Marco Marani, from Padova University and Duke, presented a work on the soil-water-plants continuum. He emphasize the role of roots in modifying the soil water distribution, otherwise controlled by Darcy flows. However, he also studied and talked about the influence of the soil-plants-atmosphere continuum.

1. 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

2. Soil-plant-atmosphere interactions are important
Pe
Pi
P
ET
Atmospheric
Input
Atmospheric
Output
Incoming
Runoff
Outgoing
Runoff
Study Region
Global water cycle
Regional water recycling
Terrestrial
Carbon
cycle
Crop responses to…

3. Vegetated soil Bare soil
Soil moisture dynamics in vegetated and bare soils
Volpeetal.,2013

4. Transpiration and Photosynthesis,
an often-neglected coupling

5. Transpiration and Photosynthesis
An often-neglected coupling
Importance of root distribution
(li) in determining overall
resistance to flow.

6. ( ) ( )[ ] xRRLLxLR AzzψgT ⋅+−+⋅−= ψψψ ),(
( ) ( )[ ] riiRRiLRi Azzgq ⋅+−+⋅−= ψψψψ ),(
cwLsLw ALAIVPDgaf ⋅⋅⋅⋅⋅= εψψ )()(
Soil-Plant-Atmosphere continuum model
Leaf-Atmosphere
Xylem-Leaf
Root-Xylem ΨR
ΨL
CO2
gx
gs
gs
T
0=
∂
∂
−
∂
∂
s
w
s
c
g
f
g
f
λ
(Katul et al., 2010)
( )Lsg ψ
( )[ ] ( )Lrs
w
ws qzKK
t
S
t
SS ψψψϕ
ψ
,++∇⋅∇=
∂
∂
+
∂
∂
Variably saturated flow (Cathy):
H2O
(Volpe et al., 2011)
Volpe et al., 2013;
Manoli et al., 2014
(Paniconi and Putti, 1994)

7. Root vs. Darcy flows integrated within the root zone
Volpe et al., 2013

8. Manoli et al., 2014
Model and obs. in NC Coastal Forest

9. RWU RWU
Root Hydraulic Redistribution Root Hydraulic Redistribution
Darcy flow divergence Darcy flow divergence
RootHydraulicRedistributionandspatialinteractions
Manolietal.,2014

10. Lumped Transpiration-Soil Saturation Relations
Pure drainage
Infiltration & drainage
Manoli et al., 2014

11. Clouds
Transpiration
z
ABL
LCL
Free Atmosphere
sunrise mid-morning
SoilPlantAtmosphere
mid-afternoon

12. Clouds
z
ρ [Ωm]
200
40
120
ABL
LCL
Free Atmosphere
sunrise mid-morning
SoilPlantAtmosphere
mid-afternoon
Transpiration

13. Convective Rainfall Initiation
Bonetti et al., 2014

14. Convective Rainfall Initiation
),( RHTzz aLCLLCL =
ABLT
sABL
z
H
dt
dz
⋅
+⋅
=
γ
β)1(
( ) ( )( )STGfLETR
c
H wSn
ap
s −−−
⋅
=
ρ
1
( )VPDgg Lss ,ψ=
( ) ( )
100
RH
TeTeVPD asss ⋅−=
( )
dt
dz
TTH
dt
dT
z ABL
aFAs
a
ABL ⋅−+=
( )
dt
dz
ww
LE
dt
dw
z ABL
FA
a
ABL ⋅−+=
λρ
z
Conservation Eqs. (well mixed
ABL ):
ABL potential temperature, Ta
Specific humidity, w
( )[ ] ( )Lrs
w
ws qzKK
t
S
t
SS ψψψϕ
ψ
,++∇⋅∇=
∂
∂
+
∂
∂
Bonetti et al., 2014

15. Modeled ABL-LCL intersection and observed rainfall

16. Soil-Plant-ABL model
Atmospheric feedback
When atmospheric
feedback
Is turned off
RAIN
NO RAIN
MoisturefromFreeAtmosphere

17. 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?