Biophysical Regulation of Carbon Flux in Different Rainfall Regime in a Northern Tibetan Alpine Meadow

doi:10.5814/j.issn.1674-764x.2017.01.005

Abstract

Abstract:

Inter-annual variability in total precipitation can lead to significant changes in carbon flux. In this study, we used the eddy covariance (EC) technique to measure the net CO₂ ecosystem exchange (NEE) of an alpine meadow in the northern Tibetan Plateau. In 2005 the meadow had precipitation of 489.9 mm and in 2006 precipitation of 241.1 mm, which, respectively, represent normal and dry years as compared to the mean annual precipitation of 476 mm. The EC measured NEE was 87.70 g C m^-2yr^-1in 2006 and -2.35 g C m^-2yr^-1 in 2005. Therefore, the grassland was carbon neutral to the atmosphere in the normal year, while it was a carbon source in the dry year, indicating this ecosystem will become a CO₂ source if climate warming results in more drought conditions. The drought conditions in the dry year limited gross ecosystem CO₂ exchange (GEE), leaf area index (LAI) and the duration of ecosystem carbon uptake. During the peak of growing season the maximum daily rate of NEE and P_max and α were approximately 30%-50% of those of the normal year. GEE and NEE were strongly related to photosynthetically active radiation (PAR) on half-hourly scale, but this relationship was confounded by air temperature (T_a), soil water content (SWC) and vapor pressure deficit (VPD). The absolute values of NEE declined with higher T_a, higher VPD and lower SWC conditions. Beyond the appropriate range of PAR, high solar radiation exacerbated soil water conditions and thus reduced daytime NEE. Optimal T_a and VPD for maximum daytime NEE were 12.7℃ and 0.42 KPa respectively, and the absolute values of NEE increased with SWC. Variation in LAI explained around 77% of the change in GEE and NEE. Variations in R_e were mainly controlled by soil temperature (T_s), whereas soil water content regulated the responses of Re to T_s.

Key words: alpine meadow, depression, different rainfall regime, Tibetan Plateau, water stress, CO₂ flux

CHAI Xi, SHI Peili, ZONG Ning, NIU Ben, HE Yongtao, ZHANG Xianzhou. Biophysical Regulation of Carbon Flux in Different Rainfall Regime in a Northern Tibetan Alpine Meadow[J]. Journal of Resources and Ecology, 2017, 8(1): 30-41.

