青藏高原高寒草甸不同海拔梯度上增温和优势植物物种去除对生态系统碳通量的影响
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摘要
在青藏高原高寒草甸的两个海拔梯度(3200 m和4000 m)上开展实验,研究增温和优势植物物种去除对净生态系统CO_2交换量(NEE)、生态系统呼吸(ER)和生态系统总初级生产力(GEP)的影响。结果表明:在2017年生长季,两个海拔的GEP均高于ER,表明这两个生态系统在生长季均表现为碳汇。低海拔(3200 m)的增温对生态系统C通量没有显著的作用,原因可能是增温引起的水分限制。在较湿润的高海拔(4000 m)地区,增温显著提高了生态系统C通量,平均而言,增温引起的GEP增加量(2.30 mg CO_2/(m~2·s))高于ER (0.62mg CO2/(m~2·s)),导致NEE增加。两个海拔优势植物物种的去除对生态系统C通量均没有显著的作用,原因可能是剩余物种的补偿作用,因为去除处理对两个海拔的地上生物量(AGB)和地下生物量(BGB)的影响都不显著。增温和优势物种去除对两个海拔生态系统C通量没有显著的交互作用。研究结果揭示土壤湿度在调节高寒草甸生态系统C通量对气候变暖响应方面的重要性,单一优势植物物种的去除可能不会对物种丰富的生态系统C通量产生较大的影响。
Experiments were conducted to investigate the effects of warming and dominant plant species removal on net ecosystem CO_2 exchange(NEE), ecosystem respiration(ER) and gross ecosystem production(GEP) along elevational gradients(3200 m and 4000 m) in the alpine meadow on the Tibetan Plateau. The results showed that GEP was higher than ER at both elevations, indicating that both ecosystems were a net C sink during the growing season in 2017. At a lower elevation(3200 m), warming did not have a significant effect on ecosystem C flux due to water limitation caused by warming. At a wetter high elevation(4000 m), warming significantly stimulated ecosystem C fluxes, on average, the warming-induced increase in GEP(2.30 mg CO_2/(m~2·s)) was higher than that in ER(0.62 mg CO_2/(m~2·s)), leading to an increase in NEE. Dominant plant species removal did not have a significant effect on ecosystem C flux at either elevations, probably due to the compensatory effects of the remaining species, because the removal on above ground biomass(AGB) or below ground biomass(BGB) was not significant at both elevations. There was no significant interaction between warming and dominant species removal on the ecosystem C fluxes at either elevations. The results reveal the importance of soil moisture in mediating the response of ecosystem C flux to climate warming in alpine meadow ecosystems, and removal of a single dominant plant species may not have a significant impact on ecosystem C flux in species-rich regions.
Experiments were conducted to investigate the effects of warming and dominant plant species removal on net ecosystem CO_2 exchange(NEE), ecosystem respiration(ER) and gross ecosystem production(GEP) along elevational gradients(3200 m and 4000 m) in the alpine meadow on the Tibetan Plateau. The results showed that GEP was higher than ER at both elevations, indicating that both ecosystems were a net C sink during the growing season in 2017. At a lower elevation(3200 m), warming did not have a significant effect on ecosystem C flux due to water limitation caused by warming. At a wetter high elevation(4000 m), warming significantly stimulated ecosystem C fluxes, on average, the warming-induced increase in GEP(2.30 mg CO_2/(m~2·s)) was higher than that in ER(0.62 mg CO_2/(m~2·s)), leading to an increase in NEE. Dominant plant species removal did not have a significant effect on ecosystem C flux at either elevations, probably due to the compensatory effects of the remaining species, because the removal on above ground biomass(AGB) or below ground biomass(BGB) was not significant at both elevations. There was no significant interaction between warming and dominant species removal on the ecosystem C fluxes at either elevations. The results reveal the importance of soil moisture in mediating the response of ecosystem C flux to climate warming in alpine meadow ecosystems, and removal of a single dominant plant species may not have a significant impact on ecosystem C flux in species-rich regions.
