全球碳循環(huán)_Effect of Global Change on Terrestrial Carbon Cycle _lecture6（英文）

1、Lecture 6: Effect of Global Change on Terrestrial Carbon Cycle1. Global climate change (temperature, precipitation, CO2)2. Interaction of climate change, terrestrial ecosystems and carbon cycle3. Effects of climate change 4. Effects of increasing atmospheric CO25. Effects of fire disturbance6. Effec

2、ts of changes in land use and land managementIPCC Third Assessment Report (TAR) WMO, (2001)“Global warming continues”(Hansen et al., 2002; Science, 295, 275)Climate ChangeDisturbancesEcosystem StructureEcosystem FunctionCarbon and Ecosystem SustainabilityEcosystem Service to HumansSpeciesComposition

3、VegetationTypeCycling of C, N, P, S and waterInterrelations of Climate Change & Terrestrial Ecosystems 3. Effects of Climate Change (IPCC 2001) Global warming may increase NPP in temperate and artic ecosystems, but, it may decrease NPP in water-stressed ecosystems as it increases water loss Soil and

4、 roots respiration have generally been shown to increase with warming in the short term Changes in rainfall pattern affect plant water availability and length of growing season, particularly in arid and semi-arid regions Changing climate can also affect the distribution of plants and the incidence o

5、f disturbance such as fire, wind, and insect attacks, leading to changes in NBP High latitude ecosystems (tundra and taiga) contain about 25% of global soil carbon pool and are sensitive to changes in temperature and water table depth Large areas of the tropics are arid and semi-arid , and plant pro

6、duction is limited by water availability (e.g., hot, dry conditions of typical El Nio years)4. Effects of Increasing Atmospheric CO2 Increasing CO2 concentration in atmosphere has two effects on the carbon-fixingenzyme (Rubisco) reactions: increasing the rate of carboxylation and decreasing the rate

7、 of oxygenation Increased CO2 concentration allows the partial closure of stomata (a decrease in stomatalconductance), restricting water loss during transpiration that result in an increase in plantswater use efficiency The responses of C3 and C4 plants to increasing the CO2 concentration in atmosph

8、ere are different: - C3 plants show an increased rate of photosynthesis- C4 plants show no direct photosynthetic response or less response than C3 plants The direct effects of CO2 fertilization (under a doubling CO2):- C3 crops show an average increase in NPP of around 33% - Grassland and crops stud

9、ies combined show an average biomass increase of 14%- Field studies on young trees have shown a stimulation of photosynthesis of about 60% Reference: Saxe et al. (1998). Tree and forest functioning in an enriched CO2 atmosphere. New Phytologist, 139: 395-436.5. Effects of Fire DisturbanceFire affect

10、s carbon cycle in terrestrial ecosystems in six ways:Fire directly release carbon into the atmosphere through the combustion of biomass (2) Fire converts plant material into charcoal, which is an inert form of carbon and does not break down via decomposition.(3) The effects of fire significantly alt

11、er the thermal regimes of the organic and mineral soil layers, which, in turn, alters the ratesof decomposition within these layers (4) Through the reduction of plant biomass to ash, the melting of thepermafrost layer, and increased decomposition, fire increase the amountof soil nutrient available f

12、or plant growth (resulting in an increase of NPP)(5) The direct and indirect effects of burning strongly influence the patternssecondary succession on fire-disturbed landscape, which, in turn, control the patterns of live biomass/carbon storage.The frequency of fire in a given region will directly i

13、nfluence the stand age distribution of forests, which, in turn, affects the total amountof carbon storage in those forests6. Effects of Changes in Land Use and Land ManagementReading assignment:IPCC 2001 (# Pages 193-194)(http:/www.grida.no/climate/ipcc_tar/wgl/095.htm)Reference: Kasischke et al. (1

14、995). Fire, global warming, and the carbon balance of boreal forests. Ecological Application, 5: 437- 451. Three Main Approaches to Investigating Effect of Climate Change on Ecosystems Long-term observation Experimental manipulation Model simulation(J.M. Melillo, 1999, Science, 283: 183)Changhui Pen

15、gModeling the Effects of Climate Change and Fire Disturbanceon Productivity and Carbon Dynamics in Canadian Boreal ForestsOne Case Study in Central CanadaStudy areaThe Boreal Forests Transect Case Study (BFTCS)MethodsCENTURY 4.0 (Parton et al. 1987; Metherell et al. 1993)DataClimateSite-specific tre

