Runoff and soil erosion under rainfall simulation of Andisols from the Ecuadorian Páramo: effect of tillage and burning

In northern Ecuador, soils of high altitude grasslands (páramos) are mainly non-allophanic Andisols developed on Holocenic volcanic ash. These soils have a high water retention capacity and are the “water tank” of central Ecuador. To assess the effect of land use (burning and tillage) on soil hydrodynamic properties, rainfall simulation was conducted at two different sites. At Pichincha near Quito, the simulation was conducted on a recent volcanic ash soil comparing natural, tilled and burned plots. At El Angel, the simulation was conducted on a mature non-allophanic Andisol comparing natural, recently tilled and formerly cultivated plots.On natural plots, the infiltration rate was very high and sediment loss very low. Results for infiltration rate and runoff indicated that land use change on páramos increased runoff flow and reduced saturated hydraulic conductivity. Superficial reorganisation of the soil surfaces occurred on tilled plots at both sites. This crusting process was fast and resulted in surfaces with very low conductivity at Pichincha. The same processes seemed to be slower at El Angel. The soil surface of recent Andisols at Pichincha was prone to crusting whereas the mature Andisol, at El Angel, with a lower bulk density, was compacted when the kinetic energy of raindrops was high. Water repellency occurred after burning at Pichincha and following long natural air drying after tillage in the non-allophanic A horizon at El Angel. Water repellency combined with the low bulk density of soil aggregates explain the intensity of sediment losses in the abandoned soils after cultivation (Bare fallow plots). Erosion occurred in these areas through floating hydrophobic and stable aggregates.     

Study on the distribution patterns of sulfate-reducing bacteria in a paddy-field soil by Iδ-index

An attempt was made to elucidate the distribution patterns of sulfate-reducing bacteria in a paddy-field soil quantitatively by the use of Morishita's Iδ-index. It was shown from the Iδ-quadrat size relations and Iδ(s)/Iδ(2s) curves that the bacterial distribution was not uniform nor random, but contagious, forming a small clump or clumps of several sizes, which were estimated to be 8 to 32 mm².     

anwendung der „vergleichsmethode standort (vermost)” zur bewertung der erosionsgefährdungspotenziale als datenbasis für förderinstrumente am beispiel des landes Brandenburg: Application of the site comparison method (vermost) to assess the potential erosion risk as a basis to examine instruments of environmental policy – the example of Brandenburg

This paper presents a comparative method (VERMOST) to evaluate complex site conditions at the level of a federal state (Brandenburg) and at different areal units. The methodology uses primary site conditions and provides the possibility to objectively compare and judge different ecological questions. Objects with heterogeneous content are pooled in comparison groups. Considering the main site characteristics allows a goal-oriented allocation of subsidies. The use of VERMOST is demonstrated for the wind and water erosion risk assessment across different scales from a federal state down to a parcel of land. The ‘parcel’ aggregation-level proves to be useful to assess the erosion risk. Larger scales are less useful in the assessment of subsidies policy with regard to erosion risk. A moving-window-technique combined with VERMOST is demonstrated to be suitable for comparing and assessing regional aspects more objectively compared with data administratively linked.     

Predicted trends of soil erosion and sediment yield from future land use and climate change scenarios in the Lancang–Mekong River by using the modified RUSLE model

Soil erosion and sediments in the Lancang-Mekong River Basin as a result of climate change and changes in land use pose a threat to the existence of the riparian people, biodiversity and ecosystems. This study seeks to assess the annual soil erosion in terms of spatial distribution and the trends of sediment yield with the climate and land changes in future scenarios in 2030 and 2040 through the modified RUSLE model. Future lands were simulated by using the MLP artificial neural network and the Markov chain analysis. The future climate was examined by using the Max Planck Institute model, which showed a corrected bias and downscaled grid size under the Representative Concentration Pathways (RCPs). The simulated land use indicated that the forest areas were converted mostly to agricultural lands and urban areas. In the future, the average rainfall under all RCP scenarios is higher than that from the historical period. The R and C factors changed constantly, thereby affecting the soil erosion rate and sediment yield. The maximum erosion was estimated at approximately 21,000 and 21,725 t/km²/y under RCP8.5 in both years. Meanwhile, the results of sediment yield in 2030 and 2040 under RCP scenarios were much higher when compared to historical sediment data around 66.3% and 71.2%, respectively. Thailand's plateau, some parts of Cambodia and Laos PDR and the Mekong Delta are vulnerable to increase soil erosion and sediment yield. Measures to address these issues need to be planned to prepare and mitigate the possible effects, especially the loss of storage capacity in dams.     

