Riparian Buffer Strips Research Articles

Riparian buffer strips promote biomass, species richness and abundance of flying insects in agricultural landscapes

Agricultural intensification is debated as one of the major drivers for the decline of insect biodiversity. Agri-environmental schemes (AES) are a common measure to promote biodiversity in agriculture by granting compensational payments to farmers for environmentally friendly practices. In this study we examined the effect of buffer strips of at least 5 m width, adjacent to small watercourses and drainage ditches, on insect biomass and insect species richness in agricultural landscapes. We selected ten arable fields in each of four regions in lower and upper Bavaria, Southern Germany. 25 out of 40 sites had a buffer strip between arable crops and watercourse. Insects were sampled at three time periods (May/June, June/July and August/September) for two weeks each. In each period two samples were collected (one per week). On each site Malaise traps were set up in 5 and 80 m distance to the embankment of the watercourse. Half of the samples was then subjected to metabarcoding and the other half was classified into different insect groups by morphological identification and the number of the individuals for each group was counted. For hoverflies (Syrphidae), individuals were identified at species-level. Data on vegetation structure (cover of grasses and herbs) in the studied riparian buffer strips was collected and correlated with number of species, abundances and biomass of flying insects. The five taxonomic orders with the highest species richness and individual numbers were: Diptera, Hymenoptera, Coleoptera, Lepidoptera and Hemiptera. Diptera dominated hereby with 34% of all species and 81% of all individuals. On average, mixed models indicated 31% higher insect biomass, 15% higher species richness and 29% higher individual numbers of flying insects in buffer strips at 5 m distance to the watercourse compared to sites with no buffer strip. The effect was even stronger for butterflies (32% higher species species richness, 70% more individuals) and hoverflies (24% higher species richness, 51% more individuals). In the presence of a buffer strip significantly higher numbers were found for total individuals, Diptera, Hymenoptera and Coleoptera. In 80 m distance to the watercourse, the samples of flying insects were not significantly influenced by a riparian buffer strip. This study highlights the importance of buffer strips in agricultural regions and their multifunctional potential in fostering biodiversity additionally to their acknowledged use for water protection. Ideally, buffer strips are rich in herbs and inflorescences and are therefore beneficial for the insect fauna by serving as valuable habitat with high potential connectivity at landscape level.

Planting trees in buffer strips for attenuating phosphorus runoff in Jiangsu Province, China

AbstractIn the last four decades, the Jiangsu province, like the rest of China, has undergone rapid economic development coupled with a rapid increase in environmental pollution. Freshwater ecosystems have been particularly affected. In Lake Tai, China's third‐largest freshwater lake by volume, water quality has been severely reduced. There is a renewed interest in establishing riparian buffer strips in China as a conservation practice for mitigating agricultural non‐point source pollution. To study the effect of riparian buffers on phosphorus attenuation, eight 50 m × 20 m plots were established between a rice farm and the shore of Lake Tai in China, with the 20 m width facing the lake shore. They were planted with hybrid poplar (Populus deltoides × euramericana), hybrid cypress (Taxodium ascendens × mucronatum), or a mixture of both at densities of 2 m × 3 m, 2 m × 5 m, or 5 m × 5 m, while one plot was left as a control. Samples collected from soil, tree leaves, and groundwater during 2014–2018 were analyzed for multiple forms of phosphorus. Results indicated that riparian buffer width and time (year) were the most significant factors of phosphorus attenuation on all plots. Tree density had a minor effect, with medium density being the most effective, and we found negligible differences among hybrid tree species on attenuating phosphorus. Farmers should use densely vegetated buffer strips at least 15 m wide to ensure a significant reduction in nutrient runoff. Species selection should be based on market value and ecological benefits.

