XVI International Botanical Congess

In northern Australia, mangrove species richness was greatest where soil salinities were moderate. These areas supported the greatest diversity of functional types, particularly those exploiting understory habitats. While mangroves differ in ability to grow in extremely low or high salinities, growth of most species is maximal in moderate salinities. There is a tendency for root growth to increase at the expense of leaf area, and for specific leaf area to decrease, with increase in salinity and with increase in salt tolerance of species. Such changes in allocation, together with reduction in photosynthesis with increase in salinity and decrease in light would lower the fraction of carbon available for growth and limit survival in shade. Thus, there may be physiological constraints on species richness if understory niches were to become unavailable with increasing salinity.