Report from Life Coastal Woodlands. Forest management methods in the coastal woodlands

Transcription

1 Report from Life Coastal Woodlands Forest management methods in the coastal woodlands Ida Wigrup, Swedish Forest Agency 2007

2 Content 1 Introduction 3 2 Regeneration cutting with nature conservation consideration Pine Spruce Broad leaved trees Mixed stands 6 3 Unconventional forest management methods Combined method Gradual regeneration Spruce under low shelter wood system Cuttings along the edges Gap regeneration Naturkultur Close-to-nature 8 4 Advisory service 8 5 References 8 2

3 1 Introduction Coastal woodlands possess a number of different values, ecological as well as cultural. It is important with both protection and active forest management to protect and develop these values. The owners and managers interest and knowledge about this special environment is essential if these values shall remain a component of the landscape. The archipelago is more forested today than in past times. The population was denser and the people living on the islands were depending on firewood for their living. Today the population is different, some people are still living in the archipelago, others have their holiday cottage there while others are visiting the archipelago as tourists. Foto: Henry Stare Many different values have to be considered in the management of the coastal woodlands. The islands are often small in the archipelago and the possibilities to manage the forests to gain an economical income are small. The nature values are often high in the coastal woodlands. The size of the cutting area shall therefore be limited and the adjustment according to the terrain should be done with care. On the small islands far from the mainland, it is often most wise to leave the forest without doing any cutting, but on islands closer to the mainland it is often possible to carry out some cutting. Coastal woodlands are rare and it is therefore of special importance to manage these forest the best possible way. It is not always suitable with big scale conventional forestry methods since it is a very vulnerable landscape. Many different aspects have to be considered and taken into account when deciding which methods to be used. This paper aims to give example of adjustment of common management methods and give examples of less widely used methods which can be applied in the coastal woodlands. 2 Regeneration cutting with nature conservation consideration By adjusting the current management practices it is possible to establish forestry practices that are well adjusted to the situation in the coastal woodlands. Some examples of adjustments are given below. 3

4 2.1 Pine Within the archipelago it is positive if the stands can offer a great range of possibilities so that the manager can chose between different management methods. A pine stand with a mix of broadleaved trees has therefore a number of advantages compared to pure spruce stands. Pine stands with elements of broad leaved trees Foto: Henry Stare The long life of the pines makes it possible to save some trees and let them grow into the new stand, an efficient method to create a more attractive view of the landscape and biological continuity. Pine stands will become relatively storm resistant by using appropriate management methods, early and small thinnings that will strengthen the root systems of the trees. This will create possibilities to leave shelter woods or seed trees when carrying out the final cutting. The main objectives of using shelter woods and seed trees in the archipelago are to : Make use of natural regeneration Use the seed trees as a complement to plantation Reduce the risk of stress due to dryness Increase the value of the remaining stems Increase the consideration for animal- and plant life Create a more attractive landscape view It is important to consider the risk of storm fellings before leaving shelter or seed trees. Topographic circumstances and previous management methods have to be assessed before choosing this method. The number of suitable shelter and/or seed trees has to be considered. The trees that shall be left is those with good height- and diameter growth and which has a good production of cones. The trees with wide crones should not be left due to the storm risk. 4

5 Broad leaved trees and small spruce trees should be left, particularly when the aim is to create a shelter wood system. It is essential to plan well in advance when leaving shelter- and seed trees. Approximately trees shall be left in a shelter wood system, depending on the fertility of the soil and the storm risk. Approximately trees should be left as seed trees when choosing that method, also depending on the soil fertility, storm risk and if complementary planting is planned. The site must be planted or sawn if the site index is not suitable for natural regeneration. Method of soil scarification, if it has to be done, should be carefully considered when planning the regeneration. In the archipelago it is often, of consideration to the ecological and cultural circumstances, appropriate to use a shallow soil scarification method which has a more limited affect on the soils than conventional soil scarification methods. 2.2 Spruce Pure spruce stand should be avoided in the coastal woodlands. A mix of pine and spruce with elements of broad leafed trees is to prefer. When regenerating the most fertile soils it is appropriate to mix spruce plants with pine and birch. On less fertile soils is pine with a mix of spruce to prefer. Suitable broad leaved trees should also be saved. Harvesting spruce Foto: Henry Stare It is not possible to adjust the cutting methods for spruce to the same extent as for pine. The management of spruce stands in the coastal woodlands are very similar as the management of spruce in the rest of the land. Pure spruce stands on islands and along costal zones are not possible to regenerate by shelter wood systems or seed trees due to sallow root systems which are making them sensitive to storm fellings. It is neither possible to extent the rotation time to great extent since that might cause risks for root rot. It is important to plan the edges of the felled area before the regeneration cutting is carried out in a spruce stand, this to minimise the storm damages, facilitate the regeneration and decrease negative impacts on the landscape view. Long and straight edges should be avoided. Cleaning 5

