Nitrogen-fixing Plants Research Articles

Pre-Treatment Effect on Seed Germination of <i>Calopogonium mucunoide</i>s: A Promising Cover Crop for Land Restoration

Calopogonium mucunoides has been widely used as a pasture legume, cover crop and nitrogen fixing plant in tropical regions of the world. The present study investigated the effect of different pre-treatments on germination per cent (GP), mean germination time (MGT), germination value (GV), peak value (PV) and germination index (GI) of C. mucunoides. Experiment was conducted in Complete Randomized Design with four replications of 25 seeds for each treatment and control (25 seeds × 4 replicates × control/hot water/acid scarification/sand scarification/growth promoters = 52 experimental units). Seeds were subjected to different pretreatments viz., Hot water soaking at 40°C, 60°C, 80°C, 88°C; acid scarification using conc. H 2 SO 4 98% (1% (v/v), 3% (v/v), 5% (v/v); sand scarification, GA 3 treatment (500ppm and 1000ppm); KNO 3 treatment 0.1% (w/v), 1% (w/v), 3% (w/v). Results of germination parameters such as GP, MGT and GV were subjected to analysis of variance (ANOVA). Dunnett t (2-sided) statistical analysis and Post hoc Tukey HSD method was used for testing the significance between treatments. Results concluded that control seed produce the GP of 56% while sand scarification and hot water soaking of seeds enhanced the GP range from 80-97%.

CH4 and N2O Emissions From Cattle Excreta: A Review of Main Drivers and Mitigation Strategies in Grazing Systems

Cattle production systems are an important source of greenhouse gases (GHG) emitted to the atmosphere. Animal manure and managed soils are the most important sources of emissions from livestock after enteric methane. It is estimated that the N2O and CH4 produced in grasslands and manure management systems can contribute up to 25% of the emissions generated at the farm level, and therefore it is important to identify strategies to reduce the fluxes of these gases, especially in grazing systems where mitigation strategies have received less attention. This review describes the main factors that affect the emission of GHG from manure in bovine systems and the main strategies for their mitigation with emphasis on grazing production systems. The emissions of N2O and CH4 are highly variable and depend on multiple factors, which makes it difficult to use strategies that mitigate both gases simultaneously. We found that strategies such as the optimization of the diet, the implementation of silvopastoral systems and other practices with the capacity to improve soil quality and cover, and the use of nitrogen fixing plants are among the practices with more potential to reduce emissions from manure and at the same time contribute to increase carbon capture and improve food production. These strategies can be implemented to reduce the emissions of both gases and, depending on the method used and the production system, the reductions can reach up to 50% of CH4 or N2O emissions from manure according to different studies. However, many research gaps should be addressed in order to obtain such reductions at a larger scale.

Invasive nitrogen-fixing plants increase nitrogen availability and cycling rates in a montane tropical grassland

Invasive nitrogen-fixing plants increase nitrogen availability and cycling rates in a montane tropical grassland

Post-mine succession and short term effects of coal mining in a Guinea savanna ecosystem

This research aimed to determine the impact of coal mining on the variety of plants and their successional dynamism in the Guinea savanna. Five sites in Nasarawa State, Nigeria, were sampled: abandoned sites (36 years post-mining), actively mined sites C and D (for two years), and one control site, E. To evaluate its diversity and species composition, alpha diversity (species richness, Shannon and Simpson diversity indices), beta diversity, and indicator species studies were employed. There were 74 plant species observed throughout the study, but 55 showed a significant connection with the locations. Control site E contained the most significant proportion of native, perennial, and nitrogen-fixing plants, indicating a high level of alpha diversity. Due to the high OC and accessible N at abandoned site A, it possesses the most significant number of tree species (75%) in the Fabaceae family, indicating ongoing natural succession. Thus, succession in abandoned site A was created based on the microhabitat's interaction with the plant species' eco-functionality. Although extrinsic factors such as grazing and farming delayed successional processes in abandoned site B, the greatest observed beta diversity was linked with the eco-morphological characteristics of rare plant species Boerhavia erecta and Kallstroemia pubescens. Active mining sites C and D had reduced soil nutrients and a greater abundance of invasive annual forb species such as Ageratum conyzoides, Asystasia gangetica, Urena lobata, Sida linifolia, and Mimosa pudica. Therefore, artificial restoration of abandoned coal site B is recommended to expedite the reclamation process.

