Aspects of the ecology of broom (Cytisus scoparius) in Canterbury, New Zealand

Abstract

Broom (Cytisus scoparius) is more abundant than gorse (Ulex europaeus) on the younger surfaces of Canterbury river beds and this is reflected in the number of seeds extracted from fresh alluvium. The patterns of emergence from alluvium in glasshouse experiments and in the field are described. Experiments on broom seedlings showed they developed a single leader in reduced light, in contrast with gorse, and they can grow in 10% light. They grow on a range of natural soils and respond readily to superphosphate. The measurement of growth and phenology of broom in Canterbury showed growth to be most rapid at the lowest altitude site, where there were major and minor flowering periods. Shoot elongation was depressed during the main period of fruit maturation. The growth and phenology of broom in New Zealand appears to be more vigorous than in Europe, partly because of the absence of its major invertebrate predators. The adaptations of broom for the wide range of sites it occupies in New Zealand is demonstrated with reference to its position on the "r" and "k" continuum.