A study was undertaken of the health and condition of riparian vegetation along the estuary-river transition zone of the Hastings River after observations noted that trees and understorey species were stressed and appeared to be dying as the drought worsened in late 2002, river flows declined significantly and the river ceased to flow over short periods, and salinity concentrations increased as the salt wedge pushed upstream. The principal causal factors likely tn be involved in vegetation decline include salinity, drought and subsequent soil moisture stress.

The impact of vegetative filter strips to reduce the delivery of nonpoint source pollutants from agricultural land to inland water systems is now recognized as an important element in overall agro-ecosystem management. A glasshouse experiment was undertaken to measure the effectiveness of tree ('Eucalyptus camaldulensis' Dehnh. and 'Casuarina cunninghamiana' Mq.) and pasture filter strips to intercept lateral movement of NO₃–N in soil water. Tree treatments retained significantly more NO₃–N associated with shallow soil water movement (between the A and B soil horizons) than bare ground. Nitrate-N removal was not significantly different between trees and pasture, and among the tree treatments. However, uptake and accumulation of NO₃–N by pastures was significantly (P < 0.001) greater than the trees. Th e average rates of N accumulation were 0.82 g m⁻² and 1.52 g m⁻² wk⁻¹ for the tree plots and the pasture plots, respectively. Th e experiment also showed that the effi ciency of NO₃–N removal from soil solutions by trees was greater when NO₃–N concentrations were relatively higher in the soil (81.4% removal at 20 mg L⁻¹ compared to 68.1% at 10 mg L⁻¹).