引文
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[2]Luo Y,Wan S,Hui D,et al.Acclimatization of soil respiration to warming in a tall grass prairie.Nature,2001,413:622-625
[3]Melillo J M,Steudler P A,Aber J D,et al.Soil warming and carbon-cycle feedbacks to the climate system.Science,2002,298:2173-2176
[4]Cox P M,Betts R A,Jones C D,et al.Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model.Nature,2000,408:184-187
[5]Trumbore S.Carbon respired by terrestrial ecosystems-recent progress and challenges.Global Change Biology,2006,12(2):141-153
[6]Oberbauer S F,Tweedie C E,Welker J M,et al.Tundra CO2 fluxes in response to experimental warming across latitudinal and moisture gradients.Ecological Monographs,2007,77(2):221-238
[7]Wu Z,Dijkstra P,Koch G W,et al.Responses of terrestrial ecosystems to temperature and precipitation change:a meta-analysis of experimental manipulation.Global Change Biology,2011,17(2):927-942
[8]Peng F,You Q,Xu M,et al.Effects of warming and clipping on ecosystem carbon fluxes across two hydrologically contrasting years in an alpine meadow of the Qinghai-Tibet Plateau.PlosOne,2014,9(10):e109319
[9]Ganjurjav H,Gao Q,Zhang W,et al.Effects of warming on CO2 fluxes in an alpine meadow ecosystem on the central Qinghai-Tibetan Plateau.PlosOne,2015,10(7):e0132044
[10]Chapin III F S.Effects of plant traits on ecosystem and regional processes:a conceptual framework for predicting the consequences of global change.Annals of Botany,2003,91(4):455-463
[11]Sasaki T,Yoshihara Y,Takahashi M,et al.Differential responses and mechanisms of productivity following experimental species loss scenarios.Oecologia,2017,183(3):785-795
[12]Kato T,Tang Y,Gu S,et al.Temperature and biomass influences on interannual changes in CO2 exchange in an alpine meadow on the Qinghai-Tibetan Plateau.Global Change Biology,2006,12(7):1285-1298
[13]Genxu W,Ju Q,Guodong C,et al.Soil organic carbon pool of grassland soils on the Qinghai-Tibetan Plateau and its global implication.Science of the Total Environment,2002,291(1/2/3):207-217
[14]Diaz H F,Eischeid J K,Duncan C,et al.Variability of freezing levels,melting season indicators,and snow cover for selected high-elevation and continental regions in the last 50 years//Climate Variability and Change in High Elevation Regions:Past,Present&Future.Dordrecht:Springer,2003:33-52
[15]Zimmermann M,Meir P,Bird M I,et al.Temporal variation and climate dependence of soil respiration and its components along a 3000 m altitudinal tropical forest gradient.Global Biogeochemical Cycles,2010,24(4):GB4012
[16]Zhao L,Li Y,Xu S,et al.Diurnal,seasonal and annual variation in net ecosystem CO2 exchange of an alpine shrubland on Qinghai-Tibetan Plateau.Global Change Biology,2006,12(10):1940-1953
[17]Saito M,Kato T,Tang Y.Temperature controls ecosystem CO2 exchange of an alpine meadow on the northeastern Tibetan Plateau.Global Change Biology,2009,15(1):221-228
[18]Liu X,Chen B.Climatic warming in the Tibetan Plateau during recent decades.International Journal of Climatology,2000,20(14):1729-1742
[19]Tang Y,Wan S,He J,et al.Foreword to the special issue:looking into the impacts of global warming from the roof of the world.Journal of Plant Ecology,2009,2(4):169-171
[20]Smith M D,Knapp A K.Dominant species maintain ecosystem function with non-random species loss.Ecology Letters,2003,6(6):509-517
[21]McLaren J R,Turkington R.Ecosystem properties determined by plant functional group identity.Journal of Ecology,2010,98(2):459-469
[22]Kato T,Tang Y,Gu S,et al.Carbon dioxide exchange between the atmosphere and an alpine meadow ecosystem on the Qinghai-Tibetan Plateau,China.Agricultural and Forest Meteorology,2004,124(1/2):121-134
[23]De Boeck H J,Lemmens C,Gielen B,et al.Combined effects of climate warming and plant diversity loss on above-and below-ground grassland productivity.Environmental and Experimental Botany,2007,60(1):95-104
[24]Hanson P J,Edwards N T,Garten C T,et al.Separating root and soil microbial contributions to soil respiration:a review of methods and observations.Biogeochemistry,2000,48(1):115-146
[25]Saleska S R,Harte J N,Torn M S.The effect of experimental ecosystem warming on CO2 fluxes in a montane meadow.Global Change Biology,1999,5(2):125-141
[26]Lin X,Zhang Z,Wang S,et al.Response of ecosystem respiration to warming and grazing during the growing seasons in the alpine meadow on the Tibetan plateau.Agricultural and Forest Meteorology,2011,151(7):792-802
[27]Ka?tovskáE,Edwards K,Picek T,et al.A larger investment into exudation by competitive versus conservative plants is connected to more coupled plantmicrobe N cycling.Biogeochemistry,2015,122(1):47-59
[28]Legay N,Grassein F,Binet M N,et al.Plant species identities and fertilization influence on arbuscular mycorrhizal fungal colonisation and soil bacterial activities.Applied Soil Ecology,2016,98:132-139
[29]Lange M,Eisenhauer N,Sierra C A,et al.Plant diversity increases soil microbial activity and soil carbon storage.Nature Communications,2015,6:6707
[30]Fornara D A,Tilman D.Plant functional composition influences rates of soil carbon and nitrogen accumulation.Journal of Ecology,2008,96(2):314-322
[31]Steinbeiss S,Bessler H,Engels C,et al.Plant diversity positively affects short-term soil carbon storage in experimental grasslands.Global Change Biology,2008,14(12):2937-2949
[32]Balvanera P,Pfisterer A B,Buchmann N,et al.Quantifying the evidence for biodiversity effects on ecosystem functioning and services.Ecology Letters,2006,9(10):1146-1156
[33]Cardinale B J,Duffy J E,Gonzalez A,et al.Biodiversity loss and its impact on humanity.Nature,2012,486:59-67
[34]Symstad A J,Tilman D,Willson J,et al.Species loss and ecosystem functioning:effects of species identity and community composition.Oikos,1998,81(2):389-397
[35]Kotas P,Choma M,?antr??kováH,et al.Linking above-and belowground responses to 16 years of fertilization,mowing,and removal of the dominant species in a temperate grassland.Ecosystems,2017,20(2):354-367
[36]Mori A S,Furukawa T,Sasaki T.Response diversity determines the resilience of ecosystems to environmental change.Biological Reviews,2013,88(2):349-364
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