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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.
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 StylePhilip 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 StylePhilip 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.
The sandy croplands in the Free State have been identified as one of the main dust sources in South Africa. The aim of this study was to investigate the occurrence and strength of physical soil crusts on cropland soils in the Free State, to identify the rainfall required to form a stable crust, and to test their impact on dust emissions. Crust strength was measured using a fall cone penetrometer and a torvane, while laboratory rainfall simulations were used to form experimental crusts. Dust emissions were measured with a Portable In-Situ Wind Erosion Laboratory (PI-SWERL). The laboratory rainfall simulations showed that stable crusts could be formed by 15 mm of rainfall. The PI-SWERL experiments illustrated that the PM10 emission flux of such crusts is between 0.14% and 0.26% of that of a non-crusted Luvisol and Arenosol, respectively. The presence of abraders on the crust can increase the emissions up to 4% and 8% of the non-crusted dust flux. Overall, our study shows that crusts in the field are potentially strong enough to protect the soil surfaces against wind erosion during a phase of the cropping cycle when the soil surface is not protected by plants.
Heleen C. Vos; Wolfgang Fister; Frank D. Eckardt; Anthony R. Palmer; Nikolaus J. Kuhn. Physical Crust Formation on Sandy Soils and Their Potential to Reduce Dust Emissions from Croplands. Land 2020, 9, 503 .
AMA StyleHeleen C. Vos, Wolfgang Fister, Frank D. Eckardt, Anthony R. Palmer, Nikolaus J. Kuhn. Physical Crust Formation on Sandy Soils and Their Potential to Reduce Dust Emissions from Croplands. Land. 2020; 9 (12):503.
Chicago/Turabian StyleHeleen C. Vos; Wolfgang Fister; Frank D. Eckardt; Anthony R. Palmer; Nikolaus J. Kuhn. 2020. "Physical Crust Formation on Sandy Soils and Their Potential to Reduce Dust Emissions from Croplands." Land 9, no. 12: 503.
The authors wish to make the following corrections to this paper
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 StyleJuliane 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 StyleJuliane 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.
Gravity affects sedimentation of particles suspended in water and gases in two ways: directly by the gravitational force that pulls a particle towards the surface and indirectly by the flow conditions of water or gas around the particles. The latter create a drag which is affected by the settling velocity. Consequently, drag coefficients observed on Earth sand-sized particles cannot be used on Mars because they are likely to overestimate the drag generated by the turbulent flow around the particle on Earth may shift into a more laminar state that generates lower drag. The effect of gravity on settling velocity is not linearly related to particle size, which may affect the sorting of the sand grains deposited from running water. Experiments carried out during parabolic flights at reduced gravity indicate that the potential error in particle settling and sorting is significant, i.e. leading to wrong interpretations of the flow velocities at the time of deposition. This in turn has implications for reconstruction of Martian environmental conditions from rock textures determined from close-up imagery. This study uses computational fluid dynamics (CFD) modelling to independently assess the effect of gravity on sediment settling velocities and sediment sorting. The CFD modelling also offers a wide capability for reconstruction sedimentation on Mars and thus supports the reconstruction of it’s environmental past, as well as the search for traces of life.
Nikolaus J. Kuhn; Federica Trudu. Computational Fluid Dynamics modelling of sedimentation on Mars. 2020, 1 .
AMA StyleNikolaus J. Kuhn, Federica Trudu. Computational Fluid Dynamics modelling of sedimentation on Mars. . 2020; ():1.
Chicago/Turabian StyleNikolaus J. Kuhn; Federica Trudu. 2020. "Computational Fluid Dynamics modelling of sedimentation on Mars." , no. : 1.
