The utility of spatial data to delineate river riparian functions and management zones: A review

Decomposition of exotic versus native aquatic plant litter in a lake littoral zone: Stoichiometry and life form analyses

The decomposition rates and stoichiometric characteristics of many aquatic plants remain unclear, and our understanding of material flow and nutrient cycles within freshwater ecosystems is limited. In this study, an in-situ experiment involving 23 aquatic plants (16 native and 7 exotic species) was carried out via the litter bag method for 63 days, during which time the mass loss and nutrient content (carbon (C), nitrogen (N), and phosphorus (P)) of plants were measured. Floating-leaved plants exhibited the highest decomposition rate (0.038 ± 0.002 day-1), followed by submerged plants and free-floating plants (0.029 ± 0.002 day-1), and emergent plants had the lowest decomposition rate (0.019 ± 0.001 day-1). Mass loss by aquatic plants correlated with stoichiometric characteristics; the decomposition rate increased with an increasing P content and with a decreasing C content, C:N ratio, and C:P ratio. Notably, the decomposition rate of submerged exotic plants (0.044 ± 0.002 day-1) significantly exceeded that of native plants (0.026 ± 0.004 day-1), while the decomposition rate of emergent exotic plants was 55 ± 4 % higher than that of native plants. The decomposition rates of floating-leaved and free-floating plants did not significantly differ between the native and exotic species. During decomposition, emergent plants displayed an increase in C content and a decrease in N content, contrary to patterns observed in other life forms. The P content decreased for submerged (128 ± 7 %), emergent (90 ± 5 %), floating-leaved (104 ± 6 %), and free-floating plants (32 ± 6 %). Exotic plants released more C and P but accumulated more N than did native plants. In conclusion, the decomposition of aquatic plants is closely linked to litter quality and influences nutrient cycling in freshwater ecosystems. Given these findings, the invasion of the littoral zone by submerged and emergent exotic plants deserves further attention.

Delineation of riparian areas based on the application of two-dimension hydraulic modelling

This paper presents a proposal for riparian area delineation relying on topographical, hydrological, vegetation, and soil data together with numerical modelling of the river hydrodynamics. The two-dimensional model Iber is used to simulate 2.5, 10, 50, and 100-years return period flood events, and new code is developed to simulate the main hydrological processes of the river-riparian system to generate riparian zone maps. Results show that changes in topography and discharge direction between river and groundwater both influence the riparian area extent, and that temporal evolution of the riparian zone is much slower than that of the flood, and its extension can continue to increase while the flood recedes, but only to a certain extent, conditioned by topography, soil characteristics, and vegetation. A simple but efficient numerical code for understanding and simulating the riparian dynamics has been developed, which constitutes a proposal for a new riparian delineation approach useful for research and management applications, and which can also be a useful tool for gaining a better understanding of the riparian boundary behavior under different ecohydrological conditions.

Spatial distribution, source identification, and risk assessment of heavy metals in riparian soils of the Tibetan plateau

Riparian soils in the lower sections of the Lhasa River were chosen as the research focus, to examine the characteristics and sources of heavy metals in riparian soils of high-cold regions. To investigate the influence of various factors on the geographical distribution of heavy metals, three horizontal and one vertical profiles were considered. The geoaccumulation index, prospective ecological risk index, and enrichment factor were used to evaluate the extent of soil contamination. Correlation analysis and the positive-matrix-analysis receptor model were used to quantitatively examine the sources of the elements. According to the soil-evaluation, the topsoil was more polluted than the deep soil. Overall, the soil was slightly degraded and posed minor ecological concern. Cd was the primary contributor to the overall contamination, with moderate and considerable risk levels at certain locations. Five sources were identified for the six heavy metals. Transportation and agricultural production were the principal sources of Cd. Ni and Cr were mostly connected to agricultural practices and weathering of parent-soil materials. Pb and Zn were mostly related to geological history, geothermal development, and traffic pollution. Mineral resource development has had a major impact on Cu. Non-carcinogenic risk index of each heavy metal and their total value were <1, indicating they are not harmful to human health. The riparian soil of the Lhasa River Basin contains heavy metals from various sources; therefore, it is important to monitor these heavy metals. This study provides a scientific foundation for the safe utilization and classification of soils in high cold regions.

