Gross Direct and Embodied Carbon Sinks for Urban Inventories

Cities and urban regions are undertaking efforts to quantify greenhouse (GHG) emissions from their jurisdictional boundaries. Although inventorying methodologies are beginning to standardize for GHG sources, carbon sequestration is generally not quantified. This article describes the methodology and quantification of gross urban carbon sinks. Sinks are categorized into direct and embodied sinks. Direct sinks generally incorporate natural process, such as humification in soils and photosynthetic biomass growth (in urban trees, perennial crops, and regional forests). Embodied sinks include activities associated with consumptive behavior that result in the import and/or storage of carbon, such as landfilling of waste, concrete construction, and utilization of durable wood products. Using methodologies based on the Intergovernmental Panel on Climate Change 2006 guidelines (for direct sinks) and peer‐reviewed literature (for embodied sinks), carbon sequestration for 2005 is calculated for the Greater Toronto Area. Direct sinks are found to be 317 kilotons of carbon (kt C), and are dominated by regional forest biomass. Embodied sinks are calculated to be 234 kt C based on one year's consumption, though a complete life cycle accounting of emissions would likely transform this sum from a carbon sink to a source. There is considerable uncertainty associated with the methodologies used, which could be addressed with city‐specific stock‐change measurements. Further options for enhancing carbon sink capacity within urban environments are explored, such as urban biomass growth and carbon capture and storage.     

The influence of rapid urbanization and land use changes on terrestrial carbon sources/sinks in Guangzhou,China

Complex changes in carbon sources and sinks caused by rapid urbanization have been observed with extensive changes in the quantity, structure, and spatial pattern of land use types. Based on the modified Carnegie-Ames-Stanford Approach model and on gray relational analysis, we analyzed the influence of land use changes on carbon sinks and emissions in Guangzhou from 2000 to 2012. The aim was to identify suitable options for built-up land expansion that would allow for minimal carbon losses. The key results were as follows: (1) Built-up land increased by 118.91% in Guangzhou city over the study period, with this expansion taking the form of concentric circles extending around the old Yuexiu district. (2) Carbon emissions over the period of analysis significantly exceeded carbon sink capabilities. The total carbon sink decreased by 30.02%, from 535.40 × 10³ t to 374.6 × 10³ t. Total carbon emissions increased by 1.89 times, from 13.73 × 10⁶ t to 39.67 × 10⁶ t; 80% of carbon emissions were derived from energy consumption. (3) There were large differences in the extent of carbon sink losses at different scales of built-up land expansion and land use change. In Guangzhou, the loss of carbon sink is small when cultivated land (though not prime farmland) and water bodies are converted to built-up land on a small scale. The loss of carbon sink is much smaller when grasslands are converted to built-up land on a large scale. However, forested land, which has excellent carbon sink functions, should not be converted. (4) Changes in carbon sinks were mainly affected by natural factors and land urbanization. Changes in carbon emissions were mainly affected by population urbanization, economic urbanization, and land urbanization. (5) To achieve “economical and intensive use of land”, “urban growth boundary” and “ecological red lines” should be determined for government policies on land use management. These factors have great significance for “increasing carbon sinks and reducing carbon emissions” in urban ecological systems.     

Defining (Urban) Producer and Consumer Sinks

This contribution was prompted by the article “Gross Direct and Embodied Carbon Sinks for Urban Inventories” by Mohareb and Kennedy published in this issue. The authors define two types of urban carbon sinks—direct and embodied—and discuss their relation to producer and consumer emissions (and sinks) accounting. This commentary continues that discussion by clarifying boundary considerations and definitions between producer and consumer sinks, and between direct and indirect sinks. Extending the notion of production‐ versus consumption‐based emissions accounting, a corollary for producer and consumer sinks can be drawn. Producer sinks would include direct sequestration through industrial and private activities occurring within a defined territory. Consumer sinks would refer to direct and indirect sequestration activities associated with the consumption of goods and services within the same territory, wherever that sequestration may occur. As with emissions accounting, in carbon sinks accounting I propose that the exact categorization depends on the perspective taken. Clear boundaries and well‐defined terminology—historically present in emissions accounting—are critical to this novel approach to sinks accounting.     

