连作对欧美杨I-107叶片主要养分元素化学计量特征的影响

The Effects of Continuous Cropping on Major Nutrient Elements and C/N/P Stoichiometric Ratios of Leaf of Populus × euramericana ‘Neva'

【目的】以期为合理经营连作欧美杨I-107人工林提供理论依据。【方法】以大汶河流域欧美杨I-107人工林为研究对象,分析一代、二代、三代连作欧美杨I-107人工林成熟叶和凋落叶主要养分元素含量计量特征。【结果】三代(连作2代)林成熟叶片的P和K含量显著低于一代林和二代林(连作1代)(P<0.05),但一代林和二代林之间差异不显著,且连作对N素含量影响较小;连作增加了凋落叶中N,P,K含量,特别是三代林,进而导致三代林叶片N,P,K的回收率显著低于一代林和二代林(P<0.05);此外,K的回收率显著大于N和P回收率;凋落叶中的C/N、C/P、N/P化学计量比普遍高于成熟叶;三代林成熟叶片的N/P和C/P显著高于其他2种林分,但3种林分成熟叶片中C/N差异不显著;随着连作代数增加,凋落叶片中的C,N,P化学计量比没有一致的变化规律,一代林凋落叶中N/P和C/P显著高于其他2种林分(P<0.05),而二代林凋落叶中的C/N显著高于其他2种林分。【结论】总体而言,连作会降低成熟叶片P和K含量,增加凋落物中N,P,K含量,同时降低欧美杨I-107养分回收率,影响养分内循环。此外,连作能通过降低凋落叶中N/P和C/P,降低欧美杨I-107凋落物的分解速率,影响土壤C,N,P含量的变化。

[ Objective ] The objective of this study was to provide theoretical basis for reasonable management of Populus x euramericana ＇ Neva＇ plantations under different continuous cropping conditions. [ Method] An Populus x euramericana ＇ Neva＇ plantation along Dawen River area was studied. The contents of major nutrient elements in leaves were measured. The variations of stoichiometric ratios and nutrient recovery under different continuous cropping conditions were analyzed. [ Result ] P and K contents in mature leaves of third generation plantation were significantly lower than those of first and second generations （ P 〈 0.05 ） , while the content differences were not significant between the first and second generations （ P 〉 0.05 ） , respectively. The effect of continuous cropping on N content was minor. Meanwhile, N, P, and K contents in leaf litters increased due to continuous cropping, especially for those in the third generation plantation. As a result, the recovery rates of N, P, and K in the third generation were significantly lower than those in the first and the second generations （ P 〈 0.05 ） , respectively. Moreover, the recovery rate of K was significantly higher than those of N and P （P 〈 0.05 ） , respectively. The stoichiometric ratios of C/N, C/P, and N/P in leaf litters were generally higher than those in mature leaves, respectively. The ratios of N/P and C/P in mature leaves of the third-generation plantation were obviously higher than those of the first and the second generations, however, there were no significant differences among C/N ratios in mature leaves of three generation plantations. With the increase of continuous cropping generations, no obvious variation trend was observed on stoichiometric ratios of C,N, and P in leaf litters. The ratios of N/P and C/P in leaf litters of the first generation were significantly higher than those of the second and the third generations （ P 〈 0.05 ） , respectively, while the C/N ratio of the second generation was significantly higher than those of the first and the third generations （ P 〈 0.05 ）. [ Conclusion ] Overall, continuous cropping could reduce the contents of P and K in mature leaves, increase N, P, and K contents in leaf litters, and reduce the nutrient recovery ratio of Populus x euramericana ＇ Neva＇ The internal circle of nutrients was therefore influenced. In addition, continuous cropping could reduce the decomposition rate of litters and affect the variations of C, N, and P contents in the soil by reducing N/P and C/P ratios in leaf litters.