Prenzel, Jürgen

[["dc.bibliographiccitation.firstpage","48"],["dc.bibliographiccitation.journal","Ecological Modelling"],["dc.bibliographiccitation.lastpage","65"],["dc.bibliographiccitation.volume","307"],["dc.contributor.author","Nietfeld, H."],["dc.contributor.author","Prenzel, J."],["dc.date.accessioned","2018-11-07T09:54:40Z"],["dc.date.available","2018-11-07T09:54:40Z"],["dc.date.issued","2015"],["dc.description.abstract","Trees growing in acid soils often suffer from nutrient imbalances and inadequate supply of base cations (M-b) but correlations between soil chemical conditions and nutritional status of forest trees are often inconclusive. Therefore, there is a need of studies that assess the M-b acquisition potential of the absorbing fine roots from the rhizosphere soil. Previous rhizosphere models, mostly implemented as a single-ion model (SIM), calculate the actual root nutrient uptake rates. But SIM often fail to reproduce measurements which is interpreted as being caused by root-induced ionic interactions. Hence, a multi-ion model (MIM) is presented which simultaneously describes the rhizospheric dynamics of H+, Al3+, Ca2+, Mg2+, K+, Na+, NH4+, NO3-, SO42-, H2PO4- and Cl- which takes into account interactions among the ions involved. In MIM the ion diffusion transport is modeled via the Nernst-Planck equation. A root-induced constant or daily-patterned water flux is assumed. The cation sorption is defined according to the cation selectivity approach. Al-solution complexes and a kinetic expression of the dissolution or precipitation of Al(OH)(3)(s) (gibbsite) are included in MIM. The selective nutrient root uptake is balanced by the excretion of H+ (cation uptake excess) or OH- (anion uptake excess) ions. These model features guarantee electro neutrality in the rhizosphere system but lead to ionic interactions. The objectives of this study are to calculate the rhizospheric gradients of protons, Al3+ ions and base cations (M-b), their concentration changes at the root surface (RS) and in rhizospheric sub-volumes termed as soil-root interface (SRI) and inner rhizosphere (Rh). It is hypothesized that root-induced changes of pH and the pH-dependent dissolution or precipitation of Al(OH)(3)(s) affect the rhizospheric concentration gradients and the actual root uptake rates (U-Mb) of M-b cations. In various scenarios the hypothesis is tested on the basis of different ion concentrations in the bulk soil and root uptake capacities of nitrogen and M-b ions. The simulations demonstrate that the rates of root excretions as H+ or OH- ions are determined by the preferential nitrogen root uptake as NH4+ or NO3-, respectively. A high NH4+, root uptake leads to a decrease of rhizospheric pH and a dissolution of Al(OH)(3)(s). An accumulation of Al3+ cations in solution and exchanger mostly on RS and in SRI is calculated due to water flux and Al(OH)(3)(s)-dissolution. Accumulation of exchangeable Al3+ cations cause an enhanced desorption of M-b cations in SRI if compared with SIM-results and lead to a M-b concentration increase in Rh-solution and a RS-depletion for Ca2+ and K+. MIM-calculated U-Mb are slightly higher compared with SIM-calculated U-Mb. A high NO3- root uptake leads to a rhizospheric pH increase, a depletion of Al3+ in rhizospheric solution and exchanger also at water flux caused by an Al(OH)(3)(s)-formation, an accumulation of exchangeable M-b cations mainly in SRI, a M-b-depletion in rhizospheric soil solution and to significantly lower U-Mb if compared with SIM-results. Al(OH)(3)(s)-induced differences in rhizospheric M-b gradients and U-Mb-values are determined by the magnitude of the H+/OH- root excretion rates, are highest at low M-b solution concentrations, and also occur in extremely low Al3+ bulk soil solution concentrations. An Al(OH)(3)(s)-formation may be inhibited at high Al3+ bulk soil solution concentrations and high H+-concentrations in solution and exchanger of the bulk soil. The range of calculated M-b depletions and accumulations in SRI and Rh correspond to the measurement results reported in the literature. It is concluded that, in contrast to SIM, MIM-simulations present asynchronous ion concentration gradients in soil solution and exchanger which include opposite concentration gradients. At NO3- surplus a high NO3- root uptake and a low availability of M-b cations