Soil factors affecting tree growth on former opencast coal land

AbstractThe growth of three tree species (Alnus glutinosa, Betula spp. and Quercus spp.) was related to soil factors on two restored opencast coal sites in South Wales, UK. The main factors favouring tree growth were greater soil depth and organic content. Factors limiting growth included poor site drainage and high magnesium levels. Whilst all species were related to most of the above factors, soil depth was of particular importance for Alnus glutinosa and Betula spp., whilst site drainage had the greatest influence for Betula spp. Soil‐tree associations tended to be closer on the older of the two sites. Combinations of soil depth, percentage clay and percentage organic content in a multiple regression predicted around 40 per cent of the growth variation in Alnus glutinosa, between 6.9 and 32 per cent of that for Betula spp. and between 14.5 and 32.6 per cent of that for Quercus spp. Growth prediction for Betula spp. improved to 40.9 and 34.8 per cent when a site drainage factor was included in the regression. The development of such predictive relationships might contribute to the planning of site reinstatement for tree planting after opencast mining, and to a better ‘matching’ of tree species to site characteristics.