0489-B1
Athanasios Hatzistathis[1] and Theocharis Hatzistathis
This paper gives a short description of the problem of soil conservation in the light of forestry practices in Greece, from ancient to modern times.
Special attention is given to human activity in the region, the development of civilizations and their effect on the degradation of ecosystems and the intense soil erosion. The factors that have contributed to the degradation of forest ecosystems and the desertification of about 30% of the country are also described.
Finally, the most severe problems of the Greek forestry sector are pointed out, and an effort is made to confront them on the basis of sustainable development in the light of the modern forest ecology. Reforestation efforts aiming to protect and improve the soils are briefly described, together with the methods being used to convert the country’s coppice forests into high forests (which make up half of the national forests), and the management methods used in the high forests, which aim to conserve the ecosystems and the soil, and to promote sustainable development of the mountainous regions. Finally the problem of preventing wildfires is briefly described.
Greece is a small country extended in the southern part of Balkan Peninsula with a complex relief. From its three sides is surrounded of the sea while to N. it borders with the mountain volume of the Balkans. Its major development from N. to S. at a distance of 792 km, has a severe effect on the formation of its ecological environment. From the total of its surface, about 75% is characterized by upland relief and only 25% is characterized as lowland surface suitable for agricultural use.
The latitude of the country, the intense fluctuations of the relief with an altitudinal width from 0-2917 m, as well as the sea which surrounds it, create a great variety of climatic variations.
The Greek climate in general, shows features of the mediterranean type: rains in winter, spring and autumn, and drought with high temperatures in summer. Up in the north and the inland of the country dominates the transitional towards continental type of climate.
The changes of the most significant meteorological parameters are as follows: in respect to the temperature, the annual thermometrical width ranges from 13 0C for the islands up to 23 0C for the north and continental parts of the country.
The relative air humidity ranges from 60-70%; the annual height of rain ranges from 400 up to 2000 mm at the highlands.
The variety of rocks from the various geological formations, which contribute to the composition of Greek space, and the many disturbances and movements which acted upon the geostratums, make the geological structure of Greece much more complicated.
The result of the above variety of the relief, climate and rocks is the development of a great diversity of forest vegetation which is richer in plant species from the floras of countries with bigger land size.
More specifically, in our country the following zones of forest vegetation are shaped, being distinguished floristically, ecologically, physiognomically and historically:
1. Eumediterranean vegetation zone Quercion ilicis.
2. Submediterranean vegetation zone or zone of Quercetalia pubescentis.
3. Zone of Fagus - Abies forests and mountainous submediterranean conifers.
4. Zone of boreal conifers.
Based on the above description of the area and on the presence but also man’s activity, from the historical years, the degradation of the natural environment is becoming comprehensive in the broader area of the Mediterranean. The deforestation in Greece but also in the wider region of the Mediterranean has been established as a classical example of the man’s adverse effect on its environment. Despite the hard-working efforts that were made to reverse the current and rehabilitate the ecosystems which had been intensely degraded, today we can say that there is no other region on the planet that shows so obviously the adverse effect of man upon the natural environment. It maybe claimed that the destruction of the natural environment in the Mediterranean area is the price paid for the development of the western civilization (Thirgood 1981).
The result of destruction of our forests is the intense erosion of Greek soils. It has been estimated that about 750 m3/Km2/year, of sediments are produced in Greece. This means that in the entire mountainous Greek area are almost produced 86.000.000 m3/year sediments, which along with rain waters, are driven into the lowland or the sea. By this erosion process it is estimated that nearly 30% of country’s land is one step before the desertification.
The destruction of the forest vegetation is the most harmful manmade factor which leads to the desertification. The destruction of forest vegetation is implemented by:
The clearcuttings of forest lands
The successive forest fires
The overgrazing of inclined lands
The unruled building construction and the tourist development, and of course the irrational management of forest ecosystems.
