三江源高寒草甸下溪流溶解性有机碳的季节性输移特征
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摘要
溶解性有机碳(DOC)在生态系统中起着重要作用,但河流DOC输移动态及其对气候变化和多年冻土退化的响应还不清楚。对青藏高原三江源地区高寒草甸下8条小流域河流于2016年8月至2017年7月进行逐月采集水样,同步测定流量,在室内对DOC浓度进行分析,研究河流DOC浓度和输移通量的逐月变化规律以及对降雨和温度逐月变化的响应。结果表明:(1) DOC的年平均浓度介于4. 05±1. 20～6. 55±2. 86 mg·L~(-1)之间,均值为5. 30 mg·L-1; DOC平均浓度与流域内高寒沼泽草甸(ASM)覆盖面积比例呈显著线性负相关,而与高寒草甸(AM)呈显著线性正相关;此外,有多年冻土发育的流域内河流平均DOC浓度明显高于无多年冻土发育的流域。(2) DOC浓度随季节性气温的变化呈现较大的变异性,在-8～2℃气温回升的过程中,DOC平均浓度随气温的升高呈急剧上升的趋势,在随后2～13℃气温继续升高到最高的过程中,DOC平均浓度又急速降低,而在之后13～-8℃气温下降的过程中,DOC平均浓度呈一个缓慢降低的趋势,并在12月达到最低。(3) DOC平均输移通量也显示出较大的季节差异,其范围为0. 006±0. 000 5～3. 01±0. 74 kg·km~(-2)·d~(-1),均值为1. 12±0. 81 kg·km~(-2)·d~(-1); DOC输移通量与流域内平均径流量显著线性正相关,DOC的输移主要集中在春季融雪期和夏季丰雨期。气候变暖会导致多年冻土活动层厚度增加,因此,温度增加导致DOC输移增加的结果提示,气候变暖可能会增加青藏高原高寒草甸区河流对有机碳输移和释放。
Dissolved organic carbon( DOC) plays an important role in ecosystem. Little is known about the dynamics of riverine DOC exports and their responses to climate change and permafrost degradation. To examine the seasonal variations of concentrations and exports of DOC and their responses to changes of air temperature and precipitation,we collected monthly river water samples from 8 catchments under alpine meadow in the Three Rivers' headwater regions on the Qinghai-Tibet Plateau from August 2016 to July 2017. The discharges in these rivers were monitored,and DOC concentrations of water samples were analyzed in the laboratory. The results showed:( 1) The annual average DOC concentrations of these streams varied from( 4. 05±1. 20) mg·L~(-1) to( 6. 55±2. 86) mg·L~(-1),with an mean value of 5. 30 mg·L~(-1). The DOC concentrations were significantly negatively correlated with the coverage area of alpine swamp meadow( ASM),but significantly correlated with the coverage of alpine meadow( AM). The average DOC concentrations in the rivers in permafrost regions were significantly higher than those in non-permafrost regions.( 2) The DOC concentrations showed a great variations with seasonal changes of air temperature. From the spring to the beginning of summer, DOC concentrations increased sharply. During this period, the monthly mean air temperature increased from-8℃ to 2℃. The DOC concentrations decreased rapidly as the air temperature increased from 2℃ to 13℃. From summer to winter,the temperature decreased from 13℃ to-8℃. Meanwhile,the average DOC concentrations decreased gradually,and the lowest value was recorded in December.( 3) The seasonal changes of DOC export varied greatly,ranging from( 0. 006 ± 0. 0005) kg ·km~(-2)·d~(-1) and( 3. 01 ± 0. 74) kg ·km~(-2)·d~(-1) among the rivers,with an average value of( 1. 12±0. 81) kg·km~(-2)·d~(-1). DOC export fluxes were positively correlated with the discharges. The highest DOC export was recorded in the spring snowmelt period and the rainy summer. Since the climate change may lead to a thicker active layer in permafrost regions,our results showed that the DOC export increased along with temperature,indicating that climate warming can cause a higher DOC export in alpine meadow in the permafrost regions on the Qinghai-Tibetan Plateau.
