Composition and Function of Bacterial Communities of Bryophytes and Their Underlying Sediments in the Dajiuhu Peatland, Central China

Symbiotic microbiomes of Sphagnum have been confirmed to play a fundamental role in carbon and nitrogen cycles, however, little is known about microbiomes associated with other bryophytes in subtropical peatland ecosystems. To explore the differences in community structure, metabolic potential and interaction relationship of bacterial microbiomes associated with different bryophytes species, the gametophytes of three bryophyte species(Sphagnum palustre, Aulacomnium androgynum, and Polytrichum commune) and their underlying peat sediments were collected from the subtropical Dajiuhu Peatland and subjected to Illumina high-throughout sequencing of 16S r RNA gene. Results showed that bacterial diversity was lowest in S. palustre, the dominant moss species, among the three moss species investigated in Dajiuhu Peatland. Bacterial communities from bryophytes clearly separated with those from sediments as indicated by both phylogenetic and taxonomical approaches. Linear discriminant analysis effect size(LEf Se) identified 30 and 36 indicator taxa in mosses and peat sediments. Bacteroidetes, Verrucomicrobia and Thermoleophilia significantly enriched in S. palustre, A. androgynum and P. commune, Chloroflexi, Proteobacteria and Acidobacteria subgroup 6 was indicator taxa for corresponding underlying sediments, respectively. Despite of these differences in compositions, bacterial functional structures were similar among all bryophytes, such as abundant aerobic heterotrophs, rare nitrifiers and denitrifiers. This phenomenon was also observed among the underlying sediments. Network analysis indicated that Proteobacteria and Acidobacteria located in the center of network and exerted strong interactions to other taxa. The sub-network of bacterial communities in sediments was more connected and microbial groups were more competitive than those in bryophytes subnetwork. Our results offer new insight into the community structure, ecological function and interaction pattern of bacterial microbiomes in the Dajiuhu Peatland across different habitats.

Ecology of testate amoebae in Dajiuhu peatland of Shennongjia Mountains, China, in relation to hydrology

This study investigates the testate amoeba communities of a large peatland in Central China. The ecology and seasonal variability of testate amoeba communities were studied during 2009-2010. Investiga- tion of environmental controls using ordination showed that the relationship between testate amoeba communities and depth to water table （DWT） and pH are extremely weak. The small proportion of variance explained by water table depth here （only 1.9% in the full data） shows that the hydrological control is weaker than we expected in this peatland, and weaker than any study we are aware of using a similar methodology. Attempts to develop species- environment （transfer function） models or identify indi- cator species for future palaeoecological studies were unsuccessful. Previous large-scale studies of peatland testate amoeba ecology have been largely restricted to Europe and North America and results have been relatively consistent among studies. Our results contrast with this consensus and suggest that at least in minerotrophic peatlands in China testate amoeba communities may be primarily controlled by different environmental variables. In China, testate amoebae have been relatively little studied but may prove to be valuable for a variety of applications in palaeoecology and biomonitoring and much further work is required.

Temporal and Spatial Variations of Microbial Carbon Utilization in Water Bodies from the Dajiuhu Peatland, Central China

To investigate the microbial utilization of organic carbon in peatland ecosystem, water samples were collected from the Dajiuhu Peatland and nearby lakes, central China across the year of 2014. The acridine orange （AO） staining and Biolog Eco microplates were used to numerate microbial counts and determine the carbon utilization of microbial communities. Meanwhile, physicochemical characteristics were measured for subsequent analysis of the correlation between microbial carbon utilization and environmental factors. Results indicated that total microbial counts were between 106107 cells/L. Microbial diversities and carbon utilization rates showed a similar pattern, highest in September and lowest in November. Microbial communities in the peat pore waters preferred to utilize N-bearing carbon sources such as amines and amino acids compared with microbial communities in lakes. The network analysis of microbial utilization of 31 carbon substrates clearly distinguished microbial communities from peat pore waters and those from lakes. Redundancy analysis （RDA） showed the total organic nitrogen content （P=-0.03, F=2.5） and daily average temperature （P=0.034, F=2.4） significantly controlled microbial carbon utilization throughout the sampling period. Our report is the first one to address the temporal and spatial variations of carbon uti- lization of microbial communities which are closely related to the decomposition of organic matter in the Dajiuhu Peatland in context of climate warming.