Drivers of tree establishment in planted windbreaks and riparian buffers: A case study of farms in southern Quebec, Canada

Successfully established windbreaks and riparian buffers contribute to protection of soils, crops, watercourses and biodiversity, and help to combat climate change. To improve establishment success of trees planted to form these agroforestry systems, identifying the factors influencing their survival and growth is crucial. We related survival and size of trees planted in windbreaks and riparian buffer strips to 23 abiotic, biotic, structural and technical explanatory factors using multiple generalized linear models. We sampled 52 windbreaks and 26 riparian buffer strips planted in different cultivated fields in southern Quebec (Canada). We analyzed volunteer vegetational composition in the tree planting right-of-way relative to eight explanatory factors. Average survival of planted trees was 86.4% and varied mainly with planting site; tree survival was negatively and significantly correlated with soil pH. We modelled correlations between size of the ten most frequently occurring tree species and 20 explanatory factors, of which six were significant, i.e., method of volunteer vegetation control, soil texture, soil preparation before planting, volunteer vegetation abundance, tree row structure and agroforestry system type (windbreak vs riparian buffer). Relative abundance of different functional types of volunteer vegetation was influenced mainly by the age of agroforestry systems. To increase tree establishment success in winbreaks and riparian buffers, species must be properly selected for planting based upon edaphic conditions, while implementing soil preparation prior to planting and maintaining sufficient spacing between trees to optimize long-term growth. Our results suggest that tree establishment in windbreaks and riparian buffers within an intensive agricultural context should not be perceived as a barrier to their adoption.

Evaluating the impacts of SRC willows on phosphorus export from a temperate grassland micro-catchment

Willows (Salix SPP.) are increasingly being grown as a source of biomass which can be harnessed for energy production at a commercial scale as one example of a Short Rotation Coppice (SRC) crop. What is less widely understood is the role of the plants in reducing nutrient loads when planted as a nature-based solution to mitigate diffuse pollution from agricultural lands. Strategically planted woodland and forest can play a major role in Nature Based Solutions (NBS) approaches. SRC willows were planted in a 22-ha grassland micro-catchment located on a research farm in Northern Ireland, which is regularly grazed by cattle and sheep. The micro-catchment comprises a small ditch with upstream and downstream monitoring points where a pair of autosamplers were used to collect water samples for nutrient analysis. It was possible to reconstruct a timeseries of hourly discharge in the ungauged micro-catchment using the SHETRAN hydrological model. Subsequently, the modelled flows were used to estimate daily phosphorus (P) loads at both upstream and downstream monitoring points from the measured P concentrations. The nearly four years (June 2018–April 2022) of monitoring data allowed P loads to be calculated for pre-planting, juvenile trees and mature trees phases. A baseline scenario was run without any changes to the model; this evaluated the changes in P loads from the catchment. A further Post-Willows scenario “P–W” modified some model parameters and evapotranspiration to represent the land use change due to the willow plantation. The results from the baseline were evaluated and showed that (i) there was a statistically significant reduction in particulate P (PP) and total P (TP) concentrations at the outlet of the micro-catchment; (ii) a statistically significant reduction in PP and TP loads, indicating that the willows were reducing PP export (losses) probably by trapping fine sediment in the ditch. Results from the P–W scenario showed a smaller than expected decrease in discharge from the model results. The overall export of TP from the micro-catchment could be further decreased by additional planting of SRC willows, but the export of soluble forms of P did not decrease by a significant amount post-planting which is a recommendation for further study in mitigation programmes. The use of SRC willows in riparian buffer strips (RBS) which are a common form of NBS, has shown promising results in terms of trapping particulate forms of P. The layout of the RBS should also be carefully designed in terms of maximising the buffer strip width, here the areas planted was optimised to make best use of unproductive farmland. If the RBS can be designed to maximise the interception of runoff flowing downhill from agricultural fields then the removal rate should be even higher.

The effects of land‐use change on semi‐aquatic bugs (Gerromorpha, Hemiptera) in rainforest streams in Sabah, Malaysia

