Grazing effects on the greenhouse gas balance of a temperate steppe ecosystem
Tóm tắt
Although a significant fraction of the global soil–atmosphere exchange of greenhouse gases (GHGs) occurs in semi-arid zones little is known about the magnitude of fluxes in grazed steppe ecosystems and the interference with grazing intensity. In order to assess GHG burdens and to identify options of climate-optimized livestock farming, GHG emissions of sheep grazing in Inner Mongolia steppe were analyzed. Carbon sequestration and field-fluxes of methane (CH4) and nitrous oxide (N2O) were measured at a range of steppe sites differing in grazing intensity and management, i.e. ungrazed (UG), ungrazed with hay cutting (HC), lightly grazed (LG), moderately grazed (MG), and heavily grazed (HG). In addition, GHG emissions from enteric fermentation, manure management, and farming inputs (i.e. fossil fuels) were quantified for LG, MG, and HG. Monte Carlo simulation was used to estimate uncertainty. Sheep grazing changed the net GHG balance of the steppe from a significant sink at UG (−1476 ± 2481 kg CO2eq ha−1 year−1) to a significant source at MG (2350 ± 1723 kg CO2eq ha−1 year−1) and HG (3115 ± 2327 kg CO2eq ha−1 year−1). In a similar way, the GHG intensity increased from 8.6 ± 79.2 kg CO2eq kg−1 liveweight gain at LG up to 62.2 ± 45.8 and 62.6 ± 46.7 kg CO2eq kg−1 liveweight gain at MG and HG, respectively. GHG balances were predominantly determined by CO2 from changes in topsoil organic carbon. In grazing systems, CH4 from enteric fermentation was the second most important component. The results suggest that sheep grazing under the current management changes this steppe ecosystem from a sink to a source of GHGs and that grazing exclusion holds large potential to restore soil organic carbon stocks and thus to sequester atmospheric CO2. The balance between grazing intensity and grazing exclusion predominantly determines GHG balances of grass-based sheep farming in this region. Therefore, a high proportion of ungrazed land is most important for reducing GHG balances of sheep farms. This can be either achieved by high grazing intensity on the remaining grazed land or by confined hay feeding of sheep.
Tài liệu tham khảo
Ammann C, Spirig C, Leifeld J, Neftel A (2009) Assessment of the nitrogen and carbon budget of two managed temperate grassland fields. Agric Ecosyst Environ 133(3–4):150–162
Audsley E, Brander M, Chatterton J, Murphy-Bokern D, Webster C, Williams A (2009) How low can we go? An assessment of greenhouse gas emissions from the UK food system and the scope to reduce them by 2050. FCRN-WWF-UK. http://assets.wwf.org.uk/downloads/how_low_report_1.pdf. Accessed on 03.01.11
Bannink A, Kogut J, Dijkstra J, France J, Kebreab E, Van Vuuren AM, Tamminga S (2006) Estimation of the stoichiometry of volatile fatty acid production in the rumen of lactating cows. J Theor Biol 238(1):36–51
Biswas WK, Graham J, Kelly K, John MB (2010) Global warming contributions from wheat, sheep meat and wool production in Victoria, Australia—a life cycle assessment. J Clean Prod 18(14):1386–1392
Chen W, Wolf B, Yao Z, Brüggemann N, Butterbach-Bahl K, Liu C, Han S, Han X, Zheng X (2010) Annual methane uptake by typical semiarid steppe in Inner Mongolia. J Geophys Res 115(D15):D15108
Chen W, Wolf B, Brüggemann N, Butterbach-Bahl K, Zheng X (2011a) Annual emissions of greenhouse gases from sheepfolds in Inner Mongolia. Plant Soil 340(1):291–301
