Design and performance of a new FACE (free air carbon dioxide enrichment) system for crop and short vegetation exposure
Design and performance of a new FACE (free air carbon dioxide enrichment) system for crop and short vegetation exposure
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DOI：
10.1016/j.envexpbot.2016.06.002
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发表时间：
2016-10-01
影响因子：
5.7
通讯作者：
Damsohn, Walter
中科院分区：
文献类型：
--
作者：
Fangmeier, Andreas;Torres-Toledo, Victor;Damsohn, Walter
目前的大气二氧化碳水平是过去80万年来前所未有的，需要对其潜在影响进行评估。自由空气二氧化碳富集（FACE）被认为是最适合实验现场调查的暴露系统。虽然早期的FACE技术涉及用于预稀释二氧化碳的风扇，但现在采用带风扇和不带风扇的系统，以纯二氧化碳运行。FACE技术中最常用的结构包括从圆形或八角形的静压室内进行外围注入，该静压室周围有二氧化碳释放管和喷射孔，可以在整个试验区产生[CO2]梯度。在这里，我们提出了一种新的面向短植被（作物和草地）的FACE设计，该设计不涉及周边注入，而是直接在地块冠层内分配二氧化碳。该系统包括许多二氧化碳释放孔，这些孔位于从树冠上部表面垂下并延伸至树冠的多孔管中。它们的高度可以根据作物生长情况进行调整。地块面积为2米× 2米，允许以低二氧化碳消耗成本进行大量重复（在24小时运行期间，五个重复地块一个季节6.5吨二氧化碳= 3.5千克二氧化碳每平方米(2)可用地块面积和一天）。系统在CO2控制方面的性能在时间和空间上都非常好，白天93%的瞬时读数与设定值的偏差匹配20%，并且在暴露的冠层内给定时刻的[CO2]变化很小。一些遮阳（树冠发育时约4%）是由样地的FACE结构造成的，但几乎没有观察到任何其他小气候人为因素。FACE系统采用模块化结构，具有高度的灵活性，可适应各种类型的矮植被。(C) 2016 Elsevier B.V.版权所有
Current atmospheric CO2 levels are unprecedented for the last 800,000 years and require assessments of their potential effects. Free Air Carbon dioxide Enrichment (FACE) is regarded as the most appropriate exposure system for experimental field investigations. While the early FACE technology involved fans for pre-dilution of CO2, now systems both with fans and without fans operating with pure CO2 are employed. The most often used construction in FACE technology involves peripheral injection from a circular or octagonal plenum with CO2 release pipes and jet holes surrounding the experimental plot which can create [CO2] gradientsacross the plot. Here, we present a new FACE design for short vegetation (crops and grassland) that does not involve peripheral injection but distributes CO2 directly within the plot canopy. The system involves numerous CO2 release holes in porous tubes that hang down from the upper canopy surface and stretch into the canopy. They can be adjusted in height according to crop growth. Plot size was 2 m x 2 m which allows for a high number of replicates at low CO2 consumption costs (6.5 tons CO2 in one season at five replicate plots = 3.5 kg CO2 per m(2) usable plot area and day during 24hr operation). System performance in terms of CO2 control was very good both in time and space, with 93% of all instantaneous readings during daylight hours matching 20% deviation from the set point, and low variation of [CO2] at a given moment within the exposed canopy. Some shading (c. 4% at full canopy development) resulted from the FACE structure at the plots but hardly any other microclimatic artifacts were observed. The FACE system is of modular construction and highly flexible and adaptable to various types of short vegetation. (C) 2 016 Elsevier B.V. All rights reserved.