马尾松人工林林龄对土壤和叶片养分含量的影响

探索不同林龄马尾松人工林土壤和针叶养分特征及其相关性，为马尾松人工林高效培育提供理论参考。采用时空互代法，以桂中不同林龄（4、9、15、19、22、30、56 a）马尾松人工林为对象，利用冗余分析和结构方程探讨马尾松人工林林龄对土壤和针叶养分含量的影响。结果表明，林龄对土壤和叶片养分均具有显著影响，随林龄的增加土壤pH呈先增后减趋势，中龄林中最大，有机碳、全N、全P、碱解N和速效态K、Ca、Mg、Zn和B含量呈先减后增的U形变化，中龄-成熟林阶段最小，全K和有效P含量呈W形变化；针叶养分含量随林龄增加呈波动性变化，C、N、P和K含量在过熟林中最大，Ca、Zn分别在中龄林、成熟林中含量最大，Mg和B均在幼龄林中最大。针叶K、Ca、Mg、Zn和B与土壤对应元素呈显著正相关，土壤有机碳、全N、有效P和速效K是影响马尾松叶片养分含量变化的敏感因素，土壤速效元素对叶片养分的正向效应显著，而土壤有机碳和全量养分的负向效应显著。综上，不同林龄阶段马尾松土壤和叶片养分存在显著差异，在马尾松15 a后，土壤和叶片养分均有所下降，尤其是受N素和微量元素限制，为此在马尾松中龄林后，建议施用N肥满足其健康生长，并辅以适量微量元素，以增强植物光合作用和蛋白质的合成及抗逆性。

Responses of Soil and Leaf Nutrients to Different Stand Ages in Pinus massoniana Plantation

The objectives of this study were to explore the characteristics and correlationships of soil and leaf nutrients of Pinus massoniana plantations with different ages,and to provide theoretical references for the efficient cultivation of P.massoniana plantations.Taking the P.massoniana plantations with different ages (4-,9-,15-,19-,22-,30-,and 56-year-old) in Guangxi as the research objects,redundancy analysis and structural equation were used to explore the influence of forest age on soil and leaf nutrients.The results showed that forest age had a significant effect on soil and leaf nutrients.Among them,with the increase of forest age,soil pH increased first and then decreased,the maximum value of pH was found in the middle-aged plantations.The contents of organic carbon,total nitrogen,total phosphorus,alkali-hydrolyzable N and available potassium,calcium,magnesium,zinc,and boron decreased first and then increased with U-shaped curves,and the minimum values were found in middle-aged-mature plantations.The contents of total potassium and available phosphorus showed W-shaped curves.The nutrient contents in the needles fluctuated with age,the contents of carbon,nitrogen,phosphorus and potassium were the largest in overmature plantations,calcium and zinc were the largest in middle-aged and mature plantations,respectively,and magnesium and boron were the largest in young plantations.Leaf potassium,calcium,magnesium,zinc,and boron were significantly and positively correlated with the corresponding elements in the soil.Soil organic carbon,total nitrogen,available phosphorus and available potassium were sensitive factors that affected the changes on leaf nutrients of P.massoniana.Soil available elements had significantly positive effects on leaf nutrients,while soil organic carbon and total nutrients had significantly negative effects.In summary,there are significant differences in the soil and leaf nutrients among different forest ages.After planting 15 years,the soil and leaf nutrients of P.massoniana declined,especially due to the limitation of nitrogen and trace elements.For middle-aged P.massoniana plantation,it was recommended to apply nitrogen fertilizer to satisfy its healthy growth,supplemented with appropriate amount of trace elements to enhance plant photosynthesis and protein synthesis and stress resistance.