Catclaw (Mimosa buincifiera): a pest or a means to restore soil fertility in heavily eroded soil from the central highlands of Mexico?

 In the central highlands of Mexico, heavily eroded soils are often colonized by catclaw (Mimosa buincifiera): an N₂-fixing shrub. An experiment was carried out to investigate how this shrub affected characteristics of the soil and its biological functioning. Soil was sampled from outside and under the canopy of catclaw at three sites characterized by different degrees of erosion and an increase in plant density. The soil microbial biomass C, total amounts of bacteria, fungi, actinomycetes and free-living N₂-fixing micro-organisms were measured, while production of CO₂ and dynamics of nitrate (NO₃ ^–), nitrite (NO₂ ^–) and ammonium (NH₄ ⁺) were monitored in an aerobic incubation at 22±1  °C for 35 days. The C content was 1.6 times greater in the area with the largest density of plants and the least erosion (RECUP) compared with the site with the lowest density and greatest erosion (DEGR), while it was 1.2 times greater under the canopy of the catclaw than outside it (average of the three sites). The incorporation of N into the soil organic matter was greater under the canopy of the catclaw than outside it as the C:N ratio was on average 8.4 and 9. 1, respectively. The microbial biomass C, as a percentage of soil organic matter, was 1.5 times greater in the RECUP than in the DEGR site. Greatest total number of colony-forming bacteria and fungi (mean of organisms found under and outside the canopy) were found in the RECUP treatment and lowest in the DEGR treatment. Free-living N₂-fixing organisms and actinomycetes showed opposite trends. Greater total numbers of colony-forming bacteria, fungi, actinomycetes and free-living N₂-fixing organisms (mean of the three treatments) were found under the canopy of catclaw than outside of it, Production of CO₂ was 1.8 times greater in the RECUP than in the DEGR and 1.6 times greater under the canopy of catclaw than outside. Production of NO₃ ^– was 1.3 times greater in the RECUP than in the DEGR and 3.5 times greater under the canopy of catclaw than outside. There was no significant effect of location or canopy on NO₂ ^– and NH₄ ⁺ concentrations. It is concluded that the natural vegetation of catclaw increased microbial biomass and soil organic matter content under, but also outside its canopy, and preserved N better, releasing greater amounts of inorganic N upon mineralization. Catclaw can serve as a first colonizer of heavily eroded soil and be replaced by other vegetation, natural or crops, when fertility is restored. Received: 4 November 1999     

Extractability of microbial N as influenced by C : N ratio in the flush after drying or fumigation

 Extractability of microbial N was estimated using in situ labelling of the microbial population with ¹⁵N. Four arable soils (one grey forest soil and three chernozems with different long-term fertilization) were amended with (NH₄)₂SO₄ (unlabelled or labelled with ¹⁵N) and d-glucose with a C : N ratio of 10 : 1 or 20 : 1 for the grey forest soil and 50 : 1 for the chernozems. d-glucose and labelled N with a C : N ratio of 20 : 1 did not cause microbial immobilization of unlabelled N. The use of substrates with a C : N ratio of 50 : 1 led to a pronounced priming action on soil N and decreased the extractability of immobilized ¹⁵N. Values of the extractable biomass N fraction (k _EN ) assessed for the fumigation-extraction and rehydration procedures were similar and varied in inverse proportion to the C : N ratio of the flush. The k _EN factor was calculated using values of the C : N ratio in flushes and the fixed C : N ratio of structural cell components, with the assumption that the C : N ratio of the extractable cytoplasmic cell fraction is variable. The ratio between the extractable and non-extractable biomass N fraction (k _EC ) and the C : N ratio of non-extractable cell components were assessed as equation parameters optimized for the measured k _EN and C : N ratio of flush data. Received: 31 October 1997     

Untersuchungen zur entwicklung von stoffgehalten im aufwuchs von niedermoorstandweiden in abhängigkeit vom vegetationsverlauf: Investigations about development of stuff contents in growth of lowland moor large units pasture in dependence from vegetation progress

