https://cpw.cvlcollections.org/files/original/dcd3e4d92f49dfc1c3b3053d7845094d.pdf 24ff4add4eba99048cd268127ab04d43 PDF Text Text The research in this publication was partially or fully funded by Colorado Parks and Wildlife. Dan Prenzlow, Director, Colorado Parks and Wildlife • Parks and Wildlife Commission: Marvin McDaniel, Chair • Carrie Besnette Hauser, Vice-Chair Marie Haskett, Secretary • Taishya Adams • Betsy Blecha • Charles Garcia • Dallas May • Duke Phillips, IV • Luke B. Schafer • James Jay Tutchton • Eden Vardy �Received: 26 April 2021 Revised: 5 August 2021 Accepted: 11 September 2021 DOI: 10.1002/rra.3871 RESEARCH ARTICLE Restoration of riparian vegetation on a mountain river degraded by historical mining and grazing Erin S. Cubley1 Travis L. Hardee | 3 | Eric E. Richer2 Brian P. Bledsoe | Daniel W. Baker3 | 4 | Chris G. Lamson3 | 5 Peter L. Kulchawik 1 Department of Forest and Rangeland Stewardship, Colorado State University, Fort Collins, Colorado, USA Abstract Riparian ecosystems in montane areas have been degraded by mining, streamflow 2 Aquatic Research Section, Colorado Parks and Wildlife, Fort Collins, Colorado, USA alterations, and livestock grazing. Restoration of ecological and economic functions, 3 especially in high-elevation watersheds that supply water to lower elevation urban Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, Colorado, USA 4 University of Georgia, College of Engineering, Athens, Georgia 5 and agriculture areas is of high priority. We investigated the response of riparian vegetation and bank stability following channel treatments and riparian habitat restoration along a segment of the upper Arkansas River south of Leadville, Colorado. The Balance Hydrologics, Inc., Truckee, California, USA study area has been historically degraded by heavy-metal mining and is designated a Correspondence Erin S. Cubley, Colorado State University, Department of Forest and Rangeland Stewardship, Fort Collins, CO, USA. Email: ecubley@gmail.com have contributed to channel widening and altered vegetation composition and cover. Funding information Colorado Department of Public Health and Environment; Federal Aid in Sport Fish Restoration Program, Grant/Award Number: F-161-R; Colorado Parks and Wildlife reaches with willow cover less than 16% in three reaches. Post-restoration, changes U.S. Superfund site. Additionally, trans-basin water diversions and livestock grazing We used a before-after-control impact study design in four reaches with varied contamination and grazing history to assess restoration success. Before restoration, streambanks were dominated by graminoids and total vegetation cover varied among in total vegetation cover fell short of projected goals, but willow cover was greater than 20% in all study reaches. The increase in woody cover likely contributed to reduced erosion and vegetation encroachment post-restoration. Differences in functional group cover among reaches persisted post-restoration and may be attributed to soil contamination levels and low willow seed rain and dispersal. These results highlight the importance of setting realistic restoration goals based on elevation and past land use. We recommend further remediation of fluvial tailings with low vegetation cover and continued monitoring of willow height and cover to determine if further restoration activities are needed. KEYWORDS bank stability, livestock grazing, mining, riparian vegetation, river restoration, superfund 1 | I N T RO DU CT I O N viability and resilience. Approximately 19,000 km of streams and rivers have been negatively affected by the release of fine sediment and Riparian ecosystems in mountain regions provide essential ecological heavy metals in the United States (Dabney, Clements, Williamson, & and economic functions including water quality improvement, attenu- Ranville, 2018; National Research Council, 1992). Abandoned mine ation of peak flows, and wildlife habitat (Hauer et al., 2016; tailings with toxic concentrations of heavy metals hinder plant growth Richardson et al., 2007). Montane streams and rivers have been signif- and threaten aquatic and terrestrial biotic communities (Strom, icantly altered by human activities that threaten long-term ecosystem Ramsdell, & Archuleta, 2002). Where tailings are located along rivers, 80 © 2021 John Wiley & Sons Ltd. wileyonlinelibrary.com/journal/rra River Res Applic. 2022;38:80–93. �81 CUBLEY ET AL. streambank stabilization can help to immobilize pollutants and is a were further divided into treatment and control sub-reaches with var- common practice in remediation efforts to prevent downstream eco- ied channel and floodplain restoration treatments. Project success logical degradation (Berti & Cunningham, 2000). The co-occurrence of thresholds for treatment sub-reaches and fenced reaches were identi- toxic mine tailings with additional alterations can limit ecosystem fied by stakeholders and managers prior to baseline monitoring (Stratus recovery in the absence of remedial action. Consulting Inc., 2010). Specifically, we ask the following questions: Stream ecosystems affected by mining can also be altered by changes in streamflow, depth to groundwater, and livestock grazing. (1) Has total riparian vegetation cover increased by at least 10% in Streamflow regimes and alluvial groundwater depths strongly influ- fenced and/or channel treatment areas post-restoration? ence the distribution and composition of riparian vegetation. Willows (2) How do channel