Belowground fate of 15N injected into sweetgum trees (Liquidambar styraciflua) at the ORNL FACE Experiment
Belowground fate of 15N injected into sweetgum trees (Liquidambar styraciflua) at the ORNL FACE Experiment
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DOI：
10.1002/rcm.4227
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发表时间：
2009-10-01
影响因子：
2
通讯作者：
Brice, Deanne J.
中科院分区：
文献类型：
--
作者：
Garten, Charles T., Jr.;Brice, Deanne J.
氮循环是森林生态系统对大气CO2浓度升高响应的重要制约因素。我们的目标是跟踪运动的N-15，注入树液，不稳定和稳定形式的土壤有机质部分来自周转的树根下升高（545 ppm）和环境（394 ppm）大气CO2浓度在橡树岭国家实验室（ORNL）的FACE（自由空气二氧化碳富集）实验。24枫香树，平均分为CO2处理，注入3.2克N-15-硫酸铵（99原子%），并在树下收集土壤样品超过89周。对于16厘米深的土壤样品收集下的研究树木，有28%以上的细根（小于或等于2毫米直径）的生物量在CO2浓度升高（P = 0.001），但没有显着的治疗效果的数量necromass，粗根生物量，或在树根和necromass的N浓度。氮-15从茎注射部位迅速移动到根中，并且根、坏死物质和不稳定有机物（即颗粒有机物，POM）的N-15含量随时间增加。注射后89周，约76%的坏死团N-15源自细根周转。POM中的N-15的周转时间（47周）比根中的N-15（16至22周）相对较长。在1.7年的研究期间，N-15移动到较慢的循环POM和根N和POM中的N之间的周转时间的差异可以施加渐进的限制土壤N的可用性与林分成熟，无论大气中的CO2，特别是如果通过分解POM的N释放是必不可少的，以维持森林净初级生产力。出版社：John Wiley & Sons，Ltd.
Nitrogen (N) cycling can be an important constraint on forest ecosystem response to elevated atmospheric CO2. Our objective was to trace the movement of N-15, injected into tree sap, to labile and stable forms of soil organic matter derived partly from the turnover of tree roots under elevated (545 ppm) and ambient (394 ppm) atmospheric CO2 concentrations at the Oak Ridge National Laboratory (ORNL) FACE (Free-Air Carbon Dioxide Enrichment) Experiment. Twenty-four sweet-gum trees, divided equally between CO2 treatments, were injected with 3.2 g N-15-ammonium sulfate (99 atom %), and soil samples were collected beneath the trees over a period of 89 weeks. For 16 cm deep soil samples collected beneath the study trees, there was 28% more fine root (less than or equal to 2 mm diameter) biomass under elevated CO2 (P = 0.001), but no significant treatment effect on the amounts of necromass, coarse root biomass, or on the N concentrations in tree roots and necromass. Nitrogen-15 moved quickly into roots from the stem injection site and the N-15 content of roots, necromass, and labile organic matter (i.e. particulate organic matter, POM) increased over time. At 89 weeks post-injection, approximately 76% of the necromass N-15 originated from fine root turnover. Nitrogen-15 in POM had a relatively long turnover time (47 weeks) compared with N-15 in roots (16 to 22 weeks). Over the 1.7 year period of the study, N-15 moved from roots into slower cycling POM and the disparity in turnover times between root N and N in POM could impose progressive limitations on soil N availability with stand maturation irrespective of atmospheric CO2, especially if the release of N through the decomposition of POM is essential to sustain forest net primary production. Published in 2009 by John Wiley & Sons, Ltd.