In this study, the potential effect of the selective transport and deposition by interrill erosion on the spatial distribution of eroded soil and associated soil organic (SOC) and inorganic carbon (SIC) in carbonate-rich soils was investigated in Mediterranean cultivated Calcisols. Particular attention was paid to the role of calcium carbonate in the stabilization of SOC and its impact on soil structure and the settling behavior of soil particles in suspension. The settling velocity is a key variable in controlling the transport and fate of eroded sediment and sediment-associated carbon, which accounts for soil particle / aggregate size and density. The objectives were to analyze the settling behavior of cultivated soils at two contrasting slope positions, representative of erosion and deposition sites, in an interrill area and compare with those of uncultivated and undisturbed soils (not affected by deposition or erosion processes). Besides we examined the distribution of SOC and SIC associated with different particle size classes. Soils were fractionated into five size classes (>250, 125–250, 63–125, 32–63 and ≤32 μm) using a settling tube procedure and carbon contents (SOC and SIC, %) were measured at each settling size classes. The results indicated that the particle size selectivity of interrill erosion affects the distribution of soil particles and associated SOC and SIC spatial variability. As a result of erosion processes, cultivated soil at the upper part of the slope was enriched in finer fractions compared to the lower part where mainly coarse particles were deposited and the finer material was transported and washed out. Cultivation leads to a depletion of SOC and of the >250 μm fraction in comparison with uncultivated and undisturbed soil, where the SOC content was two times higher than in cultivated soil. Lighter and smaller settling size classes (≤63 μm) had the highest SOC content in uncultivated and cultivated downslope soils. This is contrary to what occurs with SIC that acts as a cementing agent and promotes aggregation formation affecting soil structure. Therefore, sand-sized and silt-sized carbonates were accumulated in coarser size fractions in these soils, mainly in downslope positions. This study provides a first insight into the role of selective processes by interrill erosion and their impact on soil organic/inorganic carbon distribution affected by different particle selective transport process, soil aggregate size distribution and associated carbon in Mediterranean agroecosystems.
Laura Quijano; Nikolaus J. Kuhn; Ana Navas. Effects of interrill erosion on the distribution of soil organic and inorganic carbon in different sized particles of Mediterranean Calcisols. Soil and Tillage Research 2019, 196, 104461 .
AMA StyleLaura Quijano, Nikolaus J. Kuhn, Ana Navas. Effects of interrill erosion on the distribution of soil organic and inorganic carbon in different sized particles of Mediterranean Calcisols. Soil and Tillage Research. 2019; 196 ():104461.
Chicago/Turabian StyleLaura Quijano; Nikolaus J. Kuhn; Ana Navas. 2019. "Effects of interrill erosion on the distribution of soil organic and inorganic carbon in different sized particles of Mediterranean Calcisols." Soil and Tillage Research 196, no. : 104461.
Savannas comprise a major component of the Earth system and contribute ecosystem services and functions essential to human livelihoods. Monitoring spatial and temporal trends in savanna vegetation and understanding change drivers is therefore crucial. Widespread greening has been identified across southern Africa; yet its drivers and manifestations on the ground remain ambiguous. This study removes the effects of precipitation on an NDVI time-series, thereby identifying trends not driven by rainfall. It utilizes the significant correlation between vegetation and precipitation as captured using MODIS and rainfall estimates. A linear regression between variables was used to derive its residual (corrected) time-series, and the rate and spatial extent of trends were evaluated in relation to biomes. A random sample-based qualitative interpretation of high spatial resolution imagery was then used to evaluate the nature of the trend on the ground. 23.25% of the country, including all biomes exhibited positive trends. We propose that greening may be related to a reduction in woody species richness, loss of the large trees and a shift towards drought tolerant shrub species, as has been shown in other sub-Saharan environments. 3.23% of the country exhibited negative trends, which were mostly associated with more humid (forested) regions pointing to deforestation as a cause; these manifested as vegetation clearing, identifiable using high resolution multi-temporal imagery. Greening trends could not be identified using this approach; instead, they point to the occurrence of gradual vegetation change caused by indirect drivers.
Vladimir R. Wingate; Stuart R. Phinn; Nikolaus Kuhn. Mapping precipitation-corrected NDVI trends across Namibia. Science of The Total Environment 2019, 684, 96 -112.
AMA StyleVladimir R. Wingate, Stuart R. Phinn, Nikolaus Kuhn. Mapping precipitation-corrected NDVI trends across Namibia. Science of The Total Environment. 2019; 684 ():96-112.
Chicago/Turabian StyleVladimir R. Wingate; Stuart R. Phinn; Nikolaus Kuhn. 2019. "Mapping precipitation-corrected NDVI trends across Namibia." Science of The Total Environment 684, no. : 96-112.
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.
Juliane Krenz; Philip Greenwood; Nikolaus J. Kuhn. Soil Degradation Mapping in Drylands Using Unmanned Aerial Vehicle (UAV) Data. Soil Systems 2019, 3, 33 .
AMA StyleJuliane 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 StyleJuliane Krenz; Philip Greenwood; Nikolaus J. Kuhn. 2019. "Soil Degradation Mapping in Drylands Using Unmanned Aerial Vehicle (UAV) Data." Soil Systems 3, no. 2: 33.