Light, nitrogen supply, and neighboring plants dictate costs and benefits of nitrogen fixation for seedlings of a tropical nitrogen-fixing tree.

The ability to fix nitrogen may confer a competitive advantage or disadvantage to symbiotic nitrogen-fixing plants depending on the availability of soil nitrogen and energy to fuel fixation. Understanding these costs and benefits of nitrogen fixation is critical to predicting ecosystem dynamics and nutrient cycling. We grew inoculated (with symbiotic bacteria) and uninoculated seedlings of Pentaclethra macroloba (a nitrogen-fixing tree species) both in isolation and with Virola koschnyi (a nonfixing species) under gradients of light and soil nitrogen to assess how the ability to fix nitrogen and fixation activity affect growth, biomass allocation, and responses to neighboring plants. Inoculation itself did not provide a growth advantage to nitrogen fixers, regardless of nitrogen limitation status. Higher nitrogen fixation rates increased biomass growth similarly for nitrogen-limited and nitrogen-saturated fixers. Nodule production was offset by reduced fine-root biomass for inoculated nitrogen fixers, resulting in no change in total belowground allocation associated with nitrogen fixation. Under nitrogen-limited conditions, inoculated nitrogen fixers partially downregulated fixation in the presence of a nonfixing neighbor. These results suggest that nitrogen fixation can provide a growth advantage, even under nitrogen-saturated conditions, and that nitrogen fixers may reduce fixation rates to minimize facilitation of neighbors.

Soil characteristics and microbial community response in rare earth mining areas in southern Jiangxi Province, China.

The microbial community and functional flora in rare earth mining areas are correlated, but the characteristics and metabolic pathways of pollutant in such mining areas are still poorly known. The heavy metals, rare earth elements, and microorganisms present after mining of rare earth mine sites were analyzed. After mining, all sampling sites exhibited low pH and low total organic carbon levels, accompanied by high iron and aluminum concentrations. The development of vegetation is closely related to the development of microorganisms. In the complex environment of rare earth mining areas, Proteobacteria exhibit an absolute competitive advantage. During mine environmental recovery, the relative abundances of Acidobacteria and Chloroflexi will increase markedly, and with further restoration the relative abundance of Firmicutes will gradually decrease. Many genera of bacteria related to the N cycle and heavy metal metabolism were detected in the study area, indicating the important metabolic pathways for ammonia nitrogen and heavy metals in rare earth mining areas. Bacterial genera that promote plant nitrogen fixation also occur in the area, further revealing the nitrogen cycle. This research is important for health assessment and recovery of rare earth mines.

Biodiversity effects on grape quality depend on variety and management intensity.

Interactions between plants can be beneficial, detrimental or neutral. In agricultural systems, competition between crop and spontaneous vegetation is a major concern. We evaluated the relative support for three non‐exclusive ecological hypotheses about interactions between crop and spontaneous plants based on competition, complementarity or facilitation.The study was conducted in Swiss vineyards with different vegetation management intensities. In all, 33 vineyards planted with two different grape varieties were studied over 3 years to determine whether low‐intensity vegetation management might provide benefits for grape quality parameters. Management intensity varied with the degree of control of spontaneous inter‐row vegetation. Features of spontaneous vegetation measured included total cover, total species richness and abundance of nitrogen‐fixing plants. Grape quality parameters of known importance to wine making (yeast assimilable nitrogen, sugars, tartaric acid and malic acid) were determined by Fourier‐transform infrared spectroscopy (FTIR). Using structural equation modelling, we evaluated hypotheses about the multivariate responses of grape quality parameters as well as the direct and indirect (plant‐mediated) effects of management.Observed effects of management differed between grape varieties. Management intensity and abundance of N‐fixing plants significantly influenced grape quality parameters while total richness of spontaneous plants did not have detectable effects. Abundance of N‐fixing plants was enhanced by low‐intensity management resulting in increased N content in the red grape variety Pinot noir, potentially enhancing grape quality, while measured soil N content did not explain the increase.Synthesis and applications. Our study shows that crop quality can be enhanced by spontaneous plants, in this case by the abundance of a key functional group (N‐fixers), most likely through plant–plant or plant–microbe facilitation. However, beneficial interactions may have a high specificity in terms of facilitation partners and may have contrasting effects at low taxonomic resolutions such as crop varieties. Generally, increasing plant biodiversity in agricultural systems may increase competition with crops. Thus, the identification of suitable interaction partners and a careful balance between crop variety and spontaneous plant species may be necessary to utilize beneficial interactions and to reduce the trade‐off between agricultural production and biodiversity to achieve a sustainable ecological benefit in agricultural systems.