Abstract Land‐use change and agricultural expansion have caused marked biodiversity loss in Southeast Asia, but impacts on freshwater communities have been very little studied. Semi‐aquatic bugs are abundant in streams, provide prey for many other animals, and are sensitive to environmental change, making them a relevant group for studying land‐use change. We investigated the effects of logging and conversion of forest to oil palm plantations on semi‐aquatic bugs in Sabah, Malaysia, and the potential value of retaining riparian buffer strips in plantations, by sampling across 12 rivers along an existing land‐use gradient. We recorded catchment, riparian, and stream‐scale environmental variables and surveyed semi‐aquatic bugs within streams in old‐growth forest, logged forest, and oil palm plantation with (OPB) and without buffer strips (OP). We recorded the abundance, richness, total biomass, and proportion of juveniles and winged adult individuals of all species, together with the sex ratio of a common morphospecies (Ptilomera sp.), as possible indicators of disturbance effects. Average abundance and average richness, but not total biomass, of all semi‐aquatic bugs were lower in areas with higher habitat disturbance. In particular, average abundance in old‐growth forest was more than two, four, and six times higher than that in logged forest, OPB, and OP, respectively. Average richness in old‐growth forest was higher than in logged forest by two species, but more than two and three times higher than in OPB and OP, respectively. The presence of riparian buffer strips in oil palm had little effect on the abundance and richness of semi‐aquatic bugs. We found no significant differences in the proportion of juveniles, winged adult individuals, or the sex ratio of Ptilomera sp. along the disturbance gradient. In conclusion, oil palm plantations were associated with lower average abundance and richness of semi‐aquatic bugs than forest sites, but community composition did not differ markedly between logged and old‐growth forests. We also found that the forested buffer strips maintained within our oil palm plantation study sites did not protect forest species of semi‐aquatic bugs. Maintaining forest may therefore provide the best option for the conservation of semi‐aquatic bugs, but further studies of the effects of land‐use change and management options are needed across Southeast Asia.

The impacts of within-stream physical structure and riparian buffer strips on semi-aquatic bugs in Southeast Asian oil palm

Despite the diverse ecosystem services that forested stream margins (“riparian buffer strips”) can provide in agricultural landscapes, understanding of their biodiversity impacts in the tropics is lacking. Stream invertebrates support many ecosystem functions and several groups are valuable bioindicators of environmental conditions. Semi-aquatic bugs (insects in Hemiptera that inhabit the water surface) are important within the aquatic food chain, acting as predators of other invertebrates and prey for larger animals. Since they inhabit the water surface, semi-aquatic bugs are potentially valuable indicators of within-stream health. Focusing on the impacts of conditions at the small-scale, we investigated how within-stream physical structure and the presence of riparian buffer strips affected the abundance, total biomass, richness, and community composition of semi-aquatic bugs in oil palm plantations in Sabah, Malaysia. We also assessed the effects on the proportion of juveniles and females of Ptilomera sp. (a common genus). Our focus on the small-scale make findings applicable for management both within smallholder and large-scale plantations. At the small-scale (10-m transect), oil palms streams with riparian buffers contained twice as many semi-aquatic bugs as those without (average richness in streams with buffers 3.55 (SE ± 0.42) compared to 1.40 (SE ± 0.22) in streams without). We found a total of 14 morphospecies in streams with buffers, compared to just seven in those without. There was no difference in total biomass or the proportion of female Ptilomera sp. in streams with or without buffers. There was a significantly higher abundance of semi-aquatic bugs in streams with wider wetted width, more isolated pools, shallower slopes, and lower percentage of deadwood. The proportion of juveniles was higher in streams with higher canopy openness, higher percentage of deadwood, lower percentage of pebbles, and narrower wetted widths. This study demonstrates that small-scale differences in stream conditions within oil palm can influence semi-aquatic bugs, opening up the possibility that oil palm management could be tailored to improve environmental conditions for stream communities. As our findings are based on only a few streams and at measurements collected at a single time-point, more studies are needed to validate what we have found.

Rehabilitation Strategy for Restoration of Riverbank Protection Function in the Merawu Watershed, Banjarnegara Regency