The above climatic conditions, that is low height of rainfalls, seasonal drought, very big fluctuation of rainfalls, climatic periodicities, short-range and big-impetus rains, in conjunction to the intense relief, the poor rocky soils, the intense degradation of the forest vegetation, the very long period of intense economical and social activity, the frequent periods of political instability and the long-lasting occupations by foreign forces have contributed particularly to the degradation of forests and the natural environment in general.
In view of the current condition of the Greek forests and the relative knowledge acquired recently in the light of the Forest Ecology, aiming at intercepting the rate of degradation in our country and reversing it, we apply a conservative policy to whatever concerns the management of our forests with an objective purpose the restoration of forest ecosystems wherever possible.
The World Conservation Strategy Document (IUCN, 1980), agrees that if development is to be sustainable particular care should be taken.
Generally speaking, human population growth and the level economic consumption per capita are critical factors affecting the possibility of sustainable development. However, they are not the only major influences. Technological change and policies for environmental improvement also have a role in determining the prospects for sustainable development. These along with the maintenance of genetic diversity and sustainable levels of utilization of species and ecosystems, have an important role to play in maintaining human welfare.
The following are the most important problems which Greek Forestry is facing up today in order to align with a sustainable management of forest ecosystems within the frames of a sustainable economic development. These are the reforestation of denuded areas, the conversion of coppices into high forest, the sustainable management of the high forests, and the wildfires as well
The most serious problem of the Greek forestry is the rehabilitation of severely degraded forestry land. The effort of reforestation in such areas has started before the Second World War. The bodies that have taken over this task in the above period were some communities, associations or government bodies aiming mainly at aesthetic and protection purposes.
However, the reforestations for wood production purposes, in our country, have started from the decade of 50’s. This period of reforestations is characterized by two significant events: a) the import and cultivation of poplar trees (various clones of euroamerican poplar tree and b) the mechanization of reforestation projects, a fact which has raised the rates of survival of plantings in high levels (80-90%).
The forestry species being used for the reforestation of degraded forest lands are mainly indigenous, frugal, and drought-resistant conifers principally species. These species, depending on the vegetation zone, are classified proportionally as follows: P. nigra 40%, P. maritime 20%, P. silvestris 10%, P. brutia 8%, P. halepensis 5%, Abies borisii Regis 5%, and another 12% consists of Populus euroamericana and some other broadleaves, especially deep-rooting evergreen shrubs.
As a reforestation planting method we use containerized plantings after soil preparation. Direct seeding in forest land seems to have poor results because of the bad quality of sites. Special cultural treatments are applied on the planting material in order to prepare plants before their final planting in the reforestation site (i.d. hardening) (Hatzistathis et al. 1999)..
As concerns the planting spacing, we usually use normal spacing; in the past we used to apply more dense spacings because the purpose was clearly protectional and the crown density was achieved quicker.
As is already known the coppicing system has many and serious disadvantages which make the continuation of this system unscientific and with many problems. These disadvantages may be summarized as follows:
The produced wood is of small dimensions and is mainly used for fuelwood
In short time intervals the biotic ecosystem balance is severely disturbed
In short time intervals the soil is severely exposed to erosion and degradation due to the applied clear-cutting fellings
The beneficial effects of coppice forests for the public are much smaller than those arising from high forests
The substitution or completion of stumps which are ageing or dried up by the time, especially after successive cuttings, is harder and more costly
The coppices were a need in past times but today for many countries and for our country as well have been abandoned since the wood is rarely used as fuelwood material.
For all the above reasons the conversion of forests into high ones is necessary. Particularly for our country, the conversion of forests is of great importance because these forests represent about the half of the forested land on one hand and on the other for the improvement of the natural environment through the restoration of the forest ecosystems.
The conversion of coppice forests in our country has started little by little before the Second World War but mostly by the indirect method. This method consists in the successive retaining of a number of standard trees individually or in groups, for more rotations. The stands arising by this method have a structure similar to the middle forest, with a multi-story structure.
