Technical note: A weighing forest floor grid lysimeter

Abstract. The forest floor (FF) is dominated by plant litter and its decomposition products, whereby it differs significantly from mineral soil. Because of its wider range of pore sizes and overall high porosity, it has a large capacity to retain water and thus plays an important role in redistributing water to the mineral soil beneath. Until now, most studies have focused on the behaviour of the organic layer when wetted and dried in a laboratory setting. Alternatively, fresh field samples were collected to determine water storage potential. We present a novel low-cost grid lysimeter designed specifically for the FF but that is also suitable for other organic soil layers. It can continuously measure all water balance components of the FF. The lysimeter detects precipitation with an accuracy of 0.03 mm, outperforming most rain gauges. The developed setup allows for further customization of in situ water quality measurements. This technical note describes the setup of the lysimeter and presents performance metrics from laboratory results and initial field data.