Vertical variations and associated ecological function of bacterial communities from Sphagnum to underlying sediments in Dajiuhu Peatland

To investigate vertical changes of bacterial communities from living plants to the associated sediments and bacterial biogeochemical roles in peatland ecosystem,samples of different part of individual Sphagnum palustre and the different layers of the underlying sediments were collected from Dajiuhu Peatland in central China.All samples were subject to 16S rRNA gene clone libraries and quantitative PCR analysis.Even though bacteria vary in abundance at the same order of magnitude in all samples,they show great profile difference in composition from the top part of S.palustre to the low layer of the sediments.Cyanobacteria and alpha-Proteobacteria dominate at the top part whereas Acidobacteria at the middle part of S.palustre.Alpha-Proteobacteria and Acidobacteria are the dominant phyla at the bottom part of S.palustre and in the surface peat sediment.In contrast,bacterial communities in the subsurface sediments are dominated by Acidobacteria.These profile distributions of different bacterial communities are closely related to their ecological functions in the peatland ecosystem.Specifically,most Cyanobacteria were observed at the top green part of S.palustre,a horizon where the active photosynthesis of the moss occurs,which infers their endosymbiosis.In contrast,Acidobacteria,dominant in the subsurface sediments,are able to decompose the specific compounds on the cell wall of Sphagnum moss and thus might play an important role in the formation of the peatland,including the acidic condition.Methane oxidizing process might have been underestimated in Sphagnum peatland due to the identification of Methylocystaceae in all parts of the moss investigated here.The vertical difference in bacterial composition and bacterial ecological functions presented here sheds light on the understanding of biogeochemical processes,in particular the CH4 flux,in peat ecosystems.

神农架大九湖湿地摇蚊群落组成及其环境指示意义

泥炭地是一种水-陆过渡型的湿地生态系统。水体沼泽化过程中,植被等生物群落也随之改变,进而影响泥炭地碳埋藏和发育过程。作为泥炭地生态系统重要的次级生产者,摇蚊群落结构变迁可以为追溯泥炭地环境演变和发育历史提供关键线索。泥炭地在发育过程中将经历各种不同阶段,然而,现有的泥炭地摇蚊群落调查仅限于泥炭生境或泥炭地中开阔水域,较短的生境梯度不足以提供更为全面的摇蚊群落变化信息。神农架大九湖湿地包含泥炭地、湖泊、临时性水体等多种生境,本研究选择该湿地公园作为研究区域,通过采集不同生境的表层沉积物及水体样品,提取底泥亚化石摇蚊头壳,分析大九湖湿地中不同生境下的摇蚊群落结构差异,并对其与环境因子间的关系进行探讨。结果表明:1)大九湖湿地不同生境中摇蚊优势种迥异,泥炭藓藓丘生境中Limnophyes、Psilometriocnemus、Pseudosmittia等半陆生种类为主要优势种,湖泊生境中则以典型静水种Polypedilum nubeculosum-type为主要优势种,而过渡性水域(泥炭地洼地、沟渠及水洼生境)中,静水种与半陆生种共存;2)烧失量、水位埋深和p H是塑造不同生境类型下摇蚊群落结构的显著环境因子,水文条件主要通过改变碳积累过程等其他环境条件间接影响生物群落组成;3)沿水生-半陆生生境梯度,有机质含量和类型均发生显著变化,而摇蚊群落也由静水种、静水/半陆生共存转变为以半陆生种为主,摇蚊群落对生境变化表现出良好的响应过程。本研究揭示了不同生境条件下摇蚊群落的结构差异及影响摇蚊群落结构的潜在因子,为未来基于摇蚊的长时间尺度上泥炭地发育过程分析提供参考依据。

