Effects of forest structure, tree species, and weather conditions on the intra-annual variability of air temperature buffering in temperate forests

Air temperature buffering effects by forest canopies have important consequences for ecosystem functioning. Yet, knowledge about the relationship between forest structure and the intra-annual variability of air temperature buffering remains scarce. Here, we investigated the intra-annual variability of air temperature buffering by forest canopies using a paired design of weather stations in permanent forest plots (n = 134) of pure European beech, Norway spruce, and Scots pine as well as neighboring open lands (n = 48) on three sites in Central Europe. We found that air temperature buffering follows a seasonal pattern, with buffering effects being strongest during summer and weakest, or even absent, during winter. We then used terrestrial laser scanning (TLS)-derived measures of canopy openness and vertical structure to test whether the intra-annual variability of air temperature buffering is driven by forest structure and how these effects covary with weather conditions and landscape factors. For coniferous stands, forest structure explained on average 10.7% of variance in air temperature buffering throughout the year. For broadleaved stands, forest structure explained on average only 2.4% of variance in air temperature buffering during winter and 4.8% in summer. Overall, the most explained variance was attributable to weather conditions (Ø 40.8%) and landscape factors (Ø 13.0%), while forest structure explained only 8.3% on average. Our results suggest that the influence of forest management on air temperature buffering is limited within the studied forest types, highlighting a limited potential to mitigate the effects of climate change-related weather extremes on forest microclimate through adapted forest management and structures.