Riparian Management Research Articles

Effects of land cover, topography, and soil on stream water quality at multiple spatial and seasonal scales in a German lowland catchment

The influence of catchment characteristics on water quality varies with space and time. Understanding the key factors influencing water quality is needed for effective land use and riparian management to protect river health. To this end, we quantified effects on stream water quality in summer and winter between 1992 and 2019 at multiple spatial scales in the upper Stör catchment, Germany. We applied multivariate statistical analyses on three scales: the catchment, riparian, and reach scale. Our results indicated that poorer water quality mostly occurred in winter and in steeper arable and pasture areas and in wetlands. Water quality was strongly affected by soil properties, land use composition (the areal shares of arable or pasture land respectively with slopes >2%, forest, and urban) and configuration. The spatial variation of the overall water quality was better explained at the larger scales (riparian and catchment) and in summer (73–78%). The most important variables differed among scales and for the different water quality variables. Forest and complex landscape patterns showed more negative correlations with degraded water quality at the reach scale when compared to larger scales. At larger scales, besides permeable and organic soils, steeper arable lands were most significant for nitrate-nitrogen (NO3-N) and steeper pasture areas for phosphate-phosphorus (PO4-P) pollution. The results of this study provide valuable insights for guiding sustainable and spatially specific land-water management of river catchments at different scales to improve stream water quality.

How Cattle and Wild Ungulate Use of Riparian Areas Effects Measures of Streambank Disturbance

Improper management of cattle near streams can negatively affect the processes that support stream and riparian ecosystems. To judge the success of riparian management strategies, public land management agencies often evaluate two metrics of livestock disturbance, stubble height and streambank alteration. There are concerns associated with how well these disturbance metrics reflect livestock use and incorporate additional effects due to wild ungulates. We sought to address these questions in 39 riparian areas by using time-lapse cameras to estimate ungulate use and then measuring near stream ungulate disturbance in these same reaches. We found daytime measures of livestock use were related to stubble height and streambank alteration. Explaining the variation in the relationship between stubble height and livestock use was improved by incorporating covariates, whereas covariates did little to improve our understanding of streambank alteration. This suggests greater flexibility in how different stream reaches are managed when stubble height is the guideline. As streambank alteration was explained solely by ungulate use, the simplest way to reduce disturbance was to reduce use. In most stream reaches, the additive presence of wild ungulates was minimal but sufficient to be included in the best models describing the effects of ungulate disturbance. On most days, no cattle were seen in the evaluated riparian reaches. Although large groups of cattle (> 20 individuals) were occasionally observed within riparian areas, they generally occurred in small groups of one to four individuals. Across the riparian reaches we evaluated, cattle presence and density were generally low enough that metrics of livestock disturbance suggested little risk to stream conditions important to aquatic biota. However, there were some riparian areas where cattle stayed too long or occurred in large enough numbers that their use along the streambanks could negatively affect stream habitat conditions.

Forest riparian buffers reduce timber harvesting effects on stream temperature, but additional climate adaptation strategies are likely needed under future conditions.

Stream water temperature imposes metabolic constraints on the health of cold-water fish like salmonids. Timber harvesting can reduce stream shading leading to higher water temperatures, while also altering stream hydrology. In the Pacific Northwest, riparian buffer requirements are designed to mitigate these impacts; however, anticipated future changes in air temperature and precipitation could reduce the efficacy of these practices in protecting aquatic ecosystems. Using a combined modeling approach (Soil and Water Assessment Tool (SWAT), Shade, and QUAL2K), this study examines the effectiveness of riparian buffers in reducing impacts of timber harvest on stream water temperature in Lookout Creek, Oregon across a range of potential future climates. Simulations assess changes in riparian management alone, climate alone, and combined effects. Results suggest that maximum stream water temperatures during thermal stress events are projected to increase by 3.3-7.4 °C due to hydroclimatic change alone by the end of this century. Riparian management is effective in reducing stream temperature increases from timber harvesting alone but cannot fully counteract the additional effects of a warming climate. Overall, our findings suggest that the protection of sensitive aquatic species will likely require additional adaptation strategies, such as the protection or provisioning of cool water refugia, to enhance survival during maximum thermal stress events.

