非理想涡流位点的 CO2通量测量
Summary
所提出的协议在波兰目前重新造林的风投地点,在非典型地点使用涡差差法,适用于总面积有限的所有类型的短冠生态系统。详细介绍了测量现场设置规则、通量计算和质量控制以及最终结果分析。
Abstract
该协议是利用涡流协方差(EC)技术在波兰目前重新造林的风投区,在非典型生态系统中研究空间和时间平均净CO2通量(净生态系统生产,NEP)的一个例子。龙卷风事件发生后,在幸存的林场内形成了一条相对狭窄的”走廊”,使这类实验复杂化。在这种情况下,其他测量技术(如室法)的应用更加困难,因为特别是在开始时,倒下的树木和一般地的异质性为执行提供了一个具有挑战性的平台磁通量测量,然后适当高档获得的结果。与在未受破坏的森林中进行的标准EC测量相比,在选址和数据分析方面,风投地区需要特别考虑,以确保其代表性。因此,在这里,我们提出了一个实时的连续CO2磁通量测量协议,在一个动态变化的非理想EC站点,其中包括(1)站点位置和仪器设置,(2)磁通量计算,(3)严格的数据过滤和质量控制,以及(4)间隙填充和净通量划分成CO2呼吸和吸收。所述方法的主要优点是,它提供了实验设置和从头开始测量性能的详细描述,可应用于其他空间有限的生态系统。也可以将其视为如何处理非常规站点操作的建议列表,为非专家提供说明。获得质量检查,填补缺口,半小时净CO2值,以及吸收和呼吸通量,可以最终汇总到每日,每月,季节性或每年的总数。
Introduction
目前,在大气-陆地生态系统二氧化碳(CO2)交换研究中最常用的技术是涡测协方差(EC)技术1。EC方法已经使用了几十年,关于所有方法、技术和实际问题的全面说明已经出版2,3,4。与用于类似目的的其他技术相比,EC 方法允许从自动点测量中获得空间和时间平均净 CO2通量,该测量考虑复杂中所有元素的贡献生态系统,而不是费力的手动测量(例如,腔室技术)或采集许多样本的要求1。
在陆地生态系统中,森林在C循环中起着最重要的作用,许多科学活动的重点是研究其CO2周期、木质生物量中的碳储存及其与不断变化的气候条件之间的相互关系。直接测量或建模5。许多EC地点,包括最长的通量记录之一6,被设置在不同类型的森林7。通常,在测量开始之前,会仔细选择场地位置,目标是尽可能实现最均匀和最大的区域。虽然,在受干扰的林场,如风向,EC测量站的数量仍然不足8,9,10。原因之一是测量场地设置的后勤困难,最重要的是,少数突然出现的位置。为了在风投区获得信息最丰富的结果,在发生此类偶发事件后尽快开始,这可能会导致其他问题。与未受污染的林场相比,EC在风投地点的测量更具挑战性,并可能偏离已经确立的程序3。由于一些极端风现象造成了空间有限的区域,因此需要周到的测量站位置和仔细的数据处理,以便得出尽可能多的可靠通量值。在EC方法应用中也出现了类似的困难(例如,在一个长而狭窄的湖上完成的完成研究),其中测量的CO2通量需要严格的数据过滤11,12,以确保其空间代表性。
因此,所提出的协议是一个在非典型地点使用EC方法的例子,不仅针对风投区,而且针对所有具有有限面积的其他类型的短植被(例如,位于较高植被类型之间的农田)。拟议方法的最大优点是一般描述复杂的程序,需要高级知识,从站点位置选择和仪器设置到最终结果:高质量 CO2的完整数据集通 量。测量协议的技术新颖性是使用独特的基础结构用于 EC 系统放置(例如,具有定义高度的三脚架,即带有可调节的电动桅杆的”迷你塔”,允许更改传感器)。
Protocol
1. 场地位置和仪表设置 选择相对均匀和平坦的地形中的测量场地位置,以满足 EC 方法的基本要求。避免使用地形复杂(凹陷、斜坡)或靠近空气动力学障碍物的地方(例如,幸存的树架),以免扭曲气流。 检查物种组成和植物覆盖。选择特征最相似的地方:主要植被类型的年龄和高度。 如果可能的话,进行一些额外的土壤调查,这有助于选择均匀区域。比较几个地点的土壤类型(土壤剖?…
Representative Results
在非理想EC场址的磁通过滤和质量控制中,关键步骤之一是评估测得的磁通量的空间代表性。鉴于计算是使用商业的、广泛应用的软件进行的,进行这种分析的最简单方法是仅根据风向和足迹估计包括所需区域的测量(见第3.7节)。因此,在Tlen I站点的卫星图片背景上,风玫瑰图,具有选择的风向和最大可接受的通量足迹延伸,标记为蒙带多边形,在这里显示为分析结果的可视化表示(<…
Discussion
该协议提出了在非理想地点(这里为重新造林的风投场)使用的涡流协方差 (EC) 方法:场地位置和测量基础设施设置、净 CO2通量计算和后处理,以及有关填补和通量分区程序。
尽管 EC 技术在世界各地的许多测量站点中普遍使用,但大多数都是不受干扰的生态系统,其中设计和以下数据处理可以根据标准解决方案(例如 FLUXNET 或 ICOS 网络协议)进行).虽然在诸如风投地点等要求高…
Disclosures
The authors have nothing to disclose.
Acknowledgements
这项研究得到了波兰华沙国家森林总局(LAS项目,OR-2717/27/11号)的资助。我们要感谢波兰波兹南生命科学大学气象系的整个研究小组参与执行该协议,并感谢他们在创建协议视觉版本时的帮助。
Materials
