Low mortality in tall tropical trees
Low mortality in tall tropical trees
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高大热带树木死亡率低
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
D. Peart
中科院分区：
文献类型：
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作者：
R. Q. Thomas;J. Kellner;D. Clark;D. Peart
热带森林中最高的树木的动态是特别有趣的，因为它们的碳含量，树冠优势，以及它们死亡时产生的巨大树冠间隙。已知的可能影响高大树木生存的生态机制导致了相互矛盾的预测。水力压力和暴露于大风和干燥会增加死亡率，但最高的树木有最大的采光机会，可以避免掉洞和树枝造成的损害。由于高树的密度低，死亡率的不确定性难以解决，这使得准确估计死亡率具有挑战性。在这里，我们使用激光雷达遥感和实地测量相结合的方法来显示个体超过8.5年的死亡率。在444公顷的低地新热带雨林中，40米高的树木的年增长率为1.2%，不到所有冠层树木景观规模平均值（每年2.7%）的一半。低死亡率可能是由于物种特有的特征降低了死亡风险和/或身高的生态优势超过了风险。无论机制如何，低死亡率对热带森林碳收支具有重要意义，因为我们估计每公顷一个高大的个体代表了2-11%的地上活碳储量。我们的研究结果表明，高度特异性动态可能与传统的直径特异性动态惊人地不同，强调了扩展生态学研究以调查树木高度在森林动态中的作用的重要性。
The dynamics of the tallest trees in tropical forests are of special interest due to their carbon content, canopy dominance, and the large canopy gaps created when they die. Known ecological mechanisms that may influence tall tree survival lead to conflicting predictions. Hydraulic stress and exposure to high winds and desiccation should increase death rates, yet the tallest trees have the greatest access to light and escape damage caused by falling boles and branches. The uncertainty in tall tree mortality rates has been difficult to address due to their low density, which makes mortality rates challenging to estimate accurately. Here, we use a combination of LiDAR remote sensing and field measurements to show that the mortality rate over 8.5 years among individuals .40 m tall in 444 ha of lowland Neotropical rain forest was 1.2% per year, less than half the landscape-scale average for all canopy trees (2.7% per year). The low mortality is likely explained by species-specific traits that decrease the mortality risk and/or ecological advantages of height that outweigh the risks. Regardless of the mechanisms, the low mortality rate has important implications for tropical forest carbon budgets, as we estimated that a single tall individual represents 2-11% of total live aboveground carbon stocks per hectare. Our findings suggest that height-specific dynamics may be surprisingly different from traditional diameter-specific dynamics, emphasizing the importance of extending ecological studies to investigate the role of tree height in forest dynamics.