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1.
O3 concentrations in the troposphere are rising and those in the stratosphere decreasing, the latter resulting in higher fluxes of solar ultraviolet-B (UV-B) radiation to the earth's surface. We assessed whether the fluxes of CO2 and CH4 are altered by enhanced UV-B radiation or elevated tropospheric O3 concentrations in boreal peatland microcosms (core depth 40 cm, diameter 10.5 cm) with different vegetation cover. At the end of the UV-B experiment which lasted for a growing season, net CO2 exchange (NEE) and dark ecosystem respiration (R TOT) were sevenfold higher, and CH4 efflux 12-fold higher, in microcosms with intact vegetation dominated by Eriophorum vaginatum L. and Sphagnum spp., compared to microcosms from which we removed E. vaginatum. Vegetation treatment had minor effects on CH4 production and consumption potentials in the peat, suggesting that the large difference in CH4 efflux is mainly due to efficient CH4 transport via the aerenchyma of E. vaginatum. Ambient UV-B supplemented with 30% and elevated O3 concentrations (100 and 200 ppb, for 7 weeks) significantly increased R TOT in both vegetation treatments. Elevated O3 concentrations reduced NEE over time, while UV-B had no clear effects on the fluxes of CO2 or CH4 in the cloudy summer of the study. Field experiments are needed to assess the significance of increasing UV-B radiation and elevated tropospheric O3 concentration on peatland gas exchange in the long-term. 相似文献
2.
Tim R. Moore Allison De Young Jill L. Bubier Elyn R. Humphreys Peter M. Lafleur Nigel T. Roulet 《Ecosystems》2011,14(4):646-657
The Mer Bleue peatland is a large ombrotrophic bog with hummock-lawn microtopography, poor fen sections and beaver ponds at
the margin. Average growing-season (May–October) fluxes of methane (CH4) measured in 2002–2003 across the bog ranged from less than 5 mg m−2 d−1 in hummocks, to greater than 100 mg m−2 d−1 in lawns and ponds. The average position of the water table explained about half of the variation in the season average CH4 fluxes, similar to that observed in many other peatlands in Canada and elsewhere. The flux varied most when the water table
position ranged between −15 and −40 cm. To better establish the factors that influence this variability, we measured CH4 flux at approximately weekly intervals from May to November for 5 years (2004–2008) at 12 collars representing the water
table and vegetation variations typical of the peatland. Over the snow-free season, peat temperature is the dominant correlate
and the difference among the collars’ seasonal average CH4 flux is partially dependent on water table position. A third important correlate on CH4 flux is vegetation, particularly the presence of Eriophorum vaginatum, which increases CH4 flux, as well as differences in the potential of the peat profile to produce and consume CH4 under anaerobic and aerobic conditions. The combination of peat temperature and water table position with vegetation cover
was able to explain approximately 44% of the variation in daily CH4 flux, based on 1097 individual measurements. There was considerable inter-annual variation in fluxes, associated with varying
peat thermal and water table regimes in response to variations in weather, but also by variations in the water level in peripheral
ponds, associated with beaver dam activity. Raised water level in the beaver ponds led to higher water tables and increased
CH4 emission in the peatland. 相似文献
3.
Eeva‐Stiina Tuittila Veli‐Matti Komulainen Harri Vasander Hannu Nyknen Pertti J. Martikainen Jukka Laine 《Global Change Biology》2000,6(5):569-581
We measured a cut‐away peatland's CH4 dynamics using the static chamber technique one year before and two years after restoration (rewetting). The CH4 emissions were related to variation in vegetation and abiotic factors using multiple linear regression. A statistical model for CH4 flux with cottongrass cover (Eriophorum vaginatum L.), soil temperature, water level, and effective temperature sum index as driving variables explained most (r2 = 0.81) of the temporal and spatial variability in the fluxes. In addition to the direct increasing effect of raised water level on CH4 emissions, rewetting also promoted an increase of cottongrass cover which consequently increased carbon flux (substrate availability) into the system. The seasonal CH4 dynamics in tussocks followed seasonal CO2 dynamics till mid August but in late autumn CH4 emissions increased while CO2 influxes decreased. The reconstructed seasonal CH4 exchange was clearly higher following the rewetting, although it was still lower than emissions from pristine mires in the same area. However, our simulation for closed cottongrass vegetation showed that CH4 emissions from restored peatlands may remain at a lower level for a longer period of time even after sites have become fully vegetated and colonized by mire plants. 相似文献
4.