Riverbank is a buffer zone for the river ecosystem and the surrounding land. The significant land use changes and land cover reduction in the Merawu Watershed had put pressure on the riverbank and threatened the protection function sustainability. Thus, this study aims to 1) identify the riverbank’s ecological status, 2) identify its Protection Carrying Capacity (PCC), 3) determine the indicative location of rehabilitation, and 4) develop a rehabilitation strategy for restoring the riverbank protection function. The Riparian Quality Index (RQI) results indicated riverbank ecological degradation and deviation from natural conditions due to intensive tillage. The entire riverbank PCC status was poor due to less land cover in dryland agriculture and mixed dryland agriculture. Three indicative locations of rehabilitation were prioritized, i.e., Karangkobar (54.86 ha), Kalibening (41.21 ha), and Wanayasa Sub-districts (39.31 ha). Recommended riverbank rehabilitation strategies were 1) constructing bunds and bench terraces in sloping land, 2) implementing trees along the border (hedgerow) pattern and riparian buffer strips to increase land cover on cultivated riverbank lands, and 3) constructing gully plugs and retaining dams to strengthen riverbanks; using organic mulch; and planting the recommended species (Falcataria falcata, Artocarpus altilis, Dendrocalamus asper, and Gigantochloa apus) on degraded critical lands.

Projecting the impacts of the bioeconomy on Nordic land use and freshwater quality and quantity – An overview

This paper synthesizes a five-year project (BIOWATER) that assessed the effects of a developing bioeconomy on Nordic freshwaters. We used a catchment perspective and combined several approaches: comparative analyses of long-term data sets from well-monitored catchments (agricultural, with forestry, and near pristine) across Fennoscandia, catchment biogeochemical modelling and ecosystem services assessment for integration. Various mitigation measures were also studied. Benchmark Shared Socio-economic Pathways were downscaled and articulated in dialogue with national stakeholder representatives leading to five Nordic Bioeconomy Pathways (NBPs) describing plausible but different trajectories of societal development towards 2050.These were then used for catchment modelling and ecosystem service assessment. Key findings from the work synthesized here are: (a) The monitoring results from 69 catchments demonstrate that agricultural lands exported an order of magnitude more nutrients than natural catchments (medians 44 vs 4 kg P km−2 y-1 and 1450 vs 139 kg N km−2 y-1) whilst forests were intermediate (7 kg P km−2 y-1 and 200 kg N km−2 y-1). (b) Our contrasting scenarios led to substantial differences in land use patterns, which affected river flow as well as nutrient loads in two of the four modelled catchments (Danish Odense Å and Norwegian Skuterud), but not in two others (Swedish catchment C6 and Finnish Simojoki). (c) Strongly contrasting scenarios (NBP1 maximizing resource circularity versus NBP5 maximizing short-term profit) were found to lead to similar monetary estimates of total societal benefits, though for different underlying reasons – a pattern similar across the six studied Nordic catchments. (d) The ecological status of small to medium sized rivers in agricultural landscapes benefitted greatly from an increase in riparian forest cover from 10 % to 60 %. Riparian buffer strips, constructed wetlands, rewetting of ditched peatlands, and similar nature-based solutions optimize natural biogeochemical processes and thus can help in mitigating negative impacts of intensified biomass removal on water quality.

Evaluating the effectiveness of land use management as a natural flood management intervention in reducing the impact of flooding for an upland catchment

AbstractNatural flood management (NFM) is a method for reducing flooding by using a catchment‐based approach to managing flood risk. Understanding and quantifying the impact of implementing NFM at the catchment scale remains ambiguous with a clear need for robust empirical evidence. A combination of fieldwork, laboratory analysis and modelling was applied to quantify the impacts of land use management changes on catchment flood hazard. Soil hydraulic conductivity was measured under varying land management regimes and used to parameterize a physically based spatially distributed hydrological model (SD‐TOPMODEL). A suite of stakeholder informed land management scenarios was modelled, permitting the quantification of the impact of NFM interventions on the timing and the intensity of the peak discharge at the catchment outlet. The findings support the implementation of NFM interventions as a means of reducing flood hazard within a rural upland catchment. Improved soil infiltration provided the greatest reduction in the intensity and delayed timing of the flood peak for a 10‐year occurrence storm event (7% reduction in peak runoff and 8% increase in lag time) with similar reductions observed for a 100‐year storm event. Catchment wide woodland planting reduced peak flow by 11% during the 100‐year event but was not effective during the 10‐year event. Riparian buffer strips provided consistent reductions in peak flow and in the timing of the peak across both storm events with no significant differences relating to vegetation age. Critically, we observed that the effect of implementing multiple NFM interventions was not additive and that efficiencies can be made in using this modelling approach to prioritize the most effective outcomes.

