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The annual cutting volume 2018 of Czech states forests Lesy ČR in the four most affected Moravian territories will exceed the ecological calculated cut five times. In the crisis territories the only thing that matters now is to provide shading to the clear-cut forest areas. Far too dry years and very high summer temperatures did not only bring spruce trees to their limits. In July alone, almost 700,000 sm³ beetle-infested wood accrued in the entire Lesy ČR - this is the highest volume of all times. Mid-August, the author had the opportunity to visit the most affected area of Northeast Moravia together with, amongst others, Tomáš Pospíšil, the temporary Lesy ČR managing director.
Sahelian zone in the middle of Moravia
The first location visited is part of the military state forests. They had to deal with 3 million sm³ of damaged wood in the past three years which equals the five- to six-fold annual cutting volume. Since 1994, the annual precipitation has been gradually diminishing from an average of 750 mm. A gloomy low was reached in 2014 with only 350 mm. This is less than in dry savannah Sahel (500 mm/yr). The current year shows similarly catastrophic developments. These long periods of drought are unprecedented, as our Czech hosts inform.
Next year: dead
At an altitude between 600 and 100 m, spruce has shown good growth in the past decades. "Now it is dying extensively in all age groups", Josef Svoboda, head of communication at Lesy ČR, laments. The spruce trees first suffer from drought damage but their needles - apart from a withered treetop - still remain green. In this state, however, the trees do not have enough vitality left to repel insects (primarily spruce bark-beetles, increasingly also northern bark beetles (Ips duplicatus)) or fungi (especially honey fungus (Armillaria)). "Trees that have yellowish treetops this summer will 100% be dead by next year", Pospíšil knows. "The point of no return will by then be passed already." Despite this knowledge, the wood remains in place because the calculated cutting volume is already used five-fold.
The very high summer temperatures and absent precipitation are also affecting larch, oak and beech trees.
Vital firs do not stand a chance against game animals
Pollen analysis from the 13th century show that 90% of the area was covered in firs. In the higher age groups, however, these only still exist occasionally. The high stock of game makes a natural rejuvenation of this still vital tree species impossible.
In the visited area of military forests, the percentage of spruce trees has decreased from 66% in 2003 to under 40% by now. Across many hectares, schematic reforestations are performed: one line of spruce trees, one line of oak trees. In the past, there were no oak trees above an altitude of 500 m; now, however, they are vital there. One year after planting the oak trees, not one is left that does not show browsing damage. In a fenced reference area, the consequences of too high a level of stock of game become apparent - this is where the young plants grow.
New regulations for more vitality
Different cultivation measures are performed in the Lesy ČR areas. The consequences of climate warming have been showing in the Lesy ČR for almost 15 years. These are their current insights:
· Utilization of pioneering tree species: Under the shield (of mostly pioneer tree species) the new forest is founded.
· Never rely on only one tree species. Founding is best in groups of several tree species.
· Structured forests are more stable than forests according to age groups.
· As little interference in juvenile woods as possible to maintain the stock-internal climate.
· Stock of game must be reduced, otherwise important tree species such as fir or oak trees do not stand a chance.
· Even "foreign" tree species such as the Sudetes larch must be used if they are vital in the stock.
· Permanent forests are the ideal state since they have a balanced stock-internal climate
· No clear-cutting
New silvicultural world
"The consequences of climate change move us to a new world in terms of forestry. Silvicultural recipes that used to work up until recently are now obsolete", Pospíšil explains realistically. What the damaged Lesy ČR areas are undergoing now is not always covered by Czech forestry law which, for instance, demands afforestation within two years. Currently, however, the foresters keep every surviving vital tree and wait for natural regeneration due to natural seeding. "We try to realize to structured vital stocks consisting of up to ten tree species", Pospíšil specifies.
Spruce - from optimum to dieback
On the visited Lesy ČR area, spruce trees are rejuvenating naturally. Svoboda reports on a spruce location that had been "extremely growth-prone" for the longest time - now, spruce has massive problems here. It is accompanied by very vital larch trees as well as birch, oak, mountain ash, aspen, alder, gray alder and hornbeam trees. "This results in a completely new mix of tree species. We are now planning on intervening about every six years - not in order to mark future crop trees but to remove sick trees", Svoboda explains.
Unusually vital fir
In matured forests that have fir trees, fir is usually still vital - despite the droughts. May, not only previous silvicultural regulations must be revised but also our knowledge on tree species.
Lesy Ceske Republiky
Forest area: 1.2 m. ha
Cutting volume: 7 m. sm³/yr
Growth: 9.7 m. sm³/yr
Causes for beetle calamities in Moravia
- Precipitation: dramatic decline in annual precipitation (from 700 to 350 mm/yr) with an unfavorable distribution over the year (i.e. dry summers)
- Temperature increase: with very hot summers
- Lack of understanding of the issues: Forestry-related reactions often too little and too late.
- Inappropriate choice of tree species: (too much spruce): significant deviation from natural forest ecosystem (sometimes 90% fir)