Process-based modelling of erosion,sediment transport and reservoir siltation in mesoscale semi-arid catchments     

Axel Bronstert  José-Carlos de Araújo  Ramon J. Batalla  Alexandre Cunha Costa  José Miguel Delgado  Till Francke  Saskia Foerster  Andreas Guentner  José Andrés López-Tarazón  George Leite Mamede  Pedro Henrique Medeiros  Eva Mueller  Damià Vericat 《Journal of Soils and Sediments》2014,14(12):2001-2018

Purpose

To support scientifically sound water management in dryland environments a modelling system has been developed for the quantitative assessment of water and sediment fluxes in catchments, transport in the river system, and retention in reservoirs. The spatial scale of interest is the mesoscale because this is the scale most relevant for management of water and land resources.

Materials and methods

This modelling system comprises process-oriented hydrological components tailored for dryland characteristics coupled with components comprising hillslope erosion, sediment transport and reservoir deposition processes. The spatial discretization is hierarchically designed according to a multi-scale concept to account for particular relevant process scales. The non-linear and partly intermittent run-off generation and sediment dynamics are dealt with by accounting for connectivity phenomena at the intersections of landscape compartments. The modelling system has been developed by means of data from nested research catchments in NE-Spain and in NE-Brazil.

Results and discussion

In the semi-arid NE of Brazil sediment retention along the topography is the main process for sediment retention at all scales, i.e. the sediment delivery is transport limited. This kind of deposition retains roughly 50 to 60 % of eroded sediment, maintaining a similar deposition proportion in all spatial scales investigated. On the other hand, the sediment retained in reservoirs is clearly related to the scale, increasing with catchment area. With increasing area, there are more reservoirs, increasing the possibility of deposition. Furthermore, the area increase also promotes an increase in flow volume, favouring the construction of larger reservoirs, which generally overflow less frequently and retain higher sediment fractions. The second example comprises a highly dynamic Mediterranean catchment in NE-Spain with nested sub-catchments and reveals the full dynamics of hydrological, erosion and deposition features. The run-off modelling performed well with only some overestimation during low-flow periods due to the neglect of water losses along the river. The simulated peaks in sediment flux are reproduced well, while low-flow sediment transport is less well captured, due to the disregard of sediment remobilization in the riverbed during low flow.

Conclusions

This combined observation and modelling study deepened the understanding of hydro-sedimentological systems characterized by flashy run-off generation and by erosion and sediment transport pulses through the different landscape compartments. The connectivity between the different landscape compartments plays a very relevant role, regarding both the total mass of water and sediment transport and the transport time through the catchment.  相似文献   

Fecal Indicator and Pathogen Reduction in Vegetation Microcosms     

Johan Åström  Anneli Carlander  Kenneth Sahlén  Thor Axel Stenström 《Water, air, and soil pollution》2006,176(1-4):375-387

Municipal wastewater has been applied as a fertilizer to coniferous forest in northern Sweden with the additional aims to purify the wastewater and reduce the treatment costs. This practice has the potential to introduce pathogenic microorganisms from the applied wastewater or sludge to the environment, with a subsequent risk of transmission to exposed humans or animals. Seasonality and climatological conditions, in particular low temperature, humidity and low sun intensity will furthermore affect the persistence of pathogens in the forest in northern Scandinavia and may therefore enhance the survival and thereby the exposure risk. The survival of two pathogens (Salmonella senftenberg and Campylobacter coli) and four fecal indicator organisms; bacteria strains (E. coli and E. fecalis) and bacteriophages (S. typhimurium phage 28 B and ?x174), used here as viral models, was evaluated in microcosms (60 Litre terrariums) with two vegetation regimes (characterized as moss and lichen) at selected temperatures (+3^?C to +27^?C) and artificial light exposure (light and dark). Salmonella persisted in high numbers after 35 days in the vegetation, indicating a potential risk for further transmission. Neither the vegetation regime nor temperature or light exposure as independent factors governed the reduction of the indicator bacteria and the bacteriophages. The persistence of the indicator organisms was generally best supported in the moss vegetation at low temperature in the dark, where the time for a 90% reduction (T₉₀) was in the range from 8 days (E. coli) to 31 days (Salmonella phage). The die-off characteristics found in this study provide baseline values for further validations in the field and verify that the purification and reuse of municipal wastewater in coniferous forest could potentially be responsible for transmission of fecal pathogens to humans and animals.  相似文献   

