不同退化程度高寒草地土壤碳氮磷含量及生态化学计量特征

Contents and eco⁃stoichiometric characteristics of soil carbon,nitrogen,and phosphorus in alpine grass⁃lands with different degradation degrees

以未退化(ND)、轻度退化(LD)、中度退化(MD)和重度退化(SD)高寒草地为研究对象,调查土壤有机碳(SOC)、氮(N)、磷(P)、碳氮比(C∶N)、碳磷比(C∶P)和氮磷比(N∶P),明确不同退化程度高寒草地土壤碳氮磷含量及生态化学计量特征。结果表明:土壤SOC、N、P含量均随退化程度的加剧呈下降趋势;C∶N、C∶P和N∶P均随退化程度加剧呈“N”字型的变化,C∶N、C∶P和N∶P的平均值均小于全球水平;相关分析表明,土壤SOC、N、C∶P、N∶P与土壤pH、土壤容重显著负相关(P<0.05),而土壤SOC、N、P、C∶P、N∶P与土壤含水率呈显著正相关(P<0.05),土壤P与土壤容重相关性不显著(P>0.05);土壤C∶N与土壤pH和容重呈显著正相关(P<0.01),而与土壤含水率呈显著负相关(P<0.01);结构方程模型进一步表明,草地退化直接影响土壤理化性质,进而影响土壤SOC、N、P含量及其生态化学计量比。综上,草地退化通过降低土壤含水率,增加pH和容重改变了土壤微环境,导致SOC、N、P含量下降。

To clarify the contents and ecological stoichiometric characteristics of soil carbon(C),nitrogen(N),and phosphorus(P)in alpine grasslands under different degradation degrees,we analyzed soil organic C(SOC),N,P,C∶N,C∶P and N∶P in undegraded(ND),lightly degraded(LD),moderately degraded(MD)and severely degraded(SD)alpine grasslands.The results showed that soil SOC,N,and P contents showed a decreasing trend with increasing degradation degree of grasslands.The average values of C∶N,C∶P,and N∶P were lower than the global level,all of which showed N-shaped changes with increasing degradation degree.Soil SOC,N,C∶P,N∶P,and N∶P were negatively correlated with soil pH and bulk density(P<0.05).Soil SOC,N,P,C∶P,and N∶P were positively correlated with soil water content(P<0.05).Soil P was not significantly correlated with soil bulk density(P>0.05).Soil C∶N was positively correlated with soil pH and bulk density(P<0.01),and negatively correlated with soil water content(P<0.01).Results of structural equation modeling indicated that grassland degradation directly affected soil physicochemical properties and thus soil SOC,N,and P content and their eco-stoichiometric ratio.In summary,grassland degradation changed soil microenvironment by reducing soil water content and increasing pH and bulk density,resulting in decreases in the contents of SOC,N,and P.