Beetle diversity is higher in sunny forests due to higher microclimatic heterogeneity in deadwood.

Microclimate is a crucial driver of saproxylic beetle assemblages, with more species often found in sunny forests than in shady ones. Whether this pattern is caused by a higher detectability due to increased beetle activity under sunny conditions or a greater diversity of beetles emerging from sun-exposed deadwood remains unclear. This study examined whether sun exposure leads to higher microclimatic heterogeneity in deadwood and whether this drives beetle diversity in deadwood logs and at forest stand scale. Saproxylic beetles were sampled at the stand scale using flight-interception traps and at object scale using stem-emergence traps on deadwood logs at the same site. The variability in wood surface temperature was measured on single logs and between logs as a proxy for microclimatic heterogeneity in deadwood. Abundance in sunny forests was higher at the stand scale, and in shady forests at the object scale. The estimated number of species was higher in sunny forests at both scales and correlated positively with temperature variability on single logs and between logs at the stand scale and, albeit weakly, with temperature variability on single logs at the object scale. Gamma-diversity, and thus beta-diversity, across logs at the object scale was higher in sunny forests. These findings indicate that sun exposure promotes saproxylic beetle diversity due to higher microclimatic heterogeneity within and between deadwood logs. Our study therefore corroborates previous research demonstrating the importance of canopy cover and microclimate for forest biodiversity.

Importance of meteorological and land use parameters for insect diversity in agricultural landscapes.

Human-induced climate and land-use changes are important factors influencing global insect diversity. Nevertheless, the influence of weather on biodiversity is still relatively rarely studied. Grassland insects may be the taxon that is most affected by changing weather. We focused on the influence of weather and land-use management on butterflies in hayed meadows in the Czech Republic. During two consecutive years (2019-2020), we studied nearly 300 independent meadows. The abundance of butterflies was more influenced by the weather than their species richness. We observed positive and mainly linear effects of increasing vegetation temperatures. One very influential variable was the light intensity, which had a nonlinear effect that promoted butterflies under direct sunlight. The humidity had mainly moderate, nonlinear effects. Surprisingly, the wind had only a small effect. We observed important effects of the flowering intensity and vegetation height on the butterfly species richness and abundance regarding land use. Marginal woody vegetation cover had a positive effect on the butterfly abundance, and management had little effect. We concluded that weather and land use had important effects on butterflies. Based on our research, we recommended the reconsideration of scientific studies and monitoring programs for insects concerning the temperature threshold (≥ 25 °C) and the consideration of light intensity as an important factor. Applying a detailed approach to measuring the flowering intensity is likely unnecessary, while meadow land-use parameters appear to be necessary for insect populations.