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Philip Greenwood
Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX2 4RJ, United Kingdom

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Standard article
Published: 14 July 2021 in Geographica Helvetica
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A preliminary field-based investigation was undertaken in a small (< 10 km2) river valley located in the mountainous Jura region of northwest Switzerland. The aims of the work were to assess sediment generation and annual sediment transport rates by tree throw on forested hillslopes and to document surface hydrology characteristics on four fresh tree throw mounds associated with recent tree throws over a 24 d monitoring period. For the tree throw mounds, average sediment recovery ranged from 7.7–28.2 g (dry weight), equivalent to a suspended sediment concentration of 145.2–327.8 g L−1, and runoff coefficients ranged from 1.0 %–4.2 %. Based on a soil bulk density value of 1044 kg m−3, upslope runoff generation areas were denuded by an average of 0.14 mm within the 24 d monitoring period, representing an erosion rate equivalent to 2.1 mm a−1. This means that a ca. 50 cm high tree throw mound could theoretically persist for around 200–250 years. For tree throw work, the dimensions of 215 fallen trees were measured and their locations mapped in 12 separate locations where tree throw was prominent along the river valley, representing a cumulative area equivalent to 5.3 ha (average density equivalent to 43 trees ha−1). The 215 tree throws generated a total of 20.1 m3 of fine sediment (< 2 mm dia.), or the equivalent of 3.8×10-4 m3 m−2. The process of tree throw was originally attributed to two extreme weather events that occurred across west and central Europe in late December 1999. Taking the 18-year period since both storms, this represents an annual sediment transport rate of 2.7×10-5 m3 m−1 a−1. Exploring the relationship with wind on fall direction, however, 65.5 % of mapped tree throws (n= 143) generally fell in a downslope direction irrespective of hillslope aspect on which they were located. Given the similar fall orientation for most trees, this infers that severe storms may not have been responsible for the majority of tree throws, but instead, their upheave might be related to root failure. Given the relative maturity (average age 41 years) of fallen trees in this river valley, our data suggest that once trees attain a certain age, their physiognomy (i.e. height, mass, and centre of gravity) compromises their ability to remain securely anchored. We tentatively attribute this possibility to the presence of bedrock close to the surface, and to the shallow soil profile overlaying the steep rocky slopes. More in-depth studies are required to firstly confirm our findings, and secondly, tree throw studies should be undertaken in other Jura mountain river valleys to assess whether these results are representative.

ACS Style

Philip Greenwood; Jan Bauer; Nikolaus J. Kuhn. Assessing hillslope sediment generation potential by tree throw: a preliminary field study along a small river valley in the Jura Mountains, northwest Switzerland. Geographica Helvetica 2021, 76, 319 -333.

AMA Style

Philip Greenwood, Jan Bauer, Nikolaus J. Kuhn. Assessing hillslope sediment generation potential by tree throw: a preliminary field study along a small river valley in the Jura Mountains, northwest Switzerland. Geographica Helvetica. 2021; 76 (3):319-333.

Chicago/Turabian Style

Philip Greenwood; Jan Bauer; Nikolaus J. Kuhn. 2021. "Assessing hillslope sediment generation potential by tree throw: a preliminary field study along a small river valley in the Jura Mountains, northwest Switzerland." Geographica Helvetica 76, no. 3: 319-333.

Journal article
Published: 23 May 2021 in Geoderma
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Whilst evidence has been found that dispersed earthworm casts can act as a sediment-source on fully vegetated hillslopes, uncertainty still remains over the mobility, and hence, the ability of such material to similarly act as a sediment-source on cultivated hillslopes. This study reports preliminary findings from a prototype sediment tracing technique to assess the mobility of eroded earthworm casts on the same unconsolidated (i.e. uncrusted) and crusted hillslope soil using two different artificial radionuclides. A 0.75 * 0.75 * 0.1 m erosion plot, pitched at a 10% slope (5.7°) was filled with bulk soil and textured to simulate an agricultural-type seedbed finish. A total of 56 similarly-sized casts representing 197 g of sediment (dry weight) were labelled with 430 Bq of caesium-134 activity, evenly distributed across the unconsolidated soil and subjected to ca. 15 mm hr-1 of simulated rain until casts disintegrated, during which time surface runoff was collected continuously. Soil was air-dried to allow a surface crust to form and then a further 56 similarly-sized casts representing 198.5 g of sediment (dry weight) were labelled with 433 Bq of cobalt-60 activity, evenly distributed across the crusted surface and again, subjected to simulated rainfall until their complete disintegration. Surface runoff was continuously collected. An unmixing model was used to partition labelled sediment from unlabelled bulk soil. For the 1st rainfall event, 20.6 g of 134Cs-labelled material, representing 10.5% of the total mass deployed, was removed by surface runoff from the unconsolidated surface. During the 2nd rainfall event, a further 16.2 g of 134Cs-labelled sediment (8.2%) was removed from the crusted surface, along with 73.1 g (36.8%) of 60Co-labelled sediment. In comparison with 134Cs-labelled material, approximately double the amount of 60Co-labelled sediment was eroded from the crusted soil in approximately half the rainfall exposure time. These findings, although very preliminary, firstly provide proof-of-concept confirming the efficacy of the tracing technique and secondly, suggest that cast-derived material is not only mobile on cultivated hillslopes, but the degree of mobility and hence the source-potential of the eroded material increase markedly when soil surface conditions change from unconsolidated to crusted.

