Influence of total interception on the surface runoff in a decline mountain spruce forest

In the last decade, dieback has affected not only non-native monoculture spruce forests at lower altitudes but also mountain spruce forests. For this reason, measurements of precipitation, throughfall, and surface runoff were carried out in the dead and living parts of the spruce forest, as well as in an open area with no trees. The dead stand was largely composed of standing dead trees. The goal of this study was to determine the values of surface runoff after dieback, considering the significant influence of precipitation amount and total forest interception. Canopy interception, total interception, and surface runoff were observed in a decline mature mountain spruce stand during three growing seasons: 2018–2020. This research was conducted at the upper forest line, at an altitude of 1,420 m a.s.l. in the western part of the Western Tatras. Data collection occurred at approximately two‐week intervals. The evaluated growing seasons began at the end of May and concluded at the end of October, with the exception of the growing season of 2020, when measurements finished at the beginning of October. Surface runoff represented the following average values for the growing seasons of 2018‐2020: 3.7%, 3.7%, and 8.1% in the living forest; 2.3%, 1.9%, and 3.0% in the dead forest; and 2.9%, 3.2%, and 3.2% in an open area, all relative to the recorded gross precipitation totals. Occult precipitation significantly influences canopy interception values in these locations, increasing the amount of throughfall recorded under the stand. Consequently, the average interception in the living forest during the growing season of 2020 was ‐1.1% of the gross precipitation total. Total interception reaches significantly higher values in both stands compared to canopy interception.