Plant communities play an important role in the C-sink function of peatlands. However,global change and local perturbations are expected to modify peatland plant communities,leading to a shift from Sphagnum mosses to ...Plant communities play an important role in the C-sink function of peatlands. However,global change and local perturbations are expected to modify peatland plant communities,leading to a shift from Sphagnum mosses to vascular plants. Most studies have focused on the direct effects of modification in plant communities or of global change(such as climate warming, N fertilization) in peatlands without considering interactions between these disturbances that may alter peatlands' C function. We set up a mesocosm experiment to investigate how Greenhouse Gas(CO_2, CH_4, N_2O) fluxes, and dissolved organic carbon(DOC)and total dissolved N(TN) contents are affected by a shift from Sphagnum mosses to Molinia caerulea dominated peatlands combined with N fertilization. Increasing N deposition did not alter the C fluxes(CO_2 exchanges, CH_4 emissions) or DOC content. The lack of N effect on the C cycle seems due to the capacity of Sphagnum to efficiently immobilize N. Nevertheless, N supply increased the N_2O emissions, which were also controlled by the plant communities with the presence of Molinia caerulea reducing N_2O emissions in the Sphagnum mesocosms. Our study highlights the role of the vegetation composition on the C and N fluxes in peatlands and their responses to the N deposition. Future research should now consider the climate change in interaction to plants community modifications due to their controls of peatland sensitivity to environmental conditions.展开更多
Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditio...Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditions due to global warming may affect the relations between Sphagnum mosses and vascular plants but also the competition among Sphagnum, and thus alter the accumulation of carbon on boreal wetlands. Sphagnum mosses are a plant genus with a favorable ability to grow in low solar irradiance and temperature conditions compared to vascular plants. This may be increasingly beneficial in increased wintertime temperatures and predated snowmelt conditions. To understand particularly the importance of early spring photosynthetic activity and thus the role of the length of growing season on carbon balance, we analyzed the CO<sub>2</sub> exchange of Sphagnum mosses with closed chamber technique in two categories of microtopographical habitats, hummocks and lawns, during four seasons 2010-2013 on a raised bog in Central Finland. During CO<sub>2</sub> exchange measurements, instantaneous net ecosystem exchange (NEE) and ecosystem respiration (RE) were measured. Our results show that the mean measured seasonal NEE, i.e. the instantaneous net carbon sequestration, of hummocks was generally only slightly higher than the NEE of lawns, but the mean measured seasonal RE of hummocks was clearly and significantly higher than the RE of lawns in every study year. A reason for the observed still higher seasonal carbon sequestration of hummocks than that of lawns besides the slightly higher rate of carbon accumulation was the longer duration of physiologically active growing season. Therefore, hummock-forming Sphagnum mosses exposed firstly from snow cover showed to get the extra time for photosynthesis and thus extra benefit compared to other mire plants. This may be further enhanced by the expansion of hummock-forming Sphagnum moss dominated raised bogs towards northern aapa-mire region due to the global warming.展开更多
