Agriculture and Food Systems - Theses

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    Ecological benefits of termite soil interaction and microbial symbiosis in the soil ecosystem in two climatic regions of Australia
    Ali, Ibrahim Gima ( 2015)
    Termite soil interaction is a multidimensional process, the interphase between the surface and subsurface being the most prominent location termitaria and other termite structures usually occupy. Genetic and environmental conditions, including soil type and moisture content, in different climatic regions affect this interaction. There is scant information on termite preferences, foraging behavior within these conditions and impact on soil profile and associated symbiont microorganisms. Foraging activity of termites (Coptotermes frenchi), depth and changes in soil profile with layers of top soil, fine sand, coarse sand and gravel, was studied using a test tank in a laboratory. Termite activities were intensive in only the longest foraging galleries via which they reached and foraged up to the edge of the tank. Wood stakes inserted vertically at three different depth level intervals (0-100, 100-200, and 200-300 mm), visual observations of soil profile samples taken using auger and excavated cross sections of the soil profile all confirmed presence of termite activity, transport and mixing of soil up to the lowest horizon in the otherwise uniform sandy or gravely lower horizons. However, termite activity did not result in complete mixing of soil horizons within the study period. Termites (Coptotermes acinaciformis) were tested for their preference topsoil, fine sand, potting mix and peat, in a laboratory condition at soil moisture contents of 0, 5, 10, 15 and 20% for 30 days. The experimental apparatus involved termite colonies foraging from nesting jars connected to four sets of standing perspex tubes filled with each soil type and moisture content combination attached to the jar lid on top. Soil type had a significant effect on termite preference whereas soil moisture content did not. At lower moisture levels of 0 and 5%, termites preferred fine sand while topsoil was preferred at 10, 15 and 20%. Soil heterogeneity and textural variability with respect to particle size distribution due to termite activity was investigated in two climatic regions of Australia. Mound and surrounding soils of Coptotermes lacteus in Boola Boola State Forest, Victoria, and Amitermes laurensis and Nasutitermes eucalypti in Gove, Northern Territory were studied. The residual effects on bacteria and fungi counts were also investigated in the former. For C. lacteus and A. laurensis mounds the very fine particles sizes (< 0.045 mm) were significantly higher than that of the surrounding soil while the reverse was true for the 2 - 1 mm particle size ranges. For the Nasutitermes mound, however, they recorded significantly higher 2 - 1 mm particle sizes and significantly lower < 0.045 mm particle size ranges than the surrounding soils. For the other particle size ranges in both sites no significant difference was observed between the mound and surrounding soils except for the 0.5 – 0.2 and 0.20.063 mm ranges in the A. laurensis mound which were significantly higher than surrounding soil. Average moisture content of the surrounding soils was significantly higher than that of the mound surfaces which could have resulted in the higher bacteria and fungi counts (cfu/ml) in the surrounding soils.