Stable carbon isotope ratio and nutrient contents of the Kandelia candel mangrove populations of different growth forms

Kandelia candel (L.) Druce, the dominant mangrove species on the west coast of northern Taiwan, has three distinct growth forms. To elucidate whether the growth of the dwarf form of K. candel is related to nutrient and water availability, we analyzed nutrient contents (N, P, K, Ca, Mg, Na) and carbon isotope ratios (δC) of leaves of four K. candel populations differing in canopy height. The objectives of the study were to investigate whether the dwarf K. candel populations have higher long-term water use efficiency and whether nutrient limitation is related to the growth of the dwarf form of mangrove plants. Leaves of dwarf mangrove populations had significantly higher δC values (1–1.5‰ higher) and thus higher long-term integrated water use efficiency than the taller mangrove populations. N and P contents were significantly lower in leaves and soils of the dwarf mangrove populations than in those of medium height and tall mangrove populations. In contrast, no significant difference was found in K, Na, Ca and Mg contents among leaves of the four mangrove populations. It is proposed that water and nutrient availability, especially of nitrogen and phosphorus, limit the growth of K. candel.