Valerio Amici; Giovanni Bacaro; Francesco Brogi; Adolfo Calvo-Cases; Yolanda Cantón; Sonia Chamizo; Michael Daniels; Maurizio Del Monte; Marta Della Seta; Hazel Faulkner; Francesc Gallart; José M. García-Ruiz; Antonio J.T. Guerra; Veena Joshi; Milica Kašanin-Grubin; Juliane Krenz; Nikolaus J. Kuhn; Caroline Le Bouteiller; Simona Maccherini; Michela Marignani; Juan F. Martínez-Murillo; Mariano Moreno-De Las Heras; Estela Nadal-Romero; Garry Paterson; Jean Poesen; Emilio Rodríguez-Caballero; Mauro Rossi; Elisa Santi; Jeffrey Shellberg; Albert Solé-Benet; Zheng’An Su; Enrico Tordoni; Dino Torri; Francesco Troiani; Francesca Vergari; Wojciech Zgłobicki. List of Contributors. Badlands Dynamics in a Context of Global Change 2018, 1 .
AMA StyleValerio Amici, Giovanni Bacaro, Francesco Brogi, Adolfo Calvo-Cases, Yolanda Cantón, Sonia Chamizo, Michael Daniels, Maurizio Del Monte, Marta Della Seta, Hazel Faulkner, Francesc Gallart, José M. García-Ruiz, Antonio J.T. Guerra, Veena Joshi, Milica Kašanin-Grubin, Juliane Krenz, Nikolaus J. Kuhn, Caroline Le Bouteiller, Simona Maccherini, Michela Marignani, Juan F. Martínez-Murillo, Mariano Moreno-De Las Heras, Estela Nadal-Romero, Garry Paterson, Jean Poesen, Emilio Rodríguez-Caballero, Mauro Rossi, Elisa Santi, Jeffrey Shellberg, Albert Solé-Benet, Zheng’An Su, Enrico Tordoni, Dino Torri, Francesco Troiani, Francesca Vergari, Wojciech Zgłobicki. List of Contributors. Badlands Dynamics in a Context of Global Change. 2018; ():1.
Chicago/Turabian StyleValerio Amici; Giovanni Bacaro; Francesco Brogi; Adolfo Calvo-Cases; Yolanda Cantón; Sonia Chamizo; Michael Daniels; Maurizio Del Monte; Marta Della Seta; Hazel Faulkner; Francesc Gallart; José M. García-Ruiz; Antonio J.T. Guerra; Veena Joshi; Milica Kašanin-Grubin; Juliane Krenz; Nikolaus J. Kuhn; Caroline Le Bouteiller; Simona Maccherini; Michela Marignani; Juan F. Martínez-Murillo; Mariano Moreno-De Las Heras; Estela Nadal-Romero; Garry Paterson; Jean Poesen; Emilio Rodríguez-Caballero; Mauro Rossi; Elisa Santi; Jeffrey Shellberg; Albert Solé-Benet; Zheng’An Su; Enrico Tordoni; Dino Torri; Francesco Troiani; Francesca Vergari; Wojciech Zgłobicki. 2018. "List of Contributors." Badlands Dynamics in a Context of Global Change , no. : 1.
Afforestation is a strategy to sequester atmospheric carbon in the terrestrial system and to enhance ecosystem services. Iceland's large areas of formerly vegetated and now degraded ecosystems therefore have a high potential to act as carbon sinks. Consequently, the ecological restoration of these landscape systems is part of climate mitigation programs supported by the Icelandic government. The aim of this study was to explore the change of the soil organic carbon (SOC) pools and to estimate the SOC sequestration potential during the re-establishment of birch forest on severely degraded land. Differently aged afforested mountain birch sites (15, 20, 25 and 50 years) were compared with sites of severely degraded land, naturally growing remnants of mountain birch woodland and grasslands which were re-vegetated using fertilizer and grass seeds 50 years ago. The soil was sampled to estimate the SOC stocks and for physical fractionation to characterize the quality of the SOC. The results of our study show that the severely degraded soils can potentially sequester an additional 20 t C ha−1 (0–30 cm) to reach the SOC stock of naturally growing birch woodlands. After 50 years of birch growth, the SOC stock is lower than that of naturally growing birch woodland. Hence, afforested stands can sequester additional SOC after 50 years of birch growth. The SOC fractionation revealed that at all tested sites most of the carbon was stored in the
Matthias Hunziker; Olafur Arnalds; Nikolaus J. Kuhn. Evaluating the carbon sequestration potential of volcanic soils in South Iceland after birch afforestation. 2018, 2018, 1 -33.
