中国南方生长于不同基质的天然林植物叶片元素含量特征比较

对比中国南方两个热带喀斯特森林、一个热带红树林和来自文献的一个亚热带常绿阔叶林植物叶片元素含量和计量特点。结果表明，受碳酸盐岩的影响，西双版纳和弄岗喀斯特森林植物叶片普遍富含Ca、Mg元素，因岩性差异，含有一定白云岩的弄岗地区的植物富集更多的Mg。西双版纳喀斯特森林存在K、Fe、Na、Zn元素的缺乏状况；由于白云岩矿物成分的特殊性和缓慢的风化速度，弄岗喀斯特植物有更高的叶片K、Zn、S含量。红树林植物富集P、Ca、Mg、Na、S元素，海水环境中大量的离子进入土壤被植物吸收利用，提高了红树的养分含量，并且在高盐环境下Na在叶片中大量富集。但是，红树植物表现缺乏Fe、Si、Zn。亚热带常绿阔叶林植物受酸性土影响大，Mn元素大量富集，P与Na的含量缺乏，并且相比其他生境，常绿阔叶林的N、P、Ca、Mg含量较低。西双版纳和弄岗的喀斯特森林植物叶片N/P比分别为14.27和18.26，说明前者受到N、P的共同限制，后者主要为P限制；红树植物N/P比为13.12，受N限制；常绿阔叶林植物本身严重缺P，N/P比为26.27，表现出明显的P限制。所研究的不同基质上的植物，叶片N与P元素之间均呈显著正相关，这种稳定的协同关系是植物适应环境的普遍规律。Ca与Mg两个二价阳离子元素在喀斯特森林和常绿阔叶林中为协同关系，而在红树林中则不存在相关性，分析表明Na盐胁迫下增加了Mg的吸收，改变了Ca、Mg的平衡关系。N与K元素在红树林和常绿阔叶林中为协同关系，而由于喀斯特环境中Ca、Mg协同影响了K的吸收，改变了N、K的协同关系。P与Zn在喀斯特森林和红树林中都表现出协同关系，这与两种元素在植物代谢过程中都参与了酶的合成有关。红树植物表现K和Mn的拮抗关系，而在喀斯特森林和常绿阔叶林中均未有相关性。S与P元素在弄岗喀斯特森林中表现出正相关，这种协同性可以帮助喀斯特植物缓解缺P的症状，而在高P的红树植物中没有相关性。研究结果对于森林生态系统的生物地球化学循环模拟和生态系统管理有重要参考意义。

Comparison of foliar element contents of plants from natural forests with different substrates in southern China

In this study, the element contents and chemometric characteristics of the leaves of two tropical karst forests, a tropical mangrove forest, and a subtropical evergreen broad-leaved forest (SEBF) from the literature were compared. The results showed that the plant leaves from karst forests in Xishuangbanna and Nonggang were generally rich in Ca and Mg due to the influence of carbonate rocks. The rocks of Nonggang area are composed of a certain amount of dolomite, which makes plants contained much higher Mg. The karst forest in Xishuangbanna was lack of K, Fe, Na and Zn. Due to the composition of certain percentage of deciduous trees in Xishuangbanna karst forest, the mean foliar content was relatively lower. However, the plants in Nonggang karst forest had a higher content of K, Zn and S. Mangrove plants were rich in P, Ca, Mg, Na and S. This is likely because of the relatively rich mineral elements in the seawater that entered the soil and were absorbed and by the mangrove plants. However, the mangrove plants were deficit of Fe, Si and Zn. Plants in subtropical evergreen broad-leaf forest were rich of Mn but deficit of P and Na. Compared with other two types of forests, the evergreen broad-leaf forest had a lower content of N, P, Ca and Mg. The foliar N/P ratios of the plants in karst forest of Xishuangbanna and Nonggang were 14.27 and 18.26, respectively, indicating the nutrient limitation of both N and P in the former or P in the latter. The N/P ratio of mangrove plants was 13.12, indicating the limitation of N. The evergreen broad-leaf forest plants were seriously deficient of P as indicated by their mean N/P ratio of 26.27. There was a significantly positive correlation between N and P elements in the plant leaves from all four forests, revealing a general rule of plant adaptation to the environment. Two divalent cations, Ca⁺⁺ and Mg⁺⁺ had synergic relationship in the karst forests and evergreen broad-leaf forest, but there was no correlation between them in the mangrove forest. The analysis showed that the absorption of Mg of the mangrove plants was increased due to the stress of sodium salt, which changed the balance of Ca and Mg. N and K showed a synergic relationship in mangrove forest and evergreen broad-leaf forest, but the synergy of Ca and Mg in karst environment affected the absorption of K, which changed the synergic relationship between N and K. P and Zn showed a synergic relationship in the karst forests and mangrove forest because these two elements were involved in the enzyme synthesis in plant metabolism. The antagonistic relationship between K and Mn in mangrove plants may be helpful for mangrove plants to avoid excessive absorption of Mn, but there was no correlation between these two elements in karst forest and evergreen broad-leaf forest. S and P showed positive correlation in Nonggang karst forest, which could help the karst plants to alleviate P deficiency symptoms, but there was no correlation in mangrove plants with abundant P. The present results have important implications for the modelling of biogeochemical cycle and management of forest ecosystems.