Below-canopy and topsoil temperatures in young Norway spruce and Carpathian birch stands compared to gaps in the mountains

Reduced air pollution load has allowed to use commercially oriented forestry in the Central European mountains since the 1990s. The goal is, however, to restore species- and age-diversified stable stands that are expected to cope with uncertain changes of the harsh mountain climate. The microclimate of current young forest stands can impact on growth and performance of underplanted seedlings. In the present study, aboveground (+10 cm), surface (0 cm) and belowground (-10 cm) temperatures were compared under Norway spruce and Carpathian birch canopies. Measurements were performed in 22-year-old Norway spruce and Carpathian birch stands and replicated three times. These measurements were compared with three adjacent gaps dominated by herbal vegetation. Temperatures were measured automatically during the growing periods 2011 and 2012. The research was conducted on Norway spruce on an acidic Spodosol forest site in the summit part of the Jizerské hory Mts., Czech Republic. Data were analysed using the Horn procedure of pivot measures. The highest variability of aboveground and soil surface temperatures was observed within the gaps during a spring time. The temperatures beneath the leafless birch were close to those within the gaps, whereas in the period of leaved trees the temperature extremes were reduced similarly like under the spruce stand canopy compared to the gaps. The differences between the plots were the smallest at the end of growing seasons.