Soil fauna colonization of high elevation coal mine spoils in the Canadian Rockies
Date
1986
Authors
Lawrence, Joanne Marilyn
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Abstract
The soil arthropods, nematodes and enchytraeids colonizing high elevation coal mine spoils near Sparwood, British Columbia, were extracted from 2, 5, and 9-year-old reclaimed spoils and undisturbed subalpine meadow soil, over a 4-month period during 1982. This information was then interpreted in view of certain biological and physical site features, to facilitate recommendations regarding current reclamation techniques and objectives.
The number of taxa increased with site age, as did the mean density of most soil fauna. Early colonizers were probably opportunistic species exhibiting tolerance to adverse environmental conditions, good dispersal abilities, high reproductive rates, and subsequent rapid density increases in response to fertilization. These initial colonizing fauna were probably plant, bacterial , or unspecialized feeders. Undisturbed subalpine meadow soil had considerably higher numbers of taxa and densities of microarthropods than reclaimed mine spoils. Mites numerically dominated the microarthropod fauna in all sites; most mites were of the suborder Prostigmata, and most prostigmatid mites were Tydeidae. Some members of this and the other abundant prostigmatid families have been reported to be early colonizers, and to occur predominantly in soils with a low organic matter content.
Collembolans and insects were minor contributors to the total soil fauna, although hypogastrurid collembolans did exhibit high densities on the 5-year site. Soil insect populations were predominantly Coleoptera and Diptera larvae, with an abundance of Thysanoptera on the youngest reclaimed site.
Soil nematodes were rare on the youngest reclaimed site, yet abundant in the remaining three sites. Nematode densities were lower in the undisturbed subalpine meadow soil than normally reported in undisturbed temperate grasslands, perhaps as a result of predation pressures by tydeid mites. Enchytraeid worms occurred mainly in undisturbed meadow soil.
A general pattern of increasing microarthropod densities over the 4-month sampling period was observed on most sites. Nematodes on the three oldest sites exhibited similar high densities in June and August, possibly reflecting synchronized reproductive peaks.
Poor soil physical conditions on all reclaimed sites is reflected in the occurrence of most soil fauna in the upper 3 cm. This trend was not observed between 0-3 cm and 3-7 cm depths on the subalpine meadow site, due to more amenable soil conditions.
Soil fauna colonization on these sites increased at a high rate of change during the early successional period (ie. between the 2 and 5-year sites), with no significant increase in faunal densities later in the successional sequence (ie. between the 5 and 9-year sites). A similar pattern was observed with increases in root, litter and above-ground biomass with site age. Decreases in pH and coarse fragment content, and increases in percent soil moisture, cation exchange capacity and soil nitrogen levels were also observed with increasing site age, due primarily to the weathering of spoil material and the accumulation of organic matter from decomposition processes. However, soil fauna and most soil physical conditions still differed considerably between the oldest reclaimed and subalpine meadow sites. Given the paucity of important decomposer fauna on these sites, mites and collembolans probably play an important role in the decomposition process. Reclamation efforts should attempt to create microsites conducive to developing beneficial soil fauna populations. Mulch or topsoil applications may provide both favorable microsites, or sources of colonizing soil fauna and flora. The introduction of non-native beneficial species such as earthworms may also prove useful.