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Assessment of atmospheric and soil water stress impact on a tropical crop: the case of Theobroma cacao under Harmattan conditions in eastern Ghana.



In West Africa, Harmattan-induced atmospheric and soil droughts represent seasonally recurring hazards for Theobroma cacao L. agro-ecosystems. Under the influence of the Harmattan winds, precipitation is impaired and air humidity and temperature reach stressful levels. Climate change is causing an increase in temperature that will drive up the evaporative power of the atmosphere, risking to harshen both the soil and atmospheric stress. This would further threaten the viability of cacao cultivation in this region. To characterize the response of cacao trees to atmospheric and soil drought, we monitored two sub-plots, with and without irrigation, throughout one Harmattan season (November 2019 - March 2020) in the Eastern region in Ghana. For both treatments we recorded: sap flow velocity, photosynthetic active radiation (PAR) above and below the canopy, soil moisture, temperature, air humidity and daily precipitation. Leaf area index (LAI) was estimated from PAR measurements. To characterize drought responses of mature cocoa trees during the day and at the seasonal scale, we developed two boosted regression trees models (BRT) with the environmental variables measured. The atmospheric component of Harmattan-induced drought was found to affect the canopy to a similar extent as soil water stress, both causing a decline in LAI of 33%. This study confirmed the importance of soil drought but highlighted as well the crucial role of atmospheric drought for this species’ transpiration control. Soil and atmospheric water stresses did not have a synergistic effect on transpiration under the studied conditions. The BRT models identified LAI as one of the most influential drivers for sap velocity, which, in turn was sensitive to the interactive effect of both atmospheric and soil drought. Our results highlight that not only reduced precipitation but also increasing atmospheric drought is likely to negatively impact on cacao production in West Africa under increasingly dry conditions imposed by the influence of the Harmattan winds.
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8Rockwinds LBMS SAS, Bordeaux, France
9CIRAD, UMR PHIM, Montpellier 34090, France
:PHIM Plant Health Institute, Univ Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
;CIRAD, DGDRS, Abidjan, Côte dIvoire
<Cocoa Research Institute of Ghana, New Tafo Akyem, Eastern Region Ghana. P.O 8, Ghana
=Basque Centre for Climate Change (BC3), Leioa 48940, Spain
>IKERBASQUE, Basque Foundation for Science, Bilbao 48008, Spain
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1. Introduction
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E-mail address: G;<CC8J8C8IF:BN@E;J:FD * -8C8
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P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
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G?<I@: N8K<I JKI<JJ '<@EQ<I  )>LEKLE;<  #K :8E 9< 8J
JLD<; K?8K JL:? :FE;@K@FEJ NFLC; 9< JKI<JJ=LC =FI :8:8F 8J N<CC @E C@E<
N@K? !)'- <K 8C  )M<I8CC @K @J :C<8I K?8K :8:8F C8:BJ ?@>? KFC
<I8E:< KF ;IFL>?K FI <OKI<D< K<DG<I8KLI<J .?LJ K?< M@89@C@KP F= :LCK@
M8K@FE F= K?@J :IFG FLKJ@;< @KJ E8K@M< I8E>< @E 1<JK =I@:8 @J J<M<I<CP
K?I<8K<E<; 9P =LKLI< :C@D8K< :?8E>< .?< =LKLI< K?I<8KJ KF :8:8F :LCK@
M8K@FE 8I< =LIK?<I <O8:<I98K<; @E =LCC JLE FI C@>?KCP J?8;<; DFEF
:FCKLI8C JPJK<DJ GI<=<II<; 9P =8ID<IJ 8:IFJJ 1<JK =I@:8 =FI K?< ?@>?<I
9;LC8@ <K 8C 
FK? JF@C 8E; 8KDFJG?<I@: ;IFL>?K @DG8:K E<>8K@M<CP FE GC8EK
>IFNK? 8E; GIF;L:K@M@KP ?8M<J <K 8C  &FE> 8E; <IE8::?@
 *C8EKJ ^IJK I<JGFE; KF @E:I<8J@E> M8GFLI GI<JJLI< ;<^:@K 0*
9P :CFJ@E> K?<@I GFI<J FE K?<@I C<8= JLI=8:<J K?< JKFD8K8 KF I<;L:< KI8E
F= I<GIF;L:K@M< JKIL:KLI<J '<;CPE <K 8C  38E> <K 8C  )E
K?< FK?<I ?8E; JF@C ;IFL>?K I<;L:<J K?< :FE;L:K@M@KP F= K?< JF@CGC8EK
K?< ?P;I8LC@: JPJK<D F= K?< GC8EK =IFD <D9FC@JD "F:?9<I> <K 8C
 '8IK@E-K*8LC <K 8C  <PFE; JKFD8K8C :CFJLI< ?@>? 0*
:C< =LIK?<I @E:I<8J@E> I@JB F= ?P;I8LC@: =8@CLI< < CD<@;8 <K 8C 
%FKFNJB8 <K 8C  '8:?8;F <K 8C  <J@;<J I<;L:@E> G?FKF
?<E:< <OGFIK F= :8I9F?P;I8K<J =IFD K?< C<8M<J KF I<GIF;L:K@M< FI>8EJ
=FI _FN<I 8E; =IL@K GIF;L:K@FE ?8M<J <K 8C  ><8 <K 8C 
-<M<I8C 8LK?FIJ ?8M< 8CI<8;P ?@>?C@>?K<; K?< E<<; KF 9<KK<I @EM<JK@
>8K< K?< N8K<I I<C8K@FEJ F= :8:8F LE;<I ^<C; :FE;@K@FEJ 8II 8E;
&F:BNFF;  9LK N< JK@CC C8:B 8 ;<K8@C<; :?8I8:K<I@Q8K@FE F= ?FN
;IFL>?K JKI<JJ @E_L<E:<J :8:8F G?PJ@FCF>P 8E; I<GIF;L:K@FE &8?@M<
<K 8C  .?< <==<:KJ F= I<C8K@M< ?LD@;@KP !)'- <K 8C  8E;
K<DG<I8KLI< ?8M< 9<<E 8;;I<JJ<; 8PDFE; 8E; "8;C<P  
(8A@?8? <K 8C  8E; 8 =<N ^<C; KI@8CJ ?8M< 8;;I<JJ<; JF@C ;IFL>?K
K8E<FLJ <==<:K F= JF@C 8E; 8KDFJG?<I@: ;IFL>?K 8E; K?<@I @EK<I8:K@FE
9;LC8@ <K 8C  'FJ<I <K 8C  -:?N<E;<ED8EE <K 8C 
:?8I8:K<I@Q<; @E I8Q@C  I8>8 $LE@FI <K 8C  8E; #E;FE<J@8 'FJ<I
<K 8C  -:?N<E;<ED8EE <K 8C  9LK @E K?<J< CF:8K@FEJ 0*
8E; 8@I K<DG<I8KLI< I8I<CP I<8:? JKI<JJ=LC :FE;@K@FEJ =FI K?< KI<<J -L:?
<==<:KJ ?8M< EFK 9<<E 8;;I<JJ<; @E K?< 1<JK =I@:8E :8:8F 9<CK N?<I<
I8;@:8CCP ;@==<I<EK 8KDFJG?<I@: :FE;@K@FEJ ;L< KF K?< @E_L<E:< F= K?<
FLJCP JKL;@<; .?< F9A<:K@M< F= K?@J JKL;P @J KF :C8I@=P K?< <==<:KJ F= 8K
DFJG?<I@: 8E; JF@C N8K<I JKI<JJ FE :8:8F KI<< KI8EJG@I8K@FE ;LI@E> K?<
;IP "8ID8KK8E J<8JFE 8E; J?<; C@>?K FE K?< ;I@M<IJ F= KI8EJG@I8K@FE LE
;<I JL:? :@I:LDJK8E:<J )LI ?PGFK?<J@J @J K?8K :8:8F KI<<J N@CC I<JGFE;
K@8C ;L< KF K?< <OKI<D<CP CFN I<C8K@M< ?LD@;@K@<J 8E; C8I>< K<DG<I8KLI<
FJ:@CC8K@FEJ <OG<I@<E:<; LE;<I K?< @E_L<E:< F= K?< "8ID8KK8E
2. Materials and methods
2.1. Study site and experimental design
.NF GCFKJ F= :8:8F KI<<J N@K? 8E; N@K?FLK @II@>8K@FE N<I< DFE@
KFI<; K?IFL>?FLK K?< ;LI8K@FE F= K?< <OG<I@D<EK  <:<D9<I  KF
 '8I:?  8E; K?<@I I<JGFEJ< KF :C@D8K< KI8:B<; :CFJ<CP 9P
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
D<8EJ F= M8I@FLJ J<EJFIJ .?< D<8JLI<; <EM@IFED<EK8C M8I@89C<J N<I<
JF@C MFCLD<KI@: N8K<I :FEK<EK 8K =FLI ;<GK?J =IFD  KF  :D 8@I K<D
G<I8KLI< 8@I I<C8K@M< ?LD@;@KP 8E; G?FKFJPEK?<K@:8CCP 8:K@M< I8;@8K@FE
@> 
.?< JKL;P N8J :FE;L:K<; 8K K?< <OG<I@D<EK8C JK8K@FE F= K?< 8:8F
,<J<8I:? #EJK@KLK< F= !?8E8 ,#! CF:8K<; @E (<N .8=F BP<D 8JK<IE
,<>@FE !?8E8  (  1  D 8JC K K?@J CF:8
K@FE K?< :C@D8K< @J N8ID 8E; ?LD@; 8CC P<8I IFLE; <O:<GK =FI KNF ;IP
J<8JFEJ .?< D8@E ;IP J<8JFE ?8J @KJ :FI< 9<KN<<E <:<D9<I 8E; <9
IL8IP 9LK K?< FEJ<K :8E 9< 8J <8ICP 8J D@; (FM<D9<I 8E; C8JKJ LEK@C
JFD<K@D< @E '8I:? .?< J<:FE; ;IP J<8JFE F::LIJ 9<KN<<E K?< J<:FE;
?8C= F= $LCP 8E; K?< 9<>@EE@E> F= -<GK<D9<I 8E; @J KPG@:8CCP DL:? C<JJ
J<M<I< K?8E K?< D8@E ;IP J<8JFE
.?IFL>?FLK K?< P<8I K<DG<I8KLI< @E .8=F FJ:@CC8K<J 9<KN<<E 8
DFEK?CP 8M<I8>< D@E@DLD F=  KF   8E; 8 DFEK?CP 8M<I8>< D8O@
DLD F=  KF   E@D%N8GFE> 8E; I@DGFE>  EEL8C I8@E
=8CC I8E><J 9<KN<<E  8E;  DD N@K? 8 D<8E M8CL< F=  DD
G<I P<8I E@D%N8GFE> 8E; I@DGFE>  -K8== 
K K?< JKL;P J@K< 8  ?8 :8:8F GC8EK8K@FE N8J <JK89C@J?<; @E $LE<
 8:8F KI<<J Theobroma cacao & F= ?FDF><E<FLJ ><E<K@: FI@
>@E N<I< GC8EK<; N@K? 8  O  D JG8:@E>  KI<<J ?8  LE;<I
E<8K? Gliricidia sepium $8:H GI<M@FLJCP GC8EK<; 8K 8 ;<EJ@KP F=  KI<<J
?8  .?< GC8EK8K@FE :FEJ@JK<; F= =FLI 9CF:BJ N@K?  GCFKJ <8:? 8:?
