Author(s): Junhong Bai; Wei Wang; Xiaofei Ye; Qiongqiong Lu; Guangliang Zhang; Baoshan Cui; Xinhui Liu
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Abstract: Soil samples to the depth of 40 cm were collected in tidal flooding and freshwater restoration wetlands of Yellow River Estuary of China in spring, summer and fall to investigate the effects of freshwater input on seasonal changes in depth distributions of organic and inorganic phosphorus fractions and potential bioavailability of phosphorus in salt marsh soils. Our results showed that inorganic phosphorus contents were significantly higher than organic phosphorus contents in both wetlands (p< 0.01). Freshwater restoration wetland (FRW) soils generally contained lower organic phosphorus (OP) levels than Tidal flow wetland (TFW) soils along soil profiles in three sampling seasons (p< 0.05). Higher OP levels occurred in upper soils in both wetlands and lower OP levels were observed in fall than those in spring and summer (p< 0.05). Higher IP levels, especially Ca-P contents, were observed in FRW soil profiles than TFW soil profiles in summer (p< 0.05). IP contents increased with depth along soil profiles in summer, whereas a decreasing tendency was observed in spring and fall. Generally, FRW soils contained higher IP in both summer and fall compared with spring (p< 0.05). However, FRW soils exhibited lower available phosphorus (AP) and potential bioavailable phosphorus (PBAP) levels than TFW soils (p< 0.05). Higher AP and PBAP levels were observed in spring compared with summer and fall (p< 0.05). Multivariate analysis showed that AP was significantly correlated with soil properties such as particlesize, Ca, Fe, Al0 and Ca0, whereas PBAP had a significant correlation with water content (WC), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN). Total phosphorus (TP) was only significantly affected by Clay and Al, and organic phosphorus (OP) exhibited a significant correlation with EC (Cl-), particle size, Al0 and Ca0, whereas only EC (Cl-) and Al were the main factors influencing IP contents in both wetlands.
Year: 2018