贺兰山不同海拔植物养分含量及化学计量特征

Nutrient Composition and Stoichiometric Characteristics of Plant Species Across Different Altitudes in Helan Mountains

[目的]探讨干旱区脆弱森林生态系统不同海拔梯度植物养分含量及生态化学计量特征,为脆弱生态系统植物树种的养分管理工作提供科学支持。[方法]以贺兰山国家自然保护区5个不同海拔梯度(1730,1799,2025,2487,2544 m)的不同优势植物种为研究对象,分析其叶片、细根与土壤C,N,P及化学计量特征沿海拔梯度的变化特征及相关关系。[结果](1)土壤有机碳(SOC)含量随海拔升高呈“单峰”变化趋势,于2487 m处达到峰值(42.92 g/kg),土壤全氮(TN)含量高海拔(2025,2487,2544 m)显著大于中低海拔(1730,1799 m),而全磷(TP)无明显变化。C∶P和N∶P随海拔梯度上升呈先增加后减小趋势。(2)植物叶片与细根C随海拔无显著变化,P含量随海拔的升高而增加。细根N含量随海拔上升逐渐降低,而叶片N含量呈波动变化趋势。高海拔区植物叶片与细根N∶P<14,低海拔区N∶P>16。(3)植物叶片N,P含量显著高于细根;(4)相关性分析结果显示:植物叶片C含量与SOC,TN,C∶P,N∶P呈正相关关系,叶片N含量与细根N含量随着SOC,TN,C∶P,N∶P含量的升高显著降低,叶片、细根P含量与土壤TP含量相关性不显著。[结论]高海拔区植物生长受N限制,低海拔区植物生长受P限制,不同海拔优势植物叶片相比细根具有更高的养分含量,而海拔引起的土壤养分供应的差异调节贺兰山植物叶片与细根的氮、磷及化学计量特征。

[Objective] The nutrient content and ecological stoichiometric characteristics of plants across various altitudinal gradients in fragile forest ecosystems in arid regions were analysed in order to provide scientific support for their nutrient management.[Methods] This study focused on the dominant plant species at five distinct altitudinal intervals,i.e.1 730,1 799,2 025,2 487,and 2 544 m in the Helan Mountains National Nature Reserve.The variations and correlations of carbon(C),nitrogen(N),and phosphorus(P) contents and stoichiometric features in leaves,fine roots,and soil along these gradients were analysed.[Results](1) Soil organic carbon(SOC) displayed a unimodal pattern with altitude,peaking at 2 487 m(42.92 g/kg).Soil total nitrogen(TN) levels at the three highest altitude sites(2 025,2 487,2 544 m) were significantly greater than those at the two lowest altitudes(1 730,1 799 m),whereas total phosphorus(TP) remained relatively stable.The C∶P and N∶P initially increased and then decreased with increasing altitude.(2) There was no significant change in leaf and fine root C across altitudes,but the P content increased with altitude.Fine root N content progressively declined with altitude,whereas leaf N exhibited a fluctuating trend.At high altitudes,the N∶P ratio in the leaves and fine roots was less than 14;however,at low altitudes,the ratio exceeded 16.(3) Nutrient concentrations in the leaves were significantly higher than those in the fine roots.(4) Correlation analyses revealed that C content in leaf positively correlated with SOC,TN,C∶P and N∶P in soil.In contrast,N content in leaf and fine root significantly decreased as SOC,TN,C∶P and N∶P in soil increased,and the relationship between leaf and fine root P and soil TP was not significant.[Conclusion] Plant growth at high and low altitudes is mainly limited by N and P,respectively.Leaves of dominant plant species at different altitudes exhibit higher nutrient contents than their fine roots,and variations in soil nutrient supply due to altitude influence the N,P and stoichiometric characteristics of plants in the Helan Mountains.