Plant and saproxylic beetle dynamics during succession in lowland temperate broadleaf forests reveal only short periods of increased diversity

Abstract

Forest succession, pivotal for biodiversity restoration after disturbance, lacks comprehensive comparisons among different taxa to elucidate mechanisms driving spatiotemporal diversity changes across trophic levels. While forest succession is generally understood, knowledge of multi-taxon succession in lowland temperate broadleaf forests is limited due to scarcity of large old-growth habitats and insufficient long-term multitrophic data.

We studied successional dynamics of understory plants and saproxylic beetles (xylophages, saproxylophages, saprophages, mycetophages and zoophages) in 91 oak-hornbeam forest stands and examined species richness of functional guilds and ecological traits across a chronosequence spanning 170 years of succession.

We discovered non-linear successional patterns in species richness and functional groups of both taxa. Peaks in diversity were observed in the early- and late-successional stages, with extended periods of lower diversity in the middle stages. The patterns were closely associated with fluctuations in light availability. Early-successional stages harboured light-demanding species, taller plants, and flower-visiting beetles, while middle stages were species-poorer, favoring organisms typical of shaded, moist environments. In late-successional stages, diversity increased again due to self-thinning and stand aging as succession progressed, but the values did not reach the state of early stages.

In temperate broadleaf forests, biodiversity fluctuates throughout succession, with brief peaks during the post-disturbance recovery phase and again later as trees age and canopy opens due to treefall. Effective conservation strategies should aim to maintain a heterogeneous canopy structure by applying partial cutting with retained trees and preserve old-growth attributes such as large deadwood and old trees, ensuring an open canopy around these elements.