AMA StyleMatthias Hunziker, Olafur Arnalds, Nikolaus J. Kuhn. Evaluating the carbon sequestration potential of volcanic soils in South Iceland after birch afforestation. . 2018; 2018 ():1-33.
Chicago/Turabian StyleMatthias Hunziker; Olafur Arnalds; Nikolaus J. Kuhn. 2018. "Evaluating the carbon sequestration potential of volcanic soils in South Iceland after birch afforestation." 2018, no. : 1-33.
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.
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 StylePhilip 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 StylePhilip 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.
Soil degradation is a major threat for farmers of semi-arid north-central Namibia. Soil conservation practices can be promoted by the development of soil quality (SQ) evaluation toolboxes that provide ways to evaluate soil degradation. However, such toolboxes must be adapted to local conditions to reach farmers. Based on qualitative (interviews and soil descriptions) and quantitative (laboratory analyses) data, we developed a set of SQ indicators relevant for our study area that integrates farmers' field experiences (FFEs) and technical knowledge. We suggest using participatory mapping to delineate soil units (Oshikwanyama soil units, KwSUs) based on FFEs, which highlight mostly soil properties that integrate long-term productivity and soil hydrological characteristics (i.e. internal SQ). The actual SQ evaluation of a location depends on the KwSU described and is thereafter assessed by field soil texture (i.e. chemical fertility potential) and by soil colour shade (i.e. SOC status). This three-level information aims to reveal SQ improvement potential by comparing, for any location, (a) estimated clay content against median clay content (specific to KwSU) and (b) soil organic status against calculated optimal values (depends on clay content). The combination of farmers' and technical assessment cumulates advantages of both systems of knowledge, namely the integrated long-term knowledge of the farmers and a short- and medium-term SQ status assessment. The toolbox is a suggestion for evaluating SQ and aims to help farmers, rural development planners and researchers from all fields of studies understanding SQ issues in north-central Namibia. This suggested SQ toolbox is adapted to a restricted area of north-central Namibia, but similar tools could be developed in most areas where small-scale agriculture prevails.
Brice Prudat; Lena Bloemertz; Nikolaus J. Kuhn. Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge. SOIL 2018, 4, 47 -62.
AMA StyleBrice Prudat, Lena Bloemertz, Nikolaus J. Kuhn. Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge. SOIL. 2018; 4 (1):47-62.
Chicago/Turabian StyleBrice Prudat; Lena Bloemertz; Nikolaus J. Kuhn. 2018. "Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge." SOIL 4, no. 1: 47-62.
The increase of summer temperatures and a prolonged growing season increase the potential for agricultural land use for subarctic agriculture. Nevertheless, land use at borderline ecotones is influenced by more factors than temperature and the length of the growing season, for example soil quality, as the increasing lengths of dry periods during vegetation season can diminish land use potential. Hence, this study focuses on the quality of the soil resource as possible limiting factor for land use intensification in southern Greenland. Physical and chemical soil properties of cultivated grasslands, reference sites and semi-natural birch and grassland sites were examined to develop a soil quality index and to identify the suitability of soils for a sustainable intensification and expansion of the agriculture. The study revealed that soils in the study area are generally characterized by a low effective cation exchange capacity (CECeff) (3.7 ± 5.0 meq 100 g−1), low pH CaCl2 (4.6 ± 0.4) and low clay and silt content (3.0 ± 1.0% and 38.2 ± 4.7%, respectively). Due to the high amount of coarse fraction (59.1 ± 5.8%) and the low amount of soil nutrients, an increasing threat of dry spells for soils and yield could be identified. Further, future land use intensification and expansion bears a high risk for concomitant effects, namely further soil acidification, nutrient leaching and soil degradation processes. However, results of the soil quality index also indicate that sites which were already used by the Norseman (980s–1450) show the best suitability for agricultural use. Thus, these areas offer a possibility to expand agricultural land use in southern Greenland.
Chatrina Caviezel; Matthias Hunziker; Nikolaus J. Kuhn. Bequest of the Norseman—The Potential for Agricultural Intensification and Expansion in Southern Greenland under Climate Change. Land 2017, 6, 87 .
AMA StyleChatrina Caviezel, Matthias Hunziker, Nikolaus J. Kuhn. Bequest of the Norseman—The Potential for Agricultural Intensification and Expansion in Southern Greenland under Climate Change. Land. 2017; 6 (4):87.
Chicago/Turabian StyleChatrina Caviezel; Matthias Hunziker; Nikolaus J. Kuhn. 2017. "Bequest of the Norseman—The Potential for Agricultural Intensification and Expansion in Southern Greenland under Climate Change." Land 6, no. 4: 87.