GCFK :FEK8@E<;  KI<<J GC8EK<; @E ^M< IFNJ N@K? <@>?K KI<<J G<I IFN #E
(FM<D9<I  KNF GCFKJ F=  ?P9I@; D<CFE8;F KI<<J N@K? D<8E
:8EFGP ?<@>?K F=  D<K<IJ N<I< J<C<:K<; =FI K?< JKL;P .?< J<C<:K<;
GCFKJ N<I< CF:8K<; 8K C<8JK  D 8N8P =IFD K?< E<8I<JK J?8;@E> KI<<
8E; K?<I<=FI< N<I< :FEJ@;<I<; 8J 8 KPG@:8C 1<JK =I@:8E =LCC JLE JPJ
K<D .?< KNF JKL;P GCFKJ N<I< J<G8I8K<; 9P K<E IFNJ F= :8:8F KI<<J KF
8MF@; 8EP <;>< <==<:K FI @EK<I8:K@FE 9<KN<<E K?< KNF  @>  IFD K?<
 F= (FM<D9<I  KF K?<  F= '8I:?  KI<<J @E FE< GCFK @II@
>8K@FE KI<8KD<EK N<I< @II@>8K<; N@K?  & G<I KI<< <HL@M8C<EK KF 8G
GIFO@D8K<CP  DD G<I KI<< FE 8CK<IE8K@E> ;8K<J LJ@E> 8 ?FJ<
N?<I<8J KI<<J @E K?< J<:FE; GCFK :FEKIFC FECP I<:<@M<; 8D9@<EK GI<:@G
@K8K@FE .?< @II@>8K@FE N8J <M<ECP 8GGC@<; N@K?@E  :D =IFD K?< KILEB
N?<I< DFJK F= K?< IFFKJ N<I< 9<C@<M<; KF 9< ;@JKI@9LK<; 8II 8E;
&F:BNFF;  #II@>8K@FE :CFJ< KF K?< KILEB N8J EFK I<;L:<; 9P
CFJJ<J ;L< KF :8EFGP @EK<I:<GK@FE K?LJ @KJ <=^:8:P N8J ?@>?<I K?8E 8
I8@E=8CC F=  DD
2.2. Soil properties
::FI;@E> KF 8 JF@C 8E8CPJ@J F= K?< <OG<I@D<EK8C J@K< :FE;L:K<; @E
'8I:?  K?< LGG<I JF@C  :D N8J 8 <LKI@: _LM@JFC N@K? J8E;P
CF8D K<OKLI< 8E; 9<CFN  :D F= ;<GK? K?< JF@C K<OKLI< N8J J8E;P :C8P
CF8D .?< G" N8J  8:IFJJ K?< <EK@I< GIF^C< .?< LGG<I JF@C N8J GFFI
FI>8E@: D8KK<I :FEK<EK N8J  D8>E<J@LD N8J 
KFK8C E@KIF><E N8J   8DDFE@LD N8J  GGD G?FJG?FILJ N8J
 GGD GFK8JJ@LD N8J  8E; <O:?8E><89C< :8C:@LD
N8J   8J<; FE K?< JF@C K<OKLI< 8K 8 ;<GK? F=  :D K?<
9LCB ;<EJ@KP  ^<C; :8G8:@KP   8E; G<ID8E<EK N@CK@E> GF@EK
*1* N<I< <JK@D8K<; @E    8E;  I<JG<:K@M<CP <
CFN  :D K?< M8CL<J F=  8E; *1* N<I<   8E;
 I<JG<:K@M<CP
2.3. Transpiration measurements
FI K?< <EK@I< ;LI8K@FE F= K?< <OG<I@D<EK KI<< KI8EJG@I8K@FE N8J <J
K@D8K<; =IFD D<8JLI<D<EKJ F= J8G M<CF:@KP LJ@E> K?< "<8K ,8K@F
'<K?F; ",' '8IJ?8CC  @M< KI<<J @E <8:? GCFK N<I< J<C<:K<;
N@K? D<8E J; ;@8D<K<IJ D<8JLI<;  :D 9<CFN K?< D8@E 9I8E:? F=
  8E;   :D @E K?< :FEKIFC 8E; @II@>8K<; GCFKJ I<
JG<:K@M<CP  @>   1@K?@E <8:? GCFK K?< KI<<J N<I< J<C<:K<; 98J<;
>I<<EE<JJ ELD9<I 8E; ;@8D<K<I F= AFIHL<KK< 9I8E:?<J <K: 8E; 8MF@;
@E> JG8K@8C :CLJK<I@E> F= DFE@KFI<; KI<<J #E (FM<D9<I  N< @E
JK8CC<; FE< ?<8K GIF9< J<EJFI -  8JKJ<EJFIJ /- FE <8:? J<
C<:K<; KI<< 8:? J<EJFI :FEJ@JK<; F= K?I<< GIF9<J  DD @E C<E>K? 
DD @E ;@8D<K<I 8E;  DD 8O@8C ;@JK8E:< 8G8IK .?< :<EKI8C GIF9< :FE
K8@E<; 8E <M8EF?D ?<8K<I 8E; K?< C8K<I8C KNF GIF9<J FE< LGJKI<8D
8E; FE< ;FNEJKI<8D N@K? I<JG<:K KF K?< ?<8K<I :FEK8@E<;  K?<ID@JKFIJ
GC8:<; 8K  DD  DD 8E;  DD =IFD K?< J<EJFI K@G KF DFE@KFI
J8G _FN 8:IFJJ K?< <EK@I< ;<GK? F= K?< J8GNFF; .?< K?<ID@JKFI K<DG<I
8KLI< J<EJFI :FEJ@JK<; F= 8 % GI<:@J@FE I<J@JKFI 8E; 8 % K?<ID@JKFI
N@I<; K?IFL>? 8 K?I<< N@I< ?8C= 9I@;>< :FEE<:K<; KF 8 ;8K8CF>><I G<I @I
Fig. 1. -:?<D8K@: I<GI<J<EK8K@FE F= K?< ^<C; <OG<I@D<EK8C GC8E N@K? 8E FM<IM@<N F= K?< D<8JLI<D<EKJ K8B<E .?< <OG<I@D<EK :FDG8I<; 8E @II@>8K<; GCFK  IFNJ
F=  KI<<J KF 8 :FEKIFC I8@E=<; FE< .?< <OG<I@D<EK8C GCFKJ N<I< J<G8I8K<; 9P 8 9L`<I F= K<E IFNJ F= KI<<J #E <8:? GCFK N< D<8JLI<;  J8G M<CF:@KP :IFJJ<J 
JF@C DF@JKLI< JHL8I<J  K<DG<I8KLI< 8E; 8@I I<C8K@M< ?LD@;@KP ;FKJ  G?FKFJPEK?<K@:8CCP 8:K@M< I8;@8K@FE *, 89FM< 8E; 9<CFN K?< :8EFGP ;FKJ 8E; 
C@KK<I=8CC GIF;L:K@FE ?8K:?<; G8I8CC<CF>I8DJ .?< GFJ@K@FE F= K?< J<EJFIJ I<_<:KJ K?<@I I<8C GFJ@K@FE @E K?< ^<C; <OG<I@D<EK !I8G?@:J 9P *@<KIF <CC8 -8C8 ;I8N
@E> F= K?< :8:8F KI<< 9P JK<CC< ,@9<PI<
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
I@>8K@FE KI<8KD<EK , 8DG9<CC -:@<EK@^: &F>8E /. /- .?<
8::LI8:P F= K?< K?<ID@JKFIJ N8J   8E; K?< I<JFCLK@FE N8J 
 .?< :<EKI8C E<<;C< N8J ?<8K<; 9P 8 0 GLCJ< F=  J<:FE;J GFN<I<;
9P K?< ;8K8CF>><I 8E; I<;L:<; KF 0 K?IFL>? 8 ?<8K :FEKIFC 9F8I; 8JK
J<EJFIJ /-
8 D@E@DLD ;@JK8E:< F=  :D =IFD 8EP EF;< FI 9I8E:?@E> 8E; 8K 8 D@E
@DLD ?<@>?K =IFD K?< JF@C F=  :D 8IB K?@:BE<JJ N8J   :D
E KI<<J 8E; N8J B<GK @E GC8:< KF GIFK<:K K?< NFLE; =IFD ;IPE<JJ
8E; =LE>8C 8KK8:BJ .?< GIF9<J N<I< GIF>I8DD<; @E 8::FI;8E:< N@K?