treatments and fencing influence the cover and (Salix spp.) are the structurally dominant plants along many montane height of key riparian vegetation functional groups, like willows? rivers and provide streambank stabilization, moderation of water tem- (3) Do native species account for a minimum of 60% of total vegeta- peratures, and wildlife habitat (Naiman & Decamps, 1997). Riparian tion cover post-restoration? willow shrublands have been replaced by grasslands in montane val- (4) Is channel erosion or encroachment more dominant in the years leys across the Western United States due to overgrazing by livestock, following restoration in treatment and control sub-reaches? loss of beavers, changes in flow regimes, and historical mining (Brookshire, Kauffman, Lytjen, & Otting, 2002; Woods & Cooper, 2005). Livestock grazing in riparian areas can reduce vegeta- 2 METHODS | tion cover and destabilize streambanks resulting in altered channel morphologies and reduced habitat complexity (Herbst, Bogan, Roll, & 2.1 | Study area Safford, 2012). High concentrations of heavy metals can inhibit willow growth and mine tailings tend to be devoid of vegetation. Loss of wil- This work was conducted along an 11-mile reach of the upper Arkan- lows along streams can increase stream temperatures, negatively sas River near Leadville, Colorado (�2,800 m elevation), characterized affecting fish (White & Rahel, 2008), and increase bank erosion during as a wandering gravel-bed planform (USFWS, 2002). The Arkansas high flows (Vincent, Friedman, & Griffin, 2009). River hydrograph is defined by snowmelt-driven peaks in early to Rehabilitation of riparian ecosystems focuses on restoring ecolog- mid-June with low summer flows. The upper watershed has been ical processes and hydrologic regimes to promote biotic growth and mined for gold, silver, lead, and zinc for approximately 150 years persistence (Waletzko & Mitsch, 2013). Methods of restoration range (Stratus Consulting Inc., 2010). Hydraulic placer mining in the valley from hydrologic recovery and reconnection (Wilcox, Sweat, Carlson, & introduced coarse sediments resulting in channel aggradation and Kowalski, 2006), topographic alteration (Moreno-Mateos, Power, widening. California Gulch, a tributary of the Arkansas River, and Comin, & Yockteng, 2012), and contaminated soil removal or amend- much of the downstream watershed was designated as a ment (Wong, 2003). Treatment actions addressing channel and flood- U.S. Superfund site in 1983. Fluvial deposition of mine tailings follow- plain geomorphology are commonly used to restore overbank ing large flood events resulted in degraded soils with low pH and high flooding, groundwater levels, and promote native vegetation growth. concentrations of heavy metals. Fluvial mine waste deposits in the The construction of grazing exclosures commonly accompanies resto- 500-year Arkansas River floodplain were toxic for riparian vegetation ration (Kaufmann & Krueger, 1984) to reduce stress on vegetation and detrimental for wildlife and livestock (Industrial Economics, 2006). and channel banks. However, disturbance from restoration activities Before restoration, approximately 170 fluvial mine tailing deposits can increase non-native plant cover, and efforts to limit their estab- occurred along an 18-mile reach of the river south of Leadville lishment may be needed (Suding, Gross, & Houseman, 2004). (USFWS, 2002). Flow augmentation from trans-basin diversions has Restoration activities may have initial negative impacts and low altered the river's natural flow regime resulting in increased erosion, success rates (Roni et al., 2002), highlighting the need for long-term channel widening, and loss of pool habitat for native fish. Before min- monitoring. Relatively few restoration projects quantitatively monitor ing and flow augmentation, the river was estimated to be half of its sites beyond a few years (Bernhardt & Palmer, 2011) and the time present width (USFWS, 2002). Livestock grazing was ongoing in the requirements for success are poorly understood (Moreno-Mateos, Meli, upper Arkansas valley for nearly 200 years with settlers operating cat- Vara-Rodriguez, & Aronson, 2015). The analysis of restoration tle and sheep ranches as early as the 1830s (Klima & Scherer, 2000). approaches along montane streams impacted by mine activities is criti- Restoration objectives in the study area downstream from Cali- cal in protecting water resources for downstream users, particularly in fornia Gulch focused on both channel and floodplain treatments to high elevation watersheds that supply water to lower elevation urban restore natural river processes to address erosion, river channel mor- and agricultural areas. To address habitat restoration effectiveness phology, and degraded in-stream and floodplain habitat for fish and along a degraded montane river, we implemented a long-term monitor- other wildlife (Table A1). Improvements to the floodplain included ing program following restoration treatment and fencing on the upper livestock exclusion fencing, vegetation planting or seeding, and graz- Arkansas River in Colorado. We assessed vegetation functional group ing management plans. Vegetation plantings and seeding occurred cover and the location of the perennial streambank in four main study outside of sample plots and due to poor quality stock, plantings were reaches with different grazing histories and fencing. Study reaches largely unsuccessful. Fluvial mine waste deposits