Leaching losses of N and C from the system – Work package 4.6

Changes in mineralization and immobilization processes caused by climatic changes may affect the ecosystem retention of nutrients. Consequently, changes in soil water chemistry may be used as a direct indicator for changes in these processes and soil water chemistry may directly be used to estimate the water-mediated loss of nutrients from the ecosystem. Therefore, treatment effects on leaching losses of C, N and P from the ecosystem will be studied to establish whether the changes in conditions we impose on the system will change the retention of soluble C, N and P compounds.

Leaching of N (NO₃^-, NH₄⁺ and DON), P (inorganic PO₄) and C (DOC) from the humic soil layer and from beneath the rooting zone will be determined from all experimental plots. Humic lysimeters (zero tension plates) will be installed at the depth of the organic layer and PTFE suction cups will be installed below the rooting zone from the start of the project to obtain sampling during the pretreatment year. Soil solution collected from the humic lysimeters and the suction cups will be pooled on a monthly basis an analyzed for inorganic N and P and dissolved organic N and C. More frequent sampling will be done in campaigns to capture changes in seasonality (e.g. spring advancement) or effects of extreme events (e.g. rewetting after drought). Leaching fluxes will be estimated by combining the soil solution concentrations and water fluxes calculated by a hydrological model (e.g. WATBAL). The studies of soil water chemistry will be coordinated with soil chemistry measurements in WP3.