Duke University

Some mechanisms of soil-plant-atmosphere interaction

!Marco Marani (Univ. di Padova & Duke Univ.)

Gabriele Manoli (U. di Padova & Duke U.) Sara Bonetti (Duke U.)

Valeria Volpe (U. di Padova) Gabriel Katul (Duke U.)

John Albertson (Duke U.) Jean Cristophe Domec (Duke U.& U. de Bordeaux)

Mario Putti (U. di Padova)

Interdisciplinary  Workshop  on  Frontiers  in  Hydrology  and  Hydrogeoscience  

8-­9  May  2014,  Venice  International  University,  Venice,  Italy

Soil-plant-atmosphere interactions are important

Pe

Pi

PET

Atmospheric Input

Atmospheric Output

Incoming Runoff

Outgoing Runoff

Study Region

Global water cycle Regional water recycling

Terrestrial Carbon cycle

Crop responses to…

Vegetated soil Bare soil

Soil moisture dynamics in vegetated and bare soils

Volp

e et

al.,

201

3

Transpiration and Photosynthesis, an often-neglected coupling

Transpiration and Photosynthesis An often-neglected coupling

Importance of root distribution (li) in determining overall resistance to flow.

( ) ( )[ ] xRRLLxLR AzzψgT ⋅+−+⋅−= ψψψ ),(

( ) ( )[ ] riiRRiLRi Azzgq ⋅+−+⋅−= ψψψψ ),(

cwLsLw ALAIVPDgaf ⋅⋅⋅⋅⋅= εψψ )()(

Soil-Plant-Atmosphere continuum model

Leaf-Atmosphere

Xylem-Leaf

Root-Xylem ΨR

ΨL

CO2

gx

gsgs

T

0=∂

∂−

∂

∂

s

w

s

c

gf

gf

λ

(Katul et al., 2010)

( )Lsg ψ

( )[ ] ( )Lrsw

ws qzKKtS

tSS ψψψϕ

ψ ,++∇⋅∇=∂

∂+

∂

∂

Variably saturated flow (Cathy):

H2O

(Volpe et al., 2011)

Volpe et al., 2013; Manoli et al., 2014(Paniconi and Putti, 1994)

Root vs. Darcy flows integrated within the root zone

Volpe et al., 2013

Manoli et al., 2014

Model and obs. in NC Coastal Forest

RWU RWU

Root Hydraulic Redistribution Root Hydraulic Redistribution

Darcy flow divergence Darcy flow divergence

Roo

t Hyd

raul

ic R

edis

trib

utio

n an

d sp

atia

l int

erac

tions

Man

oli e

t al.,

201

4

Lumped Transpiration-Soil Saturation Relations

Pure drainage

Infiltration & drainage

Manoli et al., 2014

Clouds

Transpiration

z

ABL

LCL

Free Atmosphere

sunrise mid-morning

Soil

Plan

tA

tmos

pher

e

mid-afternoon

Clouds

z

ρ [Ωm]

200

40

120

ABL

LCL

Free Atmosphere

sunrise mid-morning

Soil

Plan

tA

tmos

pher

e

mid-afternoon

Transpiration

Convective Rainfall Initiation

Bonetti et al., 2014

Convective Rainfall Initiation

),( RHTzz aLCLLCL =

ABLT

sABL

zH

dtdz

⋅

+⋅=

γ

β )1(

( ) ( )( )STGfLETRc

H wSnap

s −−−⋅

=ρ

1

( )VPDgg Lss ,ψ=

( ) ( )100RHTeTeVPD asss ⋅−=

( )dtdz

TTHdtdT

z ABLaFAs

aABL ⋅−+=

( )dtdzwwLE

dtdwz ABL

FAa

ABL ⋅−+=λρ

z

Conservation Eqs. (well mixed ABL ): ABL potential temperature, Ta

Specific humidity, w

( )[ ] ( )Lrsw

ws qzKKtS

tSS ψψψϕ

ψ ,++∇⋅∇=∂

∂+

∂

∂

Bonetti et al., 2014

Modeled ABL-LCL intersection and observed rainfall

Soil-Plant-ABL model

Atmospheric feedback

When atmospheric feedback

Is turned off

RAIN

NO RAIN

Moi

stur

e fro

m F

ree

Atm

osph

ere

Conclusions

Importance of water vertical redistribution in increasing water availability to plants. Relative role of root vs. Darcy water redistribution; overlapping root systems enhance water stress but do not alter averaged Transpiration vs. mean soil moisture relations; the role of vegetation controls and WT fluctuations on the predisposition of convective rainfall Coupled carbon and water uptake modeling contribute to understanding collective responses of carbon and water cycles.

ρ [Ωm]

200

40

120

Challenges and Opportunities

Getting the right results for the right reason requires space-time characterizations of active root biomass: ERT and SPA modeling to play an important role. Root biomass allocation strategies: SPA modeling and Space-time active root mapping to yield insight into biomass allocation strategies. Climate change responses of the SPA system: subgrid parameterization?