Development of forest-soil systems on quarry detritus of open-cast oil-shale mining

摘要

Studies were carried out in North-East Estonia on the skeletal calcareous detritus of open-cast oil-shale (kukersite) mining, afforested in 1962-1978 with two-year sets of Scots pine (Pinus sylvestris) and silver birch (Betula pendula). During 2-3 decades highly productive stands developed with an average annual increment in the growing stock of 2-8 solid metres per hectare and with an average annual increase of 20-50 cm in height and 2-5 mm in the breast-height diameter. The depth of the O2-A-AC-BC profiles of simultaneously formed Calcaric Regosols and/or Rendzic Leptosols is 20-30 cm, in which 80-240 g m~(-2) yr~(-1) of organic carbon and 2-8 g m~(-2) yr~(-1) of nitrogen have accumulated. R_2O_3-humic-fulvic humus, rich in Ca-fulvates, is characteristic of both ground litter and of the epipedon which is close to the mollic. As a result of humification, some residual kukersite (14-44 g kg~9-1)) has participated in the formation of the insoluble fraction of humus. Humus colloids prevail in the soil exchange complex saturated with alkaline earths, although pedogenetic argillisation already exerts an impact on increase in exchange capacity. Changes in nonsiliceous iron relationships reveal a slight development of cambic properties in primarily formed soil sections. The formed ground litter of Moder type represents a driving force in intensification of humus accumulative soil development. An important role is played by deep-rooted grasses. Normally functioning forest―soil systems have originated already within the second decade after detritus rehabilitation for forestry and progressed during the third decade.