Deadwood enrichment

What

Standing and downed deadwood in the form of snags, logs, branches and stumps is retained during various management activities and/or  created, with the objective to increase the quantity and diversity of this essential component in forests and other ecosystems.

Where

The deadwood enrichment can be used as part of a NbS in the forest and urban ecosystems as a part of closer-to-nature management and ecological restoration. Deadwood enrichment can also be used in wetlands and cultural landscapes. 

Why

In Nordic forest ecosystems, timber harvesting, fire suppression and salvage logging reduce deadwood abundance and diversity, and climate change is expected to change input (through natural disturbances) and output (through decomposition) rates of deadwood in space and time.

Around 7,500 forest species in the Nordic countries are associated with deadwood, and hundreds of species are threatened because of the shortage in availability of deadwood. The importance of deadwood for biodiversity, carbon sequestration and ecosystem functioning has been recognised not only in forests, but also in aquatic ecosystems, such as rivers and streams, as well as wetlands and coastal areas. In urban ecosystems and cultural landscapes, deadwood benefits biodiversity and ecosystem services, as well as can be important for environmental education.  

Thus, restoring a continuous supply of diverse deadwood is vital to reverse the negative trends in decreasing biodiversity and the ecosystem’s ability to adapt to change. Deadwood enrichment addresses a range of societal challenges: 

  • Enhances biodiversity by means of providing ecological niches and food for a range of living organisms. 

  • Addresses the societal challenge of climate change mitigation and adaptation through carbon sequestration for decades or hundreds of years in large-diameter deadwood in particular, and through increased carbon sequestration in forest soil by carbon inputs from deadwood into the soil, 

  • Reduces the risks of diseases through the diversity of deadwood-associated species that enhance an ecological resilience to pests, thus promoting ecosystem health, and disaster risk and preparedness. 

  • Promotes ecosystem productivity and timber production of forest ecosystems by improving soil fertility through organic matter and nutrient inputs from deadwood, as well as through providing a seedbed for natural tree species regeneration, thus promoting economic development. 

How

The cheapest and simplest solution is retention of all existing deadwood. Creation of new deadwood is beneficial especially if the quantity and diversity of existing deadwood is low. The objective is to ensure a continuous presence of a diverse  deadwood in different stages of decomposition and thereby a range of niches for deadwood-associated biodiversity. 

A short-term enrichment of deadwood can be achieved by careful sparing of existing deadwood and creation of new deadwood by: 

  • Mapping existing deadwood to avoid destroying it during management operations
  • Creating snags and high tree stumps – future downed deadwood
  • Killing of targeted trees by girdling, felling or pulling, inoculating with fungal pathogens or combination of these techniques.

Long-term solutions aiming at enabling a continuum of a diverse deadwood  include:

  • Creation of deadwood in mature forests to accelerate development towards near-natural state
  • The retention of single trees or groups of living trees in final and intermediate fellings
  • Partial or complete retention of damaged and dead trees in connection to or instead of salvage logging after natural disturbances such as windthrows, insect outbreaks or fires
  • Prescribed burning 

In cultural landscapes and gardens, the deadwood habitats can be retained or created in form of individual, preferably large, standing or downed dead trees, log piles, wood stacks, stumperies, and wooden fences. In urban ecosystems, the deadwood can be spared and created in parks and other urban green spaces, and used in green roofs, built ponds, basins, artificial wetlands, and creeks including cased streams. Moreover, it can attract people in art exhibitions and ecotrails. Deadwood art is an education material and have been used as a source of inspiration for several NbS interventions. 

Major points worth bearing in mind when considering deadwood management

When retaining living trees, tree groups are usually better than individual trees, to support a continuity of microclimate. Groups of trees of various species, age and size with tree undergrowth and deadwood are ideal. However, to ensure that old and large retention trees are chosen over small-diameter trees, individual trees can also be retained.    

Desired characteristics of trees include old age and large size, as well as damage or hollow parts, as these characteristics increase the number of microhabitats that the tree can offer for a variety of species associated with weakened or dead trees. Younger trees that are deemed to have the potential of reach old ages are also preferred to ensure temporal continuity in the provision of deadwood microhabitats.  

