Impacts of N/P inputs on organic P dynamics and P status in soils and plants along a nutrient gradient

大气氮沉降影响森林氮循环，并对磷循环产生反馈作用。因此，SPP 1685优先计划第二阶段的主要目标是研究环境变化下土壤有机质周转对磷循环的重要性。这将在Lüss和Bad Brückenau的一个共同的实地实验中进行测试，研究N，P和N+P添加对N和P动态和森林营养的影响。Lüss是一个磷有限的生态系统，预计将产生重大影响，最终将从回收战略转变为收购战略。（苏黎世联邦理工学院植物营养组;蒂宾根大学地球生态组;环境传感和监测小组，FZ Jülich）是为了确定在森林生态系统中哪些和在多大程度上土壤生物过程受到矿物N和P添加的影响，以及如何进一步在SPP 1685第二阶段的三年中转化为植物营养。我们计划扩大现场的设置，因为独特的机会来研究肥料-P的命运，放射性同位素（P-32，P-33）在室外条件下在森林中的FZ Jülich（中间在土壤P馏分相比，Lüss和Bad Brückenau）。我们的假设是，矿物肥料添加后，无机和有机磷形式在土壤中的分布将发生变化，在Lüss比在Jülich和Bad Brückenau更多。土壤的矿物学和初始磷状态也将是变化的决定性因素。因此，植物磷（和氮）营养的来源将在Lüss，Jülich和Bad Brückenau之间有所不同。土壤中的过程和土壤中的通量以及植物与土壤之间的通量也将在短期内（项目的3年）受到影响，这很可能是因为有机物周转增加。我们将使用微生物工具和P-31 NMR分析以及稳定和放射性同位素技术。使用这些互补的工具，我们将能够量化土壤和植物磷池，表征有机磷的形式，评估土壤微生物群落结构窝藏磷酸酶基因，量化磷在土壤和植物池之间的通量，并确定不同来源的贡献，植物营养的示范性森林生态系统受到N和P添加。

Atmospheric nitrogen (N) deposition has been shown to affect N cycling in forests with feedbacks on the phosphorus (P) cycle. Therefore, the main objective of the 2nd phase of the SPP 1685 priority program is to investigate the importance of soil organic matter turnover on P cycling under environmental change. This will be tested in a common field experiment installed in Lüss and Bad Brückenau studying the effect of N, P and N+P additions on N and P dynamics and forest nutrition. Major effects are expected in Lüss, the P-limited ecosystem, which would eventually shift from a recycling to an acquiring strategy.The objectives of our joint proposal (Group of Plant Nutrition, ETH Zurich; Group of Geoecology, University of Tübingen; Group of Environmental Sensing and Monitoring, FZ Jülich) are to determine which and to which extent soil biological processes in the forest ecosystem are affected by mineral N and P additions and how this further translates into plant nutrition over the three years of the second phase of the SPP 1685. We plan to extend the set of field sites because of the unique opportunity to study the fate of fertilizer-P by radioactive isotopes (P-32, P-33) under outdoor conditions in a forest at the FZ Jülich (intermediate in terms of soil P fractions as compared to Lüss and Bad Brückenau). Our hypotheses are that after mineral fertiliser additions, the distribution of inorganic and organic P forms in soils will change, more in Lüss than in Jülich and Bad Brückenau. The mineralogy and initial P status of the soils will also be determinant factors for the changes. As a result, the source for plant P (and N) nutrition will differ between Lüss, Jülich, and Bad Brückenau. Processes in soil and fluxes in soil and between plants and soil will also be affected in the short term (3 years of the project), most likely because of an increased organic matter turnover. We will use microbiological tools and P-31 NMR analysis together with stable and radioactive isotope techniques. Using these complementary tools we will be able to quantify soil and plant P pools, characterize organic P forms, assess soil microbial community structure harbouring phosphatase genes, quantify fluxes of P between pools in soils and plants, and identify the contribution of different sources for plant nutrition of exemplary forest ecosystems subject to N and P additions.