三峡库区森林生态系统有机碳密度及碳储量

森林生态系统作为陆地生态系统的重要组成部分,在减缓全球气候变化过程中发挥重要作用.基于104块样地调查和森林资源二类清查数据,运用GIS平台,对三峡库区森林生态系统有机碳密度及储量进行研究,结果表明:(1)三峡库区森林优势树种各器官的含碳率为44.59%～54.45%,森林凋落物含碳率为30.61%～42.73%,平均为36.38%;(2)三峡库区森林生态系统平均碳密度为117.68t · hm-2,低于我国森林平均水平;植被层碳密度平均为24.15 t · hm-2,其中常绿阔叶林植被层碳密度最高,达42.80 t · hm-2;枯落物层平均碳密度为2.74 t · hm-2,土壤有机碳密度平均为9.09 kg · m-2;(3)三峡库区森林生态系统总有机碳储量为286.14×106t,其中植被层碳储量为58.72×106t,凋落物碳储量为6.67×106t,土壤碳储量为220.74×106t;(4)三峡库区马尾松林分布面积最大,其总有机碳储量为77.24×106t,占三峡库区森林有机碳总储量的26.99%;在各森林类型中,马尾松林植被层、凋落物层和土壤层有机碳储量均最高,分别达到20.70 × 106t、2.66×106t和53.89×106t;(5)三峡库区森林有机碳密度呈现\"东高西低\"分布格局,巴东-秭归、巫山-巫溪、石柱-武隆及江津南部有机碳密度较高.在三峡库区提高森林质量、扩大森林面积是增强森林生态系统碳汇功能的有效途径.     

陆地生态系统可溶性有机氮研究进展

可溶性有机氮(dissolved organic nitrogen DON)的流动是陆地生态系统氮循环的重要组成部分。本文就陆地生态系统DON的来源、组成、性质;森林生态系统DON的流动、季节动态以及DON在氮循环中的地位等方面作了概括和探讨。今后的陆地生态系统DON的研究应该集中在以下几个方面：确定陆地生态系统中DON的各分室DON的浓度、流量;DON的源与汇问题;量化不同生态系统中DON库的大小和组成;研究DON在氮的矿化、微生物的固持、以及植物吸收等氮循环过程中的地位;对比研究DON与DOC(dissolved organic carbon)的动态差别;探讨DON与植物营养和碳积累的关系等。     

我国森林生态系统碳储量和碳平衡的研究方法及进展

森林在全球碳循环中起着十分重要的作用。从现存生物量的角度出发,综述了我国森林生态系统碳储量和碳平衡研究采用的主要方法及手段,以及在该领域的研究现状,并从实际情况出发探讨我国未来研究的发展趋势和亟待解决的一些问题。     

六盘山四种森林生态系统的碳氮储量、组成及分布特征

碳和氮是森林生态系统的重要组成元素,其含量有很大时空差异,并和立地及森林特征关系很大,需做大量的积累性调查才能得到其变化规律,尤其是加强在过去较少研究的西北地区的调查。在宁夏六盘山区选择华北落叶松(Larix principisrupprechtii)人工林、华山松(Pinus armandii)次生林、桦木(Betula platyphylla)次生林和野李子(Prunus salicina)灌丛4种典型森林,测定了乔木层(分不同器官)、灌木层、草本层、枯落物层、根系层(0—100 cm土壤)的碳、氮含量,分析了生态系统的碳、氮储量及成分组成和层次分布特征。结果表明,碳含量在不同乔木树种及其不同器官之间的差异不明显;但氮含量存在显著的树种差别和器官差异,以树叶的最高、树干的最低。灌木层和草本层的碳氮含量均表现为地上部分地下部分。各森林样地的乔木层、灌木层、草本层的碳含量依次降低,但氮含量依次增高;枯落物层的碳含量低于各植被层,但氮含量高于各植被层;根系层土壤的碳、氮含量则随土层增深而递减。包括活植被层、枯落物层和根系层土壤在内的华北落叶松人工林、华山松次生林、桦木次生林、野李子灌丛的生态系统碳储量依次为364.56、450.98、640.02、196.55 t/hm2,氮储量依次为27.86、36.19、47.02、15.99 t/hm2。所有4种森林生态系统的根系层土壤的碳氮储量均占整个生态系统总储量的绝大部分,其比例对碳储量为84.69%—93.92%,氮储量为98.09%—98.64%。从乔木层、灌木层、草本层、枯落物层到根系层(土壤),呈现出C/N比依次减小的趋势;根系层土壤和整个生态系统的C/N比分别为华北落叶松林的11.84和13.12、华山松林的10.76和12.56、桦木林的12.48和13.52、野李子灌丛的11.70和12.29。     

森林演替在南亚热带森林生态系统碳吸存中的作用

研究了鼎湖山南亚热带森林同一演替系列中3个不同演替阶段(马尾松针叶林、马尾松荷木混交林和季风常绿阔叶林)生态系统碳贮量和分配格局特征,并探讨了该地区森林演替过程中生态系统碳吸存潜力和速度。结果表明:(1)针叶林各组分碳素含量高于阔叶林对应组分的碳素含量(后者是前者的72.0%～94.5%)。两个森林植物碳素含量,不同层次比较,均为乔木层>灌木层>草本层,不同器官比较,以根或干最高。(2)乔木层生物量随森林演替进展而增加。针叶林、混交林和阔叶林乔木层生物量分别为:143.5t/hm2、270.1t/hm2和407.8t/hm2,其中大部分由干和皮组成(各器官占乔木层生物量的比例平均为:叶2.8%、枝19.3%、干和皮混合57.0%、根20.9%)。林下层生物量为4.23～14.10t/hm2,是乔木层的1.0%～9.8%,随森林演替进展而减少。(3)土壤容重随深度增加而增加,但随森林演替进展而减少。与土壤容重相反,土壤有机碳含量随深度增加而明显减少,但随森林演替进展而增加。(4)3种类型森林生态系统碳总贮量分别为135.8t/hm2、215.1t/hm2和259.7t/hm2。生态系统碳贮量在各组分的格局十分相似,植被、土壤和凋落物层所占比例均分别约为67.6%、30.2%和2.2%。与其它地带森林比较,鼎湖山保护区森林植被与土壤碳贮量之比和表层(0～20cm)的土壤碳占整个     

森林生态系统可溶性碳和颗粒碳通量

可溶性碳(Dissolved carbon,DC)和颗粒碳(particulate carbon,PC)通量作为森林生态系统碳收支的重要组分,在森林固碳功能的评价和模型预测中具有重要意义,但常因认识不足、测定困难等而在森林碳汇研究中被忽略。综述了森林生态系统DC和PC的组成、作用、相关生态过程及其影响因子,并展望了该领域应该优先考虑的研究问题。森林生态系统DC和PC主要包括可溶性有机碳、可溶性无机碳和颗粒有机碳,主要来源于生态系统的净初级生产量。DC和PC是森林土壤的活性碳库,主要以大气沉降、穿透雨和凋落物的形式输入森林土壤系统,并通过土壤呼吸、侧向运输及渗透流失的方式输出生态系统。从局域尺度看,DC和PC通量受根系分泌、细根分解、微生物周转等生物过程的影响较大;从区域尺度看,它们受土壤和植被特性、生态过程耦联关系、气候因子以及全球变化的综合影响。该领域应该优先考虑:(1)探索不同时空尺度下森林生态系统DC和PC通量的控制因子及其耦联关系,揭示其中的驱动机理;(2)探索DC和PC与其它森林生态系统碳组分的相互关系及转化,阐明DC和PC通量与其它养分之间潜在的生态化学计量关系;(3)探索全球变化,特别是人类活动(如森林经营)和极端干扰事件(如林火、旱涝、冰冻、冻融交替等)对森林生态系统DC和PC通量的影响。     

我国主要森林生态系统炭贮量和碳平衡

在广泛收集资料的基础上,估算了我国主要森林生态系统的碳贮量和碳平衡通量,分析了它们的区域特征。主要结果如下：１）我国森林生态系统的平均碳密度是２５８．８３ｔ．ｈｍ＾－２,基本趋势是随纬度的增加而增加;其中植被的平均碳密度是５７．０７ｔ．ｈｍ＾－２,随纬度的增加而减少;土壤碳密度约是植被碳密度的３．４倍,其区域特点与植被碳密度呈相反趋势,随纬度升高而增加;凋落物层平均碳密度是８．２１ｔ．ｈｍ＾－２,     

