Abstract: To reveal the spatialtemporal pattern and source of soil available phosphorus (AP) across a subtropical tidal marsh, soil AP, total phosphorus (TP), organic phosphorus (Org-P) and inorganic phosphorus (IP) speciation along a hydrological gradient were examined in Minjiang River estuary of eastern China in May, August and November, 2013. The mean concentrations of soil AP in May (3.53±1.15 mg·kg^-1) and August (3.23±1.15 mg·kg^-1) were significantly higher than that in November (1.96±1.07 mg·kg^-1) (P<0.05). The distribution patterns of soil AP in the three periods were similar, which showed a fluctuant decrease from high tidal marsh to middle tidal marsh and the higher value was observed in Phragmites australis soil compared with that in Cyperus malaccensis soil (P<0.05). Additionally, we observed that soil AP decreased with soil depth in high tidal marsh, while it slightly changed with soil depth in middle tidal marsh. Org-P, iron bound phosphorus (Fe-P) and occluded phosphorus (O-P) were considered as main sources of soil AP in the different vegetation growth periods.

Key words: phenotypic plasticity, dryland wheat, physiological plasticity, artificial selection, evolution