Quantifying components of the phosphorus cycle in temperate forests

We review the state‐of‐the‐art of cross‐disciplinary knowledge on phosphorus (P) cycling in temperate forest ecosystems, focused at studies from hydrology, biology, biogeochemistry, soil‐, and geosciences. Changes in soil P stocks during long‐term ecosystem development are addressed briefly; the general ranges of specific P pools and P fluxes within the ecosystem and the presumed underlying processes are covered more in depth. Wherever possible, we differentiate between coniferous and deciduous forests. As the most important P pools, mineral soil, forest floor, vegetation, and microbial biomass are described in terms of pool size, molecular composition, and turnover. Litterfall, soil water seepage, atmospheric deposition, and biotic uptake as the most studied P fluxes in the forest ecosystem are discussed in detail, spotlighting biogeochemical processes relevant for mobilization and retention of P in the rooting zone. Through a meta‐analysis of available literature, we build a dataset that allows the quantification of major P‐cycle components in temperate forests in terms of range and distribution, highlighting similarities and differences between coniferous and deciduous forests. The two forest types are notably distinct in their distribution of P within compartments of the plant biomass and forest floor. The possibility to construct closed local P balances is often hindered by missing information on fluxes of dissolved and particulate P across the ecosystem boundary, be it in the atmosphere, soil, or on the surface. These fluxes are irregular in space and time and feature large overall mass fluxes but comparatively small P fluxes, making the latter one difficult to quantify. WIREs Water 2017, 4:e1243. doi: 10.1002/wat2.1243 This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Science of Water > Water Quality