K?< L8C '<K?F; GGIF8:? '  FIJK<I  .?< ' :FD9@E<J
K?< KI8;@K@FE8C 8GGIF8:? KF :8C:LC8K< J8G M<CF:@KP =IFD ?<8K GLCJ< M<CF:
@KP '8IJ?8CC  N@K? K?< .D8O '<K?F; )"( <K 8C  .?<
C8KK<I 8CCFNJ KF :8GKLI< ?@>? 8E; CFN _FN I8K<J 9FK? LGN8I; 8E; ;FNE
N8I; 8CFE> K?< JK<D  FIJK<I  .?I<< M8CL<J F= ?<8K GLCJ< M<CF:@KP
N<I< I<:FI;<; <M<IP  D@ELK<J G<I J<EJFI 8:? M8CL< N8J :8C:LC8K<;
=IFD K?< K<DG<I8KLI< ;@==<I<E:< 9<KN<<E <8:? G8@I F= LG 8E; ;FNE
_FN K?<ID@JKFIJ CF:8K<; 8K K?I<< ;<GK?J N@K?@E K?< J8GNFF;  
8E;  DD =IFD K?< 98IB -8G M<CF:@KP N8J :8C:LC8K<; =FI <8:? F= K?<
K?I<< GFJ@K@FEJ 8E; K?<E LGJ:8C<; KF 8E @EK<>I8K<; M8CL< F= J8G _LO =FI
<8:? KI<< K?IFL>? 8 N<@>?K<; JLD 98J<; FE K?< J8GNFF; 8I<8 <JK@
D8K<; K?IFL>? NFF; :FI@E> 8JJF:@8K<; KF K?< JG<:@^: I8;@8C GFJ@K@FE
FIJK<I  <=FI< LGJ:8C@E> KF 8 J@E>C< M8CL< G<I KI<< <8:? :FLGC<
F= K?<IDF:FLGC<J N8J :8C@9I8K<; KF ?8M< K?< Q<IF =FI J8G M<CF:@KP N?<E
E@>?K GFK<EK@8C <M8GFKI8EJG@I8K@FE N8J Q<IF -  C<9P <K 8C 
LI><JJ <K 8C  #E K?@J JKL;P @K N8J 8JJLD<; K?8K ;LI@E> K?< K?I<<
DFEK?J F= ;IP J<8JFE K?< J8GNFF; 8I<8 @E:I<D<EK @J E<>C@>@9C< K?<I<
=FI< :?8E><J @E KI8EJG@I8K@FE 8I< 8GGIFO@D8K<; KF M8I@8K@FEJ @E J8G
2.4. Soil VWC
-F@C MFCLD<KI@: N8K<I :FEK<EK 01 N8J DFE@KFI<; @E KNF _8K CF
:8K@FEJ G<I GCFK <HL@;@JK8EK  :D KF 8CC JLIIFLE;@E> KI<<J 8K =FLI
;<GK?J    8E;  :D N@K? .,)-  :8G8:@K8E:< GIF9<J
'., >IFLG *LCCD8E1 /-  @>   .?< :?FJ<E ;@JK8E:< 8C
CFN<; KF :8GKLI< K?< 8M<I8>< 01 F= 9FK? K?< @II@>8K<; 8E; K?< EFE
@II@>8K<; GCFKJ 8MF@;@E> GFK<EK@8C 9@8J<J ;L< KF LE<M<E @II@>8K@FE @E K?<
=FID<I <JG@K< K?<@I ;@JK8E:< =IFD K?< KI<<J K?< CF:8K@FEJ =FI 01
DFE@KFI@E> N<I< J?8;<; 9P K?< GCFKJ:CFJ<; :8EFGP <==<:K@M<CP C@D@K
@E> HL@:B <M8GFI8K@FE F= N8K<I 8=K<I 8 N8K<I@E> <M<EK 9< @K I8@E=8CC FI
@II@>8K@FE .?< .,)-  J<EJFIJ <JK@D8K< JF@C 01 =IFD D<8JLI<
D<EKJ F= K?< 8GG8I<EK ;@<C<:KI@: G<ID@KK@M@KP @E K?<  D& F= JLIIFLE;
@E> D<;@LD FI K?@J JKL;P K?< D8EL=8:KLI<IJ :8C@9I8K@FE =FI 8 ><E<I@:
D@E<I8C JF@C N8J LJ<;  M8CL< F= JF@C 01 G<I GIF9< N8J I<:FI;<; FE 8
, ;8K8CF>><I <M<IP  D@ELK<J =IFD (FM<D9<I   KF '8I:?
  #E FE< @EJK8E:< K?< JF@C 01 N8J KI8EJ=FID<; @EKF N8K<I GF
G<;FKI8EJ=<I =LE:K@FE @K N8J 8;FGK<; K?< DF;<C 9P 08E !<EL:?K<E
!<EL:?K<E  .?< G8I8D<KI@Q8K@FE F= K?< DF;<C N8J ;FE< N@K?
K?< , G8:B8>< soilphysics 4.0 -@CM8 8E; ;< &@D8  8E; K?< JF@C
2.5. Leaf area index
&<8= I<8 #E;<O &# N8J <JK@D8K<; =IFD D<8JLI<D<EKJ F= G?FKF
JPEK?<K@:8CCP 8:K@M< I8;@8K@FE *, 89FM<   8E; 9<CFN   K?<
:8EFGP  @>   @E 8E @EM<IK<; =FID F= <<IJ C8N H  '<8JLI<
D<EKJ F= *, N<I< :FCC<:K<; =IFD (FM<D9<I K?  KF '8I:? K?
 N@K? 8 9I@<= @EK<IILGK@FE =IFD <:<D9<I K?  KF $8EL8IP
K?  #E:FD@E> G?FKFJPEK?<K@: 8:K@M< I8;@8K@FE *,
 89FM< K?< :8EFGP N8J D<8JLI<; <M<IP  D@ELK<J 8K
FE< GFJ@K@FE @E K?< @II@>8K<; GCFK .?< *, J<EJFI -+ GF><< @E
JKILD<EKJ -8EK8 'FE@:8  /- N8J DFLEK<; FE KFG F= 8  D C<M
<CC<; @IFE G@G< GC8EK<; @E K?< JF@C @<  D 89FM< K?< :8EFGP ;;@K@FE
8CCP *, N8J DFE@KFI<; LE;<I K?< :8EFGP 8K K?I<< CF:8K@FEJ @E <8:?
GCFK N@K? K?I<< J<EJFIJ DFLEK<; FE C<M<CC<; GFC<J 8K  :D ?<@>?K .?<
<OK@E:K@FE :F<=^:@<EK % E<:<JJ8IP KF :8C:LC8K< &# =IFD *, ;8K8 H
 ;<G<E;J FE K?< JFC8I 8E>C<   8E; 8 C<8= 8E>C< ;@JKI@9LK@FE :F<=^
:@<EK   8E; N8J :8C:LC8K<; 8GGCP@E> H  8DG9<CC  .?< G8
I8D<K<I N8J :8C:LC8K<; 8J K?< I8K@F F= M<IK@:8C KF ?FI@QFEK8C GIFA<:
K@FEJ F= K?< :8EFGP 8DG9<CC  8J<; FE ^<C; D<8JLI<D<EKJ
N8J <M8CL8K<; 8K  :FII<JGFE;@E> KF 8E <CC@GJF@; C<8= 8E>C< ;@JKI@9L
K@FE  I<C@89C< <JK@D8K@FE F= % @J GFJJ@9C< FECP N?<E K?< JFC8I 8E>C< @J
:CFJ< KF K?< Q<E@K?  C<I:?@E><I 8E; 3L  .?FD8J 8E; 1@EE<I
 K?<I<=FI< N< <JK@D8K<; &# =IFD *, D<8JLI<D<EKJ :FCC<:K<;
9<KN<<E  8E;  JFC8I K@D< LIK?<IDFI< KF 8MF@; FM<I<JK@
D8K@FE F= &# ;L< KF <O:<JJ ;@I<:K I8;@8K@FE I<8:?@E> K?< J<EJFIJ LE;<I
K?< :8EFGP ;8K8 =IFD <8:? J<EJFI N<I< JDFFK?<; 8E; @EK<IGFC8K<;
N@K? K?< Daniell DF;@^<; FLI@<I D<K?F; IF:BN<CC <K 8C 
-KF==<I 8E; CFFD=@<C;  8E; K?< K?I<< I<JLCK@E> :LIM<J 8M<I8><;
KF ><K 8 ^E8C &# M8CL< =FI K?< <EK@I< GCFK
&# :?8E>< ;L< KF ;<=FC@8K@FE N8J 8CJF DFE@KFI<; K?IFL>? K?< J8D<
DFE@KFI@E> G<I@F; N@K? 8 J<K F= =FLI C@KK<I KI8GJ G<I KI<8KD<EK  @>
 8:? KI8G :FEJ@JK<; FE 8 JLJG<E;<; ^E< E<K F=  K?8K N8J GFJ@
K@FE<; @E I8E;FD@Q<; CF:8K@FEJ N@K?@E <8:? GCFK .?< C@KK<I GIF;L:K@FE
N8J :FCC<:K<; <M<IP  ;8PJ 8E; FM<E;I@<; 8K   =FI  ?FLIJ KF F9
K8@E K?< ;IP N<@>?K .F :FEM<IK K?< C<8= ;IP N<@>?K @E &# @E K?< 9<>@E
E@E> F= K?< <OG<I@D<EK K?< D<8E JG<:@^: C<8= 8I<8 -&
 N8J :8C:LC8K<;  J8DGC< F=  C<8M<J  =IFD K?<
CFN<I D@;;C< 8E; KFG :8EFGP =FI <8:? KI<8KD<EK GCFK N8J J:8EE<; FE
8 I<=<I<E:< JLI=8:< 8E  J?<<K .?< KFK8C 8I<8 N8J <JK@D8K<; 8J K?<
G<I:<EK8>< F= K?< @D8><J K?8K N8J EFK N?@K< N@K? #D8><$ 8
,8J98E;  .F F9K8@E K?< -& K?< 8M<I8>< C<8= 8I<8 N8J ;@M@;<;
9P @KJ FM<E;IP N<@>?K
2.6. Atmospheric conditions
@I K<DG<I8KLI< 8E; I<C8K@M< ?LD@;@KP N<I< CF>><; ?FLICP @E <8:?