湿地是大气甲烷(CH_4)的主要排放源,而有关放牧对湿地CH_4排放的影响特征仍未得到足够的报道。因此,通过静态箱法,研究了放牧对四川省若尔盖高原湿地CH_4排放的影响,CH_4气体通过快速温室气体分析仪测量。结果表明:放牧样地和围栏内样地生长季CH_4排放量为(31.32±19.57)g/m~2和(30.31±23.46)g/m~2,它们之间无差异显著;但是集中放牧期间(7—9月),放牧样地(21.01±12.35)g/m~2较围栏内样地显著增加了CH_4排放量为54.3%。2014年生长季期间通过刈割植物模拟放牧表明两种刈割强度CH_4排放量为(5.01±5.37)g/m~2和(4.69±5.99)g/m~2,较未刈割样地(1.15±1.89)g/m~2增加了335.9%和308.0%,其原因可能是放牧或者刈割减少地表植物生物量,降低植物高度,缩短了CH_4排放的路径距离。该结果可为我国高原湿地保护与管理决策提供基础数据支撑。 相似文献
5.
CH4 emission from a hollow-ridge complex in a raised bog: The role of CH4 production and oxidation 总被引:5,自引:0,他引:5
The aim of this study was to correlate magnitude andcontrols of CH4 fluxes with the microtopographyand the vegetation in a hollow-ridge complex of araised bog. High CH4 emission rates were measuredfrom hollows and mud-bottom hollows, while hummocksconsumed atmospheric CH4 at a low rate. Thehighest emissions were measured from plots with Eriophorum vaginatum and Scheuchzeriapalustris. CH4 emission ceased after Scheuchzeria had been clipped below the water table,indicating the importance of this aerenchymatic plantas a conduit for CH4.Peat in the upper catotelm of hollows was younger andless decomposed than in hummocks. Potential CH4production in vitro was higher and themethanogenic association was better adapted to highertemperatures in hollow than in hummock peat. Highertemperatures in hollows resulted in a strongerCH4 source in hollows than in hummocks. Negativefluxes from hummocks indicated that even in wetlandsmethanotrophic bacteria exist that are able to oxidizeCH4 at atmospheric mixing ratios, and thatoxidation controls CH4 emission completely. TheCH4 mixing ratio was low in the acrotelm, but itincreased within the catotelm. Comparing fluxesmeasured in static chambers with fluxes calculatedfrom the porewater CH4 profiles it was deducedthat the zone of methane oxidation was located closeto the water table.In hollows, CH4 production at in situtemperature was far higher than emission into theatmosphere, corresponding to an oxidation rate ofnearly 99%. The CH4 flux between the catotelmand the acrotelm of hollows was also higher than theemission, indicating the importance of CH4oxidation in the aerobic acrotelm, too. CH4microprofiles showed that CH4 oxidation inmud-bottom hollows was confined to the topmost 2 mm,and that in Sphagnum-covered hollows CH4oxidation occurred at the lower edge of green Sphagnum-parts. 相似文献
6.
Md. Sharif MahmoodMaria Strack 《Ecological Engineering》2011,37(11):1859-1868
In North America, mulching of vacuum-harvested sites combined with blocking of the drainage system is widely used for peatland restoration to accelerate Sphagnum establishment. However, peat extraction in fen peatlands or exposure of deeper minerotrophic peat layers results in soil chemistry that is less suitable for re-establishment of Sphagnum moss. In this situation, restoration of plant species characteristic of minerotrophic peatlands is desirable to return the site to a carbon accumulating system. In these cases, it may be worthwhile to maintain spontaneously revegetating species as part of restoration if they provide desirable ecosystem functions. We studied the role of six spontaneously recolonizing vegetation communities for methane (CH4) emissions and pore water CH4 concentration for two growing seasons (2008 and 2009) at an abandoned minerotrophic peatland in southeastern Quebec. We then compared the results with bare peat and adjacent natural fen vegetation. Communities dominated by Eriophorum vaginatum, Carex aquatilis and Typha latifolia had CH4 flux an order of magnitude greater than other cutover vegetation types and natural sites. In contrast, Scirpus atrocinctus and Equisetum arvense had CH4 emission rates lower than natural hollow vegetation. We found seasonal average water table and vegetation volume had significant correlation with CH4 flux. Water table and soil temperature were significantly correlated with CH4 flux at plots where the water table was near or above the surface. Pore water CH4 concentration suggests that CH4 is being produced at the cutover peatland and that low measured fluxes likely result from substantial oxidation of CH4 in the unsaturated zone. Understanding ecosystem functions of spontaneously recolonizing species on cutover fens can be used to help make decisions about the inclusion of these communities for future restoration measures. 相似文献
7.
