Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Springer (CrossRef)  (26)
Type of Medium
Language
Year
  • 1
    Language: English
    In: Plant and Soil, 2014, Vol.384(1), pp.93-112
    Description: Aims A simulation model to demonstrate that soil water potential can regulate transpiration, by influencing leaf water potential and/or inducing root production of chemical signals that are transported to the leaves. Methods Signalling impacts on the relationship between soil water potential and transpiration were simulated by coupling a 3D model for water flow in soil, into and through roots (Javaux et al. 2008) with a model for xylem transport of chemicals (produced as a function of local root water potential). Stomatal conductance was regulated by simulated leaf water potential (H) and/or foliar chemical signal concentrations (C; H+C). Split-root experiments were simulated by varying transpiration demands and irrigation placement. Results While regulation of stomatal conductance by chemical transport was unstable and oscillatory, simulated transpiration over time and root water uptake from the two soil compartments were similar for both H and H+C regulation. Increased stomatal sensitivity more strongly decreased transpiration, and decreased threshold root water potential (below which a chemical signal is produced) delayed transpiration reduction. Conclusions Although simulations with H+C regulation qualitatively reproduced transpiration of plants exposed to partial rootzone drying (PRD), long-term effects seemed negligible. Moreover, most transpiration responses to PRD could be explained by hydraulic signalling alone. Keywords Soil-root modeling * R-SWMS * Hormonal Signaling * Stomatal conductance * Partial rootzone drying
    Keywords: Soil-root modelling ; R-SWMS ; Hormonal signalling ; Stomatal conductance ; Partial rootzone drying
    ISSN: 0032-079X
    E-ISSN: 1573-5036
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Plant and soil, 2015, Vol.394(1), pp.109-126
    Description: AIMS: Stomata can close to avoid cavitation under decreased soil water availability. This closure can be triggered by hydraulic (‘H’) and/or chemical signals (‘C’, ‘H + C’). By combining plant hydraulic relations with a model for stomatal conductance, including chemical signalling, our aim was to derive direct relations that link soil water availability, expressed as fraction of roots in dry soil (fdᵣy), to transpiration reduction. METHODS: We used the mechanistic soil-root water flow model R-SWMS to verify this relation. Virtual split root experiments were simulated, comparing horizontal and vertical splits with varying fdᵣy and different strengths of stomatal regulation by chemical and hydraulic signals. RESULTS: Transpiration reduction predicted by the direct relations was in good agreement with numerical simulations. For small enough potential transpiration and large enough root hydraulic conductivity and stomatal sensitivity to chemical signalling isohydric plant behaviour originates from H + C control whereas anisohydric behaviour emerges from C control. For C control the relation between transpiration reduction and fdᵣy becomes independent of transpiration rate whereas H + C control results in stronger reduction for higher transpiration rates. CONCLUSION: Direct relations that link effective soil water potential and leaf water potential can describe different stomatal control resulting in contrasting behaviour. ; p. 109-126.
    Keywords: Plant Available Water ; Root Hydraulic Conductivity ; Stomata ; Leaf Water Potential ; Stomatal Conductance ; Roots ; Water Flow ; Mathematical Models ; Stomatal Movement ; Leaves ; Soil Water Potential
    ISSN: 0032-079X
    E-ISSN: 15735036
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Plant and Soil, 2017, Vol.415(1), pp.99-116
    Description: Background and aims The use of standard dynamic root architecture models to simulate root growth in soil containing macropores failed to reproduce experimentally observed root growth patterns. We thus developed a new, more mechanistic model approach for the simulation of root growth in structured soil. Methods In our alternative modelling approach, we distinguish between, firstly, the driving force for root growth, which is determined by the orientation of the previous root segment and the influence of gravitropism and, secondly, soil mechanical resistance to root growth. The latter is expressed by its inverse, soil mechanical conductance, and treated similarly to hydraulic conductivity in Darcy's law. At the presence of macropores, soil mechanical conductance is anisotropic, which leads to a difference between the direction of the driving force and the direction of the root tip movement. Results The model was tested using data from the literature, at pot scale, at macropore scale, and in a series of simulations where sensitivity to gravity and macropore orientation was evaluated. Conclusions Qualitative and quantitative comparisons between simulated and experimentally observed root systems showed good agreement, suggesting that the drawn analogy between soil water flow and root growth is a useful one.