in the Ranch and �82 CUBLEY ET AL. Hayden reaches were identified and treated by the Environmental by livestock. It is the only reach that was not subject to bank, Protection Agency (EPA) in 2008–2009 with additional treatments in instream, seeding, and planting activities and has a more constrained 2012–2014 (USEPA, 2017). Colorado Parks and Wildlife (CPW) valley form than the three upstream reaches. treated one fluvial deposit in the Reddy reach in 2013 during stream restoration project implementation. Fluvial mine waste deposits were treated with lime or lime and organic amendments, deep tilling, and 2.2 | Vegetation sampling seeding (EPA, 2017). The total budget for stream restoration within the 11-mile reach was approximately $8,800,000, including design, We used both photographic documentation and visual estimation to construction, and monitoring. We analyzed riparian vegetation and characterize riparian vegetation cover and willow height. A before- streambank stability in four main study reaches with different grazing after-control impact (BACI) design was used with baseline data col- histories that were further divided into treatment and control sub- lected in 2012 and post-restoration in 2015, 2017, and 2019. Each of reaches (Figure 1, Table A1). The Ranch is the upstream-most reach the four reaches was split into a varying number of sub-reaches which closest to California Gulch, followed by the Reddy, Hayden, and Kobe were approximately 12 channel widths in length. Vegetation was sam- reaches. pled in ten, 3 m2 plots uniformly spaced within each sub-reach Bank and in-stream treatments occurred in the Ranch, Reddy, and (Kulchawik & Bledsoe, 2013). Plots were oriented with one edge par- Hayden sub-reaches between 2012 and 2014 and some revegetation allel to the water and no more than 1 m spacing between the plot and work (riparian seeding, willow planting) occurred in the spring of 2015 streambank. Several plots were setback from the bank to accommo- in the Hayden reach. Riparian areas in the Reddy reach were fenced date the construction of boulder habitat structures. In late August of in 2011 followed by the Ranch reach in 2012. The Hayden reach has each monitoring year, vegetation surveys were conducted to capture not been grazed by livestock since 1998 and riparian areas are not conditions under similar streamflow and vegetation productivity in fenced. The Kobe reach is managed by the Bureau of Land Manage- the growing season. ment (BLM) and is partially fenced but has not been recently grazed Vegetation was grouped based on root stability structure (Table A2, Winward, 2000): sagebrush (Artemisia spp.), cinquefoil (Dasiphora spp.), horsetail (Equisetum spp.), iris (Iris spp.), currant (Ribes spp.), willow (Salix spp.), and graminoids (grasses, sedges, and rushes). We visually estimated the cover of vegetation functional groups, bare ground, and if erosion had occurred, water in each plot. We used plot photos from each year to categorize willows into five growth-stage bins: no willows, prostrate (0–0.3 m), low (0.3–1.0 m), medium (1.0– 2.0 m), and tall (>2.0 m). Photographs were taken from a designated plot corner each sample year. Native and non-native species cover (USDA, 2019) in Hayden reach plots was recorded in 2019. Throughout the study period, several plots located on outside bends were lost to bank erosion and plots were replaced in 2019 on the same geomorphic surface. Bank erosion and vegetation encroachment were assessed by comparing the location of the greenline through monitoring years. The greenline is defined as the first lineal grouping of perennial vegetation near the water's edge and typically occurs at or below the bankfull stage (Winward, 2000). In 2012, the location and elevation of the greenline were recorded at each sub-reach using a total station. Later monitoring used survey-grade real-time kinematic (RTK) GPS using NAD 1983 U.S. State Plane Central and NAVD 1988 coordinate systems (Richer, Gates, Kondratieff, & Herdrich, 2019). Polygons were developed from the survey data using ESRI ArcMap software to illustrate the change in greenline location between survey years and the total area of erosion versus encroachment. Net change was calculated to assess overall bank mobility at each sub-reach. We compared the areal change in the greenline between channel margins classified as convex (inside of meanders), concave (outside of meander), and straight. F I G U R E 1 Study reaches along the upper Arkansas River south of Leadville, Colorado Stream discharge was analyzed to characterize hydrology during the study period. Flood frequency analysis was used to estimate the �83 CUBLEY ET AL. recurrence interval of peak flows at the United States Geological Sur- effects. Plots were removed from the analysis if significant erosion vey (USGS) stream flow gauge # 7083710 below Empire Gulch. We had occurred since baseline, and water comprised more than 5% of also compared mean daily discharge (1992–2019) to the annual the plot. Willow height difference between years, treatments and con- hydrograph for each study year (Figure A1). The highest peak flow fol- trols, and reaches was analyzed using a repeated measure ordinal lowing restoration occurred in 2019 at 79.3 m3/s with an estimated regression with the clmm function in the ordinal package recurrence interval (RI) of 38-years. Lower peak flows were observed (Christensen, 2019). We separately analyzed vegetation functional 3 in 2015 and 2017 at 