The Interactive Effect of Elevated CO2 and Herbivores on the Nitrogen-Fixing Plant Alnus incana ssp. rugosa.

Many studies have found that future predicted CO2 levels can increase plant mass but dilute N content in leaves, impacting antiherbivore compounds. Nitrogen-fixing plants may balance their leaf C:N ratio under elevated CO2, counteracting this dilution effect. However, we know little of how plants respond to herbivores at the higher CO2 levels that occurred when nitrogen-fixing plants first evolved. We grew Alnus incana ssp. rugosa was grown at 400, 800, or 1600 ppm CO2 in soil collected from the field, inoculated with Frankia and exposed to herbivores (Orgyia leucostigma). Elevated CO2 increased nodulated plant biomass and stimulated the nitrogen fixation rate in the early growth stage. However, nitrogen-fixing plants were not able to balance their C:N ratio under elevated CO2 after growing for 19 weeks. When plants were grown at 400 and 1600 ppm CO2, herbivores preferred to feed on leaves of nodulated plants. At 800 ppm CO2, nodulated plants accumulated more total phenolic compounds in response to herbivore damage than plants in the non-Frankia and non-herbivore treatments. Our results suggest that plant leaf defence, not leaf nutritional content, is the dominant driver of herbivory and nitrogen-fixing plants have limited ability to balance C:N ratios at elevated CO2 in natural soil.

Pangenomics of the Symbiotic Rhizobiales. Core and Accessory Functions Across a Group Endowed with High Levels of Genomic Plasticity.

Pangenome analyses reveal major clues on evolutionary instances and critical genome core conservation. The order Rhizobiales encompasses several families with rather disparate ecological attitudes. Among them, Rhizobiaceae, Bradyrhizobiaceae, Phyllobacteriacreae and Xanthobacteriaceae, include members proficient in mutualistic symbioses with plants based on the bacterial conversion of N2 into ammonia (nitrogen-fixation). The pangenome of 12 nitrogen-fixing plant symbionts of the Rhizobiales was analyzed yielding total 37,364 loci, with a core genome constituting 700 genes. The percentage of core genes averaged 10.2% over single genomes, and between 5% to 7% were found to be plasmid-associated. The comparison between a representative reference genome and the core genome subset, showed the core genome highly enriched in genes for macromolecule metabolism, ribosomal constituents and overall translation machinery, while membrane/periplasm-associated genes, and transport domains resulted under-represented. The analysis of protein functions revealed that between 1.7% and 4.9% of core proteins could putatively have different functions.

Compatible Mycorrhizal Types Contribute to a Better Design for Mixed Eucalyptus Plantations.

Mixed-species forest plantation is a sound option to facilitate ecological restoration, plant diversity and ecosystem functions. Compatible species combinations are conducive to reconstruct plant communities that can persist at a low cost without further management and even develop into natural forest communities. However, our understanding of how the compatibility of mycorrhizal types mediates species coexistence is still limited, especially in a novel agroforestry system. Here, we assessed the effects of mycorrhizal association type on the survival and growth of native woody species in mixed-species Eucalyptus plantations. To uncover how mycorrhizal type regulates plant-soil feedbacks, we first conducted a pot experiments by treating distinct mycorrhizal plants with soil microbes from their own or other mycorrhizal types. We then compared the growth response of arbuscular mycorrhizal plants and ectomycorrhizal plants to different soil microbial compositions associated with Eucalyptus plants. We found that the type of mycorrhizal association had a significant impact on the survival and growth of native tree species in the Eucalyptus plantations. The strength and direction of the plant-soil feedbacks of focal tree species depended on mycorrhizal type. Non-mycorrhizal plants had consistent negative feedbacks with the highest survival in the Eucalyptus plantations, whereas nitrogen-fixing plants had consistent positive feedbacks and the lowest survival. Arbuscular mycorrhizal and ectomycorrhizal plants performed varied feedback responses to soil microbes from distinct mycorrhizal plant species. Non-mycorrhizal plants grew better with Eucalyptus soil microbes while nitrogen-fixing plants grew worse with their own conspecific soil microbes. Different soil microbial compositions of Eucalyptus consistently increased the aboveground growth of arbuscular mycorrhizal plants, but the non-mycorrhizal microbial composition of the Eucalyptus soil resulted in greater belowground growth of ectomycorrhizal plants. Overall, Eucalyptus plants induced an unfavorable soil community, impeding coexistence with other mycorrhizal plants. Our study provides consistent observational and experimental evidence that mycorrhizal-mediated plant-microbial feedback on species coexistence among woody species. These findings are with important implications to optimize the species combinations for better design of mixed forest plantations.

