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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.
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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?
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