Raccoon spatial ecology in the rural southeastern United States

The movement ecology of raccoons varies widely across habitats with important implications for the management of zoonotic diseases such as rabies. However, the spatial ecology of raccoons remains poorly understood in many regions of the United States, particularly in the southeast. To better understand the spatial ecology of raccoons in the southeastern US, we investigated the role of sex, season, and habitat on monthly raccoon home range and core area sizes in three common rural habitats (bottomland hardwood, upland pine, and riparian forest) in South Carolina, USA. From 2018-2022, we obtained 264 monthly home ranges from 46 raccoons. Mean monthly 95% utilization distribution (UD) sizes ranged from 1.05 ± 0.48 km2 (breeding bottomland females) to 5.69 ± 3.37 km2 (fall riparian males) and mean monthly 60% UD sizes ranged from 0.25 ± 0.15 km2 (breeding bottomland females) to 1.59 ± 1.02 km2 (summer riparian males). Males maintained home range and core areas ~2-5 times larger than females in upland pine and riparian habitat throughout the year, whereas those of bottomland males were only larger than females during the breeding season. Home ranges and core areas of females did not vary across habitats, whereas male raccoons had home ranges and core areas ~2-3 times larger in upland pine and riparian compared to bottomland hardwood throughout much of the year. The home ranges of males in upland pine and riparian are among the largest recorded for raccoons in the United States. Such large and variable home ranges likely contribute to elevated risk of zoonotic disease spread by males in these habitats. These results can be used to inform disease mitigation strategies in the southeastern United States.

An updated review of the efficacy of buffer zones in warm/temperate and cold climates: Insights into processes and drivers of nutrient retention

The transport of excess nutrients into freshwater systems constitutes a serious risk to both water quality and aquatic health. Vegetated buffer zones (VBZs) next to waterways are increasingly used in many parts of the world to successfully intercept and eliminate pollutants and other materials in overland flow, especially in warm or temperate regions. The major processes for the retention of pollutants in VBZ are microbial degradation, infiltration, deposition, filtration, adsorption, degradation, assimilation, etc. The effectiveness of the VBZ relies on several environmental factors, including BZ width, runoff intensity, slope, soil texture, temperature, vegetation type, etc. Among the reported factors, cold weather possesses the most detrimental impact on many of the processes that VBZ are designed to carry out. The freezing temperatures result in ice formation, interrupting biological activity, infiltration and sorption, etc. In the last twenty years, burgeoning research has been carried out on the reduction of diffuse nutrient pollution losses from agricultural lands using VBZ. Nonetheless, a dearth of studies has dealt with the problems and concerns in cold climates, representing an important knowledge gap in this area. In addition, the effectiveness of VBZ in terms of nutrient removal abilities varies from -136% to 100%, a range that reveals the incertitude surrounding the role of VBZ in cold regions. Moreover, frozen soils and plants may release nutrients after undergoing several freeze-thaw cycles followed by runoff events in spring snowmelt. This review suggests that the management and design of VBZ in cold climates needs close examination, and these systems might not frequently serve as a good management approach to decrease nutrient movement.

A GIS workflow for the identification of corridors of geomorphic river recovery across landscapes

The provision of a simplified GIS workflow to analyse the Open Access NSW River Styles database provides non-technical GIS users in river management with the ability to quickly and efficiently obtain information to assist them in catchment-scale rehabilitation prioritisation. Publicly available proprietary GIS software, standard GIS tools, and a packaged digital elevation model are used to demonstrate the ease of analysis for those with some GIS skills, to establish where corridors of geomorphic river recovery occur or could be built at-scale. Rather than a 'single use' report, this novel application of GIS methods is designed to be used by those responsible for river management, replicated across landscapes and adjusted according to preferences. Decision making becomes more cost effective, and adaptive to local circumstances and changing river management priorities. The method could also be adjusted and applied to other river monitoring and condition datasets where polyline data layers are available.

Effect of topographical features on hydrologically connected riparian landscapes across different land-use patterns in colossal dams and reservoirs

Topographic features impact the riparian landscape, which shapes reservoir ecosystems. We know little about ecological network parameter (ENP) responses to topographical features (riparian width, stream-channel width, slope, and elevation) from three land-use areas (rural, urban, and rural-urban transitional) in larger dams and reservoirs globally. This study used a field-based approach with 305 transects on an inundated area of 58,000 km² inside the Three Gorges Dam Reservoir (TGDR) in China. We discovered that topographical features influenced ENPs differently, involving parameters of plant cover, regeneration, exotics, erosion, habitat, and stressors. As per the Pearson correlation (p < 0.05), riparian width had the most significant effect on transitional ENPs and the least impact on urban ENPs. Riparian width showed the most important influence on the parameters of exotics (with r ≤ -0.44) and erosion (r ≤ 0.56). In contrast, stream-channel widths had the greatest effect on rural ENPs and the least on urban and transitional ENPs. The erosion parameters were the most affected (r ≤ -0.26) by stream width. The slope showed relationships with the fewest ENPs in all three areas and influenced the stress (with a range of -0.51 <r < 0.85) and erosion (r ≤ -0.39) parameters. The impact of elevation was higher in urban areas and was positively correlated with the parameters of plant cover (r ≤ 0.70), erosion (r ≤ 0.58), and habitat (r ≤ 0.69). These results justify the policy emphasis on riparian areas that are managed using the same techniques, which generally ignores their topographical features.

