A recipe for healthier forests? Less clearing, more fallen wood. Biodiversity can be boosted when even small amounts of wood are left behind

A scientific study published in the journal Forest Ecosystems reveals that even very small amounts of fallen wood left in commercial spruce stands can make a significant contribution to biodiversity conservation without significantly reducing wood production.

3 Jul 2025 Iva Labudová Kevin Francis Roche

Typical view of a spruce monoculture stand, with no fallen wood or herbaceous vegetation. Instead, a thick layer of needles accumulates due to slow decomposition, creating an extremely acidic environment in which very few organisms can survive.

A research team from Masaryk University’s Faculty of Science has found that leaving at least 4 m³ of large fallen wood per hectare in economic spruce forests helps maintain the diversity of terrestrial snails, which act as bioindicators of a healthy forest environment. These molluscs also represent the needs of other organisms associated with dead wood, including microorganisms, fungi and invertebrates. These organisms are crucial for the stability and resilience of forest ecosystems.
"Snails were chosen as a model group because of their sensitivity to environmental change and low mobility. They are also ideal representative species for assessing biodiversity in forest soil and on fallen wood", explains the study's lead author, Kristina Svobodová.
The study showed that the amount of fallen wood had a positive influence not only on snail diversity but also key soil properties, such as moisture and pH, as it retains water, mitigates soil acidity and provides shelter during extreme temperature fluctuations.
“Leaving behind a small amount of wood — especially an extremely small amount such as 4 m³/ha — has no significant impact on the amount harvested. Nevertheless, the approach can be a highly effective and inexpensive way of promoting biodiversity” added study co-author Michal Horsák.
To achieve an optimal situation providing significant support for sensitive and endangered species, the researchers recommend targeting up to 20 m³ of fallen timber per hectare, though a minimum of 4 m³/ha may represent a more realistic and feasible limit for forestry practice.
Right now, scientists are seeking adaptation measures to address the issues of climate change and bark beetle infestation, both of which represent a particular threat to spruce monocultures. Measures such as leaving wood to decompose directly in the forest and increasing forest environment diversity by promoting growth of more broadleaved species are good examples. In this respect, snails can serve as an umbrella group for the wider protection of soil biodiversity.

Contact:
Mgr. Kristina Svobodová
Department of Botany and Zoology, Masaryk University, Faculty of Science 
Kotlářská 2, 602 00 Brno
E-mail: kristina.svoby@seznam.cz, Tel.: +420 608 052 579

Image from a nature reserve where large fallen logs serve as shelter from the weather, supply nutrients to the soil and raise local pH levels. Photo: Kristina Svobodová.
Representatives of the family Clausiliidae. These snails are sensitive to environmental change and serve as bioindicators of well-preserved forests with plenty of dead wood. From left: Bulgarica cana, a species requiring structured forest with an abundance of decaying wood, and the Macrogastra venticosa. Photo: Michal Horsák.
Typical gastropods surviving in the harsh conditions found in spruce monocultures, usually in places with higher local humidity, fallen leaves or fallen wood, which often provide the only refuge in an otherwise acidic environment covered with spruce needles. From left: Euconulus fulvus, the Punctum pygmaeum, our smallest gastropod with a shell that measures just 1.6 mm, and the Perpolita hammonis. Photo: Michal Horsák.

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