Date of Award

2000

Degree Type

Thesis

Degree Name

Master of Science

School

School of Natural Science

Faculty

Faculty of Communications, Health and Science

First Advisor

Dr Adrianne Kinnear

Abstract

With the increased planting of E. globulus monoculture plantations, concerns surround the impact these mass plantings will have on the soil environment and wider ecosystem. Soil and litter mites are the dominant saprophages of terrestrial ecosystems, contributing to decomposition processes through their comminution and grazing activities. Despite the importance of mites to decomposition processes, there have been no investigations to date of the litter and soil communities under these plantations within Australia. This study investigated the impact of Eucalyptus globulus subsp. globulus (Tasmanian bluegum) monoculture plantations on the diversity and abundance of the soil and litter acarine (mite) fauna. Mite communities under three 8 year-old E. globulus plantations sited on reclaimed pastureland were compared with an adjacent native E. marginata (jarrah) forest and a grazed pasture in the mediterranean-type region of southwest Western Australia. Sites were sampled in spring 1997 and new sites randomly selected in autumn 1998. Large seasona1 variations in abundance and diversity were found between the sampling periods of spring 1997 and autumn 1998, influenced considerably by soil moisture. Species richness was consistently higher in both the soil and litter layers under native jarrah forest, with the E. globulus plantations intermediate in species richness between the native forest and grazed pasture. A total of 114 mite species/morphospecies was recognized; 16 Mesostigmata, 52 Prostigmata, 45 Oribatida (Cryptostigmata) and 1Astigmata. Species diversity in the surface litter was higher under the native forest, reflecting the greater heterogeneity of the litter. Diversity in the underlying soil was similar for the native forest and E. globulus plantation, although there were considerable differences in species richness. Soil diversity in the pasture was very poor in comparison to the two forest systems, reflecting the absence of a litter layer and reduced niche dimensions. The monospecific E. globulus litter possibly reduced niche variety by simplifying the physical habitat and reducing the variety of resources available for the saprophagous fauna, of which the oribatid mites are a major component. Consequently, the number of families represented in the microphytophagous, phytophagous and predator functional groups under the E. globulus plantation may have been reduced. The most common oribatid families under the plantation were those often reported from disturbed habitats, Oppiidae and Tectocepheidae, and those common in many habitats, Oppiinae and Oppiellinae. An important management implication arising from this study is that these plantations would harbour a more diverse mite fauna if planted as a mixed tree stratum.

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Biodiversity Commons

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