We investigated the temperature dependency of photosynthetic rates for five Sphagnum species: Sphagnum palustre, S. fimbriatum in the Tadewara mire (south-western Japan in a warm-temperate zone) and S. papillosum, S. ...We investigated the temperature dependency of photosynthetic rates for five Sphagnum species: Sphagnum palustre, S. fimbriatum in the Tadewara mire (south-western Japan in a warm-temperate zone) and S. papillosum, S. fuscum, S. fallax in the East Ochiishi mire (north-eastern Japan in a cool-temperate zone) measuring photosynthetic light response within a temperature range between 5 and 40。C. The maximum photosynthetic rate was obtained at T = 35。C for S. palustre, S. fuscum and S. papillosum, and at T = 30。C for S. fimbriatum and S. fallax. Photosynthetic rates of all these species showed a maximum at 300 - 500 μmol·m-2·s-1 of PPFD and it decreased at higher PPFD (>500 μmol·m-2·s-1) under low temperature (5。C - 10。C). These results imply that Sphagnum species are not fully physiologically adapted to low temperature environments, although Sphagnum species distribute mostly in the circumpolar region.展开更多
当前氮沉降对湿地泥炭藓凋落物分解的影响还存在很大争议,并且亚热带湿地泥炭藓分解对氮沉降的响应研究鲜见报道.采用分解袋法,在鄂西南地区开展模拟氮沉降对泥炭藓凋落物分解影响的实验.模拟氮浓度设置4个水平,分别为N0(0 g m^(-2)a^(-...当前氮沉降对湿地泥炭藓凋落物分解的影响还存在很大争议,并且亚热带湿地泥炭藓分解对氮沉降的响应研究鲜见报道.采用分解袋法,在鄂西南地区开展模拟氮沉降对泥炭藓凋落物分解影响的实验.模拟氮浓度设置4个水平,分别为N0(0 g m^(-2)a^(-1))、N3(3 g m^(-2)a^(-1))、N6(6 g m^(-2)a^(-1))、N12(12 g m^(-2)a^(-1)),其中N0为对照(CK).野外分解3、6、9和12个月后,室内测定泥炭藓凋落物干重、灰分、总碳(C)、总氮(N)、C/N以及总酚含量,计算凋落物的质量残留率、总碳(C)残留率及总酚残留率.结果显示:(1)氮沉降对凋落物分解的影响取决于分解时间,且泥炭藓凋落物的分解主要发生在前6个月.分解12个月后,N3浓度的质量残留率较CK下降了11.91%,而N6、N12较CK分别增加了12.98%、10.43%.(2)氮沉降对凋落物灰分含量有一定影响,但是随分解时间的延长影响程度不同.凋落物的相对灰分含量和绝对灰分含量均随分解时间的增加呈显著增加趋势.(3)氮沉降对泥炭藓凋落物总碳(C)含量有显著的影响(P<0.05),分解时间对泥炭藓凋落物总碳(C)、总氮(N)及总酚含量存在显著影响(P<0.05),且氮沉降对泥炭藓凋落物总碳(C)含量的影响程度取决于分解时间.分解12个月后,凋落物中总碳(C)含量和C/N均较初始值有所下降,总氮(N)含量和总酚含量则有所增加.(4)凋落物质量残留率、总碳(C)残留率与总酚残留率呈现出较强的线性正相关.可见,氮沉降对泥炭藓分解在短期内有一定影响,但并不是简单地促进或抑制作用.展开更多
The Dajiuhu Basin at Shennongjia,located within typical East Asian Monsoon region,preserves a sub-alpine sphagnum peat deposition in its central area.The topmost 120 cm of the peat covers the last 4000 years according...The Dajiuhu Basin at Shennongjia,located within typical East Asian Monsoon region,preserves a sub-alpine sphagnum peat deposition in its central area.The topmost 120 cm of the peat covers the last 4000 years according to AMS 14C dating of pollen concentration.Carbon isotope ofα-cellulose,extracted from sphagnum peat,provides a quantitative reconstruction of atmospheric relative humidity,based on transfer functions of C3 plants carbon isotopic fractionation equation and the bryophyte photosynthesis CO_(2)absorption rate equation.δ13C,TOC and C/N variations reveal that the Dajiuhu area has experienced a long-term tendency to dry during 4000―1000 aBP,with a major transition happening around 3000 aBP.Four relative dry events are identified at 3400―3200,3000―2600,2200―2000 and 1600―1400 aBP,respectively,corresponding to those climate events documented in many global records.Three periodicities,664 a,302 a and 277 a enclosed in the atmospheric humidity of Dajiuhu are correlated to the cycles of solar activities.The weakening of East Asia summer monsoon during this period registered in the Dajiuhu peat is consistent with the synchronous weakening of Indian Monsoon.This trend may be attributed to gradual decrease of Northern Hemispheric summer solar insolation and the consequently southward migration of Intertropical Convergent Zone(ITCZ).展开更多
To investigate vertical changes of bacterial communities from living plants to the associated sediments and bacterial biogeo- chemical roles in peatland ecosystem, samples of different part of individual Sphagnum palu...To investigate vertical changes of bacterial communities from living plants to the associated sediments and bacterial biogeo- chemical 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. A1- pha-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.展开更多