ACS Style

Philip Greenwood. A prototype tracing-technique to assess the mobility of dispersed earthworm casts on a cultivated hillslope soil under unconsolidated and crusted surface conditions. Geoderma 2021, 400, 115220 .

AMA Style

Philip Greenwood. A prototype tracing-technique to assess the mobility of dispersed earthworm casts on a cultivated hillslope soil under unconsolidated and crusted surface conditions. Geoderma. 2021; 400 ():115220.

Chicago/Turabian Style

Philip Greenwood. 2021. "A prototype tracing-technique to assess the mobility of dispersed earthworm casts on a cultivated hillslope soil under unconsolidated and crusted surface conditions." Geoderma 400, no. : 115220.

Journal article
Published: 26 March 2021 in Anthropocene
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Land-use-induced soil erosion in semi-arid drylands induced by land-use changes creates patchworks of soils and vegetation different from those of natural conditions. Knowledge of the highly dynamic spatial heterogeneity in soil properties, not depicted in conventional soil maps, is important for managing land uses sustainably, and for understanding soil-climate interactions. This analysis of soil redistribution in a degraded rangeland in South Africa assessed the significance of anthropogenic soil heterogeneity within a small catchment with a silted reservoir. This study carries out analysis of soil redistribution in a degraded rangeland in South Africa, to assess the significance of anthropogenic soil heterogeneity within a small catchment with a silted-up reservoir. Surface soil (N = 51) and soil profile (N = 29) samples were collected from areas of various degrees of degradation and analysed for texture, pH, total nitrogen (TN), total organic carbon (TOC), available phosphorus (P), and potassium (K). Diverse vegetation cover is reflected in a high soil heterogeneity, showing differences in soil texture. Average surface soil nutrient content was significantly higher in vegetated areas (grassland: TOC 1.08 %, TN 0.10 %, P 20.12 mg kg−1, mixed vegetation: TOC 0.93 %, TN 0.08 %, P 13.54 mg kg−1, depositional: TOC 1.68 %, TN 0.18 %, P 34.67 mg kg−1) than at degraded sites (TOC 0.47 %, TN 0.06 %, P 7.52 mg kg−1). K content was low to moderate but did not show any significant difference between landscape units. Potential exists for the formation of distinct young anthropogenic soils on the silted-up reservoir where deposited sediments differed in TOC, TN, P, and profile depth from the shallow natural soils. Consequently, azonal soils on dam-deposits are different from those occurring naturally, and not depicted on conventional soil maps. Their different water and nutrient cycling may affect vegetation and biogeochemical fluxes. Land-use management should consider such soils, as they play an important role in rangeland ecology.

ACS Style

Juliane Krenz; Philip Greenwood; Nikolaus J. Kuhn. Anthropogenic erosion-induced small-scale soil heterogeneity in South African rangelands. Anthropocene 2021, 34, 100290 .

AMA Style

Juliane Krenz, Philip Greenwood, Nikolaus J. Kuhn. Anthropogenic erosion-induced small-scale soil heterogeneity in South African rangelands. Anthropocene. 2021; 34 ():100290.

Chicago/Turabian Style

Juliane Krenz; Philip Greenwood; Nikolaus J. Kuhn. 2021. "Anthropogenic erosion-induced small-scale soil heterogeneity in South African rangelands." Anthropocene 34, no. : 100290.

Original article
Published: 07 February 2021 in Journal of Mountain Science
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A preliminary field-based investigation was undertaken in a small (< 10 km2) river valley located in the mountainous Jura region of northwest Switzerland. The aims of the work were to assess sediment generation and annual sediment transport rates by tree throw on forested hillslopes, and to document surface hydrology characteristics on four fresh soil mounds associated with recent tree throws over a 24-day monitoring period. For the soil mounds, average sediment recovery ranged from 7.7–28.2 g (dry weight), equivalent to a suspended sediment concentration of 145.2–327.8 g L−1, and runoff coefficients ranged from 1.0%–4.2%. Based on a soil bulk density value of 1,044 kg m−3, upslope runoff generation areas were denuded by an average 0.14 mm by the end of the 24-day monitoring period, representing an erosion rate equivalent to 2.1 mm yr−1. A ca. 50 cm high soil mound could therefore feasibly persist for around 200–250 years. For tree throw work, the dimensions of 215 individual tree throws were measured and their locations mapped in 12 separate locations along the river valley representing a cumulative area equivalent to 5.3 ha (av. density, 43 per ha). Tree throws generated a total of 20.1 m3 of fine-sediment (< 2 mm diameter), or the equivalent of 3.8 × 10−4 m3 m−2. The process of tree throw was originally attributed to two extreme weather events that occurred in west and central Europe in late December 1999. Taking the 18-year period since both storms, this represents an annual sediment transport rate of 2.7 × 10−5 m3 m−1 yr−1. Exploring the relationship with wind on fall direction, 65.5% of tree throws (143) generally fell in a downslope direction irrespective of hillslope aspect on which they were located. This infers that individual storms may not have been responsible for the majority of tree throws, but instead, could be associated with root failure. Given the high density of tree throws and their relative maturity (average age 41 years), we hypothesise that once trees attain a certain age in this river valley, their physiognomy (i.e. height, mass and centre of gravity) compromises their ability to remain securely anchored. We tentatively attribute this possibility to the presence of bedrock close to the surface, and to the shallow soil profile overlaying steep hillslopes.