16、esSoilResultsPeng et al. 1998; Peng and Apps, 1998, Global Biogeochem. CyclesPeng and Apps, (1999), Ecol. Modell. Price et al. (1999), J of Biogeography VEGETATION DISTRIBUTION (BFTCS)What is the CENTURY ?CENTURY, as developed by Parton et al. (1987, 1993), is a process-based ecosystem model of plan

17、t-soil, which simulates the long-term biogeochemical cycles of C, N, P, and S for various ecosystems, including grassland, agricultural land, savannas and forests. Website: http:/projects/century/nrel.htmCENTURY 4.0 Submodelsforest productionsoil organic matter/decompositionwater budgetgrassland/cro

18、pmanagement and events scheduling functionsTime step: monthlyCarbon pools (boxes) and fluxes (arrows) in CENTURY 4.0ATMOSPHERELeafFine Branches Large WoodCoarse RootFine Root VEGETATIONSurface LitterMetab.Struc.Dead Large WoodDead Fine BranchesDead Coarse RootSurfaceMicrobeActiveSOMSlow SOMPassiveSO

19、MLITTERSOILNPPASSIMILATIONLeached CPlantRespirationMicrobialRespirationSoil RespirationCO2 CO2 CO2CO2CO2Root LitterMetab.Struc.(Peng et al. 1998)CENTURY 4.0 Input Variablesmonthly mean, max, and min air temperaturemonthly total precipitationsoil texture: clay (%), silt (%), sand (%), and bulk densit

20、y atmospheric and soil nitrogen inputsforest typesSimulation Strategy(1) Model validation simulated above-ground biomass vs. observed data simulated soil carbon vs. observed data (0-20 cm) (2) Effects of climate change (CC)alteration to monthly mean temperature and precipitation based on 2xCO2 scena

21、rio with the GISS GCM Effects of CO2 fertilization (CO2)20% decrease in total PET and a 20% increase in nutrient use efficiency (NUE) associated with 2x CO2 Effects of CC and CO2 combined(3) Effects of fire disturbances - changes in fire disturbance intervalValidation of CENTURY 4.0(Peng et al. 1998

22、)Validation of CENTURY 4.00 2 4 6 8 10 12 Soil carbon (0-20 cm) (kg/m2) TH1TH2TH3FF2PA2FF1FF3FF4PA1 30-50 60-80ObservationSimulationNORTHSOUTH(Siltanen et al. 1997)( Correlation: R2 = 0.92 )Relative Effects on NPPAs projected by CENTURY 4.0 for GISS 2xCO2 scenario-10 0 10 20 30 40 50 60 % changeTH1T

23、H2TH3FF1FF2FF3FF4PA1PA2CCCO2CC+CO2Net primary productivity (gm-2yr-1)NORTHSOUTH( Peng and Apps 1998 )Relative Effects on Soil Decomposition0 10 20 30 40 50 60 % changeTH1TH2TH3FF1FF2FF3FF4PA1PA2CCCO2CC+CO2Decomposition (gm-2yr-1)As projected by CENTURY 4.0 for GISS 2xCO2 scenarioNORTHSOUTH( Peng and

24、 Apps, 1998 )(a)(b)Relationships (a) and (b) are Simulated by CENTURY 4.0 Under “CC+CO2” Climate ChangeR2 = 0.89R2 = 0.98( Peng and Apps 1999 )Relative Effects on Biomass Carbon Storage0 10 20 30 40 50 % changeTH1TH2TH3FF1FF2FF3FF4PA1PA2CCCO2CC+CO2Total Biomass (gm-2)As projected by CENTURY 4.0 for

25、GISS 2xCO2 scenarioNORTHSOUTH( Peng and Apps 1998 )Relative Effects on Carbon Storage-20 -15 -10 -5 0 5 10 15 % changeTH1TH2TH3FF1FF2FF3FF4PA1PA2CCCO2CC+CO2Soil organic matter (gm-2)As projected by CENTURY 4.0 for GISS 2xCO2 ScenarioNORTHSOUTH( Peng and Apps 1998 )( Peng and Apps 1999 )Effects of Fire Intervals on NPPBiomass Dynamics Under Fire Disturbance( Jiang , Peng, and Apps 1999 )Soil Carbon Dynamics Under Fire Disturbance ( Jiang, Peng and Apps 1999 )SummaryClimate change would result in changes not only in forest species composition but also in