Der geringe Bestand an Rindern in den neuen Bundesländern lässt auch den Einsatz von Schafen zur Offenhaltung des Niedermoorgrünlandes erforderlich werden. Die hohe Selektivität bei der Futteraufnahme macht Maßnahmen des Weidemanagements erforderlich, die über die reine Standweide hinausgehen. Der Verlauf der TS-Gehalte im Aufwuchs zeigt ein deutliches Maximum im Juni. Durchwuchs junger Triebe im Sommer lässt die Gehalte im Mittel zwar absinken, der Bestand bleibt aber sehr unausgeglichen. Bei Einschaltung einer Mähnutzung werden wichtige Parameter im Sinne von Futterqualität und Verzehrleistung positiv beeinflusst (TS-Gehalt, Rohfaser, Rohprotein). Die späte Mahd ist kaum wirkungsvoll und kann auf biologisch aktiven Weideflächen durch Verteilung von Erdaufhäufungen zur Verschmutzung des Futters beitragen.     

Nitrification and denitrification in an acidic soil of tea (Camellia sinensis L.) field estimated by δ15N values of leached nitrogen from the soil columns treated with ammonium nitrate in the presence or absence of a nitrification inhibitor and with slow-release fertilizers

Forty-two-day-old wheat (Triticum aestivum L. var. Asakazekomugi) plants were treated with complete, K-free (—K), Ca-limited (—Ca), and Mg-free (—Mg) nutrient solutions for 10 days using 2 mM NH₄NO₃ as the nitrogen source, which was replaced with 4 mM ¹⁵ NH₄C1 or Na¹⁵NO₃ for the subsequent 2 days to investigate the absorption, translocation, and assimilation of inorganic nitrogen in relation to the mineral supply. In another experiment plants were grown on NO₃ ^?, NH₄ ⁺, NH₄N0₃, and K-free and Ca-limited NH₄N0₃ nutrient solutions for 10 days, and then in the latter three treatments the nitrogen source was replaced with NO₃ ^? and half of the —K plants received K for 6 days to examine the changes in the nitrate reductase activity (NRA).

Wheat plants absorbed NH₄ ^?N and NO₃-N at a similar rate. Influence of K on the absorption of N0₃-N was stronger than that on the absorption of NH₄-N in wheat plants. The supply of K to the —K plants increased the absorption of NO₃-N, while the absorption of NH₄-N still remained at a lower rate in spite of the addition of K. A limited supply of Ca and lack of Mg in nutrient media slightly affected the absorption of NH₄-N. The influence of K was stronger on the translocation of nitrogen from roots to shoots, while Ca and Mg had little effect. When K was supplied again to the —K plants the translocation of NO₃,-N was more accelerated than that of NH₄-N. Incorporation of NH₄-N into protein was higher than that of NO₃-N in all the tissues; root, stem, and leaf. Assimilation of NH₄-N and NO₃-N decreased by the —K and —Mg treatments.

Leaf NRA of wheat plants decreased in the —K and —Ca plants. Higher leaf NRA was found when K was given again to the —K plants than when the plants were continuously grown in K-free media. Replacement of NO₃ ^? with NH₄ ⁺ as the nitrogen source caused a decline of leaf NRA, while the supply of both NH₄ ^?N and NO₃-N slightly affected the leaf NRA.     

Is the long-term application of sewage sludge turning soil into a sink for organic pollutants?: evidence from field studies in the Czech Republic

Purpose

Long-term microscale field experiments established at four sites in the Czech Republic (since 1996) were used for an assessment of the severity of the wide-scale contamination of treated soils by persistent organic pollutants (POPs) and pharmaceuticals and personal care products (PPCPs) as a result of the long-term regular pollutant load via sewage sludge and farmyard manure applications and for an estimation of the potential environmental risk caused by long-term pollutant inputs to agricultural soils.

Material and methods

The experimental plots were treated as follows: (i) NPK mineral fertilization (NPK); (ii) sewage sludge (SS1); (iii) sewage sludge applied at three times the rate compared to SS1 (SS2); (iv) farmyard manure (FYM); and (v) untreated control. Except for antibiotics, which showed results for all analyses below the detection limit, all groups of the analyzed compounds showed measurable contents in the treated soils.

Results and discussion

Among the POPs, the levels of organochlorine pesticides (OCPs) were detected at two locations at levels exceeding the Czech preventive values for their contents in agricultural soils (7.5 μg/kg for dichlorodiphenyl trichloroethane family, 20 μg/kg for hexachlorbenzene, and 10 μg/kg for α-hexachlorocyclohexane), regardless of the treatment. Similarly, elevated contents of polycyclic aromatic hydrocarbons (PAHs) were occasionally observed without any substantial relationship to the fertilizer application scenario. Thus, these contaminants are connected with atmospheric deposition in the given areas (PAHs) and their long-term stability (OCPs) even several decades after their ban; the role of the fertilizer composition was negligible.