All deadwood should be retained in all kinds of silvicultural treatments in forest and mountain ecosystems, except in cases where there is a risk of insect outbreaks. Created deadwood includes a range of:

  • standing dead trees
  • downed deadwood 
  • stumps of various heights
  • range of tree species 
  • range of decay classes, as a results of repeated interventions
  • preferably both at shaded and sun-exposed locations. 

Potential outcomes

The immediate and long-term positive effects include improved biodiversity, multiple ecosystem services in forest ecosystems, e.g. carbon sequestration, tree stand productivity, soil quality . In urban ecosystems and cultural landscapes, deadwood enrichment brings biodiversity and carbon sequestration benefits, and increases general awareness of people about sustainability issues through environmental education. 

Possible negative side effects can be related to risks of pests and diseases, fire, and safety.  

ATTENTION

  • In forest ecosystems, retained habitat trees (trees with microhabitats such as nesting cavities) as well as fresh logs and snags can be a source of pests in the case of susceptible species (e.g. Norway spruce and bark beetle). This can bring economic losses to forest owners.  

  • Girdled living trees can be an entry point for unwanted tree pests and diseases. 

  • In urban ecosystems, retained habitat trees and snags can cause possible safety risk to public if close to roads, paths, etc. 

  • Applying prescribed burning in a NbS should be performed with caution to avoid uncontrolled spreading of fire. This needs to be negotiated with owners of neighbouring forests. 

  • People’s safety should be kept in mind when creating deadwood or performing prescribed burning. 

Costs 

  • No extra costs, if retaining living trees or tree groups and/or deadwood. However, there is a potential loss of financial revenue as the retention of individual trees or tree groups preferably involves trees of larger diameters desirable for timber extraction. 

  • Costs for deadwood creation are not very high if the treatment is made at the same time as timber harvesting.  

  • Prescribed burning is laborious and expensive. In Finland, for example, the costs of burnings are €1500–2500/hectare. Financial support for private land-owners is available in some of the Nordic countries. 

Specific location: private and public forests 

Which ecosystem type: Forests    

Title/name of the NbS: Deadwood enrichment 

Summary: deadwood enrichment using different methods 

Contact: Prof. Koivula Matti (LUKE), Natural Resources Institute Finland, matti.koivula@luke.fi 

Relevant links to documentation::  

Lahopuun turvaaminen - Kuvaus | Metsänhoidon suositukset (metsanhoidonsuositukset.fi), 

Lahopuu | Metsähallitus (metsa.fi), 

Metsien ennallistamismenetelmät | Metsähallitus (metsa.fi) 

ecological-restoration.pdf (metsa.fi) p.13 

Specific location: southern Finland, Evo region 

Which ecosystem type: Forests    

Title/name of the NbS: Deadwood enrichment through prescribed burning and downed deadwood creation. 

Summary: The projects focuses on the effects of prescribed burning, tree retention and downed deadwood creation on the deadwood profile in managed boreal Norway spruce forest stands over a 16-year period.  

Contact: Ekaterina Shorohova (LUKE), Natural Resources Institute Finland, ekaterina.shorokhova@luke.fi 

Relevant links to documentation: Deadwood enrichment in Fennoscandian spruce forests – New results from the EVO experiment - ScienceDirect 

Ecological background (ecological functions of deadwood):

  • Stokland J. and Alfredsen G. 2024. From deadwood to forest soils: quantifying a key carbon flux in boreal ecosystems. Biogeochemistry https://doi.org/10.1007/s10533-024-01170-y   

Deadwood enrichment in forests: 

  • Similä, M., & Junninen, K. (2012). Ecological restoration and management in boreal forests–best practices from Finland. Metsähallitus Natural Heritage Services, Vantaa. ecological-restoration.pdf (metsa.fi) Handbook on ecological restoration, including chapter on deadwood  

 Deadwood enrichment in other ecosystems: