云南松形态和叶片碳氮磷化学计量及其海拔变化特征

云南松(Pinus yunnanensis Franch.)是我国西南地区特有的物种,在当地的经济、生态和水土保持功能方面占有重要地位。本研究以云南东北部不同海拔的云南松天然次生林为对象,测定了成年植株的胸径、株高、叶片长度、干重、比叶长及叶片碳、氮、磷含量,分析了不同海拔下叶片碳氮磷化学计量特征。结果表明:随海拔升高,胸径、株高、叶P含量和叶C∶N呈现"中间高,两头低"的趋势,而叶C∶P和N∶P呈现的趋势与叶P和叶C∶N的相反;云南松叶片单束松针长、比叶长、叶C、N随海拔升高呈明显降低的趋势,而单束松针重呈增加的趋势;各海拔的N∶P值(平均值为5.82±0.10)均小于14,且与植株胸径、株高呈显著负相关;该地区云南松对海拔具有较强的适应性,植株生长主要受N元素的营养限制,该结果支持生长速率假说。本研究揭示了云南松化学计量特征的空间格局变化规律,为云南松林的经营管理提供科学依据。

Morphology and leaf C,N and P stoichiometry of Pinus yunnanensis and their elevational variations.

Pinus yunnanensis,an endemic conifer species in southwestern China,is important for regional economic development and soil and water conservation. Here,we investigated the elevational variations of diameter at breast height(DBH),tree height,leaf morphology and carbon(C),nitrogen(N) and phosphorus(P) concentrations of mature individuals of P. yunnanensis in natural secondary forests of northeast Yunnan. We analyzed adaptive responses of foliar C ∶ N ∶ P stoichiometry along the elevation gradient. The results showed that DBH,tree height,leaf P concentration and C ∶ N ratio increased first and then decreased with elevation,while C ∶ P and N ∶ P ratios exhibited an opposite pattern. In addition,leaf length per bundle,specific leaf length,and concentrations of C and N were lower at higher elevation,while dry mass per bundle increased with elevation. Leaf N ∶ P(mean 5. 82 ± 0. 10) in each elevation was lower than 14,which was significantly negatively correlated with DBH and tree height. These results suggest that P. yunnanensis showed adaptive growth and leaf nutrient balance with elevation. The growth of P.yunnanensis was limited by N,supporting the growth rate hypothesis where growth rate is expected to be negatively related with plant N ∶ P. The elevational patterns of stoichiometric characteristics of P. yunnanensis revealed in this study could be helpful for vegetation management.