Decadal‐scale changes in suspended wood after riparian recruitment in managed stands in headwater streams of coastal British Columbia, Canada

AbstractLarge wood (LW) affects several ecological and hydrogeomorphic processes in streams. The main source of LW is riparian trees falling inside channels. However, in confined valley floors, falling trees are more likely to be suspended above the channel. Eventually, these suspended trees will decompose and break to finally fall into the channel to better provide functions for streams. We evaluated changes in wood decay, length, diameter, and suspended status (suspended or non‐suspended) 17 years post‐harvest and nine years after the first sampling occurred in 2006 in 12 headwater streams of coastal British Columbia, Canada. We also evaluated whether changes differed among riparian management treatments (no‐harvest buffers of 10 and 30 m in width, thinning, and unharvested reference sites), and identified the factors affecting wood changes and suspended status. Wood pieces advanced in decay, became shorter, and 34% of them (n = 108) changed status from suspended to non‐suspended. Non‐suspended wood pieces were more decayed and shorter than suspended wood. Suspended wood was longer, thicker, less decayed, and represented 46.5% (n = 147) of the wood sampled in 2006. Our findings revealed limited influences of riparian management on many aspects of wood changes considered in this study. Changes in wood characteristics were more likely for pieces that were smaller in diameter, longer, and suspended closer to the water. The transition from suspended to non‐suspended LW can be a long‐term process that can increase wood residence time and reduce LW in‐stream functions particularly in confined stream valleys. The suspended stage is also an important mechanism underlying time lags in stream ecosystem responses to riparian tree fall. © 2020 John Wiley & Sons, Ltd.

Quantifying effects of forest harvesting on sources of suspended sediment to an Oregon Coast Range headwater stream

Elevated fine sediment transport to streams can negatively affect aquatic ecosystem health, downstream infrastructure, and community water supply. Forest harvesting activities can increase the delivery of fine sediment to streams due to intensified erosion or mass wasting from hillslopes, roads, and stream channels. However, quantifying the effects of forest harvesting on sediment inputs to streams and the effectiveness of current best management practices (BMPs) at mitigating these effects remains a challenge. In this study, we used sediment source fingerprinting techniques to quantify and compare the sources of suspended sediment to a stream draining a recently harvested catchment and a nearby, unharvested reference catchment in the Oregon Coast Range of the U.S. Pacific Northwest. In each stream, we quantified the proportional contributions of suspended sediment from three potential source areas: hillslopes, roads, and streambanks. The primary source of suspended sediment in the harvested catchment was streambank sediment (90.2 ± 3.4%) with lesser amounts of hillslope (7.1 ± 3.1%) and road (3.6 ± 3.6%) sediment. Interestingly, the proportional contributions of suspended sediment in the reference catchment were similar, with the majority from streambanks (93.1 ± 1.8%) followed by hillslopes (6.9 ± 1.8%). There were no contributions from roads in the reference catchment, despite a similar road network as the harvested catchment. We also quantified monthly sediment mass eroded from 36 × 1 m2 hillslope plots. The sediment mass eroded from the general harvest area (96.5 ± 57.0 (SE) g) was ~10.6-times greater than the sediment collected in the riparian buffer (9.1 ± 1.9 g) and ~4.6-times greater than the sediment collected on the unharvested, reference hillslope (21.0 ± 3.3 g). While this study provides evidence of effectiveness of contemporary BMPs (e.g., riparian management areas, limits to cutblock size, reduced impact forest harvesting techniques, road building and maintenance) at mitigating sediment delivery to streams, additional research is needed as existing studies do not adequately reflect the broad range of climate, geology, topography, and vegetation in the Pacific Northwest, which drive highly variable hydrologic and geomorphic processes in the region.

Protecting timberland RMZs through carbon markets: A protocol for riparian carbon offsets