石灰碳汇综述

以“碳失汇”科学之谜和碳捕集与封存技术发展为背景,从石灰碳化原理、影响因素和石灰在化工、冶金、建筑以及石灰窑灰处理等领域的利用方式,综述了石灰物质流动过程的碳汇研究.结果发现: 石灰材料和环境条件是影响碳化的主要因素;石灰碳汇主要集中在化工、冶金和建筑领域;已有研究侧重分析石灰碳汇的机理、影响因素,但缺乏系统的碳汇核算方法.今后的研究工作应从以下几方面加强: 从物质流动的角度出发,建立系统完整的石灰碳汇核算方法;量化我国乃至全球的石灰碳汇量,阐明石灰生产过程中排放的CO₂抵消比例;分析石灰碳汇对碳失汇的贡献比例,明晰部分失踪碳汇;推动石灰碳捕集与封存技术发展,为我国应对气候变化国际谈判提供科学依据.     

基于建筑容量的城市建设用地碳汇量核算方法

城市建设中的矿物质材料开发利用活动不仅导致大量碳排放,也产生了碳吸收.以往建筑矿物质材料的碳吸收过程一直没有得到重视和科学量化.本研究采用遥感影像阴影高度反演技术,提取地块的建筑容量,识别建筑类型,以此为依据确定矿物材料用量及碳含量参数,采用热重分析法测定碳化率,基于以上步骤构建城市建筑碳汇量的核算方法,并选取沈阳市蒲河新来测试这一核算方法,同时进行不确定性分析.结果表明: 1996—2016年,沈阳市蒲河新城各类型建筑产生的碳汇总量依次为:居住建筑>公共服务建筑>其他类建筑>商业金融建筑>工业建筑;各类建筑用地的碳汇容积率依次为:商业金融建筑>居住建筑>公共服务建筑>其他类建筑>工业建筑.本研究构建的基于建筑容量提取的城市尺度的建筑碳汇量核算方法,可以快速准确地估算不同类型城市建设用地无机材料产生的碳汇量.在城市自然碳汇有限条件下,利用建筑碳汇增加城市碳汇量,能够为我国城市低碳发展提供新的思路.     

双碳战略背景下城市生态系统的碳汇功能与生物多样性可以兼得

“碳达峰、碳中和”是中国对世界的庄严承诺, 也是当前指导我国可持续发展的重要战略。碳排放的空间分布表明, 城市及其周边地区是最主要的碳排放区。随着我国的城市化进程不断推进, 如何有效减少城市碳排放、增加碳汇成为关系着双碳战略成效的关键问题。作为城市空间中唯一的自然碳汇, 城市绿地生态系统的固碳增汇作用日益突出。加强城市绿地的碳汇建设, 如果按照传统的人工营建思路, 只种植在当前情景下碳汇能力强的少数植物种则很可能会减少生物多样性。基于植物分配有限资源时存在权衡关系的生态学一般原理, 不仅选取当前情景下碳汇能力强的植物, 还要考虑适应环境变化、在未来环境下碳汇能力强的植物, 以及遭遇极端环境时有一定碳汇能力的植物。在此框架下, 选取恰当的植物多样性组合有望实现更好的城市绿地碳汇功能, 即环境稳定时碳汇能力更强, 环境变化时碳汇能力更稳, 出现极端事件时碳汇损失更小。具体的做法包括: (1)扩展绿地物种库信息, 纳入植物的碳减排能力、适应环境变化能力、应对极端变化能力等信息; (2)考虑植物在碳汇能力与应对气候变化能力之间的权衡关系, 将植物分成不同类型的组, 比如高碳汇低适应、低碳汇高适应; (3)根据不同城市的环境和未来气候变化特点, 因地制宜地选择恰当植物组合营建城市绿地; (4)开展城市绿地建设的全生命周期碳计量, 以近自然方式营建和管养城市绿地, 减少管护过程的碳排放。这些举措有助于实现城市绿地碳汇能力提升与生物多样性保护的双重目标。城市生态系统的‌结构与功能共赢, 对落实双碳战略和生态文明建设意义重大。     