GCFK N@K? N@K? KNF @LKKFEJ -  "P>IF:?IFE @LKKFE&@EB
&& 1?@K<N8K<I 1#/- 89FM< K?< :8EFGP 8K :8  D ?<@>?K .F GIF
K<:K K?< J<EJFIJ =IFD ;@I<:K I8;@8K@FE 8E; GI<:@G@K8K@FE K?<J< N<I< @E
JK8CC<; =8:@E> K?< >IFLE; >CL<; KF K?< @EK<IE8C G8IK F= 9FKKC< :8GJ
@>   J K<DG<I8KLI< 8E; I<C8K@M< ?LD@;@KP N<I< CF>><; ?FLICP
8GGC@<; @E FI;<I KF F9K8@E ?8C=?FLICP K@D< J<I@<J K?8K D8K:?<; K?FJ< F=
K?< FK?<I D<8JLI<; M8I@89C<J @E K?< ;8K8 J<K .?< M8GFLI GI<JJLI<
;<^:@K 0* 8E; E@>?KK@D< GFK<EK@8C <M8GFKI8EJG@I8K@FE I<HL@I<; KF
:8C@9I8K< K?< Q<IF GF@EK =FI J8G M<CF:@KP N<I< :8C:LC8K<; =FCCFN@E> K?<
) *<ED8E'FEK<@K? D<K?F; CC<E <K 8C  9P D<8EJ F= K?<
*PK?FE G8:B8>< opencroplib==0.1.5<IE@ <K 8C  .?< :8C:L
C8K@FE F= K?< E@>?KK@D< GFK<EK@8C <M8GFKI8EJG@I8K@FE LJ<; 8 N@E; M<CF:
@KP 89FM< K?< :8EFGP F=  8K  D ?<@>?K @E :FDGC@8E:< N@K?
K?< 8M<I8>< E@>?KK@D< M8CL< =IFD 8 N<8K?<I JK8K@FE 8K C<JJ K?8E  BD
=IFD K?< J@K< 8@CP GI<:@G@K8K@FE ;8K8 9<KN<<E ):KF9<I    8E;
'8I:?    N<I< I<KI@<M<; =IFD K?< /E@^<; !8L><8J<; E8CP
J@J F= 8@CP *I<:@G@K8K@FE F= K?< () C@D8K< *I<;@:K@FE <EK<I *
-K8== 
2.7. Statistical analysis
*I@FI KF 8E8CPJ@J N< :?<:B<; =FI J<EJFI >C@K:?<J ELD<I@:8C 8IK<=8:KJ
F= K?< J<EJFI I8N J@>E8C 8E; D<8JLI<D<EK <IIFIJ :8LJ<; 9P =8LCKP J<E
JFIJ CC D<8JLI<; M8I@89C<J 9LK J8G M<CF:@KP N<I< KI<8K<; 8J :FEK@EL
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
FLJ N@K? K?< ?PGFK?<J@J K?8K K?<P :8EEFK 89ILGKCP :?8E>< FM<I ?8C= 8E
?FLI FI K?@J I<8JFE @K N8J ;<:@;<; KF JKL;P K?< <MFCLK@FE F= K?<@I ^IJK
;<I@M8K@M< @E K@D< 8E; :FEJ@;<I 8J FLKC@<IJ K?< GF@EKJ N?FJ< 89JFCLK<
M8CL< C@<; FLKJ@;< K?< KNF JK8E;8I; ;<M@8K@FEJ :FE^;<E:< @EK<IM8C 
>I8G?@:8C <M8CL8K@FE F= K?< ;8K8 GF@EKJ _8>><; 8J FLKC@<IJ N8J :8II@<;
FLK 9<=FI< K?<P N<I< ;@J:8I;<;
2.7.1. GAMM analysis
 ><E<I8C@Q<; 8;;@K@M< D@O<; DF;<C !'' N8J LJ<; KF DF;<C
8E; 8JJ<JJ K?< ;@==<I<E:<J 9<KN<<E K?< @II@>8K<; 8E; EFE@II@>8K<; GCFK
;PE8D@:J F= &# FM<I K@D< .?< !' =8D@CP F= DF;<CJ N8J :?FJ<E GI@
D8I@CP 9<:8LJ< &# N8J <OG<:K<; KF <O?@9@K 8 :FDGC<O EFEC@E<8I I<C8
K@FEJ?@G N@K? K?< <EM@IFED<EK -<:FE;CP @K N8J E<:<JJ8IP KF LJ< 8
!'' 9<:8LJ< &# D<8JLI<D<EKJ @E K@D< N<I< EFK :FDGC<K<CP @E;<
G<E;<EK 8J K?<P N<I< K8B<E 9P K?< J8D< J<EJFIJ &8JKCP K?< :?F@:< KF
LJ< 8 !'' N8J ;@:K8K<; 9P K?< =8:K K?8K =FI <8:? ;8K< N< ?8; FECP =<N
GF@EKJ =FI &# K?LJ C8I>< M8I@8E:< #K NFLC; ?8M< 9<<E ;@=^:LCK KF 8G
GI<:@8K< K?< ;@==<I<E:< N@K?FLK K?< !'' DF;<C :8GKLI@E> K?< K@D<
<MFCLK@FE F= &# .?< 9L@CK !'' DF;<C ^KK<; 8 >8LJJ@8E ;@JKI@9LK@FE
=FI &# :FEK@ELFLJ M8I@89C< LJ@E> K?< KI<8KD<EK @II@>8K<; FI :FEKIFC
8J ^O<; <==<:KJ 8E; K8B@E> @EKF 8::FLEK K?< I8E;FD J<EJFIKFJ<EJFI
M8I@89@C@KP .?< <==<:K F= K@D< N8J ^KK<; 9P 8 JDFFK? K<ID LJ@E> L:?FE
JGC@E<J 8CCFN@E> K?< K?< GI<;@:K@FEJ KF K8B< @EKF 8::FLEK K?< ;@==<I<E
K@8C @E N8K<I 8M8@C89@C@KP ;L< KF @II@>8K@FE .?< !''DF;<C<; &# =FI
FM<IC8GG@E>  :FE^;<E:< @EK<IM8CJ 8J 8 J@>E@=@:8EK ;@==<I<E:< 9<
KN<<E KI<8KD<EK C<M<CJ =FI 8 >@M<E G<I@F; CC K?<J< 8E8CPJ<J N<I< G<I
=FID<; @E K?< , <EM@IFED<EK M .<8D  LJ@E> G8:B8><J GCPI
1@:B?8D  K@;PM<IJ< M 1@:B?8D <K 8C  D>:M
1FF;  8E; @KJ8;L> M M8E ,@A <K 8C 
2.7.2. Boosted Regression Tree analysis
1< LJ<; FFJK<; ,<>I<JJ@FE .I<<J 8E8CPJ@J ,. DF;<CC@E> KF GI<
;@:K KI8EJG@I8K@FE =IFD :C@D8K@: M8I@89C<J C@K? <K 8C  ,. LJ<J
KNF 8C>FI@K?DJ I<>I<JJ@FE KI<< 8E; 9FFJK@E> .I<<98J<; I<>I<JJ@FE
DF;<CJ ;<J:I@9<; =FI LJ< @E <:FCF>P 9P <8K? 8E; 89I@:@LJ 
G8IK@K@FE K?< JFCLK@FEJ JG8:< N@K? 8 J<K F= ILC<J @;<EK@=P@E> K?< DFJK ?F
DF><E<FLJ I<>@FEJ @E K<IDJ F= I<JGFEJ< KF GI<;@:KFIJ .?<P K?<E ^K 8
:FEJK8EK KF <8:? I<>@FE ^KK@E> K?< 8M<I8>< I<JGFEJ< @E K?8K I<>@FE N@K?
K?< 8JJLDGK@FE F= EFID8CCP ;@JKI@9LK<; <IIFIJ 1@K? <8:? @K<I8K@FE K?<
KI<< >IFNJ 9P I<G<8K<;CP 8GGCP@E> K?< 8E8CPJ@J F= K?< GI<;@:KFIJ JG8:< KF
@KJ FNE FLKGLK LEK@C 8 LJ<I;<^E<; JKFGG@E> :I@K<I@FE @J I<8:?<; .I<<
98J<; DF;<CJ 8I< @EKL@K@M< <8JP KF M@JL8C@Q< 8E; 8I< =8@ICP @EJ<EJ@K@M< KF
FLKC@<IJ D@JJ@E> ;8K8 8E; ;8K8 KPG<J ELD<I@: 9@E8IP :8K<>FI@:8C <K:
9LK K?<P C8:B K?< 8::LI8:P F= FK?<I D<K?F;J JL:? 8J !&' 8E; !''