Riparian Management Zone (RMZ) allocations can place a burden on landowners due to restrictions (sometimes prohibitions) on harvesting. The opportunity cost for the landowner may be minimized by shifting the primary management objective in RMZs from timber production to compensation for above-ground carbon. Our primary objective was to compare long-term net revenue generating potential of RMZs under three scenarios: (I) compensation for carbon credits without harvesting; (II) partial harvesting using Best Management Practices (BMP) guidelines without carbon credits; (III) partial harvesting combined with carbon credits as per the California Compliance Offset Protocol. Basic stand data on trees of 2.5 cm and higher were collected in riparian forest plots along headwater streams within two experimental forests in the northeast US. The USFS Forest Vegetation Simulator was used to simulate growth and yield and schedule management activities over 20-year cutting cycles. Timber volumes and registry offset credits along with their market values were calculated for the respective scenarios and a Net Present Value (NPV) and Equal Annual Equivalent (EAE) analysis was performed under assumptions of constant prices and costs. The initial aboveground carbon stocks at both locations were 32% and 140% higher than the average value for their assessment areas. Having above-average carbon stocks and basal areas between 30 and 33 m2/ha, all scenarios returned positive NPVs and EAEs. The hardwood riparian forest had a higher NPV and EAE by not participating in the carbon markets and pursuing partial harvesting as per BMP guidelines (Scenario II) at lower discount rates but had higher NPVs and EAEs under carbon markets at higher discount rates (Scenario I and III). The conifer/mixed species riparian forest provided greater positive net revenue flows by participating in the carbon markets either in a no harvesting scenario or under partial harvesting as per guidelines in the Protocol (Scenarios I and III). Our results indicate that a protocol for compensating landowners with large forest holdings for riparian carbon offsets provides an opportunity to generate positive net revenues in scenarios in which state BMP guidelines may restrict harvesting in RMZs. Given the high density of ecologically critical headwater streams in the Northeast and potential RMZ restrictions, the carbon offset option provides landowners with the opportunity to remain economically viable.

Exploring motivation crowding around farmer incentives for riparian management in Nova Scotia

AbstractIncentive programs to encourage landowners to protect habitat should be carefully designed to avoid motivation crowding: basically, replacing intrinsic reasons such as a land ethic with extrinsic ones like payments. Little research on motivation crowding tests real programs, and no such work has been done in Canada. We surveyed farmers in Nova Scotia in 2017 to explore whether participation in a new incentive program called Wood Turtle Strides, or knowledge about a similar incentive program potentially available in the future, would alter reported motivations to use riparian setbacks and buffers. Motivations to use setbacks or buffers were heavily intrinsic across all four survey cohorts: wildlife stewardship and sacrifice motivated actions more than social pressures. We were not able to statistically test for motivational crowding due to low program uptake and thus post‐program survey responses, but there was no evidence of second‐hand crowding: farmers being motivated by hearing about a program in an adjacent jurisdiction. Findings point to the significance of wildlife stewardship for many farmers, and persistent resistance to conservation among others, as well as a risk of low additionality. More post‐program research is necessary to fully understand the program's net impact on motivations and conservation.

A laboratory study of flow characteristics in natural heterogeneous vegetation patches under submerged conditions

Existing studies on flow through vegetation have focused mainly on understanding the turbulent structure in vegetated channels of single plant type. However, in natural riverine environments, vegetation also occurs as patches with heterogeneous plant forms. The present paper investigates the flow and turbulent characteristics in heterogeneous vegetation patches at a laboratory scale. Experiments were conducted using different forms (grass, leafy and cylindrical) of natural vegetation planted, alternatively and also as a mixed variety of patches in a staggered pattern. The results show that the presence of other vegetation forms in mixed heterogeneous patch increases the velocity reduction up to 10% compared to flexible grass. Moreover, additional drag due to mixed vegetation reduces shear generated turbulence at the canopy top and shifts its peak above the canopy. In the case of heterogeneous patches, spatial heterogeneity in velocity fields and, varying zones of increased and diminished turbulence were observed. Specifically, patch form and its alignment significantly control the velocity reduction and, momentum transfer between the canopy and overflow regions. These findings and furthermore studies on heterogeneous patches may be helpful for riparian management practices in creating ecological and sediment deposition zones.

Designed Elements Improve Riparian Management Outcomes

Designed Elements Improve Riparian Management Outcomes

Current Insights into the Effectiveness of Riparian Management, Attainment of Multiple Benefits, and Potential Technical Enhancements.

Buffer strips between land and waters are widely applied measures in diffuse pollution management, with desired outcomes across other factors. There remains a need for evidence of pollution mitigation and wider habitat and societal benefits across scales. This paper synthesizes a collection of 16 new primary studies and review papers to provide the latest insights into riparian management. We focus on the following areas: (i) diffuse pollution removal efficiency of conventional and saturated buffer strips, (ii) enhancing biodiversity of buffers, (iii) edge-of-field technologies for improving nutrient retention, and (iv) potential reuse of nutrients and biomass from buffers. Although some topics represent emerging areas, for other well-studied topics (e.g., diffuse pollution), it remains that effectiveness of conventional vegetated buffer strips for water quality improvement varies. The collective findings highlight the merits of targeted, designed buffers that support multiple benefits, more efficiently interrupting surface and subsurface contaminant flows while enhancing diversity in surface topography, soil moisture and C, vegetation, and habitat. This synthesis also highlights that despite the significant number of studies on the functioning of riparian buffers, research gaps remain, particularly in relation to (i) the capture and retention of soluble P and N in subsurface flows through buffers, (ii) the utilization of captured nutrients, (iii) the impact of buffer design and management on terrestrial and aquatic habitats and species, and (iv) the effect of buffers (saturated) on greenhouse gas emissions and the potential for pollution swapping.