Dissolved organic carbon( DOC) plays an important role in ecosystem. Little is known about the dynamics of riverine DOC exports and their responses to climate change and permafrost degradation. To examine the seasonal variations of concentrations and exports of DOC and their responses to changes of air temperature and precipitation,we collected monthly river water samples from 8 catchments under alpine meadow in the Three Rivers' headwater regions on the Qinghai-Tibet Plateau from August 2016 to July 2017. The discharges in these rivers were monitored,and DOC concentrations of water samples were analyzed in the laboratory. The results showed:( 1) The annual average DOC concentrations of these streams varied from( 4. 05±1. 20) mg·L~(-1) to( 6. 55±2. 86) mg·L~(-1),with an mean value of 5. 30 mg·L~(-1). The DOC concentrations were significantly negatively correlated with the coverage area of alpine swamp meadow( ASM),but significantly correlated with the coverage of alpine meadow( AM). The average DOC concentrations in the rivers in permafrost regions were significantly higher than those in non-permafrost regions.( 2) The DOC concentrations showed a great variations with seasonal changes of air temperature. From the spring to the beginning of summer, DOC concentrations increased sharply. During this period, the monthly mean air temperature increased from-8℃ to 2℃. The DOC concentrations decreased rapidly as the air temperature increased from 2℃ to 13℃. From summer to winter,the temperature decreased from 13℃ to-8℃. Meanwhile,the average DOC concentrations decreased gradually,and the lowest value was recorded in December.( 3) The seasonal changes of DOC export varied greatly,ranging from( 0. 006 ± 0. 0005) kg ·km~(-2)·d~(-1) and( 3. 01 ± 0. 74) kg ·km~(-2)·d~(-1) among the rivers,with an average value of( 1. 12±0. 81) kg·km~(-2)·d~(-1). DOC export fluxes were positively correlated with the discharges. The highest DOC export was recorded in the spring snowmelt period and the rainy summer. Since the climate change may lead to a thicker active layer in permafrost regions,our results showed that the DOC export increased along with temperature,indicating that climate warming can cause a higher DOC export in alpine meadow in the permafrost regions on the Qinghai-Tibetan Plateau.
引文
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[2]WINTERDAHL M,LAUDO H,LYON S W,et al.Sensitivity of stream dissolved organic carbon to temperature and discharge:Implications of future climates[J].Journal of Geophysical Research:Biogeosciences,2016,121(1):126-144.
[3]LAUDO H,BUTTLE J,CAREY S K,et al.Cross-regional prediction of long-term trajectory of stream water DOC response to climate change[J].Geophysical Research Letters,2012,39(18):L18404.
[4]MONTEITH D T,STODDARD J L,EVANS C D,et al.Dissolved organic carbon trends resulting from changes in atmospheric deposition chemistry[J].Nature,2007,450(7169):537-540.
[5]KAPLAN L A,NEWBOLD J D,HORN D J V,et al.Organic matter transport in New York City drinking-water-supply watersheds[J].Journal of the North American Benthological Society,2006,25(4):912-927.
[6]WU X,FANG H,ZHAO L,et al.Mineralisation and changes in the fractions of soil organic matter in soils of the permafrost Region,Qinghai-Tibet Plateau,China[J].Permafrost and Periglacial Processes,2014,25(1):35-44.
[7]ZOU D,ZHAO L,SHENG Y,et al.A new map of permafrost distribution on the Tibetan Plateau[J].The Cryosphere,2017,11(6):2527.
[8]MU C,ZHANG T,WU Q,et al.Organic carbon pools in permafrost regions on the Qinghai-Xizang(Tibetan)Plateau[J].The Cryosphere,2015,9(2):479-486.
[9]KAISER K,KALBITZ K.Cycling downwards-dissolved organic matter in soils[J].Soil Biology and Biochemistry,2012,52:29-32.
[10]ABBOTT B W,LAROUCHE J R,JONES J B,et al.Elevated dissolved organic carbon biodegradability from thawing and collapsing permafrost[J].Journal of Geophysical Research:Biogeosciences,2015,119(10):2049-2063.
[11]OLEFELDT D,ROULET N T.Effects of permafrost and hydrology on the composition and transport of dissolved organic carbon in a subarctic peatland complex[J].Journal of Geophysical Research:Biogeosciences,2012,117(G1):273-279.
[12]WU X,ZHAO L,HU G,et al.Permafrost and land cover as controlling factors for light fraction organic matter on the southern Qinghai-Tibetan plateau[J].Science of the Total Environment,2018,613:1165-1174.
[13]徐玲玲,张宪洲,石培礼,等.青藏高原高寒草甸生态系统净二氧化碳交换量特征[J],生态学报,2005,25(8):1948-1952.XU L L,ZHANG X Z,SHI P L,et al.Net ecosystem carbon dioxide exchange of alpine meadow in the Tibetan Plateau from August to October[J].Acta Ecologica Sinica,2005,25(8):1948-1952.
