西藏急尖长苞冷杉与川滇高山栎叶片δ13C沿海拔梯度的变化

Altitudinal Variation of the Foliar δ^(13)C in Abies georgei var. smithii and Quercus aquifolioides in Tibet

以青藏高原东南部亚高山暗针叶林的主要组成树种急尖长苞冷杉(Abies georgei var.smithii)和川滇高山栎(Quercus aquifolioides)为研究对象,分别在其自然分布海拔范围内采集叶片样品,测定其δ13C与单位面积的叶片重量(LMA),研究了急尖长苞冷杉和川滇高山栎叶片δ13C与单位面积的叶片重量(LMA)沿海拔梯度的变化趋势以及二者之间的差异.结果表明:急尖长苞冷杉叶片δ13C值的变化范围在-28.88‰^-27.06‰之间,平均值是-28.11‰;而川滇高山栎叶片δ13C值的变化范围在-29.11‰^-25.57‰之间,平均值是-27.63‰;与全球高海拔和青藏高原植物叶片的δ13C值相比,前者变化范围小且偏低,而后者变化范围及平均值相对比较接近.随着海拔的升高,急尖长苞冷杉叶片δ13C和LMA并不是线性增加,而是呈不规则的变化,而川滇高山栎叶片δ13C和LMA则显著线性增加,且δ13C和LMA之间呈显著线性正相关.这说明,在青藏高原东南部随着海拔梯度的变化,虽然常绿针叶林和落叶阔叶林叶片δ13C和LMA响应趋势不同,但是δ13C和LMA之间的正相关关系却不受树种种类影响而具有普遍性;这种差异可能是由群落内物种种内和种间竞争能力大小的差异,以及非生物环境因子如温度、降水等共同作用而造成的结果.

In this paper, the foliar δ13C and leaf mass per unit area （LMA） in Abies georgei var. smithii and Quercus aquifolioides, the dominant species of subalpine coniferous forests in Tibet, changing with altitude are studied. The foliar δ13C values vary from -28.88‰ to -27.06%, with an average of -28. 11‰ in Abies georgei var. smithii; and from-29.11‰to -25.57 ‰, with an average of -27.32‰ in Quercus aquifolioides. Compared with δ13C from the other plants from the Tibetan Plateau and the other high altitude regions over the world, both variation ranges and average values are smaller in Abies georgei var. smithii,but they are average in Quercus aquifolioides. Overall, values of foliar δ13C and LMA show no linear relationship with altitude in Abies georgei var. smithii but show a linearly increasing relationship with altitude in Quercus aquifolioides. Furthermore, the relationships between the foliar δ13C and LMA are positively correlated in both species. The differences in the foliar δ13C and LMA responding to altitude in this two species may be due to a complex interaction between biotic factors （e. g inter-specific competition） and abiotic factors （for example, temperature and precipitation）.