.F :FDG<EJ8K< =FI K?@J ;FNEJ@;< @K @J :FEM<E@<EK KF :FD9@E< KI<<98J<;
DF;<CJ N@K? 9FFJK@E> .?< @;<8 9<?@E; K?< 9FFJK@E> D<K?F;J @J K?8K @K @J
DFI< GIF989C< KF ^E; D8EP ILC<J F= K?LD9 K?8E KF ^E; 8 J@E>C< ?@>?CP
8::LI8K< GI<;@:K@FE ILC< -:?8G@I<  #K @J K?<I<=FI< DFI< :FEM<
E@<EK KF 8GGIFO@D8K< K?< JFCLK@FE 9P 8M<I8>@E> K?< I<JLCKJ F= 8 C8I><
ELD9<I F= ILC<J F= K?LD9 I8K?<I K?8E 8@D@E> =FI 8 LE@HL< ?@>?CP 8::L
I8K< FE< .?< ,. LJ<J 9FFJK@E> 8J 8 N8P KF <M8CL8K< K?< >I8;@<EK F= K?<
GI<;@:KFIJ JG8:< 9P =F:LJ@E> FE K?< M8I@8K@FE @E K?< I<JGFEJ< EFK <O
GC8@E<; P<K 9P K?< DF;<C 8K 8 >@M<E JK<G 8E; ^KK@E> 8 E<N KI<< KF @KJ
I<J@;L8CJ C@K? 8E; &<8K?N@:B  .?IFL>? 9FFJK@E> ;<:@J@FE KI<<J
8I< ^KK<; @K<I8K@M<CP KF K?< KI8@E@E> ;8K8 @E:I<8J@E>CP <DG?8J@J@E> K?<
N@J< <O@JK@E> KI<<J 8I< C<=K LE:?8E><; 8J K?< DF;<C @J <EC8I><; 9LK K?<
^KK<; M8CL< @J <JK@D8K<; 8K <8:? JK<G KF I<_<:K K?< :FEKI@9LK@FE F= K?<
E<NCP 8;;<; KI<< .?< ^E8C ,. DF;<C @J 8 C@E<8I I<>I<JJ@FE DF;<C
N?<I< <8:? K<ID @J 8 KI<<
^KK@E> K?< <M8CL8K@FE CFFB<; 8K K?< ;@==<I<E:< 9<KN<<E K?< KI8@E@E>
;8K8 :F<=^:@<EK F= :FII<C8K@FE 8E; K?< :F<=^:@<EK F= :FII<C8K@FE =FI K?<
=FC; :IFJJM8C@;8K@FE .?< JB@CC F= K?< DF;<CJ @EJK<8; N8J 8JJ<JJ<;
9P GCFKK@E> K?< GI<;@:K<; M8CL<J 8>8@EJK K?< D<8JLI<; FE<J C@K? 8E;
&<8K?N@:B  C@K? <K 8C 
.?< ,. 8E8CPJ<J N<I< :8II@<; FLK LJ@E> , M .<8D  8E;
K?< >9D !I<<EN<CC <K 8C  8E; ;@JDF "@AD8EJ <K 8C 
G8:B8><J .?< G8I8D<K<I@Q8K@FE F= K?< KNF DF;<CJ :8E 9< =FLE; @E .89
.NF ,. DF;<CJ N<I< 9L@CK LJ@E>  F= K?< ;8K8J<K KF <OGC8@E K?<
I<C8K@M< @DGFIK8E:< F= K?< GFK<EK@8C ;I@M<IJ F= KI8EJG@I8K@FE ;LI@E> K?<
;IP "8ID8KK8E J<8JFE .?< I<D8@E@E>  N8J LJ<; KF ^K K?< DF;<CJ
8E; <M8CL8K< K?<D 8>8@EJK K?< D<8JLI<; M8CL<J .?< KNF ,. DF;<CJ
:FEJ@;<I<; JF@C MFCLD<KI@: N8K<I :FEK<EK 01 G?FKFJPEK?<K@: 8:K@M<
I8;@8K@FE 89FM< K?< :8EFGP *, 8E; K?< M8GFLI GI<JJLI< ;<^:@K F= K?<
8KDFJG?<I< 0* 8J <EM@IFED<EK8C GI<;@:KFIJ K?< C<8= 8I<8 @E;<O
&# F= K?< KNF GCFKJ 8J @E;@:8KFI F= K?< ><E<I8C JK8K< F= K?< :8EFGP 8E;
K?< ;@8D<K<I F= @E;@M@;L8C KI<<J 8J 8 GIFOP =FI K?<@I ;@D<EJ@FE .?< ^IJK
DF;<C DF;<C  LJ<; K?< ?8C=?FLICP ;8PK@D< ;8K8 *,  
 KF @EM<JK@>8K< K?< @DGFIK8E:< F= <8:? 8=FI<D<EK@FE<;
GI<;@:KFIJ @E ;<K<ID@E@E> K?< ;8@CP ;8PK@D< :P:C< F= J8G M<CF:@KP .?<
J<:FE; DF;<C DF;<C  @EM<JK@>8K<; K?< IFC< F= K?< J8D< GI<;@:KFIJ 8K
K?< K@D< J:8C< F= FE< ;8P =FI K?@J K?< @EGLK M8I@89C<J 8J N<CC 8J J8G M<
CF:@KP N<I< 8M<I8><; FM<I K?< G<I@F; F= K?< ;8P N@K? 8 *, 89FM< 
.F 8MF@; GFJJ@9C< :FM8I@8K@FEJ ;L< KF 8 :FDDFE ;8@CP :P:C< =FI K?<
^IJK DF;<C @K N8J ;<:@;<; KF I<DFM< K?< ;8@CP G8KK<IE =IFD K?< M8GFI
GI<JJLI< ;<^:@K 8E; I8;@8K@FE D8@EK8@E@E> FECP K?< <==<:KJ ;L< KF K?<
M8I@8K@FE =IFD K?< 8M<I8>< ;8@CP :P:C< .?< >CF98C ;8@CP G8KK<IE N8J
D8@EK8@E<; 8J 8 J<G8I8K< M8I@89C< @< K?< ?FLI F= K?< ;8P "FLI 8E;
@E:CL;<; 8DFE> K?< GI<;@:KFIJ
.?< KNF DF;<CJ N<I< 98J<; FE K?< 8JJLDGK@FE F= 8 EFID8C ;@JKI@9L
K@FE F= K?< ;8K8 =8D@CP  !8LJJ@8E 8E; G8I8D<K<I@Q<; KF 8MF@;
FM<I^KK@E> .89  C@K? 8E; &<8K?N@:B  C@K? <K 8C 
Table 1
#EK<I8:K@FEJ 9<KN<<E K?< M8I@89C<J :FEJ@;<I<; @E K?< ,. 'F;<C  @E <OGC8@E
@E> :8:8F J8G M<CF:@KP 8K 8 JL9;8@CP K@D<J:8C< FI <8:? G8@I F= M8I@89C<J K?<
K89C< I<GFIKJ K?< D<8E M8CL< F= K?< I<J@;L8CJ N?@:? I<GI<J<EKJ K?< JKI<E>K? F=
K?< @EK<I8:K@FE #E 9FC; K?< @EK<I8:K@FEJ :FEJ@;<I<; JKIFE> K?LJ J@>E@=@:8EK
9P K?< DF;<C
"FLI @8D<K<I 0* *,79FM< &# -F@C701
"FLI     
@8D<K<I    
0*   82788.32 71754.54 
*,79FM<   
&#   
-F@C701 
Table C.1
*8I8D<KI@Q8K@FE F= K?< ,. DF;<CJ KF GI<;@:K K?< KI8EJG@I8K@FE ;LI@E> K?< ;8P
8K 8 D@ELK< K@D< @EK<IM8C 'F;<C  8E; 8K 8 ;8@CP K@D< JK<G 'F;<C  
,. DF;<C I<HL@I<J K?< ;<=@E@K@FE F= 8 J<K F= ?PG<IG8I8D<K<IJ =8D@CP  K?<
KPG< F= JK8K@JK@:8C <IIFI ;@JKI@9LK@FE :?8I8:K<I@Q@E> K?< ;8K8 @E FLI :8J< !8LJJ
@8E KFC<I8E:< KC  K?< K?I<J?FC; @E M8I@8E:< :?8E>< LE;<I N?@:? KF JKFG K?<
DF;<C I<@K<I8K@FE 98> =I8:K@FE 9>  K?< =I8:K@FE F= ;8K8J<K KF LJ< =FI K?<
KI8@E@E> F= <8:? KI<< .?< I<D8@E@E> ;8K8 @J LJ<; 8K <8:? JK<G KF :IFJJ M8C@;8K<
K?< J<K F= I<C8K@FEJ =FLE; ELD9<I F= KI<<J EK  K?< ELD9<I F= KI<<J E<:<J
J8IP =FI FGK@D8C GI<;@:K@FE #K @J ;<K<ID@E<; 98J<; FE KC 8E; 9> KI<< :FDGC<O
@KP K:  K?< D8O@DLD C<M<C F= @EK<I8:K@FE 9<KN<<E M8I@89C<J KF :FEJ@;<I @E 8
KI<< C<8IE@E> I8K< CI  ;<K<ID@E<J K?< :FEKI@9LK@FE F= <8:? KI<< KF K?< >IFN
@E> DF;<C .?< J<<; ELD9<I LJ<; N8J  
-K<G 8D@CP KC 9> EK K: CI
'F;<C   D@E !8LJJ    
'F;<C   ;8P !8LJJ    
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
3. Results
3.1. Climatic conditions
.?< 8M<I8>< ;8@CP K<DG<I8KLI< ;LI@E> K?< <OG<I@D<EK  F= (F
M<D9<I   F= '8I:?  N8J    8E; K?< D8O@
DLD 8E; D@E@DLD I<:FI;<; K<DG<I8KLI<J N<I<   8E;   I<
JG<:K@M<CP  @>  <KN<<E $8EL8IP 8E; <9IL8IP K?< J@K< <OG<I@<E:<;
K?<J@J =FI J<M<I8C ?FLIJ .<DG<I8KLI<J 89FM< K?< K?I<J?FC; 8K N?@:?