The Comprehensive Reduction Capacity of Five Riparian Vegetation Buffer Strips for Primary Pollutants in Surface Runoff

Most studies on the effects of plants on reducing pollutants in surface runoff focus on the elimination of a single pollutant by a single plant species. We take into account the fact that natural riparian herbaceous vegetation buffer strips remove multiple pollutants at the same time, and vegetation species need to be selected according to actual conditions. In an indoor simulation, processed soil samples were taken, and collected rainwater was used to prepare standard solutions for simulating surface runoff, which includes five primary water pollutants: total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH3-N), and chemical oxygen demand (COD). Pollutant concentrations were measured after the experiments. We found that the reduction capacity of vegetation buffer strips differs due to the differentiation of biological structure and growth characteristics. Dichondra repens Forst and Cynodon dactylon (Linn.) Pers had high biomass, and their vegetation was creeping on the ground with well-developed roots, showing a strong comprehensive ability to reduce pollutants. The comprehensive reduction capability of five vegetation buffer strips for pollutants is ranked as follows: Dichondra repens Forst > Cynodon dactylon (Linn.) Pers > Zoysia matrella > Festuca elata Keng ex E. Alexeev > Lolium perenne.

Production pathways for profitability and valuing ecosystem services for willow coppice in intensive agricultural applications

Increasing agricultural sustainability is a key challenge facing the globe today. Energy crops, planted as riparian buffers are one way to support this, simultaneously mitigating water quality degradation and climate change. However, the economics of implementing such riparian buffer systems is under researched. Hence this work conducted a bottom-up economic analysis of willow coppice riparian buffers on a Northern Irish dairy farm, which is indicative of agricultural intensification across Europe. This work includes an economic assessment of a willow coppice riparian buffer strip, using harvested yield data from an established willow buffer site for the first time. It also considered the impact of harvesting technology on the economic performance of a willow coppice riparian buffer strip for the first time. The analysis considered three willow production pathways: 1) direct chip harvesting, 2) full-stem harvesting, and 3) a scenario with a guaranteed purchasing contract for fresh chip. Economic performance was considered using net present value over a 25-year plantation lifetime. The full-stem scenario provided the highest economic return over its lifetime with an average yearly net present value of £497 ha−1 (in £ sterling). This system was then considered for integration into a typical dairy farm, assuming 5 % land usage and including government grants for establishing riparian zones. The result was a drop in value of £28 ha−1 yr−1 compared to a dairy-only scenario; however, per litre of milk the farm employing willow coppice riparian buffer strips outperformed a typical dairy farm both environmentally and economically. Further analysis considered a novel approach that included payments for ecosystem services in the economic analysis. This analysis found that the implementation of government payments for ecosystem services (nutrient removal) increased the economic return of the willow coppice riparian buffer system by £400 ha−1 yr−1, resulting in minimal impact on the return from dairy land.

Impacts of different vegetation in riparian buffer strips on runoff and sediment loss.

Buffer strips continue to feature in the management of agricultural runoff and water pollution in many countries. Existing research has explored their efficacy for reducing environmental problems in different geoclimatic settings but, the evidence on the efficacy of different vegetation treatments is less abundant than that for other buffer strip characteristics, including width, and is more contradictory in nature. With policy targets for various environmental outcomes including water or air quality and net zero pointing to the need for conversion of agricultural land, the need for robust experimental evidence on the relative benefits of different vegetation types in buffer strips is now renewed. Our experiment used a replicated plot scale facility to compare the efficacy of 12 m wide buffer strips for controlling runoff and suspended sediment loss during 15 sampled storms spanning 2017-2020. The buffer strips comprised three vegetation treatments: a deep rooting grass (Festulolium cv. Prior), a short rotation coppice willow and native broadleaved woodland trees. Over the duration of the monitoring period, reductions in total runoff, compared with the experimental control, were in the order: willow buffer strips (49%); deciduous woodland buffer strips (46%); grass buffer strips (33%). The corresponding reductions in suspended sediment loss, relative to the experimental control, were ordered: willow buffer strips (44%) > deciduous woodland buffer strips (30%) > grass buffer strips (29%). Given the 3-year duration of our new dataset, our results should be seen as providing evidence on the impacts during the establishment phase of the treatments.