Effect of experimental nitrogen load on methane and nitrous oxide fluxes on ombrotrophic boreal peatland 总被引:8,自引:0,他引:8
Nykänen Hannu Vasander Harri Huttunen Jari T. Martikainen Pertti J. 《Plant and Soil》2002,242(1):147-155
Methane (CH4) and nitrous oxide (N2O) dynamics were studied in a boreal Sphagnum fuscum pine bog receiving annually (from 1991 to 1996) 30 or 100 kg NH4NO3-N ha–1. The gas emissions were measured during the last three growing seasons of the experiment. Nitrogen treatment did not affect the CH4 fluxes in the microsites where S. fuscum and S. angustifolium dominated. However, addition of 100 kg NH4NO3-N ha–1 yr–1 increased the CH4 emission from those microsites dominated by S. fuscum. This increase was associated with the increase in coverage of cotton grass (Eriophorum vaginatum) induced by the nitrogen treatment. The differences in the CH4 emissions were not related to the CH4 oxidation and production potentials in the peat profiles. The N2O fluxes were negligible from all microsites. Only minor short-term increases occurred after the nitrogen addition. 相似文献
8.
Effect of microrelief and vegetation on methane emission from wet polygonal tundra, Lena Delta, Northern Siberia 总被引:3,自引:0,他引:3
The effect of microrelief and vegetation on methane (CH4) emission was investigated in a wet polygonal tundra of the Lena Delta, Northern Siberia (72.37N, 126.47E). Total and plant-mediated CH4 fluxes were measured by closed-chamber techniques at two typical sites within a low-centred polygon. During the study period, total CH4 flux averaged 28.0±5.4mgm–2d–1 in the depressed polygon centre and only 4.3±0.8mgm–2d–1 at the elevated polygon rim. This substantial small-scale spatial variability of CH4 emission was caused by strong differences of hydrologic conditions within the microrelief of the polygon, which affected aeration status and organic matter content of the soils as well as the vegetation cover. Beside water table position, the vegetation cover was a major factor controlling CH4 emission from polygonal tundra. It was shown that the dominant vascular plant of the study area, Carex aquatilis, possesses large aerenchyma, which serve as pathways for substantial plant-mediated CH4 transport. The importance of plant-mediated CH4 flux was strongly influenced by the position of the water table relative to the main root horizon. Plant-mediated CH4 transport accounted for about two-thirds of the total flux in the wet polygon centre and for less than one-third of the total flux at the moist polygon rim. A clipping experiment and microscopic-anatomical studies suggested that plant-mediated CH4 transport via C. aquatilis plants is driven only by diffusion and is limited by the high diffusion resistance of the dense root exodermes. 相似文献
9.
Methane emission and rhizospheric CH4 oxidation were studied in stands of Equisetum fluviatile, a common cryptogam in boreal lakes. The experiment was performed in mesocosms with organic sediment or sand bottoms under natural variation of temperature and light using the light-oxic – dark-anoxic chamber (LO/DA) technique. Net CH4 emission from the organic sediment during the growing season varied between 3.4 and 19.0 mg m–2 h–1, but from sand the net CH4 emission was only 3–10% of that measured from the organic sediment. In the organic sediment net CH4 emission was very significantly correlated with sediment temperature (r2 = 0.92). In the sand mesocosms the variation of net CH4 emission was better correlated with the shoot biomass than with sediment temperature variation during the growing season, indicating that methanogens were severely limited by substrate availability and were probably dependent on substrates produced by E. fluviatile. The proportion of the methane oxidized of the potential CH4 emission in summer did not differ significantly between the bottom types. The net CH4 emission during the growing season as a proportion of the seasonal maximum of the shoot biomass was significantly higher in the organic sediment mesocosms (6.5%) than in sand (1.7%). The high CH4 emissions observed from dense well-established E. fluviatile stands in the field appear to be more related to temperature-regulated turnover of detritus in the anaerobic sediment and less to CH4 oxidation and seasonal variation in plant growth dynamics 相似文献
10.
