After rain comes sunshine: canopy and forest floor interception

02. Februar 2012, 16 ct - 18 Uhr Hörsaal Fahnenbergplatz (Rektoratsgebäude) / Miriam Coenders - TU Delft, Niederlande

(PresseBox) (Freiburg, ) Interception is the part of the rainfall that is captured by the earth's surface and which subsequently evaporates. How much of the precipitation evaporates depends on land cover characteristics, rainfall characteristics, and on the evaporative demand. Interception can amount up to 15-50% of precipitation, which is a significant part of the water balance. In this study we focus on canopy and forest floor interception. We measured interception of three dominant European vegetation types at three locations. In the Huewelerbach (Luxembourg) a beech forest has been investigated, in Westerbork (the Netherlands) grasses and mosses, and in the Botanical Garden (Delft, the Netherlands) a Cedar tree. Canopy interception is determined by the difference between gross precipitation and the sum of throughfall and stemflow. To measure forest floor interception a special device has been developed. It consists of two aluminium basins which are mounted above each other. The upper basin is permeable and contains the forest floor. By weighing both basins simultaneously, evaporation from interception can be calculated.

We found that canopy interception has a clear seasonal trend ranging from 15% of rainfall in summer to 7% in winter for the beech forest. On the other hand, forest floor interception appears to be constant over the year and evaporates on average 22% of throughfall.

Spatial throughfall patterns were also investigated, and showed the persistence of hotspots (locations with concentrated throughfall) and the importance of tree structure for throughfall patterns. By use of a 'virtual experiment' the effect of these throughfall patterns on soil moisture was analysed with a developed statistical tool.

In this presentation I will elaborate on the measuring techniques, the results, and the analysis of the data with different model approaches.

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