飓风和台风对沿海地区森林生态系统的影响

飓风和台风是影响热带和温带沿海区域的主要灾害性气候之一,飓风和台风对于森林生态系统的影响是生态学关注的课题。综述了飓风和台风登陆对于森林生态系统树木和林分的危害影响形式及主要影响因素,着重举例阐述了树种和森林类型是影响台风危害程度的一个重要因素。分析了目前国际上开展的关于飓风和台风登陆对于森林生态系统碳、氮循环的影响,结果表明飓风、台风干扰导致的森林凋落物输入量、凋落物分解速率以及森林碳储存量动态变化较为复杂,与森林类型、林分空间位置以及台风过后的时间段密切相关。飓风引起的森林受损的恢复途径和机理与树冠受损严重程度直接相关,并受到光和水分条件的影响,及时的开花、结果以及充足的土壤种子库对森林植被恢复具有促进作用。在景观和区域尺度量化飓风和台风对沿海地区森林生态系统的影响也日益引起关注,在这方面,整合气象数据、遥感数据和地面调查的模型模拟方法起到重要的作用。今后应加强对于我国东南沿海地区森林生态系统遭受台风影响损失的生态监测和长期定位研究,加强关于台风对于不同森林生态系统类型和不同树种的危害形式和危害程度的研究,以及台风对于森林生态系统碳、氮循环影响的研究,弥补我国在以上领域的空白。     

中国森林生态系统中植物固定大气碳的潜力

1　前　言在引起全球温室效应的痕量气体中 ,尤以含Ｃ气体的作用最为显著。ＣＯ2 和ＣＨ4两种含碳气体的贡献将达到 75 %[1] 。而且 ,在大气中这两种气体的浓度正在不断增加[2 ] 。为了弄清大气中这些含碳痕量气体的来源和归宿 ,首先应该搞清楚全球主要碳库的现有贮量及其潜力。森林是全球陆地生态系统中的最大有机碳库 ,它贮有1 1 4 6ＰｇＣ ,占整个陆地碳库的 5 6%[3] 。而且更重要的是森林生态系统具有较高的碳贮存密度(ｃａｒｂｏｎｄｅｎｓｉｔｙ ,即与别的土地利用方式相比 ,单位面积内可以贮存更多量的有机碳 )。据研究 ,森林生态系…     

辽东山区典型森林生态系统碳密度

以辽东山区典型森林生态系统为研究对象,通过系统的样地调查并结合辽宁省2009年森林资源二类调查资料,利用异速生长方程和植被类型法对典型森林生态系统不同组分碳密度及碳储量进行估算.结果显示,辽东山区森林生态系统碳密度为300.050Mg· hm-2,各层碳密度的大小顺序为:土壤层(232.452 Mg·hm-2)＞乔木层( 63.237Mg · hm-2)＞凋落物层(3.529 Mg·hm-2)＞灌木层(0.558 Mg · hm-2)＞草本层(0.274Mg·hm-2).乔木层碳密度随着林龄的增加而增大,灌木层碳密度随着林龄的增加而减小,土壤、草本和凋落物层碳密度在不同龄组间的变化没有明显的规律性.辽东山区305.852×104 hm2的生态系统碳储量为917.709 Tg C,其中生物量碳储量为206.751Tg C,土壤碳储量为710.959 Tg C,土壤碳储量是生物量碳储量的3.44倍.通过比较本次调查结果与以往研究结果发现,利用森林清查资料,由于低估了幼龄林的乔木碳密度,导致辽东山区的乔木碳储量低估,且以往研究中用简单的换算系数高估了林下植被碳密度,但远低估了土壤碳密度.     