A preliminary study of simulated thermal maturity has been conducted to evaluate the oil, gas and hydrocarbon generation potential of sphagnum coal in the Jinsuo brown coal basin, Yunnan Province and to understand the...A preliminary study of simulated thermal maturity has been conducted to evaluate the oil, gas and hydrocarbon generation potential of sphagnum coal in the Jinsuo brown coal basin, Yunnan Province and to understand the characteristics of the element composition and biomarkers in the course of thermal alteration. The experimental result was compared with that of xylitic coal, a kind of lithotype of soft brown coal. It is considered that sphagnum coal possesses the potential of forming economic accumulation of oil and gas. Its highest proportion of oil and hydrocarbon generation is 510 mg/g Corg. and 232.1 mg/g Corg. respectively. At an R_(ran)~° value of 2.51%, the ratio of gas generation from sphagnum coal attains to 620.5 ml/g Corg. In view of sphagnum coal being different from the conventional soft brown coal in various respects such as coal forming raw materials and enviroments as well as physico-chemical properties, it is Suggested as a special kind of source rock for coal-generated oil and gas.展开更多
为了解不同浓度氮素添加对亚热带贫营养泥炭地土壤碳组分的影响,对鄂西南贫营养泥炭地原位喷洒不同浓度的NH4Cl溶液,研究氮沉降下不同深度土壤的总碳(TC)、总氮(TN)及其碳组分含量.模拟氮沉降设置0(N0)、3(N3)、6(N6)、12 g m^(-2) a^(-...为了解不同浓度氮素添加对亚热带贫营养泥炭地土壤碳组分的影响,对鄂西南贫营养泥炭地原位喷洒不同浓度的NH4Cl溶液,研究氮沉降下不同深度土壤的总碳(TC)、总氮(TN)及其碳组分含量.模拟氮沉降设置0(N0)、3(N3)、6(N6)、12 g m^(-2) a^(-1) (N12)4个处理.结果表明:4年的氮添加显著增加了表层(0-10 cm)与亚表层(10-20 cm)土壤TC含量、表层土壤TN含量,并且总体上随着氮素浓度的增加呈现增加的趋势(N12>N6>N3>N0);氮添加显著增加了表层与亚表层土壤矿物结合态有机碳(MAOC)含量以及表层土壤颗粒态有机碳(POC)、可溶性有机碳(DOC)含量.其中,与N0处理相比,N12处理下表层、亚表层土壤MAOC含量显著增加,分别增加了23%、33.7%;表层土壤POC、DOC与TC、TN呈显著正相关关系,MAOC与TC呈显著正相关关系;亚表层土壤DOC与TN呈显著正相关关系,MAOC与TC呈显著正相关关系;对表层土壤TC贡献较大的是MAOC、TN和草本地上生物量,其次是POC;对亚表层土壤TC影响较大的是MAOC、TN和pH,其次是灌木地上生物量.上述研究表明氮添加主要通过增加MAOC进而显著增加土壤碳储量,结果为全球氮沉降背景下增强贫营养泥炭地碳汇能力提供了一定理论基础.展开更多
基金research conducted in the Labex VOLTAIRE (ANR-10-LABX-100-01)the financial support provided to the PIVOTS project by the Région Centre–Val de Loire:ARD 2020 program,CPER 2015-2020,the European Union who invests in Centre-Val de Loire with the European Regional Development Fundsupported by the AMIS(FAte and IMpact of AtmospherIc PollutantS)project funded by the European Union,under the Marie Curie Actions IRSES(International Research Staff Exchange Scheme),within the Seventh Framework ProgrammeFP7-PEOPLE-2011-IRSES
文摘Plant communities play an important role in the C-sink function of peatlands. However,global change and local perturbations are expected to modify peatland plant communities,leading to a shift from Sphagnum mosses to vascular plants. Most studies have focused on the direct effects of modification in plant communities or of global change(such as climate warming, N fertilization) in peatlands without considering interactions between these disturbances that may alter peatlands' C function. We set up a mesocosm experiment to investigate how Greenhouse Gas(CO_2, CH_4, N_2O) fluxes, and dissolved organic carbon(DOC)and total dissolved N(TN) contents are affected by a shift from Sphagnum mosses to Molinia caerulea dominated peatlands combined with N fertilization. Increasing N deposition did not alter the C fluxes(CO_2 exchanges, CH_4 emissions) or DOC content. The lack of N effect on the C cycle seems due to the capacity of Sphagnum to efficiently immobilize N. Nevertheless, N supply increased the N_2O emissions, which were also controlled by the plant communities with the presence of Molinia caerulea reducing N_2O emissions in the Sphagnum mesocosms. Our study highlights the role of the vegetation composition on the C and N fluxes in peatlands and their responses to the N deposition. Future research should now consider the climate change in interaction to plants community modifications due to their controls of peatland sensitivity to environmental conditions.