[14]MU C,ZHANG T,ZHAO Q,et al.Permafrost affects carbon exchange and its response to experimental warming on the northern Qinghai-Tibetan Plateau[J].Agricultural and Forest Meteorology,2017,247:252-259.
[15]LAUDON H,HEDTJRNJ J,SCHELKER J,et al.Response of dissolved organic carbon following forest harvesting in a boreal forest[J].AMBIO:A Journal of the Human Environment,2009,38(7):381-386.
[16]FREY K E,SMITH L C.Amplified carbon release from vast West Siberian peatlands by 2100[J].Geophysical Research Letters,2005,32(9):L09401.
[17]NEFF J C,HOOPER D U.Vegetation and climate controls on potential CO2,DOC and DON production in northern latitude soils[J].Global Change Biology,2002,8(9):872-884.
[18]WALLENSTEIN M D,WEINTRAUB M N.Emerging tools for measuring and modeling the in situ activity of soil extracellular enzymes[J].Soil Biology and Biochemistry,2008,40(9):2098-2106.
[19]LAUDON H,BERGGRENB M,GREN A,et al.Patterns and dynamics of dissolved organic carbon(DOC)in boreal streams:the role of processes,connectivity,and scaling[J].Ecosystems,2011,14(6):880-893.
[20]WANG Z,WANG Q,ZAHO L,et al.Mapping the vegetation distribution of the permafrost zone on the Qinghai-Tibet Plateau[J].Journal of Mountain Science.2016,13(6):1035-1046.
[21]MATTSSON T,KORTELAINEN P,RIKE A.Export of DOMfrom boreal catchments:impacts of land use cover and climate[J].Biogeochemistry,2005,76(2):373-394.
[22]JOHANSSON T,MALMER N,CRILL P M,et al.Decadal vegetation changes in a northern peatland,greenhouse gas fluxes and net radiative forcing[J].Global Change Biology,2006,12(12):2352-2369.
[23]WALLIN M B,WEYHENMEYER G A,BASTVIKEN D,et al.Temporal control on concentration,character,and export of dissolved organic carbon in two hemiboreal headwater streams draining contrasting catchments[J].Journal of Geophysical Research:Biogeosciences,2015,120(5):832-846.
[24]王烁,孙自永,胡雅璐,等.高寒山区典型小流域河流溶解性有机碳输出的年内变化及其成因[J].安全与环境工程,2017,24(2):1-7.WANG S;SUN Z Y;HU Y L,et al.Intra-annual variation of dissolved organic carbon export through stream from an typical alpine catchment in Qinghai-Tibet Plateau:patterns and hydrological controls[J].Safety and Environmental Engineering,2017,24(2):1-7.
[25]MU C C,ABBOTT B W,WU X D,et al.Thaw depth determines dissolved organic carbon concentration and biodegradability on the northern Qinghai-Tibetan Plateau[J].Geophysical Research Letters,2017,44(18):9389-9399.
[26]CAREY S K.Dissolved organic carbon fluxes in a discontinuous permafrost subarctic alpine catchment[J].Permafrost and Periglacial Processes,2003,14(2):161-171.
[27]WU X,FANG H,ZHAO Y,et al.A conceptual model of the controlling factors of soil organic carbon and nitrogen densities in a permafrost-affected region on the eastern Qinghai-Tibetan Plateau[J].Journal of Geophysical Research:Biogeosciences,2017122(7):1705-1717.
[28]MOORE T R,TURUNEN J.Carbon accumulation and storage in mineral subsoil beneath peat[J].Soil Science Society of America Journal,2004,68(2):690-696.
[29]CLARK J M,ASHLEY D,WAGNER M,et al.Increased temperature sensitivity of net DOC production from ombrotrophic peat due to water table draw-down[J].Global Change Biology,2009,15(4):794-807.
[30]TANK S E,FREY K E,STIEGL R G,et al.Landscape-level controls on dissolved carbon flux from diverse catchments of the circumboreal[J].Global Biogeochemical Cycles,2012,26(4):GB0E02.
[31]HOBBIE S E,SCHIMEL J P,TRUMBORE S E,et al.Controls over carbon storage and turnover in high-latitude soils[J].Global Change Biology,2000,6(S1):196-210.
[32]DAVIDSON E A,JANSSENS I A.Temperature sensitivity of soil carbon decomposition and feedbacks to climate change[J].Nature,2006,440(7081):165-173.