| Adjustable mast with metal rails and electric engine (24 V) | maszty.net | – | Alternative basic construction. To be designed and made by professionals |
| EddyPro | LI-COR, Inc. | ver. 6.2.0. | Free commercial software for fluxes calculation. Available on a website: https://www.licor.com/env/products/eddy_covariance/software.html, on request |
| Enclosed-path infrared gas analyzer | LI-COR, Inc. | LI-7200 | One of two instruments of the eddy covariance system (EC) used for CO2 fluxes measurements. Other types of fast analyzers (>10Hz sampling frequency) can be used |
| REddyProc | – | – | Free software for EC fluxes gap filling and partitioning. Available on Max Planck Institute for Biogeochmistry: https://www.bgc-jena.mpg.de/bgi/index.php/Services/REddyProcWeb. Both online tool and R package are provided. |
| Short aluminum tower base with concrete foundation | maszty.net | – | Alternative basic construction (pioneering solution). To be designed and made by professionals |
| Sonic anemometer | Gill Instruments | Gill Windmaster | One of two instruments of the eddy covariance system (EC) used for wind speed measurements. Other types of three-dimensional sonic anemometers can be used |
| Stainless-steel tripod | Campbel Scientific, Inc. | CM110 10 ft | The basic construction for eddy covariance (EC) system. Can be constructed by yourself- materials to be found in a hardware store |
| Sunshine sensor | Delta-T Devices Ltd. | BF5 | One of the exemplary instruments for photosynthetic photon flux density measurements (PPFD). To be bought from several commercial companies. Remember to place it above the canopy, far from reflective surfaces. |
| Thermistors | Campbel Scientific, Inc. | T107 | One of the exemplary instruments for soil temperature measurements. To be bought from several commercial companies. It is advisable to have a profile of soil temperature |
| Thermohygrometer | Vaisala Oyj | HMP155 | One of the exemplary instruments for air temperature and humidity measurements. To be bought from several commercial companies. Remember to place it inside radiation shield at similar height as the EC system. |
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Cite This Article
Ziemblińska, K., Urbaniak, M., Dukat, P., Olejnik, J. Measurements of CO2 Fluxes at Non-Ideal Eddy Covariance Sites. J. Vis. Exp. (148), e59525, doi:10.3791/59525 (2019).