Síkfőkút LTER Europe site is a temperate deciduous forest site, unmanaged since the late 1960ies. It is situated in the Szőllőcske forest reserve area on the southern foothills of Bükk Mountains, NE Hungary. The site is covered by a mature coppice oak forest (105 years old) with Q. petraea and Q. cerris in the upper canopy layer and other woody species occurring in the secondary canopy layer and shrub layers (Acer sp., Cornus sp, Euonymus sp., Crataegus sp.) The site was seriously impacted by oak decline during 1980ies. The soil has been classified as a brown forest soil type according to the Hungarian Soil Classification System which corresponds to Luvisol according to FAO WRB. Long-term data are available on climate, soil variables and forest structural and functional characteristics (for period 1973-2016).