华南典型树种凋落叶的野外分解和溶解性有机质溶出动态

选用华南亚热带地区常见阔叶树种木荷和针叶树种湿地松的新近凋落叶,在野外分解0、30、60、90、150、210、240、365 d,分析溶出的溶解性有机质(DOM)浓度、组成和性质的变化,以及对土壤可溶性有机碳(DOC)的影响.结果表明: 随着分解的进行,尽管木荷叶片的DOM浓度高于松针,但是2种凋落叶DOM浓度、性质和物质组成变化规律一致;2种凋落叶的DOM浓度均呈下降趋势,芳香化程度和分子量增大,富里酸、腐殖酸类物质逐渐增多,可降解的简单芳烃蛋白(如酪氨酸)逐渐减少.在分解初期,DOM主要由亲水中性和酸性部分组成,易分解、易迁移,对表层土壤DOC影响不显著;在分解后期,DOM主要为腐殖酸和富里酸类物质,吸附性强,表层土壤DOC浓度显著下降.     

吉安地区典型景观湖泊浮游植物群落特征及其与水环境因子的关系

2012年8月至2013年7月,对吉安地区将军湖、龙湖、庐陵湖和挹翠湖4个景观湖泊水体浮游植物群落及其主要水环境因子进行了调查,并利用生物多样性指数法(Shannon指数H、Margalef指数D和Pielou指数J)和主成分分析(PCA)法分别对湖泊水质和水环境因子进行了评价。结果表明:4个湖泊共鉴定浮游植物7门82属163种,主要优势种为硅藻或绿藻;浮游植物细胞丰度呈季节性变化,秋夏居高,冬春季偏低,平均丰度变化范围为25.45×10~6~54.04×10~6cells·L~(-1);将军湖、龙湖、庐陵湖和挹翠湖的H值分别为1.26~2.08、1.82~2.61、2.27~2.62和1.10~2.32;D值分别为2.03~3.51、2.36~3.71、2.48~3.93和3.12~3.96;J值分别为0.45~0.69、0.59~0.80、0.67~0.77和0.50~0.84。综合评价结果显示,4个湖泊处于富营养化状态、中等污染水平。而对污染较重的庐陵湖水环境因子PCA分析结果表明,水温(WT)、溶解氧(DO)和总氮(TN)是影响小型封闭景观水体浮游植物群落变化的主要因素。建议对小型封闭景观水体进行必要的治理和生态修复。     

杉木人工林土壤可溶性有机质及其与土壤养分的关系

通过在福建省来舟林场对不同栽植代数杉木人工林土壤可溶性有机碳(DOC)和氮(DON)及土壤养分的研究,其结果表明,随着杉木栽植代数的增加林地土壤DOC和DON含量逐渐下降,在0～10cm土层内第3代杉木林土壤DOC和DON含量分别是第1代杉木林的83.9%和87.1%、第2代杉木林的90.6%和96.9%,在10～20cm土层内第3代杉木林土壤DOC和DON含量分别是第1代杉木林的80.2%和81.5%、第2代杉木林的81.8%和90.0%。在不同林地和土层内土壤DOC含量之间的差异性达到了显著或极显著水平,而DON含量之间的差异性不显著。不同栽植代数杉木林土壤养分的变化趋势与DOM一致,随着杉木连栽,土壤养分含量呈下降趋势。在0～10cm土层内第3代杉木林土壤全氮、全钾、铵态氮和速效钾含量分别是第1代杉木林的83.1%、60.4%、68.1%和44.3%,是第2代杉木林的84.6%、68.5%、74.4%和58.7%;在10～20cm土层内第3代杉木林土壤全氮、全钾、铵态氮和速效钾含量分别是第1代杉木林的74.0%、53.4%、57.6%和54.6%,是第2代杉木林的94.8%、59.5%、74.3%和65.5%。经相关性分析,在各土层内土壤DOC和DON含量与土壤全氮、全钾、铵态氮和速效钾等土壤养分含量存在着不同程度的相关性。     

A stormflow/baseflow comparison of dissolved organic matter concentrations and bioavailability in an Appalachian stream