    Keywords: Macropores ; Root architecture model ; Root growth direction ; R-SWMS
    ISSN: 0032-079X
    E-ISSN: 1573-5036
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Water Resources Management, 2013, Vol.27(3), pp.885-909
    Description: The main goal of the project was to assess nitrogen pollution of surface waters and groundwater in the Federal State of North Rhine Westphalia (NRW), Germany. For this purpose the hydro(geo-)logical models GROWA-DENUZ/WEKU were coupled to the agro-economic model RAUMIS in order to assess the diffuse nitrogen loads and to approaches to determine the nitrogen loads from point sources. In this way the complex socio-economic interrelations and hydrological/hydrogeological interdependencies were simultaneously. The model network was applied consistently across the whole territory of NRW. At first the actual N inputs into groundwater and surface waters resulting from diffuse sources and point sources were assessed. For the relevant diffuse input pathways (groundwater runoff, drainage runoff and natural interflow) this was done in a spatial resolution of 100 m ∙ 100 m. In the case of point source inputs information from municipal waste water treatment plants, industrial effluents, rainwater sewers and combined sewer overflows has been considered. For NRW an actual total N input into surface waters of ca. 117.000 t ∙ a −1  N has been quantified. As the inputs via natural interflow (ca. 30 %), groundwater runoff (ca. 26 %) and drainage systems (ca. 18 %) hold the largest portion, it is evident that measures to control nitrate pollution have to focus on the inputs from diffuse sources. For this purpose, initially the development of the agrarian sector according to the Common Agricultural Policy, CAP until 2015 including supplementary measures and other impact factors has been analysed. The impact of this so-called baseline scenario 2015 was predicted for both, the diffuse N surpluses and the N pollution of groundwater and surface waters. It could be shown that the baseline projections for the agricultural sector through 2015 may lead to decrease of the diffuse N inputs into groundwater by ca. 13.500 t ∙ a −1  N and an overall decrease of the diffuse N inputs into surface waters by ca. 25.000 kg ∙ ha −1  ∙ a −1  N. Based on the baseline scenario 2015 the additional N reduction to guarantee nitrate concentrations in groundwater below the EU-threshold value of 50 mg ∙ l −1 NO 3 was determined by means of a backward model calculation. This was done using the predicted nitrate concentrations in the leachate 2015 for the individual 100 m ∙ 100 m grids as starting points. In this way for the whole territory of NRW an additional N reduction beyond the baseline scenario 2015 of ca. 12.000 t ∙ a −1  N has been assessed. Model results indicate that additional N reduction measures don’t have to be implemented area-covering in order to be efficient, but in certain subareas only. It is suggested that in these subareas the available financial resources for the implementation of N reduction measures shall be used for individual, i.e. regionally adapted nitrate reduction measures.
    Keywords: Water framework directive ; Nitrate pollution ; Groundwater ; Surface waters ; Nitrate modelling ; Agro-environmental management
    ISSN: 0920-4741
    E-ISSN: 1573-1650
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: Plant and Soil, 2019, Vol.439(1), pp.273-292
    Description: Background and aims Although modelling of water and nutrient uptake by root systems has advanced considerably in recent years, steep local gradients of nutrient concentration near the root-soil interface in the rhizosphere are still a central challenge for accurate simulation of water and nutrient uptake...