The direct conversion with natural regeneration has started being applied during the last 40 years. This method implies the extension of rotation time and the suitable silvicultural treatment of entire stands as they were high even-aged forests, leading to a single-story structure of stands.
In this case, the purpose of silvicultural treatment is not only the preparation of soil and trees for the natural regeneration with seeds, but mainly the exploitation of the productive capability of the stand to produce technical wood. For this reason the method is applied in stands consisting of species capable of producing valuable wood such as oak and beech, and in which we meet a fairly large number of standard trees of best quality, regularly distributed throughout the surface of the stand showing a good vitality and a satisfactory growth. More specifically, the method is applied on the coppicing forests of deciduous oak and beech trees in best sites only (I, II, III site quality) and in stands with at least 100-150 trees of good form per hectare (Dafis, 1966, 1989, Dafis and Hatzistathis 1984).
The biggest advantage of this method is that we can put “under conversion” on the same time very big areas without a direct economic loss whereas we can concurrently make profit of the productive capacity of stands. The indirect economic loss resulting from the reduction of the harvested wood rate is offset by the gradual quality improvement of the growing stock, the growth of the ecosystem’s stability, the aesthetic improvement of the landscape and the obtaining of cut from the thinnings.
For our country, a basic purpose of forestry today is the creation of ecologically healthy forests with a desirable structure, being capable for a perpetual production of the maximum possible quantity and best wood quality of various categories in conjunction to a very high public-beneficial effect.
Under this concept, the conversion of coppice forests into high ones consists the best protection mean of the forest ecosystems and a highly scientific target for the global economy and for the global ecosystem as well.
The trees in stands are grown in close neighbouring-social interrelations among each other. These trees are cut down only in specific time period when all of them or part of them obtain the required consumption properties and dimensions.
For the maintainance and exploitation of the stand growing stock two different ways may be followed.
According to the first way, there may be pursued the stabilization of the forest’s structure and growing stock with a theoretically annual but practically periodical cut of the growing stock’s increment. This is attained by the cutting of a specific number of trees which are systematically selected.
Such a process is the one which is applied in the selective and group-selective system of the sophisticated Swiss form.
In this case the measures which are taken for the improvement of the growing stock are closely connected with the formation of the forest structure particularly by favouring the regeneration, irregularly in the selective forest, or with some order in space and time in the patches, in the group-selective forest.
The selection forest contains all the development stages of trees under well-developed canopies. Due to such a natural structure, a selection forest covers an area with trees of all ages, ranging from seedlings to mature trees. Both, the group selection mixture and the single tree mixture are equally ecologically effective.
The selection forest of beech and fir, influences considerably the stability of the landscape. The beneficial influence of selection forests is specific because it lasts throughout the year.
Finally, according to Prpiæ (2001), the selection forests as an infrastructural system, is an efficient factor for ensuring over the longterm natural vital conditions, air, climate, soil, and draining water. At the same time it protects nature, supported by right silvicultural procedures, that is by maintaining sustainability through the self-regeneration of forest ecosystems and by conserving the biological diversity of the natural forests composition.
By the diametrically opposite way according to which as a unit of silvicultural plan is considered the entire stand, the shortening of rotation is pursued with pure economic principles, leading to clear cuttings.
Overlooking any advantages or disadvantages arising from these two adverse systems, and irrespective from the way which someone would follow up to achieve the silvicultural purpose, the following basic principles should everywhere and always be taken into consideration, and kept for the best protection of the forest ecosystems:
1. The conservation of the forest as a forest ecosysem which means that the regeneration of the forest is a fundamental principle of the silvicultural treatment and this must be certainly continuous.
2. The maintenance and the best possible improvement of the site’s productivity. Keeping this principle in action it is necessary to choose the best suitable forest species, to form the appropriate structure of stands and take good care of the soil.
3. The pursuit of the maximum possible perpetual production in value and public-benefit effects (principle of sustainability). The strict maintainance of the above two principles and mainly the protection and improvement of the soil (Zagas and Hatzistathis 1995).