Analisis Pengaruh Limbah Domestik terhadap Kualitas Air Anak Sungai Asam

The Asam River is one of the tributaries located along the RT 15 area of Paal V Village, the Asam River crossing the residential area of this river has the potential to be polluted by domestic waste. Based on data on the water quality of the Asam River according to the Jambi City Environmental Service in 2020, the water quality of the Asam River has exceeded the surface water quality standard on the parameters of TSS, turbidity, pH, BOD, COD and ammonia. The purpose of the study was to determine the disposal of domestic wastewater and to determine the quality status of the acid river in terms of the pollution index method and to know the plan for controlling the pollution of the acid river with the influence of domestic waste. Based on the calculation of the status of the Asam River water quality, which was determined using the Pollution Index (IP) method, the points AP-1 (Upstream) and AP-2 (Downstream) were in a “Lightly Polluted” condition. This is because the results of the ammonia and turbidity parameter tests at the AP-1 (Upstream) and AP-2 (Downstream) points that exceed the established quality standards. Efforts to control river pollution can be carried out by making riparian buffer strips or planting vegetation on the banks of the Asam River. , the manufacture of communal WWTPs in every existing sub-district along the Asam River and tightening of wastewater quality standards for industrial and domestic activities which must not exceed the water quality standard according to its class.

First delimitation and land-use assessment of the riparian zones at Uruguayan Pampa

The expansion and intensification of agriculture frequently affect riparian zones, mainly in basins where agriculture is the most important activity. In countries with basins dominated by agricultural activities, land use change in riparian zones promotes water quality loss and biodiversity degradation. As a tool to prevent these environmental impacts, the delimitation of riparian zones and buffer strips is crucial. For that purpose, photo interpretation jobs and botanical studies are usually necessary. However, a digital terrain model (DTM) becomes the best alternative when the information is unavailable or the survey area is too large. This work made the first delimitation of riparian zones of the country's water drainage network. The results obtained by using a 1-m vertical buffer in DTM allowed the delimitation of the riparian zones of Uruguay. The results indicate that of the areas identified as riparian, 62% would be authentic and that the 29% of riparian areas identified under cultivation could rise to 46% if the identification improved the identification accuracy. The results indicate the existence of 4,608,890 ha of riparian zones, of which 94,651 ha could be under cultivation.

Soil CO2 emissions in cropland with fodder maize (Zea mays L.) with and without riparian buffer strips of differing vegetation

Vegetated land areas play a significant role in determining the fate of carbon (C) in the global C cycle. Riparian buffer vegetation is primarily implemented for water quality purposes as they attenuate pollutants from immediately adjacent croplands before reaching freashwater systems. However, their prevailing conditions may sometimes promote the production and subsequent emissions of soil carbon dioxide (CO2). Despite this, the understanding of soil CO2 emissions from riparian buffer vegetation and a direct comparison with adjacent croplands they serve remain elusive. In order to quantify the extent of CO2 emissions in such an agro system, we measured CO2 emissions simultaneously with soil and environmental variables for six months in a replicated plot-scale facility comprising of maize cropping served by three vegetated riparian buffers, namely: (i) a novel grass riparian buffer; (ii) a willow riparian buffer, and; (iii) a woodland riparian buffer. These buffered treatments were compared with a no-buffer control. The woodland (322.9 ± 3.1 kg ha− 1) and grass (285 ± 2.7 kg ha− 1) riparian buffer treatments (not significant to each other) generated significantly (p = < 0.0001) the largest CO2 compared to the remainder of the treatments. Our results suggest that during maize production in general, the woodland and grass riparian buffers serving a maize crop pose a CO2 threat. The results of the current study point to the need to consider the benefits for gaseous emissions of mitigation measures conventionally implemented for improving the sustainability of water resources.