References

[1] Adams J.M., Faure H., Fauredenard, L. et al. 1990. Increases in terrestrial carbon storage from the Last Glacial Maximum to the Present. Nature , 348(6303): 711-714.
[2] Aires L.M.I., Pio C.A., Pereira J.S. 2008. Carbon dioxide exchange above a Mediterranean C3/C4 grassland during two climatologically contrasting years. Global Change Biology , 14(3): 539-555.
[3] Boone R.D., Nadelhoffer K.J., Canary J.D. et al. 1998. Roots exert a strong influence on the temperature sensitivityof soil respiration. Nature , 396(6711): 570-572.
[4] Carrara A., Janssens I.A., Yuste J.C. et al. 2004. Seasonal changes in photosynthesis, respiration and NEE of a mixed temperate forest. Agricultural & Forest Meteorology , 126(1): 15-31.
[5] Chen S., Liu Y., Thomas A. 2006. Climatic change on the Tibetan Plateau: potential evapotranspiration trends from 1961-2000. Climatic Change , 76(3): 291-319.
[6] Fan Y., Zhang X., Wang J. et al. 2011. Effect of solar radiation on net ecosystem CO 2 exchange of alpine meadow on the Tibetan Plateau. Journal of Geographical Sciences , 21(4): 666-676.
[7] Flanagan L.B. 2002. Seasonal and interannual variation in carbon dioxide exchange and carbon balance in a northern temperate grassland. Global Change Biology , 8(7): 599-615.
[8] Fu Y.L., Yu G.R., Sun X.M. et al. 2006. Depression of net ecosystem CO 2 exchange in semi-arid Leymus chinensis steppe and alpine shrub. Agricultural and Forest Meteorology , 137(3): 234-244.
[9] Gao Y., Cooper D.J., Ma X. 2016. Phosphorus additions have no impact on plant biomass or soil nitrogen in an alpine meadow on the Qinghai-Tibetan Plateau, China. Applied Soil Ecology , 106: 18-23.
[10] Gilmanov T.G., Aires L., Barcza Z. et al. 2010. Productivity, respiration, and light-response parameters of world grassland and agroecosystems derived From flux-tower measurements. Rangeland Ecology & Management , 63(1): 16-39.
[11] Gilmanov T.G., Soussana J.F., Aires L. et al. 2007. Partitioning European grassland net ecosystem CO2 exchange into gross primary productivity and ecosystem respiration using light response function analysis. Agriculture, Ecosystems & Environment , 121(1-2): 93-120.
[12] Gilmanov T.G., Tieszen L.L., Wylie B.K. et al. 2005. Integration of CO 2 flux and remotely-sensed data for primary production and ecosystem respiration analyses in the Northern Great Plains: potential for quantitative spatial extrapolation. Global Ecology and Biogeography , 14(3): 271-292.
[13] Goldstein A.H., Hultman N.E., Fracheboud J.M. et al. 2000. Effects of climate variability on the carbon dioxide, water, and sensible heat fluxes above a ponderosa pine plantation in the Sierra Nevada (CA). Agricultural & Forest Meteorology , 101(2-3): 113-129.
[14] Gu S. 2003. Short-term variation of CO 2 flux in relation to environmental controls in an alpine meadow on the Qinghai-Tibetan Plateau. Journal of Geophysical Research , 108(D21): 1981-1990.
[15] Hall D.O., Scurlock J.M.O. 1991. Climate change and productivity of natural grasslands. Annals of botany , 67(supp1): 49-55.
[16] Harper C.W., Blair J.M., Fay P.A. et al. 2005. Increased rainfall variability and reduced rainfall amount decreases soil CO 2 flux in a grassland ecosystem. Global Change Biology , 11(2): 322-334.
[17] Harris R.B. 2010. Rangeland degradation on the Qinghai-Tibetan plateau: A review of the evidence of its magnitude and causes. Journal of Arid Environments , 74(1): 1-12.
[18] Heisler-White J.L., Knapp A.K., Kelly E.F. 2008. Increasing precipitation event size increases aboveground net primary productivity in a semi-arid grassland. Oecologia , 158(1): 129-140.
[19] Hunt J.E. 2002. Evaporation and carbon dioxide exchange between the atmosphere and a tussock grassland during a summer drought. Agricultural and Forest Meteorology , 111(1): 65-82.
