Carbon, Part 3, Net Ecosystem Production

Transcription

1 Carbon, Part 3, Net Ecosystem Production Carbon Balance of Ecosystems NEP,NPP, GPP Seasonal Dynamics of Ecosystem Carbon Fluxes Carbon Flux Partitioning Chain-saw and Shovel Ecology Dennis Baldocchi ESPM UC Berkeley 1

2 Carbon Cycle: Above and Below Ground Links Law and Ryan, Biogeochemistry, 2005 Active Carbon/Water Flux Measurement Sites 2

3 What is the Range of Gross Primary Productivity? 0.06 Published Data, April, pdf GPP (gc m -2 y -1 ) Upper Limits of GPP 2 PAR gc m GPPmax Rg LUE fpar R mole C g 7000 * MJ m - 2 y -1 * (4.6/2) * 0.02 * 0.9 * 12 = 3477 gc m -2 y -1 Rg: incoming short wave radiation PAR: photosynthetically active radiation, 0.4 to 0.7 micron LUE: light use efficiency fpar: fraction of absorbed PAR 3

4 Potential and Real Rates of Gross Carbon Uptake by Vegetation: Most Locations Never Reach Upper Potential GPP at 2% efficiency and 365 day Growing Season tropics GPP at 2% efficiency and day Growing Season FLUXNET 2007 Database How much Carbon do Ecosystems take up? Probability Distribution of Published NEE Measurements, Integrated Annually Published Data, April, n = 973 mean = /- 253 gc m -2 y -1 pdf NEE (gc m -2 y -1 ) 4

5 Luyssaert et al. 2007, GCB NEP is the balance between two large fluxes GPP and ecosystem respiration Chapin et al. 5

6 Seasonal change in daily NEE for a temperate deciduous forest 100 Harvard Forest: NEE (kg ha -1 d -1 ) Day Data of Wofsy et al; Urbanski et al 2007 JGR GPP (kgc ha -1 d -1 ) Harvard Forest, Season Course in Daily GPP and Reco for a temperate deciduous forest day Reco (kgc ha -1 d -1 ) Data of Wofsy et al; Urbanski et al. JGR 2008 day 6

7 Seasonal Patterns Vary with Plant Functional Type 4 2 F N (gc m -2 d -1 ) Deciduous forest Evergreen forest Macchia Perennial grassland Annual grassland Crop (wheat) Tundra Day Net Ecosystem Carbon Exchange of Deciduous Forests Scales with Length of Growing Season 200 Temperate and Boreal Deciduous Forests Deciduous and Evergreen Savanna 0 F N (gc m -2 yr -1 ) Length of Growing Season, days Baldocchi, Austral J Botany,

8 Does Net Ecosystem Carbon Exchange Scale with Photosynthesis? F N (gc m -2 y -1 ) F A (gc m -2 y -1 ) Ecosystems with greatest GPP don t necessarily experience greatest NEE Baldocchi, Austral J Botany, 2008 Ecosystem Respiration Scales with Ecosystem Photosynthesis, But with an Offset by Disturbance Undisturbed Disturbed by Logging, Fire, Drainage, Mowing 3000 F R (gc m -2 y -1 ) F A (gc m -2 y -1 ) Baldocchi, Austral J Botany,

9 Interannual Variations in Photosynthesis and Respiration are Coupled Interannual Variability in F N d F R /dt (gc m -2 y -2 ) Coefficients: b[0] b[1] r ² n = d F A /dt (gc m -2 y -2 ) Baldocchi, Austral J Botany, 2008 GPP and Climate Drivers Climate explains 70% of variation in GPP Luyssaert et al. 2007, GCB 9

10 NPP and Climate Drivers Climate explains 35% of variation in NPP Luyssaert et al. 2007, GCB NEP and Climate Drivers Climate explains 5% of variation in NEP Luyssaert et al. 2007, GCB 10