Land use effects on terrestrial carbon sources and sinks

Current and past land use practices are critical in determining the distribution and sizeof global terrestrial carbon (C) sources and sinks. Although fossil fuel emissions dominate the an-thropogenic perturbation of the global C cycle, land use still drives the largest portion of anthropo-genic emissions in a number of tropical regions of Asia. The size of the emission flux owing to landuse change is still the biggest uncertainty in the global C budget. The Intergovernmental Panel on Climate Change (IPCC) reported a flux term of 1.7 PgC·a~(-1) for 1990-1995 but more recent es-timates suggest the magnitude of this source may be only of 0.96 PgC·a~(-1) for the 1990s. In add-ition, current and past land use practices are now thought to contribute to a large degree to the northern hemisphere terrestrial sink, and are the dominant driver for some regional sinks. However,mechanisms other than land use change need to be invoked in order to explain the inferred C sink in the tropics. Potential candidates are the carbon dioxide (CO_2) fertilization and climate change;fertilization due to nitrogen (N) deposition is believed to be small or nil. Although the potential formanaging C sinks is limited, improved land use management and new land uses such as refores-tation and biomass fuel cropping, can further enhance current terrestrial C sinks. Best manage-ment practices in agriculture alone could sequester 0.4-0.8 PgC per year in soils if implemented globally. New methodologies to ensure verification and permanency of C sequestration need to be developed.     

Land use effects on terrestrial carbon sources and sinks

Current and past land use practices are critical in determining the distribution and size of global terrestrial carbon (C) sources and sinks. Althoughfossil fuel emissions dominate the anthropogenic perturbation of the global C cycle, land use still drives the largest portion of anthropogenic emissions in a number of tropical regions of Asia. The size of the emission flux owing to land use change is still the biggest uncertainty in the global C budget. The Intergovernmental Panel on Climate Change (IPCC) reported a flux term of 1.7 PgC@a-1 for 1990-1995 but more recent estimates suggest the magnitude of this source may be only of 0.96 PgC@a-1 for the 1990s. In addition, current and past land use practices are now thought to contribute to a large degree to the northern hemisphere terrestrial sink, and are the dominant driver for some regional sinks. However, mechanisms other than land use change need to be invoked in order to explain the inferred C sink in the tropics. Potential candidates are the carbon dioxide (CO2) fertilization and climate change; fertilization due to nitrogen (N) deposition is believed to be small or nil. Although the potential for managing C sinks is limited, improved land use management and new land uses such as reforestation and biomass fuel cropping, can further enhance current terrestrial C sinks. Best management practices in agriculture alone could sequester 0.4-0.8 PgC per year in soils if implemented globally. New methodologies to ensure verification and permanency of C sequestration need to be developed.     

陆地生态系统碳汇评估方法研究进展

“碳中和”是我国作出的一项重大的国家战略决策,陆地生态系统碳汇作为碳增汇的重要组成部分,在碳中和目标实现的过程中发挥着重要的作用。但当前基于不同观测数据和方法的陆地碳汇计算仍有很大的不确定性,为了全面了解陆地生态系统碳汇分布特征,提高陆地生态系统碳汇评估的准确性,梳理了近年来关于陆地生态系统碳汇评估的国内外研究进展,从“自下而上”和“自上而下”两类途径阐述了陆地生态系统碳汇评估的主要方法(样地清查法、涡度相关法、模型模拟法和碳同化反演法)的主要原理和特征,优势和缺陷,及在不同尺度碳汇研究中的应用,并从土地利用/覆盖变化、气候因素(大气CO₂浓度、氮沉降)、环境因素(太阳辐射、温度、降水)等因素阐述了陆地系统碳汇主要驱动因子;分析了我国陆地生态系统碳汇的主要特征及时空变化趋势,并从人类活动(生态工程)和环境因素阐述了中国陆地生态系统碳汇的驱动因素;最后,展望了新的监测手段和评估方法在提升陆地生态系统碳汇评估精度中的作用,从而更好的服务于我国“碳中和”的长远目标。     