Forest regrowth is an ongoing process in the European Alps. In the Unteralptal, a valley in central Switzerland, landscape characteristics show considerable change toward the encroachment of green alder ( Alnus viridis (Chaix) DC. = Alnus alnobetula (Ehrh.) K. Koch). Initially, green alder was described to grow on moist, north-facing and steep slopes of high geomorphic activity. However, the recent spreading of green alder described in several studies over the alpine arc questions the ecological habitat described in historic literature. Thus, a time series of aerial photographs and a digital elevation model (DEM) with a resolution of 2 m were used to find proxies for green alder encroachment. The cover of “new shrub areas” was analyzed based on relief parameter values and geomorphic landforms. The results show that green alder is spreading on more gentle slopes and well-drained areas, as well as on areas with lower geomorphic activity than anticipated. Thus, the habitat spectrum of green alder is much wider than assumed and encroachment has potentially greater consequences for landscape ecology than expected
Chatrina Caviezel; Matthias Hunziker; Nikolaus J. Kuhn. Green alder encroachment in the European Alps: The need for analyzing the spread of a native-invasive species across spatial data. CATENA 2017, 159, 149 -158.
AMA StyleChatrina Caviezel, Matthias Hunziker, Nikolaus J. Kuhn. Green alder encroachment in the European Alps: The need for analyzing the spread of a native-invasive species across spatial data. CATENA. 2017; 159 ():149-158.
Chicago/Turabian StyleChatrina Caviezel; Matthias Hunziker; Nikolaus J. Kuhn. 2017. "Green alder encroachment in the European Alps: The need for analyzing the spread of a native-invasive species across spatial data." CATENA 159, no. : 149-158.
Shrub encroachment by green alder ( Alnus viridis ) has been an ongoing process in European mountain areas after land abandonment. The invasion of this N 2 -fixing and highly productive plant on former subalpine pastures and meadows changes the properties and interactions in the plant-soil system. In the national carbon inventory, it is assumed that green alder woodlands contain the same amount of SOC (~ 69 t C ha − 1 ) as productive forests due to the lack of data. To explore the rarely studied change of the soil organic carbon (SOC) pools during the shrub establishment, the study used a chronosequence approach by testing pastures in a pre-encroached status and green alder stands with an age of 15, 25, 40 and 90 years, respectively. Besides the estimation of the SOC stock, the soil samples, taken in four different depth layers, were physically fractionated to characterize the quality of the SOC. While pasture grassland contained a median SOC stock (0–30 cm) of 100 t C ha − 1 , the SOC stocks decreased to 81 t C ha − 1 for 40 years old shrub stands. The 90 years old green alder bushes showed the significantly highest C stock in the mineral soil with 174 t C ha − 1 . Green alder encroachment led to an increase of the particulate organic material (POM) in the mineral soil resulting in a high concentration of unprotected carbon. By contrast, a stabilization of the SOC with the mineral soil phase was not visible during green alder establishment. The study concludes that green alder encroachment causes a significant increase of fresh and unprotected carbon in the soil system compared to subalpine pastures, resulting in a significantly higher total SOC stock (+ 74 t C ha − 1 ) after 90 years and a doubling of the potential to leach dissolved organic carbon. At landscape level, the ingrowth and establishment of green alder on abandoned subalpine pastures can therefore influence the terrestrial and aquatic systems. Secondly, the SOC stocks of shrub forests are insufficiently represented in the current National Inventory Report
Matthias Hunziker; Chatrina Caviezel; Nikolaus J. Kuhn. Shrub encroachment by green alder on subalpine pastures: Changes in mineral soil organic carbon characteristics. CATENA 2017, 157, 35 -46.
AMA StyleMatthias Hunziker, Chatrina Caviezel, Nikolaus J. Kuhn. Shrub encroachment by green alder on subalpine pastures: Changes in mineral soil organic carbon characteristics. CATENA. 2017; 157 ():35-46.
Chicago/Turabian StyleMatthias Hunziker; Chatrina Caviezel; Nikolaus J. Kuhn. 2017. "Shrub encroachment by green alder on subalpine pastures: Changes in mineral soil organic carbon characteristics." CATENA 157, no. : 35-46.
