Altitude effect on leaf wax carbon isotopic composition in humid tropical forests
Altitude effect on leaf wax carbon isotopic composition in humid tropical forests
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DOI：
10.1016/j.gca.2017.02.022
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发表时间：
2017-06
影响因子：
5
通讯作者：
Mong Sin Wu;S. Feakins;R. Martin;A. Shenkin;L. Bentley;B. Blonder;N. Salinas;G. Asner;Y. Malhi
中科院分区：
文献类型：
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作者：
Mong Sin Wu;S. Feakins;R. Martin;A. Shenkin;L. Bentley;B. Blonder;N. Salinas;G. Asner;Y. Malhi
植物叶蜡生物标志物的碳同位素组成常被用来重建古环境条件。添加到有限的校准信息可用于现代热带森林，我们分析了植物叶和叶蜡碳同位素组成的森林冠层树木在一个高度生物多样性，海拔3.3公里梯度的东侧的安第斯山脉。我们采样的优势树种，并评估其相对丰富度在每个树木群落。共采集了沿着9个林地、129个树种的405片阳光照射下的冠层叶片，进行了叶片和叶片石蜡正构烷烃（C27-C33）含量和碳同位素（δ 13 C）分析;一个子集（76个个体，29种，另外分析了五个森林样地）的正链烷酸（C22-C32）浓度和δ 13 C。δ 13 C值显示+0.87 ± 0.16‰ km−1的趋势（95%CI，r2= 0.96，p < 0.01），C29正构烷烃为+1.45 ± 0.33‰ km−1（95%CI，r2= 0.94，p < 0.01）。这些碳同位素梯度在多物种样本集中定义，并在广泛分布的属和几个科中得到证实，表明对环境的生化反应对分类更替具有鲁棒性。我们计算分馏和比较绝热梯度，环境变量，叶片waxn-alkane浓度，和太阳/阴影位置，以评估影响叶面化学反应的因素。在海拔4 km的安第斯山脉森林覆盖范围内，预计高地C3植物叶片及其正烷基脂的δ 13 C值比低地高4-6‰，我们预计这种模式是非常潮湿的热带山地环境的系统特征。δ 13 C值的这种海拔依赖性应告知沉积档案的解释，因为13 C富集值可能来自C4草，成岩输入或高地C3植物。最后，我们概述了潜在的叶蜡碳同位素追踪生物标志物来源集水区和古测高。
The carbon isotopic composition of plant leaf wax biomarkers is commonly used to reconstruct paleoenvironmental conditions. Adding to the limited calibration information available for modern tropical forests, we analyzed plant leaf and leaf wax carbon isotopic compositions in forest canopy trees across a highly biodiverse, 3.3 km elevation gradient on the eastern flank of the Andes Mountains. We sampled the dominant tree species and assessed their relative abundance in each tree community. In total, 405 sunlit canopy leaves were sampled across 129 species and nine forest plots along the elevation profile for bulk leaf and leaf waxn-alkane (C27–C33) concentration and carbon isotopic analyses (δ13C); a subset (76 individuals, 29 species, five forest plots) were additionally analyzed forn-alkanoic acid (C22–C32) concentrations andδ13C.δ13C values display trends of +0.87 ± 0.16‰ km−1(95% CI,r2= 0.96,p< 0.01) for bulk leaves and +1.45 ± 0.33‰ km−1(95% CI,r2= 0.94,p< 0.01) for C29n-alkane, the dominant chain length. These carbon isotopic gradients are defined in multi-species sample sets and corroborated in a widespread genus and several families, suggesting the biochemical response to environment is robust to taxonomic turnover. We calculate fractionations and compare to adiabatic gradients, environmental variables, leaf waxn-alkane concentrations, and sun/shade position to assess factors influencing foliar chemical response. For the 4 km forested elevation range of the Andes, 4–6‰ higherδ13C values are expected for upland versus lowland C3plant bulk leaves and theirn-alkyl lipids, and we expect this pattern to be a systematic feature of very wet tropical montane environments. This elevation dependency ofδ13C values should inform interpretations of sedimentary archives, as13C-enriched values may derive from C4grasses, petrogenic inputs or upland C3plants. Finally, we outline the potential for leaf wax carbon isotopes to trace biomarker sourcing within catchments and for paleoaltimetry.