Conservation planning at the intersection of landscape and climate change: brook trout in the Chesapeake Bay watershed

AbstractWe developed a multi‐scale conservation planning framework for brook trout (Salvelinus fontinalis) within the Chesapeake Bay watershed that incorporates both land use and climate stressors. Our specific objectives were to (1) construct a continuous spatial model of brook trout distribution and habitat quality at the stream reach scale; (2) characterize brook trout vulnerability to climate change under a range of future climate scenarios; and (3) identify multi‐scale restoration and protection priorities for brook trout across the Chesapeake Bay watershed. Boosted regression tree analysis predicted brook trout occurrence at the stream reach scale with a high degree of accuracy (CV AUC = 0.92) as a function of both natural (e.g., water temperature and precipitation) and anthropogenic (e.g., agriculture and urban development) landscape and climatic attributes. Current land use activities result in a predicted loss of occurrence in over 11,000 stream segments (40% of suitable habitat) and account for over 15,000 km (45% of current value) of lost functional brook trout fishery value (i.e., length‐weighted occurrence probability) in the Chesapeake Bay watershed. Climate change (increased ambient temperatures and altered precipitation) is projected to result in a loss of occurrence in at least 3000 additional segments (19% of current value) and at least 3000 km of functional fishery value (9% of current value) by 2062. Model outcomes were used to identify low‐ and high‐quality stream segments within relatively intact and degraded sub‐watersheds as restoration and protection priorities, respectively, and conservation priorities were targeted in watersheds with high projected resilience to climate change. Our results suggest that traditional restoration activities, such as habitat enhancement, riparian management, and barrier removal, may be able to recover a substantial amount of brook trout habitat lost to historic landscape change. However, restoration efforts must be designed within the context of expected impacts from climate change or those efforts may not produce long‐term benefits to brook trout in this region.

Applying the ecology of aquatic–terrestrial linkages to freshwater and riparian management

Applying the ecology of aquatic–terrestrial linkages to freshwater and riparian management

Aquatic–terrestrial linkages provide novel opportunities for freshwater ecologists to engage stakeholders and inform riparian management

AbstractStudies of aquatic–terrestrial ecosystem linkages explore the mechanisms by which components of one ecosystem, such as the aquatic insect community in a stream, directly affect components o...

Invertebrate responses to land use in tropical streams: discrimination of impacts enhanced by analysis of discrete areas

We identified influences of land-use disturbances on invertebrate assemblages in streams draining eight areas of the Great Barrier Reef catchment in tropical Australia (~15.7–22°S), a region of high biodiversity. We used distance-based linear modelling (DistLM) to analyse assemblage data (103 taxa), richness and the SIGNAL2 taxon sensitivity index. DistLM of assemblages explained ~40% of variation across all samples and 7–54% of variation in individual areas. DistLM of richness and SIGNAL2 explained respectively 19–81 and 26–95% of variation. Explanatory variables were land use (especially cropping and grazing v. forest), riparian width, instream habitat, climate (drier south) and water quality (conductivity greater in south). Local impacts of activities such as mining were evident in models of individual areas. A detailed comparison of streams with contrasting riparian management demonstrated a 25% loss of richness, but no change in SIGNAL2 score. Accounting for local environmental gradients and using measures appropriate to the type of disturbance improved identification of impacts, and could form a framework for future regional monitoring of stream ecological condition. The impacts identified may be mitigated by remediation such as riparian rehabilitation, although management at catchment scales is required to be effective.

Identifying riparian climate corridors to inform climate adaptation planning.