    Keywords: Water uptake ; Nutrient uptake ; Root system architecture ; Root soil modelling ; Multiscale ; Root system scale ; Single root scale ; Rhizosphere
    ISSN: 0032-079X
    E-ISSN: 1573-5036
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Boundary-Layer Meteorology, 2014, Vol.151(2), p.373(15)
    Description: We applied three approaches to estimate the zero-plane displacement d through the aerodynamic measurement height z (with z = [z.sub.m] - d and [z.sub.m] being the measurement height above the surface), and the aerodynamic roughness length [z.sub.0], from single-level eddy covariance data. Two approaches (one iterative and one regression-based) were based on the universal function in the logarithmic wind profile and yielded an inherently simultaneous estimation of both d and [z.sub.0]. The third approach was based on flux-variance similarity, where estimation of d and consecutive estimation of [z.sub.0]] are independent steps. Each approach was further divided into two methods differing either with respect to the solution technique (profile approaches) or with respect to the variable (variance of vertical wind and temperature, respectively). All methods were applied to measurements above a large, growing wheat field where a uniform canopy height and its frequent monitoring provided plausibility limits for the resulting estimates of time-variant d and [z.sub.0]. After applying, for each approach, a specific data filtering that accounted for the range of conditions (e.g. stability) for which it is valid, five of the six methods were able to describe the temporal changes of roughness parameters associated with crop growth and harvest, and four of them agreed on d to within 0.3 m most of the time. Application of the same methods to measurements with a more heterogeneous footprint consisting of fully-grown sugarbeet and a varying contribution of adjacent harvested fields exhibited a plausible dependence of the roughness parameters on the sugarbeet fraction. It also revealed that the methods producing the largest outliers can differ between site conditions and stability. We therefore conclude that when determining d for canopies with unknown properties from single-level measurements, as is increasingly done, it is important to compare the results of a number of methods rather than rely on a single one. An ensemble average or median of the results, possibly after elimination of methods that produce outliers, can help to yield more robust estimates. The estimates of [z.sub.0] were almost exclusively physically plausible, although d was considered unknown and estimated simultaneously with the methods and results described above. Keywords Aerodynamic roughness length * Barley * Eddy covariance * Sonic anemometer * Sugarbeet * Wheat * Zero-plane displacement
    Keywords: Earth Sciences ; Atmospheric Sciences ; Meteorology ; Atmospheric Protection/Air Quality Control/Air Pollution ; Aerodynamic Roughness Length ; Barley ; Eddy Covariance ; Sonic Anemometer ; Sugarbeet ; Wheat ; Zero-Plane Displacement ; Meteorology & Climatology ; Biology;
    ISSN: 0006-8314
    E-ISSN: 15731472
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Language: English
    In: Applied Magnetic Resonance, 2016, Vol.47(2), pp.121-138
    Description: Soils are highly complex and heterogeneous porous materials, and thus measuring water distribution non-invasively with high accuracy and adequate spatial resolution still remains challenging. The first few centimeters of a soil surface control the vapor flux to the atmosphere justifying the need for high spatial resolution measurements of moisture content. The objective of this study was to compare and assess the feasibility of various high-resolution magnetic resonance (MR) methods to characterize an unsaturated porous system. We employed (1) a spin-echo, (2) three types of single-point imaging and (3) a unilateral three-magnet array to monitor T 1 and T 2,app relaxation time spectra and the effective moisture saturation (Θ MR ) of a silt loam under progressing desaturation with focus on an emerging unsaturated surface layer, which is predicted by theory. During the first stage of drying where evaporation occurred at the soil surface, all methods showed homogeneously distributed moisture. A decreasing Θ MR and a shift in the T 1 and T 2,app relaxation time spectra to shorter values indicated the commencement of stage 2 evaporation coincided with an increasing unsaturated layer. At low water contents, the most suitable method to determine the extent of a desaturated surface zone with high accuracy was found to be single--point ramped imaging with T 1 enhancement. As a simple and low-cost device the unilateral three-magnet array was feasible to monitor the drying process until the dry surface layer developed.
    Keywords: Physics ; Solid State Physics ; Spectroscopy/Spectrometry ; Atoms and Molecules in Strong Fields, Laser Matter Interaction ; Physical Chemistry ; Organic Chemistry ; Physics;
    ISSN: 0937-9347
    E-ISSN: 1613-7507
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Environmental Earth Sciences, 2016, Vol.75(14), pp.1-15
    Description: Irrigated agriculture is an important economic factor in the rural parts of the metropolitan area of Hamburg. It is commonly expected that climate change will reduce the groundwater quantities available for field irrigation. Against this background, the ratio of irrigation need and groundwater recharge (IGR-ratio) is suggested as an indicator to assess climate change impacts on the vulnerability of groundwater resources towards overexploitation by agricultural irrigation. The IGR-ratio has been assessed based on the distributed water balance model mGROWA, i.e. under consideration of the simulated groundwater recharge levels and the field crop-specific irrigation need of the commonly cultivated field crops. The spatial IGR-ratio distribution determined for the observed reference period 1971–2000 has shown that the delineated vulnerable areas coincide with the regions for which high irrigation quantities have been documented at present. Additionally, the IGR-ratio depicts the areas in which irrigation is currently still negligible, but in which the introduction of irrigation into agricultural practice would lead to an immediate overexploitation of the sustainably available groundwater budget. The possible impact of future climate on IGR-ratios was determined by using a model chain of mGROWA and the regional climate models REMO and WETTREG2010. The related ensemble simulations did not provide a uniform tendency of possible future IGR-ratio changes. Whereas the mGROWA–WETTREG2010 realisations projected a very high increase in the IGR-ratios, the mGROWA–REMO realisations did not show a pronounced trend of increasing IGR-ratios. Therefore, considerable uncertainties remain regarding the future bandwidth of IGR-ratio changes.