Entwicklung und gestaltung gehölzreicher weidelandschaften auf reliefiertem niedermoor     

Gisbert Schalitz  Axel Behrendt 《Archives of Agronomy and Soil Science》2013,59(1):57-66

Die drastische Reduzierung der Besatzstärke an Rindern auf 0,5–1 GV/ha LF nach der politischen Wende in Ostdeutschland schafft interessante Möglichkeiten der Neugestaltung von Weiden. Um stärker und gleichmäßiger wechselnde Aufenthaltsplätze in der Fläche zu induzieren, könnten Extensivweiden in einer Art aufgelockerter Parklandschaft gestaltet werden. Die Eignung verschiedener Baum‐ und Straucharten für Niedermoore wurde in der Forschungsstation Paulinenaue, nordwestlich von Berlin, analysiert.

Untersuchungen zeigten, daß zukünftig insbesondere ausländische Rinderrassen vor zu starker UV‐Belastung geschützt werden sollten. Die heutigen ausgeräumten Weidelandschaften bieten nicht genügend Schatten und auch nicht ausreichend Windund Wetterschutz während des Winters. Die Entwicklung von vielfältig strukturierten Weiden verbessert das Wohlbefinden der Tiere als auch die Biodiversität des gesamten Ökosystems. Die Landschaft gewinnt durch die Variation von Landschaftselementen, der Stoffkreislauf wird geregelter und die Akzeptanz für den ländlichen Raum in der Bevölkerung steigt.  相似文献   

Implications of soil substrate and land use for properties of fen soils in North-East Germany Part III: Soil quality for grassland use     

Dr Lothar Mueller  Axel Behrendt  T. Graham Shepherd  Uwe Schindler  Thomas Kaiser 《Archives of Agronomy and Soil Science》2013,59(2):137-146

Abstract

The aim of the study was to analyse aspects of fen soil quality for grassland use with regard to the different topsoil structure and their status of earthification/moorshification (degradation). Fifty fens of different origin, structural status and land use intensity were sampled, analysed and scored by different methods: Visual Soil Assessment, Peerlkamp test and Muencheberg Soil Quality Rating. Suitable soil structure scores were found at different land use intensities with the exception of stock tracks on pastures. These had lower water and air permeability and lower soil strength. Highest visual scores of macrostructure were found where the water table was deeper; while highest overall soil quality scores occurred where the water table was optimum. The accelerated status of moorshification had no effect on the soil quality scores and on the crop yield. At lower levels of soil development (earthification) the crop yield was slightly lower due to higher proportions of inedible plants. It may be concluded that degraded peat soils will have no loss of soil quality and have relatively high soil quality for grassland use if the water table can be managed in a suitable range and the sward quality is maintained.  相似文献   

The derivation of grassland vegetation types on the basis of site and land use characteristics     

Thomas Kaiser Dr  Horst Käding  Joachim Kiesel  Lothar Müller  Wilfried Hierold  Axel Behrendt 《Archives of Agronomy and Soil Science》2013,59(4):405-416

This study derives grassland communities from site, climate and land use characteristics, allowing yield estimation within the framework of model scenarios. Based on the dominant species, about 450 relevés, primarily of extensively used grassland from four regions of the North-East German lowlands, were classified into vegetation types using a cluster analysis. These types were then reclassified to known phytosociological communities. The relationship between the vegetational composition and the abiotic explanatory variables were verified by a discriminant analysis. The water supply level proved to be the most important factor influencing grassland vegetation. The impact of historical land use (especially the persistence of formerly sown species) reduced prognostic quality.  相似文献   

Variation in phenotypic characters of pale flax (<Emphasis Type="Italic">Linum bienne</Emphasis> Mill.) from Turkey     

Hüseyin Uysal  Orhan Kurt  Yong-Bi Fu  Axel Diederichsen  Peter Kusters 《Genetic Resources and Crop Evolution》2012,59(1):19-30