Ancient CO2 levels favor nitrogen fixing plants over a broader range of soil N compared to present

Small inreases in CO2 stimulate nitrogen fixation and plant growth. Increasing soil N can inhibit nitrogen fixation. However, no studies to date have tested how nitrogen fixing plants perform under ancient CO2 levels (100 MYA), when nitrogen fixing plants evolved, with different levels of N additions. The aim of this study was to assess if ancient CO2, compared to present, favors nitrogen fixers over a range of soil nitrogen concentrations. Nitrogen fixers (Alnus incana ssp. rugosa, Alnus viridis ssp. crispa, and Alnus rubra) and their close non-nitrogen fixing relatives (Betula pumila, Betula papyrifera, Betula glandulosa) were grown at ancient (1600 ppm) or present (400 ppm) CO2 over a range of soil N levels, equivalent to 0, 10, 50, and 200 kg N ha−1 year−1. The growth of non-N fixing plants increased more than N fixing plants in response to the increasing N levels. When grown at an ancient CO2 level, the N level at which non-nitrogen fixing plant biomass exceeded nitrogen fixing plant biomass was twice as high (61 kg N ha−1 year−1) as the N level when plants were grown at the ambient CO2 level. Specific nodule activity was also reduced with an increasing level of soil N. Our results show there was a greater advantage in being a nitrogen fixer under ancient levels of CO2 compared with the present CO2 level.

Perspectives on the utilization of Azolla-Anabaena system as feed supplement

The nitrogen fixing aquatic pteridophyte Azolla is one of the fastest growing nitrogen-fixing plants and it is used as a potential source for high rate biomass production. Azolla has the ability to fix atmospheric nitrogen at cheaper and faster rates due to the presence of a symbiotic cyanobacterium Anabaena azollae. Therefore, the ability to fix atmospheric nitrogen is important from an agricultural perspective. However, Azolla is gaining popularity as feed supplement for cattle, poultry and fish. Further, the ease of cultivation and favourable nutrient composition make Azolla an important feed supplement. This review focuses on the perspectives of Azolla as feed supplement.

Mechanism and application of Sesbania root-nodulating bacteria: an alternative for chemical fertilizers and sustainable development.

Chemical fertilizers are used in large-scale throughout the globe to satisfy the food and feed requirement of the world. Demanding cropping with the enhanced application of chemical fertilizers, linked with a decline in the recycling of natural or other waste materials, has led to a decrease in the organic carbon levels in soils, impaired soil physical properties and shrinking soil microbial biodiversity. Sustenance and improvement of soil fertility are fundamental for comprehensive food security and ecological sustainability. To feed the large-scale growing population, the role of biofertilizers and their study tends to be an essential aspect globally. In this review, we have emphasized the nitrogen-fixing plants of Sesbania species. It is a plant that is able to accumulate nitrogen-rich biomass and used as a green manure, which help in soil amelioration. Problems of soil infertility due to salinity, alkalinity and waterlogging could be alleviated through the use of biologically fixed nitrogen by Sesbania plants leading to the conversion of futile land into a fertile one. A group of plant growth-promoting rhizobacteria termed as "rhizobia" are able to nodulate a variety of legumes including Sesbania. The host-specific rhizobial strains can be used as potential alternative for nitrogenous fertilizers as they help the host plant in growth and development and enhance their endurance under stressed conditions. The review gives the depth understanding of how the agriculturally important microorganisms can be used for the reduction of broad-scale application of chemical fertilizers with special attention to Sesbania-nodulating rhizobia.