Diel methane emissions in stands of Spartina alterniflora and Suaeda salsa from a coastal salt marsh 总被引:1,自引:0,他引:1
In this study, we aimed to understand the influence of plant type on the monthly variations of diel CH4 fluxes from Spartina alterniflora and Suaeda salsa of coastal salt marshes at three growth stages (July, August and September). Dissolved CH4 concentrations in porewater and sediment redox potentials were monitored, as were aboveground plant biomass and stem densities. CH4 fluxes exhibited clear monthly variations and peaked in September in the S. alterniflora and S. salsa mesocosms. However, no discernible diel variation was observed in the CH4 flux in the S. salsa mesocosm, probably due to its weak gas transport capacity. By contrast, notable diel variations of CH4 flux with the peak of 1.42 and 3.67 mg CH4 m−2 h−1 at 12:00 and the lowest of 0.75 and 2.11 mg CH4 m−2 h−1 at 3:00 or 6:00 were observed in the S. alterniflora mesocosm on 11 August and 11 September, respectively, but not in July mainly due to low plant biomass masking diel variations in the porewater CH4 concentration. The ratios of the maximum flux to minimum flux over the course of the day in the S. alterniflora mesocosm on 10 July, 11 August and 11 September were 1.28, 1.89 and 1.76, respectively, and corresponding values for porewater CH4 concentration were 1.31, 1.39 and 1.17, respectively. CH4 flux significantly correlated with CH4 concentration in porewater, and both were significantly related to air temperature. These findings indicate that CH4 production and CH4 flux at the middle growth stage (August) exhibited greater responses to changes in air temperature, which in turn induced the higher diel variation. The higher diel cycle for CH4 flux in August than in September was likely due to the higher proportion of CH4 oxidized during diffusion within the aerenchyma system. Our results suggest that the extent of diel variations in CH4 flux may have depended on the gas transport capacity of plants, and the highest diel variation occurred at the middle growth stage. 相似文献
11.
Drainage of peatlands for forestry starts a succession of ground vegetation in which mire species are gradually replaced by forest species. Some mire plant communities vanish quickly following the water-level drawdown; some may prevail longer in the moister patches of peatland. Drainage ditches, as a new kind of surface, introduce another component of spatial variation in drained peatlands. These variations were hypothesized to affect methane (CH4) fluxes from drained peatlands. Methane fluxes from different plant communities and unvegetated surfaces, including ditches, were measured at the drained part of Lakkasuo mire, Central Finland. The fluxes were found to be related to peatland site type, plant community, water-table position and soil temperature. At nutrient-rich fen sites fluxes between plant communities differed only a little: almost all plots acted as CH4 sinks (−0.9 to −0.4 mg CH4 m−2 d−1), with the exception of Eriophorum angustifolium Honck. communities, which emitted 0.9 g CH4 m−2 d−1. At nutrient-poor bog site the differences between plant communities were clearer. The highest emissions were measured from Eriophorum vaginatum L. communities (29.7 mg CH4 m−2 d−1), with a decreasing trend to Sphagna (10.0 mg CH4 m−2 d−1) and forest moss communities (2.6 mg CH4 m−2 d−1). CH4 emissions from different kinds of ditches were highly variable, and extremely high emissions (summertime averages 182–600 mg CH4 m−2 d−1) were measured from continuously water-covered ditches at the drained fen. Variability in the emissions was caused by differences in the origin and movement of water in the ditches, as well as differences in vegetation communities in the ditches. While drainage on average greatly decreases CH4 emissions from peatlands, a great spatial variability in fluxes is emerged. Emissions from ditches constantly covered with water, may in some cases have a great impact on the overall CH4 emissions from drained peatlands. 相似文献
12.
长江滩地是甲烷(CH_4)排放的潜在热点区域,然而目前其CH_4通量的变化特征及控制因子尚未被揭晓。基于涡度相关闭路系统进行为期2年多的连续观测,旨在揭示长江滩地杨树(Populus deltoides)人工林幼林CH_4通量在不同时间尺度上的变化特征及其调控机理。结果显示,全年和部分未淹水月份表现出白天排放强而夜间排放弱的平均日变化特征,且淹水前、淹水期间和退水后分别表现出日间双峰型(7:00和10:00)、日间与夜间各一峰的双峰型(10:00和23:00),以及典型的日间单峰型(10:00)。淹水年份(2012年)在夏季(6—8月)排放最强,在春末(5月)和秋末冬初(11—12月)排放最弱,而未淹水年份(2013年)在初夏(6月)排放最强,在盛夏(7月)和秋末(11月)转变为较弱的吸收。淹水年份的年排放量((128.0±42.4)mmol/m~2)是未淹水年份((51.5±29.1)mmol/m~2)的2.5倍。滩地人工林幼林CH_4通量的日变化和季节变化最可能受到摩擦风速、水位和土壤温度的调节,而年际间的巨大差异主要由淹水状况决定。 相似文献
13.