ACS Style

Philip Greenwood; Jan Bauer; Nikolaus J. Kuhn. Sediment generation and soil mound denudation in areas of high-density tree throw along a river valley in the Jura Mountains, Switzerland. Journal of Mountain Science 2021, 18, 377 -391.

AMA Style

Philip Greenwood, Jan Bauer, Nikolaus J. Kuhn. Sediment generation and soil mound denudation in areas of high-density tree throw along a river valley in the Jura Mountains, Switzerland. Journal of Mountain Science. 2021; 18 (2):377-391.

Chicago/Turabian Style

Philip Greenwood; Jan Bauer; Nikolaus J. Kuhn. 2021. "Sediment generation and soil mound denudation in areas of high-density tree throw along a river valley in the Jura Mountains, Switzerland." Journal of Mountain Science 18, no. 2: 377-391.

Correction
Published: 19 May 2020 in Soil Systems
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The authors wish to make the following corrections to this paper

ACS Style

Juliane Krenz; Philip Greenwood; Nikolaus J. Kuhn. Correction: Krenz, J., et al. Soil Degradation Mapping in Drylands Using Unmanned Aerial Vehicle (UAV) Data. Soil Syst. 2019, 3, 33. Soil Systems 2020, 4, 33 .

AMA Style

Juliane Krenz, Philip Greenwood, Nikolaus J. Kuhn. Correction: Krenz, J., et al. Soil Degradation Mapping in Drylands Using Unmanned Aerial Vehicle (UAV) Data. Soil Syst. 2019, 3, 33. Soil Systems. 2020; 4 (2):33.

Chicago/Turabian Style

Juliane Krenz; Philip Greenwood; Nikolaus J. Kuhn. 2020. "Correction: Krenz, J., et al. Soil Degradation Mapping in Drylands Using Unmanned Aerial Vehicle (UAV) Data. Soil Syst. 2019, 3, 33." Soil Systems 4, no. 2: 33.

Journal article
Published: 12 December 2019 in Soil and Tillage Research
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Understanding the extent to which textural characteristics of inter-rill and rill-eroded sediment differ across a range of agricultural soils is important in order to more accurately predict sediment transport capacities and thus increase the reliability of erosion models. However, a lack of consensus still exists over how much influence these two mechanisms exert on the physical characteristics of sediment during an erosion event. This communication reports results from a prototype tracing technique using two different artificial radionuclides to compare the grain size composition of inter-rill and rill-eroded sediment from eight different cultivated hillslope soils from southern England. A 1.0 m * 0.2 m * 0.11 m soil box was filled with soil labelled with caesium-134 (134Cs) to a depth of 0.1 m. A second layer of soil labelled with cobalt-60 (60Co) was distributed across the first soil layer, to a depth of 0.01 m, and lightly textured to replicate a fine tilth. The soil box was pitched at a ca. 17% slope (9.5°) and each soil was subjected to ca. 35 mm hr−1 of simulated rainfall until surface runoff was initiated and a rill developed. All runoff-eroded sediment was collected over 90 s intervals, dried and radiometrically assayed. Changes in radiometric signals were used to identify the transition from inter-rill to rill erosion, demarking a shift in sediment-source. Samples recording highest activity of either radionuclide were deemed to contain largest contributions of sediment mobilised by each respective erosion process and were selected for grain size analysis. Grain sizes, measured at 10 percentile intervals, were subjected to a paired-sample statistical analysis to determine whether size-difference was significant. Rill-eroded sediment was significantly coarser than inter-rill eroded sediment for four soils, whereas inter-rill eroded sediment was significantly coarser than rill-eroded sediment for one soil. There was no significant size-difference for two soils, and one soil was omitted from statistical analysis due to excessive contamination by the sub-dominant erosion process.

ACS Style

Philip Greenwood; Yusheng Zhang. Comparing grain size composition of inter-rill and rill-eroded sediment from cultivated hillslope soils using caesium-134 and cobalt-60 as tracers. Soil and Tillage Research 2019, 198, 104532 .

AMA Style

Philip Greenwood, Yusheng Zhang. Comparing grain size composition of inter-rill and rill-eroded sediment from cultivated hillslope soils using caesium-134 and cobalt-60 as tracers. Soil and Tillage Research. 2019; 198 ():104532.

Chicago/Turabian Style

Philip Greenwood; Yusheng Zhang. 2019. "Comparing grain size composition of inter-rill and rill-eroded sediment from cultivated hillslope soils using caesium-134 and cobalt-60 as tracers." Soil and Tillage Research 198, no. : 104532.

Special issue article
Published: 02 December 2019 in Weed Research
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Soil loss from riparian areas supporting the annual invasive weed, Impatiens glandulifera (Himalayan balsam), was measured and compared with equivalent values recorded at nearby, topographically similar areas supporting perennial vegetation over a cumulative seven‐year period, along sections of two separate river systems; one in Switzerland, and one in the UK. Soil loss from colonised locations was significantly greater than from reference locations in four of the seven measurement periods. Despite contrasting results, standard deviations, based on soil losses and gains, were predominantly higher for colonised areas at both rivers over most monitoring periods. These findings indicated that areas colonised by Himalayan balsam experience higher sediment flux in comparison with areas free of invasion. Here, we test those original interpretations by reinterrogating the datasets using a more robust analysis of inequality. Nine datasets were tested, five of which (i.e. 56%) showed that sediment flux was significantly greater at Himalayan balsam‐invaded areas than at reference areas. Three datasets showed no difference in sediment flux between invaded and reference areas (33%), and one (11%) showed higher sediment flux at reference areas. Most results uphold our original interpretations and support our hypothesis that hydrochory probably dictates where colonisation initially occurs, by depositing Himalayan balsam seeds in slack or depressional areas along river margins. Once Himalayan balsam becomes established and sufficient perennial vegetation is displaced, seasonal die‐off and depleted vegetation cover may increase the risk that some areas will experience significantly higher sediment flux.