Riparian habitats have been frequently identified as priority areas for conservation under climate change because they span climatic gradients and have cool, moist microclimates relative to surrounding areas. They are therefore expected to act as dispersal corridors for climate-induced species range shifts and to provide microclimatic refugia from warming. Despite recognition of these values, rigorous methods to identify which riparian areas are most likely to facilitate range shifts and provide refugia are currently lacking. We completed a novel analysis across the Pacific Northwest, USA, that identifies potential riparian corridors featuring characteristics expected to enhance their ability to facilitate range shifts and provide refugia. These features include large temperature gradients, high canopy cover, large relative width, low exposure to solar radiation, and low levels of human modification. These variables were used to calculate a riparian climate-corridor index using a multi-scale approach that incorporates results ranging in scale from local watersheds to the entire Pacific Northwest. Resulting index values for potential riparian corridors in the Pacific Northwest were highest within mountainous areas and lowest within relatively flat, lowland regions. We also calculated index values within ecoregions, to better identify high-value riparian climate corridors within the relatively flat, degraded areas where they may most contribute to climate adaptation. We found that high-value riparian climate-corridors are least protected in flat, lowland areas, suggesting that such corridors should be high priorities for future conservation effort. Our analysis provides critical information on valuable riparian climate-corridors to guide climate adaptation efforts (and riparian management and restoration efforts) in the Pacific Northwest, while offering a novel approach that may be applied to similar efforts in other geographies.

A novel application of remote sensing for modelling impacts of tree shading on water quality

Uncertainty in capturing the effects of riparian tree shade for assessment of algal growth rates and water temperature hinders the predictive capability of models applied for river basin management. Using photogrammetry-derived tree canopy data, we quantified hourly shade along the River Thames (UK) and used it to estimate the reduction in the amount of direct radiation reaching the water surface. In addition we tested the suitability of freely-available LIDAR data to map ground elevation. Following removal of buildings and objects other than trees from the LIDAR dataset, results revealed considerable differences between photogrammetry- and LIDAR-derived methods in variables including mean canopy height (10.5 m and 4.0 m respectively), percentage occupancy of riparian zones by trees (45% and 16% respectively) and mid-summer fractional penetration of direct radiation (65% and 76% respectively). The generated data on daily direct radiation for 2010 were used as input to a river network water quality model (QUESTOR). Impacts of tree shading were assessed in terms of upper quartile levels, revealing substantial differences in indicators such as biochemical oxygen demand (BOD) (1.58–2.19 mg L−1 respectively) and water temperature (20.1 and 21.2 °C respectively) between ‘shaded’ and ‘non-shaded’ radiation inputs. Whilst the differences in canopy height and extent derived by the two methods are appreciable they only make small differences to water quality in the Thames. However such differences may prove more critical in smaller rivers. We highlight the importance of accurate estimation of shading in water quality modelling and recommend use of high resolution remotely sensed spatial data to characterise riparian canopies. Our paper illustrates how it is now possible to make better reach scale estimates of shade and make aggregations of these for use at river basin scale. This will allow provision of more effective guidance for riparian management programmes than currently possible. This is important to support adaptation to future warming and maintenance of water quality standards.

Litter decomposition is driven by microbes and is more influenced by litter quality than environmental conditions in oil palm streams with different riparian types

Rapid and extensive conversion of tropical forests into oil palm (Elaeis guineensis) (OP) plantations pose serious threats to tropical stream processes. To mitigate land use change impacts on stream ecosystems, retention of riparian vegetation is typically proposed. We evaluated the effectiveness of a gradient of riparian qualities in oil palm streams: (1) natural forest; (2) OP-native forested buffer; (3) OP-native understory, no chemical input (OPOP) and (4) OP-no buffer, to mitigate impacts on in-stream litter processing. Leaf bag method entry using two leaf species of contrasting litter quality (Macaranga tanarius and OP) were deployed into streams. Across all riparian types, microbes were the main drivers of decomposition with negligible macroinvertebrate shredding activities. Leaf decomposition rates were more influenced by litter quality than changes in environmental conditions in the different riparian types. Across all sites, native Macaranga litter decomposed approximately 5× faster than OP litter possibly due to high structural compounds in OP leaves. Macaranga litter was also more susceptible to changes in environmental conditions as leaf decomposition positively correlated to phosphorus and potassium content. However, OP leaves were resilient to stream environmental changes and decomposed slower only at OPOP sites. These varying responses reveal complex interactions within tropical stream ecosystems. We suggest that riparian management strategies as well as plans to restore functioning in degraded tropical streams should ensure a wide diversity of native riparian tree species in order to effectively mitigate adverse OP plantation impacts on tropical stream functioning.

