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Pro Silva conference and visit to Croatia

PRO SILVA CONFERENCE AND VISIT TO CROATIA
1-4 June 2005
Mike Seville and Rik Pakenham

Mike Seville is the Chairman and Rik Pakenham a committee member of the Continuous Cover Forestry Group, which is affiliated to Pro Silva in Europe. This is a federation of foresters who advocate forest management based on natural processes.

Woodland Heritage kindly sponsored them to attend this annual conference and study tour, which is held in a different member country each year.

Croatia used to be part of Yugoslavia but is now a Republic with a population of approximately 4.5 million people and an area of 5,654,200 hectares.

Forestry has a long history, within the statutes of many Dalmatian towns are regulations on the preservation and conservation of forests as early as the 13th century. The first forestry offices were established in 1765 with the first manual on forest management, the Forest Order issued by Maria Theresa in 1769.

Forests comprise 44% of the total area, of which 82% are state owned and 18% privately. Composition by tree species is 84% deciduous and 16% coniferous. The main species are Beech 35%, Pedunculate Oak 14%, Silver Fir 10%, Sessile Oak 10%, Hornbeam 8%, Ash 4%, Norway Spruce 2%, other broadleaves 13%, other conifers 6%.

Forest communities are divided into two vegetation regions, the Mediterranean and the Euro-Siberian- North American, within which there are respectively two and five vertical vegetation belts. The country is very rich in species diversity having 4,500 plant species, half of which live in the forests. 260 are woody species, 60 of which have commercial value. Annual increment is 9.6 million m³ and the annual cut is 5.3 million m³, 46% of which is sawmill timber, 37% fuelwood and 17% waste.

Forest education began in 1860 and is now based in the Faculty of Forestry and the Academy of Forest Sciences at the University of Zagreb, and the Forestry Institute at Jastrebarsko. The Faculty owns five teaching-experimental centres and 3.5 million hectares of forests. Approximately 100 students graduate each year.

It was one of these teaching centres we visited on our first day.

2nd June 2005

Excursion 1: Natural regeneration of Silver Fir stands using group selection system at the Forest research and educational centre of Zalesina.

The forest is situated 130 km west of Zagreb and 50 km east of the Adriatic sea in a mountainous area between the south eastern Alps and the Dinaric mountain chain.

We visited the Belevine management unit which covers 294 ha between 720-870 m elevation. The soils are podzols over lying schists and sandstones. Air temperatures range from -3° to + 16° C, precipitation averages 2500 mm and snow lies for approximately 180 days.

Historically this was a virgin Beech forest with very few conifers. Exploitation began at the end of the 16th century, but increased towards the end of the 18th century when roads and railways were built. From 1871 the forest was owned by German families and from this time the concept of creating pure conifer stands was put into practice.

Records show that the Beech content in 1867 was 67%. By 1950 it was only 3%. Much of the Beech was exported to Venice for the Murano glass works. The current structure originated from natural regeneration under a selection system, the main species being Beech, Silver Fir, Norway Spruce (not native), Rowan, Sycamore, Lime and Elm.

For the last 50 years the forest has been managed by the Faculty of Forestry under set management guidelines which aim to have an optimal volume of 440m³/ha, a basal area of between 34-37 m², selection cutting interventions every 10 years removing 25% of the volume – aiming to form mixed stands of 80% Fir 20% Beech.

Target diameters for cutting are Fir 70cm dbh and Beech 50cm dbh. Single tree and Group selection systems are used.

All species regenerate freely except Norway Spruce which has been used as a pioneer on fire, wind blow, or on die-back areas caused by pollution.

The maximum gaps created by felling are 1.5 times the height of the neighbouring trees, generally 30-50 metres.

The students study for a four year degree and are tutored in all aspects of forest management including six months practical work in the forests. At the time of our visit they had felled Silver Fir, delimbed, measured over bark, peeled the tree, measured under bark, cross cut and were waiting to extract the timber.

Excursion 2: Natural regeneration of Fir-Beech stands using the Single Tree Selection system.