Patterns of dissolved organic carbon (DOC) and nitrogen (DON) delivery were compared between times of stormflow and baseflow in Paine Run, an Appalachian stream draining a 12.4 km² forested catchment in the Shenandoah National Park (SNP), Virginia. The potential in-stream ecological impact of altered concentrations and/or chemical composition of DOM during storms also was examined, using standardized bacterial bioassays. DOC and DON concentrations in Paine Run were consistently low during baseflow and did not show a seasonal pattern. During storms however, mean DOC and DON concentrations approximately doubled, with maximum concentrations occurring on the rising limb of storm hydrographs. The rapid response of DOM concentration to changes in flow suggests a near-stream or in-stream source of DOM during storms. Stormflow (4% of the time, 36% of the annual discharge) contributed >50% of DOC, DON and NO₃ ^– flux in Paine Run during 1997. In laboratory bacterial bioassays, growth rate constants were higher on Paine Run stormflow water than on baseflow water, but the fraction of total DOM which was bioavailable was not significantly different. The fraction of the total stream DOC pool taken up by water column bacteria was estimated to increase from 0.03 ± 0.02% h^–1 during baseflow, to 0.15 ± 0.04% h^–1 during storms. This uptake rate would have a minimal effect on bulk DOM concentrations in Paine Run, but storms may still have considerable impact on the bacterial stream communities by mobilizing them into the water column and by supplying a pulse of DOM.     

Production of Total Potentially Soluble Organic C, N, and P Across an Ecosystem Chronosequence: Root versus Leaf Litter

Dissolved organic matter (DOM) plays several important roles in forest ecosystem development, undergoing chemical, physical and/or biological reactions that affect ecosystem nutrient retention. Very few studies have focused on gross rates of DOM production, and we know of no study that has directly measured DOM production from root litter. Our objectives were to quantify major sources of total potentially water-soluble organic matter (DOM_tps) production, with an emphasis on production from root litter, to quantify and compare total potentially soluble organic C, N, and P (DOC_tps, DON_tps, and DOP_tps) production, and to quantify changes in their production during forest primary succession and ecosystem development at the Mt. Shasta Mudflows ecosystem chronosequence. To do so, we exhaustively extracted freshly senesced root and leaf and other aboveground litter for DOC_tps, DON_tps, and DOP_tps by vegetation category, and we calculated DOM_tps production (g m⁻² y⁻¹) at the ecosystem level using data for annual production of fine root and aboveground litter. DOM production from throughfall was calculated by measuring throughfall volume and concentration over 2 years. Results showed that DOM_tps production from root litter was a very important source of DOM_tps in the Mount Shasta mudflow ecosystems, in some cases comparable to production from leaf litter for DON_tps and larger than production from leaf litter for DOP_tps. Total DOC_tps and DON_tps production from all sources increased early in succession from the 77- to the 255-year-old ecosystem. However, total DOP_tps production across the ecosystem chronosequence showed a unique pattern. Generally, the relative importance of root litter for total fine detrital DOC_tps and DON_tps production increased significantly during ecosystem development. Furthermore, DOC_tps and DON_tps production were predominantly driven by changes in biomass production during ecosystem development, whereas changes in litter solubility due to changes in species composition had a smaller effect. We suggest that DOM_tps production from root litter may be an important source of organic matter for the accumulation of SOM during forest ecosystem development. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Shauna M. Uselman, Robert G. Qualls, and Juliane Lilienfein conceived of or designed the study and performed research. SMU analyzed data and wrote the article. SMU and RGQ contributed new methods or models.     

Composition,Dynamics, and Fate of Leached Dissolved Organic Matter in Terrestrial Ecosystems: Results from a Decomposition Experiment

Fluxes of dissolved organic matter (DOM) are an important vector for the movement of carbon (C) and nutrients both within and between ecosystems. However, although DOM fluxes from throughfall and through litterfall can be large, little is known about the fate of DOM leached from plant canopies, or from the litter layer into the soil horizon. In this study, our objectives were to determine the importance of plant-litter leachate as a vehicle for DOM movement, and to track DOM decomposition [including dissolve organic carbon (DOC) and dissolved organic nitrogen (DON) fractions], as well as DOM chemical and isotopic dynamics, during a long-term laboratory incubation experiment using fresh leaves and litter from several ecosystem types. The water-extractable fraction of organic C was high for all five plant species, as was the biodegradable fraction; in most cases, more than 70% of the initial DOM was decomposed in the first 10 days of the experiment. The chemical composition of the DOM changed as decomposition proceeded, with humic (hydrophobic) fractions becoming relatively more abundant than nonhumic (hydrophilic) fractions over time. However, in spite of proportional changes in humic and nonhumic fractions over time, our data suggest that both fractions are readily decomposed in the absence of physicochemical reactions with soil surfaces. Our data also showed no changes in the ¹³C signature of DOM during decomposition, suggesting that isotopic fractionation during DOM uptake is not a significant process. These results suggest that soil microorganisms preferentially decompose more labile organic molecules in the DOM pool, which also tend to be isotopically heavier than more recalcitrant DOM fractions. We believe that the interaction between DOM decomposition dynamics and soil sorption processes contribute to the ¹³C enrichment of soil organic matter commonly observed with depth in soil profiles. published online 2004     

