Abstract
The landscape history of the largest calcareous seminatural alvar site (ca. 700 ha) in Estonia, is described with the help of a historical map from 1705 and aerial photographs from 1951, and recent vegetation mapping from 1994-1996. The seminatural, species rich alvar grasslands originate and are maintained by grazing of domestic animals. Three hundred years ago the area was mainly open grassland with sparse shrubs and some fields. Forty years ago the vegetation pattern was similar, with some smaller forests and forest clear-cut areas present. Now, since grazing has ceased for ca. 40 years, only 30% of the area remains as open grassland and 70% as forest. Identification of clusters of field layer vegetation using the program TABORD resulted in 8 clusters, which agreed with the empirically determined community types. The field layer within the young pine forest (up to 20 year old pines) is similar to the open alvar grassland. In older forests, the field layer has already changed. There were no phytosociological differences found between ancient grasslands and grasslands on former arable fields or forest clear-cut areas. Decrease in species richness, compared to open grassland, was most drastic in forests of age 20-40 years where the canopy was most closed. Forests have spread more extensively in areas with deeper soil. The continuation of traditional management (grazing and tree cutting) in alvar grasslands is urgently needed in order to keep seminatural alvar grasslands open. The possibility to restore open grasslands remains as long as there is a pool of grassland species available, especially in younger forests.[PUBLICATION ABSTRACT]