G?FKFJPEK?<J@J ;<:C@E<J   N<I< I<:FI;<; K?IFL>?FLK K?< <EK@I<
G<I@F; LE;<I 8E8CPJ@J FE 8M<I8>< =FI   ?FLIJ 8 ;8P  @> 
.<DG<I8KLI<J 9<CFN K?< CFN<I K?I<J?FC; =FI G?FKFJPEK?<K@: <=^:@<E:P
  @EJK<8; F::LII<; FECP @E $8EL8IP 8E; <9IL8IP N?<E K?<
"8ID8KK8E N@E;J I<8:?<; K?< J@K< ,<C8K@M< ?LD@;@KP =<CC 9<CFN  =FI
K?< ^IJK K@D< @E <8ICP <:<D9<I 8E; =IFD C8K< <:<D9<I LEK@C '8I:?
K?< J@K< <OG<I@<E:< J<M<I8C ?FLIJ N@K? ," 9<CFN  8CDFJK ;8@CP
@>  I<8:?@E> LG KF ^=K<<E ?FLIJ G<I ;8P 9<CFN  @E $8EL8IP
LI@E> FLI JKL;P G<I@F; K?< KFK8C GI<:@G@K8K@FE N8J  DD F= N?@:?
 DD =<CC @E '8I:? N?@C< K?< I<D8@E@E>  DD N<I< ;@JKI@9LK<; @E
JGFI8;@: <M<EKJ =IFD <:<D9<I KF <9IL8IP *I@FI KF K?< FEJ<K F= FLI
JKL;P @E ):KF9<I 8E; (FM<D9<I  K?< J@K< I<:<@M<;  DD F= GI<
:@G@K8K@FE .?< 8M<I8>< JF@C 01 8:IFJJ K?< <EK@I<    :D GIF^C<
N8J 8CN8PJ ?@>?<I @E K?< @II@>8K<; KI<8KD<EK K?8E @E K?< :FEKIFC
K?IFL>?FLK K?< <OG<I@D<EK -F@C 01 N8J 89FM<  @E $8EL8IP 8E;
<9IL8IP @E K?< @II@>8K<; GCFK N?@C< @E K?< EFE@II@>8K<; :FEKIFC GCFK
01 :FEK@EL<; KF ;<:C@E< 9<CFN  FM<I K?< J8D< G<I@F; 01
HL@:BCP I<:FM<I<; @E 9FK? KI<8KD<EKJ @E '8I:? N?<E I8@EJ I<JLD<;
Fig. 2. C@D8K@: :FE;@K@FEJ ;LI@E> K?< JKL;P G<I@F; &<=K KFG D<8E ;8@CP 8@I K<DG<I8KLI< JFC@; 9C8:B C@E< K?< K?I<J?FC;J =FI G?FKFJPEK?<K@: ;<:C@E<  8E;
  8E; F9J<IM<; 98J< K<DG<I8KLI< =FI M<><K8K@M< >IFNK?   &8?@M< <K 8C  ;8J?<; C@E<J 8E; K?< I8E>< F= M8CL<J J?8;<; 8I<8 8I< ;<G@:K<; &<=K
9FKKFD D<8E ;8@CP I<C8K@M< 8@I ?LD@;@KP JFC@; 9C8:B C@E< N@K? K?< K?I<J?FC; F=  ;8J?<; C@E< 8E; @KJ I8E>< F= F9J<IM<; M8CL<J J?8;<; 8I<8 ,@>?K KFG 8M<I
8>< JF@C 01 =FI K?< <EK@I< GIF^C<  KF  :D =FI K?< @II@>8K<; 9CL< C@E< 8E; EFE @II@>8K<; I<; C@E< GCFKJ ,@>?K 9FKKFD ;8@CP GI<:@G@K8K@FE
Fig. A.1. (LD9<I F= ?FLIJ G<I ;8P LE;<I JKI<JJ=LC :C@D8K@: :FE;@K@FEJ =FI :8:8F KI<<J 8::FI;@E> KF M8CL<J I<GFIK<; @E &8?@M< <K 8C )>LEKLE;< 
'<@EQ<I !)'- <K 8C  8E; 8PDFE; 8E; "8;C<P  <8:? 98I @J FE< ;8P .FG 8@I ?LD@;@KP 9<CFN  D@;;C< K<DG<I8KLI< 89FM< G?FKFJPE
K?<K@: FGK@DLD K?I<J?FC;   9FKKFD K<DG<I8KLI< 9<CFN K?< 98J< K<DG<I8KLI< =FI M<><K8K@M< >IFNK?  
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
3.2. Leaf area index (LAI)
)M<I8CC &# ;<:C@E<; JK<8;@CP K?IFL>?FLK K?< <OG<I@D<EK 9FK? @E
K?< @II@>8K<; 8E; @E K?< :FEKIFC GCFK .?IFL>?FLK <:<D9<I K?< &# I<
D8@E<; :FEJK8EK 8E; JK8IK<; KF ;<:I<8J< @E $8EL8IP @E 9FK? KI<8KD<EK
GCFKJ 8K K?< J8D< K@D< 8J K?< ELD9<I F= ;8PJ N@K? ,"   JK8IK<; KF
@E:I<8J<  @>J  8E;  #E <9IL8IP &# :FEK@EL<; KF ;<:I<8J<
=8JK<I @E K?< EFE@II@>8K<; :FEKIFC GCFK K?8E @E K?< @II@>8K<; FE< K K?<
<E; F= K?< JKL;P K?< <JK@D8K<; &# N8J  8K K?<
@II@>8K<; GCFK 8E;  8K K?< EFE@II@>8K<; GCFK :FD
G8I<; KF 8E <JK@D8K<;  @E K?< 9<>@EE@E> F= K?<
JKL;P =FI 9FK? KI<8KD<EKJ  @>  .?< &# K?LJ ;IFGG<; 9P 8GGIFO@
D8K<CP  @E K?< @II@>8K<; GCFK 8E; 9P 8GGIFO@D8K<CP  @E K?<
:FEKIFC ::FI;@E> KF K?< !'' =IFD D@; <9IL8IP FEN8I;J &# @E
K?< @II@>8K<; GCFK N8J J@>E@=@:8EKCP ?@>?<I K?8E @E K?< :FEKIFC GCFK
@> 
.?< KFK8C C@KK<I :FCC<:K<; K?IFL>?FLK K?< <EK@I< <OG<I@D<EK N8J
>I<8K<I @E K?< :FEKIFC   K?8E @E K?< @II@>8K<; 
 KI<8KD<EK 'FJK F= K?< J?<;;@E> 8GG<8IJ KF ?8M< F::LII<;
@E C8K< <:<D9<I =FI 9FK? KI<8KD<EKJ N?@C< @E '8I:? N@K? K?< I<JLDG
K@FE F= I8@E K?< C@KK<I=8CC N<EK KF Q<IF  @>  .?< 8M<I8>< C@KK<I=8CC
N8J CFN<I @E K?< @II@>8K<; GCFK EFK89CP @E K?< ^IJK N<<B F= $8EL8IP
@>  N?<E 8@I ?LD@;@KP ;IFGG<; 9<CFN  =FI K?< ^IJK K@D<
@>  .?@J @J @E 8>I<<D<EK N@K? K?< I<JLCKJ F= &# ;PE8D@: K?8K <M@
;<E:<; 8 ;@==<I<E:< @E &# 9<KN<<E GCFKJ 8K K?< <E; F= K?< J<8JFE I<JLCK
@E> =IFD 8 JK<8;@CP C8I><I =FC@8>< CFJJ @E K?< EFE@II@>8K<; GCFK  @>J
8E; 
3.3. Sub-daily patterns of sap velocity in response to climatic drivers
@> J?FNJ K?< I<JGFEJ< F= J8G M<CF:@KP KF 0* LE;<I ;@==<I<EK
C<M<CJ F= *, 89FM< K?< :8EFGP @E K?< KNF KI<8KD<EKJ K CFN 0* M8C
Fig. 3. &<8= 8I<8 @E;<O &#  @E K?< KNF N8K<I@E> KI<8KD<EKJ @II@>8K<; 9CL< 8E; :FEKIFC I<; K?IFL>?FLK K?< F9J<IM<; ;IP J<8JFE .?<
C@E<J I<GI<J<EK K?< K?I<< ;8PDFM@E> 8M<I8><J F= K?< &# K@D<J J<I@<J FOGCFKJ I<GI<J<EK K?< M8I@89@C@KP 9<KN<<E K?< K?I<< J<EJFIJ @E <8:? GCFK =FI <M<IP ;8K<
Fig. B.1. @==<I<E:< @E <JK@D8K<; C<8= 8I<8 @E;<O &# 9<KN<<E K?< @II@>8K<; 8E; K?< :FEKIFC GCFK .?< ^KK<; C@E< @J 8 ><E<I8C@Q<; 8;;@K@M< DF;<C 8E; K?< J?8;<; 8I<8
@J K?<  GI<;@:K@FE @EK<IM8C  J?8;<; 8I<8 EFEFM<IC8GG@E> N@K? K?< Q<IFC@E< @E;@:8K<J 8 J@>E@=@:8EK ;@==<I<E:< 9<KN<<E N8K<I@E> KI<8KD<EKJ
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
Fig. B.2. &@KK<I GIF;L:K@FE F= :8:8F KI<<J ;LI@E> K?< ;IP "8ID8KK8E J<8JFE @E GI<J<E:< 9CL< 8E; 89J<E:< I<; F= @II@>8K@FE FOGCFKJ I<GI<J<EK M8I@8K@FEJ 9<
KN<<E K?< =FLI C@KK<I KI8GJ G<I KI<8KD<EK 8E; ;8K< FC; C@E<J I<GI<J<EK D<8EJ G<I GCFK 8E; ;8K<
Fig. 4. -L9;8@CP ;8PK@D< D<8JLI<D<EKJ F= :8:8F KI<<J J8G M<CF:@KP @E I<JGFEJ< KF M8IP@E> 0* @E K?< @II@>8K<; GCFK C<=K 8E; @E K?< :FEKIFC GCFK I@>?K ;LI@E> K?<
;IP "8ID8KK8E J<8JFE -PD9FC :FCFLIJ ;<G@:K *, C<M<CJ D<8JLI<; 89FM< K?< :8EFGP @E 
L<J   KI<<J @E K?< :FEKIFC GCFK J<<D KF ?8M< KI8EJG@I<; DFI<
K?8E K?FJ< @E K?< @II@>8K<; GCFK /E;<I ?@>? 0*    D<8JLI<
?@>? ;@JG<IJ@FE I<>8I;C<JJ F= K?< *, C<M<C /E;<I @EK<ID<;@8K< 0*
  J8G M<CF:@KP 8GG<8I<; KF I<JGFE; DFI< KF *, @E KI<<J =IFD
K?< @II@>8K<; GCFK @> J?FNJ K?< 8M<I8>< ;8@CP :P:C< F= J8G M<CF:@KP
;LI@E> K?<  DFJK 8E; C<8JK JKI<JJ@E> ;8PJ FM<I K?< JKL;P G<I@F;
-8G M<CF:@KP 8K CFN 0* =FCCFN<; K?< J8D< :P:C< @E K?< KNF GCFKJ N@K?
