Jiří Procházka

Fine-Scale Vertical Stratification and Guild Composition of Saproxylic Beetles in Lowland and Montane Forests: Similar Patterns despite Low Faunal Overlap.

Objective The finer scale patterns of arthropod vertical stratification in forests are rarely studied and poorly understood. Further, there are no studies investigating whether and how altitude affects arthropod vertical stratification in temperate forests. We therefore investigated the fine-scale vertical stratification of diversity and guild structure of saproxylic beetles in temperate lowland and montane forests and compared the resulting patterns between the two habitats. Methods The beetles were sampled with flight intercept traps arranged into vertical transects (sampling heights 0.4, 1.2, 7, 14, and 21 m). A triplet of such transects was installed in each of the five sites in the lowland and in the mountains; 75 traps were used in each forest type. Results 381 species were collected in the lowlands and 236 species in the mountains. Only 105 species (21%) were found at both habitats; in the montane forest as well as in the lowlands, the species richness peaked at 1.2 m, and the change in assemblage composition was most rapid near the ground. The assemblages clearly differed between the understorey (0.4 m, 1.2 m) and the canopy (7 m, 14 m, 21 m) and between the two sampling heights within the understorey, but less within the canopy. The stratification was better pronounced in the lowland, where canopy assemblages were richer than those near the forest floor (0.4 m). In the mountains the samples from 14 and 21 m were more species poor than those from the lower heights. The guild structure was similar in both habitats. Conclusions The main patterns of vertical stratification and guild composition were strikingly similar between the montane and the lowland forest despite the low overlap of their faunas. The assemblages of saproxylic beetles were most stratified near ground. The comparisons of species richness between canopy and understorey may thus give contrasting results depending on the exact sampling height in the understorey.

Vertical stratification of scolytine beetles in temperate forests

Although most studies exploring the vertical distribution of arthropods in forests have been limited to discrete comparisons between understorey and canopy, few have sampled across multiple heights. We studied vertical distribution of scolytine beetle flight activity in temperate lowland broadleaf and montane beech‐fir forests using flight interception traps arranged in vertical transects with traps placed 0.4, 1.2, 7, 14, and 21 m above ground. In each forest type 15 vertical transects (75 traps) were used. The assemblages sampled at 0.4 and 1.2 m above ground (undergrowth) clearly differed from those at 7, 14, and 21 m (midstorey and canopy). Ambrosia‐fungi feeder abundance peaked at 1.2 m in the mountains, whereas in the lowland they were almost evenly distributed from 1.2 to 21 m. Phloem feeders were significantly more abundant in the midstorey and canopy than in the undergrowth. Height preferences of eleven species were identified. Four species were associated with traps exposed at 7, 14, or 21 m, whereas seven species were associated with the height of 1.2 m. No species was associated with the 0.4 m height. To cover entire scolytine assemblages of forest stands, sampling should thus not be restricted to the usually sampled understorey level, but also cover the canopy.