Conclusions

The levels of per- and polyfluoroalkylated substances, brominated flame retardants, and synthetic musk compounds tended to increase in the sewage sludge–treated plots, indicating that sewage sludge can contribute to the abundance of these compounds in soil, although the contaminant levels determined do not represent a direct environmental risk. The levels of these contaminants in sewage sludge and sludge-treated soils should be regularly monitored in further research.

     

Entwicklung der organischen bodensubstanz (obs) auf löss in abhängigkeit von unterschiedlicher düngung am beispiel des bodenbildungsversuches in Halle/Saale: Development of soil organic matter (som) on loess in dependence of different fertilization e.g. of the soil formation trial at Halle/Saale

In 1948, a model trial to study soil formation was arranged at Halle/Saale by K. Schmalfuß. Loess with very low content of soil organic matter was used as substrate. The aim was to investigate the soil formation processes influenced by the P and N mineral fertilization. After 30 years, crop yields reached a characteristic, approximately constant level corresponding to the different fertilization treatments and cultivated plants. Recent comparisons of the highest N with the no-N fertilizer treatment show that the mean shoot dry weight per year has a 2.5-fold higher but the C_org content in the topsoil only a 1.2-fold higher value. An accumulation of alkaline-soluble organic soil substances and a decrease of hot water soluble carbon compounds were observed in the highest fertilizer treatment as well as in the treatments without N or P fertilization. Carbon compounds were apparently enriched in the inert carbon pool of the topsoil. During soil formation, the cation exchange capacity and the content of easily soluble P compounds increased, lime content decreased and the C/N ratio became narrower. The results suggest that these parameters are continuing to change and the steady state of the level of organic soil substances and of the transformation processes between C pools in the topsoil has not yet been reached.     

Semiquantitative determination of imogolite and Al-rich allophane (Si / Al ≃ 1 : 2) in some volcanic ash soils in San'in region by a combination of thermogravimetry-differential thermal analysis and trimethylsilylation analysis of soil clays

Abstract

A method to determine the contents of imogolite and Al-rich allophane (Sil Al ? 1 : 2) in volcanic ash soils was presented. The method is based on the (1) assessment of the presence of Al-rich allophane in clays by successsive extraction with dithionite-citrate and oxalate-oxalic acid, (2) trimethylsilylation of soil clay with a mixture of hexamethyldisiloxane, HCl, and isopropyl alcohol, and determination of the content of monomeric Si based on the trimethylsilyl derivative of monomeric orthosilicate anion by gas / liquid chromatography, (3) determination of the total content of imogolite and Al-rich allophane based on the content of monomeric Si from imogolite, (4) determination of the imogolite content by Thermogravimetry (TG )-Differential Thermal Analysis (DTA) based on the weight loss due to endothermic dehydroxylation with maximum values at ca. 386°C, (5) calculation of the Al-rich allophane content by subtracting the imogolite content from the total content of these minerals, and (6) evaluation of the imogolite and Al-rich allophane content of soil by multiplying clay content of soil and the two mineral content of clay. The trimethylsilylation analysis was found to be reproducible, and the estimated total amounts of two minerals in clays by this method were adequately approximated to those evaluated from the amount of Si (= Si_o) extracted with oxalate-oxalic acid after extraction with dithionite-citrate. The variation in the abmldance of two minerals in the soil horizons of volcanic ash soils from the San'in region indicated that this method is suitable for the profile-study of volcanic ash soils.     

Untersuchungen zur verdaulichkeit und zum energiegehalt von futterpflanzen auf niedermoorstandweiden in abhängigkeit vom vegetationsverlauf: Investigations about digestibility and energy content of fodder plants on lowland moor large units pasture in dependence from vegetation progress

On lowland moor large units pasture, which are used for holding paddock sheep, several differences in aerosis ability are given, in the apparent digestibility and in the capacity of energy (metabolizable energy and net energy lactation) in connection with stage of vegetation between several care variants (without fertilization, fertilized and combined utilization) of fodder plants. Especially in the second period of vegetation one has to consider a reduction of nutrient concentration in the fodder on unfertilized pasture segments. Under conditions of extensive grassland management with intensive races these relations have a limitative influence on the animal efficiency, because in fodder growth there are imbalances between the energy and protein supply. On the other hand, grass in the fertilized variant shows a higher digestibility and more energy at this time. In relation to the nutrient supply, the combined utilization is the most well-known variant. Lower raw fibre concentrations offer a high feed intake capacity for pasture animals.     

