The forest floor (FF) is a hydrologically highly relevant, but still only partially explored nexus between precipitation, throughfall or stem flow, evaporation, and infiltration into the soil. The influence of the FF on infiltration and the generation of overland flow and preferential flow and its spatial and temporal patterns have not been studied in detail. Leaching of dissolved organic matter (DOM) from the FF into the soil has partly been assessed. However, linking the spatial and temporal variability of water fluxes and storage in the FF with the fluxes of DOM, as well as feedback mechanism to the atmosphere (evaporation), is still a wide and open field of research.

Test of a low-cost miniature optical fiber spectrometer and development and test of system with FF in the lab and with artificial sprinkling experiments

Extend and further develop the concept of grid lysimeters, which allow to observe the spatial-temporal variability of water fluxes to the mineral soil, combined with a weighting forest floor lysimeter (Gerrits et al., 2010) to measure the variation of water storage (anticipated accuracy of 0.1 mm) in the forest floor, the throughfall fluxes and to determine evaporation from the FF. Each grid lysimeter should cover an area 25 cm x 100 cm with 4 individual grids. The concentration of DOC and its possible sources and dynamics will be inferred from optical absorbance and fluorescence measurements. Development of an in-situ system, combining the method of drop counters and EC measurement of the drops implemented in the new rain gauges (ATMOS) by METER with fibre-optic spectral and fluorescence systems, which will measure the spectral properties of each drop leaving the drop counter of each grid element in the lysimeter. The system will first be developed and tested with a laboratory UV-VIS spectrometer/fibre optic fluorometer to ensure initial success and then replaced with the Micro-spectrometer C12880MA from Hamamatsu Photonics. The final system should allow to measure EC, DOC concentration and DOM quality of every drop leaving the grid lysimeter.

Markus Weiler and Britta Kattenstroth

Markus Weiler markus.weiler@hydrology.uni-freiburg.de Tel. +49 (0)761 / 203-3530

Lab - and field work, 3D Printing, Spectrometry, technical development

Deutsch oder Englisch

Gerrits AMJ, Pfister L, Savenije HHG (2010) Spatial and temporal variability of canopy and forest floor interception in a beech forest. Hydrological Processes, 24(21), 3011-3025.