Timber Storage – Life Conservation
Life conservation of individual trees or
whole stands is not a method of conservation in the strict sense of the term.
It is rather an instrument to preserve timber quality and coordinate salvage
logging operations over an extended period of time after calamities.
Life conservation provides the
possibility to differentiate between different levels of urgency of salvage
logging tasks. A priority list can be compiled. Loss of a certain degree of
timber quality is accepted in any case and is not avoidable. The method is not
applicable for perennial conservation.
Life conservation means that pushed or
thrown trees are left for a certain period of time in order to direct workforce
capacities to stands with higher salvage logging priority.
Temporarily delaying the cutting of such
trees can maintain the tree’s water balance and therefore keep it alive. Drying
out of the wood is slowed down, and the tree’s natural defences are used to
prevent, or at least delay, infestation with insects and fungi.
- Applicable directly without prior processing.
- No technical equipment is needed.
and easy to realise storage method enabling the forest company to use the
available workforce in damaged
- As the water supply is restricted, infestation with insects and fungi is
more likely than in trees with complete anchoring.
- Changes in moisture within the tree can not be influenced. Success of
the method depends on climatic conditions.
- Life conservation is temporary. It should not be applied for longer than
two years/vegetative periods, even for tree species rated “very good” in the
- Life conservation of spruce in particular depends on the forest
protection situation of the surrounding area. Continuous beetle monitoring is
therefore essential (see Fig. 1 below).
- The forest protection situation is less critical for forests with higher
proportions of fir and Douglas fir. In fir or Douglas fir stands, longer
storage periods are possible without a large reduction in quality and high risk
of beetle infestation. Still, two vegetative periods should not be exceeded.
- High monitoring input and experienced and cautious staff (forest guards)
are needed. Immediate action is needed if risks to forest protection arise.
- Anchorage of the root plate.
- Most important precondition:
sufficient contact between roots and soil. The root plate should only be lifted
slightly. At least 20% (preferably 30%) of the roots should still be anchored
in the ground. If the root plate stands vertically and only a few roots are
still connected to the ground life conservation will not be successful. The
trees die off in a short time.
- Storage location
- Preferably shady locations on
northern slopes. Individual thrown trees are advantageous. Spruce trees with
shallow root plates on sites with stagnant or alternating moisture levels, as
well as sites with high proportions of red rot infection, are unsuitable for
- State of the tree’s health
- The trees need to
have a green, intact crown and must not show any great bark damage. Only stands
and sites with low proportions of broken timber are suited for life
- Forest protection situation
- For successful life conservation,
of spruce in particular, the present bark beetle population (i.e. the
population which existed before the calamity) should be as small as possible.
- Monitoring and documentation of beetle infestation on storm damaged sites
- Checking storm damaged sites
regularly for beetle infestation and documentation of the findings is
fundamental for successful life conservation. Forest
companies have to be able to recognise increasing risks in the forest
protection situation at an early stage and react accordingly. Delegation of
this task to a specialised forest guard at the district level is highly
recommended and has proven to be very useful.
Life conservation or salvage logging?
Fig. 2: Decision guide and flowchart for life conservation (Illustration:
Research Institute Baden-Wuerttemberg, Department for Forest
Suitability of tree species
Individual tree species are suited for life conservation to varying degrees:
Storage period no longer than
12 (– 24) months
Very good - Good
12 (– 24) months
Good - Suitable
12 (-15) months (spruce: risk of blue
1 vegetative period/2 winters
Good - Suitable
12 months (risk of blue staining)
Good - Suitable
6 (- 12) months
N/a. Risk of blue staining.
Experience so far
Fig. 3: Although it is an eastern / north-eastern slope, there is a risk of drying-up.
- The study mentioned below shows that life conservation on moist sites
with good water supply produces better quality sawn timber than on dry sites.
However, after "Lothar" there were occasional good experiences on drier sites.
- Individual or scattered wind thrown trees on shady sites seem to be
better suited for life conservation than entirely thrown stands, but this could
not be proved unequivocally in the study mentioned below.
- Experiences hitherto show that stands on northern and northeastern
slopes are better suited for life conservation than southern, southwestern or
western slopes and plains. More recent experiences indicate that spruce trees,
which were thrown downwards on northern/eastern slopes, were at higher risk of
insect infestation and loss of timber quality. The reason for this phenomenon
seems to be drying out of the root plate, as the underside of the root plate is
exposed to strong solar radiation.
- Studies on life conservation after the storms “Vivian” and “Wiebke” in
1990 in Rheinland-Pfalz showed the suitability of different tree species
(Eisenbarth, 1995 and Bücking, Eisenbarth and Jochum, 1997).
- The results indicate that life conservation can be
recommended for spruce and pine thrown during winter for up to one year after
the storm event. According to the authors, preconditions are low proportion of
broken trees, normal to low bark beetle population and preferably a low
proportion of damaged bark (no extreme damage).
- Life conserved trees from moist sites with a good
water supply showed better sawn timber quality than trees from drier sites. The
outcome of the study did not clarify to which extent individual or groups of
thrown trees need to be processed prior to entirely thrown stands. In any case,
salvage logging operations should be completed before swarming of forest
insects in the second vegetative period after the storm.
- The study also included tests on life conservation of
Douglas fir, oak and beech. Due to differing basic conditions and a small
sample size, the results for Douglas fir are not conclusive, but experiences
are overall very positive. According to the study, even life storage durations
of 5 years did not have any negative effects on the quality of Douglas fir
roundwood and the sawn timber produced from these trees.
- Life conservation can also be applied to preserve
timber values of oak after calamities, as long as the duration does not exceed
one year. Compared to piled storage, life conservation clearly showed better
- Good suitability of beech trees for life conservation
was found where the trees were thrown during winter storms and were kept no
longer than the following vegetative period. Furthermore, the results showed
that the loss of quality is higher on openings than under shelter, where losses
were marginal during the first year.
- Eisenbarth, E. (1995): Schnittholzeigenschaften bei Lebendlagerung von
Rotbuche (Fagus sylvatica L.) aus Wintersturmwurf 1990 in Abhängigkeit
von Lagerart und Lagerdauer. Mitteilungen aus der Forstlichen
Versuchsanstalt Rheinland-Pfalz Nr. 33/95, 211 S.
Mahler, G.; Schröter, H.; Seemann, D.; Wurster, M. und Textor, B.
(2000): Lebendlagerung muss ein Teil der Strategie werden! AFZ - Der
Wald 9/2000 S. 452-453.
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