盐分和淹水增加对河口潮汐淡水沼泽湿地土壤磷形态和磷酸酶活性的影响

选取中国东南沿海闽江河口潮汐淡水沼泽湿地土壤作为研究对象,研究不同盐分(淡水对照、低盐处理、高盐处理)和不同淹水(CK、CK+15 cm、CK+30 cm)交互处理对土壤磷形态和磷酸酶活性的影响.结果表明,在闽江河口潮汐淡水沼泽湿地土壤中,无机磷是土壤总磷的主要赋存形态,约占总磷含量的68%~82%,有机磷含量约占总磷的18%~32%.无机磷以铁铝结合态磷为主(60%~66%),其次为钙结合态磷和闭蓄态磷.淹水处理对磷的总量和形态的影响有限,盐分变化对磷的总量和形态影响显著.低盐处理可增加铁铝结合态磷、闭蓄态磷含量及碱性磷酸酶活性,而高盐处理则对它们表现出抑制作用.随着盐分的增加,土壤总磷含量逐渐降低,土壤中钙结合态磷含量和磷酸盐含量将逐渐升高.相关分析表明,有机磷含量与土壤碱性磷酸酶活性呈负相关,无机磷含量与土壤碱性磷酸酶活性呈正相关.当盐分由淡水变化至低盐时,土壤磷的形态主要由有机磷向无机磷转化;而当盐分由低盐变化至高盐时,无机磷占比降低,有机磷占比增加.研究结果表明,碱性磷酸酶活性在磷形态对盐分和淹水的响应中发挥着重要作用.

Effects of increasing salinity and flooding on soil phosphorus speciation and phosphorus-acquiring enzyme activities in the tidal freshwater wetland soils of the Min River Estuary, southeast China

In the present study, we established mesocosms loaded with soil from a tidal freshwater wetland of the Min River Estuary, southeast China, and subjected them to three salinity treatments (fresh control, oligohaline, mesohaline) and three flooding treatments (control, control+15 cm, control+30 cm) treatments. Thereafter, we simultaneously assessed the abundance and speciation of phosphorus (P) and P-acquiring enzyme activities. In general, the contents of organic P accounted for approximately 68%~82% of total P, whereas those of inorganic P accounted for approximately 18%~32% of total P. Moreover, iron/aluminum bound P (Fe/Al-P) was the main component (approximately 60%~66%) of inorganic P, followed by calcium bound P and occluded P. Salinity had remarkable impact on the abundance and speciation of P, whereas flooding treatments revealed limited effect. Oligohaline treatment increased the contents of Fe/Al-P and occluded P and alkaline phosphatase activities, whereas mesohaline treatment decreased these contents. As salinity increased, the total P contents and acid phosphatase activities decreased; however, the calcium bound P contents and porewater phosphate concentrations increased. This study revealed that organic and inorganic P contents exhibited negative and positive correlation with alkaline phosphatase activities, respectively. When the salinity changed from freshwater to oligohaline, few parts of organic P transformed into inorganic P. Furthermore, when the salinity changed from oligohaline to mesohaline, the importance of inorganic P decreased, whereas that of organic P increased. Thus, this study highlighted the importance of phosphorus-acquiring enzyme activities on the feedbacks of abundance and speciation of P toward increasing salinity and flooding in tidal freshwater wetland soils.