FLK J@>E@=@:8EK ;@==<I<E:<J <O:<GK @E K?< <8ICP DFIE@E> N?<E K?< :FE
KIFC KI<<J KI8EJG@I<; J@>E@=@:8EKCP DFI< K?8E K?< @II@>8K<; FE<J  @>
 #E ;8PJ N?<E 0* N8J ?@>? K?< 8M<I8>< J8G M<CF:@KP G<8B<;
8IFLE;  :D? =FI 9FK? KI<8KD<EKJ 9LK K?< @II@>8K<; GCFK GI<J<EK<;
FE 8M<I8>< 8 J8G M<CF:@KP ?@>?<I K?8E K?< :FEKIFC ;LI@E> K?< C8K< DFIE
@E>J N?@C< K?< :FEKIFC K<E;<; KF D8@EK8@E 8 ?@>?<I J8G M<CF:@KP @E K?<
C8K< 8=K<IEFFE  @>  #E K?< DFIE@E> K?< :FEKIFC GI<J<EK<; 8 G<8B
@E J8G M<CF:@KP 8IFLE;  8D  :D? I<>8I;C<JJ F= K?< C<M<C F= 0*
E <8ICP DFIE@E> G<8B @E J8G M<CF:@KP N8J 8CJF =FLE; =FI K?< @II@>8K<;
GCFK @E ;8PJ N?<E 0* N8J ?@>? FK? @>J 8E; ?@EK<; KF JFD< 9<
K?< JKL;P N@K? K?< KNF ,. DF;<CJ
.?< D8@E ;I@M<IJ F= ?8C=?FLICP M8I@8K@FEJ @E J8G M<CF:@KP ;LI@E> K?<
;8P N<I< @;<EK@^<; 9P D<8EJ F= 8 ,. DF;<C DF;<C   @>  .?<
DF;<C 8M<IK<; FM<I^KK@E> 8E; N8J :FEJ@;<I<; KF 9< JK89C< KI8@E@E>
;8K8 :FII<C8K@FE   :IFJJM8C@;8K@FE :FII<C8K@FE :F<=^:@<EK 
  I<>I<JJ@FE 8E8CPJ@J F= GI<;@:K<; 8>8@EJK D<8JLI<; M8CL<J =FI
K?< K<JK ;8K8 J<K J?FN<; K?8K DF;<C  8K CFN M8CL<J LG KF  
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
Fig. 5. -8G M<CF:@KP 8M<I8>< ;8@CP :P:C< =FI :8:8F KI<<J LE;<I ?@>?  8E; CFN  0* :FE;@K@FEJ .?< ;8J?<; C@E< I<GI<J<EKJ K?< 8M<I8>< 0* :P:C< .?< 8M<I8>< :P
:C<J =FI J8G M<CF:@KP 8E; 0* N<I< F9K8@E<; LJ@E> K?< ;8K8 =IFD K?<  DFJK 8E; C<8JK JKI<JJ@E> ;8PJ F= K?< ;IP "8ID8KK8E J<8JFE  .?< J?8;@E>J ;<G@:K
K?< K?<  :FE^;<E:< @EK<IM8C
Fig. 6. )M<IM@<N F= ;8PK@D< J8G M<CF:@KP I<JGFEJ< KF K?< D8@E <EM@IFED<EK8C ;I@M<IJ 8J @;<EK@^<; N@K? 8 ,. DF;<C DF;<C  .?< I<JGFEJ<J 8I< :8C:LC8K<; FE ?8C=
?FLICP ;8K8 ;LI@E> K?< <EK@I< G<I@F; F= K?@J JKL;P LE:K@FE8C J?8G<J F= K?< I<JGFEJ< F= J8G M<CF:@KP KF K?< <EM@IFED<EK8C M8I@89C<J "FLI 0* *, -F@C 01 &#
8E; KI<< ;@8D<K<I *, 8E; 0* N<I< <OGI<JJ<; 8J M8I@8K@FEJ =IFD K?< I<JG<:K@M< ;8PK@D< :P:C< 8:? M8I@89C< N8J GI<J<EK<; N@K? K?< I<C8K@M< N<@>?K F= @KJ M8I@8K@FE
@E K?8K F= J8G M<CF:@KP N@K?@E G8I<EK?<J<J .?< I<; ;FKK<; C@E<J I<GI<J<EK K?< &)-- JDFFK?@E> =FI <8:? I<JGFEJ< =LE:K@FE
JC@>?KCP FM<I<JK@D8K<; ?8C=?FLICP J8G M<CF:@KP FK?<IN@J< @K LE;<I<JK@
D8K<; J8G M<CF:@KP  @>  .?< =@KK<; =LE:K@FE@E @> I<GI<J<EKJ
K?< G8IK@8C ;<G<E;<E:P F= J8G M<CF:@KP KF K?< ;@==<I<EK M8I@89C<J 8E; @K @J
F9K8@E<; 9P 8M<I8>@E> FLK K?< <==<:KJ F= 8CC K?< M8I@89C<J @E K?< DF;<C
<O:<GK FE< 8E; K?<E GCFK K?< 8M<I8>< ^KK<; M8CL< N@K? I<JG<:K KF K?<
FE< M8I@89C< C<=K LIK?<IDFI< @K N8J :?FJ<E KF GCFK 8 JDFFK?@E> F= K?<
,. =LE:K@FEJ LJ@E> 8 &)-- JDFFK?@E>  K?< JDFFK?<; =LE:K@FEJ 8I<
J?FNE @E I<;  @>  )E:< K?< <==<:K F= K?< ;8@CP :P:C< "FLI N?@:?
?8J 8 I<C8K@M< @E_L<E:< F=  @E <OGC8@E@E> J8G M<CF:@KP N8J I<
DFM<; K?< GI<M8C<EK <EM@IFED<EK8C M8I@89C<J <OGC8@E@E> K?< M8I@89@C
@KP @E J8G M<CF:@KP N<I< *, 89FM< K?< :8EFGP  8E; 0*
 =FCCFN<; 9P JF@C 01  .?< <MFCLK@FE F= &# FM<I K?<
J<8JFE @E K?< KNF GCFKJ <OGC8@E<;  F= K?< M8I@89@C@KP N?@C< KI<< ;@
8D<K<I GIFOP =FI K?< ;@==<I<EK KI<<J 8::FLEK<; =FI  F= K?< KFK8C
-8G M<CF:@KP I<JGFE;<; C@E<8ICP KF K?< M8I@8K@FEJ F= 0* 8IFLE; @KJ
D<8E ;8@CP :P:C<  0* LG KF   <PFE; K?@J GF@EK K?< ,. DF;<C
JL>><JKJ 8E @E:I<8J< @E K?< JCFG< F= K?@J I<C8K@FEJ?@G .?< M8I@89@C@KP @E
*, 89FM< K?< :8EFGP N8J 8 B<P ;I@M<I F= J8G M<CF:@KP 1?<E *, N8J
89FM<8M<I8>< :FDG8I<; KF @KJ D<8E ;8@CP :P:C<  *,  J8G M<CF:
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
Fig. C.1. )9J<IM<; 89J:@JJ8 MJ GI<;@:K<; FI;@E8K<J J8G M<CF:@KP K?< :FII<JGFE;@E> C@E<8I I<>I<JJ@FE ;8J?<; C@E< 8E; PO C@E< =LCC 9C8:B C@E< =FI K?< ,. ?8C=
?FLICP DF;<C DF;<C  K<JK ;8K8
@KP @E:I<8J<; N@K? *, @E 8 C@E<8I =8J?@FE FI 9<CFN8M<I8>< *,
*,  J8G M<CF:@KP I<D8@E<; I<C8K@M<CP JK89C< LEK@C *, I<8:?<; 
  <PFE; K?@J GF@EK K?< I<JGFEJ< F= J8G _FN KF *,
;<:C@E<; 8E; K?<E JK89@C@Q<; -8G M<CF:@KP @E:I<8J<; N@K? JF@C 01 LG
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JGFEJ< F= J8G M<CF:@KP _8KK<E<; FLK LEK@C ^<C; :8G8:@KP 
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J8G M<CF:@KP 8E; N<I< E<>C@>@9C< ;I@M<IJ F= J8G M<CF:@KP 8K K?< JL9;8@CP
#E K?< JL9;8@CP DF;<C K?< @EK<I8:K@FEJ 9<KN<<E 0* 8E; *, 8E;
0* 8E; &# N<I< DFI< @DGFIK8EK K?8E K?< FK?<I @EK<I8:K@FEJ .89 
N?@:? D<8EJ K?8K 0* DF;@^<; K?< J8G M<CF:@KP I<JGFEJ< KF 9FK? &#
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8M<I8>< ;8@CP :P:C< J8G M<CF:@KP N8J M<IP CFN  @>  1?<E 0* N8J
?@>? K?< J8G M<CF:@KP N8J M<IP ?@>? =FI 8EP M8CL< F= *, -@D@C8ICP
N?<E *, N8J ?@>? J8G M<CF:@KP N8J ?@>? 8E; JK89C< N?8K<M<I K?<
M8CL< F= 0* <O:<GK N?<E 0* N8J M<IP ?@>? N?<I< J8G M<CF:@KP N8J
M<IP ?@>? 1?<E 0* 8E; &# N<I< CFN K?< J8G _FN N8J 8CJF M<IP CFN
@>  1?<E 0* N8J CFN K?< J8G M<CF:@KP I<D8@E<; CFN N?8K<M<I
K?< M8CL< F= &# 1?<E &# N8J CFN   J8G M<CF:@KP @E:I<8J<; N@K?