Chen WW, Wolf B, Zheng XH, Yao ZS, Butterbach-Bahl K, Bruggemann N, Liu CY, Han SH, Han XG (2011b) Annual methane uptake by temperate semiarid steppes as regulated by stocking rates, aboveground plant biomass and topsoil air permeability. Global Change Biol 17(9):2803–2816
Conant RT, Paustian K, Elliott ET (2001) Grassland management and conversion into grassland: effects on soil carbon. Ecol Appl 11(2):343–355
Dong YS, Zhang S, Qi YC, Chen ZZ, Geng YB (2000) Fluxes of CO2, N2O and CH4 from a typical temperate grassland in Inner Mongolia and its daily variation. Chin Sci Bull 45(17):1590–1594
Forster P, Ramaswamy V, Artaxo P, Berntsen T, Betts R, Fahey DW, Haywood J, Lean J, Lowe DD, Myhre GJ, Nganga JR, Prinn RG, Raga GM, Schulz M, Van Dorland R (2007) Changes in atmospheric constituents and in radiative forcing. Climate change 2007: the physical science basis. Contribution of working group I to the fourth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
Galbally IE, Kirstine WV, Meyer CP, Wang YP (2008) Soil-atmosphere trace gas exchange in semiarid and arid zones. J Environ Qual 37(2):599–607
Gill M, Smith P, Wilkinson JM (2010) Mitigating climate change: the role of domestic livestock. Animal 4(3):323–333
Glindemann T, Wang C, Tas BM, Schiborra A, Gierus M, Taube F, Susenbeth A (2009) Impact of grazing intensity on herbage intake, composition, and digestibility and on live weight gain of sheep on the Inner Mongolian steppe. Livest Sci 124(1–3):142–147
Hoffmann C, Funk R, Li Y, Sommer M (2008) Effect of grazing on wind driven carbon and nitrogen ratios in the grasslands of Inner Mongolia. Catena 75(2):182–190
Holst J, Liu C, Yao Z, Bruggemann N, Zheng X, Han X, Butterbach-Bahl K (2007) Importance of point sources on regional nitrous oxide fluxes in semi-arid steppe of Inner Mongolia, China. Plant Soil 296(1–2):209–226
IPCC (2006) In: Eggleston HS, Buendia L, Miwa K, Ngara T, Tanabe K (eds) IPCC guidelines for national greenhouse gas inventories, prepared by the National Greenhouse Gas Inventories Programme. IGES, Japan
ISO (2006) Environmental management—life cycle assessment—principles and framework. EN ISO 14040:2006. International Organisation for Standardization, Geneva, Switzerland
IUSS Working Group WRB (2006) World reference base for soil resources 2006, World soil resources reports No 103. Rome, FAO
Jones SK, Rees RM, Skiba UM, Ball BC (2005) Greenhouse gas emissions from a managed grassland. Global Planet Change 47(2–4):201–211
Kebreab E, Clark K, Wagner-Riddle C, France J (2006) Methane and nitrous oxide emissions from Canadian animal agriculture: a review. Can J Anim Sci 86(2):135–158
Lal R (2004) Soil carbon sequestration impacts on global climate change and food security. Science 304(5677):1623–1627
Liebig MA, Gross JR, Kronberg SL, Phillips RL, Hanson JD (2010) Grazing management contributions to net global warming potential: a long-term evaluation in the Northern Great Plains. J Environ Qual 39(3):799–809
Liu CY, Holst J, Yao ZS, Bruggemann N, Butterbach-Bahl K, Han SH, Han XG, Tas B, Susenbeth A, Zheng XH (2009) Growing season methane budget of an Inner Mongolian steppe. Atmos Environ 43(19):3086–3095
Liu XR, Dong YS, Qi YC, Li SG (2010) N2O fluxes from the native and grazed semi-arid steppes and their driving factors in Inner Mongolia, China. Nutr Cycl Agroecosyst 86(2):231–240
Mosier AR, Halvorson AD, Reule CA, Liu XJJ (2006) Net global warming potential and greenhouse gas intensity in irrigated cropping systems in northeastern Colorado. J Environ Qual 35(4):1584–1598
Nemry F, Theunis J, Brechet T, Lopez P (2001) Greenhouse gas emissions reduction and material flows. Final report. IDD—Institut Wallon—VITO. Brussel
NRC (2007) Nutrient requirements of small ruminants. National Research Council. The National Academy Press, Washington, DC, USA
Peters GM, Rowley HV, Wiedemann S, Tucker R, Short MD, Schulz M (2010) Red meat production in Australia: life cycle assessment and comparison with overseas studies. Environ Sci Technol 44(4):1327–1332
Pineiro G, Paruelo JM, Oesterheld M, Jobbagy EG (2010) Pathways of grazing effects on soil organic carbon and nitrogen. Rangel Ecol Manage 63(1):109–119
Ren JZ, Hu ZZ, Zhao J, Zhang DG, Hou FJ, Lin HL, Mu XD (2008) A grassland classification system and its application in China. Rangel J 30(2):199–209
Robertson GP, Paul EA, Harwood RR (2000) Greenhouse gases in intensive agriculture: contributions of individual gases to the radiative forcing of the atmosphere. Science 289(5486):1922–1925
Schils RLM, Verhagen A, Aarts HFM, Sebek LBJ (2005) A farm level approach to define successful mitigation strategies for GHG emissions from ruminant livestock systems. Nutr Cycl Agroecosyst 71(2):163–175
Schönbach P, Wan H, Schiborra A, Gierus M, Bai Y, Müller K, Glindemann T, Wang C, Susenbeth A, Taube F (2009) Short-term management and stocking rate effects of grazing sheep on herbage quality and productivity of Inner Mongolia steppe. Crop Pasture Sci 60:963–974
Schönbach P, Wan H, Gierus M, Bai Y, Müller K, Lin L, Susenbeth A, Taube F (2011) Grassland responses to grazing: effects of grazing intensity and management system in an Inner Mongolian steppe ecosystem. Plant Soil 340(1):103–115
Schönbach P, Wan H, Gierus M, Loges R, Müller K, Lin L, Susenbeth A, Taube F (2012) Effects of grazing sheep and precipitation on herbage production, herbage nutritive value and animal performance in continental steppe. Grass Forage Sci. doi:10.1111/j.1365-2494.2012.00874.x
Six J, Conant RT, Paul EA, Paustian K (2002) Stabilization mechanisms of soil organic matter: implications for C-saturation of soils. Plant Soil 241(2):155–176
Smith P, Martino D, Cai Z, Gwary D, Janzen H, Kumar P, McCarl B, Ogle S, O’Mara F, Rice C, Scholes B, Sirotenko O, Howden M, McAllister T, Pan G, Romanenkov V, Schneider U, Towprayoon S, Wattenbach M, Smith J (2008) Greenhouse gas mitigation in agriculture. Philos Trans R Soc B Biol Sci 363(1492):789–813
Soussana JF, Allard V, Pilegaard K, Ambus P, Amman C, Campbell C, Ceschia E, Clifton-Brown J, Czobel S, Domingues R, Flechard C, Fuhrer J, Hensen A, Horvath L, Jones M, Kasper G, Martin C, Nagy Z, Neftel A, Raschi A, Baronti S, Rees RM, Skiba U, Stefani P, Manca G, Sutton M, Tubaf Z, Valentini R (2007) Full accounting of the greenhouse gas (CO2, N2O, CH4) budget of nine European grassland sites. Agric Ecosyst Environ 121(1–2):121–134
Steffens M, Kolbl A, Kogel-Knabner I (2009) Alteration of soil organic matter pools and aggregation in semi-arid steppe topsoils as driven by organic matter input. Eur J Soil Sci 60(2):198–212
Steffens M, Kolbl A, Schork E, Gschrey B, Kogel-Knabner I (2011) Distribution of soil organic matter between fractions and aggregate size classes in grazed semiarid steppe soil profiles. Plant Soil 338(1–2):63–81
Williams AG, Audsley E, Sandars DL (2006) Determining the environmental burdens and resource use in the production of agricultural and horticultural commodities. Main report. Defra research project IS0205. Cranfield University and Defra, Bedford
Wolf B, Zheng XH, Brueggemann N, Chen WW, Dannenmann M, Han XG, Sutton MA, Wu HH, Yao ZS, Butterbach-Bahl K (2010) Grazing-induced reduction of natural nitrous oxide release from continental steppe. Nature 464(7290):881–884