Benefits of weed control and fertiliser application to young Eucalyptus dunniistressed from waterlogging and insect damage

SummaryA trial designed to measure benefits to growth of post—establishment weed control and fertiliser (diammonium phosphate, DAP) application in a young Eucalyptus dunniiplantation was used to test whether young trees benefiting from such silvicultural practices were more resilient to stress from waterlogging and insect damage. Chlorophyll fluorescence (Fv/Fm) was used as the measure of tree stress. Both the weed control and fertiliser treatments had significant beneficial effects on diameter and height of surviving trees. Tree growth response was greater for weed control than fertiliser application. Neither treatment, however, appeared to alleviate the impact of flooding on tree mortality. Insect damage, in particular from the leaf blister sawfly Phylacteophaga froggatti, was negatively correlated with tree size, which in turn was directly influenced by the degree of soil inundation, weed control and fertiliser application. It is argued that growth results from a balance of beneficial conditions and a range of stressful factors. Post—establishment practices such as weed control and fertiliser application can improve tree resilience to stress-inducing factors that cannot be managed easily.