于2012年7月—2014年6月对地处干旱区的张掖湿地甲烷(CH_4)通量进行观测,分析其CH_4通量的变化特征及其影响因子。结果表明:CH_4通量的日变化趋势总体表现为白天大于夜间;不同季节CH_4通量排放特征差异明显,夏季最大,春秋次之,冬季最小;CH_4通量日总量与空气温度、土壤温度之间指数相关关系显著,其中4 cm处土壤温度与之相关性最强;1—6月摩擦风速(U*)与CH_4通量显著正相关;结合CO_2通量观测数据,研究时段张掖湿地净碳吸收量为495.92 g C m~(-2)a~(-1),为明显碳汇。 相似文献
14.
Under the warmer climate, predicted for the future, northern peatlands are expected to become drier. This drying will lower
the water table and likely result in reduced emissions of methane (CH4) from these ecosystems. However, the prediction of declining CH4 fluxes does not consider the potential effects of ecological succession, particularly the invasion of sedges into currently
wet sites (open water pools, low lawns). The goal of this study was to characterize the relationship between the presence
of sedges in peatlands and CH4 efflux under natural conditions and under a climate change simulation (drained peatland). Methane fluxes, gross ecosystem
production, and dissolved pore water CH4 concentrations were measured and a vegetation survey was conducted in a natural and drained peatland near St. Charles-de-Bellechasse,
Quebec, Canada, in the summer of 2003. Each peatland also had plots where the sedges had been removed by clipping. Sedges
were larger, more dominant, and more productive at the drained peatland site. The natural peatland had higher CH4 fluxes than the drained peatland, indicating that drainage was a significant control on CH4 flux. Methane flux was higher from plots with sedges than from plots where sedges had been removed at the natural peatland
site, whereas the opposite case was observed at the drained peatland site. These results suggest that CH4 flux was enhanced by sedges at the natural peatland site and attenuated by sedges at the drained peatland site. However,
the attenuation of CH4 flux due to sedges at the drained site was reduced in wetter periods. This finding suggests that CH4 flux could be decreased in the event of climate warming due to the greater depth to the water table, and that sedges colonizing
these areas could further attenuate CH4 fluxes during dry periods. However, during wet periods, the sedges may cause CH4 fluxes to be higher than is currently predicted for climate change scenarios. 相似文献
15.
采用静态箱-气相色谱法与相对生长方程法,同步测定小兴安岭7种天然沼泽湿地(草丛沼泽-C、灌丛沼泽-G、毛赤杨沼泽-M、白桦沼泽-B、落叶松苔草沼泽-L-T、落叶松藓类沼泽-L-X、落叶松泥炭藓沼泽-L-N)的土壤呼吸(CO_2、CH_4)净碳排放量、植被年净固碳量,并依据生态系统净碳收支平衡,揭示温带天然沼泽湿地的碳源/汇作用规律。结果表明:(1)7种天然沼泽CH_4年通量(0.006—7.756 mg m~(-2)h~(-1))呈M(高于其他类型1.0—1291.7倍,P0.05)C、G、B(高于针叶林沼泽17.7—649.0倍,P0.05)针叶林沼泽变化趋势,其季节动态存在3种类型(C、G单峰型、M、B多峰型及针叶林沼泽排放与吸收交替型);(2)其CO_2年通量(157.40—231.06 mg m~(-2)h~(-1))呈G(高于森林沼泽28.7%—46.8%,P0.05)C(高于森林沼泽7.4%—22.5%,P0.05)森林沼泽的变化趋势,其季节动态存在2种类型(C、G、L-X和L-N双峰型和M、B、L-T单峰型);(3)C、G、M、B、L-N CH_4排放仅受0—40 cm不同土壤层温度所控制;7种天然沼泽土壤CO_2排放均受气温及0—40 cm不同土壤层温度所控制,但B、L-X、L-N受温度与水位综合控制;(4)其植被年净固碳量((2.05±0.09)—(6.75±0.27)t C hm-2a-1)呈C(高于其他类型65.4%—229.3%,P0.05)G、B、L-T、L-X、L-N(高于M 80.0%—99.0%,P0.05)M变化趋势;(5)7种天然沼泽的碳源/汇(-2.32—2.09 t C hm-2a-1)作用不同,C、B和L-N为碳吸收汇(C强汇、B和L-N弱汇),M、G、L-T和L-X则为碳排放源(M、G强源、L-T和L-X弱源)。因此,温带小兴安岭草丛沼泽为碳强汇、灌丛沼泽为碳强源、森林沼泽基本维持碳平衡(除M外)。 相似文献
16.