6 of the felled area from branches etc should be avoided or made to small extent. Smaller trees and bushes should be left to decrease the risk of stress from lack of water. 2.3 Broad leaved trees Broad leaved trees are improving the soils. They can be used as protection in beach zones and are giving a light and open landscape view. Continuity in this kind of stands is essential for many animal- and plant species. Many insects and birds are depending on old broad leaved trees. Pure broadleaved stands are not very common in the coastal wood lands. Broad leaved trees are suitable to use as shelter trees and it is therefore appropriate to save these trees when carrying out the early thinnings. Birch is the most common tree in the archipelago, with the exception of Bohuslän and Blekinge were noble trees are dominating. Cutting spruce and leaving birch trees Foto: Henry Stare 2.4 Mixed stands Creation or maintaining mixed stands in the coastal woodlands can result in a number of positive effects, economically as well as healthier stands. In the coastal woodlands is mainly pine mixed with broad leaved trees but also spruce can be suitable to mix. The most common is that birch is naturally regenerated in coniferous stands. This is a way to fill out gaps in the existing stand. The natural regeneration can in cases be so extensive that it is necessary to reduce the number of broad leaved trees. The impact of the birches is changing depending on the age of the stand. In younger stands can a share of 40% be appropriate to improve the quality of the pines. The high share will limit the growth in middle aged stands. The share of birch should be low at the end of the rotation. It is possible for a spruce stand to have higher share of birch than a pine stand. A share of % in average during the whole rotation does not decrease the growth. Aspen can also be a suitable tree species in spruce stands. The main value of having mixed stands in the coastal woodlands is not increased growth or quality but the attractive variation that it creates in the landscape, positive effects on the soils and the use as shelter trees. 6

7 3 Unconventional forest management methods 3.1 Combined method This method is aiming to result in a mixed stand with naturally regenerated pine and planted spruce with elements of broadleaved trees. The method can be suitable in some areas in the south of Sweden. Mainly pines are left as nurse trees. Birch and spruce can also complement the pines in the shelter wood system if there is a need. About 150 trees should be left as nurse trees. Soil scarification is needed and has to be adjusted to the soil type. It important to plan and carry out the soil scarification carefully since the soil in the costal woodlands is very vulnerable. The number of spruce seedlings is to be adjusted according to the fertility of the soil and the estimated extent of naturally regenerated pine. Experience has showed that it is often necessary to plant the same number as spruce as normally is done. The nurse trees are normally harvested in two steeps. It is of high importance to use gentle methods when harvesting the nurse trees since there is a risk to damage the regeneration. 3.2 Gradual regeneration This method is used for regeneration of spruce and is preferably used in damp/wet soils and peat lands were spruce is naturally regenerating in gaps. The method is suitable for swamp forests where it is important to keep the micro climate, not to risk frost since it can make the areas very hard to regenerate. Soil scarification is normally not carried out. The method should not be used at sites which are exposed to wind. The regeneration will take about years and the stand should be harvested gradually during 3-4 cuttings within this time. The harvesting should be adjusted so that the plants will get enough light at the same time as other vegetation should be held back. 3.3 Spruce under low shelter wood system The low shelter wood system is mostly used on damp areas. It can be used on plain areas were the risk for frost is high. It is common that mainly birch and aspen will create the shelter in these areas is. Spruce will gradually establish under the shelter. By cutting the shelter gradually the plants will get enough protection from frost and light. The growth of the spruce is kept back with this method which has a positive effect on the quality. The shelter of broadleaved trees makes it possible to create a mixed forest which can in an early stage produce both fuel wood and pulp wood. This system can produce valuable timber if the broadleaved trees are of good quality. 3.4 Cuttings along the edges This method is suitable to regenerate spruce m wide strips are cut with an interval of 5-10 years. It is essential to start in the northern part of the stand and put the strips in an easternwestern direction. This makes it possible for the spruce to naturally regenerate in the shade of the old stand. Simultaneously, the remaining stand should be thinned in the northern edge to start the regeneration phase in the next strip. The regeneration will take about years. The stand will be unevenly aged. Problems can occur with storm damages and insect damages at the edges. 7

8 3.5 Gap regeneration The gap regeneration method means that gaps with a diameter of 20 metres are cut with an interval of 5-10 years. The gaps are gradually expanded by 10 metres at a time to gradually grow together. The remaining stand is thinned in the edge to the gaps in connection to the harvesting operations. The total area will, with this method be regenerated within years. The new forest will have a spread in age classes. Problems can occur with storm damages and insect damages at the edges. 3.6 Naturkultur The idea behind this system is to cut the most valuable trees when they are mature. This will result in a forest with well spread age classes. The gaps that occur when the trees are removed are replanted without soil scarification or naturally regenerated. The method has mainly been used in trials and has not been used as management method to great extent. 3.7 Close-to-nature The prime idea behind this method is that the trees are cut when they have reached the most economically favourable age, free-standing or group wise. This will result in a stable micro climate, making it possible for the trees to naturally regenerate in the gaps. Complementary planting is done if it is needed. This will result in a stand with a wide diversity in age- and dimension classes. This kind of stand will become more storm resistant compared to stand managed by conventional methods. The method is in line with the idea behind PROSILVA, an European federation of foresters working towards forest management methods based on natural processes. Advisory service It is a good idea to contact the Swedish Forest Agency for discussions concerning the operations before carrying out any forestry operations in the forest. Also Forest owners associations, forest companies and local entrepreneurs process great experiences and can give good advices in the planning of forest operation in this special landscape. They can also assist in mediating contacts to timber buyers etc. 5 References Andersson E Alternative forest management regimes in Scandinavia a well needed complement? Examansarbete 73:2006. Department of forest products and markets and School for forest engineers. Kihlblom D Skärgårdsskog Ekologi och skötsel. Skogsstyrelsen, Jönköping. Larsen B J Naturnær skovdrift. Dansk skovforening, Köpenhamn. Länsstyrelsen i Östergötlands län och Skogsvårdsstyrelsen i Östergötlands län. Skogen i skärgården. Linköping. Moström J Skärgårdsmönster En historisk och geografisk studie av ägande, nyttjande och landskap i Kalmar läns urbergsskärgård 2004:1. Länsstyrelsen Kalmar län. 8

9 Skogsstyrelsen Grönare skog. Jönköping. Thor B Riktlinjer för hållbart skogsbruk i skogen vid kusten. Skogsstyrelsen, Jönköping. PROSILVA downloaded