2003, Li, Jin, Duggin, John Alexander, Grant, Carl, Loneragan, WA

Establishing native eucalypts in grasslands developed by the historical clearing of forests and woodlands has to overcome significant difficulties brought about by past land use activities and associated environmental changes. Options for establishment include natural regeneration from remnant trees, direct sowing or tree planting. 'Eucalyptus blakelyi' is a significant species on the New England Tablelands, being just north of the central part of its ecological range and is potentially useful for ecosystem rehabilitation, agroforestry and farm forestry. The aims of this series of studies are to determine the effects of cold temperatures resulting from microclimate changes on germination and early survival of 'E. blakelyi', the level of seed predation by ants, and the effectiveness of site preparation techniques on survival and growth of seedlings planted in grasslands. Germination of local seeds collected from the New England Tablelands was tested under constant and alternating temperatures, either in the dark or under 12 h light/dark cycle. 'E. blakelyi' exhibited optimal germination between 15 and 25°C with the maximum occurring at 15°C under constant temperatures, and at 15–25°C under alternating temperatures. Light had a significant and positive effect on germination under both constant and alternating temperature regimes, although this difference was not significant at temperatures around the optimum. Seedling survival decreased significantly as temperature decreased from −5 to −10°C, as exposure time to low temperature increased from 1 to 4 h, and as seedling age increased from 1 to 8 weeks. Ant predation was high with 73% of the seeds removed within 7 days. Four site preparation techniques (grazing exclusion, cultivation, burning and fertiliser) were used in a factorial arrangement to examine their interactions and influences on seedling survival and height growth 30 months after establishment. Grazing significantly reduced seedling survival and height, whereas soil cultivation and burning significantly increased them. Survival and height were consistently lower when fertiliser was added to grazed plots across all cultivation treatments including the control. When grazing was excluded, fertiliser significantly reduced survival with cultivated treatments, and increased height only with shallow cultivation (to a depth of 5 cm) while it significantly reduced height with deep cultivation (20 cm). The interactions amongst the various treatments identified that seedling survival and growth were best when grazing was excluded and the site was deep cultivated without the broadcast application of fertiliser. Fire has an additive effect on seedling survival and height growth. The main benefits of this combination of treatments lie in preventing browsing and trampling damage by livestock, reducing competition from the herbaceous layer, removing litter, and possibly alleviating potential allelopathic effects.

2006, Mercuri, Amanda, Duggin, John Alexander, Daniel, Heiko, Lockwood, Peter Vincent, Grant, Carl

Commercial forestry plantations as a post-mining land use in the Upper Hunter Valley of New South Wales, Australia are restricted by both the poor nutrient availability of mining substrates and low regional rainfall. An experiment was conducted to investigate whether municipal waste products and saline groundwater from coal mining operations could improve early tree growth without impacting on the environment through salt accumulation and/or nutrient enrichment and changes in groundwater quality. Potential impacts were investigated by quantifying the nutrient cycling dynamics within the plantation using an input–output mass balance approach for exchangeable calcium (Ca²⁺), exchangeable magnesium (Mg²⁺), exchangeable potassium (K⁺), exchangeable sodium (Na⁺), nitrogen (N), and phosphorus (P). Measured inputs to and outputs from the available nutrient pool in the 0–30 cm of the overburden subsystem were used to estimate the net effect of unmeasured inputs and outputs (termed 'residuals'). Residual values in the mass balance of the irrigated treatments demonstrated large leaching losses of exchangeable Ca, Mg, K, and Na. Between 96% and 103% of Na applied in saline mine-water irrigation was leached below the 0–30-cm soil profile zone. The fate of these salts beyond 30 cm is unknown, but results suggest that irrigation with saline mine water had minimal impact on the substrate to 30 cm over the first 2 years since plantation establishment. Accumulations of N and P were detected for the substrate amendments, suggesting that organic amendments (particularly compost) retained the applied nutrients with very little associated losses, particularly through leaching.

2005, Mercuri, Amanda, Duggin, John Alexander, Grant, Carl

Commercial forestry plantations as a post-mining land use in the Upper Hunter Valley NSW, Australia, have productivity limitations and are restricted by the poor nutrient quality of mining substrates and low regional rainfall. However, municipal waste products and saline groundwater from coal mining operations can assist in establishing and improving plantation growth rates. The aim of this study was to investigate the establishment and growth of four potentially commercial species in a saline irrigation and nutrient amendment experiment over 2 years. The experiment was designed as a split–split plot with irrigation being the main plot effect, nutrient amendments (overburden, fertiliser, biosolids, compost and topsoil) as the subplot effect and species ('Corymbia maculata' Hook, 'Eucalyptus botryoides' Smith, 'E. tereticornis' Smith and 'E. occidentalis' Endl.) as the sub-subplot effect. Survival, height, diameter, above-ground biomass, tree form and weed competition in each treatment were measured along with substrate electrical conductivity. Tree survival after 24 months improved with irrigation (89.8%) compared to the rain-fed treatment (78.6%). Irrigation did not significantly improve tree growth responses but there was an increasing trend after 24 months with irrigation producing better overall growth. Biosolids, compost and fertiliser produced significantly better growth than the topsoil and overburden treatments. However, weed growth was higher in biosolids and compost and was correlated with reduced tree growth but not less than topsoil and overburden treatments. 'Eucalyptus occidentalis' performed significantly better than other species in relation to height (1.89 m), diameter at 30 cm (3.1 cm) and standing crop biomass (982 kg ha⁻¹) after 2 years. Surface substrate EC1:5 (0–10 cm) increased significantly following irrigation events but reduced over time by leaching from rainfall. Electrical conductivity in the lower horizon (10–30 cm) was not significantly different from the upper horizon in the irrigation treatment but was significantly higher in the rain-fed treatment after 2 years. Biosolids and compost increased EC1:5 over the first 6 months but thereafter compost and overburden produced higher values during the second year of the study. These results show that saline mine water irrigation can be used to establish plantations without impacting deleteriously on tree growth and substrate EC1:5. However, further research is required to determine whether growth rates will reach a commercial standard and that the long-term impacts of using saline irrigation water are avoided.