太湖西部流域滨岸带土壤磷形态空间分布与影响因素比较

摘要

为了揭示不同流域滨岸带的生态功能,于2015年夏季采集太湖西部苕溪流域和天目湖流域不同滨岸带(林地、耕地、草地、荒地)土壤,利用连续顺序提取法获得无机磷形态,分析土壤磷形态的空间分布特征、影响因素以及土壤磷形态与地下水中TDP(总溶解性磷)的联系.结果表明:苕溪滨岸带的磷形态含量总体上高于天目湖滨岸带,但组成方面有所差异.滨岸带土壤的NH4Cl-P(弱吸附态磷)、BD-P (还原态磷)、NaOH-P(金属氧化物结合态磷)含量随土壤深度的增加而降低,HCl-P(钙结合态磷)含量随土壤深度的增加而增加,耕地表现得最为明显.从高地到滨水带,草地和荒地的磷形态含量有略微增加的趋势,而林地和耕地的磷形态含量均降低,耕地同样表现得最为明显.苕溪滨岸带磷形态含量的水平变幅大于天目湖滨岸带.相关性分析表明,土壤NaOH-P对地下水中TDP的贡献较大,有机质、黏土矿物和碳酸盐对磷形态有明显的影响;苕溪滨岸带土壤性质对其磷形态的影响较弱,而天目湖滨岸带比较明显.因此,苕溪和天目湖流域不同滨岸带土壤磷形态的空间分布存在差异,影响因素也不同;土壤磷形态与地下水中TDP有明显关系,尤其是NaOH-P.%In order to reveal the ecological functions of riparian zones in different watersheds, the soils in different riparian zones (woodland,cropland,grassland and wasteland) of Tiaoxi watershed and Tianmu Lake watershed in western Taihu Basin were collected and analyzed in the summer of 2015. Phosphorus fractions were obtained by a sequential extraction procedure. Spatial distributions of phosphorus fractions in soil profiles,influence factors and the relationships between phosphorus fractions in soils and the total dissolved phosphorus (TDP) in ground water were analyzed. The results showed that phosphorus fractions concentrations of riparian soils in Tiaoxi watershed were higher than those in Tianmu Lake watershed, but there were differences in compositions. Generally the loosely absorbed phosphorus (NH4Cl-P),reductant phosphorous(BD-P) and metal oxide bound phosphorus(NaOH-P) concentrations decreased with the increase of soil depth,while calcium bound phosphorus (HCl-P) concentrations increased with the increase of soil depth, and cropland showed the most obvious tendency in vertical direction.From upland to waterfront,phosphorus fractions concentrations in soils of grassland and wasteland profiles increased slightly,while those of woodland and cropland profiles decreased. Cropland also showed the most obvious tendency in horizontal direction. Overall,the horizontal changes of phosphorus fractions concentrations of soil profiles of Tiaoxi watershed were more obvious than those of Tianmu Lake watershed. The correlation analyses showed that NaOH-P contributed more to TDP in the ground water. Organic matter, clay mineral and carbonate showed stronger effects on phosphorus fractions than other soil properties.Phosphorus fractions in riparian soils of Tiaoxi watershed had weak relationships with the soil properties, while those of Tianmu Lake watershed had strong relationships with the soil properties. Therefore,there were differences in spatial distributions of phosphorus fractions in different riparian soils in Tiaoxi and Tianmu Lake watersheds and their influence factors were also different. There was a significant relationship between phosphorus fractions in soils and TDP in the ground water,especially NaOH-P.