11 Disentangling roles of Age, Climate and N deposition Magnani et al 2007 Nature Net Ecosystem C Exchange is a Function of Time Since Disturbance 1800 Harvard Forest 1600 Carbon Flux (gc m -2 y -1 ) F N F A F R Year Urbanski et al. 2007, JGR 11

12 Net Primary Production and Stand Age He et al GBC On to Ecosystem Respiration 12

13 The Ratio between Plant Respiration and Photosynthesis is Constant: Regardless of Plant Size, Treatment etc Gifford, 1994, Australian J Plant Physiol Emerging and Useful Ecological Rules Fundamentals of Soil Respiration Kyuzakov 13

14 Soil Respiration and Temperature Note how Variance increases with T, especially after Ps starts! deforest et al 2006 IntJ Biomet Soil Respiration, Temperature and Soil Moisture Xu and Qi, 2001, Global Change Biology 14

15 Soil Respiration and Soil Moisture Xu and Qi, 2001, Global Change Biology Roles of Drought and Temperature on Soil Respiration Reichstein et al. 2003, GBC 15

16 Environmental Controls on Respiration: Temperature, Soil Moisture, Growth/Reproduction, Rain-Induced Microbial Activity Fast growth period data R eco /R ref 1.0 Rain pulse Soil volumetric water content (m3 m -3 ) Xu + Baldocchi, 2003 AgForMet Respiration: Temperature and acclimation Respiration of a cold Boreal Ecosystem, at 10 C, Is similar to a warm Temperate Ecosystem at 20 C Enquist et al. 2003, Nature 16

17 Respiration and Temperature: A role for fast-photosynthesis 0.50 Tonzi Open areas 1.7 Tonzi Under trees :50h 1.6 Under trees DOY h 12:50h h 16h 0.25 Fo=0.037e T, Q 10 =1.69, R 2 = h h 1.2 6h 24h Fu=0.337e T, Q 10 =1.61, R 2 = Soil tempreture ( o C) Soil temperature ( o C) Tang, Baldocchi, Xu, 2005, GCB On Annual Scales Soil Respiration Scales with Photosynthesis Raich 2000 Tellus Janssens et al 2001 GCB 17

18 Rain Pulses: Heterotrophic Respiration 5 C Efflux (gc m -2 d -1 ) mm 12.7 mm 61 mm 12 mm 3 mm Days After Rain Pulse Xu, Baldocchi, Tang, 2004, GBC Photodegradation Austin et al 2010 PNAS 18

19 Concluding Points GPP scales with Available Sunlight so there are upper Limits to GPP, set by Length of Growing Season, Temperature and Water Most (80%) Assimilated Carbon is lost by Autotrophic and HeterTrophic Respiration Net Carbon Fluxes are a Function of Weather, Structure and Function And Time Since Disturbance Soil Respiration tied to Temperature and Moisture, and recent Photosynthesis Rain can Induce Pulses! Chain-Saw Carbon Balance, 101 C Gains Losses t Gains GPP Losses Re spiration LitterFall Herbivory RootTurnover VOC_ Emissions Fire Harvest) C ~ Wood Soil t annual C C 19

20 Carbon Allocation of Forests Litton et al., 2007 But Partitioning of Carbon is Poorly related to Biomass Litton et al.,

21 NPP Biometry NPP=GPP-Ra NPP=Live mass increment (L) + Detritus (D) + Herbivory (H) NEP = (L + D +H)-R hetero Soil Carbon Store=Detritus-R hetero dcarbon = Wood Increment + Soil Carbon Store NEP ~ dcarbon H=0 Caveat Emptor Few of the NPP components are measured, or measured well, in practice Litterfall Bole Increment Labile Carbon is not measured in wood increment ANPP Convert bole increment to gc Small diameter trees ignored, < 10 cm diameter Below ground components often ignored 21

22 Biometry and Eddy Covariance NEP converges on Long Time Scales Gough et al 2008 AgForMet NEP,ec=GPP-Reco NEP = (L + D +H)-Rhetero Curtis et al, 2002, AgForMet 22

23 Chapin et al 23