Environmental limits of the biological carbon pumping in the forests

Transcription

1 Environmental limits of the biological carbon pumping in the forests effect of the solar radiation type dimming effect Centre for Global Change Impact Studie Michal V. Marek, Otmar Urban, Dalibor Janouš czechglobe.cz

2 Forest trees and the light Effects of solar radation energy Photo-energetic effect photosynthesis, transpiration Photo-cybernetic effect induction vegetative/generative phase changes Photo-destructive effect - inhibiton of photosynthesis, chlorophyll bleachning Incident solar radation Global solar radiation whole radiation Beam solar radiation direct solar beams Diffusive solar radiation multidirectional illumination

3 Dimming effect Observed reduction of the solar radiation intenzity up to.51 ±.5 W m -2 per year, i.e. 2.7 % per decenium The causes of the global dimming increase of the antropogenic pollutans increase of the water vapour atmospheric vulcanic activity enhanced diffusive solar radiation

4 Diffusive solar radiation enhances NPP El Chichón Pinatubo net primary production (NPP) is enhanced in realtion to the diffusive conditions Diffusive radiation was responsible for the increased carbon sink in the years period up to 25% Merkado L.M. et al.: Nature 458: , 29.

5 PPFD, μmol m -2 s -1 Example of daily course of PAR under BEAM and DIFUSSIVE conditons Cloudy Sunny : 6: 12: 18: : Time, h

6 Diffusive solar radiation enhanced GPP and NPP Urban O. et al.: GCB 46: , 27. Merkado L.M. et al.: Nature 458: , 29.

7 Comparison of the beam versus diffusive diffusive days effects on carbon uptake at spruce shoot and stand level 3 25 NEE (μmol m -2 s -1 ) A Cloudy Sunny AM Sunny PM -5 Fit -1 stand PPFD (μmol m -2 s -1 ) AN, μmol m -2 s An_cloudy An_sunny Fit_cloudy Fit_sunny -2 shoot A PAR, μmol m -2 s -1

8 Possible causses of the positive effect of diffusive radiation on the carbon pumping in the forest stand Solar radation energy penetration into lef interior Temperature effects Effects of VPD Solar radation spectrum within a crown space Solar radation penetration into crown space Inclusion of lower crown parts into canopy photosyntesis

9 Solar radation energy penetration into lef interior palisade mesophyll spongy mesophyll Cylindric palisade cells form effective space for beam radiation penetration Spongy mesophyll cell are effectivelly illuminated by heterogenous diffusive radiation

10 Temperature effects Tair, C Cloudy Sunny,25,5,75 1 Time, h Typical daily courses of air temperature in sunny and cloudy days Respiration components of ecosystems are exponentially related to air temperature - Cloudy days - frequently lower air temperature!!!! Soil CO2 efflux, umolco 2 m -2.s y = 1,251e,937x R 2 =, Soil temperature, o C Stem CO 2 efflux, μmolco 2 m -2 s y =,274e,1167x R 2 =, Cambium temperature, C Leaf respiration, μmolco2 m -2 s -1 2,5 2, 1,5 1,,5, y =,1132e,919x R 2 =, Leaf temperature, C The exponential relationships between the rate of CO 2 efflux from soil (A), stems (B) and leaves (C) and actual temperature.

11 Effects of VPD VPD, kpa Sunny Cloudy : 6: 12: 18: : Time, h Typical daily courses of vapour pressure deficit (VPD) over the days with prevailing beam of diffusive radiation High value of VPD is related to closed stomatal pore - reduction of assimilation Cloudy days frequently lower values of VPD!!!! GS, mmol(h2o) m -2 s Gs_cloudy Gs_sunny GsFit-lin GsFit-Keen BThe relationship between stomatal PAR, conductivity μmol m -2 s -1 (G S ) and intensity of incident PAR