Simple Feasibility Analysis Of Nitrogen-Fixing Cereals Project

<p>Nitrogen does not directly have advantages in human physiology system, but it holds one of the most critical roles in plants’ life cycle and productivity. Even though Nitrogen is the most abundant elements in the atmosphere, it is also the most deficient essential nutrients in plants. The proposed idea of the nitrogen-fixing GM crops, particularly wheat, is aimed to overcome those stated cons of the traditional diculture and nitrogen fertilizer. This analysis focus on the overview as well as the pro and cons of the genetically modified nitrogen-fixing plants in providing a better agricultural method. The genetically modifying method to generate a nitrogen-fixing non-legumes carries a significant chance of failure results and hindrance. The multilevel implication occurs when we need to modify the plants that not normally produce nodules in their roots to form the nodules and to modify the Nitrogen-fixing microbes to live in the nodules of non-legumes, which are not their natural dwelling places.</p><p>In conclusion, the genetically modified crops project to fix their Nitrogen is feasible, but the difficulties and the funds needed still outweigh the benefits obtained in the future. With all of those limitations, the target goal to erase famine in 2050 just by funding the nitrogen-fixing wheat alone seems to be too high to be reached. The funds and efforts should be better spent on other factors and farming methods.</p>

Response of ecological stoichiometry and stoichiometric homeostasis in the plant-litter-soil system to re-vegetation type in arid mining subsidence areas

Mining restoration is a key in ecological sustainable development. Ecological stoichiometry and homeostasis in the plant-litter-soil system remain largely unknown but are vital for developing guidelines for vegetation restoration in mining subsidence areas in arid northwest China. Six re-vegetation types comprising stands of Amorpha fruticosa, Hippophae rhamnoides, Xanthoceras sorbifolium, Cerasus humilis, Cerasus szechuanica and Pinus sylvestris were selected for study. We investigated changes in the contents and stoichiometry of C, N and P in roots, stems, leaves, litter and soil in order to understand stoichiometric homeostasis and the factors driving nutrient cycling. The stoichiometry of the plant-soil system varied markedly with different re-vegetation types. The coupling of plant and soil N:P ratios indicates that the concentrations of C, N and P are usually equilibrated. Leave N:P ratios in all re-vegetation types studies indicate that plant growth was N-limited. 1/H only in H. rhamnoides and A. fruticosa (nitrogen-fixing plants) was simultaneously categorized as 'homeostatic' and this might mitigate the N-limitation. Soil easily-extractable glomalin, hyphal density and available phosphorus were key factors shifting the ecological stoichiometry. The study demonstrates that nitrogen-fixing re-vegetation species can promote stoichiometric homeostasis and the results contribute to guidance for vegetation restoration practices in mining subsidence areas.

Invasive legume affects species and functional composition of mountain meadow plant communities

Plant invasions are among the key drivers of global biodiversity and ecosystem change. They often cause reductions in native species richness and overall biodiversity. Nitrogen-fixing plants are problematic as they affect soil nutrient availability and outcompete species of nutrient-poor sites. Here we assessed the impacts of the legume Lupinus polyphyllus on species and functional diversity of mountain meadow communities in the UNESCO Biosphere Reserve Rhön. We compared species diversity (richness, evenness and effective species number), functional diversity (functional richness, evenness, divergence and dispersion) and similarity of plots in three characteristic vegetation types (Nardus grassland, mesic and wet mountain hay meadows) between different lupine cover classes. We calculated community weighted means (CWMs) of single plant traits and plotted them against lupine cover classes. The invasion of L. polyphyllus homogenizes vegetation composition since the similarity among plots of the different vegetation types increased with increasing lupine cover. It significantly affected species diversity in terms of richness and effective species number and the functional divergence of the vegetation. The trait set of species occurring together with lupine was shifted towards more competitive trait values. We demonstrate strongly negative impacts of L. polyphyllus on different mountain meadow vegetation types since L. polyphyllus, fosters the growth of competitive species and leads to overall more productive plant communities.

Short rotation coppice of leguminous tree Leucaena spp. improves soil fertility while producing high biomass yields in Mediterranean environment

The use of woody nitrogen-fixing plant species as multipurpose and energy crops aims to enhance biomass yield while improving soil properties. Yet, the effectiveness of this option is still under debate especially the use of short rotation cropping in water and nutrient limited environments. This study investigated whether short rotation coppicing of four taxa of multipurpose biomass woody legume Leucaena spp. can improve soil conditions when grown for biomass under a Mediterranean environment. Biomass yield, mineral composition and heat value of the biomass and the mineral and organic matter content of soil were evaluated. Under favorable growing conditions, woody dry biomass production was up to 29 Mg ha−1 year−1 with slight but significant differences between the four taxa that were tested. After 11 years of cropping, the soil showed higher fertility and microbial activity compared to the uncropped plot. Leucaena cultivation increased soil nitrogen by 35 %, dehydrogenase activity by 98 %, and organic matter and carbon content (by 41 %). Annual cuttings resulted in the highest biomass production, followed by two and three year cuttings. The mineral composition and the calorific capacity of woody biomass make it suitable for commercial use as an energy source (generating on average 151 MW h ha-1 year-1). In conclusion, short rotation coppicing of nitrogen-fixing woody species results in high biomass production rates with the restoration of degraded soils, constituting a sustainable agroforestry system for rural areas.

