Temporal And Spatial Variation Of Soil Organic Phosphorus Form At The Lake Entrance Of Xiuhe And Ganjiang River

Soil organic phosphorus is an important component of soil phosphorus.This paper takes the soil of the Xiuhe and Ganjiang river entering the mouth of the lake as the research object.To explore the spatial and temporal distribution characteristics of organic phosphorus forms in different sampling times,different flooding conditions,different soil layers and different watersheds,and to explore the effects of soil physical and chemical properties,soil microbial phosphorus and enzymatic activities on the changes of organic phosphorus forms,The adsorption and desorption characteristics of the soil in the sampling point were studied in order to provide a reference for the eutrophication control of the lake.The results show that:(1)The contents of various organic phosphorus forms in the estuaries of Ganjiang and Xiuhe lakes showed the law of medium active organic phosphorus >medium stable organic phosphorus > high stable organic phosphorus > active organic phosphorus in different time and space.The content of organic phosphorus in different soil layers were significant and decreased with the deeping of soil layers.The annual mean proportions of soil active and medium active organic phosphorus at the mouth of Ganjiang river and Xiuhe were 63.93% and 69.19% respectively.These organic phosphorus were easily decomposed and unstable,indicating the risk of phosphorus release in the lake area.(2)The soil TP content of the two lake entrances and the OM content of the Xiuhe lake entrance soil showed the law of semi-flooded soil > flooded soil > unflooded soil.The effects of soil physical and chemical properties on organic phosphorus forms in the two lake estuaries were different in dry season and wet season.On the whole,the p H of the two lake estuaries was negatively correlated with the contents of the four forms of organic phosphorus in both dry and wet periods;TP was positively correlated with the four forms of organic phosphorus in the dry and wet periods of the Xiuhe estuary;OM and water content had different effects on the forms of organic phosphorus in the two watersheds.(3)The activities of soil catalase,sucrase,alkaline phosphatase and microbial phosphorus in Xiuhe estuary and Ganjiang river decreased significantly with the deeping of soil layers,and the activities of soil catalase and sucrase in September wet season were higher than those in March dry season,but alkaline phosphatase and microbial phosphorus were opposite.The changes of soil protease activity in each soil layer were not consistent.The correlation between soil enzymatic activities and physical and chemical properties and organic phosphorus forms were different.(4)The adsorption parameters K and MBC were positively correlated with water content,and positively correlated with OM and TP.The flooded soil(GJ),semiflooded soil(GJ、XH)in dry season and unflooded soil(GJ、XH)in wet season have strong phosphorus adsorption capacity.The desorption of the unflooded soil of Ganjiang river and the flooded soil of Xiuhe in dry season,and the semi-flooded soil of Ganjiang river and Xiuhe in wet season were easy.In the management of the eutrophication of Ganjiang river and Xiuhe,the risk of soil phosphorus release should be emphasized.