43.9 and 29.5 m /s, respectively (5.5- and group cover between years in plots located on fluvial mine tailings 2.5-year RI). In non-sampling years, peak flows were lower, with using one-way analysis of variance (ANOVA) due to the small sample recurrence intervals less than 5 years. size (n = 16). Erosion and encroachment between concave, convex, and straight channel segments were also analyzed using ANOVA. Kruskal Wallace tests were used if model residuals did not meet 2.3 | Statistical analyses assumptions and transformations did not improve residuals. All statistical analyses were performed in R, program version 4.0.3 We assessed changes in riparian vegetation functional group cover (R Development Core Team, 2020). and bank stability between years, treatment and control sub-reaches, and the four main study reaches with different grazing histories using repeated measure mixed-effects models with the lmerTest package in 3 | RE SU LT S R (Kuznetsova, Brockhoff, & Christensen, 2017). Vegetation group covers were averaged within each sub-reach since model residuals Streambank plots along the upper Arkansas River were dominated by with individual plot as the sample unit violated linearity and hetero- graminoids followed by willows and then forbs during the study skedasticity assumptions. Sub-reach was nested within study reach as period. Total vegetation cover was similar between control and treat- a random effect and treatment type, year, and reach were fixed ment sub-reaches from baseline to 2019 (Figure 2; Table 1; p = .21), F I G U R E 2 Percent total vegetation (top) and willow (bottom) cover between study reaches and years. Reach and year interacted to predict total vegetation cover while reach, year, and treatment predicted percent willow cover. Total cover differed across reaches before restoration in 2012 but was similar between reaches in 2019 �84 CUBLEY ET AL. T A B L E 1 Mixed model results for vegetation functional group cover (%) between all monitoring years, study reaches, and treatment and control sub-reaches. For significant main effects and interactions (in bold), Tukey adjusted p values for significant pairwise comparisons of estimated least square means are shown Type III tests of fixed effects Total vegetation cover Tukey pairwise comparisons (differences of least squares means) Effect DF F p Effect Estimate DF Treatment 1 1.68 .21 2012 ranch: 2012 Reddy 13.18 34.8 Adj. p .003 Year 3 2.04 .12 2012 Reddy: 2012 Kobe 12.08 31.9 .004 Reach 3 5.98 .005 2012 Hayden: 2012 ranch 18.04 36.5 <.001 Year � reach 9 3.49 .002 2012 Hayden: 2012 Kobe 16.93 28.2 <.001 2012 Hayden: 2015 Hayden 4.94 51.0 .007 2012 Hayden: 2019 Hayden 5.43 51.0 .003 2012 Hayden: 2017 Hayden 4.18 51.0 .022 2012 Kobe: 2015 Kobe 5.89 51.0 .03 2012 ranch: 2017 ranch 8.20 51.0 .02 2012 ranch: 2019 ranch 9.64 51.0 .005 2012 ranch: 2019 ranch 9.64 51.0 .005 2015 Hayden: 2015 ranch 9.10 36.5 .03 2017 Reddy: 2019 Reddy 6.15 51.0 .005 2017 ranch: 2017 Reddy 12.27 31.9 .004 2017 Hayden: 2017 ranch 9.08 36.5 .03 2017 Hayden: 2017 Kobe 13.87 28.2 .002 Willow cover Effect DF Treatment 1 F p Effect 6.72 .019 Treatment: Control Estimate DF Adj. p 10.51 17 .02 Year 3 22.14 <.001 2012:2015 6.14 51 <.0001 Reach 3 13.39 <.001 2012:2017 10.90 51 <.0001 2012:2019 7.82 51 <.0001 2015:2017 4.76 51 .001 2017:2019 3.08 51 .03 Reddy: Hayden 19.26 17 <.0001 Kobe: Hayden 26.70 17 <.0001 Graminoid cover Effect DF DF p Treatment 1 F 3.05 p .100 2012:2015 Effect 7.88 51 <.0001 Year 3 30.38 <.001 2012:2017 12.52 51 <.0001 Reach 3 5.29 .009 2012:2019 15.83 51 <.0001 2015:2017 4.64 51 .01 2015:2019 Estimate 7.94 51 <.0001 Reddy: Hayden 12.40 17 .001 Hayden: Kobe 12.11 17 .02 Estimate DF p Forb cover Effect DF Treatment 1 Year 3 Reach 3 F p Effect .98 2012:2017 0.97 51 <.001 21.36 <.001 2012:2019 1.46 51 <.001 10.48 <.001 2015:2017 0.87 51 <.001 2015:2019 1.36 51 <.001 0.005 �85 CUBLEY ET AL. TABLE 1 (Continued) Forb cover Effect DF F p Effect Estimate DF 2017:2019 0.49 51 p .03 Reddy: Hayden 1.22 17 <.001 Reddy: Kobe 1.02 17 .005 Reddy: Ranch 0.91 17 .014 F I G U R E 3 Photo documentation of the change in riparian vegetation cover in the Reddy reach in treatment (top) and control (bottom) sub-reach plots [Color figure can be viewed at wileyonlinelibrary.com] but the effect of study year on total cover varied by reach (Table 1; (χ2 = 9.93, p = .02) and differed across all years except between p = .001). Baseline total vegetation cover in 2012 was 18% lower 2015 and 2017. From 2012 to 2019, the percentage of willows classi- in the Ranch reach and 14% lower in the Kobe reach than the fied as medium or tall increased across all reaches while prostrate and Hayden reach while cover was similar between the Reddy and low willows decreased (Figure 3). Overall, the Hayden reach had more Hayden and between the Ranch and Kobe reaches (Table 1). Total tall willows than Reddy and Kobe, where a higher percentage of wil- vegetation cover became similar across all study reaches post- lows were in the prostrate and low height categories (Figure 4, restoration in 2019. Total cover increased 10% in the Ranch reach estimate = 1.75, p = .02). and 5% in the Kobe reach from 2012 (baseline) to 2019 (post-resto- The cover of graminoids was predicted by reach and year ration). In the Hayden reach, total cover decreased 6% from 2012 (Table 1). Graminoid cover decreased across the study period with sig- to 2019 (p = .003) but varied throughout the study period with a nificant differences between