亚热带红壤侵蚀区马尾松针叶养分含量及再吸收特征

叶片衰老过程中的养分再吸收是植物适应养分贫瘠生境的一种重要策略,一直是生态学领域的研究热点。以亚热带红壤侵蚀区生态恢复先锋树种马尾松为研究对象,分析4种不同恢复水平下马尾松叶片养分含量随叶龄的变化情况及养分再吸收特征。结果表明:(1)叶片中N、P、K含量变化范围分别在(6.10±0.52)—(12.02±0.85)mg/g、(0.17±0.03)—(1.02±0.01)mg/g、(1.58±0.49)—(9.46±0.90)mg/g,随叶龄增长整体呈先增加后降低的趋势,具有一个快速积累期和一个相对漫长衰减期的动态特征,这表明叶龄也是影响叶片养分含量的重要因素;(2)叶片N、P、K含量随生境恢复水平的提高而增加,且N、P含量在除凋落叶外的叶龄阶段均表现出显著正相关,表明叶片中这两种营养元素在动态变化上存在协同性;(3)在叶片N、P、K再吸收效率中,P、K再吸收效率较高,而N相对较低。养分再吸收受生境中营养元素的含量水平、循环方式等因素的综合影响表现出一定选择性,对生境中较为贫瘠或使其生长受到限制的元素具有较高的再吸收效率。这不仅可以减小植物对外源养分的依赖性,同时也维持了体内重要营养元素的平衡。随叶龄增长叶片中N/P逐渐增大,反映出在叶片衰老过程中对限制元素P具有较强的再吸收能力,这种反馈调节提高了马尾松对养分贫瘠环境的适应性。本文的研究结果可为亚热带红壤侵蚀退化区先锋物种在贫瘠生境条件下的养分利用机制与适应对策方面的研究提供理论依据。

Foliar nutrient content and resorption efficiency of Pinus massoniana in the subtropical red soil erosion region

Resorption of nutrients from senescing leaves is an important strategy for plants to adapt to the environments with very poor nutrient supplies, and it has been an important topic in ecological research for many years. This study investigated the changes in nutrient content, and the characteristics of nutrient resorption, during leaf aging for a pioneer species Pinus massoniana under four different restoration stages in a subtropical red soil erosion region. The results revealed that:(1) the average contents of leaf N, P, and K were (6.10±0.52)-(12.02±0.85) mg/g, (0.17±0.03)-(1.02±0.01) mg/g, and (1.58±0.49)-(9.46±0.90) mg/g, respectively. The contents of all three nutrient elements had a tendency to first increase then decrease during the process of leaf aging, indicating a dynamic process involving a period of rapid accumulation followed by a period of slow attenuation. Such a dynamic tendency was very obvious for N. Despite the fact that P and K showed a similar pattern to that of N, these nutrients showed relatively small changes during the dynamic process. (2) During the habitat restoration process, the contents of leaf N, P, and K increased as the habitat was restored, and the contents of N and P showed significantly positive correlation at different leaf ages compared to that in the leaf litter, suggesting that the two nutrients N and P had a covariation dynamic. (3) Among the three elemental leaf nutrients, the resorption efficiencies of P and K were relatively high, and N resorption efficiency was relatively low, which indicates there was a selection in the nutrient resorption response to the nutrient contents and circulation in different habitats. The nutrient resorption efficiency was increased at a very low environmental supply, or when the nutrient was a limiting factor to plant growth. Such an adaptation strategy would not only reduce the dependency of plants on outside environmental resources, but also help to maintain the balance of important nutrients within the plants. Throughout the leaf aging process, the leaf N/P content increased gradually, indicating a high resorption capacity of the limiting element P toward leaf senescence. Such feedback regulation improves the adaptability of P. massoniana to adapt to environments with poor nutrient supplies. The results of this research can provide a theoretical basis for further investigation into the mechanisms behind nutrient utilization for the pioneer species in subtropical red soil erosion areas with poor nutrient resources.