Eucalypt regeneration and ecological restoration of remnant woodlands in Tasmania, Australia

摘要: Lack of eucalypt regeneration is a key factor in the decline forest and woodland remnants low rainfall agricultural regions Australia. This thesis provides new insight into dry by demonstrating how important tightly circumscribed seedling niche these forests Tasmania. The potential soil water repellency to be barrier recruitment difficulty mimicking improve natural processes degraded are highlighted. A section on management implications included. Key effective woodlands an understanding requirements conditions that promote seed germination establishment (recruitment niche) persistence lignotuberous sprouts (juvenile niche). were investigated Midlands Tasmania at scales stand microsite. work was conducted with view applying results discipline restoration ecology. Measurements structural complexity thirty remnant stands range stages revealed healthy contained four times amount (seedlings, saplings) than condition absent paddock trees (except for one which there had been fire). An additional lack smaller diameter size classes both intermediate tree sites relative amounts shown implies long-term scarcity unavoidable future bottleneck development mature trees. quantity positively associated other attributes: perennial species life form richness; cover vegetation 0.5-6m high; litter; dead trees; large total length fallen logs >10cm diameter; negatively quadratic mean breast height. Across stands, majority saplings. Only burnt 2-6 years prior survey did newly recruited seedlings part regeneration. Within differed significantly juvenile (occupied sprouts), while characteristics similar general floor. Seedling microsites characterised following: canopy gaps ashbeds; predominantly northerly aspect; over 220° shelter profile; average distance sheltering object < 30cm; provided coarse woody debris (80% sheltered branches); softer less repellent floor; grass. All affect moisture availability. The role ashbeds, further investigated. Soil (hydrophobicity) can severe as hydrophobic organic compounds coat surfaces particles this has movement storage system. Other studies have hydrophobicity differentially affected fire depending temperatures reached, increasing temperature increases until threshold reached removed (approximately 260°C). Logs lying floor provide heavy fuel intense creates ashbeds. current study showed ashbeds surface layers but layer moved lower (1-3cm) down profile. wettable zones enabled subsequent seedlings. Remaining adjacent partially store (with threefold under compared 5m away) probably protection from microclimatic fluctuations browsing animals. Surface outside ashbed areas severely suggesting may lightly unburnt soils. These findings applied ecology. Patch scale trials six attempt mimic niches through use spot burns or cultivation without addition logs. Survival established introduced rain variable within among resulting no treatment effects. Thus ‘Burn logs’ not successfully niche, because experiment heterogeneity following wildfire. However, survival planted greatest ‘Cultivated log’ treatments, most closely resembled niche. Burning treatments relatively weed-free bed year surviving grew better those cultivated quickly became infested grassy weeds despite granular herbicide application. Survival observed sown each correlated score planting site higher condition. suggests more crossed abiotic (using state transition model terminology) completely experimental treatments. early also species; underlying plot; proximity adult type amelioration used presence absence logs. Suggestions include trialling burning retaining situ rather post burn addition; investigating timing intensity weed control treatments; testing effects wetting agents; spatial aspects patch placement.