Diurnal evolution of water flow and potential in an individual spruce: experimental and theoretical study

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Diurnal evolution of water flow and potential in an

individual spruce: experimental and theoretical study

P. Cruiziat, André Granier, J.P. Claustres, Denise Lachaize

To cite this version:

P. Cruiziat, André Granier, J.P. Claustres, Denise Lachaize. Diurnal evolution of water flow and

potential in an individual spruce: experimental and theoretical study. International symposium Forest

Tree Physiology, Sep 1988, Nancy, France. �hal-02852999�

Diurnal evolution of

water

flow and

_potential

in

an

individual spruce:

_experimental

and theoretical

study

P.

Cruiziat

1

A.

Granier

2

J.P.

Claustres

1

D. Lachaize

1

1 _{Laboratoire de}

Bioclimatologie,

INRA, Domaine-de-Crouelle,

F-63039

Clermont-Ferrand,

and

2

CRF de

_Nancy,

INRA,

Station de

Sylviculture,

BP 35,

F-54280

_Seichamps,

France

Introduction

We

present

a

model built

_primarily

to

_study

the

water

flow

in a

_single

tree

within

a

forest.

After

_comparing

it with other

avail-able

_systems,

we

_develop

the

characteris-tics of

our

model and its usefulness.

Materials and

Methods

Outline

of the model

The structure of the model

_{(Fig. 1)}

comes from

our idea of how the _spruce we work with is

compartmented;

7

compartments

were

distin-guished:

leaves

(1

uppercrown

(2),

lower

crown

(2),

trunk

(2).

Except

for

leaves,

2 kinds of water reservoirs constitute each of the 3

pre-ceding

levels

_(Jarvis,

1975;

Granier,

1987; Gra-nier and

_{Claustres, 1989):}

a small one

corre-sponding

to the elastic tissues with a small constant of time and a

_larger

one

_representing

the

_sapwood

with a

_large

time constant. Twelve resistances must be

_{specified. Although}

SPICE,

the circuit simulation _program we

_used,

allows

us to introduce variable

capacitances

and resis-tances

_(Cruiziat

and

_Thomas,

_1988),

we did not

think

_they

were _necessary at this

stage

of our

experimental knowledge.

Assumptions

1.

_Sap

moves from

_points

of

high

potential

to

points

of low

_potential.

2. Flow within the different

parts

of the

_system

_obeys

the

_Darcy

equation.

3. Roots are not

_supposed

to have

a

_{capacitance (optional).}

4. All

_parameters

are

_{lumped together.}

5. Neither

branch,

twig

architecture nor

_growth

are considered

(optional).

Values of the

_parameters

and

_input

variables The data consist of

_hourly

measurements of sap flow

(bottom

of the

trunk),

leaf water

poten-tial at 2 levels and

_{transpiration}

rate per tree

(calculated by

the Penman-Monteith

_equation

for the

_stand).

In

addition,

sapwood

cross

sec-tional.area and dimensional characteristics at different levels

provide

information for

starting

values of the

_parameters

_(resistances

and

capacitances).

Then

they

were

_{adjusted (by}

trial and

error)

in order to obtain a combination of values which

reasonably

fit our measurements.

Properties

Under ’ideal’ conditions

_(regular

_{transpiration,}

all

_potentials,

_including

_V1soil

_starting

at 0

MPa),

there is a continuous evolution

of

W

in the different

_parts

of the tree

(Fig.

2);

only

the reservoirs from elastic tissues show no residual deficit at the end of the

_night;

the

_sapwood

tissue still

stays

at a

_{negative yq}

its contribution is about 3% of the

_{daily transpiration.}

This

proportion

increases

_gradually

if _{the yr!!;, falls} for several

days.

The difference between maximum rates of

transpiration (E

max

)

and

absorption

is

_greatly

affected

by

the relative

_magnitude

of root resis-tance.

The _{minimum value of leaves} occurs leaves about 1 h after

_(E

_max

_):

at that

time,

transpiration

and

_absorption

are

_equal.

This fact

_provides

a

means to obtain an estimation of the total

re-sistance of the

_{transpirational pathway (Fig. 3).}

It is

_possible

to

determine

the 3

parameters

(2

resistances and 1

_capacitance)

of the

equi-valent circuit

_having

the same transfer function

(=

transpiration

versus

_absorption).

This trans-formation allows those interested in water

balance of

_drainage

basins to use this

simplified

version as a subrnodel.

Discussion and

Conclusions

This model

was

_designed

to

be

a

_working

tool.

It has 2 main

_purposes:

₁₎

to

contin-uously

bring together

new

_experimental

data within

a

coherent

_{representation;}

and

2)

to

_help

us to

select the

most

crucial

measurements.

Our

model

differs from

other

_published

models

_(Landsberg

et

al.,

1976;

Milne and

_Young,

1985;

Wronski

et

al.,

1985;

Edward

_{et al.,}

_{1986) by}

its struc-ture.

Nevertheless,

for the

moment,

due

to

the lack of

_experimental

_data,

it is

_likely

that several

models of the

same

_object

(e.g.,

same

_species)

can

be

_presented,

each

_having

its own

_strengths

and

weaknesses.

_Therefore,

we

believe that it

is

more

useful

to

_{compare different}

ap-proaches

to

the

same

_object

rather than

different

models

_designed

for different

objects.

References

Cruiziat P. & Thomas R.

(1988)

SPICE,

a circuit simulation program for

physiologists.

Agrono-mie 8, 49-60

Edwards

W.R.N.,

Jarvis

P.G.,

Landsberg

J.J. & Talbot H.

(1986)

A

_dynamic

model for

_studying

flow of water in

_single

trees. Tree

Physiol.

1, 309-324

Granier A.

₍₁₉₈₇₎

Mesure du flux de s6ve brute dans le tronc du

_Douglas

par une

nouvelle m6thode

_thermique.

Ann. Sci. For. 44,

1-14 4

Granier A. & Claustres J.P.

(1989)

Relations

hydriques

dans un

_6pic6a

_(Picea

abies

L.)

en

conditions naturelles: variations

_spatiales.

Oecol. Plant. 2, in press

Jarvis P.

(1975)

Water transfer in

plants.

In: Heat and Mass Transfer in the

_Biosphere.

Part 1. Transfer Processes in Plant Environment.

_(de

Vries D.A. &

Afgan

N.H.,

eds.),

John

Wiley

&

Sons,

New

York,

pp. 369-394

Landsber

g

J.J.,

B!lanchard TW. & Warrit B.

₍₁₉₇₆₎

Studies on the movement of water

_{through apple}

trees. J.

Exp.

Bot.

27,

579-596

Milne R. &

Yourng

P.

(1985)

Modelling

of water movement in trees. In: IFAC Identification and

System

Parameter

Estimation, York, U.K.,

pp. 463-468

Wronsky

E.B.,

Holmes J.W. & Turner N.C.

(1985)

Phase and

_amplitude

relations between

transpiration,

water

_potential

and stem shrink-age. Plant Cell E’nviron.

8,

613-622