2015年12月—2016年10月,每月小潮日原位定期向闽江口塔礁洲淡水感潮野慈姑(Sagittaria trifolia L.)湿地施加剂量为60、120 kg S hm~(-2)a~(-1)的K_2SO_4溶液(分别记做S-60和S-120),探讨模拟硫酸根(SO_4~(2-))沉降对河口淡水感潮湿地甲烷(CH4)排放通量及间隙水SO_4~(2-)浓度的影响。对照、S-60和S-120处理组CH_4排放通量年均值分别为(7.88±1.00)mg h~(-1)m~(-2)、(6.55±0.97)mg h~(-1)m~(-2)和(6.66±1.49)mg h~(-1)m~(-2)。在年尺度上,两个高强度模拟SO_4~(2-)沉降处理组均未显著降低闽江口淡水感潮野慈姑湿地CH_4排放通量(P0.05),即高强度SO_4~(2-)沉降不会对河口淡水感潮湿地CH_4排放通量产生类似于其对泥炭湿地和水稻田的显著抑制效应。在年尺度以及秋、冬季,两个施加K_2SO_4溶液处理显著增加了野慈姑湿地10 cm深度土壤间隙水SO_4~(2-)浓度。对于各个处理组,温度较高的夏、秋季CH_4排放通量均显著高于温度相对较低的冬、春季(P0.05)。不同处理组CH_4排放通量均与土壤温度呈显著正相关关系,温度仍然是影响亚热带河口淡水感潮湿地CH_4排放通量的重要环境因子。 相似文献
17.
Scott J. Davidson Victoria L. Sloan Gareth K. Phoenix Robert Wagner James P. Fisher Walter C. Oechel Donatella Zona 《Ecosystems》2016,19(6):1116-1132
Methane (CH4) emissions from Arctic tundra are an important feedback to global climate. Currently, modelling and predicting CH4 fluxes at broader scales are limited by the challenge of upscaling plot-scale measurements in spatially heterogeneous landscapes, and by uncertainties regarding key controls of CH4 emissions. In this study, CH4 and CO2 fluxes were measured together with a range of environmental variables and detailed vegetation analysis at four sites spanning 300 km latitude from Barrow to Ivotuk (Alaska). We used multiple regression modelling to identify drivers of CH4 flux, and to examine relationships between gross primary productivity (GPP), dissolved organic carbon (DOC) and CH4 fluxes. We found that a highly simplified vegetation classification consisting of just three vegetation types (wet sedge, tussock sedge and other) explained 54% of the variation in CH4 fluxes across the entire transect, performing almost as well as a more complex model including water table, sedge height and soil moisture (explaining 58% of the variation in CH4 fluxes). Substantial CH4 emissions were recorded from tussock sedges in locations even when the water table was lower than 40 cm below the surface, demonstrating the importance of plant-mediated transport. We also found no relationship between instantaneous GPP and CH4 fluxes, suggesting that models should be cautious in assuming a direct relationship between primary production and CH4 emissions. Our findings demonstrate the importance of vegetation as an integrator of processes controlling CH4 emissions in Arctic ecosystems, and provide a simplified framework for upscaling plot scale CH4 flux measurements from Arctic ecosystems. 相似文献
18.
Species composition affects the carbon turnover and the formation and emission of the greenhouse gas methane (CH4) in wetlands. Here we investigate the individual effects of vascular plant species on the carbon cycling in a wetland ecosystem.
