Understanding ecosystem P cycling and the various pathways by which P is transported is crucial for sustainable nutrient management. Colloid-facilitated transport of P is a poorly understood subsurface P flux pathway that may be particularly important in ecosystems with coarse-textured soils and minimal surface runoff. This study examines subsurface transport of dissolved (as defined as P <3 kDa) and particulate P in well-drained forest soils of two coniferous (pine) sites and one deciduous (oak) site. Total, dissolved and particulate (>0.45 μm and >3 kDa) groundwater P fluxes were quantified, as well as surface total P fluxes via litterfall and litter leachate. Our central hypothesis is that particulate and/or colloid-associated subsurface P flux exceeds that of dissolved P flux as a result of dissolved P sorption to mobile and stationary Fe- and Al-rich solid phases present in the soil. Results show that dissolved P flux (<3 kDa) was below detection in groundwater samples from all study sites, with the P within groundwater being dominated by particulates >0.45 μm. Overall, P fluxes from subsurface P pools (soils, groundwater) at all sites were one to three orders of magnitude lower than surface P inputs from litterfall and litter leachate, suggesting a highly efficient system for P conservation with minimal P losses below the root zone.

中文翻译：

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排水良好的森林土壤中的地下磷通量小且以颗粒物为主

了解生态系统磷循环和磷运输的各种途径对于可持续养分管理至关重要。胶体促进磷的运输是一种知之甚少的地下磷通量途径，这在具有粗糙土壤和最小地表径流的生态系统中可能特别重要。本研究检查了两个针叶（松树）地点和一个落叶（橡树）地点的排水良好的森林土壤中溶解的（定义为 P <3 kDa）和颗粒磷的地下传输。对地下水总磷通量、溶解磷通量和微粒（>0.45 μm 和 >3 kDa）以及通过凋落物和垃圾渗滤液产生的地表总磷通量进行量化。我们的中心假设是，由于溶解的 P 吸附到土壤中存在的流动和固定的富铁和铝固相，颗粒和/或胶体相关的地下 P 通量超过了溶解 P 通量。结果表明，所有研究地点的地下水样品中溶解的 P 通量（<3 kDa）低于检测值，地下水中的 P 以大于 0.45 μm 的颗粒物为主。总体而言，所有地点的地下磷库（土壤、地下水）的磷通量比来自凋落物和凋落物渗滤液的地表磷输入低一到三个数量级，表明一个高效的磷保护系统，根区以下的磷损失最小. 地下水中的 P 以大于 0.45 μm 的颗粒物为主。总体而言，所有地点的地下磷库（土壤、地下水）的磷通量比来自凋落物和凋落物渗滤液的地表磷输入低一到三个数量级，表明一个高效的磷保护系统，根区以下的磷损失最小. 地下水中的 P 以大于 0.45 μm 的颗粒物为主。总体而言，所有地点的地下磷库（土壤、地下水）的磷通量比来自凋落物和凋落物渗滤液的地表磷输入低一到三个数量级，表明一个高效的磷保护系统，根区以下的磷损失最小.