Wind-induced error in the measurement of soil respiration using closed dynamic chambers
Wind-induced error in the measurement of soil respiration using closed dynamic chambers
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DOI：
10.1016/j.agrformet.2005.06.004
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发表时间：
2005-08-31
影响因子：
6.2
通讯作者：
Wofsy, SC
中科院分区：
文献类型：
--
作者：
Bain, WG;Hutyra, L;Wofsy, SC
我们评估了使用封闭式动态室方法获得的土壤CO2呼吸通量的误差。特别注意到气室顶空和外部环境之间的微小压力梯度，这可能会导致土壤空气的大量流动，导致对土壤呼吸的高估。当空气运动在排气口产生文丘里效应时，这些压力梯度就会形成，该效应旨在确保压力平衡，导致从气室内吸入空气。在哈佛森林的野外实验中，对于密封在防渗板上的密封室，文丘里效应产生了大约每1米1帕S(-1)的压力梯度，但在森林土壤上部署的相同系统中没有观察到压力梯度。土壤空气的质量流动补偿了风驱动的压力梯度，即使在茂密的森林树冠下，也观察到二氧化碳通量增加了超过2倍的风事件。森林土壤的高孔隙率使风或采样流动引起的压力伪影扰乱了土壤的扩散通量，可能会影响几乎所有的密封室方法。土壤呼吸测量中的相关误差必须通过小室设计和评估来解决。(C)2005 Elsevier B.V.保留所有权利。
We assess errors in soil respiration fluxes of CO2 obtained using the closed dynamic chamber method. Particular attention is given to small pressure gradients between the chamber headspace and the external environment that may induce mass flow of soil air, leading to overestimation of soil respiration. These pressure gradients develop as air movement creates a Venturi effect at the vent that is designed to insure pressure equilibration, leading to aspiration of air from within the chamber. During field experiments at the Harvard Forest, the Venturi effect produced pressure gradients of approximately 1 Pa per 1 m s(-1) for a chamber sealed to an impermeable plate, but no pressure gradient was observed in an identical system deployed on the forest soil. Mass flow of soil air compensated for the wind-driven pressure gradients, and increases in CO2 fluxes exceeding a factor of 2 were observed in response to wind events even under a dense forest canopy. The high porosity of forest soils allows pressure artifacts induced by winds or by sampling flows to perturb the diffusive flux from soils, potentially affecting virtually all chamber methods. Associated errors in soil respiration measurements must be addressed through chamber design and evaluation. (c) 2005 Elsevier B.V. All rights reserved.