The Leaf Economic Traits And Element Concentrations Of Mangrove Plants In Southern China

Mangrove plants are the particular species living in the tidal tropical and subtropical zones, they have been called "coast guard" by people. Mangrove forests can resist to storm and tsunami, protect the life and property of coast residents, maintain biodiversity and clean marine environment, and mitigate the global warming trend. Leaf traits can reflect the plants to response and adapt the condition of habitat, reflect the plant’s survival strategy, and leaf traits often correlate with each other. This paper studies the elements content of 11 mangrove species in Beihai, Guangxi and leaf traits of 9 species in Hainan, and we want to reveal the physiological and ecological adaptability of these mangrove species. These can be a reference to the study of the resistance to salinity of plants and the conservation of mangroves. The main findings are summarized below:1. The average of leaf mass per area of 9 mangrove species in Wenchang Hainan is 112 g·m-2, which is smaller than that in a global scale(127.7 g·m-2), and the average of net photosynthetic rate per leaf area (15.85 μmol·m-2·s-1) is similar to the average of global scale, and the average of dark respiration rate (0.95 μmol·m-2·s-1) is less than the global scale(1.24 μmol·m-2·s-1). This reveals the greater carbon assimilation efficiency of the mangrove plants.2. The mangrove plants in Wenchang, Hainan have a lower nitrogen content but a higher phosphorus content than many terrestrial plants, its N/P is less than 14, indicating N limitation in these mangrove habitats. The relative higher foliar P is helpful to reduce dark respiration.3. The characteristics of foliar element content of mangrove species in Beihai is the type of N> Na> Ca> K, all of which are more than 10 g·kg-1. The foliar concentration of element varies large across species,3 times variation in the macro-elements, while 25 times in average in micro-elements. There are a big difference in element concentrations between salt-secrete and non-salt-secrete mangrove species. The true mangrove species have higher concentrations of macro-elements but lower micro-elements compared to semi-mangrove species.4. Foliar K/Na and Ca/Na shows the ability of plant to select the kinds of ions for transportation. If these ratios are high, the plants will have a strong capability to resist salt ions from transporting into the plants above-ground. The mangrove species of the present study have higher ratios of K/Na and Ca/Na, being 4.2 in K/Na and 3.0 in Ca/Na in average.