Fine-root production dominates response of a deciduous forest to atmospheric CO2 enrichment.
Fine-root production dominates response of a deciduous forest to atmospheric CO2 enrichment.
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DOI：
10.1073/pnas.0403491101
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发表时间：
2004-06
影响因子：
11.1
通讯作者：
R. Norby;Joanne Ledford;C. D. Reilly;N. E. Miller;E. O'neill
中科院分区：
文献类型：
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作者：
R. Norby;Joanne Ledford;C. D. Reilly;N. E. Miller;E. O'neill
细根生产和周转是生态系统地球化学循环的重要调节因子，也是生态系统对全球变化响应的关键组成部分。我们提出了一个近连续6年的记录细根生产和死亡率的微型电子显微镜分析的封闭冠层，落叶枫香林在自由空气CO（2）富集实验。与环境空气中的地块相比，在550 ppm CO（2）的地块中，细根的年产量增加了一倍以上。这种反应是净初级生产力持续增长22%的主要组成部分。年细根死亡率与年产量相匹配，根的平均停留时间并没有被升高的CO（2）改变，但在仲夏的峰值细根现存量显着较高的CO（2）富集地块，特别是在土壤剖面较深。额外的碳优先分配到细根，这在这个物种中有一个快速的周转率，而不是树干，降低了长期增强的可能性，通过提高CO（2）的生物量中的碳封存。然而，一些细根碳在土壤池中的封存并不排除，并且可能有其他好处的树从一个季节性的更大和更深的细根系统。根系动力学可以解释生态系统对大气CO（2）浓度升高的反应差异;因此，在全球变化的大气中准确评估森林中的碳通量和碳储存必须考虑到这一不可见和难以测量的组成部分。
Fine-root production and turnover are important regulators of the biogeochemical cycles of ecosystems and key components of their response to global change. We present a nearly continuous 6-year record of fine-root production and mortality from minirhizotron analysis of a closed-canopy, deciduous sweetgum forest in a free-air CO(2) enrichment experiment. Annual production of fine roots was more than doubled in plots with 550 ppm CO(2) compared with plots in ambient air. This response was the primary component of the sustained 22% increase in net primary productivity. Annual fine-root mortality matched annual production, and the mean residence time of roots was not altered by elevated CO(2), but peak fine-root standing crop in midsummer was significantly higher in CO(2)-enriched plots, especially deeper in the soil profile. The preferential allocation of additional carbon to fine roots, which have a fast turnover rate in this species, rather than to stemwood reduces the possibility of long-term enhancement by elevated CO(2) of carbon sequestration in biomass. However, sequestration of some of the fine-root carbon in soil pools is not precluded, and there may be other benefits to the tree from a seasonally larger and deeper fine-root system. Root-system dynamics can explain differences among ecosystems in their response to elevated atmospheric CO(2); hence, accurate assessments of carbon flux and storage in forests in a globally changing atmosphere must account for this unseen and difficult-to-measure component.