Better forest management boosts beetle diversity in spruce plantations hit by bark beetles

As climate change and pests put increasing pressure on forests, the right forest management practices are emerging as key to preserving biodiversity. A new study published in Forest Ecosystems explores how different management strategies affect beetle diversity in spruce plantations severely impacted by bark beetle outbreaks.

The research, conducted in the “Montabaurer Höhe” forest in western Germany, examined five forest management approaches, including non-intervention deadwood stands and salvage logging, in areas affected by bark beetles. The study focused on ground-dwelling and flight-active beetles, which are vital to forest ecosystems, acting as decomposers and pollinators. Researchers from University of Koblenz set out to understand how these practices influence beetle populations and overall biodiversity.

“Our study shows that non-intervention deadwood stands, where no further forestry work was done, supported the most diverse beetle communities,” said Eva Plath, lead author of the study. “This finding suggests that leaving some areas undisturbed after disturbance events, like bark beetle outbreaks, can significantly benefit biodiversity.”

Over the course of the study, researchers collected over 13,000 beetles from 442 species. The results showed that deadwood stands, left untouched after the dieback, supported the highest diversity of beetles, including several rare and endangered species. In contrast, salvage-logged areas, where trees were removed after the outbreak, had lower beetle diversity. This was particularly true for species that thrive in open, undisturbed habitats, which were scarce even in cleared areas.

The study highlights the significant role of forest management in promoting or hindering biodiversity, especially in forests undergoing post-disturbance recovery. The researchers found that ground-active beetles favored areas with dense canopies and few tree stumps, while flight-active beetles preferred more open areas with rich plant diversity. This shows that the structure of the forest after disturbance—whether through salvage logging or non-intervention—can dramatically shape the beetle community.

To improve biodiversity conservation, the team recommends a mixed management approach that combines areas of non-intervention deadwood with more open patches of diverse vegetation. Such a strategy could enhance landscape heterogeneity and connectivity, benefiting both forest ecosystems and the species that depend on them.