Soil degradation is a major threat for farmers of semi-arid north-central Namibia. Soil conservation practices can be promoted by the development of soil quality (SQ) evaluation toolboxes that provide ways to evaluate soil degradation. However, such toolboxes must be adapted to local conditions to reach farmers. Based on qualitative (interviews and soil descriptions) and quantitative (laboratory analyses) data, we developed a set of SQ indicators relevant for our study area that integrate farmers' field experiences (FFE) and technical knowledge. We suggest using participatory mapping to delineate soil units (Oshikwanyama Soil Units, KwSUs) based on FFE, which highlight mostly soil properties that integrate long-term productivity and soil hydrological characteristics (i.e. internal SQ). The actual SQ of a location depends on the KwSU described and is thereafter assessed by field soil texture evaluation (i.e. chemical fertility potential) and by soil colour shade (i.e. SOC status). The resulting information includes internal SQ (KwSU), chemical fertility potential (sand content) and the soil organic carbon content status (colour shade). This three-level information reveals SQ improvement potential and aims to help farmers, rural development planners and researchers from all fields of studies understanding SQ issues in north-central Namibia. This SQ toolbox is adapted to a restricted area of north-central Namibia but similar tools could be developed in most areas where small-scale agriculture prevails.
Brice Prudat; Lena Bloemertz; Nikolaus J. Kuhn. Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge. 2017, 2017, 1 -22.
AMA StyleBrice Prudat, Lena Bloemertz, Nikolaus J. Kuhn. Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge. . 2017; 2017 ():1-22.
Chicago/Turabian StyleBrice Prudat; Lena Bloemertz; Nikolaus J. Kuhn. 2017. "Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge." 2017, no. : 1-22.
Several research projects undertaken by the authors and others over the last 14 years have used fallout and geogenic radionuclides for understanding erosion processes and sediment yield dynamics in South Africa over the last 100–200 years as European settlers colonised the interior plains and plateaux of the country and imported new livestock and farming techniques to the region. These projects have used two fallout radionuclides (210Pb and 137Cs) to date sediments accumulating in reservoirs, farm dams, wetlands, alluvial fans and floodouts and have used other fallout nuclides (7Be) and long-lived geogenic radionuclides (e.g. 40K, 235U) as part of a composite fingerprint exploring contemporary sediment sources and changes to sources through time. While successful in many parts of the world, applying these techniques in Southern Africa has posed a number of challenges often not encountered elsewhere. Here we explore some of the benefits and challenges in using gamma-emitting radionuclides, especially 137Cs, in these landscapes. Benefits include the potential for discriminating gully sidewall from topsoil sources, which has helped to identify contemporary gully systems as sediment conduits, rather than sources, and for providing a time-synchronous marker horizon in a range of sedimentary environments that has helped to develop robust chronologies. Challenges include the spatial variability in soil cover on steep rocky hillslopes, which is likely to challenge assumptions about the uniformity of initial fallout nuclide distribution, the paucity of stable (non-eroding) sites in order to estimate atmospheric fallout inventories, and the limited success of 210Pb dating in some rapidly accumulating high altitude catchments where sediments often comprise significant amounts of sand and gravel. Despite these challenges we present evidence suggesting that the use of gamma-emitting radionuclides can make a significant contribution to our understanding of erosion processes and sediment yield dynamics. Future research highlighted in the conclusion will try to address current challenges and outline new projects established to address them more fully.
Ian D. L. Foster; John Boardman; Adrian L. Collins; Ruth Copeland-Phillips; Nikolaus J. Kuhn; Tim M. Mighall; Simon Pulley; Kate M. Rowntree. The potential for gamma-emitting radionuclides to contribute to an understanding of erosion processes in South Africa. Proceedings of the International Association of Hydrological Sciences 2017, 375, 29 -34.
AMA StyleIan D. L. Foster, John Boardman, Adrian L. Collins, Ruth Copeland-Phillips, Nikolaus J. Kuhn, Tim M. Mighall, Simon Pulley, Kate M. Rowntree. The potential for gamma-emitting radionuclides to contribute to an understanding of erosion processes in South Africa. Proceedings of the International Association of Hydrological Sciences. 2017; 375 ():29-34.
Chicago/Turabian StyleIan D. L. Foster; John Boardman; Adrian L. Collins; Ruth Copeland-Phillips; Nikolaus J. Kuhn; Tim M. Mighall; Simon Pulley; Kate M. Rowntree. 2017. "The potential for gamma-emitting radionuclides to contribute to an understanding of erosion processes in South Africa." Proceedings of the International Association of Hydrological Sciences 375, no. : 29-34.
