Phosphorus transport in lateral subsurface flow at forested hillslopes

Abstract. This study is concerned with the transport of Phosphorus (P) with lateral subsurface flow in the organic layer and topsoil of three forested headwater sites in Germany. Sampling frequency was set proportional to the incident flow rate in high temporal resolution. With this approach we want to investigate intra-event dynamics of P transport in lateral subsurface flow to establish initial process understanding about this potentially relevant pathway of P loss in forested hillslopes. With the organic layer being an important transfer site in the P cycle of temperate forests, availability and transportability of P in short timescales may reveal details about the overall balance of P in theses ecosystems. Our results demonstrate that P concentrations in lateral flow are highly variable within and in between distinct flow events as well as among our study sites. To determine possible controls of the P transport we constructed multiple linear models of the P concentration in lateral flow as a function of site specific environmental datasets. Site affiliation was responsible for more than half of total explained variability regarding P concentration in lateral flow, followed by flow rate, electric conductivity of subsurface lateral flow