all years (Figure 5). Graminoid cover was 5% increase from 2015 to 2017 (p < .02). Similarly, total cover 11% higher at Reddy and 7% higher at Kobe than Hayden (Table 1; decreased by 6% from 2017 to 2019 in the Reddy reach p < .001). Forb cover was similar in 2015 compared to 2012 but (Table 1; p = .005). increased from 2012 baseline to 2017 and 2019 (Figure 5; p < .001). Variance in willow cover was explained by year, treatment, and Forb cover was higher at Reddy than Hayden (p < .001), Kobe reach (Table 1). From baseline in 2012–2019 willow cover increased (p = .006), and the Ranch reaches (Table 1; p = .01). Graminoid and 8% (Figures 2 and 3). Willow cover was similar among the Ranch, forb cover was similar between control and treatment sub-reaches. Reddy, and Kobe reaches, but they all had significantly less willow Within the study area, 16 of the 170 plots were located on fluvial cover than the Hayden reach (Table 1; p < .001). Treatment sub- mine tailings. Vegetation cover on tailings ranged 0–100% in 2012 reaches had higher willow cover in the 2012 baseline which continued and 12–100% in 2019 and was dominated by graminoids and forbs. through the study period (Table 1). Variance in willow height was However, vegetation cover on tailings was similar between study explained by year (Ordinal Regression χ2 = 53.87, p < .001) and reach years (Figure 6, ANOVA p = .37). �86 CUBLEY ET AL. F I G U R E 4 Percentage of plots in five willow height classes between study reaches in 2012 (top) and 2019 (bottom) Non-native cover averaged 16% in the Hayden reach in 2019. Non- 4 | DI SCU SSION native species identified in order of abundance were yarrow (Achillea millefolium), Kentucky bluegrass (Poa pratensis), common dandelion (Taraxicum This study assessed changes in riparian vegetation cover and bank sta- officinale), white clover (Trifolium repens), wild chamomile (Tripleurospermum bility in response to channel restoration and grazing exclosures in four perforatum), and European stickseed (Lappula squarrosa). study reaches along the upper Arkansas River. Before restoration, his- Bank erosion area was higher between the 2012 baseline survey torical mining activities and related soil contamination, livestock graz- and 2015 than it was during the 2015–2017 and 2015–2019 periods ing, and flow alteration and channel configuration altered riparian (Figure 7; F = 7.09, p = .003). Erosion area was also higher along con- vegetation composition and cover. Total vegetation cover was lower cave river segments than convex segments between 2012 and 2015 in recently grazed reaches before restoration but increased post- (Kruskal Wallace p = .02) and was significantly lower between 2017 restoration becoming similar to the other study reaches. Although and 2019 than 2012–2015 in concave segments (p = .003). Year and total vegetation cover converged across reaches post-restoration, reach interacted to predict channel encroachment area (F = 5.45, functional group cover differences are likely related to disturbance p = .005) and net change in area (F = 6.45, p < .005). Encroachment history and legacy effects. For example, willow height and cover in area was higher in Hayden than the Kobe (estimate = 335.76, reaches grazed before restoration are still lower than reaches where p = .003), Ranch (estimate = 365.68, p < .001), and Reddy livestock grazing has been absent for more than 20 years. Our results (estimate = 344.87, p < .001) reaches from 2017 to 2019 (Figure 7). indicate a significant increase in riparian willow cover and height In the Hayden reach, encroachment was higher between 2017 and across all reaches, suggesting increased riparian habitat structural 2019 than 2015–2017 (estimate = 337.34, p < .001) and 2012– complexity following restoration. The increase in woody vegetation 307.18, p < .001). Area of encroachment was cover will help to stabilize streambanks and reduce the mobilization of 2015 (estimate = higher in convex segments compared to concave segments (Kruskal fluvial mine wastes downstream. Wallace p = .02). Net change was highest in the Hayden reach from We found a 10% increase in total vegetation cover in the Ranch 2017 to 2019 and in the Reddy reach between 2012 and 2015 reach and a 5% increase in the Kobe reach but, the average total veg- (Figure 7; estimate = 135.31, p = .05). etation cover change across all reaches was negligible. The project �CUBLEY ET AL. F I G U R E 5 Percent cover of graminoids (top) and forbs (bottom) between study reaches and years on the upper Arkansas River. Graminoid cover decreased across the study period and was generally higher in the Reddy reach. Forb cover was highest in the Reddy reach and increased from 2012 to 2017 and 2019 F I G U R E 6 Photographic documentation of riparian vegetation cover on fluvial tailing plots in the Ranch reach from 2012 (before) to 2019 (after restoration). Total vegetation cover was similar on fluvial tailings from 2012 to 2019 [Color figure can be viewed at wileyonlinelibrary.com] 87 �88 CUBLEY ET AL. F I G U R E 7 Area of erosion (top), encroachment (middle), and net change (bottom) at subreaches across three study intervals (2012–2015, 2015– 2017, 2017–2019) goal of a 10% vegetation cover increase was established before quan- among reaches before restoration may be partly driven by differences in tifying baseline conditions. The perception of low vegetation cover grazing. Total cover was highest in the Hayden reach where livestock may have been driven by