ACS Style

P Greenwood; A C Gange; N J Kuhn. Evidence of sedimentation inequality along riparian areas colonised by Impatiens glandulifera (Himalayan balsam). Weed Research 2019, 60, 26 -36.

AMA Style

P Greenwood, A C Gange, N J Kuhn. Evidence of sedimentation inequality along riparian areas colonised by Impatiens glandulifera (Himalayan balsam). Weed Research. 2019; 60 (1):26-36.

Chicago/Turabian Style

P Greenwood; A C Gange; N J Kuhn. 2019. "Evidence of sedimentation inequality along riparian areas colonised by Impatiens glandulifera (Himalayan balsam)." Weed Research 60, no. 1: 26-36.

Journal article
Published: 07 May 2019 in Soil Systems
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Arid and semi-arid landscapes often show a patchwork of bare and vegetated spaces. Their heterogeneous patterns can be of natural origin, but may also indicate soil degradation. This study investigates the use of unmanned aerial vehicle (UAV) imagery to identify the degradation status of soils, based on the hypothesis that vegetation cover can be used as a proxy for estimating the soils’ health status. To assess the quality of the UAV-derived products, we compare a conventional field-derived map (FM) with two modelled maps based on (i) vegetation cover (RGB map), and (ii) vegetation cover, topographic information, and a flow accumulation analysis (RGB+DEM map). All methods were able to identify areas of soil degradation but differed in the extent of classified soil degradation, with the RGB map classifying the least amount as degraded. The RGB+DEM map classified 12% more as degraded than the FM, due to the wider perspective of the UAV compared to conventional field mapping. Overall, conventional UAVs provide a valuable tool for soil mapping in heterogeneous landscapes where manual field sampling is very time consuming. Additionally, the UAVs’ planform view from a bird’s-eye perspective can overcome the limited view from the surveyors’ (ground-based) vantage point.

ACS Style

Juliane Krenz; Philip Greenwood; Nikolaus J. Kuhn. Soil Degradation Mapping in Drylands Using Unmanned Aerial Vehicle (UAV) Data. Soil Systems 2019, 3, 33 .

AMA Style

Juliane Krenz, Philip Greenwood, Nikolaus J. Kuhn. Soil Degradation Mapping in Drylands Using Unmanned Aerial Vehicle (UAV) Data. Soil Systems. 2019; 3 (2):33.

Chicago/Turabian Style

Juliane Krenz; Philip Greenwood; Nikolaus J. Kuhn. 2019. "Soil Degradation Mapping in Drylands Using Unmanned Aerial Vehicle (UAV) Data." Soil Systems 3, no. 2: 33.

Research article
Published: 13 November 2018 in Land Degradation & Development
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Poaching is caused by the excessive trampling of soil and vegetation by herd animals and is prevalent in intensively‐managed grasslands. It is viewed as detrimental to soil fertility, has the potential to contribute to soil erosion and thus represents a form of land degradation that is unsustainable. Attempts to document sediment redistribution by poaching have been hampered by a lack of techniques capable of measuring the movement of poached material at requisite spatial and temporal scales. We present a new tracing technique, using caesium‐134 (134Cs) and cobalt‐60 (60Co), which is designed to overcome those problems. Nine areas (plots) of grassland, each measuring 0.04 m2, were directly labelled with a known activity of either 134Cs or 60Co. Three plots were located on level, un‐poached ground for use as controls and six were located in livestock‐poached areas. Initial surface inventories were documented and then re‐measured on three occasions after rainfall. Inventory changes were converted to estimates of sediment redistribution, which was documented across all poached plots at each re‐measurement. Erosion represented the predominant mechanism, with average soil losses estimated at an equivalent of 0.03 kg m‐2 d‐1 at the first re‐measurement (T1), 0.11 kg m‐2 d‐1 at T2, and 0.18 kg m‐2 d‐1 at T3. Despite assuming erosion would diminish, increasing soil loss is attributed to reduced surface roughness. These findings not only confirm the viability of the tracing technique, but also demonstrate that livestock‐poached areas act as sediment‐sources over timescales of at least a few months after poaching has ceased.

ACS Style

Philip Greenwood; Katrin Meusburger. Documenting soil redistribution on livestock-poached pasture using caesium-134 and cobalt-60 as tracers. Land Degradation & Development 2018, 30, 315 -327.

AMA Style

Philip Greenwood, Katrin Meusburger. Documenting soil redistribution on livestock-poached pasture using caesium-134 and cobalt-60 as tracers. Land Degradation & Development. 2018; 30 (3):315-327.

Chicago/Turabian Style

Philip Greenwood; Katrin Meusburger. 2018. "Documenting soil redistribution on livestock-poached pasture using caesium-134 and cobalt-60 as tracers." Land Degradation & Development 30, no. 3: 315-327.

