东祁连山高寒草甸土壤理化性质对海拔和坡向的响应及其与植被特征的关系

Response of soil physical and chemical properties to altitude and aspect of alpine meadow in the eastern Qilian Mountains and their relationships with vegetation characteristics

为了探索高寒草甸土壤理化性质对海拔和坡向的响应及其与植被的关系,以东祁连山高寒草甸为研究对象,分析了7个海拔和2个坡向高寒草甸的土壤养分含量和生态化学计量比变化规律及其与植被的关系。结果表明:(1)土壤含水量、电导率、有机碳、全氮、全钾、碱解氮、速效磷、速效钾含量、碳磷比(C/P)和氮磷比(N/P)随海拔的升高呈先升高后降低的趋势,土壤容重、全磷和碳氮比(C/N)呈先降低后升高的趋势。(2)同一海拔,大部分海拔梯度阳坡的土壤土壤容重、速效钾、电导率和全磷高于阴坡,阳坡的土壤含水量、速效磷、C/P和N/P低于阴坡,海拔3200 m梯度以下阳坡的土壤有机碳、全氮、碱解氮和C/N低于阴坡。(3)不同海拔和坡向的高寒草甸土壤C/N、C/P和N/P处于14.55~38.13、12.61~87.94和0.27~5.01之间。(4)冗余分析(RDA)发现,土壤容重、全氮和速效磷是影响高寒草甸植被的关键土壤因子,聚类分析发现海拔3200~3400 m的阴坡和阳坡聚为一类。综上所述,东祁连山高寒草甸土壤养分和生态化学计量比随海拔和坡向的变化呈规律性变化,基于对N/P比的分析发现,该区域高寒草甸类草原的初级生产力主要受土壤氮限制且低海拔和高海拔区域尤为明显,基于聚类分析发现,海拔3000 m和3400 m是该区域草地植被和土壤特征发生变化的临界线。建议在高寒草甸类草原的管理过程中,应该充分考虑海拔和坡向的分异性特征。

To investigate the response of physical and chemical properties of alpine meadow soil to altitude and their interconnection to vegetation characteristics,the alpine meadows in the eastern Qilian Mountain of China were chosen as the research object.The changes to seven altitudes and two soil nutrient content and ecological stoichiometric aspects in the alpine meadows and their interconnection with the vegetation were analyzed.The results demonstrated that(1)soil water content,electrical conductivity,soil organic carbon(SOC),total nitrogen(TN),total potassium(TK),alkali-hydrolyzable nitrogen(AN),available phosphorus(AP),and available potassium(AK)were affected.carbon-phosphorus ratio(C/P)and nitrogen-phosphorus ratio(N/P)appeared to increase first and then decreased with the increase in altitude.The soil bulk density,total phosphorus(TP),and carbon-nitrogen(C/N)decreased first and then increased.(2)At the same altitude,soil bulk density,AK,electrical conductivity,and TP were higher in the sunny aspect than in the shady aspect;soil moisture content,AP,C/P,and N/P were lower in the sunny aspect than in the shady aspect,and SOC,TN,AN,and C/N were lower in the sunny aspect under 3200 m than in the shady aspect.(3)The C/N,C/P,and N/P of the alpine meadow soils at different altitudes and aspects were between 14.55-38.13,12.61-87.94,and 0.27-5.01.(4)Redundancy analysis revealed that soil bulk density,TN,and AP are the most important soil factors influencing the vegetation of alpine meadows.Cluster analysis discovered that the shady and sunny aspects at an altitude of 3200-3400 m were clustered together.Finally,the physical and chemical properties of the soil and ecological stoichiometry of the alpine meadows in the eastern Qilian Mountains changed regularly with altitude and aspect differentiation.Based on the N/P rate,soil nitrogen was the main constraint to alpine meadow productivity,which was severe in low and highaltitude areas.Based on cluster analysis,3000 m and 3400 m were identified as the critical lines for change in vegetation and soil characteristics in this area,suggesting that altitude and aspect differentiation should be considered in alpine meadow management.