    Keywords: Groundwater recharge ; Irrigation need ; mGROWA ; Climate change ; Vulnerability indicator
    ISSN: 1866-6280
    E-ISSN: 1866-6299
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Biology and Fertility of Soils, 2016, Vol.52(2), pp.151-164
    Description: The addition of biochar or digestate as organic amendments to soils is currently controversially discussed with regard to its positive and negative effects on C mineralization. Organic amendments are generally applied to agricultural fields to improve soil quality and crop yield. In this study, we present results from short-term respiration experiments (90 days), where two different biochars (produced at 400 and 800 °C) as well as digestate from biogas production were added in different combinations to two soils (loamy sand and silt loam). Additionally, both amendments were mixed together into the soil to study interactions between biochar and digestate effects and investigate the interactions of both amendments with clay minerals resulting in a total of 13 mixtures (plus control soils) per soil type. The results indicate that the rate of CO 2 evolution was not proportional to the amount of C added to the systems indicating a saturation effect in the C degradation mechanism. More than 40 % of the digestate C was released as CO 2 and only 3 % for the biochar soil mixture; the recalcitrant nature of biochar and its suitability for short-term C stabilization in soils (incubation period of 90 days) were shown. Surprisingly, a much lower CO 2 release (up to 11-fold) was observed in soil/digestate/biochar compared to soil/digestate mixtures without biochar. This effect was observed even when only 1 % ( w / w ) biochar was added to the digestate/soil mixtures, indicating that the biochar changed the physicochemical properties of the system. Additional dissolved organic C (DOC) sorption experiments revealed that large quantities of DOC can be sorbed by the biochar reducing the microbial accessible DOC in the liquid phase and as a consequence also the CO 2 production.
    Keywords: Biochar ; Digestate ; C degradation ; DOC sorption ; Microbial respiration
    ISSN: 0178-2762
    E-ISSN: 1432-0789
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Plant and Soil, 2014, Vol.377(1), pp.277-293
    Description: AIMS: Soil salinity can cause salt plant stress by reducing plant transpiration and yield due to very low osmotic potentials in the soil. For predicting this reduction, we present a simulation study to (i) identify a suitable functional form of the transpiration reduction function and (ii) to explain the different shapes of empirically observed reduction functions. METHODS: We used high resolution simulations with a model that couples 3D water flow and salt transport in the soil towards individual roots with flow in the root system. RESULTS: The simulations demonstrated that the local total water potential at the soil-root interface, i.e. the sum of the matric and osmotic potentials, is for a given root system, uniquely and piecewise linearly related to the transpiration rate. Using bulk total water potentials, i.e. spatially and temporally averaged potentials in the soil around roots, sigmoid relations were obtained. Unlike for the local potentials, the sigmoid relations were non-unique functions of the total bulk potential but depended on the contribution of the bulk osmotic potential. CONCLUSIONS: To a large extent, Transpiration reduction is controlled by water potentials at the soil-root interface. Since spatial gradients in water potentials around roots are different for osmotic and matric potentials, depending on the root density and on soil hydraulic properties, transpiration reduction functions in terms of bulk water potentials cannot be transferred to other conditions, i.e. soil type, salt content, root density, beyond the conditions for which they were derived. Such a transfer could be achieved by downscaling to the soil-root interface using simulations with a high resolution process model. ; p. 277-293.
    Keywords: Soil-root modelling ; Salinity ; Root water uptake ; Stress function
    ISSN: 0032-079X
    E-ISSN: 1573-5036
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages