Abstract
The assessment of impacts of an altered nutrient availability, e.g. as caused by consistently high atmospheric nitrogen (N) deposition, on ecosystem phosphorus (P) nutrition requires understanding of P fluxes. However, the P translocation in forest soils is not well understood and soil P fluxes based on actual measurements are rarely available. Therefore, the aims of this study were to (1) examine the effects of experimental N, P, and P+N additions on P fluxes via preferential flow as dominant transport pathway (PFPs) for P transport in forest soils; and (2) determine whether these effects varied with sites of contrasting P status (loamy high P/sandy low P). During artificial rainfall experiments, we quantified the P fluxes in three soil depths and statistically analyzed effects by application of linear mixed effects modeling. Our results show that the magnitude of P fluxes is highly variable: In some cases, water and consequently P has not reached the collection depth. By contrast, in soils with a well-developed connection of PFPs throughout the profile fluxes up to 4.5 mg P m−2 per experiment (within 8 h, no P addition) were observed. The results furthermore support the assumption that the contrasting P nutrition strategies strongly affected P fluxes, while also the response to N and P addition markedly differed between the sites. As a consequence, the main factors determining P translocation in forest soils under altered nutrient availability are the spatio-temporal patterns of PFPs through soil columns in combination with the P nutrition strategy of the ecosystem.
Highlights
The biogeochemical cycles of nitrogen (N) and phosphorus (P) in forest ecosystems are assumed to be closely synchronized, especially in ecosystems relyingBiogeochemistry on tight recycling of nutrients
The degree of response of the soil P cycle might be dependent on the prevailing nutrition strategy and on the ability of an ecosystem to adapt to alterations in nutrient availability
In Makowski et al (2020b), we described the results for preferential flow distribution and P translocation during three sequential artificial irrigations at the three control plots of the two sites
Summary
The biogeochemical cycles of nitrogen (N) and phosphorus (P) in forest ecosystems are assumed to be closely synchronized, especially in ecosystems relyingBiogeochemistry on tight recycling of nutrients. The close relationship of different nutrients in ecosystems is affected by significantly higher loss or addition of one nutrient relative to the other, which induces adaption processes of organisms to maintain their required stoichiometry (Chapin et al 1987; Rastetter et al 1997). Changed environmental conditions, such as rising atmospheric CO2 concentrations and temperature, enforce these processes. The driving processes of P mobilization and transport under conditions of an altered nutrient availability in forest
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