Today, in the light of facts of the ecology science, is unthinkable to conduct clearcuttings particularly in short intervals. Given that forest ecosystems are complex systems consisting of a large number of plant associations and animal associations, which “are literally built step by step”, and that this complexity and biodiversity is increased by the time, their destruction in regular time spans is anti-scientific (Hatzistathis, A. 2001).
The problem of facing up wildfires is primarily an issue of prevention and secondarily of suppression. The fire prevention at technical level has given satisfactory results in other Mediterranean countries. In our country, effective systems of prevention and control of wildfires were studied at research level. The prevention of forest fires is based on various actions, such as (Hatzistathis et al. 1996a, b):
The analysis of the ecological characteristics of the specific forest
The selection of the most suitable methods of forest treatment for reducing the risks and damages by the fires
The existing infrastructure of the under protection area
The organization of a network of rapid information and finally
Making people sensitive about the risks from wildfires.
European landscapes and forests have been influenced by man, and thus they have been changed significantly. However, forests are the most natural (semi-natural) element of present-day industrial landscapes, having locally the highest potential for maintaining and developing biological diversity, which in turn is essential for the preservation and conservation of nature.
It is our responsibility to create healthy and diverse forest for future generations, providing positive contribution to the global carbon and hydrological cycles, protection to soil and water resources, health and protection to the population and infrastructures against natural hazards, income and employment, particularly in rural areas and the excellence for recreational and cultural values for all people. To carry out the above objectives there is only one way; to follow up a “close to nature” silviculture which is based mainly on biological and secondly on socio-economic and technical criteria.
Dafis, S. 1966. Site and yield research in oak and chestnut coppices of NE Chalkidiki. Lab. of Silviculture and Mountainous Hydronomics. Aristotle Univ. of Thessaloniki, pp 120 (in greek).
Dafis, S. and A. Hatzistathis. 1984. Conversion of forests in Greece. Proc. of Balkan scientific conference on “Exploring, preserving and utilization of forest resources”. Sofia, June 18-23, 1984. Vol. III. 226-232.
Dafis, S. 1989. Applied Silviculture. Giahoudis-Giapoulis. Thessaloniki., pp. 258 (in greek).
Greek National Committee for Combating Desertification.The Greek national action plan against desertification.
Hatzistathis, A. et al. 1996a. Postfire vegetation dynamics in Sithonia (Chalkidiki, Greece). Proc. 2nd Balkan Conference “Conservation and Utilization of Forest Resources”. Sofia, Bulg. Vol. I.
Hatzistathis, A. et al. 1996b. Thinning treatment effects on stand structure and quality of Holm Oak coppices. Proc. 2nd Balkan Conference “Conservation and Utilization of Forest Resources”. Sofia, Bulg. Vol. I. Innovations. Athens, November 1999.
Hatzistathis, A. et al. 1999. Experimental work on reforestation techniques after wildfires in forest ecosystems in Chalkidiki. Proc. Intern. Symp. “Forest Fires: Needs and innovations. Athens.
Hatzistathis, A. 2001. Silviculture and environment protection. In Greek. Proc. Greek Forest Conference.
IUCN. 1980. World Conservation Strategy. IUCN. Gland, Switzerland.
Thirgood, I.V. 1981. Man and the Mediterranean forest. Academic Press.
Prpiæ, B.V. 2001. The selection forest as an infrastructural spatial category. In Silver Fir in Croatia by Slavco Matic.
Zagas, T. and A. Hatzistathis. 2000. Proceedings of the Congress NATURA 2000. “Application of Directive 92/43/EEC in Greece. WWF GREECE:109-118 (in greek).
| [1] Professor, Lab. of Silviculture,
School of Forestry & Natural Environment, Aristotle University of Thessaloniki,
Greece. Tel: +32310 998911; Fax: + 32310 998881; Email: [email protected] |