Plant species richness of afforestations with different former use and habitat continuity

In northeastern Germany, the presence of 148 vascular plant species in 155 woodlands, which have been planted during the last 200 years, was observed. Woodlands existing continuously from the 19th century were called old woodlands whereas those from the 20th century were called recent woodland. Five species were significantly associated with old woodlands whereas six species were more often found in recent woodland. There was no significant difference in the total number of species, apart from the higher number in shrub and herb species in woodlands formerly used as grassland compared with those on former arable field. Forty-one species were significantly associated with recent woodland formerly used as grassland in comparison to woodlands formerly used as arable field. The relatively low intensity of disturbance and the ability to survive with very small populations in pastures and meadows may explain why a relatively large number of true woodland species occurred predominantly in woodlands created on grasslands. The results show that former use is important to many species whilst habitat continuity plays a minor role provided that the time frame is only about 150 years. A comparison of species with preferred occurrence in woodland established on grasslands with species without preference shows clear differences in their Ellenberg indicator values but only few differences in the plant’s life history traits. Species occurring predominantly in woodland formerly used as grassland reach on average higher indicator values for moisture, soil reaction, nitrogen and have a higher tolerance regarding susceptibility to human disturbance. The development of semi-natural afforested sites seems to be more efficient on grasslands than on arable fields. Moreover, afforestations on grasslands contained more endangered or relatively rare species than those on arable fields. The results of this study stress the necessity of careful studies of land use history to understand the development of a landscape and the present distribution pattern as well as the diversity of plant species in various habitats.