Quantification, modeling, and regionalization of seepage losses of phosphorus from forest soils

SPP 1685的一个主要假设是，土壤中的磷（P）耗竭驱动森林生态系统从磷获取系统（从矿物相有效动员）到磷循环系统（高效循环）。在这里，磷通量的表征变得重要，以指示生态系统的营养状态。然而，由于缺乏详细的研究数据，对温带森林中磷通量的定量了解受到很大限制。对于磷输出通量，以往的研究只是零星地在森林生态系统中研究了暴雨事件引起的损失的动态特征。我们以前的研究表明，风暴事件是磷损失的主要驱动力，优先流途径（PFP）是磷的主要运输途径。因此，我们将专注于森林土壤中优先流（PF）的表征。在拟议项目的框架内，我们将采用原位取样方法对比SPP网站和调查PF定量（通量）以及定性（溶液化学）。此外，我们将应用我们的采样方法在试验田的联合N × P应用实验（由SPP 1685服务项目协调），以检查P输出通量在改变营养条件下。所有的数据将被包括在一个新的建模方法CMF-P模拟P通量基质流和PF在所有SPP网站，包括N × P应用实验的地块。在这里，我们正在进行的项目SPP 1685/1的结果也将涉及，特别是关于PFP在土壤中的分布，在PFP和基质中的P组分在不同的SPP核心网站，和P输出通量在溪流。最后，我们将升级所获得的过程中的理解，使用CMF-P模型来模拟P通量的云杉和山毛榉林在德国。

A main hypothesis of the SPP 1685 is that phosphorus (P) depletion in soils drives forest ecosystems from P acquiring system (efficient mobilization from the mineral phase) to P recycling systems (highly efficient cycling). Here, the characterization of P fluxes becomes important to indicate the nutrient state of an ecosystem. However, the quantitative understanding of P fluxes in temperate forests is considerably limited by a lack of detailed research data. For P export fluxes, the dynamic character of losses induced by heavy rainfall events has been investigated only sporadically in forest ecosystems by previous research. Our previous studies revealed that storm events are a main driver for P losses, and preferential flow pathways (PFP) are the predominant transport paths for P. Therefore, we will focus on the characterization of preferential flow (PF) in forest soils. Within the frame of the proposed project, we will apply an in-situ sampling approach in contrasting SPP sites and investigate PF quantitatively (fluxes) as well as qualitatively (solution chemistry). Furthermore, we will apply our sampling approach at the test plots of the joined N x P application experiment (coordinated by the SPP 1685 service project) to examine P export fluxes under changed nutrition conditions. All data from the plot scale will be included in a new modeling approach CMF-P to simulate P fluxes by matrix flow and PF at all SPP sites, including the plots of the N x P application experiment. Here, results from our ongoing project of SPP 1685/1 will also be involved, especially regarding the distribution of PFP in soils, the P fractions in PFP and matrix at different SPP core sites, and P export fluxes in streamwater. Finally, we will upscale the acquired process understanding using the CMF-P model to simulate P fluxes for spruce and beech forest stands in Germany.