12 Solar radation spectrum within a crown space Relative photon distribution, r.u. 4.5E-3 3.5E-3 2.5E-3 1.5E-3 Cloudy Sunny Strong differences in BLUE and RED spectrum area λ, nm Relative photon distribution over the days with prevailing direct ( ) and diffuse ( ) radiation G S (mol m -2 s -1 ) Cloudy Sunny Fit Blue part of solar spectra enhanced stomata openning and is more effective absorbed Cloudy days induction of assimilation imilation!!!! C PPFD Blue (μmol m -2 s -1 ) Košvancová-Zitová et al.: Photosynthetica 47: , 29

13 Solar radation penetration into crown space FARtrans (%) A Ln(FARtrans) B Oblačno Jasno LA cumul (%) Oblačno Jasno y =.62x +.95 R 2 =.99 y =.8x -.23 R 2 = H (m) Diffusive radiation is responsible for the lower extinctions coefficent within crown space Cloudy days - diffusivefusive radiation penetrates deeper into crown body!!! Relationship between cumulative leaf area (LA cumul ) and transmitted photosynthetic photon flux density (PPFD trans ) estimated during sunny (empty circles) and cloudy (full circles) days (A). Slopes of linear relationship between logarithmic PPFD trans and canopy height H (B). SELA was calculated for incident PPFD 4 μmol m -2 s -1. Empty columns, sunny days; Filled columns, cloudy days.

14 Solar radation penetration into crown space,35 vertical bars indicate.95 confidence intervals,3 Gs, mol m-2 s-1,25,2,15,1,5, 4th whorl 7th whorl 9th whorl 12th whorl -,5 time: sunny time: cloudy Cloudy days stomata in the lower part of the crown body are more open!!!

15 Solar radation penetration into crown space Amount of CO2 assimilated (g) A % 42.5% 35.8% Cloudy 4th whorl 7th whorl 9th whorl 12th whorl 9.4% 78.1% 24.2% 2.1% -4.3% Sunny CLEAR days lower crown parts CO 2 assimilation contribution is MINIMAL CLOUDY days- lower crowns parts CO 2 assimilation contribution is INCREASING

16 Eddy-covari covariance technique IRGA a PC controla

17 Effect of the occurence of solar radiation diffusive days on the NEP of 5 the mountain spruce stand NEP [kg C ha-1] NEP [kg C ha-1] Majority of beam days Majority of diffusive days month

18 Inter-annual variation of NEP of a spruce forest Kg CO 2 ha -1 h -1

19 Deeper analysis of seasonal NEP courses in a mountain spruce forest NEP [kgc ha-1 day-1] Carbon deposition dormancy temp. decrease overcast overcast + rain sunny + warm overcast + warm NEP [kgc ha-1 day-1] NEP [kgc ha-1 day-1]

20 Environmental limits of the biological carbon pumping in the forests effect of the solar radiation type Higher carbon pumping under conditions of diffusive radiation is induced by: (1) more suitable microclimatological conditions Air temperture decrease is responsible for respiration decrease, Decrease of VPD is responsible for stomata oppening, (2) stimulation of assimilation processes and stomatal conductance because of changes of solar radiation spectral composition within the crown space (3) increased radiation penetrartion and thus more significant connection of lower crown parts into assimilatory activity. Carbon pump of forest stand is strongly affected by the solar diffusive radiation penetration (1) large part of leaf area is illuminated by the higher radiation exceeding light compensation point active CO 2 sink in large part of crown space (2) higher proportion of leaf area is an carbon sink for longer time

21 Environmental limits of the biological carbon pumping in the forests effect of the solar radiation type Others effects of diffusive radiation Water use efficiency is INCREASING stand photosynthesis is responding more significantly to difusive radiation in comparison to the transpiration Isoprene production increased diffusive radiation is connected to the lower volative compounds production, because of the lower global radiation illumination and thus the lower cooling of stand canopy surface Knohl A, Baldocchi DD (28) Effects of diffuse radiation on canopy gas exchange processes in a forest ecosystem. Journal of Geochemical Research, 113, G223.

22 Thank You