slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Grant, R.F. 1 , Baldocchi, D.D. 2 and Ma, S. 2 PowerPoint Presentation
Download Presentation
Grant, R.F. 1 , Baldocchi, D.D. 2 and Ma, S. 2

Loading in 2 Seconds...

play fullscreen
1 / 16

Grant, R.F. 1 , Baldocchi, D.D. 2 and Ma, S. 2 - PowerPoint PPT Presentation


  • 62 Views
  • Uploaded on

Ecological Controls on Net Ecosystem Productivity of a Seasonally Dry Annual Grassland under Current and Future Climates: Modelling with Ecosys. Grant, R.F. 1 , Baldocchi, D.D. 2 and Ma, S. 2 1 Department of Renewable Resources, University of Alberta, Edmonton, AB, Canada T6G 2E3

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Grant, R.F. 1 , Baldocchi, D.D. 2 and Ma, S. 2' - kenaz


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Ecological Controls on Net Ecosystem Productivity of a Seasonally Dry Annual Grassland under Current and Future Climates: Modelling with Ecosys

Grant, R.F.1, Baldocchi, D.D.2and Ma, S.2

1 Department of Renewable Resources, University of Alberta,

Edmonton, AB, Canada T6G 2E3

2 Department of Environmental Science, Policy and Management & Berkeley

Atmospheric Science Center, University of California, Berkeley, CA

ecological controls on nep of annual grasslands in mediterranean climate zones
Ecological controls on NEP of annual grasslands in Mediterranean climate zones
  • Net C uptake
    • determined by the duration and intensity of precipitation in the rainy season during which soils are wet enough to sustain net C uptake by plants.
  • Net C emission
    • slow during the dry season when grasslands have senesced
    • rapid, rainfall-induced pulses at the start of the next rainy season before grasslands regrow,
    • rapid at the end of the rainy season if grassland growth terminates before the start of the following dry season.
how can we model these controls
How can we model these controls?
  • (1) Climatic and phenological signals that induce germination during soil wetting at the start of the rainy season, and senescence during soil drying at the end of the rainy season
  • (2) Soil-root-canopy-atmosphere hydraulic scheme by which soil and atmospheric water status determine plant water status, and hence GPP during soil wetting and drying between germination and senescence
  • (3) Stimulation or suppression of Rh during wetting or drying of surface residues and soil evident in precipitation-driven pulses that characterize C emissions in seasonally dry ecosystems
1 climatic and phenological signals
(1) Climatic and phenological signals
  • requirements for time accumulated at yc above or below set thresholds to be met during earlier and later plant growth stages respectively
    • 480 h above -0.2 MPa for germination, and 240 h below -2.0 MPa for senescence.
    • avoid premature germination or senescence and hence wastage of resources during false starts or ends to the rainy season
slide5

(2) Soil-root-canopy-atmosphere hydraulic scheme:

derive yc at which

root water uptake

+ capacitance

= transpiration

Rn

LE

H

atm. vapor density

atmosphere

stomatalsunlit,1

boundary

stomatalshaded,1

canopy layer 1

canopy vapor density

stomatalsunlit,n

canopy layer n

c

stomatalshaded,n

axial1

axial2

capacitance

s,1

axial3

r,1

soil1

radial1

s,2

radial2

r,2

soil2

s,n

r,n

radialn

soiln

CO2 fixation,

turgor, Ca - Ci

residue layer

soil hydraulic

resistance, root

length density

root surface

area

root axis length

soil layer 1

soil layer 2

soil layer n

3 stimulation or suppression of r h during wetting or drying
(3) Stimulation or suppression of Rh during wetting or drying
  • Scheme water and vapor transfer through soil surface and surface residue to solve for qr and yr.
  • Specific microbial respiration in soil and residue constrained by aqueous concentration [M/q] and y.
slide7

Vaira Ranch (38.418N, 120.958W)

MAT 16.3 oC

Precipitation 559 mm

slide8

Intercepts (a), slopes (b), correlations (R2), root mean square of differences between modelled and measured fluxes (RMSD), root mean square of error in measured fluxes (RMSE)

large interannual variation in nep caused by precipitation

Rainy seasons

shorter, less intense vs. longer more intense

Soil drying

earlier vs. later

Net C emission at start of rainy season

End of net C uptake

sooner vs. later

Large interannual variation in NEP caused by precipitation
slide12
Wetting of dry surface soil and residue at the start of the rainy season drives rapid pulses of CO2 emission
slide15

increased productivity with rising Ta, Ca, but …

earlier maturity in longer growing seasons

leaves wetter, respiring soil during dry season

slide16

pattern of IAV changes after 35 to 70 years, avg. NEP declines

NEP mean and IAV are stable under current climate

SOC stops rising, declines gradually after IAV changes