Net Ecosystem CO2 Flux and Effect Factors in Peatland Ecosystem of Central China

Peatland ecosystems play an important role in the global carbon cycle because they act as a pool or sink for the carbon cycle. However, the relationship between seasonality effect factors and net ecosystem CO2 exchange (NEE) remains to be clarified, particularly for the non-growing season. Here, based on the eddy covariance technique, NEE in the peatland ecosystem of Central China was examined to measure two years’ (2016 and 2017) accumulation of carbon dioxide emissions with contrasting seasonal distribution of environmental factors. Our results demonstrate the cumulative net ecosystem CO2 emissions during the study period was in the first non-growing season 2.94 ± 4.83 μmolCO2 m-2.s-1 with the lowest values in the same year in first growing season was -2.79 ± 4.92 μmolCO2 m-2.s-1. The results indicate the effect of seasonal variations of NEE can be directly reflected in daily and seasonal variations in growth and respiration of peatland ecosystem by environmental parameters over different growing stages.

大九湖泥炭地距今16000年以来Hg沉积记录及影响因子

神农架大九湖盆地距今16000年以来的泥炭沉积被用来分析Hg含量变化及其主要影响因子.基于剖面Ti、Al、Sc、Rb、Sr、Pb、Zn等元素含量和δ13C、腐殖化度等指标,主成分分析和逐步回归分析揭示泥炭剖面Hg含量变化主要受大气降尘、地表径流作用下的矿物质输入、大气降水、泥炭分解程度等因子影响.根据各因子影响Hg含量的强度随年代(深度)变化以及剖面Hg含量变化,距今16000年以来大九湖泥炭剖面的Hg记录可以分为6个阶段.在阶段Ⅰ(16.0~15.6cal kyr BP),Hg含量低值源于大气降尘减少和泥炭分解程度降低;第Ⅱ阶段(15.6~14.2cal kyr BP)大气降水增加以及陆地生物量增多、陆源有机物输入增多,导致Hg含量升高;阶段Ⅲ(14.2~11.3cal kyr BP)Younger Dryas时期(YD,12.3~11.3cal kyr BP),因大气降尘增多,泥炭分解程度增加,Hg含量较YD之前升高;第Ⅳ阶段(11.3~4.3cal kyr BP),各因子作用波动明显,Hg含量整体处于高值段;在第Ⅴ阶段(4.3~3.1cal kyr BP)气候转干,大气降尘也较低,Hg含量出现明显的降低.第Ⅵ阶段(3.1cal kyr BP以来)表现出大气降尘的逐渐增加和整体减少的矿物质输入,反映降水减少以及逐渐增强的人类活动影响,Hg含量则持续升高.

神农架大九湖泥炭湿地能量通量及平衡分析

研究大九湖泥炭湿地通量,为准确评估泥炭地生态系统与大气间的物质和能量交换提供基础数据。利用涡度相关系统对神农架大九湖2015年9月~2016年8月的净辐射、显热通量、潜热通量及土壤热通量进行了为期1年的连续观测。结果表明:1)泥炭地全年净辐射为3 146.91MJ/m2,显热通量为931.79MJ/m2,潜热通量为1 762.40MJ/m2,土壤热通量为22.26MJ/m2;能量分配主要以潜热为主,占净辐射的56%。潜热通量为能量散失的主要形式,土壤表现为热汇。2)各能量分量季节变化明显,10月、1月、4月及7月的日变化均以净辐射为基础,呈相似的单峰型曲线变化。3)波文比逐月变化不规律,月平均波文比为0.65、波动在0.34~1.06,年波文比为0.53,全年能量分配潜热通量大于显热通量。4)神农架大九湖泥炭地年能量闭合度为0.86,存在14%的能量不闭合。不闭合的原因可能与下垫面状况、季节变化及平流的影响产生的波动等相关。

