滇东石漠化坡地不同恢复模式下云南松林土壤碳氮磷化学计量特征及其影响因子

Stoichiometric characteristics and influencing factors of soil C,N and P in Pinus yunnanensis forests under different restoration modes on rocky desertification slope land in eastern Yunnan

【目的】研究不同植被恢复模式下云南松Pinus yunnanensis林土壤碳、氮、磷化学计量特征,为喀斯特石漠化区植被恢复和土壤肥力提高提供依据。【方法】在滇东石漠化区选取云南松纯林、云南松人工混交林、云南松天然次生林为研究对象,测定各样地0~10、10~20、20~40、40~60 cm土层土壤的碳、氮、磷质量分数,计算其化学计量比并用冗余分析工具分析土壤化学计量特征的影响因子。【结果】滇东喀斯特区云南松林土壤碳、氮、磷质量分数均值分别为2.94、0.26、0.46 g·kg^(-1),呈低碳低氮格局。云南松天然次生林的土壤有机碳质量分数显著高于人工混交林和纯林(P<0.05),人工混交林土壤氮和磷质量分数最为丰富,土壤磷质量分数差异不显著(P>0.05);天然次生林土壤有机碳质量分数随土层加深递增,人工混交林和纯林土壤碳、氮质量分数在土层0~10 cm达最大,呈表聚性,土壤磷质量分数在云南松林不同土层中变异较小。云南松林土壤碳氮比、氮磷比和碳磷比均值分别为11.43、0.59和4.53,天然次生林土壤的碳氮比和碳磷比显著高于纯林和人工混交林(P<0.05),纯林土壤氮磷比最大,3种云南松林下土壤氮磷比小于14,凋落物氮磷比小于25,土壤氮缺乏且凋落物分解也受氮元素限制,其中天然次生林土壤氮最缺乏;人工混交林和纯林土壤碳氮比随土层加深递减,3种云南松林土壤氮磷比和碳磷比随土层加深递减。研究区土壤碳、氮、磷化学计量特征受凋落物碳氮比和土壤大团聚体、容重、孔隙度、根长密度等环境因素的影响。【结论】滇东云南松林土壤呈低碳低氮格局,主要受氮元素限制,建议云南松林恢复时用混交林代替纯林,并针对元素限制性的植被施肥。图4表3参33。

[Objective]The objective is to study the stoichiometric characteristics of soil carbon(C),nitrogen(N)and phosphorus(P)of Pinus yunnanensis under different vegetation restoration modes,so as to provide the basis for vegetation restoration and fertility improvement in karst rocky desertification areas.[Method]Pure forest,artificial mixed forest and natural secondary forest of P.yunnanensis were selected as research objects in the rocky desertification area of eastern Yunnan.The contents of C,N and P in 0−10,10−20,20−40 and 40−60 cm soil layers of various plots were measured,the stoichiometric ratio was calculated and the influencing factors of soil stoichiometric characteristics were analyzed with redundancy analysis tools.[Result]The average contents of soil C,N and P of P.yunnanensis vegetation were 2.94,0.26 and 0.46 g·kg^(−1),showing a pattern of low C and low N.The soil organic C content in natural secondary forest was significantly higher than that in artificial mixed forest and pure forest(P<0.05),and the artificial mixed forest had the richest soil N and P contents.There was no significant difference in soil P content(P>0.05).Soil organic C content in natural secondary forest increased with soil deepening,while soil C and N contents in artificial mixed forest and pure forest reached the maximum in 0−10 cm soil layer,showing a surface aggregation.The soil P content had little variation in different soil layers of P.yunnanensis.The mean values of soil C/N,N/P and C/P in P.yunnanensis vegetation were 11.43,0.59 and 4.53,and the values of soil C/N and C/P in natural secondary forest were significantly higher than those in pure forest and artificial mixed forest(P<0.05).The soil N/P ratio in pure forest was the greatest.In the 3 P.yunnanensis vegetation types,the soil N/P ratio was less than 14 and the litter N/P ratio was less than 25,so soil N was deficient and litter decomposition was also limited by N.The natural secondary forest was the most deficient in soil N.With the deepening of soil,the soil C/N ratio in artificial mixed forest and pure forest decreased,so did the soil N/P ratio and C/P ratio of the 3 P.yunnanensis vegetation.The stoichiometric characteristics of soil C,N and P in the study area were affected by the litter C/N ratio,soil macroaggregates,bulk density,porosity,root length density and other environmental factors.[Conclusion]The vegetation soil of P.yunnanensis in eastern Yunnan presents a pattern of low C and low N,which is mainly limited by N elements.It is suggested that mixed forest should be used instead of pure forest in vegetation restoration of P.yunnanensis,and fertilization should be applied to vegetation with limited elements.[Ch,4 fig.3 tab.33 ref.]