Rainfall interception loss is rainfall retained by vegetation during rainfall event which then evaporated back into the atmosphere. Quantity of interception loss depends on a variety of vegetation and meteorological factors. In this thesis we deepen the knowledge of two rarely addressed factors, leaf area index (LAI) and microstructure of rainfall.
Measurements were carried out at the research plot adjacent to the building of the Department of Environmental Civil Engineering UL FGG in the center of Ljubljana, where grown two groups of trees: two silver birch (Betula pendula Roth.) and two black pine (Pinus nigra Arnold). The measurements of precipitation, throughfall and stemflow were carried out between August 2015 and June 2016, at the same time, we also measured the microstructure precipitation with disdometer. In the spring of 2016 we started with the measurements of leaf area index (LAI) for both considered tree species. LAI increase is very noticeable by the birch, which is the consequance of the growth of new leaves in spring. Within a short time period LAI increased from 1 to 2,5. In the case of pine, the changes are not so obvious, values of LAI are between 1,5 and 2,2.
The results show that in the observed period birch intercepted 19,2 % and pine 38,2 % of total rainfall. The interception was most affected by the total amount of precipitation, however the differences in the proportion of interception with the same amount of precipitation were due to the microstructure of precipitation (size and speed of the droplets) and LAI, related to the storage capacity of the tree crown. Trees intercept more when the droplets are smaller and slower, and LAI higher.