The diversity of pale flax (Linum bienne Mill.) as the progenitor of cultivated flax (L. usitatissimum L.) has not been well documented and the domestication syndromes in cultivated flax are poorly understood. An attempt was made to characterize 34 pale flax accessions and six cultivated flax accessions collected during 2007 summer in Turkey. A total of 12 quantitative and 7 qualitative characters covering vegetative and generative plant parts, including phenological traits, were assessed. The occurrence of yellow anthers well known in cultivated flax is reported for the first time in pale flax. Pale flax displayed larger variation in vegetative plant parts and growth habit than the cultivated flax and more heterogeneity within accessions. Within pale flax, a higher degree of variation was observed in many generative parts such as the flower characters than in the capsule and seed characters. Based on the assayed characters, the pale flax from Turkey was grouped into three clusters and these clusters were associated with site elevation and longitude, further confirming local genetic differentiation in pale flax from Turkey. These findings are significant for further studies of flax domestication history and useful for further exploitation of wild flax in genetic improvement of cultivated flax.  相似文献   

Modelling the effects of land-use change on runoff and sediment yield for a meso-scale catchment in the Southern Pyrenees     

Eva Nora Mueller  Till Francke  Ramon J. Batalla  Axel Bronstert 《CATENA》2009,79(1):103-111

The Southern Pre-Pyrenees experienced a substantial land-use change over the second half of the 20th century owing to the reduction of agricultural activities towards the formation of a more natural forest landscape. The land-use change over the last 50 years with subsequent effects on water and sediment export was modelled with the process-based, spatially semi-distributed WASA-SED model for the meso-scale Canalda catchment in Catalonia, Spain. It was forwarded that the model yielded plausible results for runoff and sediment yield dynamics without the need of calibration, although the model failed to reproduce the shape of the hydrograph and the total discharge of several individual rainstorm events, hence the simulation capabilities are not yet considered sufficient for decision-making purposes for land management. As there are only a very limited amount of measured data available on sediment budgets with altered land-use and climate change settings, the WASA-SED model was used to obtain qualitative estimates on the effects of past and future change scenarios to derive a baseline for hypothesis building and future discussion on the evolution of sediment budgets in such a dryland setting. Simulating the effects of the past land-use change, the model scenarios resulted in a decrease of up to 75% of the annual sediment yield, whereas modelled runoff remained almost constant over the last 50 years. The relative importance of environmental change was evaluated by comparing the impact on sediment export of land-use change, that are driven by socio-economic factors, with climate change projections for changes in the rainfall regime. The modelling results suggest that a 20% decrease in annual rainfall results in a decrease in runoff and sediment yield, thus an ecosystem stabilisation in regard to sediment export, which can only be achieved by a substantial land-use change equivalent to a complete afforestation. At the same time, a 20% increase in rainfall causes a large export of water and sediment resources out of the catchment, equivalent to an intensive agricultural use of 100% of the catchment area. For wet years, the effects of agricultural intensification are more pronounced, so that in this case the intensive land-use change has a significantly larger impact on sediment generation than climate change. The WASA-SED model proved capable in quantifying the impacts of actual and potential environmental change, but the reliability of the simulation results is still circumscribed by considerable parameterisation and model uncertainties.  相似文献   

Variations of nutrient concentrations and contents between summer and autumn within tree compartments of European beech (Fagus sylvatica)          下载免费PDF全文

Matthias Ulbricht  Axel Göttlein  Peter Biber  Jochen Dieler  Hans Pretzsch 《植物养料与土壤学杂志》2016,179(6):746-757

The paradigm of sustainable forest management was initially aimed to ensure continuous wood supply but has gradually been extended for many functions and services of forest ecosystems, including the aspect of nutrient sustainability. The current tendency towards harvesting all year round and whole‐tree export for energy purposes raised the question of how the input : output balance of nutrients depends on site conditions, tree species, and harvest intensity. Possible differences in nutrient export between harvesting in autumn and summer have been more or less neglected. Based on compartment‐wise analyses of biomass and nutrient (Ca, K, Mg, and P) concentrations of adult European beeches (Fagus sylvatica [L.]), nine compartments were sampled in summer and nine in autumn. We found, for the majority of the compartments (especially in branch wood), increased levels of nutrient concentrations: 81% (Ca), 54% (K), 90% (Mg), and 96% (P) in autumn compared to summer. Upscaling our results to stand level revealed up to 10.0% and 1.6% less mineral nutrient exports of Ca and Mg, respectively, for whole‐tree harvest in forest stands when carried out in summer instead of autumn. Nutrient removal was increased by 0.8% and by 13.0% for K and P, respectively, in summer. Despite lower nutrient export, many ecological, logistic, and technical reasons discourage harvesting in summer. Our findings, however, deliver an additional yet so far missing mosaic piece for a better understanding and assessment of the frame conditions for sustainable nutrient management in beech forests.  相似文献   

