湿地退化条件下土壤碳氮磷储量与生态化学计量变化特征

Ecological Stoichiometry Characteristics and Storage of Soil Carbon,Nitrogen and Phosphorus During the Wetland Degradation Process

为了研究湿地退化过程中土壤碳氮磷储量与生态化学计量变化,明确碳氮"汇"功能的变化和土壤碳、氮、磷的平衡关系,采用实地采样调查、室内分析与数理统计法,研究了若尔盖自然湿地保护区内未退化湿地沼泽(MA)、沼泽化草甸(MM)、草甸(ME)3种不同退化程度湿地的典型样地在碳氮磷含量、储量以及生态化学计量的变化特征。结果表明,草甸化沼泽土与草甸土全剖面总有机碳、全氮含量较沼泽土分别降低了29.55%,6.52%和67.53%,40.04%,碳氮储量分别降低了67.49%,60.10%和85.14%,54.47%;3种土壤全磷剖面含量大小顺序为MM>ME>MA,其储量高低顺序是ME>MA>MM。随着土层深度的增加,沼泽土的总有机碳、全氮含量明显升高,全磷含量与草甸化沼泽土、草甸土的总有机碳、全氮、全磷含量均呈现降低趋势;3种土壤碳氮磷储量40—100cm土层高于0—40cm土层。沼泽土、草甸化沼泽土、草甸土3种不同类型土壤C/N分别为40.38,31.70,23.26,C/P分别为409.52,247.46,113.07,N/P分别为10.43,7.90,5.02,土壤C/N、C/P、N/P均随湿地退化而减小,较高的C/P与N/P<14揭示氮磷元素均是影响植物生长的限制性因素,且受氮素限制高于磷素。因此,若尔盖湿地退化导致土壤碳氮含量与储量降低,碳氮"汇"功能减弱,尤其是碳"汇"。

The aims of this study were to investigate the ecological stoichiometry characteristics during the process of wetland degradation,and clarify the relationship between the changes in C and N sink function of the soil and the balance in soil C,N and P.Soil C,N and P concentrations,storages and ecological stoichiometry in three kinds of wetland landscape with different degrees of degradation,i.e.marsh（MA）,marsh meadow（MM）and meadow（ME）in the Zoige Wetland Nature Reserve,were studied by means of field investigation,laboratory analysis,and mathematical statistics.Compared with MA soil,total organic C and N concentrations in the whole soil profiles decreased by 29.55% and 6.52%in MM soil,and by 67.53% and 40.04%in ME soil;storages of C and N decreased by 67.49%and 60.10%in MM soil,and by 85.14%and 54.47%in ME soil,respectively.Total P concentration in the soil followed the order of MM〉ME〉MA,and P storage in the soil followed the order of ME〉MA〉MM.Both total organic C and N concentrations in the soil of MA increased obviously with increasing soil depth,while the concentrations of total organic C,N and P in the MM and ME soil decreased with increasing soil depth.For all three types of soil,C,N and P storages in the40—100cm layers were generally higher than those in the 0—40cm layers.For the soil in the MA,MM and ME,C/N was 40.38,31.70 and 23.26,while C/P was 409.52,247.46 and 113.07,and N/P was 10.43,7.90 and 5.02,respectively,with C/N,C/P and N/P declining as the wetland degradation became intensified.When C/P is high and N/P is〈14,both N and P are limiting factors for plant growth,and N is more limiting than P.In conclusion,degradation of the Zoige Wetland has led to decreased concentrations and storages of C and N in the soil,and the C and N sink function of the soil,in particular the C sink function,has been weakened during the wetland degradation process.