Phenology of N2-fixing nodules in pruned clones of Erythrina poeppigiana

Nitrogen-fixing nodule biomass (NM), leaf biomass (LM) and young leaf ureide-N concentration (CUN) of two clones (2660 and 2693) of Erythrina poeppigiana (Walpers) O.F. Cook were monitored during a six-month pruning cycle. Before the first pruning, the NM means were 102 g tree1 for 2660 and 35 g tree1 for 2693. Nine weeks after pruning (WAP), NM was almost nil for both clones. By 17 WAP, NM had increased to 138 g tree1 for 2660 and 112 g tree1 for 2693. A period of high temperature and low soil moisture around 17 WAP corresponded to a major leaf fall. By 24 WAP, NM had dropped to values similar to those observed before the first pruning. Nodule phenology of pruned E. poeppigiana was apparently linked to availibility of photosynthate. CUN was low during the whole cycle (220 to 380 ¿g g-1 dry leaf) and was not correlated with NM. At 24 WAP, LM and CUN differed significantly among four clones (2660, 2662, 2687 and 2693), but NM varied widely within clones. There was no significant correlation between NM and CUN of individual trees. Leaf CUN may not be a reliable indicator of N2-fixing activity in E. poeppigiana