[20] Huxman T.E., Snyder K.A., Tissue D. et al. 2004. Precipitation pulses and carbon fluxes in semiarid and arid ecosystems. Oecologia , 141(2): 254-268.
[21] Jaksic V., Kiely G., Albertson J. et al. 2006. Net ecosystem exchange of grassland in contrasting wet and dry years. Agricultural and Forest Meteorology , 139(3-4): 323-334.
[22] Jia X., Zha T.S., Wu B. et al. 2014. Biophysical controls on net ecosystem CO 2 exchange over a semiarid shrubland in northwest China. Biogeosciences , 11(3): 4679-4693.
[23] Kato T. 2004. Seasonal patterns of gross primary production and ecosystem respiration in an alpine meadow ecosystem on the Qinghai-Tibetan Plateau. Journal of Geophysical Research , 109(D12): 1045-1056.
[24] Kato T., Tang Y., Gu S. et al. 2004. Carbon dioxide exchange between the atmosphere and an alpine meadow ecosystem on the Qinghai-Tibetan Plateau, China. Agricultural and Forest Meteorology , 124(1-2): 121-134.
[25] Kato T., Tang Y.H., Gu S. et al. 2006. Temperature and biomass influences on interannual changes in CO 2 exchange in an alpine meadow on the Qinghai-Tibetan Plateau. Global Change Biology , 12(7): 1285-1298.
[26] Knapp A.K., Smith M.D. 2001. Variation among biomes in temporal dynamics of aboveground primary production. Science , 291(5503): 481- 484.
[27] Li S.G., Asanuma J., Eugster W. et al. 2005. Net ecosystem carbon dioxide exchange over grazed steppe in central Mongolia. Global Change Biology , 11(11): 1941-1955.
[28] Liu R., Cieraad E., Li Y. et al. 2016. Precipitation pattern determines the inter-annual variation of herbaceous layer and carbon fluxes in a phreatophyte-dominated desert Ecosystem . Ecosystems , 19(4): 601-614.
[29] Lloyd J., Taylor J.A. 1994. On the temperature dependence of soil respiration. Functional Ecology , 8(3): 315-323.
[30] Luan J.W., Song H.T., Xiang C.H. et al. 2016. Soil moisture, species composition interact to regulate CO 2 and CH 4 fluxes in dry meadows on the Tibetan Plateau. Ecological Engineering , 91: 101-112.
[31] Meyers T.P. 2001. A comparison of summertime water and CO 2 fluxes over rangeland for well-watered and drought conditions. Agricultural & Forest Meteorology , 106: 205-214.
[32] Nagy Z., Pintér K., Czóbel et al. 2007. The carbon budget of semi-arid grassland in a wet and a dry year in Hungary. Agriculture Ecosystems & Environment , 121(1-2): 21-29.
[33] Nakano T., Nemoto M., Shinoda M. 2008. Environmental controls on photosynthetic production and ecosystem respiration in semi-arid grasslands of Mongolia. Agricultural and Forest Meteorology , 148(10): 1456- 1466.
[34] Orchard V.A., Cook F.J. 1983. Relationship between soil respiration and soil moisture. Soil Biology & Biochemistry , 15(4): 447-453.
[35] Pereira J.S., David J.S., David T.S. et al. 2004. Carbon and water fluxes in mediterranean-type ecosystems—constraints and adaptations. Springer Berlin Heidelberg , 65: 467-498.
[36] Piao S., Tan K., Nan H. et al. 2012. Impacts of climate and CO 2 changes on the vegetation growth and carbon balance of Qinghai-Tibetan grasslands over the past five decades. Global & Planetary Change , 98-99(6): 73-80.
[37] Polley H.W., Emmerich W., Bradford J.A. et al. 2010. Physiological and environmental regulation of interannual variability in CO 2 exchange on rangelands in the western United States. Global Change Biology , 16(3): 990-1002.
[38] Reichstein M., Valentini R. 2002. Ecosystem respiration in two Mediterranean evergreen Holm Oak forests: drought effects and decomposition dynamics. Functional Ecology , 16(1): 27-39.
[39] Ruimy A., Jarvis P.G., Baldocchi D.D. et al. 1995. CO 2 Fluxes over Plant Canopies and Solar Radiation: A Review. Advances in Ecological Research , 26(26): 1-68.
[40] Salvucci M. E., S. J. Crafts-Brandner 2004. Inhibition of photosynthesis by heat stress: the activation state of Rubisco as a limiting factor in photosynthesis. Physiologia Plantarum 120(2): 179-186.