我国主要海域海水养殖碳汇能力评估及其影响效应——基于我国9个沿海省份面板数据

随着海水养殖业的碳汇功能逐渐被认识和肯定,海水养殖不再单是一项经济活动,而是对环境具有正向影响的碳汇生态活动。以我国沿海9个省份为例,选取海水养殖业碳汇主要贡献的贝类和藻类海产品,并按照各自的碳汇方式对我国沿海地区2008—2015年海水养殖碳汇能力测算,进一步将9个沿海省份按照主要海域划分为渤海、黄海、东海、南海,利用LMDI模型从海水养殖的结构效应和规模效应角度分析碳汇能力的区域差异和主要影响因素。研究结果显示,黄海沿岸海水养殖碳汇能力最强,南海沿岸海水养殖的碳汇转化比例最高,规模效应与我国沿海地区海水养殖碳汇能力始终呈正相关,结构效应的作用显著但不稳定。基于上述结论,我国沿海地区碳汇养殖业应首先提升碳汇养殖技术、稳定海水养殖产量,其次注重优化养殖结构,对碳汇潜力巨大的贝类多加关注。     

土壤有机碳汇内涵与核算方法辨析

在"碳达峰、碳中和"战略需求下,土壤有机碳汇作为生态系统碳汇的重要组成部分,土壤碳库容量以及如何开展土壤有机碳汇核算日益成为生态碳汇的研究热点。梳理了国内外土壤有机碳汇及核算相关研究成果,解析了土壤有机碳汇的概念内涵,提出了以稳定性有机碳作为土壤有机碳汇的表征指标及获取方法。从土壤发生学角度提出了土壤碳汇阈值的概念,土壤中有机碳的含量随着分解转化最终会达到动态平衡,此时稳定有机碳含量值约是常数,这个常数就是稳定碳库的库容,在特定的成土因素下,碳库的核算值不会超过平衡时的常态值。在客观上,体现在非人类干扰状态下不同土壤类型自然状态下的稳定性有机碳含量。参照土壤有机质平衡理论,提出了土壤碳汇核算的定量化方法,为土壤碳汇的度量和核算提供了一套技术思路。下一步土壤有机碳汇的核算应在科学研究基础上多角度凝聚共识,制定碳汇核算标准,确定不同尺度下可操作、可重复以及可复制的土壤有机碳汇核算技术与方法。     

排放与森林碳汇作用下云南省碳净排放量估计

以云南省为例,用马尔科夫链计算能源结构,在经济增长模型基础上基于动态最优化理论估计能源消费碳排放,并基于CO₂FIX模型计算云南省森林碳汇,预测在能源消费碳排放和森林碳汇共同作用下的从2008到2050年碳净排放量。研究发现云南省能源消费碳排放量和碳净排放量曲线都呈"倒U"型,在2035年达到高峰,高峰值分别为和129.71 MtC和118.89 MtC;在森林碳汇中,原有森林的碳汇作用在现在和未来一段时间内处于主导地位,但新造林有着巨大的碳汇潜力,所以在保护原有森林的同时要植树造林,从生态学角度抵消碳排放;森林碳汇只能减少小部分碳排放,更主要的是改善云南省的能源结构,加快技术进步速度,开发水电等新能源,从根本上减少温室气体的排放。     

