The borders of natural distribution of many trees and bushes species run across Poland . It is conducive to a high biological diversity, in particular species diversity. About 65 % of Polish flora or fauna species exist in forests or are connected with forest.
On the one hand, we observe the disappearing of certain species such as: great bustard ( Otis tarda ) or curlews ( Numenius sp .), but on the other hand some previously endangered species are becoming more common: European bison ( Bison bonasus ), wolf ( Canis lupus ), and beaver ( Castor fiber ). Among tree species, we observe the disappearing of yew ( Taxus baccata , and fir ( Abies alba ), as well as the expansion of hornbeam ( Carpinus betulus ) and lime ( Tilia sp. ).
Secondary or artificial plantations constitute the majority of our forests. They developed after cutting natural forests down and artificial regeneration by man. Traditional forestry simplified the structures and functions of managed forests by the unification of reproductive genetic material, elimination of undesirable populations, removal of dead wood, and numerous conventional actions in forest management. The single-functional forestry in the XIX century was based on the “normal forest” model. It was supposed to provide the constancy of utilisation. The even distribution of age classes in the whole forest complex was the desired structure of such forest. This structure was achieved by the clear felling of the oldest stands and the regeneration of young stands, while the area where it took place was still the same every year. In such a way, a schematism was introduced to forest ecosystems. It made forest management easier but destroyed the natural diversity of forest communities. Limiting the diversity of forest ecosystems, people, in the same time, limited or eliminated ecological processes such as: natural selection, ageing, competition, and succession. In simplified ecosystems, the biggest opportunities of development belong to the species which are marked by efficient expansion, high regeneration potential, fast growing and the lack of food specialization. However, they are not always the desired species in the ecosystem.
The modal of single-functional management was verified only in 1982-1986 by the ecological disasters: strong winds, heavy snow, gradation of insects, droughts, and the effects of industrial emissions.
An important threat to the genetic diversity of forests is, conducted for over 200 years, the man-made selection of forest trees species, which eliminates a part of genetic diversity of trees. It comprises support for certain species and their ecotypes as well as silvicultural and tending systems like selective thinning. There is also a problem of the naturalness of different tree species provenance. Seeds of different alien species were brought to Poland as early as in the XVII century. That is why, the “naturalness” of our forests and the “naturalness” of the distribution ranges is controversial. The knowledge of “naturalness” of different species is important when these species are introduced or reintroduced.
A bad forests condition in the 70s and 80s caused the changes in forest management. This started to bring forestry closer to nature. International actions, the new act about forests from 1992 and many regulations by the General Director of State Forests reinforced these tendencies.
The basis of “ecological” forestry is the compatibility of species composition with site, or biocenosis with biotope. The forestry actions conducted in order to protect and enrich biological diversity are: rebuilding of stands, introduction of undergrowth, fitomeliorations, enriching organic material in soil, works on sites, plotting of sites and others.
In last decade, genetic diversity of forests came into focus. Forest Gene Bank Kostrzyca in Kostrzyca is of special interest as there are gene resources of over 20 trees, bushes, and undergrowth plants species from the Sudetes which were endangered as a result of forest dieback in the 80s. Through the realisation of “ The Preservation Programme of Gene Resources and Selective Silviculture of Forest Trees for 1991-2010” a system of protection in situ and ex situ developed and the forest seed base was created. This base consists of:
- Permanent seed stands,
- Progeny plantations,
- Seed orchards
- Seed plantations,
- Selected plus trees.
These objects are legally protected.
The regionalisation of seeds and seedlings is also important as it aims at:
- The preservation of autonomy of as many as possible natural and native populations of trees and bushes species,
- The limitation of uncontrolled transport of regeneration material and strict definition of rules and directions of its transport,
- Taking genetic diversity of vegetation material into consideration in forest management,
- The adaptation of silvicultural methods to diverse conditions in different regions in Poland.
Reginalisation distinguishes 26 seed macroregions and 106 macroregions.
Silviculture planning in Polish forestry was based on the division of our country into eight natural forest regions and the system of sites classification.
In the process of “ecologisation” of Polish forestry, we can find two basic rules: diffusion and decrease of silviculture risk. The actions connected with them are:
- The choice of proper species for the site,
- Creating diverse forest structure,
- The preference of natural regeneration,
- Making nurturing cuts considering natural biogroups of trees,
- The improvement of sanitary state and vitality of trees.
In 1999, the General Director of State Forests replaced the Decree no 11 from 1995 and since then the new Decree no 11 a has been in force. At present, it is the basis of “ecological” management in State Forests.
The preservation of biological diversity is one of the most important aims of forest management. Forest Act from1992 introduces a definition of permanent and balanced forest management with reference to the sustainable forest management – SFM. This act introduces new elements of nature conservation to the forest management plan. It brings Promotional Forest Complexes into existence, regulates the rules of creating protection forests and preserving natural swamps and peat-bogs.
In 1995, the National Program for the Augmentation of Forest Cover started to exist and became a tool to increase biological diversity. In 1995-2000, 111.3 thousand ha were afforested out of planned 100 thousand ha. However, these afforestations took place mainly in northern and north-western Poland while they are mostly needed in the central part of the country. During preparation of the plan for 2001-2020, some changes were made as a result of environment and landscape preservation needs. In the programme for 2001-2020, 680 thousand ha are planned to be afforested. Such large-scale project may help or degenerate biological diversity. That is why, a detailed analysis of particular area needs is necessary. Therefore, the categorisation of communities in respect of their forestation preferences has been made and natural conditions as well as farming methods have been taken into account. Apart from creating forest complexes, it is also very important to make ecological corridors in a form of trees outside the forest. The areas which are priority for agri-environmental programmes or places valuable from historical or archaeological point of view should not be afforested. It is very important to maintain a mosaic of sites, which allows not only forests but also open areas and waters.