The leak in the phosphorus cycle - exploring the mechanisms and controls of phosphorus leaching in soils of acquiring and recycling forest ecosystems

磷循环中的渗漏——探索森林生态系统获取与循环土壤中磷淋失的机制与控制

• 批准号: 241226483
• 负责人: Dr. Klaus Kaiser
• 金额: --
• 依托单位: Eidgenössische Forschungsanstalt WSL - Wald-Schnee-Landschaft
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/241226483?language=en
• 关键词: leak; phosphorus; cycle; exploring; mechanisms

During ecosystem development, forest ecosystems gradually change from the acquisition of rock P to the recycling of organic P. Orthophosphate and dissolved organic P (DOP) are released in the organic layers and partly leached into the mineral soil. Our results obtained during phase 1 of the main project indicate decreasing leaching of orthophosphate from organic layers with increasing recycling tendency of the forest ecosystems. In comparison, DOP does not decrease much. Most DOP is not enzymatic hydrolysable, and consequently bioavailability is little. Orthophosphate decreases with depth in the mineral soil; the decline in DOP is less strong. Likely, DOP contributes substantially to the steady P loss from all forest ecosystems, but also orthophosphate is not retained completely in the mineral soil. Yet, the factors controlling the differential production of dissolved P in organic layers of acquiring and recycling forest ecosystems are not resolved. Also, the causes for the steady leaching of dissolved P are not fully understood.The proposed work aims at exploring the mechanisms and controls of the mobilization and leaching of P in forest ecosystems.Mobilization of P in organic layers will be assessed by measuring the release of P forms and DOP bioavailability in the SPP-fertilization experiment and in microcosms with organic matter of different quality. Also, we will trace the fate of 13C-labelled compounds to determine DOP turnover and the rate limiting steps in the mobilization process. By measuring P leaching with and without nutrient fertilization and from substrates with differing stoichiometry (C:P:N ratios), we can deduce if DOP production is driven by P availability or is rather a byproduct of soil organic matter cycling. In climate chambers, we will estimate the temperature dependency of P mobilization processes, which is a key factor in the P cycle.One possible cause for the mobility of dissolved P is colloidal transport. We, thus, will analyze soil solutions for colloids by ultracentrifugation. Binding to colloids can also explain the poor enzymatic hydrolyzability of DOP. The possible release of DOP from soil matrix-bound organic P compounds will be tested by separating DOP in P-rich and P-poor fractions, combined with 14C analyzes. Characterization of dissolved P will be carried out with 31P-NMR, which is often limited by the small amounts of P in subsoil solutions. Therefore, we will employ XPS with Ag anode excitation to determine P binding forms in small samples. Part of the project will be dedicated to the development of this new method.In order to generalize the obtained results, we will determine dissolved P in soil waters sampled sporadically at a number of additional forest sites. Finally, we will contribute to the synthesis on transport- and flux-related results within main project, which is a prerequisite for the modeling of the P cycle in forest ecosystems.

在生态系统发育过程中，森林生态系统逐渐从对岩石磷的获取转变为对有机磷的再循环。正磷酸盐和溶解性有机磷（DOP）在有机层中释放，部分淋溶到矿质土壤中。我们的研究结果在第一阶段的主要项目表明，减少正磷酸盐的有机层的淋溶增加森林生态系统的再循环趋势。相比之下，DOP并没有下降太多。大多数DOP不能被酶水解，因此生物利用度很小。在矿质土壤中，正磷酸盐随深度的增加而减少; DOP的下降不那么强烈。可能的是，DOP大大有助于从所有森林生态系统的稳定的磷流失，但也正磷酸盐是不完全保留在矿质土壤。然而，控制溶解磷的差异生产的因素，在有机层的收购和回收森林生态系统没有解决。本研究旨在探讨磷在森林生态系统中的迁移和淋溶的机制和控制，通过测定土壤有机层中磷的形态释放和DOP的生物有效性来评价土壤有机层中磷的迁移。此外，我们将跟踪13 C标记的化合物的命运，以确定DOP营业额和动员过程中的限速步骤。通过测量有和没有养分施肥和不同化学计量比（C：P：N比）的基质中的P淋失，我们可以推断DOP的产生是由P的可用性驱动的，还是土壤有机质循环的副产品。在气候室中，我们将估计磷活化过程的温度依赖性，这是磷循环的一个关键因素。溶解磷的流动性的一个可能原因是胶体运输。因此，我们将用超离心法分析土壤溶液中的胶体。与胶体的结合也可以解释DOP的差的酶促水解性。通过分离富磷和贫磷组分中的DOP，结合14 C分析，测试DOP从土壤基质结合有机磷化合物中的可能释放。溶解磷的表征将进行与31 P-NMR，这往往是有限的底土溶液中的少量的P。因此，我们将采用XPS与银阳极激发，以确定小样品中的P结合形式。该项目的一部分将致力于开发这种新方法。为了推广所获得的结果，我们将在一些额外的森林站点零星取样，确定土壤沃茨中的溶解磷。最后，我们将有助于综合运输和通量相关的结果在主项目，这是一个先决条件的森林生态系统中的P循环建模。