84 FOREST REPORT 2005
4.5 Dead wood
Dead wood is the basis for life of many animals, higher plants, fungi, lichens and algae.
More standing or lying dead wood can be found in Swiss forests than elsewhere in Europe, but this is still ten times less than in virgin forests.
Although the quantity of dead wood has increased in recent years, there are still, from an ecological point of view, far too few large stems of standing dead wood in the Central Plateau and Jura.
Habitat
Deadwood,according to experts, consists of trees, branches and roots that have died. They pro- vide thebasis forlife ofmany an- imals,fungi,higher plants,lichen and algae. Around 1300 species of beetle and over 2300 high- er fungi species cannot survive without deadwood.In the harsh climate ofmountain forests,dead woodmoreover formsan impor- tant seed bedfor the next gener- ation of trees.In totalabout one fifth ofall livingorganisms in the forest dependondeadwood.
An especially large number of species, including some of the most endangered in central Europe, live in decaying stems.
Large insects,like the verdigrised chafer (Protaetia aeruginosa) or the hermit beetle (Osmoderma eremita), reside in rotten stems and tree cavities. Today more than half of the beetle species that live indeadwood are threat- ened. Among them are well- known oneslike the rosalialong- icorn(Rosalia alpina))or the stag beetle(Lucanuscervus)).
In virgin forests the quan- tity of dead wood depends on the site characteristicsand how quickly the tree species decom- pose.Beech forests,for example, contain less fallen dead wood than beech-fir forests. Depend- ingon the forest community and thedevelopment phase,between 20and250m3ofdeadwoodper hectareaccumulate inEuropean virgin forestsandup to 400m3in thedecomposition phase of very old stands. In Switzerland the mean regional value ranges from 4 m3 per hectare in the middle of theCentralPlateauand34m3 per hectare in the north-eastern Alps.
How much dead wood is needed for endangered species to survive iscurrently the subject of research. The third Nation- al Forest Inventory (2004–2007) will yield valuabledataon thisas FURTHERINFORMATION
Swiss Federal Research Institute WSL, 8903 Birmensdorf
National Forest Inventory Research Dept. LANDSCAPE Section Landscape inventories (0) 44/ 739 23 43
Section Silvicultural strategies (0) 44/ 739 24 86
Ecole Polytechnique Fédérale de Lausanne EPFL
1015Lausanne ENAC Ecosystem Management (0) 21 /693 63 36
85 4BIOLOGICAL DIVERSITY
it is recording for the first time throughout the country the di- mensions and level of decay of dead and decayingwood.
Studies havealready shown, however, that the proportion of dead wood in Swiss forests is, froman ecologicalpoint of view, toolow.Astudy of the three-toed woodpeckercame to theconclu- sion that a minimum of 5% of standing stems must be dead wood toguarantee thebird’s sur- vival. The percentage today in
theAlps is,however,only 3.1%.
This example shows that,even in mountain forestswithquitealot ofdeadwood, there is stillan ec- ologicaldeficit.This is especially unfortunateas rottenwoodis of- ten the only place inmountain forests where spruce seedlings cangrow.
Development
The amount of dead wood has increased considerably since the mid ninetiesdue to storms, in- creased agingandlessuse.Today Switzerlandhas the highest pro- portion of dead wood per acre (12 m3 per hectare) in Europe.
Morewoodwill,in future,proba- bly beleft in the forest ascommer- cialuse isdeclining,particularly in the mountains. In the inten- sively usedforests in theCentral Plateauand theJura, the propor- tion of standingdeadwoodwith stemsmore than30cmindiam- eter is only 2m3per hectare.This is still too low from an ecologi- calpoint of view.Steps therefore need tobe taken inbroadleaf for- estsat loweraltitudes to increase the proportion ofdeadwood.
4.5.1
Volume of dead wood
Mean totalquantities of standing andlyingdead wood[m3/ha]
in the economic regions.
Switzerland:12.0
■up to5.0
■5.1–10.0
■10.1–15.0
■15.1–20.0
■over 20
4.9 5.6
6.5 3.9
6.8
9.4
15.0 16.9
18.2 33.8
14.7
11.6 23.3
14.7
4.5.2
Percentage area covered by dead wood
Development of theproportionof thebasal area of standing andlyingdead wood[%]
according todiameter at breast height (dbh).
Sanasilva Inventory in 4x4km grid Sanasilva Inventory in 16x16km grid
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03
■thin dead wood (< 30 cm dbh)
■thickdead wood (≥30 cm dbh)
How much dead wood is needed for en- dangered species to survive is currently the subject of research. Studies have already shown, however , that the propor- tion of dead wood in Swiss forests is, from an ecological point of view, too low.
8
4
0
8
4
0
Percentage Percentage
