Similar variation in carbon storage between deciduous and evergreen treeline species across elevational gradients
Similar variation in carbon storage between deciduous and evergreen treeline species across elevational gradients
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DOI：
10.1093/aob/mct127
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发表时间：
2013-08-01
期刊：
影响因子：
4.2
通讯作者：
Hoch, Guenter
中科院分区：
文献类型：
--
作者：
Fajardo, Alex;Piper, Frida I.;Hoch, Guenter
到目前为止，对树线形成最合理的解释是生长限制假说（GLH），该假说认为碳汇受低温的限制比受碳源的限制更大。支持GLH的证据在万年青树种中很强，但在落叶树线树种中较少且较弱。在不同海拔梯度的落叶-常绿混交林中，假设不同海拔梯度的落叶树线树种和万年青树种具有不同的碳贮量趋势，对不同海拔梯度的落叶-常绿混交林中的GLH进行了检验。在6个落叶-常绿林线交错带的4个海拔高度上对分支边材和茎边材组织进行了测定在智利南部的安第斯山脉（40 S，Nothofagus pumilio和Nothofagus betuloides; 46 S，Nothofagus pumilio和Pinus sylvestris）和瑞士阿尔卑斯山脉（46 N，落叶落叶松（Larix decidua）和松（Pinus cembra）），树木生长（断面积增量）随海拔升高而下降。无论叶的习惯，神经干细胞并没有耗尽海拔，表明没有短缺的碳储存在任何调查的组织。相反，叶（P0.001）和分支边材（P0.0012）组织中的神经干细胞随海拔升高而显著增加.对于所有组织，落叶树种的神经干细胞显著高于常绿树种;平均而言，前者有11个（叶），158个（分支）和103个（边材）显著（P 0.0001）高于后者的神经干细胞。最后，落叶树种有较高的NSC（特别是淀粉）增加与海拔比常绿的干边材，但相反的是真实的叶和分支sapwood.Considering观察到的树木生长减少和增加的NSC与海拔，它的结论是，无论是落叶和万年青树线的物种是汇有限的，当面对温度下降。尽管落叶树种的碳储量的总体要求较高，没有迹象表明，在高山树线交错带的落叶树种的碳限制。
The most plausible explanation for treeline formation so far is provided by the growth limitation hypothesis (GLH), which proposes that carbon sinks are more restricted by low temperatures than by carbon sources. Evidence supporting the GLH has been strong in evergreen, but less and weaker in deciduous treeline species. Here a test is made of the GLH in deciduousevergreen mixed species forests across elevational gradients, with the hypothesis that deciduous treeline species show a different carbon storage trend from that shown by evergreen species across elevations.Tree growth and concentrations of non-structural carbohydrates (NSCs) in foliage, branch sapwood and stem sapwood tissues were measured at four elevations in six deciduousevergreen treeline ecotones (including treeline) in the southern Andes of Chile (40S, Nothofagus pumilio and Nothofagus betuloides; 46S, Nothofagus pumilio and Pinus sylvestris) and in the Swiss Alps (46N, Larix decidua and Pinus cembra).Tree growth (basal area increment) decreased with elevation for all species. Regardless of foliar habit, NSCs did not deplete across elevations, indicating no shortage of carbon storage in any of the investigated tissues. Rather, NSCs increased significantly with elevation in leaves (P 0001) and branch sapwood (P 0012) tissues. Deciduous species showed significantly higher NSCs than evergreens for all tissues; on average, the former had 11 (leaves), 158 (branch) and 103 (sapwood) significantly (P 0001) higher NSCs than the latter. Finally, deciduous species had higher NSC (particularly starch) increases with elevation than evergreens for stem sapwood, but the opposite was true for leaves and branch sapwood.Considering the observed decrease in tree growth and increase in NSCs with elevation, it is concluded that both deciduous and evergreen treeline species are sink limited when faced with decreasing temperatures. Despite the overall higher requirements of deciduous tree species for carbon storage, no indication was found of carbon limitation in deciduous species in the alpine treeline ecotone.