Journal article
Published: 07 November 2018 in Science of The Total Environment
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Soil transport on fully vegetated land surfaces is typically detachment limited. Rates of soil and nutrient transport, and ultimately long-term landscape evolution, are controlled by processes that supply soil material for entrainment and transport. Despite their on-going nature, many such processes operate at low rates and have not been subject to detailed investigation. We present preliminary findings from a prototype tracing approach to quantify one such process; namely to determine the relative mobility of sediment from earthworm casts on a fully vegetated hillslope surface. A 0.6 ∗ 0.5 m bounded area of pasture was prepared and fifteen intact earthworm casts representing 203 g of soil were labelled with an estimated 216 Bq of caesium-134 (134Cs) activity and evenly distributed across the upslope half of the plot, 0.3–0.6 m from the downslope outlet. A further 15 intact casts representing 190.7 g of soil were labelled with 224 Bq of cobalt-60 (60Co) activity and distributed between 0.3 and 0.0 m from the same outlet. All labelled casts were exposed to natural weather events over 76 days, during which time 186.3 mm of rainfall generated 16 runoff samples. A mass balance was used to partition labelled sediment from the unlabelled material. A total of 27.17 g of 60Co-labelled casts, equivalent to 14.2% of the original mass deployed, was recovered from a distance of ≤0.3 m from their original locations. In contrast, 8.77 g of 134Cs-labelled casts, equivalent to 4.3% of the original mass deployed, was recovered from a distance ≥0.3 m from their original locations. Some runoff-derived samples recorded an over-enrichment of radionuclide material, which suggests that intact casts may sorb more material than the original assumption predicts. Ways in which sorption can be more accurately quantified to improve the accuracy of the tracing approach are outlined.

ACS Style

Philip Greenwood; Stephen Haley; Markus Zehringer; Nikolaus J. Kuhn. A prototype tracing-technique to assess the mobility of dispersed earthworm casts on a vegetated hillslope using caesium-134 and cobalt-60. Science of The Total Environment 2018, 654, 1 -9.

AMA Style

Philip Greenwood, Stephen Haley, Markus Zehringer, Nikolaus J. Kuhn. A prototype tracing-technique to assess the mobility of dispersed earthworm casts on a vegetated hillslope using caesium-134 and cobalt-60. Science of The Total Environment. 2018; 654 ():1-9.

Chicago/Turabian Style

Philip Greenwood; Stephen Haley; Markus Zehringer; Nikolaus J. Kuhn. 2018. "A prototype tracing-technique to assess the mobility of dispersed earthworm casts on a vegetated hillslope using caesium-134 and cobalt-60." Science of The Total Environment 654, no. : 1-9.

Journal article
Published: 04 June 2018 in Journal of Soils and Sediments
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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. 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. 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. 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.

ACS Style

Philip Greenwood; Patrick Baumann; Simon Pulley; Nikolaus J. Kuhn. The invasive alien plant, Impatiens glandulifera (Himalayan Balsam), and increased soil erosion: causation or association? Case studies from a river system in Switzerland and the UK. Journal of Soils and Sediments 2018, 18, 3463 -3477.

AMA Style

Philip Greenwood, Patrick Baumann, Simon Pulley, Nikolaus J. Kuhn. The invasive alien plant, Impatiens glandulifera (Himalayan Balsam), and increased soil erosion: causation or association? Case studies from a river system in Switzerland and the UK. Journal of Soils and Sediments. 2018; 18 (12):3463-3477.

Chicago/Turabian Style

Philip Greenwood; Patrick Baumann; Simon Pulley; Nikolaus J. Kuhn. 2018. "The invasive alien plant, Impatiens glandulifera (Himalayan Balsam), and increased soil erosion: causation or association? Case studies from a river system in Switzerland and the UK." Journal of Soils and Sediments 18, no. 12: 3463-3477.

Article
Published: 22 December 2017 in Earth Surface Processes and Landforms
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Site-average values of local gradient, defined as the steepest slope angle measured at a point, are a powerful predictor of long-term rates of soil loss as measured by erosion pins on the non-channel floor portions of ten badland study sites in the Karoo area of South Africa. Local gradient may be easily measured using a smartphone clinometer. The successful use of local gradient here is in strong contrast to the previous failure of other site-specific attributes, including other measures of gradient and relief, to explain between-site variation in erosion rate on these study sites. Each measurement of local gradient may be thought of as a sample of the site's microtopography. Microrelief is a strong determinant of the emergent patterns of inter-channel overland flow, and hence of the patterns of inter-channel erosion by flow. Local gradient changes most rapidly during the initial stages of channel incision. When channels are established, local gradient changes more slowly leading to almost-parallel retreat of channel sidewalls. A sensitivity analysis suggests that measurements of local gradient are not all equal with regard to prediction of long-term erosion rate. A greater share of predictive power is contributed by measurements made on very steep or vertical channel side wall areas, and a lesser share is contributed by measurements made on interfluves.

ACS Style

David Favis-Mortlock; John Boardman; Ian Foster; Philip Greenwood. ‘Local gradient’ and between‐site variability of erosion rate on badlands in the Karoo, South Africa. Earth Surface Processes and Landforms 2017, 43, 871 -883.