Freilandversuche zur eignung chemisch veränderter weichbraunkohle als bodenverbesserungsmittel bei der landwirtschaftlichen rekultivierung humusfreier kippenböden 1 : Field experiments with n-modified brown coal as humus fertilizer in agricultural revitalisation of humus free dump soils

Die bodenmeliorativen und ertragssteigernden Effekte des Einsatzes von N-modifizierter Weichbraunkohle als Humusdüngestoff bei der landwirtschaftlichen Rekultivierung humusfreier Kippenböden werden in mehreren Freilandversuchen überprüft. In diesem Beitrag wird über die zu Rekultivierungsbeginn mit W.-Roggen, W.-Weizen, Kartoffeln und Luzerne erzielten Ergebnisse berichtet.     

Reactivity of lignin with different composition of aromatic syringyl/guaiacyl structures and erythro/threo side chain structures in β-O-4 type during alkaline delignification: as a basis for the different degradability of hardwood and softwood lignin

The reactivity of lignin during alkaline delignification was quantitatively investigated focusing on the effect of the structural differences between syringyl and guaiacyl aromatic nuclei and between erythro and threo in the side chain of β-O-4 type lignin substructure on the β-O-4 bond cleavage rate. It was known that the ratio of this reaction rate of the erythro to threo isomers of the dimeric β-O-4 type lignin model compound with two guaiacyl aromatic nuclei was ca. 4. However, the presence of a syringyl nucleus strongly influenced the rate, and the ratio of the syringyl type analogue was in the range between 2.7 and 8.0 depending on the reaction temperature. The effect of syringyl nucleus on the enhancement of the reaction rate appeared to be greater when the syringyl nucleus consists of the cleaving ether bond rather than being a member of the carbon framework.     

Biochar applications enhance the phytoextraction potential of Salix smithiana [Willd.] (willow) in heavily contaminated soil: potential for a sustainable remediation method?

Journal of Soils and Sediments - The combination of chemostabilization and phytoextraction provide an affordable and environmentally effective remediation technology for the heavy metals in...     

Studying the effect of organic matter recycling combined with mineral n fertilization in long-term field and model pot experiments: Untersuchung der wirkung der rezyklierung der organischen substanz kombiniert mit mineraldüngung in dauerfeldversuchen und modellgefässversuchen

The effect of various combinations of organic and mineral N fertilizers was studied on the organic matter content of the soil, grain yield, dry matter production and N-uptake of maize. In a model experiment, large pots were filled with 55?kg sandy loam soil originating from the plots of the ‘International Long-term Experiments for Investigating the Effect of Organic and Inorganic Fertilisers’ (IOSDV), Keszthely. The field experiment, which was set up in 1983, contained three crop-rotations with maize, winter wheat and winter barley. Treatments: (1) inorganic fertilizers only with increasing N-doses (N); (2) farmyard manuring (FYM) in every third year+N; (3) stalk, straw or green manure+N. Our results clearly proved the advantage of organic matter recycling combined with mineral fertilization over treatment 1. In the fifth and sixth rotations, both types of organic matter recycling resulted in significantly higher C_org contents compared to mineral N fertilization without farmyard manuring or incorporation of crop residues. Grain yields in the field trial were the lowest in treatments without organic matter recycling. In the pot experiment, dry matter production and N accumulation in the grains and vegetative plant parts were also significantly higher in treatments where mineral fertilization was combined with organic matter recycling.     

