Survival, growth and physiological status of Acacia disparrima and Eucalyptus crebra seedlings with respect to site management practices in Central Queensland, Australia

Abstract

An improved understanding of important ecophysiological mechanisms underpinning tree water and nutrient use is necessary for developing and testing effective revegetation and restoration techniques in disturbed landscapes. A field trial was established in Central Queensland, Australia, to evaluate tree ecophysiological response to site management methods, including site preparation, herbicide application versus top soil removal (scalping) and fertilisation versus non-fertilisation. The influence of site management practices on plant survival, growth and foliar ecophysiological traits of Acacia disparrima (M. W. McDonald and Maslin) and Eucalyptus crebra (F. Muell.) seedlings was investigated within 22 months following tree planting. There was no difference in the survival of A. disparrima and E. crebra in response to the site preparation. However, there was a significant difference in growth response with both species showing greater mean periodic height gain in the herbicide areas compared to the scalped areas. Plant growth and survival of both species were unaffected by fertilisation, regardless of site preparation treatment. We suggest that the effects of fertiliser may have been masked by drought conditions experienced by seedlings in the first 6 months after planting. Neither site preparation nor fertilisation affected the leaf-level ecophysiological traits of seedlings, including foliar total N, photosynthetic capacity, instantaneous water-use efficiency, carbon isotope composition and stomatal conductance, irrespective of species. Scalping was more effective than herbicide application to suppress weeds and reduced the costs of site preparation and maintenance. Surprisingly, scalping had no impact on plant survival and foliar ecophysiological traits. However, it should be noted that the scalping may not be a sustainable practice in plantation establishment with short rotations where organic matter levels may not have a chance to recover between disturbances.