省域视角下中国森林碳汇空间外溢效应与影响因素

森林碳汇空间相关性与溢出效应对林业产业的区域统筹发展具有重要作用,科学核算各地区的森林碳汇量并分析其空间关联特征是制定差异化碳汇发展政策的重要基础。以森林蓄积量扩展法核算我国31个省(市、自治区)1993—2018年6次森林资源清查期间的森林碳汇量,探究省域间森林碳汇量的相关性特征,并利用空间计量模型分析森林碳汇的外溢效应和影响因素。结果表明：(1)我国整体森林碳汇量不断增加,不同地区的森林碳汇量差别较大。西南省份和东北林区森林碳汇量处于第一梯队,上海和北京碳汇增速较快。(2)研究期间内的Moran′s I指数先呈现倒“V”形的变化特征,之后又以较为稳定的趋势上升,我国各地区的森林碳汇分布存在显著的空间关联性。(3)森林碳汇的空间外溢效应显著,根据空间杜宾模型将外溢效应分解为直接效应、间接效应和总效应。林业管理水平和森林蓄积水平对本地和相邻地区森林碳汇量有正向影响,林业产业发展水平对本地区的森林碳汇量有负向影响。综上,我国各地方政府对差异化林业碳汇政策的制定和执行应兼顾区域因素,以我国林业政策的总体空间规划来综合统筹各区域森林政策,在“山水林田湖草沙”的命运共同体理念引领下,实现林业的...     

天然林保护工程区近20年森林植被碳储量动态及碳汇(源)特征

分析近20年来天保工程区森林植被碳储量的动态变化及碳汇（源）特征,以期为我国天然林保护的政策制订和措施实施提供数据支撑。利用天然林资源保护工程区6-9次森林资源连续清查数据,把森林植被划分乔木林、灌木林、竹林、疏林地、散生木、四旁树,基于行业标准的生物量模型和碳计量参数、采用生物量加权平均法等方法,估算整个工程区和各省的森林植被总碳储量;对乔木林分起源、龄组、优势树种（组）估算碳储量和碳密度;量化森林植被总碳储量和乔木林碳储量随时间变化的消长,明确其碳汇/源特征。研究结果表明：6-9次清查,天保工程区森林植被总碳储量分别为2999 TgC、3254 TgC、3585 TgC和4097 TgC,年均增长率为1.65%、1.96%和2.70%;碳储量集中分布于我国东北和西南区域,其中四川碳储量最高,4期碳储量均占天保工程区总量20%以上;乔木林碳储量是森林植被碳储量的主体,每期占比均稳定在80%以上,其中天然林比例由94.67%下降至90.28%,人工林比例稳步上升,但到9次清查时其碳密度仍低于天然林50%;不同龄组间,中龄林碳储量最高,近熟林碳储量增长最快,碳密度从幼龄林到过熟林逐渐上升,4期趋势一致;乔木林中纯林碳储量占60%以上,大部分树种（组）碳储量和碳密度随时间推移而增加。7-9次清查,天保工程区森林植被总固碳量（当期相对于前期）分别为255.33 TgC、331.46 TgC和511.53 TgC,对全国森林植被总碳汇量的贡献由8次连清的53.78%上升到9次的67.46%,其中,乔木林对全国乔木林碳汇的贡献为68.71%;天保工程区内天然林对乔木林碳汇的贡献为75.90%;不同清查期,乔木林各龄组的碳汇变化较大,幼龄林和中龄林碳汇占比明显上升,近熟林和过熟林下降,9次清查时各龄组碳汇量大小顺序为：中龄林 > 近熟林 > 幼龄林 > 成熟林 > 过熟林;不同清查期,各个优势树种的碳汇/源表现不一,总体上,混交林的碳汇比例最大,到9次清查时,阔叶混交林和针阔混交林对乔木林碳汇的贡献分别为62.59%和17.23%,纯林中柏木碳汇贡献最大,为5.43%。天保工程区森林植被总碳储量随时间稳步增长,乔木林是总碳储量的主体,天然林是碳汇的主要来源,天然林保护增强了我国天然林碳汇的碳汇功能,促进了人工林碳汇作用提升,未来天保工程区碳汇潜力很大。     