神农架大九湖泥炭地溶解有机碳季节性变化及其影响因素

亚热带泥炭地在水源涵养、碳储存和生物多样性等方面有着重要的保护价值。溶解有机碳(DOC)是泥炭地中容易受到外界扰动的一部分碳,在气候变化和人类活动的双重影响下,DOC可能通过降解或横向迁移从泥炭地中流失,潜在地威胁了泥炭地的碳储存功能。然而,目前对于亚热带泥炭地DOC如何响应季节性尺度的环境变化还缺乏深入的认识。以位于北亚热带的神农架大九湖泥炭地为研究对象,开展了季节尺度的泥炭孔隙水DOC浓度和紫外-可见吸收光谱特征以及环境参数的监测。结果显示,在大九湖泥炭地中,表层0~10 cm的泥炭孔隙水DOC浓度和光谱参数具有明显的季节差异性,DOC浓度和光谱参数还表现出明显的深度差异性。相关性分析显示,DOC浓度及紫外-可见吸收光谱参数直接受控于泥炭孔隙水的电导率和氨态氮浓度,可能还间接受到泥炭地水位和孔隙水硝态氮浓度等因素的影响。以上结果表明,在亚热带季风气候条件下,季节性水位波动引起的泥炭水化学参数和营养盐的变化,可能显著改变表层泥炭DOC动态,需要重视这种季节性波动对亚热带泥炭地碳储存能力以及生态功能的影响。

神农架大九湖泥炭地碳储量估算及固碳能力研究

通过对神农架大九湖泥炭地进行野外调查和长期观测,采用经验公式和实验室分析方法,计算了神农架大九湖泥炭地土壤有机碳含量和有机碳储量,并对2016—2018年神农架大九湖泥炭地的固碳能力特征进行了分析。结果表明:在0~100 cm深度范围内,神农架大九湖泥炭地土壤有机碳含量的变化范围为282.90~516.10 g/kg,土壤有机碳储量为7.04×10^(5) t,并估算得到在总沉积深度为0~260 cm范围内神农架大九湖泥炭地土壤有机碳总储量为1.45×10^(6)~1.61×10^(6) t,有机碳积累强度为1800~2000 t/hm^(2);在2016—2018年3年间,神农架大九湖泥炭地净生态系统生产力(NEP)与CH_(4)通量较高的月份均出现在5~9月水热同期的时间段内,期间泥炭地固碳总量约为6975.00 t,单位面积年均固碳量为3.09 t/hm^(2),在月变化水平上泥炭地固碳量与气温和降雨量呈正相关关系,观测期间的固碳功能未发生改变,泥炭地整体表现为碳汇。

近400年来湖北大九湖泥炭地摇蚊对湿度变化的响应

神农架大九湖泥炭地是华中地区少有的亚高山泥炭藓湿地,是研究长江中游气候变化及其生态效应的理想区域.本文通过大九湖一根泥炭岩芯的年代学、元素及摇蚊亚化石记录,结合区域古气候资料,探讨大九湖泥炭地地表干湿变化历史及生物响应过程.结果表明,近400年来大九湖泥炭地古水文和摇蚊种群变化经历了3个主要阶段:1820s之前研究区内气候偏冷湿,尤其是1720s—1820s年间,冷湿的环境有利于泥炭中碳的大量积累,较高的地表有效湿度使得摇蚊大量生长,同时湖泊相摇蚊属种丰富度及含量均较高;1820s—1940s年间,区域内夏季降水量显著降低,同时伴随明显的区域增温过程,泥炭地地表有效湿度过低不利于水生生物生长,摇蚊种群生物量极低;1940s(尤其1970s)后,摇蚊种群丰度逐渐回升,但湖泊相摇蚊丰度较1820s以前明显降低,半陆生摇蚊属种丰度有所增加,说明尽管该时期泥炭地表湿度有所增加,但较1820s前仍较低,暖湿气候下泥炭分解也较为明显.本研究探索性地分析了气候变化背景下泥炭地摇蚊种群对泥炭地湿度变化的响应过程,这不仅为摇蚊亚化石在气候变化研究中的应用开拓了新的领域,同时也为全面、精准地理解泥炭地演化及区域环境变化过程提供了新线索.

