Nutritional ecology of plants grown in a tropical peat swamp

抄録

The relationships between plant and soil in peat swamp forests in two different growth stages, primary and secondary, were examined by analyzing nutritional characteristics (e.g. N, P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, Mo, Al, B, and Si concentrations) and natural abundances of ¹⁵N (δ¹⁵N) and ¹³C (δ¹³C) of plant and soils. Fifty-two plant species from primary forests and thirty from secondary forests were randomly sampled. Plants in both forests belonged to the phylogenic groups Euasterids II, Euasterids I, Ericales, Eurosids II, Eurosids I, Eudicots, and Magnoliids, which were from a newly evolved order. The results showed that Eurosids I plants in primary forests accumulated higher P, K, Mg, Fe, and B than those in secondary forests.
Other minerals did not limit plant growth at either forest type. For Eurosids I plants nutrients depended on soil K, Mg, and Fe, but for P and B they relied on their own nutrient acquisition. This is similar to other plant phylogenies in both forests whose nutrient contents reflected their own nutrient requirements rather than soil nutrients. Since the leaf δ ¹⁵N of plants in both forests is lower than soil δ ¹⁵N, N₂-fixing microorganism activity may be high. It can be hypothesized that peat swamp forests have developed symbiotic systems with N₂-fixing microorganisms, because of poor N nutrition.