Enantiomeric discrimination and quantification of the chiral organophosphorus pesticide fenamiphos in aqueous samples by a novel and selective ³¹P nuclear magnetic resonance spectroscopic method using cyclodextrins as chiral selector

A rapid, selective, and accurate quantitative 31P nuclear magnetic resonance (31P NMR) spectroscopy method was used for the chiral recognition of the racemic organophosphorus pesticide fenamiphos using chiral solvating agents (CSAs). Six neutral cyclodextrins (CDs) (α-CD, β-CD, methyl-β-CD, hydroxyethyl-β-CD, hydroxypropyl-β-CD, and hydroxypropyl-γ-CD) and two anionic CDs (carboxymethyl-β-CD and carboxyethyl-β-CD) were selected for these experiments. The shift displacement values (Δδ), after addition of each of the eight CDs in the highest possible molar ratio to a guest, were recorded. The results showed that β-CD and hydroxypropyl-β-CD were the best chiral solvating agents for the enantiomeric discrimination of fenamiphos. Two-dimension rotating frame nuclear Overhauser spectroscopy (ROESY) was used to investigate the structure of the β-CD-fenamiphos inclusion complex in aqueous solution. To determine the fenamiphos enantiomers, a calibration curve was drawn for two enantiomers over the range of 0.05-0.25 mg mL?1. The limits of detection (S/N = 3) were obtained as 0.0068 and 0.0060 mg mL?1 for fenamiphos enantiomers. The recovery studies were performed on aqueous real samples ranging from 94 to 107% with coefficients of variation of ≤ 9%.     

Untersuchungen zur CO2-Gas-Austauschrate bei transgenen Fructan bildenden Kartoffellinien ( Solanum tuberosum L.) unter Einsatz eines modularen Großküvettensystems: (Investigations to the CO2 gas exchange rate in transgenic fructans generating potato lines ( Solanum tuberosum L.) by implementation of a modular cuvette system)

Abstract

This survey was aimed at comparing the CO₂ gas exchange rate of transgenic potato lines and of the isogenic line Désirée in order to establish if genetic modification has resulted in ecologically relevant changes. In examining two transgenic potato lines and one isogenic line, a modular whole-plant cuvette system was implemented for the first time. Furthermore, suitability of such a cuvette system for comparative examination was to be tested in the survey at hand. The lowest CO₂ exchange rate was observed in the SST/FFT line. The SST line achieved the highest CO₂ exchange rate of all genotypes tested. Measurement of CO₂ exchange rate, and additionally collected data on morphologic and characteristics of yield physiology, resulted in distinctly correlating data. The phenotypical changes observed could be classified within the growth and yield profile specified by the German Federal Office of Plant Varieties (Bundessortenamt) for potato varieties permitted for cultivation in Germany. A changed growth rate of crop in the transgenic lines could not be established. A modular whole-plant cuvette system can be implemented in comparative gas exchange measurements in a partly air-conditioned cell.     

The invasive alien plant, <Emphasis Type=\"Italic\">Impatiens glandulifera</Emphasis> (Himalayan Balsam), and increased soil erosion: causation or association? Case studies from a river system in Switzerland and the UK

Purpose

A monitoring investigation undertaken along the River Ibach, northwest Switzerland over the winter 2012/2013, found that riparian areas recently supporting the invasive plant Himalayan Balsam (HB) recorded significantly higher erosion rates than nearby uninvaded areas. This communication sythesises the latest findings about the influence of HB on sedimentation processes, again, from the Ibach, but also from a second river system in southwest UK.

Materials and methods

Erosion pins, a micro-profile bridge and a digital caliper were used to measure changes in soil surface profile (SSP) at selected riparian areas supporting HB plants along both rivers. Values were statistically compared against equivalent data recorded from nearby reference areas supporting mixed perennial vegetation. A comparison of source and sediment geochemistry was also undertaken on soil from HB-invaded and uninvaded floodplain areas along the Ibach, to assess the potential for identifying the extent to which either group acts as a sediment source.

Results and discussion

Erosion pin data indicate that soil loss from HB-colonised areas was significantly greater than soil loss from reference areas in two out of the four periods at the River Ibach site, and in two out of three measurement periods at the River Taw site. Colonisation of new HB sites may initially occur by hydrochorous processes, but HB plants may increase colonisation potential by trapping additional fine sediment and organic matter, including viable HB seeds. Geochemical results from the Ibach suggest that high inputs of suspended sediment originate from sources close to the river channel, but HB-invaded floodplain sources have geochemical properties that are most similar to suspended river sediment.

Conclusions

The findings from both rivers led us to rethink our original hypothesis; that HB promotes soil erosion, to an amended hypothesis in which HB may be associated with areas where high erosion is sometimes recorded. Whilst initial colonisation may be due to hydrochorous processes, as HB becomes increasingly established, the displacement of perennial vegetation increases the risk of erosion during the winter period when live HB plants are absent. Preliminary geochemical findings of floodplain soils supporting different vegetation types along the Ibach tentatively suggest that at least some material originating from HB sites may enter the watercourse.