湖北神农架大九湖泥炭地泥炭藓共生细菌群落分析

对采自湖北神农架大九湖泥炭地泥炭藓(Sphagnum palustre)样品进行了不同预处理,之后提取微生物基因组DNA,构建克隆文库进而对泥炭藓共生菌的群落结构进行分析。菌落培养实验和荧光定量PCR结果显示,双氧水能杀死泥炭藓表面附生的微生物及破坏部分DNA,为研究泥炭藓内共生细菌提供一定的途径。群落组成分析结果表明双氧水处理后,所获得的细菌克隆文库的群落特征发生了改变,主要表现在细菌种类的减少及各菌门所占比率的变化上:NTX-0中酸杆菌门(Acidobacteria)和变形杆菌门(Proteaobacteria)百分比含量分别位居第一和第二,而经过双氧水进行表面除菌后NTX-0-degerming中变形菌门(Proteobacteria)占了绝对优势;而在NTX-2-degerming中,蓝细菌门(Cyanobacteria)占绝对主导地位,细菌的群落多样性明显降低,细菌种类减少。系统发育分析表明与泥炭藓内共生的细菌一方面能适应大九湖泥炭湿地酸性、贫营养的环境,另一方面能为泥炭藓提供碳源、氮源,从而参与泥炭湿地的元素循环。尤其值得注意的是在内共生菌中发现了Ⅱ型甲烷氧化菌,证实了甲烷氧化菌与泥炭藓的内共生关系,暗示着这类细菌通过自身的代谢进而影响全球碳循环的潜在意义。此外,首次报道了利用细菌的通用引物扩增出了大量泥炭藓叶绿体的序列,这可能为叶绿体内共生学说提供佐证。

神农架大九湖泥炭地孔隙水溶解有机碳特征及其影响因素

溶解性有机碳(Dissolved Organic Carbon,DOC)是泥炭地碳循环的重要组成部分。以往的研究大多集中在北方泥炭地,而对亚热带季风区泥炭地DOC动力学的认识十分有限。利用紫外可见光光谱(UVVis)和三维荧光光谱结合平行因子分析法(EEM-PARAFAC)研究了神农架大九湖泥炭地孔隙水的DOC浓度与化学组成及其影响因素。EEM-PARAFAC的结果表明:大九湖泥炭地孔隙水DOC主要包含3种类腐殖质组分。紫外可见光和荧光指标表明,泥炭孔隙水DOC表观分子较小,而芳香度较高。深度剖面数据表明,泥炭孔隙水DOC浓度随深度降低,0~10 cm深度浓度最高为24. 16 mg/L,150~160 cm深度浓度最低为9. 72 mg/L,并且深层DOC以微生物代谢产生的新鲜有机物为主,具有较低的腐殖化度。此外,氧化还原电位(ORP)与DOC浓度及化学性质关系密切。以上结果表明,在亚热带泥炭地中,微生物来源或受微生物改造的有机物是泥炭孔隙水DOC的重要组成部分;垂向输送或选择性保存是影响该亚热带亚高山泥炭地DOC动力学的重要因素。

神农架大九湖泥炭湿地甲烷通量特征及其与土壤微生物群落组成的关系

虽然神农架大九湖泥炭湿地的甲烷排放特征、土壤微生物群落组成已有一些研究,但是关于微生物群落与甲烷排放量的关系及影响的研究不多.采用涡度相关法和高通量测序技术,探讨2016年3月~2017年2月微生物对大九湖泥炭湿地CH4通量排放的影响.结果表明,大九湖泥炭湿地研究期间表现为CH4的源,年总排放量5566.27 mg·m^-2,日平均排放速率10.96 nmol·m^-2·s^-1;春、夏、秋、冬四季的平均通量分别为12.06、22.47、3.02、2.92 nmol·m^-2·s^-1;研究区优势菌为泉古菌(54.6%)、广古菌(18.9%)、酸杆菌(12.6%)等.对不同季节样品Shannon指数进行单因素分析,p值为0.000127,分析结果表明:CH4月通量变化均呈明显的倒“U”型;夏季CH4通量最高,冬季最低;不同季节的微生物群落物种多样性存在显著差异;夏季、冬季微生物群落组成与CH4通量分别呈显著正相关、显著负相关;未鉴别出的菌群和俭菌总门与CH4通量呈极显著正相关关系,泉古菌门与CH4通量呈极显著负相关关系.