The nutritional role ofLupinus arboreus in coastal sand dune forestry

Summary In the artificial plant succession used to stabilise coastal sand dunes in New Zealand,Lupinus arboreus is sown into plantedAmmophila arenaria stands primarily to provide shelter for youngPinus radiata trees. Recent observations have suggested that the lupin may play a nutritional, as well as a physical part in the stabilisation technique. Work elsewhere with otherLupinus spp. and forest crops supports this theory. An attempt is being made to evaluate the significance ofL. arboreus at Woodhill State Forest with a view to possible manipulation of nitrogen supply to the tree crop. Work described in this preliminary paper has established that the presence of undamaged lupin plants can increase nitrogen uptake inP. radiata through the influence of litter and seedling exudate. Their effect could be due to direct nitrogen transfer or to stimulation of non-symbiotic nitrogen fixation. Lupin leaf washings were shown to contain ninhydrin-positive substances but did not influence nitrogen uptake byP. radiata seedlings in this experiment. N. Z. Forest Service Paper No.452. O. D. C. 237–52.