Relationship Between Plant Species Richness and Age of Woodland Patches (Ojców National Park, Poland)

Woodlands in different regions of Central Europe are mosaics diversified by floristic richness and age. The age of woodlands is understanded as the period of permanent existence of woodland phytocenosies, or at least a woodland site, without any transformations, even for a short period of time, to agricultural fields or any other areas managed in different ways. Forests which occur in identical habitats are often differentiated of their species richness. Data gathered from studies carried out to date, indicate that the age of a forest plays a significant role in the way plant communities develop. This relationship, however, is modified by a number of other factors.In this paper, an attempt was made to answer the following questions: 1) are there any differences in this relationship between woodland age and richness, and species composition of recent and ancient forests, 2) does the age of a forest affect the richness of vascular plant species in the layers of their vertical structure, the number of species of various phytosociological groups, 3) which of the selected factors affecting the processes of migration and colonization, alongside age, affect the richness of species noted in forest communities.The Ojców National Park (OPN) was chosen as a study area because its forests are diversified by age, from the younger than 71 to the older than 216 years and because the history of the forests there have been well documented. Age of selected woodland patches was determined using a ‘Map of distribution woodlands of different age in the Ojców National Park’, whereas the remaining factors were either measured or determined in the field or using available sources. In order to establish relationships, a multiple regression model was used.The results obtained in the study prove that, in OPN, the age of the forest is the principal factor affecting the overall number of vascular species. Old forests are most abundant in species, and many plant taxa occur only in such forests. Within the same age classes, the number of taxa is often diversified because of the impact of habitat factors e.g., humidity, and it is also linked to the history of the development of these forests. The factors which affect the species richness in a particularly beneficial way is the presence of rocks, as well as the diverse relief of a given area. Much less significant are exposure and inclination of the terrain.The age of a forest significantly affects the number of species in the herb layer, whereas it does not demonstrate significant correlations with respect to shrub or tree layers. The number of species in fertile deciduous forests are also positively affected, whereas no such relations were found in coniferous forest species. The results also indicate that the forest’s surface area, along with a specific combination of factors, may only have a limited effect on the richness of plant species in the area.