文摘Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditions due to global warming may affect the relations between Sphagnum mosses and vascular plants but also the competition among Sphagnum, and thus alter the accumulation of carbon on boreal wetlands. Sphagnum mosses are a plant genus with a favorable ability to grow in low solar irradiance and temperature conditions compared to vascular plants. This may be increasingly beneficial in increased wintertime temperatures and predated snowmelt conditions. To understand particularly the importance of early spring photosynthetic activity and thus the role of the length of growing season on carbon balance, we analyzed the CO<sub>2</sub> exchange of Sphagnum mosses with closed chamber technique in two categories of microtopographical habitats, hummocks and lawns, during four seasons 2010-2013 on a raised bog in Central Finland. During CO<sub>2</sub> exchange measurements, instantaneous net ecosystem exchange (NEE) and ecosystem respiration (RE) were measured. Our results show that the mean measured seasonal NEE, i.e. the instantaneous net carbon sequestration, of hummocks was generally only slightly higher than the NEE of lawns, but the mean measured seasonal RE of hummocks was clearly and significantly higher than the RE of lawns in every study year. A reason for the observed still higher seasonal carbon sequestration of hummocks than that of lawns besides the slightly higher rate of carbon accumulation was the longer duration of physiologically active growing season. Therefore, hummock-forming Sphagnum mosses exposed firstly from snow cover showed to get the extra time for photosynthesis and thus extra benefit compared to other mire plants. This may be further enhanced by the expansion of hummock-forming Sphagnum moss dominated raised bogs towards northern aapa-mire region due to the global warming.
文摘We investigated the temperature dependency of photosynthetic rates for five Sphagnum species: Sphagnum palustre, S. fimbriatum in the Tadewara mire (south-western Japan in a warm-temperate zone) and S. papillosum, S. fuscum, S. fallax in the East Ochiishi mire (north-eastern Japan in a cool-temperate zone) measuring photosynthetic light response within a temperature range between 5 and 40。C. The maximum photosynthetic rate was obtained at T = 35。C for S. palustre, S. fuscum and S. papillosum, and at T = 30。C for S. fimbriatum and S. fallax. Photosynthetic rates of all these species showed a maximum at 300 - 500 μmol·m-2·s-1 of PPFD and it decreased at higher PPFD (>500 μmol·m-2·s-1) under low temperature (5。C - 10。C). These results imply that Sphagnum species are not fully physiologically adapted to low temperature environments, although Sphagnum species distribute mostly in the circumpolar region.
