Good forest means dead wood

There is a study by German researchers, led by people linked to the Bavarian Forest National Park, published in order to review global strategies towards dead wood and its relation to biodiversity.

According to the study the importance of dead wood for biodiversity is widely recognized but strategies for conservation exist only in some regions worldwide. However there are no evidences that the importance of dead wood for (forest) biodiversity is so widely recognised. Conservation professionals might understand that the existence and survival of a lot of species dependent on rotening timber, but the public perception does not seems to be even close to this understanding.

The researchers made global review of 79 experimental studies addressing biodiversity patterns in dead wood and identified major knowledge gaps and aim to foster collaboration among researchers by providing a map of previous and ongoing experiments. The study shows that research has focused primarily on temperate and boreal forests, where results have helped in developing evidence-based conservation strategies, whereas comparatively few such efforts have been made in subtropical or tropical zones.

Nationalpark Kalkalpen © Bart van Engeldorp Gastelaars

If one digs a bit further and tries to find evidences about the quantity of dead wood in managed forests in at least some of the European countries, the following data will appear:

  • Belgium (Lecomte, in press) 3,3 m3/ha deadwood in managed forests
  • Finland (Siitonen, 2001) 2-10 m3/ha
  • France (Vallauri et al, 2002) 2,23 m3/ha
  • Germany (Ammer, 1991) 1-3 m3/ha
  • Hungary (NÉBIH, 2014) 9,7 m3/ha
  • Sweden (Fridman and Walheim, 2000) 6,1 m3/ha
  • Switzerland (Brassel and Brandli, 1999) 12 m3/ha

Finland, Hungary and Swizerland seem to do well, but the devil lies in details! The authors stated that their meta-analysis confirms the benefits of dead-wood addition for biodiversity. However there are a few important facts, which the study naturally did not cover in its analysis of research gaps. These facts are (based on a recent presentation of György Csóka from the Hungarian Forestry Research Institute):

  • a lot of thin dead wood does not substitute thick dead wood
  • the laying dead wood does not support species dependent on standing dead wood
  • if there is 200 m3 dead wood in a forest district, this quantity will not support the complete lack of dead wood in a far away forest district (but adds to the average)
  • the fresh dead wood does not substitute the rotten, old dead wood

So the final important statement, which should be a motto of responsible foresters, is the following: a gentleman does not cut a hollow tree! (cover image by Rennet Stowe, wikipedia commons)

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