short willows plus the prevalence of barren grazing has been absent for over 20 years compared to the Ranch and fluvial mine tailings across the study area. Vegetation goals defined Reddy reaches where riparian grazing was eliminated by fencing prior to for each reach would have been more useful since baseline surveys in baseline monitoring in 2011 and 2012. Willow seed rain can increase 2012 indicated that total vegetation cover was greater than 90% in slowly following long periods of grazing (Kaczynski, Gage, & the Hayden and Reddy reaches but was 78% and 83% at the Ranch Cooper, 2018) and contribute to lagged willow recovery. Willow cover and Kobe reaches, respectively. A previous 1987 study estimated and height were restored to reference levels within exclosures after total vegetation cover to be 77% in the two upper reaches (Ranch and 5 years along a montane stream in northern Colorado (Holland, Reddy) and 65% in the Hayden reach (Keammerer, 1987). Although Leininger, & Trlica, 2005). Conversely, another stream in Utah with high our study used a different sampling design, total vegetation cover is grazing intensity and low woody recruitment saw little change in willow estimated to have increased approximately 12% in the Ranch and abundance 4 years post-exclosure (Hough-Snee, Roper, Wheaton, Reddy reaches and 30% in the Hayden reach over the past 32 years. Budy, & Lokteff, 2013). In California, willow height had not yet recov- Differences in valley form between study reaches may influence flood ered after 25 years of rest post-grazing (Nusslé, Matthews, & frequency, groundwater, and soils that drive variation in riparian vege- Carlson, 2017). We found that willow cover was not significantly higher tation cover. For example, the downstream Kobe reach is more con- than baseline until 2017, indicating that several years were needed for strained than the three upstream reaches which may affect hydrologic woody plant recovery and establishment. Willow density and height in conditions and vegetation. restored riparian sites in the San Juan Mountains of Colorado were still Along the upper Arkansas River, the long-term effects of channel treatments, grazing exclosures, fluvial mine waste remediation, and lower than reference densities 12–15 years after restoration (Cooper, Kaczynski, Sueltenfuss, Gaucherand, & Hazen, 2017). interannual climatic variability on riparian vegetation composition and Differences in functional vegetation group cover across reaches cover are difficult to uncouple. Variation in total vegetation cover may also be attributed to variation in heavy-metal contamination �89 CUBLEY ET AL. (Wahsha et al., 2012). Impacts to biological resources were hypothe- channel narrowing with imported fill occurred. Planting and seeding sized to decrease moving downstream. Still, a lower channel gradient activities did not occur in long-term monitoring plots, but these activi- and bankfull capacity in the Hayden reach resulted in more overbank ties may be affecting vegetation cover captured by the greenline anal- flow and historic mine waste deposition (USFWS, 2002). Although ysis and explain the minimal change in total cover captured in insignificant, increases in total vegetation cover from 2012 to 2019 vegetation plots. Restoration of the channel and floodplain also varied on fluvial tailings were attributed to graminoids and forbs that were between sub-reaches and not all reaches received similar restoration seeded during remediation and restoration efforts. Herbs and treatments. Furthermore, more time may be needed for channel re- graminoids provide some level of streambank stabilization, increasing adjustment in treatment areas, particularly with slow vegetation surface roughness on floodplains and promoting sediment deposition, responses (Cooper et al., 2017). channel contraction, and plant succession (Simon & Collison, 2002). Willow cover and height may be slower to recover in areas with more heavy metal contamination, particularly in areas with a fluctuating 5 | CONC LU SIONS water table (Bourret, Brummer, Leininger, & Heil, 2005). Reestablishment of willows on fluvial tailings may require planting, espe- Although restoration along the upper Arkansas River has not resulted cially if natural recruitment from upstream or adjacent propagule sup- in a 10% increase in total vegetation cover across all fenced and chan- plies is low. nel treatment reaches, willow height and cover increased while The functional response of riparian vegetation is largely driven by graminoid cover decreased. Additionally, greenline encroachment sug- temporal variations in hydrological conditions (Januschke, Jähnig, gests an increase in reach-scale coverage of riparian vegetation. Spe- Lorenz, & Hering, 2014). Large magnitude spring flows on the Arkan- cific goals related to willow cover and height rather than total sas River in 2019 flooded riparian plots and deposited sediment that vegetation cover would have been more appropriate to address the may have contributed to the continuation of low cover on tailings and main project goal of improving fish habitat through stream shading minimal changes in total vegetation cover post-restoration. However, and terrestrial inputs to the aquatic food web (Baxter, Fausch, & years with high discharges that flood and deposit sediment stimulate Saunders, 2005). Recently grazed reaches still had lower willow cover plant colonization by importing seeds, nutrients, and mineral soils and height in 2019 and this legacy may be inhibiting willow growth (Asaeda, Gomes, Sakamoto, & Rashid, 2011; Richards, Brasington, & and seed dispersal. Natural recovery timelines could exceed 15 years Hughes, 2002). Interannual climatic variations that influence discharge (Cooper et al., 2017), particularly since the growing season is short and stream stage may also drive groundwater recharge if water is sup- (�75 days). Continued monitoring of these areas will be necessary to plied by lateral flow from the river (Gribovszki, Szilágyi, & determine if willow seed rain is sufficient and if additional willow Kalicz, 2010). Bankfull cross-sectional area decreased from 2013 to planting is needed. 