[33]TIERNEY G L,FAHEY T J,GROFFMAN P M,et al.Soil freezing alters fine root dynamics in a northern hardwood forest[J].Biogeochemistry,2001,56(2):175-190.
[34]KREYLING J,HAEI M,LAUDON H.Snow removal reduces annual cellulose decomposition in a riparian boreal forest[J].Canadian Journal of Soil Science,2013,93(4):427-433.
[35]PANNEER S B,LAUDON H,GUILLEMETTE F,et al.Influence of soil frost on the character and degradability of dissolved organic carbon in boreal forest soils[J].Journal of Geophysical Research:Biogeosciences,2016,121(3):829-840.
[36]WALVOORD M A,VOSS C I,WELLMAN T P.Influence of permafrost distribution on groundwater flow in the context of climate-driven permafrost thaw:Example from Yukon Flats Basin,Alaska,United States[J].Water Resources Research,2012,48(7):W07524.
[2]WINTERDAHL M,LAUDO H,LYON S W,et al.Sensitivity of stream dissolved organic carbon to temperature and discharge:Implications of future climates[J].Journal of Geophysical Research:Biogeosciences,2016,121(1):126-144.
[3]LAUDO H,BUTTLE J,CAREY S K,et al.Cross-regional prediction of long-term trajectory of stream water DOC response to climate change[J].Geophysical Research Letters,2012,39(18):L18404.
[4]MONTEITH D T,STODDARD J L,EVANS C D,et al.Dissolved organic carbon trends resulting from changes in atmospheric deposition chemistry[J].Nature,2007,450(7169):537-540.
[5]KAPLAN L A,NEWBOLD J D,HORN D J V,et al.Organic matter transport in New York City drinking-water-supply watersheds[J].Journal of the North American Benthological Society,2006,25(4):912-927.
[6]WU X,FANG H,ZHAO L,et al.Mineralisation and changes in the fractions of soil organic matter in soils of the permafrost Region,Qinghai-Tibet Plateau,China[J].Permafrost and Periglacial Processes,2014,25(1):35-44.
[7]ZOU D,ZHAO L,SHENG Y,et al.A new map of permafrost distribution on the Tibetan Plateau[J].The Cryosphere,2017,11(6):2527.
[8]MU C,ZHANG T,WU Q,et al.Organic carbon pools in permafrost regions on the Qinghai-Xizang(Tibetan)Plateau[J].The Cryosphere,2015,9(2):479-486.
[9]KAISER K,KALBITZ K.Cycling downwards-dissolved organic matter in soils[J].Soil Biology and Biochemistry,2012,52:29-32.
[10]ABBOTT B W,LAROUCHE J R,JONES J B,et al.Elevated dissolved organic carbon biodegradability from thawing and collapsing permafrost[J].Journal of Geophysical Research:Biogeosciences,2015,119(10):2049-2063.
[11]OLEFELDT D,ROULET N T.Effects of permafrost and hydrology on the composition and transport of dissolved organic carbon in a subarctic peatland complex[J].Journal of Geophysical Research:Biogeosciences,2012,117(G1):273-279.
[12]WU X,ZHAO L,HU G,et al.Permafrost and land cover as controlling factors for light fraction organic matter on the southern Qinghai-Tibetan plateau[J].Science of the Total Environment,2018,613:1165-1174.
[13]徐玲玲,张宪洲,石培礼,等.青藏高原高寒草甸生态系统净二氧化碳交换量特征[J],生态学报,2005,25(8):1948-1952.XU L L,ZHANG X Z,SHI P L,et al.Net ecosystem carbon dioxide exchange of alpine meadow in the Tibetan Plateau from August to October[J].Acta Ecologica Sinica,2005,25(8):1948-1952.
[14]MU C,ZHANG T,ZHAO Q,et al.Permafrost affects carbon exchange and its response to experimental warming on the northern Qinghai-Tibetan Plateau[J].Agricultural and Forest Meteorology,2017,247:252-259.
[15]LAUDON H,HEDTJRNJ J,SCHELKER J,et al.Response of dissolved organic carbon following forest harvesting in a boreal forest[J].AMBIO:A Journal of the Human Environment,2009,38(7):381-386.
[16]FREY K E,SMITH L C.Amplified carbon release from vast West Siberian peatlands by 2100[J].Geophysical Research Letters,2005,32(9):L09401.
[17]NEFF J C,HOOPER D U.Vegetation and climate controls on potential CO2,DOC and DON production in northern latitude soils[J].Global Change Biology,2002,8(9):872-884.