may lead to wide NO3-:M-b root uptake ratios and tree nutrient imbalances. (c) 2015 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.ecolmodel.2015.02.011"],["dc.identifier.isi","000355709500005"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36586"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1872-7026"],["dc.relation.issn","0304-3800"],["dc.title","Modeling the reactive ion dynamics in the rhizosphere of tree roots growing in acid soils. I. Rhizospheric distribution patterns and root uptake of M-b cations as affected by root-induced pH and Al dynamics"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","150"],["dc.bibliographiccitation.journal","Ecological Modelling"],["dc.bibliographiccitation.lastpage","164"],["dc.bibliographiccitation.volume","345"],["dc.contributor.author","Nietfeld, H."],["dc.contributor.author","Prenzel, J."],["dc.contributor.author","Helmisaari, H.-S."],["dc.contributor.author","Polle, A."],["dc.contributor.author","Beese, F."],["dc.date.accessioned","2018-02-22T11:08:25Z"],["dc.date.available","2018-02-22T11:08:25Z"],["dc.date.issued","2017"],["dc.description.abstract","The effects of acid soil conditions on mineral nutrition and growth of forest trees are discussed controversially. It is hypothesized that approaches are needed which determine the root nutrient uptake rates as affected by root-induced processes in the rhizosphere. A multi-ion rhizosphere model (MIM) has been developed which calculates the reactive dynamics of all major ions (H+, Al3+, Mn2+, Fe3+, Ca2+, Mg2+, K+, Na+, NO3−, SO42− and Cl−) in the rhizosphere of forest tree roots growing in acid soils. MIM calculates fine-scaled ion concentration gradients extending from the unrooted bulk soil (Bulk) to the root surface (RS) and the temporal dynamics of the average concentrations in rhizospheric sub-volumes termed as soil-root-interface (SRI), inner rhizosphere (Rh) and outer rhizosphere (oRh) of all ions (Mi) involved. SRI, Rh and oRh are defined as cylindrical soil volumes around the root which have distances to the root surface of 0.5 mm, 2.0 mm and 8–12 mm, respectively. The SRI-to-Bulk, Rh-to-Bulk and Rh-to-oRh ion concentration ratios (, , ) and the actual rates of root nutrient uptake () and H+ or OH− root excretion (EH/OH) are determined. The model is used in a Monte Carlo upscaling-procedure to calculate the - and EH/OH-rates of non-mycorrhizal long roots of spruce trees growing on a long-term monitoring plot in Solling, Germany. The objectives of this study are (i) to show the plot-specific heterogeneity of modeled - and -values of H+, base cations (Ca2+, Mg2+, K+; Mb-cations), NO3− and SO42−, to present a comparison with rhizospheric measurement data and, to model the and EH/OH rates and (ii) to present the impact of major influencing processes. The -data comprise a range of about 0.5 up to 3.0 and more depending on the ion considered. In an equivalence-testing the modeled -ratios of Ca2+, SO42−, Fe3+ and Na+ agree with corresponding ratios () of measured concentrations in Rh and oRh if extreme -values are neglected. Means of modeled -rates are 0.27, 0.126, 0.09, 1.09 and 0.12 mmol m−2 d−1 for Ca2+, Mg2+, K+, NO3− and SO42−, respectively. The -rates are determined by root uptake capacities (), height of water fluxes, Mb concentrations in bulk and rhizosphere soil, amounts of desorbed exchangeable Mb cations and EH/OH-rates. In most calculations OH− root excretions (EOH) have been calculated. Low -rates have been calculated at low water fluxes and low bulk soil solution concentrations even at high -values and are associated with EOH-rates. Based on the -rates an assessment of the contribution of long roots on the total annual nutrient uptake of the spruce stand is given. It is concluded that the measured proceeding reduction of Mb-solution concentrations and the prospective NO3− saturation in the bulk soil of the spruce plot will lead to extreme low Mb/NO3 root uptake ratios."],["dc.identifier.doi","10.1016/j.ecolmodel.2016.09.006"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/12426"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.title","Modeling of mineral nutrient uptake of spruce tree roots as affected by the ion dynamics in the rhizosphere"],["dc.title.subtitle","Upscaling of model results to field plot scale"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]