AMA Style

David Favis-Mortlock, John Boardman, Ian Foster, Philip Greenwood. ‘Local gradient’ and between‐site variability of erosion rate on badlands in the Karoo, South Africa. Earth Surface Processes and Landforms. 2017; 43 (4):871-883.

Chicago/Turabian Style

David Favis-Mortlock; John Boardman; Ian Foster; Philip Greenwood. 2017. "‘Local gradient’ and between‐site variability of erosion rate on badlands in the Karoo, South Africa." Earth Surface Processes and Landforms 43, no. 4: 871-883.

Review
Published: 06 December 2017 in Cobalt
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The chapter firstly outlines the global crisis concerning accelerated soil erosion, the implications that this could have on longer-term food security and ways that soil loss has been quantified originally through catchment-scale monitoring but with a recent shift toward the use of sediment tracers. It then briefly reviews some of the most commonly used tracers in sedimentation studies, before focusing on artificial, gamma-emitting radionuclides, and in particular, on Cobalt-60 (Co-60). Some historical background information on previous uses of Co-60 are then provided, and the suite of key environmental characteristics that, from the perspective of studies in hydrology and geomorphology, make Co-60 a potentially attractive candidate for fine-sediment tracing. The chapter then outlines and reviews three ways in which Co-60 has been experimentally applied in varying erosion and sedimentation scenarios where most of the more commonly used tracers would be unsuitable or would lack the level of sensitivity needed to return meaningful data. It then outlines some of the notable drawbacks associated with using Co-60, before highlighting refinements and prospects for future work. The chapter finally concludes by evaluating the versatility and efficacy of Co-60 as a fine-sediment tracer.

ACS Style

Philip Greenwood. A Review of the Radionuclide, Cobalt-60, as a Fine-Sediment Tracer. Cobalt 2017, 1 .

AMA Style

Philip Greenwood. A Review of the Radionuclide, Cobalt-60, as a Fine-Sediment Tracer. Cobalt. 2017; ():1.

Chicago/Turabian Style

Philip Greenwood. 2017. "A Review of the Radionuclide, Cobalt-60, as a Fine-Sediment Tracer." Cobalt , no. : 1.

Journal article
Published: 01 January 2016 in Agriculture, Ecosystems & Environment
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Climate change is expected to affect both the amount of global crop production, and annual variability in food supply. Agriculture is a major source of greenhouse gas emissions, but also considered to mitigate climate change. Conservation tillage, as a climate-smart agricultural practice, is repeatedly reported to mitigate net greenhouse gas emissions by increasing soil organic carbon (SOC). However, with reduced tillage, less litter is moved from the surface deeper into the soil profile, so SOC increase is very likely constrained to topsoil layers. Further adaptation benefits, such as increasing crop yield and resilience to famine, have recently been questioned after averaging yields from field studies. However, such global averaging masks the geographic extent individual studies apply to. This paper attempts a holistic regional analysis on the benefits of conservation tillage, in particular its fundamental principle no-tillage (NT), on the Chinese Loess Plateau. Based on a review of almost 20 years of conservation tillage plot experiments, the potential of NT to increase SOC stocks and to adapt to lower but more variable rainfall in the future has been assessed. The results show that the difference of total SOC stocks between NT and CT decreased with soil depth, confirming that the SOC benefits of NT are concentrated to the immediate topsoil still subject to direct seeding. The topsoil achieved maximum SOC stocks after about 10 years of NT. Crop yields from NT increased by up to 20% for years with average and below average precipitation, demonstrating the advantages of NT in stabilizing crop yields in dry years. However, the results in previous reports are not weighted by the actual spatial extent of drylands and humid regions after counting individual plot studies. As a consequence of such global and unweighted averaging, the benefits from NT to increase SOC stocks are likely to misrepresent the actual impact. Therefore, given the size of the Loess Plateau and its relevance for food security in China, our analysis illustrates the need to assess the benefits of a tillage and residue management system for each combination of eco-region and farming practice, weighted by their area and the affected population, rather than just using a global average for policy development on sustainable productivity.

ACS Style

Nikolaus Kuhn; Yaxian Hu; Lena Bloemertz; Jin He; Hongwen Li; Philip Greenwood. Conservation tillage and sustainable intensification of agriculture: regional vs. global benefit analysis. Agriculture, Ecosystems & Environment 2016, 216, 155 -165.

AMA Style

Nikolaus Kuhn, Yaxian Hu, Lena Bloemertz, Jin He, Hongwen Li, Philip Greenwood. Conservation tillage and sustainable intensification of agriculture: regional vs. global benefit analysis. Agriculture, Ecosystems & Environment. 2016; 216 ():155-165.

Chicago/Turabian Style

Nikolaus Kuhn; Yaxian Hu; Lena Bloemertz; Jin He; Hongwen Li; Philip Greenwood. 2016. "Conservation tillage and sustainable intensification of agriculture: regional vs. global benefit analysis." Agriculture, Ecosystems & Environment 216, no. : 155-165.

