Landscape history of a calcareous (alvar) grassland in Hanila, western Estonia, during the last three hundred years

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 17 05 and aerial photographs from 1951, and recent vegetation mapping from 199 1-1996. The seminatural, species rich alvar grasslands originate and are ma intained by grazing of domestic animals. Three hundred years ago the area w as mainly open grassland with sparse shrubs and some fields. Forty years ag o the vegetation pattern was similar, with some smaller forests and forest clear-cut areas present. Now, since grazing has ceased for ca. 40 years, on ly 30% of the area remains as open grassland and 70% as forest. Identificat ion of clusters of field layer vegetation using the program TABORD resulted in 8 clusters, which agreed with the empirically determined community type s. The field layer within the young pine forest (up to 20 year old pines) i s similar to the open alvar grassland. In older forests, the field layer ha s already changed. There were no phytosociological differences found betwee n ancient grasslands and grasslands on former arable fields or forest clear -cut areas. Decrease in species richness, compared to open grassland. was m ost 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 contin uation of traditional management (grazing and tree cutting) in alvar grassl ands is urgently needed in order to keep seminatural alvar grasslands open. The possibility to restore open grasslands remains as long as there is a p ool of grassland species available, especially in younger forests.