Contrasting controls on tree ring isotope variation for Amazon floodplain and terra firme trees.
Contrasting controls on tree ring isotope variation for Amazon floodplain and terra firme trees.
复制标题
亚马逊洪泛区和陆地树木年轮同位素变化的对比控制。
DOI：
10.1093/treephys/tpz009
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发表时间：
2019
期刊：
影响因子：
4
通讯作者：
Barçante Ladvocat Cintra B
中科院分区：
文献类型：
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作者：
Barçante Ladvocat Cintra B
热带树木年轮中的同位素可以提高我们对树木对气候反应的理解。我们评估了气候和生长条件对4棵亚马逊树的树轮氧和碳同位素(δ18OTr和δ13CTR)的影响。我们分析了生长在不同季节性地点的两种陆地(非淹水)和两种泛滥平原树木的年轮内同位素变化。我们发现，δ18O和δ13CTR的年内格局明显不同，主要受天气和水源δ18O季节变化的驱动。生长在最潮湿条件下的树木，其同位素的季节变化最小。基于现有理论的树轮纤维素同位素模型很好地再现了年轮内的变化，气孔和叶肉导度可能对δ13CTR的变化做出了贡献。气候分析表明，Terra Firmeδ18O信号与全流域降水有关，表明水源δ18O的影响，而洪泛区树木记录到与当地气候有关的叶片丰富效应。因此，在所分析的两个不同物种中，本质上不同的过程(源水和叶片富集物)影响δ18ORT。这些差异可能既是物种特有特征的结果，也是洪泛平原和陆地环境生长条件不同的结果。对δ13CTR和δ18ORT的同时分析支持这一解释，因为它显示出这两种同位素在由叶片气孔导度共同控制的洪泛区树木中的年内模式非常相似，而陆地树两种同位素之间的协变性较小。我们的结果从植物生理学的角度来看很有趣，并对气候重建有意义，因为树木记录了本质上不同的过程。
Isotopes in tropical trees rings can improve our understanding of tree responses to climate. We assessed how climate and growing conditions affect tree-ring oxygen and carbon isotopes (δ18OTRand δ13CTR) in four Amazon trees. We analysed within-ring isotope variation for two terra firme (non-flooded) and two floodplain trees growing at sites with varying seasonality. We find distinct intra-annual patterns of δ18OTRand δ13CTRdriven mostly by seasonal variation in weather and source water δ18O. Seasonal variation in isotopes was lowest for the tree growing under the wettest conditions. Tree ring cellulose isotope models based on existing theory reproduced well observed within-ring variation with possible contributions of both stomatal and mesophyll conductance to variation in δ13CTR. Climate analysis reveal that terra firme δ18OTRsignals were related to basin-wide precipitation, indicating a source water δ18O influence, while floodplain trees recorded leaf enrichment effects related to local climate. Thus, intrinsically different processes (source water vs leaf enrichment) affect δ18OTRin the two different species analysed. These differences are likely a result of both species-specific traits and of the contrasting growing conditions in the floodplains and terra firme environments. Simultaneous analysis of δ13CTRand δ18OTRsupports this interpretation as it shows strongly similar intra-annual patterns for both isotopes in the floodplain trees arising from a common control by leaf stomatal conductance, while terra firme trees showed less covariation between the two isotopes. Our results are interesting from a plant physiological perspective and have implications for climate reconstructions as trees record intrinsically different processes.