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(daily) net photosynthesis (PSN) and (annual) net primary production (NPP)

(daily) net photosynthesis (PSN) and (annual) net primary production (NPP). PSN and NPP. (daily) net photosynthesis (PSN) (annual) net primary production (NPP) relate to net carbon uptake important for understanding global carbon budget (climate change). PSN and NPP.

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(daily) net photosynthesis (PSN) and (annual) net primary production (NPP)

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  1. (daily) net photosynthesis (PSN)and(annual) net primary production (NPP)

  2. PSN and NPP • (daily) net photosynthesis (PSN) • (annual) net primary production (NPP) • relate to net carbon uptake • important for understanding global carbon budget (climate change)

  3. PSN and NPP • C02 removed from atmosphere • photosynthesis • C02 released by plant (and animal) • respiration • Net Photosynthesis (PSN) • net carbon exchange over 1 day: (photosynthesis - respiration)

  4. PSN and NPP • Net Primary Productivity (NPP) • annual net carbon exchange • quantifies actual plant growth • (not just C02 fixation)

  5. Algorithms - require to be model-based • simple Production efficiency model (PEM) • (Monteith, 1972; 1977) • relate PSN, NPP to APAR • APAR from PAR and fAPAR

  6. PSN = daily total photosynthesis • NPP, PSN typically accum. of dry matter (convert to C by assuming DM 48% C) • = efficiency of conversion of PAR to DM (g/MJ) • equations hold for non-stressed conditions

  7. to characterise vegetation need to know: • Efficiency • fAPAR so for fixed

  8. Determining • herbaceous vegetation (grasses): • av. 1.0-1.8 gC/MJ for C3 plants • higher for C4 • woody vegetation: • 0.2 - 1.5 gC/MJ • simple model for :

  9. References • Dubayah, R. (1992) Estimating net solar radiation using Landsat Thematic Mapper and Digital Elevation data. Water resources Res., 28: 2469-2484. • Monteith, J.L., (1972) Solar radiation and productivity in tropical ecosystems. J. Appl. Ecol, 9:747-766. • Monteith, J.L., (1977). Climate and efficiency of crop production in Britain. Phil. Trans. Royal Soc. London, B 281:277-294. • Running, S.W., Nemani, R., Glassy, J.M. (1996) MOD17 PSN/NPP Algorithm Theoretical Basis Document, NASA.

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