Spatial, geomorphological, and seasonal variability of CDOM in estuaries of the Florida Coastal Everglades

This paper demonstrates the usefulness of fluorescence techniques for long-term monitoring and assessment of the dynamics (sources, transport and fate) of chromophoric dissolved organic matter (CDOM) in highly compartmentalized estuarine regions with non-point water sources. Water samples were collected monthly from a total of 73 sampling stations in the Florida Coastal Everglades (FCE) estuaries during 2001 and 2002. Spatial and seasonal variability of CDOM characteristics were investigated for geomorphologically distinct sub-regions within Florida Bay (FB), the Ten Thousand Islands (TTI), and Whitewater Bay (WWB). These variations were observed in both quantity and quality of CDOM. TOC concentrations in the FCE estuaries were generally higher during the wet season (June–October), reflecting high freshwater loadings from the Everglades in TTI, and a high primary productivity of marine biomass in FB. Fluorescence parameters suggested that the CDOM in FB is mainly of marine/microbial origin, while for TTI and WWB a terrestrial origin from Everglades marsh plants and mangroves was evident. Variations in CDOM quality seemed mainly controlled by tidal exchange/mixing of Everglades freshwater with Florida Shelf waters, tidally controlled releases of CDOM from fringe mangroves, primary productivity of marine vegetation in FB and diagenetic processes such as photodegradation (particularly for WWB). The source and dynamics of CDOM in these subtropical estuaries is complex and found to be influenced by many factors including hydrology, geomorphology, vegetation cover, landuse and biogeochemical processes. Simple, easy to measure, high sample throughput fluorescence parameters for surface waters can add valuable information on CDOM dynamics to long-term water quality studies which can not be obtained from quantitative determinations alone.     

Chemistry and Dynamics of Dissolved Organic Matter in a Temperate Coniferous Forest on Andic Soils: Effects of Litter Quality

Dissolved organic matter (DOM) plays an important role in transporting carbon and nitrogen from forest floor to mineral soils in temperate forest ecosystems. Thus, the retention of DOM via sorption or microbial assimilation is one of the critical steps for soil organic matter formation in mineral soils. The chemical properties of DOM are assumed to control these processes, yet we lack fundamental information that links litter quality, DOM chemistry, and DOM retention. Here, we studied whether differences in litter quality affect solution chemistry and whether changes in litter inputs affect DOM quality and removal in the field. The effects of litter quality on solution chemistry were evaluated using chemical fractionation methods for laboratory extracts and for soil water collected from a temperate coniferous forest where litter inputs had been altered. In a laboratory extraction, litter type (needle, wood, root) and the degree of decomposition strongly influenced solution chemistry. Root litter produced more than 10 times more water-extractable dissolved organic N (DON) than any other litter type, suggesting that root litter may be most responsible for DON production in this forest ecosystem. The chemical composition of the O-horizon leachate was similar under all field treatments (doubled needle, doubled wood, and normal litter inputs). O-horizon leachate most resembled laboratory extracts of well-decomposed litter (that is, a high proportion of hydrophobic acids), in spite of the significant amount of litter C added to the forest floor and a tendency toward higher mean DOM under doubled-Litter treatments. A lag in DOM production from added litter or microbial modification might have obscured chemical differences in DOM under the different treatments. Net DOM removal in this forest soil was strong; DOM concentration in the water deep in the mineral soil was always low regardless of concentrations in water that entered the mineral soil and of litter input manipulation. High net removal of DOM from O-horizon leachate, in spite of extremely low initial hydrophilic neutral content (labile DOM), coupled with the lack of influence by season or soil depth, suggests that DOM retention in the soil was mostly by abiotic sorption.