We used a novel combination of laboratory methods and controlled environment facilities and studied three different vascular
plant species (Eriophorum vaginatum, Carex rostrata and Juncus effusus) collected from the same wetland in southern Sweden. We found distinct differences in the functioning of these wetland sedges
in terms of their effects on carbon dioxide (CO2) and CH4 fluxes, bubble emission of CH4, decomposition of 14C-labelled acetate into 14CH4 and 14CO2, rhizospheric oxidation of CH4 to CO2 and stimulation of methanogenesis through root exudation of substrate (e.g., acetate). The results show that the emission
of CH4 from peat–plant monoliths was highest when the vegetation was dominated by Carex (6.76 mg CH4 m−2 h−1) than when it was dominated by Eriophorum (2.38 mg CH4 m−2 h−1) or Juncus (2.68 mg CH4 m−2 h−1). Furthermore, the CH4 emission seemed controlled primarily by the degree of rhizospheric CH4 oxidation which was between 20 and 40% for Carex but >90% for both the other species. Our results point toward a direct and very important linkage between the plant species
composition and the functioning of wetland ecosystems and indicate that changes in the species composition may alter important
processes relating to controls of and interactions between greenhouse gas fluxes with significant implications for feedback
mechanisms in a changing climate as a result. 相似文献
19.
Elevated UV-B radiation alters fluxes of methane and carbon dioxide in peatland microcosms 总被引:7,自引:0,他引:7
Riikka Niemi Pertti J. Martikainen† Jouko Silvola‡ Anu Wulff Satu Turtola Toini Holopainen 《Global Change Biology》2002,8(4):361-371
Increases in solar ultraviolet‐B radiation (UV‐B; 280–320 nm) reaching the earth have been estimated to continue until 2050s in the boreal and subarctic regions with an abundant peatland cover. Peatlands are significant sinks for carbon dioxide (CO2) and sources for methane (CH4). To assess whether the future increases in UV‐B could affect the fluxes of CO2 and CH4 in peatlands via an impact on vegetation, we exposed peatland microcosms to modulated 30% supplementation of erythemally weighted UV‐B at an outdoor facility for one growing season. The experimental design included appropriate controls for UV‐A and ambient radiation. The UV‐B caused a significant reduction in gross photosynthesis, net ecosystem CO2 exchange, and CH4 emission of the peatland microcosms. These changes in the carbon gas cycling can be partly explained by UV‐B‐induced morphological changes in Eriophorum vaginatum which acts as a conduit for CH4. Leaf cross section and the percentage of CH4‐conducting aerenchymatous tissue in E. vaginatum were significantly reduced by UV‐B. Methanol‐extractable UV‐B absorbing compounds decreased under both UV‐B and UV‐A in Sphagnum angustifolium, and tended to accumulate under UV‐B in S. papillosum. Membrane permeability to magnesium (Mg) and calcium (Ca) ions was higher in UV‐B exposed S. angustifolium. Amount of chlorophyll and carotenoid pigments was increased by UV‐A in S. magellanicum. The observed changes in Sphagnum mosses did not coincide with those in carbon gas fluxes but occurred at the time of the highest UV intensity in the mid summer. Our findings indicate that increasing UV‐B may have more substantial effects on gas exchange in peatlands than previously thought. 相似文献
20.
为了更好理解若尔盖高原不同微生境下沼泽湿地生态系统CO2排放通量的变化特征,以若尔盖高原湿地自然保护区为研究对象,2013和2014年生长季期间,采用了静态箱和快速温室气体法原位观测了3种湿地5种微生境下沼泽湿地CO2排放通量时空变化规律。结果表明:长期淹水微地貌草丘区湿地(PHK)和洼地区湿地(PHW) CO2排放通量变化范围分别为38.99-1731.74 mg m-2 h-1和46.69-335.22 mg m-2 h-1,季节性淹水区微地貌草丘区湿地(SHK)和洼地区湿地(SHW) CO2排放通量变化范围分别为193.90-2575.60 mg m-2 h-1和49.93-1467.45 mg m-2 h-1,而两者过渡区的无淹水区沼泽湿地(Lawn) CO2排放通量变化范围194.20-898.75 mg m-2 h-1。相关性分析表明5种微地貌区沼泽湿地CO2排放通量季节性变化与不同深度土壤温度均存在显著正相关,与水位存在显著负相关(PHW、SHW、SHK、Lawn)或不相关(PHK),并且水位和温度(5 cm)共同解释了CO2排放通量季节性变化的87%。3种湿地5种微生境下沼泽湿地CO2排放通量存在空间变化规律,主要受水位影响,但植物也影响沼泽湿地CO2排放通量空间变化规律,并且表明沼泽湿地CO2排放通量与水位平均值存在显著负相关。 相似文献