[41] Shi, PL., Sun, X., Xu, L. et al. 2006. Net ecosystem CO 2 exchange and controlling factors in a steppe—Kobresia meadow on the Tibetan Plateau. Science in China Series D: Earth Sciences, 49(2): 207-218.
[42] Piao Sl, P., Fang J., Zhou L. et al. 2006. Variations in satellite‐derived phenology in China's temperate vegetation. Global Change Biology , 12(4): 672-685.
[43] Sowerby A., Emmett B. A., Tietema A. et al. 2008. Contrasting effects of repeated summer drought on soil carbon efflux in hydric and mesic heathland soils. Global Change Biology 14(10): 2388-2404.
[44] Suyker A.E. 2001. Year-around observations of the net ecosystem exchange of carbon dioxide in a native tallgrass prairie. Global Change Biology , 7(3): 279-289.
[45] Thomey M.L., Collins S.L., Vargas R. et al. 2011. Effect of precipitation variability on net primary production and soil respiration in a Chihuahuan Desert grassland. Global Change Biology , 17(4): 1505-1515.
[46] Vargas R., Collins S.L., Thomey M.L. et al. 2012. Precipitation variability and fire influence the temporal dynamics of soil CO 2 efflux in an arid grassland. Global Change Biology , 18(4): 1401-1411.
[47] Wayne Polley H., Mielnick P. C., Dugas W. A. et al. 2006. Increasing CO 2 from subambient to elevated concentrations increases grassland respiration per unit of net carbon fixation. Global Change Biology 12(8): 1390-1399.
[48] Wang L., Liu H.Z., Sun J.H. et al. 2016a. Water and carbon dioxide fluxes over an alpine meadow in southwest China and the impact of a spring drought event. International journal of biometeorology , 60(2): 195- 205.
[49] Wan S., Xia J. Liu W. et al. 2009. Photosynthetic overcompensation under nocturnal warming enhances grassland carbon sequestration. Ecology 90(10): 2700-2710.
[50] Wolf S., Eugster W., Potvin C. et al. 2011. Strong seasonal variations in net ecosystem CO 2 exchange of a tropical pasture and afforestation in Panama. Agricultural & Forest Meteorology 151(8): 1139-1151.
[51] Wang S.Y., Zhang Y., Lu S.H. et al. 2016b. Biophysical regulation of carbon fluxes over an alpine meadow ecosystem in the eastern Tibetan Plateau. International journal of biometeorology , 60(6): 801-812.
[52] Wang Y. F., Cui X. Y., Hao Y. B. et al. 2011. The fluxes of CO 2 from grazed and fenced temperate steppe during two drought years on the Inner Mongolia Plateau, China. Sci Total Environ 410-411(complete): 182-190.
[53] Ward H.C., Evans J.G., Grimmond C.S.B. 2012. Multi-season eddy covariance observations of energy, water and carbon fluxes over a suburban area in Swindon, UK. Atmospheric Chemistry & Physics , 12(11): 29147-29201.
[54] Xu L., Baldocchi D.D. 2004. Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California. Agricultural and Forest Meteorology , 123(1-2): 79-96.
[55] Xu L., Baldocchi D.D., Tang J. 2004. How soil moisture, rain pulses, and growth alter the response of ecosystem respiration to temperature. Global Biogeochemical Cycles , 18(4): 187-206.
[56] Yang F., Zhou G., Hunt J.E. et al. 2011. Biophysical regulation of net ecosystem carbon dioxide exchange over a temperate desert steppe in Inner Mongolia, China. Agriculture, Ecosystems & Environment , 142(3-4): 318- 328.
[57] You Q., Fraedrich K., Ren G. et al. 2013. Variability of temperature in the Tibetan Plateau based on homogenized surface stations and reanalysis data. International Journal of Climatology , 33(6): 1337-1347.
[58] Zhao L., Li J., Xu S. et al. 2010. Seasonal variations in carbon dioxide exchange in an alpine wetland meadow on the Qinghai-Tibetan Plateau. Biogeosciences , 7(4): 1207-1221.
[59] Zhao L., Li Y., Xu S. et al. 2006. Diurnal, seasonal and annual variation in net ecosystem CO2exchange of an alpine shrubland on Qinghai-Tibetan plateau. Global Change Biology , 12(10); 1940-1953.
[60] Zheng D., Zhang Q., Wu S. 2000. Mountain Geoecology and Sustainable Development of the Tibetan Plateau. Geojournal Library , 57.