This forest was situated in the Dinaric mountains growing on steep slopes with many limestone outcrops. Similar to the lunch-time stop, the best trees were growing in the deeper soils between the rocks, but trees were also on the shallower soils over the Limestone and this created a large range of heights.

These features led to the choice of using a Single Tree Selection system to enhance stability and retain canopy cover.

The main species were Silver Fir, Norway Spruce and Beech with Sycamore and Elm.

Experimental plots showed 931 trees/ha with diameter range of 1-110cm dbh, basal area of 41m², standing volume of 601 m³/ha and annual increment of 7.1m³/ha.

The diameter distribution was <30cm 15%, 31-50cm 15%, >51cm 70%.

Cutting interventions were every ten years removing 20–25 % of the volume, which approximated the increment over that period.

Although the terrain made felling and extraction difficult the following average expenditure and income was achievable:

Price roadside €48/m³, fell and extract €7, tending €9, administration €10, return €22/m³.

This was a beautiful forest exhibiting the best that Selection systems can offer.

3rd June 2005

Having spent the night in Delnice in the west near the Slovenian border we travelled east, almost to the Hungarian border to the Bjelovar forest district.

On this side of the country the climate was very different, with hot summers and cold winters. The average temperatures were 10-12º C, with precipitation being 850mm per annum. The landscape was flat, or rolling hills with wide flood plain valleys

Excursion 3: Natural regeneration of Beech-Sessile Oak forests by Shelterwood cutting. This forest was situated in the Bilogora Hills at 150 metres altitude. It was predominantly Beech with Oak, both Robur and Petrea and a small percentage of Cherry, Lime and Hornbeam.

The system regenerated the forest over 10-12 years with three thinnings and a final clear cut over this period. The aim was to establish a predominantly Beech/Oak forest with other minor species.

Beech produced viable seed every year and Oak every 3-4 years. The regeneration area was 34 ha which had been fenced to exclude Wild Boar. Boar numbers are increasing since the end of the recent war as people no longer need to kill them to survive. Local hunting clubs now carry out the control.

The standing volume at the beginning of the regeneration period was 520m³/ha, Beech are managed on 100-110 year rotations before Red Heart attacks the tree.

The average prices received roadside were Beech €50 and Oak €100 per m³, Oak veneer could fetch up three times this price. The timber is sold to a traditional set of complicated rules, but was of high quality.

The outcome of this management system could be seen in the adjoining compartment where 60 ha of 20 year-old, even-aged forest stood at up to 10,000 trees/ha.

This view came as rather a shock compared with what we had seen the day before, and no explanation, apart from tradition, was offered for not considering adopting selection systems to develop an uneven-aged structure.

Excursion 4:The management of Beech-Lime stands.

A 51 year old stand that totalled 50 ha, with 50% Lime (argentea), 18% Beech, 18% Hornbeam 14% other species including Wild Cherry. The standing volume was 295 m³/ha with an average top height 28 metres and yield of 11m³/ha per annum. Lime only grows in this part of Croatia between 200-400 metre contours.

The Lime is worth more than the Beech in monetary terms and is used for internal panelling, veneer and plank. However it is a pioneer species, does not grow under other Lime and is very aggressive both from suckers and seed. The site type is Beech/Oak and it is envisaged that this will dominate in the next generation.

Excursion 5: Flood plain forest stand of Black Alder.

The next stop was within the river Drava flood plain almost adjacent to the Hungarian border. Here we were in the Black Alder/Oak forest area that totalled 5,000 ha, of which 2,000 ha were Black Alder. We visited a stand of Black Alder that was 96 years old, an average height of 37 metres, a mean dbh of 37 cm and a standing volume of 750m³/ha, other minor species were Field Maple, Hornbeam and Bird Cherry. It formed part of a forest reserve and had been protected since 1975. It survived in an almost natural state because of the water regime, where the constant water table level was 1 metre below the surface, but spring and autumn floods were essential to retain this regime. This was one of the few areas within in the Danube water-shed that had not been affected by the damming of the water courses, and this gave rise to a Gley type soil with sand.

