闽江河口互花米草不同入侵年限湿地土壤磷赋存形态

Phosphorus forms in marsh soils with different years of Spartina alterniflora invasion in the Minjiang River estuary, China

选择闽江河口鳝鱼滩互花米草不同入侵年限湿地(SA_(1),5~6年;SA_(2),8~10年;SA_(3),12~14年)为对象,基于时空互代法研究了互花米草入侵对湿地土壤磷赋存形态的影响。结果表明:不同入侵年限互花米草湿地土壤中难分解态磷(HCl-Pi、Residual-P)含量的占比最高(46.4%~46.7%),中等易分解态磷(NaOH-Pi、NaOH-Po、Sonic-Pi)次之(40.0%~44.0%),而易分解态磷(Resin-Pi、NaHCO_(3)-Pi、NaHCO_(3)-Po)最低(9.5%~13.3%)。随着互花米草入侵年限的增加,湿地土壤磷赋存形态及其空间分布特征也发生明显改变,中等易分解态磷、难分解态磷和总磷含量整体上均呈增加趋势,而易分解态磷含量呈降低趋势。相对于SA_(1),SA_(2)的中等易分解态磷、难分解态磷和总磷含量分别增加了11.5%、9.7%和10.5%,而SA_(3)分别增加了24.8%、13.2%和13.5%。互花米草入侵年限的增加显著改变了湿地土壤磷的赋存形态特征,这主要取决于电导率(EC)、pH值及粒度等关键因子的变化。近年来,闽江河口开展的互花米草定期刈割治理在一定程度上减少了残体向土壤归还磷养分的能力,降低了土壤中易分解态磷的养分供应。

We examined the effects of Spartina alterniflora invasion on phosphorus forms of marsh soils,based on the method of space-for-time substitution by selecting S.alterniflora marshes with different invasion years(SA_(1),5-6 years;SA_(2),8-10 years;and SA_(3),12-14 years)in Shanyutan of the Minjiang River estuary.The results showed that in marsh soils of different invasion years,the proportion of hardly decomposable phosphorus(HCl-Pi and Residual-P)was the highest(46.4%-46.7%),followed by moderately decomposable phosphorus(NaOH-Pi,NaOH-Po and Sonic-Pi)(40.0%-44.0%),and the easily decomposable phosphorus(Resin-Pi,NaHCO_(3)-Pi and NaHCO_(3)-Po)was the lowest(9.5%-13.3%).With increasing invasion years of S.alterniflora,soil phosphorus forms and their spatial distributions were greatly altered.The contents of moderately decomposable phosphorus,hardly decomposable phosphorus,and total phosphorus(TP)generally increased,while easily decomposable phosphorus content generally decreased.Compared with SA_(1),the contents of moderately decomposable phosphorus,hardly decomposable phosphorus and TP in SA_(2) increased by 11.5%,9.7%and 10.5%,while those in SA_(3) increased by 24.8%,13.2%and 13.5%,respectively.The distribution of phosphorus forms was greatly altered with increasing invasion years,which was dependent on the variations of key factors such as EC,pH value and grain composition.The implementation of regular mowing activities for S.alterniflora in the Minjiang River estuary in recent years,to some extent,reduced the return of phosphorus from residues to soils and decreased the availability of the easily decomposable phosphorus in soils.