2015 at many sub-reaches in the study area (Richer, Gates, Herdrich, & The inclusion of reference sites outside of the disturbed study Kondratieff, 2017), indicating increased channel-floodplain connectiv- area may have better informed restoration goals for riparian func- ity and shallower alluvial groundwater levels that may be contributing tional group cover and the proportion of native versus non-native to increased willow growth. species. Although non-native species can be persistent following res- Discharge patterns also control rates of erosion, sediment trans- toration activities, we found non-native cover to be below 30% and port, and bed material deposition that influence channel form (Ward, consist mainly naturalized species, like yarrow (A. millefolium). The Tockner, Arscott, & Claret, 2002). Annual average streamflow and study was also limited by the placement of control sub-reaches within snowmelt flows can significantly influence the balance between ero- grazing exclosures and their proximity to treatment sub-reaches. It is sion and encroachment and temporal variation in discharge results in possible that this affected vegetation response at controls and diverse floodplain habitats that frequently shift (Robinson, Tockner, & masked differences. Ward, 2002). Floodplain areal increases following restoration along a Multiple ecosystem alterations can influence riparian ecosystem montane river in Germany was attributed to lower discharges in years restoration and practitioners are challenged to anticipate the biotic post-restoration that promoted succession processes (Januschke and abiotic processes that may affect the timescale and trajectory of a et al., 2014). By contrast, we found that erosion was highest in the site (Bilyeu, Cooper, & Hobbs, 2008). Our results highlight how multi- first few years post-restoration before encroachment became domi- ple ecosystem stressors challenge the restoration of riparian vegeta- nant. The elevated 2019 peak flow coupled with increased woody tion and how growing season length and inherent climatic variability vegetation cover post-restoration may have contributed to increased that drives streamflow can make restoration improvements difficult to sediment deposition and geomorphic recovery (Corenblit, Steiger, detect. Additionally, stream restoration is expensive, and there is lim- Gurnell, Tabacchi, & Roques, 2009), particularly in the lower gradient ited evidence that restoration activities are effective due to a general Hayden reach. lack of monitoring. However, in the 5 years post-restoration on the We found that erosion and encroachment were similar between upper Arkansas River, the increase in willow cover and height and net treatment and control sub-reaches. The increase in encroachment vegetation encroachment suggests a shift toward dynamic equilibrium over the study period suggests that overall vegetation cover has for the stream channel, structurally complex riparian vegetation, and increased on the floodplain, particularly in the Hayden reach, where increased habitat heterogeneity for terrestrial and aquatic biota. �90 CUBLEY ET AL. ACKNOWLEDGMENTS This work was sponsored by Colorado Parks and Wildlife (CPW), and funding was provided in part by the Federal Aid in Sport Fish Restoration Program (Project F-161-R, Stream Habitat Investigations and Assistance) and Natural Resource Damage Assessment provisions of the Comprehensive Environmental Response, Compensation, and Liability Act via the Colorado Department of Public Health and Environment (CDPHE). Kyle Hardee, Brye Windell, Renee Vandermause, Johannes Beeby, Rod Lammers, Danny White, and others assisted in the field. The authors declare no conflict of interest. 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T A B L E A 1 Vegetation monitoring sub-reaches used for evaluation of the upper Arkansas River habitat restoration project including reach and sub-reach identifier, delineation as treatment or control, type of restoration treatments, and function of treatments Reach Sub-reach Type Treatments Functions Ranch UA 2–2 Treatment Fluvial mine tailings, boulder grade control, boulder vane, boulder cluster, pool development, sod mat, riparian seeding, willow transplant Bank stabilization, sediment transport, fish habitat, revegetation Ranch UA 2–4 Treatment Fluvial mine tailings, boulder vane, pool development, riparian seeding Bank stabilization, sediment transport, fish habitat, revegetation Reddy UA 2–5 Control None - Reddy UA 2–6 Treatment Cobble toe, wood toe, log/boulder vanes, point-bar and pool development, sod mat Bank stabilization, sediment transport, fish habitat Reddy UA 2–7 Treatment Point-bar and pool development Sediment transport, fish habitat Reddy UA 2-8R Treatment Wood toe, boulder cluster, log vane, point-bar and