Journal article
Published: 16 October 2015 in Hydrology
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The use of sediment settling velocity based on mineral grain size distribution in erosion models ignores the effects of aggregation on settling velocity. The alternative approach, wet-sieved aggregate size distribution, on the other hand, cannot represent all destructive processes that eroded soils may experience under impacting raindrops. Therefore, without considering raindrop impact, both methods may lead to biased predictions of the redistribution of sediment and associated substances across landscapes. Rainfall simulation is an effective way to simulate natural raindrop impact under controlled laboratory conditions. However, very few methods have been developed to integrate rainfall simulation with the settling velocity of eroded sediment. This study aims to develop a new proxy, based on rainfall simulation, in order to identify the actual settling velocity distribution of aggregated sediment. A combined Raindrop Aggregate Destruction Test-Settling Tube (RADT-ST) approach was developed to (1) simulate aggregate destruction under a series of simulated rainfalls; and (2) measure the actual settling velocity distribution of destroyed aggregates. Mean Weight Settling Velocity (MWSV) of aggregates was used to investigate settling behaviors of different soils as rainfall kinetic energy increased. The results show the settling velocity of silt-rich raindrop impacted aggregates is likely to be underestimated by at least six times if based on mineral grain size distribution. The RADT-ST designed in this study effectively captures the effects of aggregation on settling behavior. The settling velocity distribution should be regarded as an evolving, rather than steady state parameter during erosion events. The combined RADT-ST approach is able to generate the quasi-natural sediment under controlled simulated rainfall conditions and is adequately sensitive to measure actual settling velocities of differently aggregated soils. This combined approach provides an effective tool to improve the parameterization of settling velocity input for erosion models.

ACS Style

Liangang Xiao; Yaxian Hu; Philip Greenwood; Nikolaus J. Kuhn. A Combined Raindrop Aggregate Destruction Test-Settling Tube (RADT-ST) Approach to Identify the Settling Velocity of Sediment. Hydrology 2015, 2, 176 -192.

AMA Style

Liangang Xiao, Yaxian Hu, Philip Greenwood, Nikolaus J. Kuhn. A Combined Raindrop Aggregate Destruction Test-Settling Tube (RADT-ST) Approach to Identify the Settling Velocity of Sediment. Hydrology. 2015; 2 (4):176-192.

Chicago/Turabian Style

Liangang Xiao; Yaxian Hu; Philip Greenwood; Nikolaus J. Kuhn. 2015. "A Combined Raindrop Aggregate Destruction Test-Settling Tube (RADT-ST) Approach to Identify the Settling Velocity of Sediment." Hydrology 2, no. 4: 176-192.

Journal article
Published: 15 October 2015 in Geographica Helvetica
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ACS Style

P. Greenwood; M. Hoelzle; N. J. Kuhn. Introduction to the special issue of Geographica Helvetica: "Mapping, measuring and modeling in geomorphology". Geographica Helvetica 2015, 70, 311 -313.

AMA Style

P. Greenwood, M. Hoelzle, N. J. Kuhn. Introduction to the special issue of Geographica Helvetica: "Mapping, measuring and modeling in geomorphology". Geographica Helvetica. 2015; 70 (4):311-313.

Chicago/Turabian Style

P. Greenwood; M. Hoelzle; N. J. Kuhn. 2015. "Introduction to the special issue of Geographica Helvetica: "Mapping, measuring and modeling in geomorphology"." Geographica Helvetica 70, no. 4: 311-313.

Journal article
Published: 15 June 2015 in Geographica Helvetica
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Raindrop impact and subsequent aggregate breakdown can potentially change the movement behaviour of soil fractions and thus alter their transport distances when compared against non-impacted aggregates. In a given water layer, the transport distances of eroded soil fractions, and thus that of the associated substances across landscapes, such as soil organic carbon (SOC) and phosphorous, are determined by the settling velocities of the eroded soil fractions. However, using mineral size distribution to represent the settling velocities of soil fractions, as often applied in current erosion models, would ignore the potential influence of aggregation on the settling behaviour of soil fractions. The destructive effects of raindrops impacting onto aggregates are also often neglected in current soil erosion models. Therefore, the objective of this study is to develop a proxy method to effectively simulate aggregate breakdown under raindrop impact, and further identify the settling velocity of eroded sediment and the associated SOC. Two agricultural soils with different sandy and silty loam textures were subjected to rainfall using a raindrop aggregate destruction device (RADD). The aggregates sustained after raindrop impact were fractionated by a settling tube into six different classes according to their respective settling velocities. The same mass amount of bulk soil of each soil type was also dispersed and sieved into the same six classes, to form a comparison in size distribution. The SOC content was measured for each settled and dispersed class. Our results show the following: (1) for an aggregated soil, applying dispersed mineral grain size distribution, rather than its actual aggregate distribution, to soil erosion models would lead to a biased estimation on the redistribution of eroded sediment and SOC; (2) the RADD designed in this study effectively captures the effects of raindrop impact on aggregate destruction and is thus able to simulate the quasi-natural sediment spatial redistribution; (3) further RADD tests with more soils under standard rainfall combined with local rainfalls are required to optimize the method.

ACS Style

L. Xiao; Y. Hu; P. Greenwood; N. J. Kuhn. The use of a raindrop aggregate destruction device to evaluate sediment and soil organic carbon transport. Geographica Helvetica 2015, 70, 167 -174.

AMA Style

L. Xiao, Y. Hu, P. Greenwood, N. J. Kuhn. The use of a raindrop aggregate destruction device to evaluate sediment and soil organic carbon transport. Geographica Helvetica. 2015; 70 (2):167-174.

Chicago/Turabian Style

L. Xiao; Y. Hu; P. Greenwood; N. J. Kuhn. 2015. "The use of a raindrop aggregate destruction device to evaluate sediment and soil organic carbon transport." Geographica Helvetica 70, no. 2: 167-174.