Baseline assessment of the hydrological network and land use in riparian buffers of Pampean streams of Uruguay

The integrated assessment of stream networks and terrestrial land use contributes a critical foundation for understanding and mitigating potential impacts on stream ecology. Riparian zone delineation and management is a key component for regulating water quality, particularly in agricultural watersheds. We present a national assessment of riparian zone land uses according to stream order for the entire hydrological network in the Uruguayan landscape in Southeastern South America. We classified over 82,500 km of streams and rivers in Uruguay into seven Strahler order classes and delineated riparian buffers of 100 and 500 m, depending on stream order, covering a total of 13% of the terrestrial land area in Uruguay. Natural vegetation cover in riparian zones averaged 77% among basins, whereby natural grassland dominated first and second order stream buffers at 58% and 49%, respectively. This highlighted the importance of grasslands in headwater regions of the country. Riparian forests formed corridors along larger streams, representing a mere 9% of buffers in first order streams but reaching 46% of buffers of 6th order streams. Among the six major basins of Uruguay, we found differences in the relative importance of riparian forests and crop cover in headwater stream riparian zones, as well as differences in relative crop cover within riparian zones. Results show that streams in subtropical grassland landscapes originate in open grassland environments, which has major implications for thermal regimes, carbon inputs, and stream biodiversity. Riparian buffer management should consider geographic differences among different basins and ecoregions within Uruguay.

Impacts of Stressors on Riparian Health Indicators in the Upper and Lower Indus River Basins in Pakistan

Riparian zones along rivers and streams provide ecosystem services that may change over time as disturbances increase and deteriorate these buffer zones globally. The effect of stressors on ecosystem services along the rivers in underdeveloped countries is unclear, which impacts the environment directly in the form of riparian health indicators (RHIs). This study fills this gap and measures the impact of stressors on RHIs (parameters of habitat, plant cover, regeneration, exotics, and erosion) in the Indus River basin (IRB) in Pakistan. Data on 11 stressors and 27 RHIs were collected using a field-based approach in 269 transects in the upper and lower Indus basins (UIB and LIB) in 2020 and analyzed using multivariate statistical methods. The Kruskal-Wallis tests (p < 0.05) indicated that RHIs varied significantly under the influence of stressors in the UIB and LIB. However, their highest mean values were found in the UIB. Principal component analysis revealed the key RHIs and stressors, which explained 62.50% and 77.10% of the variance, respectively. The Pearson correlation showed that stressors had greater impacts on RHIs in LIB (with r ranging from -0.42 to 0.56). Our results also showed that stressors affected RHI indices with r ranging from -0.39 to 0.50 (on habitat), -0.36 to 0.46 (on plant cover), -0.34 to 0.35 (on regeneration), -0.34 to 0.56 (on erosion), and -0.42 to 0.23 (on exotics). Furthermore, it was confirmed by the agglomerative hierarchical cluster that indices and sub-indices of RHIs and stressors differ across the UIB and LIB. These findings may serve as guidance for managers of large rivers and ecosystem service providers to minimize the environmental impact of stressors in terms of RHIs.

The migration and microbiological degradation of dissolved organic matter in riparian soils

Riparian zones are important natural means of water purification, by decreasing the aqueous concentration of terrestrial organic matter (OM) through adsorption and microbial degradation of the organic matter within the aquatic ecosystem. Limited studies have been reported so far concerning the migration of dissolved organic matter (DOM) in the horizontal and vertical planes of riparian zones. In this study, the migration of DOM in riparian zones, from forest soil to wetland soil, and with soil depth, were explored, based on a case study reservoir. Results showed that riparian wetlands can absorb the OM from the forest soils and adjacent reservoir, and act as a major OM sink through microbial action. Methylomirabilota and GAL15 bacteria increased with soil depth for the two soil systems, and the wetland soil system also contained microbial sulfates, nitrates and carbonates. These microorganisms successfully utilize the Fe³⁺, SO₄^-, and CO₃^- as electron acceptors in the wetland system, resulting in enhanced OM removal. Although the variation of soil DOM in the vertical direction was the same for both forest and wetland soils, the Chemical structure of the DOM was found to be significantly different. Furthermore, the soil was found to be the main source of DOM in the forest ecosystem, with lignin as the main ingredient. The lignin structure was gradually oxidized and decomposed, with an increase in carboxyl groups, as the lignin diffused down into the soil and the adjacent reservoir. PLS-PM analysis showed that the soil physicochemical properties were the main factors affecting DOM transformation. However, microbial metabolism was still the goes deeper affecting factor. This study will contribute to the analysis that migration and transform of soil organic matter in riparian zone.