文摘当前氮沉降对湿地泥炭藓凋落物分解的影响还存在很大争议,并且亚热带湿地泥炭藓分解对氮沉降的响应研究鲜见报道.采用分解袋法,在鄂西南地区开展模拟氮沉降对泥炭藓凋落物分解影响的实验.模拟氮浓度设置4个水平,分别为N0(0 g m^(-2)a^(-1))、N3(3 g m^(-2)a^(-1))、N6(6 g m^(-2)a^(-1))、N12(12 g m^(-2)a^(-1)),其中N0为对照(CK).野外分解3、6、9和12个月后,室内测定泥炭藓凋落物干重、灰分、总碳(C)、总氮(N)、C/N以及总酚含量,计算凋落物的质量残留率、总碳(C)残留率及总酚残留率.结果显示:(1)氮沉降对凋落物分解的影响取决于分解时间,且泥炭藓凋落物的分解主要发生在前6个月.分解12个月后,N3浓度的质量残留率较CK下降了11.91%,而N6、N12较CK分别增加了12.98%、10.43%.(2)氮沉降对凋落物灰分含量有一定影响,但是随分解时间的延长影响程度不同.凋落物的相对灰分含量和绝对灰分含量均随分解时间的增加呈显著增加趋势.(3)氮沉降对泥炭藓凋落物总碳(C)含量有显著的影响(P<0.05),分解时间对泥炭藓凋落物总碳(C)、总氮(N)及总酚含量存在显著影响(P<0.05),且氮沉降对泥炭藓凋落物总碳(C)含量的影响程度取决于分解时间.分解12个月后,凋落物中总碳(C)含量和C/N均较初始值有所下降,总氮(N)含量和总酚含量则有所增加.(4)凋落物质量残留率、总碳(C)残留率与总酚残留率呈现出较强的线性正相关.可见,氮沉降对泥炭藓分解在短期内有一定影响,但并不是简单地促进或抑制作用.
基金Supported by Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT0533)National Natural Science Foundation of China(Grant Nos.40671193 and 40631003)
文摘The Dajiuhu Basin at Shennongjia,located within typical East Asian Monsoon region,preserves a sub-alpine sphagnum peat deposition in its central area.The topmost 120 cm of the peat covers the last 4000 years according to AMS 14C dating of pollen concentration.Carbon isotope ofα-cellulose,extracted from sphagnum peat,provides a quantitative reconstruction of atmospheric relative humidity,based on transfer functions of C3 plants carbon isotopic fractionation equation and the bryophyte photosynthesis CO_(2)absorption rate equation.δ13C,TOC and C/N variations reveal that the Dajiuhu area has experienced a long-term tendency to dry during 4000―1000 aBP,with a major transition happening around 3000 aBP.Four relative dry events are identified at 3400―3200,3000―2600,2200―2000 and 1600―1400 aBP,respectively,corresponding to those climate events documented in many global records.Three periodicities,664 a,302 a and 277 a enclosed in the atmospheric humidity of Dajiuhu are correlated to the cycles of solar activities.The weakening of East Asia summer monsoon during this period registered in the Dajiuhu peat is consistent with the synchronous weakening of Indian Monsoon.This trend may be attributed to gradual decrease of Northern Hemispheric summer solar insolation and the consequently southward migration of Intertropical Convergent Zone(ITCZ).
基金supported by National Natural Science Foundation of China(Grant Nos.41072253,41130207)Special Funds for Basic Scientific Research of Central Colleges,China University of Geosciences(Wuhan)(Grant No.CUG120103)
文摘To investigate vertical changes of bacterial communities from living plants to the associated sediments and bacterial biogeo- chemical 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. A1- pha-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.
基金Presented at Youth Symposium on Organic Geochemistry held in May, 1987 in Guangzhou and supported by Organic Geochemistry Laboratory, Academia Sinica and China Coal Science Foundation.
文摘A preliminary study of simulated thermal maturity has been conducted to evaluate the oil, gas and hydrocarbon generation potential of sphagnum coal in the Jinsuo brown coal basin, Yunnan Province and to understand the characteristics of the element composition and biomarkers in the course of thermal alteration. The experimental result was compared with that of xylitic coal, a kind of lithotype of soft brown coal. It is considered that sphagnum coal possesses the potential of forming economic accumulation of oil and gas. Its highest proportion of oil and hydrocarbon generation is 510 mg/g Corg. and 232.1 mg/g Corg. respectively. At an R_(ran)~° value of 2.51%, the ratio of gas generation from sphagnum coal attains to 620.5 ml/g Corg. In view of sphagnum coal being different from the conventional soft brown coal in various respects such as coal forming raw materials and enviroments as well as physico-chemical properties, it is Suggested as a special kind of source rock for coal-generated oil and gas.
