Mortality of Eucalyptus marginata (jarrah) seedlings in Mediterranean‐climate forest in response to overstorey, site, seedbed, fertilizer application and grazing

Abstract The effects of overstorey, site, seedbed, seedling density, application of fertilizer and grazing on mortality of Eucalyptus marginata (jarrah) seedlings were studied experimentally in the northern jarrah forest of Western Australia. Rainfall, soil temperature, soil water deficits, leaf water potentials and photosynthetically active radiation (PAR) were monitored. Seedlings on sites with the overstorey removed experienced significantly higher soil temperatures for 9 months of the year (of up to 6°C), smaller soil and leaf water deficits during the dry season (minimum predawn leaf water potentials of ‐0.5 MPa compared to ‐1.6 MPa) and higher intensities of PAR (maximum values of 1900 umol m⁻² s¹ compared to 900 umol m⁻² s⁻¹), compared to seedlings on sites with the overstorey retained. Mortality off. marginata seedlings was greater on sites where the overstorey was retained compared to where the overstorey was removed, on low quality sites than high quality sites, and on undisturbed and lightly disturbed seedbeds compared to heavily disturbed seedbeds. Seedling density, application of fertilizer and grazing by vertebrates did not have a significant effect on percentage mortality. Most of the mortality occurred as water deficits developed in late spring and summer and was attributed to these water deficits. Some mortality that occurred prior to the development of substantial water deficits was probably caused by pathogenic fungi, We conclude that mortality of E. marginata seedlings in the northern jarrah forest of Western Australia can be minimized by reducing the density of the overstorey and by seeding into a seedbed that has had litter and groundcover removed and the soil disturbed.