Environmental literacy affects riparian clean production near major waterways and tributaries

Although environmental illiteracy threatens the functioning of landscapes throughout the world, it is frequently ignored. The traditional wisdom assumes that suspicions will evaporate when the public and government authorities are provided with new information. Despite significant efforts to enhance riparian corridor output, limited data are available on the effect of environmental literacy metrics (ELMs) on clean production elements (CPEs) across various streams (e.g., main rivers and tributaries) within impoundments. This study examined such effects within the China Three Gorges Dam Reservoir area (TGDRA) by collecting 336 transects that assessed the breadth of effects on 58,000 km² in 2019. The network visualization revealed 7234 papers published over the last 121 years, each of which focused on themes such as plant cover, regeneration, exotics, erosion, habitat, and stressors. The bar graph showed that the general public lacked understanding of environmental literacy (e.g., knowledge, attitudes, and behavior), which influenced plant cover elements most in tributary zones but had little direct effect on regeneration. Locals' environmental literacy had the greatest impact on CPEs, with Pearson correlation coefficients ranging from -0.69 <r < 0.96 in the main river zones. Moreover, public employees' environmental literacy had a stronger correlation with CPEs (-0.58 <r < 0.83) within the main river regions. Farming systems, exposed soil, dominant grass regeneration, and instream structures, including pollution, were among the most notable CPEs within the TGDRA. According to hierarchical approaches, CPEs and ELMs change substantially across stream types. CPEs and ELMs vary significantly around main rivers and tributaries, requiring efforts to raise the public understanding of the worldwide impacts of stream health on humans.

Mapping riparian zone macro litter abundance using combination of optical and thermal sensor

A significant increase in the world's population will lead to an increase in consumption and, therefore, an increase in global waste. Various attempts have been made to monitor and map waste, but the proposed approaches are difficult and complicated, and they incur high costs. In this study, to overcome limitations in monitoring and mapping plastic waste, using combined optical and thermal sensors installed on drones is proposed. The study area is the riparian zone, or the zone around the river, where the accumulation of plastic waste at the mouth of the river eventually reaches the sea. The image data obtained were processed using machine learning methods to produce high accuracy and precision. To determine the effectiveness of the proposed method, an accuracy assessment was conducted. The results of this study indicate that the combination of optical and thermal sensors provides the best accuracy compared to using only single optical or thermal image data.

A metric-based analysis on the effects of riparian and catchment landuse on macroinvertebrates

Woody riparian vegetation along rivers and streams provides multiple functions beneficial for aquatic macroinvertebrate communities. They retain fine sediments, nutrients and pesticides, improve channel hydromorphology, control water temperature and primary production through shading and provide leaves, twigs and large wood. In a recent conceptual model (Feld et al., 2018), woody riparian functions were considered either independent from large-scale landuse stressors (e.g. shading, input of organic matter), or dependent on landuse at larger spatial scales (e.g. fine sediment, nutrient and pesticide retention). We tested this concept using high-resolution data on woody riparian vegetation cover and empirical data from 1017 macroinvertebrate sampling sites in German lowland and mountain streams. Macroinvertebrate metrics indicative for individual functions were used as response variables in structural equation models (SEM), representing the hierarchical structure between the different considered stressors at different spatial scales: catchment, upstream riparian, local riparian and local landuse cover along with hydromorphology and water quality. The analysis only partly confirmed the conceptual model: Biotic integrity and water quality were strongly related to large-scale stressors as expected (absolute total effect 0.345-0.541), but against expectations, fine sediments retention, considered scale-dependent in the conceptual model, was poorly explained by large-scale stressors (absolute total effect 0.027-0.231). While most functions considered independent from large-scale landuse were partly explained by riparian landuse cover (absolute total effect 0.023-0.091) they also were nonetheless affected by catchment landuse cover (absolute total effect 0.017-0.390). While many empirical case studies at smaller spatial scales clearly document the positive effects of restoring woody riparian vegetation, our results suggest that most effects of riparian landuse cover are possibly superimposed by larger-scale stressors. This does not negate localized effects of woody riparian vegetation but helps contextualize limitations to successful restoration measures targeting the macroinvertebrate community.

