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.

在生态系统开发过程中，森林生态系统逐渐从岩石P的获取转变为有机邻磷酸盐和溶解有机P（DOP）的回收，在有机层中释放，并部分渗入矿物质。我们在主要项目的第1阶段获得的结果表明，随着森林生态系统的回收趋势的增加，从有机层的正磷酸盐浸出。相比之下，DOP并不多。大多数DOP是不可酶的水解，因此生物利用度很少。矿物质土壤中的磷酸盐随着深度而降低； DOP的下降不那么强劲。 DOP可能会导致所有森林生态系统的稳定p损失，但也没有完全保留在矿物质土壤中。然而，无法解决收集和回收森林生态系统中有机层中溶解P差异产生的因素。此外，尚未完全了解稳定溶解P的稳定浸出的原因。拟议的工作旨在探索森林生态系统中P动员和P浸出的机制和控制。有机层中P的P型将通过测量P形式和dop Bioabaibaility in spppp-Ircorm conter和micrecors中的释放来评估P形式和dop生物生理性的范围。另外，我们将追踪13C标记化合物的命运，以确定动员过程中的DOP周转和速率限制步骤。通过测量有或没有养分受精的P浸出以及具有不同化学计量法的底物（C：P：N比），我们可以推断出DOP的产生是由P的可用性驱动的，或者是土壤有机物循环的副产品。在气候腔中，我们将估计P动员过程的温度依赖性，这是P周期中的关键因素。溶解P的迁移率的一种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的胶体溶液。与胶体的结合还可以解释DOP的酶促水解性差。通过将PICH和P-POOR较量分数分开的DOP与14C分析相结合，可以通过将DOP从土壤基质结合的有机P化合物中释放出来。溶解P的表征将使用31p-NMR进行，通常受到较小的土壤溶液中少量P的限制。因此，我们将使用具有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。为了概括所获得的结果，我们将在许多其他森林地点偶尔采样的土壤水中溶解的P。最后，我们将为主要项目中的运输和通量相关结果的综合做出贡献，这是森林生态系统中P周期建模的先决条件。