Plant communities are the basic types of phytocenoses, distinguished on the basis of the species similarity. Not all the communities groups are identified in a complete way. In Poland, there are 485 plant associations (Matuszkiewicz, 2001). Among them:
12 % constitute associations frequently encountered in all the country or in many regions,
5 % constitute associations unevenly distributed in the country, in some regions very common, absent in others,
37 % constitute moderately common associations, existing in all the country or in many regions,
24 % constitute moderately common associations, existing in some regions,
22 % constitute rare associations, existing in few regions.
Geographical diversity is a specific feature of Polish vegetation. According to Matuszkiewicz's work 12 % of plant associations should be treated as Polish endemic plants; about 40 % of them are of eurasiatic character, 3% are Atlantic-West-European associations, 1% ocean-South-European, 4% continental-South-European, and 10 % are of boreal-North-European character.
Today's potential natural vegetation describes the hypothetical flora which would be achieved as a result of natural succession, if the developmental tendencies of presently existing vegetation could be fully realized, in case of total cease of man's activity. According to the map of potential vegetation of Poland (W. Matuszkiewicz and others, 1995), most areas of our country constitute possible forest communities. 13,6 % area of Poland are possible beech forests, 41,6 % oak-hornbeam forests, 2,9 % thermophilous oak forests , 8,9 % riparian mixed forests , 5,2 % acidic oak forests, 13,9 % mixed coniferous-broadleaf forests, 10,2 % pine forests and 1,2 % spruce forests.
The communities which are rare in the country are very valuable and should be given protection. The examples of such communities are: xerothermic meadows, orchid-beech forests, oligotrophic or lobelia lakes and the communities built by the species which exist in only single places in Poland (e.g. downy oak (Quercus pubescens) in Bielinek by the Odra river.
Individual plant communities have different dynamism. Some of them widen and some narrow down their occurrence. There is also a group of disappearing communities or threatened with extinction. A specific group consists of semi-natural communities which disappear owing to the cease of traditional farming. The communities connected with rare and specific habitats, e.g. xerothermic meadows comprise another group. Many communities vanish because of the changes in water conditions. Especially peat-bogs disappear as a consequence of drainage.
The communities representing the majority of natural and semi-natural types of communities are preserved in a classic way. First of all, there is a areal protection such as national parks, nature reserves and others. Moreover, along with the acceptance of European legislation, it is necessary to verify the objects and areas under protection and to introduce the network of objects Natura 2000. This network is based, among other things, on „Habitat directive” (Council Directive 92/43/EEC of May 1992).