Plant communities and their relations to habitat and microhabitat features along a management gradient in beech forests in Denmark

Abstract

Aims

Many empirical studies have found neutral or positive effects of forestry on plant alpha diversity in temperate deciduous forests, reflecting a positive effect of soil and canopy disturbances caused by forestry operations. The level to which this positive response to artificial disturbances mimics processes in natural forest ecosystems is less clear; hence, the systemic effects of forest management on ground floral communities remain obscure.

Location

Temperate Europe, Denmark.

Methods

We studied communities of ground-dwelling bryophytes and vascular plants in 400 plots distributed across 40 beech stands across four classes of forest management intensity – long unmanaged, recently unmanaged, near-to-nature managed, and shelterwood managed – while recording the incidence of a diverse array of microhabitats related to hydrology, canopy closure and soil disturbance.

Results

Microhabitat availability differed considerably among forest management classes as a response to management. Overall, forest management had a significant positive effect on the plot-level alpha diversity of both vascular plants and bryophytes. In contrast, beta diversity and total ecospace decreased with forest management intensity. Litter accumulation simultaneously decreased alpha diversity in both groups, while light availability, soil exposure and presence of wetlands respectively, were crucial for vascular plant and bryophyte richness. Forestry-created canopy gaps had a similar effect on alpha diversity as natural tree-fall gaps but supported a different set of species, mainly ubiquitous generalists.

Conclusions

Even if plant alpha diversity was lower in unmanaged forest stands, this did not significantly affect gamma diversity across the sampled stands, suggesting that plant richness needs to be considered at a relevant scale when evaluating forest management impact on biodiversity. These scaling issues seem to reflect fundamental differences in disturbance dynamics in managed and unmanaged forest ecosystems, which are typically not well accounted for in monitoring and research. A better understanding of disturbance dynamics in forest ecosystems and their spatial impact on biodiversity is needed to guide ecological restoration and management for biodiversity in production forest.