[18]WALLENSTEIN M D,WEINTRAUB M N.Emerging tools for measuring and modeling the in situ activity of soil extracellular enzymes[J].Soil Biology and Biochemistry,2008,40(9):2098-2106.
[19]LAUDON H,BERGGRENB M,GREN A,et al.Patterns and dynamics of dissolved organic carbon(DOC)in boreal streams:the role of processes,connectivity,and scaling[J].Ecosystems,2011,14(6):880-893.
[20]WANG Z,WANG Q,ZAHO L,et al.Mapping the vegetation distribution of the permafrost zone on the Qinghai-Tibet Plateau[J].Journal of Mountain Science.2016,13(6):1035-1046.
[21]MATTSSON T,KORTELAINEN P,RIKE A.Export of DOMfrom boreal catchments:impacts of land use cover and climate[J].Biogeochemistry,2005,76(2):373-394.
[22]JOHANSSON T,MALMER N,CRILL P M,et al.Decadal vegetation changes in a northern peatland,greenhouse gas fluxes and net radiative forcing[J].Global Change Biology,2006,12(12):2352-2369.
[23]WALLIN M B,WEYHENMEYER G A,BASTVIKEN D,et al.Temporal control on concentration,character,and export of dissolved organic carbon in two hemiboreal headwater streams draining contrasting catchments[J].Journal of Geophysical Research:Biogeosciences,2015,120(5):832-846.
[24]王烁,孙自永,胡雅璐,等.高寒山区典型小流域河流溶解性有机碳输出的年内变化及其成因[J].安全与环境工程,2017,24(2):1-7.WANG S;SUN Z Y;HU Y L,et al.Intra-annual variation of dissolved organic carbon export through stream from an typical alpine catchment in Qinghai-Tibet Plateau:patterns and hydrological controls[J].Safety and Environmental Engineering,2017,24(2):1-7.
[25]MU C C,ABBOTT B W,WU X D,et al.Thaw depth determines dissolved organic carbon concentration and biodegradability on the northern Qinghai-Tibetan Plateau[J].Geophysical Research Letters,2017,44(18):9389-9399.
[26]CAREY S K.Dissolved organic carbon fluxes in a discontinuous permafrost subarctic alpine catchment[J].Permafrost and Periglacial Processes,2003,14(2):161-171.
[27]WU X,FANG H,ZHAO Y,et al.A conceptual model of the controlling factors of soil organic carbon and nitrogen densities in a permafrost-affected region on the eastern Qinghai-Tibetan Plateau[J].Journal of Geophysical Research:Biogeosciences,2017122(7):1705-1717.
[28]MOORE T R,TURUNEN J.Carbon accumulation and storage in mineral subsoil beneath peat[J].Soil Science Society of America Journal,2004,68(2):690-696.
[29]CLARK J M,ASHLEY D,WAGNER M,et al.Increased temperature sensitivity of net DOC production from ombrotrophic peat due to water table draw-down[J].Global Change Biology,2009,15(4):794-807.
[30]TANK S E,FREY K E,STIEGL R G,et al.Landscape-level controls on dissolved carbon flux from diverse catchments of the circumboreal[J].Global Biogeochemical Cycles,2012,26(4):GB0E02.
[31]HOBBIE S E,SCHIMEL J P,TRUMBORE S E,et al.Controls over carbon storage and turnover in high-latitude soils[J].Global Change Biology,2000,6(S1):196-210.
[32]DAVIDSON E A,JANSSENS I A.Temperature sensitivity of soil carbon decomposition and feedbacks to climate change[J].Nature,2006,440(7081):165-173.
[33]TIERNEY G L,FAHEY T J,GROFFMAN P M,et al.Soil freezing alters fine root dynamics in a northern hardwood forest[J].Biogeochemistry,2001,56(2):175-190.
[34]KREYLING J,HAEI M,LAUDON H.Snow removal reduces annual cellulose decomposition in a riparian boreal forest[J].Canadian Journal of Soil Science,2013,93(4):427-433.
[35]PANNEER S B,LAUDON H,GUILLEMETTE F,et al.Influence of soil frost on the character and degradability of dissolved organic carbon in boreal forest soils[J].Journal of Geophysical Research:Biogeosciences,2016,121(3):829-840.
[36]WALVOORD M A,VOSS C I,WELLMAN T P.Influence of permafrost distribution on groundwater flow in the context of climate-driven permafrost thaw:Example from Yukon Flats Basin,Alaska,United States[J].Water Resources Research,2012,48(7):W07524.
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