Allocation and residence time of photosynthetic products in a boreal forest using a low-level 14C pulse-chase labeling technique
Allocation and residence time of photosynthetic products in a boreal forest using a low-level 14C pulse-chase labeling technique
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DOI：
10.1111/j.1365-2486.2006.01300.x
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发表时间：
2007-02-01
影响因子：
11.6
通讯作者：
Trumbore, Susan E.
中科院分区：
文献类型：
--
作者：
Carbone, Mariah S.;Czimczik, Claudia I.;Trumbore, Susan E.
我们对碳（C）如何在植物中分配的理解大部分来自放射性碳（C-14）脉冲追踪标记实验。然而，衰变计数需要大量的C-14，这意味着这些研究大部分仅限于围隔生态系统或受控实验室实验。利用加速器质谱（AMS）的C-14检测的灵敏度增强，我们测试了低水平的C-14脉冲追踪标记技术的实用性，用于量化C分配模式和不同植物组分对加拿大中部马尼托巴黑云杉林的总生态系统呼吸的贡献。现场实验的所有方面都使用了远低于规定健康标准的C-14，而没有显著改变大气中的CO2浓度。在夏末（8月和9月）施用标记物30 d后，通过测定不同生态系统组分呼吸的CO2总量和C-14含量，监测了标记光合产物的时空分配格局。标记的光合产物在林下（羽藓）、冠层（黑云杉）和根际（黑云杉根和相关微生物）中的平均停留时间（MRT）分别< 1、6和15天。从冠层和林下的呼吸表现出显着更大的影响，标记的光合产物比离体根和完整的根际呼吸。30天后，类似的65%的标签同化已呼吸的冠层，类似的20%的根际，和类似的9%的林下植物，与类似的6%的下落不明，也许留在组织中。根和根际呼吸的最大C-14值达到标签应用后4天。30天后，在根、根际和冠层呼吸中仍然可以检测到该标记;如果使用C-13标记，则无法检测到这些剩余标记水平。我们的研究结果支持以前的研究表明，在生长季节的根际呼吸的碳燃料的很大一部分可能是来自存储的C池，而不是最近的光合产物。
Much of our understanding about how carbon (C) is allocated in plants comes from radiocarbon (C-14) pulse-chase labeling experiments. However, the large amounts of C-14 required for decay-counting mean that these studies have been restricted for the most part to mesocosm or controlled laboratory experiments. Using the enhanced sensitivity for C-14 detection available with accelerator mass spectrometry (AMS), we tested the utility of a low-level C-14 pulse-chase labeling technique for quantifying C allocation patterns and the contributions of different plant components to total ecosystem respiration in a black spruce forest stand in central Manitoba, Canada. All aspects of the field experiment used C-14 at levels well below regulated health standards, without significantly altering atmospheric CO2 concentrations. Over 30 days following the label application in late summer (August and September), we monitored the temporal and spatial allocation patterns of labeled photosynthetic products by measuring the amount and C-14 content of CO2 respired from different ecosystem components. The mean residence times (MRT) for labeled photosynthetic products to be respired in the understory (feather mosses), canopy (black spruce), and rhizosphere (black spruce roots and associated microbes) were < 1, 6, and 15 days, respectively. Respiration from the canopy and understory showed significantly greater influence of labeled photosynthates than excised root and intact rhizosphere respiration. After 30 days,similar to 65% of the label assimilated had been respired by the canopy,similar to 20% by the rhizosphere, and similar to 9% by the understory, with similar to 6% unaccounted for and perhaps remaining in tissues. Maximum C-14 values in root and rhizosphere respiration were reached 4 days after label application. The label was still detectable in root, rhizosphere and canopy respiration after 30 days; these levels of remaining label would not have been detectible had a C-13 label been applied. Our results support previous studies indicating that a substantial portion of the C fueling rhizosphere respiration in the growing season may be derived from stored C pools rather than recent photosynthetic products.