Use of artificial habitats to detect spawning sites for the conservation of Galaxias maculatus, a riparian-spawning fish

Galaxias maculatus is a diadromous riparian-spawning fish that supports an important fishery. Eggs develop terrestrially as with several other teleost fishes. Spawning habitat occurs in specific locations near rivermouths and its protection is a conservation priority. However, quantifying the areas involved is hampered by high egg mortality rates on degraded waterway margins. We hypothesised that temporary artificial habitat would detect spawning in these situations producing a useful indicator for riparian management. We installed arrays of straw bales as artificial habitat in two independent experiments over consecutive years and assessed their impact using pairwise Before-After-Control-Impact (BACI) experimental designs. We tested degraded gaps within the distribution of known spawning sites and also areas further upstream and downstream. Nine spawning occurrences were recorded on artificial habitats in 2015, 22 in 2016, and two on paired controls. Both experiments produced a significant effect for artificial habitats deployed in degraded gaps within the known spawning site distribution (p = 0.0001) providing evidence that these locations should be regarded as actual or potential spawning sites. In 2016 the technique also produced a significant effect downstream of known sites in one of the study catchments (p = 0.0375). We believe the use of artificial habitats as a detection tool could be useful in a variety of management contexts. These include identifying areas for protection, as confirmation of site suitability prior to making restoration investments, and in investigations to support the migration of habitats to new locations under climate change, since these may currently be degraded.

Integrating process‐based flow and temperature models to assess riparian forests and temperature amelioration in salmon streams

AbstractThe importance of riparian tree cover in reducing energy inputs to streams is increasingly recognized in schemes to mitigate climate change effects and protect freshwater ecosystems. Assessing different riparian management strategies requires catchment‐scale understanding of how different planting scenarios would affect the stream energy balance, coupled with a quantitative assessment of spatial patterns of streamflow generation. Here, we use the physically based MIKE SHE model to integrate simulations of catchment‐scale run‐off generation and in‐stream hydraulics with a heat transfer model. This was calibrated to model the spatio‐temporal distribution of hourly stream water temperature during warm low flow periods in a Scottish salmon stream. The model was explored as a “proof of concept” for a tool to investigate the effects of riparian management on high stream water temperatures that could affect juvenile Atlantic salmon. Uncertainty was incorporated into the assessment using the generalized likelihood uncertainty estimation approach. Results showed that by decreasing both the warming (daylight hours) and the cooling (night‐time hours) rates, forest cover leads to a reduction of the temperature range (with a delay of the time to peak by up to 2 hr) and can therefore be effectively used to moderate projected climate change effects. The modelling presented here facilitated the quantification of potential mitigating effects of alternative riparian management strategies and provided a valuable tool that has potential to be utilized as an evidence base for catchment management guidance.

On the banks of the Red Cedar: toward socio-ecologically robust riparian management in an iconic Michigan river

Land use is continually evolving in river watersheds and riparian zones, particularly in areas containing dense human populations requiring infrastructure development. Land use planners in south-central Michigan, USA, are challenged to balance infrastructure needs with the ecological integrity of the iconic Red Cedar River, which flows through the Michigan state capital (Lansing) and surrounding suburban and rural areas and supports freshwater diatoms, mussels, fishes, and other organisms. Although land use goals in the Red Cedar River watershed include protecting riverine biodiversity, decision-makers need a systematic method for predicting and mitigating effects of land use change on the river ecosystem. We developed a framework for evaluating habitat associations of diatoms and native unionid mussels in the Red Cedar River using field collections and mixed-effects modeling to facilitate socio-ecologically informed riparian management. Diatoms were significantly more abundant and genus-rich in riffles and pools than runs, whereas mussels were more abundant in riffles than pools, with intermediate run abundance. Diatom relative abundance was most affected by pH (+ effect), depth (+), and water temperature (+), similar to diatom genus richness (pH and depth +). Mussel relative abundance was best explained by depth (–), pH (+), and percent forest cover (+), similar to mussel length (depth +, pH –). Results from this study underscore riparian management strategies for optimizing forest cover, depth, and pH to promote ecologically favorable conditions for diatoms and mussels in the Red Cedar River (e.g. stable, near-neutral pH; diverse tree species with ≥60% forest cover). Advancing understanding of aquatic biota and their habitats, this research provides a foundation for socio-ecologically balanced land use planning in the Red Cedar River and other riverine ecosystems.