Exclusion of human interference from national parks and nature reserves commonly results in undesirable successional changes in the vegetation. First of all the semi-natural plant communities, which have been formed and maintained by traditional methods of extensive land-use—mowing, grazing, burning, etc.—are affected. In Poland this has happened, for example, to the halophytic meadows on the Baltic coast, the secondary xerothermic (‘steppe’) grassland in the southern highlands, and the mesic hay-meadows of the forest zones in the Carpathian Mountains. When neither mown nor grazed, they all lose more and more of their typical components, and finally disappear. Many such communities originated hundreds or thousands of years ago and include a number of native plant species which cannot be found in any of the natural vegetation types.The problems of conservation of semi-natural plant communities have been studied by the Author in three representative areas of Southern Poland: in the Gorce Mountains (Western Carpathians), the Niepolomice Forest, and the Ojców National Park near Cracow. In the Gorce Mountains about half the existing major plant communities belong to the semi-natural category and exhibit a much higher species-diversity than the natural forest vegetation (Table I). Similarly, in the northern part of the Niepolomice Forest, many more species are concentrated in the semi-natural, non-forest communities than in natural ones (Table II). For the Ojców area two maps, one of the actual vegetation and another of the expected or ‘potential natural’ vegetation, were compared and the topographic arrangement and successional trends of plant communities established (Table III). It became evident that, if all human impact were to be excluded from the Park, the rich semi-natural plant communities would completely disappear and many of their interesting components would become extinct at least locally.These data, as well as similar observations reported by other authors, explicitly demonstrate that very often the existing vegetation diversity in national parks and nature reserves may be maintained only when the ecological situation has been rightly understood and the proper management adopted.
Classification of the natural vegetation of Mtendere Game Ranch in the Chibombo District of the Central Province, Zambia