Riparian buffer strips influence nitrogen losses as nitrous oxide and leached N from upslope permanent pasture

Riparian buffer strips can have a significant role in reducing nitrogen (N) transfers from agricultural land to freshwater primarily via denitrification and plant uptake processes, but an unintended trade-off can be elevated nitrous oxide (N2O) production rates. Against this context, our replicated bounded plot scale study investigated N2O emissions from un-grazed ryegrass pasture served by three types of riparian buffer strips with different vegetation, comprising: (i) grass riparian buffer with novel deep-rooting species, (ii) willow (young trees at establishment phase) riparian buffer, and (iii) deciduous woodland (also young trees at establishment phase) riparian buffer. The experimental control was ryegrass pasture with no buffer strip. N2O emissions were measured at the same time as total oxidized N in run-off, and soil and environmental characteristics in the riparian buffer strips and upslope pasture between 2018 and 2019. During most of the sampling days, the no-buffer control treatment showed significantly (P < 0.05) greater N2O fluxes and cumulative N2O emissions compared to the remainder of the treatments. Our results also showed that the grass riparian buffer strip is a sink of N2O equivalent to − 2310.2 g N2O-N ha−1 day−1 (95% confidence interval:−535.5 to 492). Event-based water quality results obtained during storms (12 November 2018 and 11 February 2019) showed that the willow riparian buffer treatment had the highest flow-weighted mean N concentrations (N-FWMC) of 0.041 ± 0.022 and 0.031 ± 0.015 mg N L−1, when compared to the other treatments. Our 9-month experiment therefore, shows that riparian buffer strips with novel deep-rooting grass can therefore potentially address emissions to both water and air. The results imply that over a shorter timeline similar to the current study, the grass riparian buffer strip can potentially address N emission to both air and water, particularly when serving a permanent pasture in similar settings as the current experiment.

Root architecture characteristics of five natural homogeneous grasslands in riparian buffers from lower reaches of Yellow River

AbstractRoot system characteristics are of fundamental importance to soil improvement and underground resource acquisition in riparian buffer strips. Root architectural traits determine the in situ space‐filling properties of a root system. The aims of this study were to examine the grassland root morphological characteristics in the vegetation zone from the lower reaches of Yellow River. Five natural homogeneous grasslands including Imperata cylindrica, Phragmites australis, Cynodon dactylon, Artemisia argyi and Juncellus serotinus were selected. Seven root architecture parameters including fractal dimension, total root length, total root surface area, total root volume, average diameter, root crossing number and root tip number were analyzed, and comprehensive scores were evaluated using principal component analysis. The results showed that average root diameter of the five herbaceous plants was ranged from 0.42 to 0.78 mm. The total root length, total root surface area, total root volume, root crossing number and root tip number of I. cylindrica and P. australis were significantly higher than those of C. dactylon, A. argyi and J. serotinus. The main factors influencing root architecture were average diameter, total root surface area and total root volume through principal component analysis. I. cylindrica had the highest comprehensive score, followed by P. australis, A. argyi, C. dactylon and J. serotinus. I. cylindrica and P. australis would be good competitors for both soil resource acquisition and soil quality improvement due to their root traits. These results could provide a scientific basis for evaluating the ecological function of riparian vegetation.

Soil N2O and CH4 emissions from fodder maize production with and without riparian buffer strips of differing vegetation

PurposeNitrous oxide (N2O) and methane (CH4) are some of the most important greenhouse gases in the atmosphere of the 21st century. Vegetated riparian buffers are primarily implemented for their water quality functions in agroecosystems. Their location in agricultural landscapes allows them to intercept and process pollutants from adjacent agricultural land. They recycle organic matter, which increases soil carbon (C), intercept nitrogen (N)-rich runoff from adjacent croplands, and are seasonally anoxic. Thus processes producing environmentally harmful gases including N2O and CH4 are promoted. Against this context, the study quantified atmospheric losses between a cropland and vegetated riparian buffers that serve it.MethodsEnvironmental variables and simultaneous N2O and CH4 emissions were measured for a 6-month period in a replicated plot-scale facility comprising maize (Zea mays L.). A static chamber was used to measure gas emissions. The cropping was served by three vegetated riparian buffers, namely: (i) grass riparian buffer; (ii) willow riparian buffer and; (iii) woodland riparian buffer, which were compared with a no-buffer control.ResultsThe no-buffer control generated the largest cumulative N2O emissions of 18.9 kg ha− 1 (95% confidence interval: 0.5–63.6) whilst the maize crop upslope generated the largest cumulative CH4 emissions (5.1 ± 0.88 kg ha− 1). Soil N2O and CH4-based global warming potential (GWP) were lower in the willow (1223.5 ± 362.0 and 134.7 ± 74.0 kg CO2-eq. ha− 1 year− 1, respectively) and woodland (1771.3 ± 800.5 and 3.4 ± 35.9 kg CO2-eq. ha− 1 year− 1, respectively) riparian buffers.ConclusionsOur results suggest that in maize production and where no riparian buffer vegetation is introduced for water quality purposes (no buffer control), atmospheric CH4 and N2O concerns may result.