Impacts of riparian width and stream channel width on ecological networks in main waterways and tributaries

Riparian buffer width and stream channel width have different impacts on ecological networks (e.g., plant cover, regeneration, exotics, erosion, habitat, and stressors) and provide various ecosystem services. The protection of riparian zones of increasing widths for higher-order streams and connected tributaries alongside mega-reservoirs and around dams is of great global significance. However, it remains unclear which protection strategies are most effective for such zones. By applying a rapid field-based approach with 326 transects on an inundated area of 58,000 km² within the Three Gorges Dam Reservoir (TGDR) in China, we found that riparian buffer areas were influenced differently by broad-ranging widths. The riparian buffer width of 101.84 ± 72.64 m (mean ± standard deviation) had the greatest impact on the main waterway, whereas the stream channel width of 99.87 ± 97.10 m was most influential in tributaries. The correlation coefficient strengths among ecological and stress parameters (independently) were relatively greater in the main waterway riparian zones; the highest value was r = 0.930 using Pearson correlation (p < 0.05). In contrast, stress parameters revealed substantial and strong relationships with ecological parameters in tributaries, with the highest value being r = 0.551. Riparian width had the strongest influence on buffer vegetation scales, high-impact exotics, and bank stability. In comparison, channel width had the greatest effect on tree roots, dominant tree regeneration, and agricultural farming. These parameters showed distinctive responses in the shapes of indexing in higher-order streams and connected tributaries. These observations confirm the urgent need for research on regional-based extended riparian areas managed by the same administration strategies. Revised guidelines are needed to protect massive dam and reservoir ecosystems from further deterioration.

Charting a perfect storm of water quality pressures

The agri-food economy can be a significant driver of water quality pressures but the role of hydro-meteorological patterns in a changing climate also requires consideration. For this purpose, an assessment was made of a ten-year synchronous high temporal resolution water quality and hydro-meteorological dataset in Irish agricultural catchments. Changes occurring to rainfall intensity and soil temperature patterns were found to be important drivers of nutrient mobility in soils. There were links between the intensity of the North Atlantic Oscillation over the decade and large shifts in baseline nutrient concentrations in catchments. The data also revealed extreme weather impacts to pollution patterns including short periods of rain induced nutrient flux, that exceeded average annual mass loads in these catchments, and drought influences on point source pollution. These influences need consideration, and may require different mitigation strategies, as links between water quality land use pressure and water quality state in regulatory reviews. In a decade of both increased land use source and hydro-meteorological transport pressures, water quality natural capital in Ireland has faced a perfect storm. Such conditions are difficult to model and only revealed in high temporal resolution datasets.

Assessing riparian zone changes under the influence of stress factors in higher-order streams and tributaries: Implications for the management of massive dams and reservoirs

Riparian ecosystem services along higher-order streams and connected tributaries may change over time as disturbances continuously increase, resulting in diverse deterioration of buffer zones. How habitat, plant cover, regeneration, erosion, and exotic parameters (riparian health conditions) change within huge dams and reservoirs worldwide is an unanswered question. We used multivariate statistical techniques to assess changes in riparian health parameters affected by disturbances identified in 304 transects within the Three Gorges Dam Reservoir, China, and associated tributaries. Kruskal-Wallis tests (p < 0.01) revealed high diversity in habitat, plant cover, regeneration, erosion, and overall stream condition. There was also notable variance relating to exotic and pressure parameters. The critical variables of riparian health indicators and stress factors identified by principal component analysis explained 58.40% and 74.6% (in the main waterway) and 53.23% and 71.0% (in the tributaries) of the total variance. Among riparian health indicators, one habitat parameter (riparian vegetation width) in the main waterway and one regeneration parameter (tree size classes) in tributaries contributed greatly, along with other specified parameters. Furthermore, stress factors such as farming systems, land-use types, and pollutant activity variables had the highest impact on these water bodies. In comparison, counting stress factors alone showed more deterioration in the main waterway with a range of (r = -0.527- 0.493), as determined using Pearson correlation (p < 0.05). Furthermore, after indexing, the parameters exhibited weaker coefficient values in tributaries, where exotic correlated negatively with other indexed values. These findings are relevant for managers of massive dam and reservoir ecosystems seeking to mitigate environmental and socioeconomic losses.