into Wells Creek, a tributary to the Mississippi River located in southeastern Minnesota. Stream temperatures measured from 23 July to 3 September 1997 were used to calibrate the model, evaluate existing temperatures, generate simulations for different shade conditions and channel morphologies, and generate simulations for ''average'' and ''warm'' summers (we define a warm summer as one that is 2.8ЊC above the 30-year mean). The simulations indicated that successional buffers (grasses and forbs) provided as much shade as wooded buffers in streams with a width less than 2.5 m. With a low width:depth ratio, the successional buffer vegetation mediated mean temperature as well as the wooded buffer when discharge was held constant. At a discharge characteristic of our study reach, the mean temperature would be about the same along a successional buffer as in a wooded buffer if the wooded vegetation also led to widening of the stream channel. However, wooded buffers had a significantly higher percentage of shade than grazed or successional buffers. In general, temperatures in an average year decreased along the wooded reaches and increased slightly along the successional and grazed buffer areas. The differences in measured weekly mean maximum temperatures may be as great as 2.5ЊC across riparian buffer types. Maximum temperatures across all riparian types would be higher during warmer than average years, even with 50% shade along the stream. Shade provided by successional and woody vegetation may serve to moderate maximum temperatures and may be sufficient for the reintroduction of brook trout if other conditions improve.

A Comparison of the Temperature Regime of Short Stream Segments under Forested and Non‐Forested Riparian Zones at Eleven Sites Across North America

“…Change in temperature over distance has only been employed in a few studies (Blann et al, 2002). The short segments (approximately 100 m) avoid the potential complication of tributary inputs yet are long enough for temperature changes to be detectable.…”

Emulation of natural disturbance (END) for riparian forest management: synthesis and recommendations

“…Moreover, retention of mature riparian forest is not required along LPS streams (Table 2) because they are typically very narrow, and understory vegetation generally will provide adequate shade (see Blann et al 2002).…”

Spring distributions and relationships with land cover and hydrogeologic strata in a karst landscape in Winona County, Minnesota, USA

“…With potentially increased surface runoff and decreased recharge to springs, cold-water spring contributions to streams could diminish with subsequent degradation to cold-water ecosystems (Sullivan et al 1987;Blann et al 2002). Forest best management practices (BMP) that minimize or prevent changes to hydrological characteristics and sediment inputs to springs and stream segments could minimize or eliminate loss of shading for these areas.…”

“…In many karst regions, springs are a critical cold-water habitat component for fish hatcheries and aquatic fish species (Anderson 1983;McClendon and Rabeni 1987;Thorn 1988;Blann et al 2002;Brabrand et al 2002;Whitledge et al 2006;Brewer et al 2007). In the midwestern US, hydrogeologic characteristics have been related to trout stream habitat quality (Poff and Allan 1995;Richards et al 1996).…”

“…In the midwestern US, hydrogeologic characteristics have been related to trout stream habitat quality (Poff and Allan 1995;Richards et al 1996). Characteristics describing geology and regional land use have also been linked to stream water quality, invertebrate production and trout population characteristics (Krueger and Waters 1983;Troelstrup and Perry 1989;Vondracek et al 2000;Blann et al 2002).…”