AN APPRAISAL OF FACTORS CONTROLLING THE LATITUDINAL DISTRIBUTION OF MANGROVE (AVICANNIA-MARINA VAR RESINIFERA) IN NEW-ZEALAND

The latitudinal distribution of mangroves (Avicennia marina var. resin ifera) in New Zealand has traditionally been considered to be controll ed by climatic stress, particularly air temperature. This paper review s the influence of climate factors, particularly frost, and the disper sal of mangrove propagules on the present-day mangrove distribution. T here is no strong evidence to show that the southern limit of mangrove s in New Zealand is a function of climatic conditions, or that the pre sent mangrove distribution is in equilibrium with climatic conditions. It is probable that coastal processes affecting propagule dispersal a re more important controls on the mangrove distribution within New Zea land than climatic factors. In particular, tidal asymmetry inhibits mi xing of east and west coast mangrove populations around northern-most New Zealand, and low coastal current velocities and large distances be tween suitable habitats makes natural establishment south of present l imits unlikely.