To see 750 m³/ha of this species was almost unique and well worth the visit despite the Black Fly and Midges !

4th June 2005

The last day was spent in the Lowland and Floodplain forests of Croatia between the rivers Sava and Drava. These forests cover 290,000 hectares of which 205,000 hectares are pedunculate oak, 27,000 hectares of narrow leaved ash, 17,000 hectares of black alder as well as white willow, poplars and other mixed softwoods and hardwoods. The total growing stock is 72,900,000m³, the annual increment 2,076,000m³ and the annual cut 1,280,000m³ or 61% of the increment.

The forests fall in to four main stand types:

  • Oak and hornbeam
  • Floodplain oak
  • Oak and narrow-leaved ash
  • Oak and alder

Excursion 6: Climax Oak and Hornbeam forest

The first stand we visited was an area of magnificent 175 year old oak and hornbeam with 450m³/ha of oak and 178m³/ha of hornbeam. This was climax forest on an area which did not flood and where the water table was typically between -1m and -7m below ground level with the oak having an annual increment of 6.37m³/ha and the hornbeam 3.96m³/ha.

Again this woodland was being regenerated naturally by a shelterwood system though, where previously the method would have been to clear all the undergrowth and wait either 5 or 15 years and then fell all the oak, now the crop was removed in 3 cuts over a 6-8 year period, as they were finding that the young oaks could only live under the canopy for a maximum of four years due to problems with mildew, mice and wild boar.

Excursion 7: Floodplain Oak and Ash, Oak and Alder forest

Although at the same altitude, 93m, the ground conditions at this site were very different from the previous one and the area was characterised by small scale, but distinct changes in vegetation type caused by very small differences in height relative to the water table. At the first stop the soil was heavy clay and the area flooded twice a year. It had been an oak elm mixture, but the elm had been lost and was now being replaced by ash. Although slightly younger than at the previous site, the oak was of a significantly smaller diameter being slower grown. This made it at least 20% more valuable at €360/m³ as opposed to €260/m³ for the wider ring width oak.

Possibly because of the soil conditions the oak here does not fruit, so regeneration was by seeding of oak at a rate of 800kg – 1 ton of acorns per hectare.

Within feet of this site, the land was constantly flooded and the crop changed to alder swamp.

We then walked on to a recently regenerated area. This 9 hectare site had received a sanitation felling in 1998 which had opened up the canopy sufficiently to allow seeding and regeneration. In 2001 40% of the overstorey, 500m³/ha, had been removed and in 2004 the remaining trees had also been felled. Although the crop was now well established there had been significant tending costs: 31 man days for fencing, 137 man days for weeding and unspecified costs for two mildew treatments.

Whilst there was no doubt that the shelterwood systems used by the Croatians were working and producing good quality timber, there was much discussion within the group as to why a more intimate selection system which had the potential to save on costs and prevent the felling of trees before their optimum size and value, had not been adopted. Again this appeared to be a combination of tradition and a lack of will to experiment and change perhaps as a legacy of the communist era.

Something different

In the afternoon of the last day we left the forest behind for a surprise visit to the Lonjsko polje nature park. This fascinating village of sawn oak houses and adjacent wetland was a step back in time and it was heartening to see that the Croatians had recognised its importance and were taking steps to safeguard it.

The reserve is an important breeding ground for storks, spoonbills and other wetland birds and is notable for the semi-feral wild pigs historically kept by the villagers and currently being re-introduced.

More information is available at the reserve website www.pp-lonjsko-polje.hr

Conclusion

Whether or not you agree with the management systems adopted by the Croatians, there is no doubt that they value their forests and manage them to a high standard.

Their forests and foresters are held in high regard and contrary to some opinion, they are not cutting more than their increment for quick Western currency. Indeed, if they have a problem it is that they are not cutting enough timber to sustain the regeneration of their forests.

The more one travels in Europe the more one realises we have a great deal to learn from European foresters with their long history of forest management and how the love of trees and forests can bring people together to share their knowledge.

Mike Seville and Rik Pakenham

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