Assessing the source and delivery processes of organic carbon within a mixed land use catchment using a combined n-alkane and carbon loss modelling approach

PurposeUnderstanding fluxes of soil organic carbon (OC) from the terrestrial to aquatic environments is crucial to evaluate their importance within the global carbon cycle. Sediment fingerprinting (SF) is increasingly used to identify land use-specific sources of OC, and, while this approach estimates the relative contribution of different sources to OC load in waterways, the high degree of spatial heterogeneity in many river catchments makes it challenging to precisely align the source apportionment results to the landscape. In this study, we integrate OC SF source apportionment with a carbon loss model (CLM) with the aim of: (i) reducing ambiguity in apportioning OC fluxes when the same land use exists in multiple locations within a catchment; and (ii) identifying factors affecting OC delivery to streams, e.g., buffer zones.MethodsTwo main approaches were used in this study: (i) identification of the sources of freshwater bed sediment OC using n-alkane biomarkers and a Bayesian-based unmixing model; and (ii) modelling and analysis of spatial data to construct a CLM using a combination of soil OC content modelling, RUSLE soil erosion modelling and a connectivity index. The study was carried out using existing OC and n-alkane biomarker data from a mixed land use UK catchment.ResultsSediment fingerprinting revealed that woodland was the dominant source of the OC found in the streambed fine sediment, contributing between 81 and 85% at each streambed site. In contrast, CLM predicted that arable land was likely the dominant source of OC, with negligible inputs from woodland. The areas of the greatest OC loss in the CLM were predicted to be from arable land on steeper slopes surrounding the stream channels. Results suggest extensive riparian woodland disconnected upslope eroded soil OC and, concomitantly, provided an input of woodland-derived OC to the streams. It is likely the woodland contribution to streambed OC is derived from litter and leaves rather than soil erosion.ConclusionThis study demonstrates how location-specific OC sources and delivery processes can be better determined using sediment fingerprinting in combination with CLM, rather than using sediment fingerprinting alone. It highlights that, although wooded riparian buffer strips may reduce the impact of upslope, eroded soil OC on waterways, they could themselves be a source of OC to stream sediments through more direct input (e.g., organic litter or leaf debris). Characterising this direct woodland OC as a separate source within future fingerprinting studies would allow the contributions from any eroded woodland soil OC to be better estimated.

Phosphate oxygen isotope ratios in vegetated riparian buffer strip soils

AbstractThe oxygen isotopic composition of phosphate (δ18OP) in soils and surface water bodies has been used to trace terrestrial P inputs into aquatic ecosystems. However, enhanced biological activity in vegetated riparian buffer strips (VBSs) may lead to an alteration of δ18OP values. The objective of this study was to assess whether enhanced biological cycling of P in VBS soils can be identified using δ18OP values. For this purpose, we sampled temperate grassland soils at various depths along a VBS to grassland transect. Here, we combined sequential P soil extracts with an analysis of δ18OP values. Soil P pool concentrations tended to decrease significantly along the transect from the VBS to the grassland soils; the strength of this relationship varied with P extract, sample depth, and inorganic or organic bonding form. For the δ18OP values of the 1 M HCl‐extractable P we observed a significant negative trend along the VBS to grassland transect, indicating a tendency for accelerated rates of biological cycling of P within the VBS soil profile compared with the upslope soils. We conclude that oxygen isotope‐based assessments of P source contributions to freshwater bodies should consider the enhanced biological turnover of P in VBS soils.