Wood ants play a significant role in forest biodiversity – project seeks ways to protect Ant nests during regeneration felling

Wood ants are essential to the functioning of forests. Their mounds provide habitats for hundreds of other species and help control pests. The PPP project, coordinated by the Natural Resources Institute Finland (Luke), investigates forest management methods that could enhance the survival of wood ant nests in regeneration felling areas.

In boreal forests, wood ants are key to maintaining biodiversity. Their nest mounds offer habitats for numerous insects, arachnids, and other invertebrates, many of which live exclusively in wood ant nests.

Entire food chains have formed within these mounds. For example, certain beetles only feed on wood ant eggs and larvae during their larval stage. Additionally, trees growing near nest mounds are faster-growing and sturdier than those further away. This is because the organic material in the mounds, such as needles and twigs, is converted through microbial activity into nutrients that trees and plants can use.

Wood ants also help control forest pests, such as the spruce bark beetle and possibly even the European spruce bark beetle, which threaten forest biodiversity and the forests' ability to bind carbon.

However, wood ant nests often become deserted after regeneration felling because the ants’ food sources, such as aphids, diminish, and the microclimate of the mounds changes. After felling, the nests can dry out due to wind or become too wet, disrupting the mounds' temperature regulation.

Luke's Public-Private Partnership funded (PPP) AntForest project studies the impact of various forest management methods on the survival of wood ant nests and the presence of invasive species in them. The project seeks ways to improve the survival of wood ant nests during regeneration felling, thereby promoting the biodiversity of commercial forests.

How do retention tree groups affect nest mounds?

Retention tree groups are clusters of trees left uncut during regeneration felling to promote forest biodiversity. These groups provide habitats for various species that benefit from the shelter and resources provided by the retention trees.

The research project investigates how the size and placement of retention tree groups affect wood ants and the preservation of their nests. The research areas are located in southern Finland, between Lake Oulujärvi and the Salpausselkä ridges.

"We want to determine the optimal size of retention tree groups around wood ant nests to help them recover after felling. Previous studies have shown that the survival of wood ants can be enhanced if the nests are located closer to the forest edge," says Jouni Sorvari, Luke’s research scientist coordinating the project.

According to Tiina Laine, forestry manager at Metsä Group, the research supports their goal of being a leader in ecological sustainability.

"The project approaches forest biodiversity practically by producing forest management guidelines that better consider the important nest mounds during felling," says Laine.

Nest mounds bind carbon

The carbon storage capacity of nest mounds has not been previously studied, but according to Sorvari, mounds could be significant carbon stores relative to their size. When nest mounds are abandoned, they decompose quickly and release their stored carbon back into the atmosphere. Nest mounds may contain more carbon than their exterior suggests.

Luke's methods can determine how much carbon is stored in different layers of the mounds. The surface layer is dense, composed of needles and small plant fragments, while the core is made of coarser material. At the bottom of large mounds, there is a condensed, peat-like mass that has been processed for a long time.

Practical guidelines and tools for forest management

The project provides tools for the forestry sector to maintain the biodiversity and sustainability of commercial forests. It will develop publicly available forest management recommendations to preserve wood ant nests during regeneration felling. These guidelines will help forest owners and forestry operators support biodiversity.

"Our goal is to create a predictive model to help calculate the probability of wood ant nests occurring in forest areas. The model will help forest owners and forestry companies consider important wood ant nests," Sorvari says.

According to Laine, it is crucial to know the locations of ant nests and ensure that retention tree groups protect them.

"Retention trees are always left during forest felling. With location information, we can place the retention trees to best support biodiversity," Laine says.

AntForest-project

Project duration:

• 1.2.-2024-31.1.2027

Partner:

• the Swedish University of Agricultural Sciences (SLU)

Funders:

• Metsä Group Treasury Ltd.
• Metsähallitus Metsätalous Ltd.
• Stiftelsen Skogssällskapet
• Stora Enso Plc