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.

在生态系统发展过程中，森林生态系统逐渐从岩石磷的获取转变为有机磷的循环利用。正磷酸盐和溶解性有机磷（DOP）释放在有机层中，部分淋滤到矿质土壤中。我们在主项目第一阶段获得的结果表明，随着森林生态系统循环趋势的增强，有机层中正磷酸盐的浸出量有所减少。相比之下，DOP下降幅度并不大。大多数 DOP 不可酶水解，因此生物利用度很小。正磷酸盐随着矿质土壤深度的增加而减少； DOP 的跌幅较弱。 DOP 很可能对所有森林生态系统磷的稳定流失做出了重大贡献，但正磷酸盐也没有完全保留在矿质土壤中。然而，控制森林生态系统获取和循环利用有机层中溶解磷生产差异的因素尚未得到解决。此外，溶解磷稳定淋滤的原因尚不完全清楚。拟议的工作旨在探索森林生态系统中磷的动员和淋滤的机制和控制。有机层中磷的动员将通过测量释放来评估在 SPP 施肥实验和不同质量有机质的微观世界中，P 形式和 DOP 生物利用度的影响。此外，我们将追踪 13C 标记化合物的命运，以确定 DOP 周转率和动员过程中的限速步骤。通过测量有或没有养分施肥以及不同化学计量（C:P:N 比率）的基质中 P 的浸出，我们可以推断 DOP 的生产是由 P 的有效性驱动的，还是土壤有机质循环的副产品。在气候室中，我们将估计磷移动过程的温度依赖性，这是磷循环的关键因素。溶解磷移动的一个可能原因是胶体运输。因此，我们将通过超速离心分析土壤溶液中的胶体。与胶体的结合也可以解释 DOP 酶水解性差的原因。将通过分离富磷和贫磷部分中的 DOP 并结合 14C 分析来测试 DOP 从土壤基质结合的有机磷化合物中可能释放的情况。溶解磷的表征将通过 31 P-NMR 进行，这通常受到底土溶液中少量磷的限制。因此，我们将采用带有 Ag 阳极激发的 XPS 来确定小样品中的 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，我们将测定在许多其他森林地点零星采样的土壤水中的溶解磷。最后，我们将在主要项目中贡献与运输和通量相关的结果的综合，这是森林生态系统中磷循环建模的先决条件。