林分密度对北京石质山地侧柏人工林碳氮磷化学计量和养分再吸收的影响

Effects of stand density on carbon,nitrogen,and phosphorus stoichiometry and nutrient resorption of Platycladus orientalis plantations in rocky mountainous area of Beijing

【目的】探讨北京石质山地不同林分密度对侧柏人工林C、N、P化学计量特征的影响,以及养分再吸收与林分密度的关系,旨在揭示林分密度变化下侧柏人工林主要养分相互作用与制约规律,为侧柏人工林经营管理提供科学依据。【方法】以不同密度侧柏人工林为研究对象,分析其鲜叶、凋落叶和土壤C、N、P化学计量特征及养分再吸收规律。【结果】(1)林分密度对土壤–鲜叶–凋落叶C、N、P化学计量影响不同,鲜叶N、P和N:P以及凋落叶P含量随着密度的增加逐渐降低,而鲜叶C∶N和C∶P总体呈升高趋势。凋落叶C∶N和C∶P随着密度的增大呈升高。(2)土壤的N和P含量随密度先升后降;林分密度和土壤因素的交互作用仅对鲜叶N和凋落叶P有显著影响;(3)不同林分密度的侧柏林N再吸收率明显低于P再吸收率,N再吸收率为18.03%~32.15%,P再吸收率为58.87%~60.13%。【结论】合理的林分密度能缓解侧柏人工林养分限制以及提高N、P重吸收能力。未来应注重林分密度调整、增加阔叶树种比例、实施抚育剩余物处理等措施以改善侧柏人工林养分限制状况。

[Objective]This study was conducted to analyze the dynamics of carbon(C),nitrogen(N),and phosphorus(P),and their stoichiometric characteristics and nutrient resorption of Platycladus orientalis plantations in rocky mountainous area of Beijing.Studies on these relationships provided insights into interactions on nutrient cycling and nutrient use strategies for resource acquisition and mass partitioning.[Method]Four stand densities were taken as research objects,the contents and stoichiometric characteristics of C,N and P in fresh leaves,litter leaves and soil were determined,the N and P resorption efficiency was calculated and also their relationships with leaf and soil nutrient indices were analyzed.[Result](1)The forest stand density had different effects on stoichiometry of soil leaf litter C,N,and P,with leaf N and P,fresh leaf N∶P,while fresh leaf C∶N and C∶P showing an overall upward trend.The C∶N and C∶P of fallen leaves showed an increasing trend with increasing density.(2)The N and P contents of soil first increased and then decreased with density;the interaction between density and soil factors only had a significant impact on fresh leaf N and litter leaf P.(3)The resorption rate of N in Platycladus orientalis plantations with different stand densities was significantly lower than that of P,with N resorption rates ranging from 18.03%to 32.15%and P resorption rates ranging from 58.87%to 60.13%.[Conclusion]Reasonable stand density can alleviate nutrient limitations and improve N and P resorption capacity in artificial forests of Platycladus orientalis in rocky mountainous area of Beijing,and measures such as increasing stand density adjustment,increasing proportion of broadleaved tree species,and implementing nurturing residues should be taken to improve nutrient limitations in plantation tending management based on local conditions.