三江平原湿地土壤磷形态转化动态

采用Hedley连续浸提法对三江平原湿地小叶章草甸土壤磷形态的季节动态进行研究,分析生长季土壤磷形态之间的相互转化及其可能的驱动机制。结果表明:小叶章草甸土壤有机磷(TPo)总量高于无机磷(TPi),NaOH溶液浸提的无机磷(NaOH-Pi)和有机磷形态(NaOH-Po)分别占总无机磷(TPi)和总有机磷(TPo)比重最大。各无机磷形态均有明显的季节变化,Resin-P和Conc.HCl-Pi季节变异性大,生长结束后含量较初期降低,其他形态无机磷含量有不同程度的升高。有机磷组分中NaOH-Po的季节波动最明显,生长季末期较初期含量降低,其他有机磷形态和Residual-P生长季初、末期含量变化不大,波动也相对较小。TP、TPo季节变化整体趋势相似,二者含量变化达到极显著相关。各无机磷形态变化主要受植物生长节律影响;水分、热量等环境条件也是磷的形态转化的重要驱动因子,并可能间接通过影响土壤动物、微生物等的活性推动土壤磷的循环。小叶章草甸土壤有机磷矿化释放的无机磷通常都首先被土壤金属氧化物固定,再经过无机磷之间的转化过程为生物利用,因此三江平原湿地土壤磷大量释放的可能性很小。

Seasonal changes of soil phosphorus fractions under Calamagrostis angustifolia wetlands in Sanjiang Plain, China

The seasonal dynamics of soil P fractions was determined in the Sanjiang plain marshes.The soil samples were taken from a depression marsh once or twice every month during the growth season and soil P fractions were determined by the modified Hedley fraction method in 2005.The study showed that P was mainly organically bound in the Sanjiang Plain wetlands.NaOH extractable organic P(NaOH-Po)and inorganic P(NaOH-Pi)was the predominant form in total organic P(TPo)and total inorganic P(TPi);respectively.The content of Resin-P was highest at end of August and lowest at the early days of July,seasonal dynamic of NaHCO3-Pi and NaOH-Pi were similar to Resin-P.Dil.HCl-Pi and Conc.HCl-Pi had their highest and lowest value at the beginning of September and the initial stage of May.The variation coefficient of Resin-P and Conc.HCl-Pi were higher than other Pi fractions,the level of them decreased from the beginning of growth season to the end of growth season,while the other Pi fractions increased in some degree.For organic phosphorus(Po),the variation coefficient of NaOH-Po was highest in the Po fractions,and NaOH-Po content reduced in the end of the growth season,NaHCO3-Po,Conc.HCl-Po and Residual-P had no obvious changes during this time.The concentration of TP and TPo had significant correlation and the concentration of TP was similar to TPo.The dynamic of P fractions,especially inorganic P forms are intensively affected by the plants,the change of their value go with the absorbing intensity of plants,especially Resin-P.The transformation of phosphorus is directly promoted and also indirectly improved by environmental factors(e.g.water and temperature)with their effect on the biomass or activity of microorganism.The soil water content plays an important role in sorption and desorption of NaHCO3-Pi,NaOH-Pi from soil.The biomass or activity of microorganism usually influences mineralization of organic P.The Pi which is released from mineralization of Po is usually first absorbed by mineral oxide and then transform into other more active form for utilizing of plants or microbe.