VEGETATION AND SOIL FACTORS ON A HEAVY METAL MINE SPOIL HEAP

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Abstract
The vegetation of a small Scottish [UK] metal-mine spoil heap was sampled by means of 70 0.25 m2 quadrats and classified into 3 groups. The most common species were Agrostis capillaris and Festuca rubra which were important constituents of all 3 groups. Soil samples were collected from each quadrat and analyzed for pH, loss-on-ignition, heavy metal and nutrient elements in the soil solution and for several physical properties. The mine spoil was physically and chemically heterogenous with many of the soil solution samples having potentially toxic concentrations of Cu, Pb and Zn. The vegetation data were ordinated: axis 1 of the ordination was significantly correlated (positively) with all 3 heavy metal concentrations, silt and sand, and (negatively) with loss-on-ignition and K concentration; axis 2 was significantly negatively correlated with pH and Ca, nitrate and phosphate concentrations. Consideration of this ordination and comparisons between soil parameters associated with each of the 3 vegetation groups and with nonvegetated quadrats, suggest that Pb and Zn may be the major determining factors of the spoil-heap vegetation. Low nutrients (except phosphate) and in some cases adverse soil physical factors might also be important. The apparently small influence of Cu is discusssed. Aboveground parts of 5 plant species [A. capillaris, F. rubra, Cerastium, fontanum, Rumex acetosa, Thymus praecox] were collected from the mine spoil and often had high heavy metal concentrations which differed between species. Some implications of interspecific differences in metal-mine occurrence within the genera Agrostis and Festuca are discussed.