Aphid infestation differently affects the defences of nitrate-fed and nitrogen-fixing Medicago truncatula and alters symbiotic nitrogen fixation.

Legumes can meet their nitrogen requirements through root nodule symbiosis, which could also trigger plant systemic resistance against pests. The pea aphid Acyrthosiphon pisum, a legume pest, can harbour different facultative symbionts (FS) influencing various traits of their hosts. It is therefore worth determining if and how the symbionts of the plant and the aphid modulate their interaction. We used different pea aphid lines without FS or with a single one (Hamiltonella defensa, Regiella insecticola, Serratia symbiotica) to infest Medicago truncatula plants inoculated with Sinorhizobium meliloti (symbiotic nitrogen fixation, SNF) or supplemented with nitrate (non-inoculated, NI). The growth of SNF and NI plants was reduced by aphid infestation, while aphid weight (but not survival) was lowered on SNF compared to NI plants. Aphids strongly affected the plant nitrogen fixation depending on their symbiotic status, suggesting indirect relationships between aphid- and plant-associated microbes. Finally, all aphid lines triggered expression of Pathogenesis-Related Protein 1 (PR1) and Proteinase Inhibitor (PI), respective markers for salicylic and jasmonic pathways, in SNF plants, compared to only PR1 in NI plants. We demonstrate that the plant symbiotic status influences plant–aphid interactions while that of the aphid can modulate the amplitude of the plant's defence response.

Effects of residual S-metolachlor in soil on the phyllosphere microbial communities of wheat (Triticum aestivum L.)

S-metolachlor (S-ME) is a widely used chiral herbicide that can cause potential ecological risks via long-term usage. In this work, we chose a model plant, wheat, as the test material to determine the effects of applying 10 mg/kg S-ME to soil on its fresh weight, chlorophyll and malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity and the diversity and structural composition of the phyllosphere microorganisms after 7 and 14 days of exposure. Our work showed that this concentration of residual S-ME in soil only slightly decreased plant biomass and had little effect on lipid peroxidation, the antioxidant enzyme system and chlorophyll content. Interestingly, although the test concentration of S-ME did not exert strong inhibitory effects on the physiological activities of wheat, it decreased the diversity of phyllosphere microbial communities and changed their structure, indicating that microorganisms were more sensitive stress indicators. S-ME reduced the colonization by some beneficial bacteria related to plant nitrogen fixation among the phyllosphere microorganisms, which influenced the growth and yield of wheat because these bacteria contribute to plant fitness. In addition, S-ME affected the association between the host and the composition of the phyllosphere microbial communities under different growth conditions. Our work provides insights into the ecological implications of the effects of herbicides on the phyllosphere microbiome.

Effects of invasive N2-fixing Acacia mearnsii on sediment nutrient concentrations in mountain streams: Implications of sediment geochemistry for ecosystem recovery

Widespread invasive nitrogen-fixing plant species pose major threats to water resources, biodiversity and nutrient dynamics of river catchments around the world. However, the impacts of invasive N2-fixing plants on in-stream sediment nutrient dynamics remain poorly understood. Here, we quantified the impacts of invasive N2-fixing Acacia mearnsii and A. mearnsii clearing on two mountain streams in South Africa’s Cape Floristic Region. Nutrients were measured in fine sediment that had infiltrated into the gravel bed and surface water in three reaches associated with natural fynbos shrubs, A. mearnsii invaded and cleared riparian ecotones. Results showed that the impacts of A. mearnsii invasions and Acacia clearing in riparian areas on in-stream sediment-associated nutrient concentrations are context-dependent. The difference in channel morphometry and sediment geochemical attributes at reach-scale contributed to the contrasting spatial patterns of sediment-adsorbed nutrients within these rivers. There was also an indication of a long-lasting effect of invasion on total phosphorus that could persist in river sediments ≥10 years after the removal of dense A. mearnsii stands in close proximity to streams. This could be a result of the complexation between phosphorus and immobile iron in sediment, resulting in the retention of ‘legacy phosphorus’. This underlines the importance of fine sediments in capturing nutrients and ultimately regulating nutrient concentrations in the water column.