Before starting to harvest storm-damaged timber one should in a general way fix in which order in with which priorities the different tree species and forest stands will be treated. Thereby the aspects:
- "Absorbing capacity of the timber market"
- "Marketable assortments and timber utilization"
- "Forest protection"
have to be taken into account and weighted against each other.
The speed of the harvesting and processing plays an important role. Depending on the amount of damaged timber (volume and species) in the forest enterprise, the situation on the timber market, the own available labour capacity and the possibility to store timber, it is useful to stretch the harvesting of the timber.
Hereby, the actual situation of forest protection and its development has to be taken into account. In the following, the strategy of harvesting and processing of storm damaged timber after the storm event "Lothar" in December 1999 of the state forest service of Baden-Württemberg will be described as one possible approach:
|The damaged hardwood has to be harvested as fast as possible conserving the value of the timber.||>||Valuable timber of hardwoods is harvested before the timber of conifers.|
|Follow-up damages to standing forest stands by insects are minimised.||>||Storm broken trees are preferentially harvested. Scattered damaged trees are processed before large storm areas. Broken trees are preferably processed. Ongoing control of live-conserved forest stands for insect attacks. The harvesting strategy is adapted to the actual situation of forest protection.|
|A part of the coniferous timber from the state forest does not charge the timber market at peak times as it is withdrawn by conservation.||>||A large part of the conifers from the state forest is conserved by wet storage and only reaches the timber-market at a later point in time. Thereby the "non-state-forest" can sell its stemwood early.|
The following order has been fixed, whereas an adaptation to local conditions was necessary:
- Clear the necessary transport- and forest roads; ensure the access to the damaged areas and the hauling of the processed timber. It is recommended to firstly clear the roads to the required areas (if this is in line with the general traffic, e.g. for recreation, …) and – if possible - to process into marketable assortments. Overhasty cutting of trees into small logs to clear roads increases problems in marketing, storing and protecting timber against insects.
- Start with processing beech and valuable hardwoods – minimum quality class B and size L 3b (- mid diameter >35 cm) (3a >30cm) – at first on large areas until 4 months after the event (in case of a winterstorm), after that also scattered trees should be harvested until 8 months after the event. The reason therefore is to avoid a fast devaluation of the valuable hardwood timber. Moreover, the cost-intensive processing of small and low-valued hardwood should be avoided for economic reasons, resp. to be restricted to unavoidable cases.
- Processing of "damage-nests", especially with broken trees of spruce and pine (motor manual), remove stumps, process as long poles. The most important point here is to avoid bark beetles, as broken trees will be attacked the fastest by bark-breeding beetles (e.g. Ips typographus). Especially storm damage-nests and concentrated single damages are starting points for bark-beetle damages. This danger has to be minimised by completely removing the breeding-material from the beginning.
- Processing of large storm damaged areas of Norway spruce and pine with the help of contractors until 15 months after a winterstorm. Due to the large and nation-wide offer of harvesters and forwarders large storm-damaged areas could be processed at the same time as "damage-nests". If there is a lack of demand or no possibility of wet storage, processing should be postponed. Ideal for postponing are large damaged areas with a share of broken trees of less than 20%.
- Other conifers: The experiences from the storm in 1990 showed that bark beetles at silver fir are less aggressive. There also a minor forest protection problem with Douglas fir. Non-processed Douglas fir was estimated to be storable in situ until 2002 (24 months after the storm event).
- Valuable logs and stemwood of oak and poplar: Oak should only be processed on demand. Both tree species have been successfully stored unprocessed in situ until winter 2001/2002, or even spring 2002 (12-24 months after the storm event).
- Processing of small sized conifer logs (< 20 cm dbh) and industrial hardwood is of subordinate importance. No treatment of logging debris in the year 2000. According to the experiences of the year 1990 the risk of attacks by Pityogenes chalcographus can be controlled. No danger of bark-breeding bark-beetles is issued from broadleaves.
Experiences and evaluation concerning the order of processing
Experiences have shown that the order of processing storm damaged timber was right. The strategy "preferred and fast processing of valuable broadleaves until May 2000 (5 months after the event)" has proven to be successful. Despite the approaching end of the season for hardwoods and a relevant volume of oak-timber from France, an important volume of timber could be sold to acceptable timber prices.
The aspects "order of processing" and "speed of processing" have to be analysed in a more differentiated way. Although the given targets were not fundamentally put into question, reality increasingly deviated from the given strategies during the summer after the storm. The strategies can therefore only partly be looked upon successful.
- Many of large damaged areas have been processed mechanically. Due to the higher performance of the machines these large areas were often faster processed as the small areas , which was not according to the strategy. Some of the contractors tried to implement themselves on the attractive large areas instead of working on small areas using extortionary methods.
- In order to quickly fill the wet storage places, the early use of harvesters on large areas was necessary.
- The expectations of private and community forest owners had a certain influence on the decision not to decrease the speed of processing.
- The mental and emotional load on the collaborators lead to the desire to clean up the damage as fast as possible.
- A lack of discipline and solidarity of some employees of the forest service and some forest owners lead to a competition for resources and sales-contracts. Consequently, the speed of processing increased continuously in the first months after the storm.
Subordinate processing of small-sized conifers:
- Against previous expectations, the years after the storm have shown that the damage caused by Pityogenes chalcographus can endanger whole forest stands. These has to be taken into account when designing future strategies.
Results of the high speed of processing:
- In some forest districts, it was not possible to transport the logs out of the forest due to a shortage in hauling capacity. Possibilities to store the logs along the roads were soon exhausted. Due to the long storage times along forest roads the situation of forest protection was deteriorated and the quality of the logs decreased. If the situation of forest protection and labour organisation allows for, in situ conservation (live storage) should be preferred to processing and consecutive storage of timber along the roads.
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