Woodlands and savannahs provide essential ecosystem functions and services to communities. On the African continent, they are widely utilized and converted to subsistence and intensive agriculture or urbanized. This study investigates changes in land cover over four administrative regions of North Eastern Namibia within the Kalahari woodland savannah biome, covering a total of 107,994 km2. Land cover is mapped using multi-sensor Landsat imagery at decadal intervals from 1975 to 2014, with a post-classification change detection method. The dominant change observed was a reduction in the area of woodland savannah due to the expansion of agriculture, primarily in the form of small-scale cereal and pastoral production. More specifically, woodland savannah area decreased from 90% of the study area in 1975 to 83% in 2004, and then increased to 86% in 2014, while agricultural land increased from 6% to 12% between 1975 and 2014. We assess land cover changes in relation to towns, villages, rivers and roads and find most changes occurred in proximity to these. In addition, we find that most land cover changes occur within land designated as communally held, followed by state protected land. With widespread changes occurring across the African continent, this study provides important data for understanding drivers of change in the region and their impacts on the distribution of woodland savannahs.
Vladimir R. Wingate; Stuart R. Phinn; Nikolaus Kuhn; Lena Bloemertz; Kiran L. Dhanjal-Adams. Mapping Decadal Land Cover Changes in the Woodlands of North Eastern Namibia from 1975 to 2014 Using the Landsat Satellite Archived Data. Remote Sensing 2016, 8, 681 .
AMA StyleVladimir R. Wingate, Stuart R. Phinn, Nikolaus Kuhn, Lena Bloemertz, Kiran L. Dhanjal-Adams. Mapping Decadal Land Cover Changes in the Woodlands of North Eastern Namibia from 1975 to 2014 Using the Landsat Satellite Archived Data. Remote Sensing. 2016; 8 (8):681.
Chicago/Turabian StyleVladimir R. Wingate; Stuart R. Phinn; Nikolaus Kuhn; Lena Bloemertz; Kiran L. Dhanjal-Adams. 2016. "Mapping Decadal Land Cover Changes in the Woodlands of North Eastern Namibia from 1975 to 2014 Using the Landsat Satellite Archived Data." Remote Sensing 8, no. 8: 681.
The net effect of soil erosion by water, as a sink or source of atmospheric carbon dioxide (CO), is determined by the spatial (re-)distribution and stability of eroded soil organic carbon (SOC), and the dynamic replacement of eroded C by the production of new photosynthate. The depositional position of eroded SOC is a function of the transport distances of soil fractions where the SOC is stored. In theory, the transport distances of soil fractions are related to their settling velocities under given flow conditions. Yet, very few field investigations have been conducted to examine the actual movement of eroded soil fractions along hillslopes, let alone the re-distribution pattern of SOC fractions. Eroding sandy soils and sediment were sampled after a series of rainfall events along a slope on a freshly seeded cropland in Jutland, Denmark. All the soil samples were fractionated into five settling classes using a settling tube apparatus. The spatial distribution of soil settling classes shows a coarsening effect immediately below the eroding slope, followed by a fining trend at the slope tail. These findings support the validity of the conceptual model proposed by Starr et al. (Land Degrad Dev 11:83–91, ) to predict SOC redistribution patterns along hillslopes. The δC values of soil fractions were more positive at the footslope than on the slope shoulder or at the slope tail, suggesting enhanced decomposition rate of fresh SOC input at the footslope during or after erosion-induced transport. Pronounced CO emission rates at the slope tail also suggest a higher potential for decomposition of the eroded SOC after deposition. Overall, our results illustrate that immediate deposition of fast settling soil fractions and the associated SOC at footslopes, and potential CO emissions during or immediately after transport, must be appropriately accounted for in attempts to quantify the role of soil erosion in terrestrial C sequestration. A SOC erodibility parameter based on actual settling velocity distribution of eroded fractions is needed to better calibrate soil erosion models.
Yaxian Hu; Asmeret Asefaw Berhe; Marilyn L. Fogel; Goswin J. Heckrath; Nikolaus J. Kuhn. Transport-distance specific SOC distribution: Does it skew erosion induced C fluxes? Biogeochemistry 2016, 128, 339 -351.
AMA StyleYaxian Hu, Asmeret Asefaw Berhe, Marilyn L. Fogel, Goswin J. Heckrath, Nikolaus J. Kuhn. Transport-distance specific SOC distribution: Does it skew erosion induced C fluxes? Biogeochemistry. 2016; 128 (3):339-351.
Chicago/Turabian StyleYaxian Hu; Asmeret Asefaw Berhe; Marilyn L. Fogel; Goswin J. Heckrath; Nikolaus J. Kuhn. 2016. "Transport-distance specific SOC distribution: Does it skew erosion induced C fluxes?" Biogeochemistry 128, no. 3: 339-351.