Journal article
Published: 23 February 2015 in Geographica Helvetica
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Alpine and mountain slopes represent important pathways that link high-altitude grazing areas to meadows and rangelands at lower elevations. Given the often acute gradients associated with such environments, they potentially represent highly efficient runoff conveyance routes that facilitate the downslope movement of runoff and associated material during erosion events. Many such slopes host series of small steps, or "terracettes". The juxtaposition of terracettes against the natural downslope flow path of non-complex slopes leads us to hypothesise that they may influence typical hillslope processes by intercepting or capturing surface runoff. Here we report preliminary results and some tentative conclusions from ongoing work to explore this possibility. Google Earth was used to initially identify a ca. 400 m2 well-developed terracette system situated on a west-facing slope with gradients ranging from 25 to 40° (46 to 84 %). A digital elevation model (DEM) of the terracettes was constructed using spatial data taken from a relevant section of topographic map. The DEM was then queried using a flow-accumulation algorithm and the results displayed in a geographic information system. The output data provided "proof of concept" that terracettes can capture surface runoff. The generation of empirical data from a series of rainfall/runoff simulations performed on the same section of terracettes supports this finding. Results from both work components indicate that sections of a terracette system may intercept runoff and could act as preferential flow pathways. By contrast, some sections appeared to act as depositional sites. We cautiously predict that these areas could act as retention zones for the temporary storage of runoff-associated substances. Greater understanding of the exact influence of terracettes on surface hydrology in steep-sloping and subalpine environments could benefit the future management of grazing and rangelands in such areas.

ACS Style

P. Greenwood; S. Kuonen; W. Fister; N. J. Kuhn. The influence of terracettes on the surface hydrology of steep-sloping and subalpine environments: some preliminary findings. Geographica Helvetica 2015, 70, 63 -73.

AMA Style

P. Greenwood, S. Kuonen, W. Fister, N. J. Kuhn. The influence of terracettes on the surface hydrology of steep-sloping and subalpine environments: some preliminary findings. Geographica Helvetica. 2015; 70 (1):63-73.

Chicago/Turabian Style

P. Greenwood; S. Kuonen; W. Fister; N. J. Kuhn. 2015. "The influence of terracettes on the surface hydrology of steep-sloping and subalpine environments: some preliminary findings." Geographica Helvetica 70, no. 1: 63-73.

Journal article
Published: 25 November 2014 in Earth Surface Processes and Landforms
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In a review of the role of plants in river systems, Gurnell (2014) explains how living riparian vegetation can exert physical controls that enable it to modify and manipulate many fluvial processes. Those traits, in combination with their tendency to speed up the recovery of river systems between extreme flow events through their stabilising influence, imply that plants may act as ‘river system engineers’. In this sense, vegetation may be important in attenuating erosion during high flow and stabilising river features both during and after extreme flow conditions. This article is protected by copyright. All rights reserved.

ACS Style

Philip Greenwood; Nikolaus J. Kuhn. Earth Surface Exchanges (ESEX) Commentary on ‘Plants as river system engineers’ by A. Gurnell.Earth Surface Processes and Landforms39: 4-25, 2014. DOI 10.1002/esp.3397. Earth Surface Processes and Landforms 2014, 40, 131 -134.

AMA Style

Philip Greenwood, Nikolaus J. Kuhn. Earth Surface Exchanges (ESEX) Commentary on ‘Plants as river system engineers’ by A. Gurnell.Earth Surface Processes and Landforms39: 4-25, 2014. DOI 10.1002/esp.3397. Earth Surface Processes and Landforms. 2014; 40 (1):131-134.

Chicago/Turabian Style

Philip Greenwood; Nikolaus J. Kuhn. 2014. "Earth Surface Exchanges (ESEX) Commentary on ‘Plants as river system engineers’ by A. Gurnell.Earth Surface Processes and Landforms39: 4-25, 2014. DOI 10.1002/esp.3397." Earth Surface Processes and Landforms 40, no. 1: 131-134.

Journal article
Published: 20 December 2013 in Journal of Soils and Sediments
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The invasive plant, Impatiens glandulifera (common English name: Himalayan Balsam), is now found in many river catchments in most European countries. Its preference for damp, nutrient-rich soils, along with its intolerance to cold weather and rapid dieback, has implicated it in promoting soil erosion along the riparian zone. Despite the implication, its influence on the sediment dynamics of river systems remains unconfirmed. This communication reports the preliminary findings of ongoing work to investigate a possible link between I. glandulifera and accelerated erosion rates in inland river systems.

ACS Style

Philip Greenwood; Nikolaus J. Kuhn. Does the invasive plant, Impatiens glandulifera, promote soil erosion along the riparian zone? An investigation on a small watercourse in northwest Switzerland. Journal of Soils and Sediments 2013, 14, 637 -650.

AMA Style

Philip Greenwood, Nikolaus J. Kuhn. Does the invasive plant, Impatiens glandulifera, promote soil erosion along the riparian zone? An investigation on a small watercourse in northwest Switzerland. Journal of Soils and Sediments. 2013; 14 (3):637-650.

Chicago/Turabian Style

Philip Greenwood; Nikolaus J. Kuhn. 2013. "Does the invasive plant, Impatiens glandulifera, promote soil erosion along the riparian zone? An investigation on a small watercourse in northwest Switzerland." Journal of Soils and Sediments 14, no. 3: 637-650.