pool development, sod mat Bank stabilization, sediment transport, fish habitat Reddy UA 2-8 L Control None - Hayden UA 3–1 Treatment Channel narrowing, boulder toe, cobble toe, boulder cluster, point-bar and pool development, sod mat, riparian seeding, willow transplants Floodplain connectivity, bank stabilization, sediment transport, fish habitat, revegetation Hayden UA 3–2 Treatment Channel narrowing, wood toe, boulder cluster, pointbar and pool development, sod mat, riparian seeding, willow stakes, willow transplants Floodplain connectivity, bank stabilization, sediment transport, fish habitat, revegetation Hayden UA 3–3 Treatment Wood toe, log vane, point-bar and pool development, sod mat and willow transplants, riparian seeding Bank stabilization, sediment transport, fish habitat, revegetation Hayden UA 3–4 Treatment Channel narrowing, boulder vane, point-bar and pool development, sod-mat and willow transplants Floodplain connectivity, bank stabilization, sediment transport, fish habitat Hayden UA 3–5 Treatment Cobble toe, log vane, point-bar and pool development, sod-mat and willow transplants Bank stabilization, sediment transport, fish habitat Hayden UA 3–6 Control None - Hayden UA 3–7 Treatment Fluvial mine tailings, boulder cluster, log vane, pointbar and pool development, sod-mat and willow transplants Bank stabilization, sediment transport, fish habitat, revegetation Kobe UA 4–1 Control None - Kobe UA 4–2 Control None - Kobe UA 4–3 Control None - TABLE A2 Vegetation functional groups based on stability rating Group symbol Genus Description Functional group stability number AR = sagebrush Artemisia All Artemisia spp. 5 DA = cinquefoil Dasiphora All Dasiphora fruticosa 5 EQ = horsetail Equisetum All equisetum spp. 7 FB = forbs - Forbs 5 GR = grasses, sedges, rushes - Graminoids 7 IR = iris Iris All Iris missouriensis 7 RI = current Ribes All Ribes laxiflorum 6 SA = willow Salix Various willows 8 X = bare - Bare ground 1 �CUBLEY ET AL. 93 F I G U R E A 1 Daily discharge in each of the study years (2012, 2015, 2017, 2019) and mean daily discharge (1992–2019) during the growing season on the upper Arkansas River (USGS # 7083710). Peak flows were highest in 2019 and characterized by two peaks, one in June and one in July � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Journal Articles Description An account of the resource CPW peer-reviewed journal publications Text A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Restoration of riparian vegetation on a mountain river degraded by historical mining and grazing Description An account of the resource Riparian ecosystems in montane areas have been degraded by mining, streamflow alterations, and livestock grazing. Restoration of ecological and economic functions, especially in high-elevation watersheds that supply water to lower elevation urban and agriculture areas is of high priority. We investigated the response of riparian vegetation and bank stability following channel treatments and riparian habitat restoration along a segment of the upper Arkansas River south of Leadville, Colorado. The study area has been historically degraded by heavy-metal mining and is designated a U.S. Superfund site. Additionally, trans-basin water diversions and livestock grazing have contributed to channel widening and altered vegetation composition and cover. We used a before-after-control impact study design in four reaches with varied contamination and grazing history to assess restoration success. Before restoration, streambanks were dominated by graminoids and total vegetation cover varied among reaches with willow cover less than 16% in three reaches. Post-restoration, changes in total vegetation cover fell short of projected goals, but willow cover was greater than 20% in all study reaches. The increase in woody cover likely contributed to reduced erosion and vegetation encroachment post-restoration. Differences in functional group cover among reaches persisted post-restoration and may be attributed to soil contamination levels and low willow seed rain and dispersal. These results highlight the importance of setting realistic restoration goals based on elevation and past land use. We recommend further remediation of fluvial tailings with low vegetation cover and continued monitoring of willow height and cover to determine if further restoration activities are needed. Bibliographic Citation A bibliographic reference for the resource. Recommended practice is to include sufficient bibliographic detail to identify the resource as unambiguously as possible. <a href="https://doi.org/10.1002/rra.3871" target="_blank" rel="noreferrer noopener">https://doi.org/10.1002/rra.3871</a> Creator An entity primarily responsible for making the resource Cubley, Erin S. Richer, Eric E. Baker, Daniel W. Lamson, Chris G. Hardee, Travis L. Bledsoe, Brian P. Kulchawik, Peter L. Subject The topic of the resource Bank stability Livestock grazing Mining Riparian vegetation River restoration Superfund Extent The size or duration of the resource. 14 pages Date Created Date of creation of the resource. 2021-10-06 Rights Information about rights held in and over the resource <a href="http://rightsstatements.org/vocab/InC-NC/1.0/" target="_blank" rel="noreferrer noopener">In Copyright - Non-Commercial Use Permitted</a> Format The file format, physical medium, or dimensions of the resource application/pdf Language A language of the resource English Type The nature or genre of the resource Article