The validity of soil erosion data is often questioned because of the variation between replicates. This paper aims to evaluate the relevance of interreplicate variability to soil and soil organic carbon (SOC) erosion over prolonged rainfall. Two silty loams were subjected to simulated rainfall of 30 mm h−1 for 360 min. The entire rainfall event was repeated ten times to enable statistical analysis of the variability of the runoff and soil erosion rates. The results show that, as selective removal of depositional particles and crust formation progressively stabilized the soil surface, the interreplicate variability of runoff and soil erosion rates declined considerably over rainfall time. Yet, even after the maximum runoff and erosion rates were reached, the interreplicate variability still remained between 15 and 39 %, indicating the existence of significant inherent variability in soil erosion experiments. Great caution must be paid when applying soil and SOC erosion data after averaging from a small number of replicates. While not readily applicable to other soil types or rainfall conditions, the great interreplicate variability observed in this study suggests that a large number of replicates is highly recommended to ensure the validity of average values, especially when extrapolating them to assess soil and SOC erosion risk in the field.
Yaxian Hu; Wolfgang Fister; Nikolaus J. Kuhn. Inherent interreplicate variability during small-scale rainfall simulations. Journal of Soils and Sediments 2016, 16, 1809 -1814.
AMA StyleYaxian Hu, Wolfgang Fister, Nikolaus J. Kuhn. Inherent interreplicate variability during small-scale rainfall simulations. Journal of Soils and Sediments. 2016; 16 (6):1809-1814.
Chicago/Turabian StyleYaxian Hu; Wolfgang Fister; Nikolaus J. Kuhn. 2016. "Inherent interreplicate variability during small-scale rainfall simulations." Journal of Soils and Sediments 16, no. 6: 1809-1814.
During slope-scale erosion events, re-distribution of eroded soil and the associated soil organic carbon (SOC) is not always uniform, but very often affected by preferential transport and deposition. Under given flow conditions, the site of SOC deposition depends on the transport distances of sediment particles containing the SOC. Very often, soil and SOC erosion risk are assessed by applying mineral particle specific SOC distributions to erosion models. However, soil is not always eroded as individual mineral particles, but mostly in a form of aggregates. Aggregates are likely to increase settling velocities of individual mineral particles, which may considerably reduce the transport distance of sediment fractions and the associated SOC, skewing SOC redistribution and its subsequent fate. Yet, little is known about the potential effects of aggregation on the movement and fate of eroded SOC.\ud \ud To assess the effect of preferential deposition, a simulated rainfall was applied to two soils in this study, with the Movelier silty clay having greater SOC content and aggregate stability than the Möhlin silty loam. The eroded sediments of the two soils were fractionated by a settling tube apparatus according to their potential transport distances. The CO2 emissions of the fractionated and incubated sediments were then measured for 50 days enabling the assessment of the bioactivity of eroded SOC for weeks after deposition. Our results show that: 1) the re-deposition of eroded SOC into terrestrial systems increased by 64% if considering the actual aggregate specific rather than the mineral particle specific SOC distribution. 2) The CO2 emission rates differed across settling fractions, with the most pronounced rates in the finest fractions from the Möhlin silty loam sediment and in the medium-size fractions from the Movelier silty clay sediment. 3) Over 50-day incubation, the CO2 emissions from the Möhlin silty loam sediment was 114% greater than that from the non-eroded Möhlin soil, whereas CO2 emissions were roughly equivalent for the Movelier sediment and non-eroded Movelier silty clay. These data demonstrate that erosion and preferential deposition of SOC-enriched aggregates can enhance terrestrial SOC deposition. This can further result in greater CO2 efflux than commonly applied mineral particle size specific SOC distribution would suggest. The different performances of deposition and CO2 emissions between the two soils also suggest that these effects can vary with soil type. Our observations certainly illustrate that sediment aggregation requires further investigation to assess the redistribution and subsequent fate of eroded SOC appropriately
Yaxian Hu; Nikolaus Kuhn. Erosion-induced exposure of SOC to mineralization in aggregated sediment. CATENA 2016, 137, 517 -525.
AMA StyleYaxian Hu, Nikolaus Kuhn. Erosion-induced exposure of SOC to mineralization in aggregated sediment. CATENA. 2016; 137 ():517-525.
Chicago/Turabian StyleYaxian Hu; Nikolaus Kuhn. 2016. "Erosion-induced exposure of SOC to mineralization in aggregated sediment." CATENA 137, no. : 517-525.