| Survival and growth of the epigeic earthworm, Dendrobaena octaedra (Savigny) in lodgepole pine forest floor materials and effects of the invasion of D. octaedra into pine forest floor on soil physical (structure) and chemical (pH, organic matter, %C, %N) parameters, microbial activity and the communities of soil fungi and oribatid mites were studied under conditions of optimum temperature and moisture in laboratory mesocosms over six months and under field conditions over two years.; Moisture content was the major limiting factor for survival of D. octaedra. Maximum growth of D. octaedra occurred in fermentation material and decreased growth in worm-worked humus material.; In the mesocosms organic matter content of the humus layer was significantly reduced from 72% to 47% by worm activities at three months. Microbial biomass was significantly reduced from 11300 to 7400 and from 6800 to 4600 {dollar}mu{dollar}g microbial biomass-C g{dollar}sp{lcub}-1{rcub}{dollar} soil in the fermentation and humus layers, respectively. The number of fungal isolates per plated particle was highest at intermediate levels of worm activity, probably due to addition of new substrates for fungal exploitation. Fungal species negatively affected by worm activities tended to be aggregated, suggesting that microhabitat specialists were being adversely affected by worms. Similarly, maximum oribatid and faunal abundances occurred at intermediate levels of worm activity probably due to increased microhabitat diversity.; In field plots organic matter content, total nitrogen, carbon, basal respiration and qCO{dollar}sb2{dollar} decreased with increasing worm biomass, suggesting that D. octaedra reduced nutrient availability for the microbes. Worm activities decreased fungal (29 to 22) and oribatid (18 to 13) species richness, number of fungal isolates per plated particle (2.5 to 1.8) and abundances of several fungal (Mortierella ramanniana, Oidiodendron scytaloides, sterile darks 875, 876, 877) and oribatid (Liochthonius simplex, Sellnickochthonius immaculatus, Oppiella nova) species and faunal groups (juvenile and adult oribatids, mesostigmatids, total mites). The field study appeared to represent a later stage in the invasion of D. octaedra than the mesocosm experiment. Expected declines in fungal and oribatid species richness, diversity and abundance due to higher worm biomass in the field relative to the mesocosms were not observed, possibly due to increased stability associated with more diverse fungal and oribatid communities in the field. |
