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

SPP 1685的一个主要假设是，土壤中磷(P)的耗竭驱动森林生态系统从磷获取系统（从矿物阶段有效动员）到磷回收系统（高效循环）。在这里，磷通量的表征对于指示生态系统的营养状态变得重要。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认识相当有限。对于磷输出通量，以往的研究仅对森林生态系统中强降雨事件造成的损失的动态特征进行了零星的研究。我们之前的研究表明，风暴事件是磷损失的主要驱动因素，优先流路径（PFP）是磷的主要运输路径。因此，我们将重点研究森林土壤优先流（PF）的特征。在拟议项目的框架内，我们将采用原位采样方法来对比SPP地点，并定量（通量）和定性（溶液化学）研究PF。此外，我们将在联合氮磷肥施用试验（由spp1685服务项目协调）的试验田采用我们的抽样方法，研究变化营养条件下磷的输出通量。所有来自样地尺度的数据将被纳入一种新的建模方法CMF-P中，该方法通过矩阵流和PF在所有SPP站点模拟P通量，包括N × P应用实验的样地。这里还将涉及我们正在进行的spp1685 /1项目的结果，特别是关于土壤中PFP的分布，不同SPP核心地点PFP和基质中的P组分，以及水流中P的输出通量。最后，我们将利用CMF-P模型对德国云杉和山毛榉林分的P通量进行模拟，从而对所获得的过程理解进行升级。

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.