石灰碳汇综述

以“碳失汇”科学之谜和碳捕集与封存技术发展为背景,从石灰碳化原理、影响因素和石灰在化工、冶金、建筑以及石灰窑灰处理等领域的利用方式,综述了石灰物质流动过程的碳汇研究.结果发现: 石灰材料和环境条件是影响碳化的主要因素;石灰碳汇主要集中在化工、冶金和建筑领域;已有研究侧重分析石灰碳汇的机理、影响因素,但缺乏系统的碳汇核算方法.今后的研究工作应从以下几方面加强: 从物质流动的角度出发,建立系统完整的石灰碳汇核算方法;量化我国乃至全球的石灰碳汇量,阐明石灰生产过程中排放的CO₂抵消比例;分析石灰碳汇对碳失汇的贡献比例,明晰部分失踪碳汇;推动石灰碳捕集与封存技术发展,为我国应对气候变化国际谈判提供科学依据.     

草地农业生态系统的碳平衡分析方法

根据草地农业生态系统的结构,它的碳平衡为4个生产层的碳平衡之和,也是3个界面的碳平衡之和,而某一生产层或者某一界面的碳平衡则是其固定、输入、排放和输出的碳之和。草地农业生态系统4个生产层的碳平衡分析方法定量重要生产环节的碳汇与碳源过程,便于草业生产改进碳汇管理;草地农业生态系统3个界面的碳平衡分析方法显示碳源和碳汇的发生机理,及其空间和数量关系,便于调控草业生产组分以增汇减排;但是,这两个方法不易区分碳的来源和去向,难以明确其利用效率。草地农业生态系统碳平衡分析的输入/输出法定量地指示碳的来源和去向,以及碳效率,计算简单,但是较为概括,不利于牧场尺度的草业碳汇管理。以中国祁连山甘肃马鹿牧场和澳大利亚塔斯玛尼亚奶牛牧场为例,用3种方法分析了两个牧场的碳平衡,结果表明,放牧管理的草业系统的主要碳源是休闲旅游、产品加工流通环节产生的温室气体,主要碳汇是草地和土壤中贮存的碳,好的草地管理可以增汇减排。     

Do grasslands act as a perpetual sink for carbon?

It is increasingly commonly suggested that grasslands are a perpetual sink for carbon, and that just maintaining grasslands will yield a net carbon sink. I examine the evidence for this from repeated soil surveys, long term grassland experiments and simple mass balance calculations. I conclude that it is untenable that grasslands act as a perpetual carbon sink, and the most likely explanation for observed grassland carbon sinks over short periods is legacy effects of land use and land management prior to the beginning of flux measurement periods. Simply having grassland does not result is a carbon sink, but judicious management or previously poorly managed grasslands can increase the sink capacity. Given that grasslands are a large store of carbon, and that it is easier and faster for soils to lose carbon that it is for them to gain carbon, it is an important management target to maintain these stocks.     

