Unlike other European countries that experience major forest damage due to climate change and related disease and insect pest attacks, Slovenia’s foresters have a number of advantages in protecting their forests, which cover almost 60% of the country’s land area.
Although Norway spruce covers one-third of Slovenia’s forests, the country has a greater tree species mix than many other European countries, which helps reduce the risk of widespread damage from disease, insects, heavy sleet, fire and wind. In addition, Slovenia is recognised as the leader in close-to-nature forestry (CNF) or what we in Ireland refer to as continuous-cover forestry (CCF).
“In 1949, there was a prohibition of the clear-cut system and there were regular inventories and obligatory plans for all forests – state and private – in Slovenia,” explains our guide professors Janez Pirnat of the University of Ljubljana.
“The general aim of this approach is to achieve ecological, economic and social sustainability,” he adds in his introductory talk to Society of Irish Foresters members during their recent study tour of Slovenia’s forests.
“Tree tending is done mostly by retaining an appropriate canopy cover while harvesting of adult trees is the most important instrument of forest tending.”
CNF has a “planned non-intervention” approach “which allows a network of old growth forests, forest reserves, eco-cells, islands of ancient trees and dead wood and protection forests to develop side by side with production forests”.
Prepared
As a result of CNF, Slovenia’s forests are better prepared to deal with climate change threats than some of their neighbouring countries that are experiencing forest fires, drought and the devastating damage caused by the eight-toothed spruce bark beetle (Ips typographus).
Native tree composition including retention of special habitats and the creation of uneven-aged forest by natural regeneration is the basis of CNF.
Unlike Ireland, which has a limited native tree species resource, Slovenia has a wide range of indigenous species. CNF ensures that this mix is retained and even enhanced apart from Norway spruce, which will be reduced over time to 8% of forest cover.
This species is close to the end of its natural range in Slovenia and prof Pirnat believes it is better suited to higher elevations rather than lower slopes and valleys.
The Pahernik Foundation was established by Vida Ribnikar in 2005 after she inherited the family forest located in the Pohorje region in Northern Slovenia. The Paherniks managed the forest since the 19th century, but it was Vida’s father Franjo Pahernik who is acknowledged as a pioneer in applying CNF principles when he took over the forest from his father in 1903.
He lost the family forest on two occasion: first during the German occupation in World War II and later to the Communist regime when Slovenia was annexed into former Yugoslavia. Pahernik worked as a forester but didn’t live to see the family recover the forest in 1999, eight years after independence.
Scholarships
The Foundation is responsible not only for the organisation and management of the 570ha forest, but also provides scholarships for forestry students of Ljubljana University and commissions a range of research projects.
The Pahernik CNF silvicultural approach optimises multipurpose economic, ecological, social and productive goals. The forest achieves an annual economic surplus of €190/ha.
Although the forest extends from 370m to over 1,500m altitude, the average annual increment is 10.8m3/ha from which the Foundation harvests 8m3/ha from the conifer dominant forest.
This is impressive as the terrain is difficult with slopes often greater than 30 degrees. The soils are productive acid brown earths, capable of carrying an average stocking of 450m3/ha.
The main species are Norway spruce (67%), beech (16%), and European silver fir (12%), while the remainder is divided between with conifers (3%) and broadleaves (2%).
As elsewhere in Slovenia there is a gradual transformation of pure monocultures to mixed species stands with a shift towards broadleaves.
However, Norway is the mainstay in the Pahernik production forest. Pride of place goes to its 50m tall Norway spruce, which is the tallest tree in Slovenia.
Impressive as it is, the 250-year-old Pahernik Norway spruce is well short of the Glendalough 61m Sitka spruce which still has to celebrate its 100th birthday.
Climate change and forest protection are interrelated in Slovenia as they are throughout Europe. While average annual rainfall remains consistent, extreme rainfall and weather conditions are now more common.
Likewise, drought periods are longer. During our short stay in Slovenia, we experienced some of these extremes.
When we arrived in Ljubljana, we were greeted by blue skies and a temperature of 25°C but within 24 hours torrential rain swept across Slovenia as it did in most of central Europe with over 200mm falling in 48 hours. By the time we reached the modest altitude – by Slovenian standards – of 1,100m in the Pohorje region, it was snowing, almost three months ahead of schedule.
Slovenia’s approach to mixed species, close to nature forestry helps to reduce the risk of widespread damage to their forests but although not immediately visible, their spruce forests haven’t escaped bark beetle damage.
Their foresters are extremely vigilant in clearing damaged forests while regular inspections of 40 pheromone traps per 2,000ha are carried out to monitor both Ips and the six-toothed spruce bark beetle (Pityogenes chalcographus), which is also a major threat.
But the Slovenians adopt a positive attitude towards forest protection. Many will remember European silver fir dying in the 1970s and 80s here and throughout Central Europe. This species is sensitive to pollution in the atmosphere especially sulphur dioxide emissions. Since this industrial pollution has decreased, silver fir has recovered extremely well as evidenced in Slovenia.
The eight-toothed and six-toothed beetles threaten Slovenia’s forests but not as prevalent as elsewhere in Central Europe.
In short