Progesterone and pregnanediol-glucuronid concentrations in saliva, milk and urine of female alpacas and their application in pregnancy diagnosis     

Volkery J  Wittek T  Sobiraj A  Gottschalk J  Einspanier A 《Berliner und Münchener tier?rztliche Wochenschrift》2010,123(11-12):500-505

The objective of the present study was the measurement of the pregnancy associated hormones progesterone (P4) and pregnanediol-glucuronide (PdG) in saliva, milk and urine of alpacas and their potential use in pregnancy diagnosis. Sample of blood, saliva, milk and urine were obtained from 36 female alpacas before mating and throughout the pregnancy. Concentrations of P4 and PdG were determined using an enzyme immunoassay (EIA). Pregnancy was checked by ultrasonography at any sampling time. The milk samples were also tested using a commercial on-farm progesterone kit which was designed for dairy cattle. EIA-Concentrations of P4 in blood, milk and urine and urine PdG concentrations were significantly higher in pregnant than in not pregnant alpacas. There was no difference in concentrations of P4 or PdG in saliva. The accuracy of the progesterone kit was 90% for diagnosis of pregnancy and 69% for non-pregnancy. However, 70% of the false positive results also showed relatively high P4 milk concentrations in the EIA. Values of P4 in blood and PdG in urine are comparable to previous reports in alpacas and therefore can be confirmed as an indicator for pregnancy. Saliva seems unsuitable in pregnancy diagnosis in alpacas, whereas milk seems to be an adequate alternative. The use of milk and urine would simplify the pregnancy diagnosis in alpacas since in contrast to the current methods (e. g. blood progesterone) the owners can take the samples. The avoidance of blood sampling results in a considerable stress reduction for the animals. P4 measurement in milk and PdG measurement in urine are good alternatives in pregnancy diagnosis during the first month of pregnancy, when a trans-abdominal ultrasonographic examination is not yet reliable. However, since high values of P4 and PdG only show the presence of active luteal tissue and therefore are indirect markers of pregnancy the diagnosis should be confirmed using ultrasound later in pregnancy.  相似文献   

Arthropod species richness in the Norway Spruce (Picea abies (L.) Karst.) canopy along an elevation gradient     

Juliane Röder  Claus Bässler  Roland Brandl  Libor Dvořak  Andreas Floren  Martin M. Goßner  Axel Gruppe  Andrea Jarzabek-Müller  Oldřich Vojtech  Christian Wagner  Jörg Müller 《Forest Ecology and Management》2010

Norway Spruce is the economically most important tree species in Europe and has been cultivated in plantations on a large-scale at low elevations, far outside its natural range. In the Bohemian Forest, it naturally occurs in pure stands above 1150 m a.s.l. and as a mixed tree species from 650 to 1150 m a.s.l. An understanding of natural distributions and the diversity along temperature gradients at various elevations is important for conservation, pest management, and predictions of future species assemblages by global warming. Here we investigated the species richness of canopy arthropods in spruce trees along a gradient from 300 to 1300 m a.s.l. using flight-interception traps. We analyzed species richness by combining diversity partitioning with a moving window approach after standardizing sample size per plot. Total richness decreased linearly as the elevation increased, which reflected declining temperatures and a declining regional species pool. Phytophages (herbivores excluding xylophages) were the most influenced. Richness did not peak at the transition zones of the three ecological elevation zones, neither for all species, nor for any of the separate functional groups. However, the proportion of both beetle and true bug spruce specialists significantly increased with elevation and actually doubled in richness above 1000 m a.s.l., where spruce is naturally dominating. Our results indicate that even planted spruce trees at lower elevations maintain high levels of species richness. Further climate warming will promote overall species richness, especially of phytophages, at all elevations. However, spruce specialists may be seriously threatened by global warming.  相似文献