低碳导向下土地覆被演变模拟——以深圳市为例

全球碳排放水平的不断增加引起的全球变暖越发严重,导致了严重的自然灾害和经济损失,这种失衡发展的态势促使着各个国家开始探索低碳环保的发展模式。为了探究何种土地利用组成可以更好的为低碳城市服务,以深圳市为研究区,结合2020年土地利用现状结构和2020年土地利用规划结构分别估算出碳汇最大化情景和碳排放量最小化情景下2020年各土地利用类型的数量结构,并运用FLUS模型模拟出深圳市土地利用类型在这两种情景下的空间分布特征。最后,从碳密度和碳排放视角对比这两种情景的低碳效益。研究结果如下：①碳汇最大化和碳排放最小化情景下土地利用总碳盈余均比2020年少,且碳汇最大化情景下土地利用总碳盈余最小。碳汇最大化情景下耕地、园地和林地面积增加而水域和建设用地减少,碳排放最小化情景下园地和林地面积增加来源于草地、水域和建设用地的减少,这两种低碳情景的碳汇能力增强而碳排放量减少;②碳汇最大化和碳排放最小化情景下林地明显增加故而土地利用总碳盈余均比实际情景小,而园地和草地的缩减和扩张是引起两种低碳情景碳密度和碳排放量有差异的主要原因。碳汇最大化和碳排放最小化情景下,西部和东南部主要是碳密度增加和碳排放减少的区域,而中部是碳密度减少和碳排放增加的区域。因此对中部区域进行重点调控,有利于深圳市碳中和和碳达峰的实现。研究可以为深圳的低碳发展提供规划建议,同时给其他区域的低碳规划提供参考意见。     

江西省森林碳蓄积过程及碳源/汇的时空格局

森林碳蓄积是研究森林与大气碳交换以及估算森林吸收或排放含碳气体的关键参数,不同年龄森林的碳源/汇功能差异则体现出森林生态系统碳蓄积过程的时间特征。以森林资源清查的样方数据作为数据源,通过刻画主要树种的林分蓄积生长曲线、林龄与净初级生产力(NPP)之间的关系,驱动区域碳收支模型(InTEC)模拟江西省1950—2008年的森林碳蓄积过程,了解山江湖工程实施以来的森林碳源/汇状况。结果表明,20世纪80年代以前,江西省森林年平均NPP波动于450—813 gCm-2a-1之间,年净增生物量碳26.55—36.23 TgC/a,年净增木质林产品碳0.01—0.3 TgC/a;80年代初,NPP和年净增生物量碳分别降至307.39 gC m-2a-1和17.31 TgC/a,而年净增木质林产品碳却高达0.6 TgC/a,说明森林被大量砍伐进入林产品碳库;1985年山江湖工程实施后,大面积造林使得年净增碳蓄积呈现急剧上升趋势,生物量和木质林产品碳蓄积分别上升至目前的42.37 TgC/a和0.79 TgC/a,而平均NPP值增加缓慢、碳汇功能降低,说明林分质量有待提高;90年代后碳汇功能开始稳步增强,说明造林面积的迅速增加是引起江西省森林碳增汇的主要驱动因素,但未来森林增汇潜力应源于森林生长和有效的经营管理。     

牡蛎礁生境：海岸带可持续发展的潜在碳汇

牡蛎礁生境是指由聚集的牡蛎和其他生物及环境堆积形成的复合生态系统,其固碳和储碳潜力巨大,在海岸带生态系统中发挥着重要的作用。然而,目前对牡蛎礁生境碳源与汇的认识仍存在不足,主要在于牡蛎钙化和呼吸作用都释放CO₂,而碳源与汇的评估忽视了钙化、同化和沉积过程带来的整体碳汇价值及牡蛎礁生态系统功能带来的碳汇效应。因此,有必要重新认识牡蛎礁生境的碳汇价值。一方面,牡蛎礁生境的碳源和碳汇需要从牡蛎礁自身的整体碳循环中进行评估,包括牡蛎礁系统中的沉积、钙化、呼吸作用及侵蚀、再悬浮和再矿化作用; 另一方面,牡蛎礁生态系统服务引起的碳汇效应需从牡蛎礁的生态系统服务价值角度进行评估,将生态系统服务价值及碳价值进行关联,从而纳入碳汇核算体系。从实现海岸带可持续增汇角度出发,综述了牡蛎礁生境中碳的源与汇;阐述了容易被人们忽视的微生物在牡蛎礁生境碳汇中的作用;以保护和生态修复为目的,进一步提出可实现牡蛎礁生境最大潜在碳汇的策略,以期为实现海洋负排放及践行"国家双碳战略"提供理论和技术支撑。