Colonization of Industrial Reclamation Sites by Acari, Collembola and Other Invertebrates

(1) The soil fauna colonizing four reclaimed coal pit heap sites in Northumberland, England, were sampled monthly for 2 yr (1971 and 1972). The sites were at different stages of reclamation when sampling commenced. Two of the sites were planted with grass and trees and two with grass only then grazed by cattle. (2) The population density of mites was low before, but rose rapidly to a maximum of 131 x 103 m-2 after reclamation was completed and the sown grass and clover seeds had germinated. The pioneer mites on the younger sites were Astigmata and the prostigmatid families Tarsonemidae, Pyemotidae and Nanorchestidae. Even on the older sites, Mesostigmata were never abundant and few Cryptostigmata were found. Seasonal fluctuations of density occurred on the older sites with maxima in the late autumn and winter and minima in the summer or early autumn. Some negative associations between groups of mites had developed on the older sites. (3) Thirty-three species of arthropleone Collembola were recorded, eighteen of which occurred on all four sites. Their population densities were low initially (0-3 x 103 m-2) but rose rapidly, probably due to the low density of predators. By the end of the survey, a very high density had been attained on the younger woodland site (152 x 103 m-2 in December). On the two older sites, seasonal fluctuations of density were detected with maxima in spring and autumn or winter, and minima in summer. The species able to live in bare shale were quickly superseded by a fauna more typical of agricultural soils as the vegetation cover developed. Populations were dominated by either Tullbergia krausbaueri (Borner) or Isotoma notabilis (Schiffer) and only on one older site was more than one species dominant. In the second year of the survey, Isotomidae (mainly Isotoma viridis Bourlet and L notabilis) made up much of the total biomass. (4) Some 'other' arthropods (symphypleone Collembola, Hemiptera, Araneida, Thysanura, Diptera larvae and Coleoptera) occurred irregularly in low numbers; earthworms had not penetrated the sites by the end of the survey. (5) It is concluded that despite the extreme conditions existing on reclamation sites, Acari and Collembola can colonize the soil rapidly, especially when the vegetation cover is developed. In the absence of a large number of predators, the density of the fauna has been shown to rise to a very high level within 2 yr.