Phosphorus fractions and profile distribution in newly formed wetland soils along a salinity gradient in the Yellow River Delta in China

Soil P availability has been identified as one of the key factors controlling wetland productivity, structure, and function. Soil P fractions at different depths in newly formed wetlands along a salinity gradient in Yellow River Delta (China) were studied using a modified Hedley fraction method. The total P (P t ) content ranged from 471.1 to 694.9 mg kg –1 , and diluted HCl‐extractable inorganic P (Dil‐HCl‐P i ) ranged from 324 to 524.2 mg kg –1 . The Dil‐HCl‐P i is the predominant P form in all profiles, with on average 70% of the P t extracted as P i . Organic P (P o ) comprised (4.2 ± 2.0)% (mean ± SD) of the P t , due to low organic‐matter content in coastal salt marsh ecosystems. The labile P (resin‐P, NaHCO 3 ‐P i , and NaHCO 3 ‐P o ) and moderately labile P (NaOH‐P i and NaOH‐P o ) concentrations were both low, ranged from 11.6 to 38.1 and 2.8 to 21.3 mg kg –1 , respectively, constituting (3.7 ± 1.1)% and (2.0 ± 0.7)%, respectively, of P t , suggesting low availability of P to plants in these soils. Our results suggested that vegetation cover significantly influenced soil P dynamics and availability. In particular, the labile P content under Tamarix chinensis increased significantly by 23.2%–145.5% compared with adjacent soils. These findings have important implications for wetland conservation or restoration and long‐term sustainable management of newly formed wetland ecosystems in the Yellow River Delta.