贺兰山中段不同海拔青海云杉林非根和根围土壤生态化学计量特征及影响因素

Soil ecological stoichiometric and its influencing factors of bulk soil and ectorhizosphere soil in Picea crassifolia forest along an elevation gradient in the middle of Helan Mountains

面对全球变化,准确掌握陆地森林生态系统生物地球化学循环过程及其影响因素,有助于维持生态系统多功能性与稳定性,实现增汇并延长碳汇服务,持续增进并改善人民福祉。为了探究贺兰山山地森林生态系统优势建群种青海云杉(Picea crassifolia)林土壤生态化学计量特征对海拔的生态响应及其影响因素,从土壤、林分、地形影响因素的角度出发,采用冗余分析(Redundancy analysis,RDA)和方差分解分析(Variance partitioning analysis,VPA)阐明影响其非根和根围土壤生态化学计量特征空间变异的关键因素。结果表明:(1)贺兰山青海云杉林非根和根围土壤C、N养分含量均维持在较高水平,高海拔区域青海云杉生长受土壤P限制高;相较非根土壤,根围土壤虽养分含量较低,但具有较高的养分周转能力,如有机质分解与矿化、固持P的潜力等。(2)随海拔变化,非根和根围土壤养分及其生态化学计量比变化趋势不同,非根土除了全氮(TN)含量外其他养分含量及化学计量比在不同海拔间均差异显著(P<0.05),根围土全磷(TP)、碳磷比(C/P)具有显著性差异(P>0.05)。(3)土壤、林分、地形3组影响因子共同累计解释了非根和根围土壤养分计量特征61.35%、39.64%的变异;海拔、微生物量碳(MBC)和微生物量磷(MBP)是影响青海云杉林非根土壤养分计量垂直分异的主导因子,而归一化植被指数(NDVI)则显著影响其根围土壤养分计量空间特征;土壤因子对非根和根围土壤生态化学计量特征的单独作用分别是林分因子的2倍、3倍。综上所述,贺兰山青海云杉林非根和根围土壤养分及其生态化学计量特征的空间异质性主要受到土壤因子的驱动,林分因子次之,地形因子的作用主要通过对环境因子的再分配改变植被、土壤性质等特征进而影响土壤生态化学计量的空间格局。本研究有助于科学评估山地生态系统土壤养分盈亏状况及其关键的影响因素,以期从生态化学计量角度为林地土壤养分调控与可持续经营管理提供科学依据和理论支持。

In the face of global climate change,an accurate grasp of the biogeochemical cycling process and its key influencing factors in terrestrial forest ecosystems is beneficial for maintaining the multifunctionality and the stability of the ecosystem,achieving increased and extended carbon sink services,and continuously enhancing and improving people′s well-being.Redundancy analysis(RDA)and Variance partitioning analysis(VPA)were used to clarify the key factors affecting the spatial variation of the stoichiometric characteristics of bulk soil and ectorhizosphere soil of the Picea crassifolia forest from the perspective of soil,forest stand and topography in this study,in order to explore the influencing factors and the ecological response of soil ecostoichiometric characteristics to the altitude of the forest of P.crassifolia,which is the constructive species in the forest ecosystem of Helan Mountains.The results of experiment showed that:(1)the contents of C and N nutrients in bulk soil and ectorhizosphere soil of P.crassifolia forest in Helan Mountains were remained at a high level,while the growth of P.crassifolia in the high-altitude areas was affected by the high P limit of soil.Compared with the bulk soil of P.crassifolia forest,the ectorhizosphere soil has higher capacity of nutrient turnover,such as the decomposition and mineralization of organic matter,and the potential of P retention,although the nutrient content of ectorhizosphere soil was relatively lower.(2)there were significant differences in bulk soil and ectorhizosphere soil ecostoichiometric characteristics of P.crassifolia forest between different altitudes(P<0.05).With the increase of altitude,the bulk soil and ectorhizosphere soil nutrients and ecostoichiometric ratios changed differently,and all soil nutrient contents and ecostoichiometric ratios of bulk soil were significantly different between different altitudes except total nitrogen content(TN)(P<0.05),and total phosphorus(TP)and C/P ratio(C/P)had significant differences of ectorhizosphere soil(P<0.05).(3)three groups of influencing factors,i.e.the soil,forest stand,and topography,together accounted for 61.35%and 39.64%of the variation of the ecostoichiometric characteristics of bulk soil and ectorhizosphere soil,respectively.It was found that altitude,microbial biomass carbon(MBC),and microbial biomass phosphorus(MBP)were the dominant factors affecting the vertical variation of the ecostoichiometric characteristics of bulk soil,while those of ectorhizosphere soil were significantly affected by the normalized difference vegetation index(NDVI).The single effect of soil factors on the ecostoichiometric characteristics of bulk soil and ectorrhizosphere soil was twice and three times as great as that of forest stand factors,respectively.In summary,the spatial heterogeneity of the ecostoichiometric characteristics of bulk soil and ectorhizosphere soil in P.crassifolia forest in Helan Mountains was mainly driven by soil factors,secondly by forest stand factors.The effect of topographic factors was to change vegetation characteristic and soil properties mainly through the redistribution of environmental factors,so as to affect the spatial pattern of soil nutrient stoichiometry in P.crassifolia forest.This study is helpful to evaluate the soil nutrient deficit status and key influencing factors in mountain ecosystems,and is also beneficial for providing a scientific basis and theoretical support for soil nutrient regulation and sustainable management in the forest land from the perspective of ecological stoichiometry.