K?< 0* 8EFD8CP N@K? K?< J8D< <MFCLK@FE 8E; I<8:?<; J@D@C8I ?@>? M8C
L<J =FI GFJ@K@M< 0* 8EFD8C@<J LK N?<E 9FK? &# 8E; 0* N<I< ?@>?
&#  0* 8EFD8CP  K?< I<JGFEJ< F= J8G M<CF:@KP N8J :?8I8:
K<I@Q<; 9P 8 JK<<G<I JCFG< @E;@:8K@E> 8 GFJJ@9C< GFJ@K@M< JPE<I>@JK@: <=
=<:K FE J8G M<CF:@KP 9<KN<<E 0* 8E; &# .?@J JPE<I>P D<8EK K?8K K?<
GFJ@K@M< I<JGFEJ< F= J8G M<CF:@KP KF GFJ@K@M< 0* 8EFD8C@<J  @>  N8J
8DGC@^<; 9P K?< :8EFGP ;<EJ@KP N?<E &# N8J 89FM<   @>  #= K?<
&# 8CFE< N8J EFK 89C< KF J<EJ@9CP :?8E>< K?< J8G M<CF:@KP  @>  8K
?@>? M8CL<J &#  @KJ @DGFIK8E:< N8J @E_8K<; 9P GFJ@K@M< 0*
8EFD8C@<J  @>  /CK@D8K<CP K?< J8G M<CF:@KP F= KI<<J N@K? 8E &#
89FM<  LE;<I 8 JKIFE><I GLCC@E> =FI:< =IFD K?< 8KDFJG?<I< GFJ@K@M<
0* 8EFD8C@<J I<JLCK<; KF 9< ?@>?<I K?8E K?< J@E>C< I<JGFEJ<J KF <8:?
K<I8:K@FE 9<KN<<E 0* 8E; JF@C 01 N8J EFK =FLE; JKIFE> <EFL>? KF
9< :FEJ@;<I<; I<C<M8EK 8::FI;@E> KF DF;<C  .89 
Fig. 7. .?I<<;@D<EJ@FE8C G8IK@8C ;<G<E;<E:< GCFKJ =FI K?< @EK<I8:K@FE 9<
KN<<E 0*   8E; *,   M8I@8K@FEJ =IFD K?< D<8E
;8@CP :P:C< @E K?< ,. DF;<C  =FI ?8C=?FLICP J8G M<CF:@KP   @E :8:8F
KI<<J CC M8I@89C<J <O:<GK K?FJ< GCFKK<; 8I< ?<C; :FEJK8EK 8K K?<@I D<8E M8CL<J
3.4. Daily variations of sap velocity in response to climatic drivers
.?< ,. DF;<C 98J<; FE K?< ;8@CP 8M<I8><J F= J8G _FN M<CF:@KP I<E
;<I<; 8 JKIFE> KI8@E@E> ;8K8 :FII<C8K@FE  8 >FF; :IFJJM8C@;8K@FE
:FII<C8K@FE  .?LJ K?< DF;<C N8J =FLE; KF 9< JK89C< 8E; I<C@
89C< E <M8CL8K@FE F= GI<;@:K<; 8>8@EJK D<8JLI<; M8CL<J FE K?< K<JK
;8K8 J?FN<; K?8K DF;<C  GI<;@:K<; N<CC J8G M<CF:@KP ;<JG@K< 8 JC@>?K
LE;<I<JK@D8K@FE 8K ?@>? ;8@CP 8M<I8>< J8G M<CF:@K@<J 89FM< 
@>  LIK?<IDFI< N?<E J:8C@E> LG =IFD K?< ?8C=?FLICP KF K?<
;8@CP 8E8CPJ@J K?< N<@>?K F= K?< GI<;@:KFIJ FE J8G M<CF:@KP :?8E><;
@>  .?< M8I@89@C@KP @E ;8@CP J8G M<CF:@KP N8J DFJKCP <OGC8@E<; 9P
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
Fig. 8. .?I<<;@D<EJ@FE8C G8IK@8C ;<G<E;<E:< GCFKJ =FI K?< @EK<I8:K@FE 9<
KN<<E &#   8E; 0*   M8I@8K@FE =IFD K?< D<8E
;8@CP :P:C< @E K?< ,. DF;<C  =FI ?8C=?FLICP J8G M<CF:@KP   @E :8:8F
KI<<J CC M8I@89C<J <O:<GK K?FJ< GCFKK<; 8I< ?<C; :FEJK8EK 8K K?<@I D<8E M8CL<J
&#  8E; JF@C 01  .?< I<C8K@M< @DGFIK8E:< F= I8;@8
K@FE *, 8E; 0* ;<:I<8J<; KF  8E;  I<JG<:K@M<CP 
F= K?< M8I@89@C@KP @E J8G M<CF:@KP N8J <OGC8@E<; 9P M8I@8K@FEJ @E KILEB ;@
.?< J?8G< F= K?< I<JGFEJ< :LIM<J F= ;8@CP J8G M<CF:@KP KF K?< :FEJ@;
<I<; M8I@89C<J N8J ;@==<I<EK KF K?8K F9J<IM<; =FI ?8C=?FLICP M8CL<J
@>   -8G M<CF:@KP @E:I<8J<; E<8ICP C@E<8ICP N@K? &# 89FM< 
 -8G M<CF:@KP N8J @EJ<EJ@K@M< KF &# =FI M8CL<J 9<
KN<<E 8E;   <CFN  8E;
;FNE KF  D@E@DLD M8CL< D<8JLI<; @E FLI
JKL;P J8G _FN M<CF:@KP 8CJF I<JGFE;<; KF :?8E><J @E &# @E:I<8J@E> 8J
&# N8J CFN<I -8G _FN M<CF:@KP @E:I<8J<; C@E<8ICP N@K? JF@C 01 LEK@C
8 K?I<J?FC; C<M<C F=  8GGIFO@D8K<CP  =FI FLI
JF@C G8JK N?@:? @K GC8K<8L<; .?< J?8G< F= K?< I<JGFEJ< :LIM< F= J8G M<
CF:@KP KF D<8E ;8@CP *, N8J 8CDFJK C@E<8I @E K?< I8E>< =IFD  KF 
 <PFE; K?@J M8CL< K?< I<JGFEJ< F= J8G M<CF:@KP :8G
KLI<; 9P K?< ,. DF;<C C<8E<; FE =<N GF@EKJ K?LJ N8J EFK :FEJ@;<I<;
I<C@89C< @E8CCP K?< D<8E ;8@CP J8G M<CF:@KP @E:I<8J<; C@E<8ICP N@K?
;8@CP 8M<I8>< 0* @E 8 J@D@C8I =8J?@FE KF K?8K F9J<IM<; @E K?< ?8C=
?FLICP DF;<C   @>J 8E; 
 J@>E@=@:8EK @EK<I8:K@FE N8J =FLE; 9<KN<<E &# 8E; JF@C 01 8E;
KF 8 C<JJ<I <OK<EK 9<KN<<E 0* 8E; *, .89  1?<E &# N8J CFN
J8G M<CF:@KP @E:I<8J<; JC@>?KCP N@K? JF@C 01  @>  LK N?<E &#
I<8:?<; K?< M8CL< F=   K?< @E:I<8J< N@K? JF@C 01 9<:8D<
DL:? DFI< @DGFIK8EK 8E; J8G M<CF:@KP I<8:?<; M<IP ?@>? M8CL<J .?<
@EK<I8:K@FE 9<KN<<E 8M<I8>< ;8@CP 0* 8E; *, 8CK?FL>? C<JJ GIF
EFLE:<; J?FN<; K?8K K?< @E:I<8J< @E 0* 8E; *, D8P ?8M< 8 JPE<I
>@JK@: <==<:K FE J8G M<CF:@KP  @>  J *, @E:I<8J<; LG KF 
 J8G M<CF:@KP I<JGFE;<; DFI< I<8;@CP KF ;8@CP 8M<I8><
0* 8E; M@:< M<IJ8 <N *, M8CL<J N<I< I<:FI;<; 89FM< 
8E; K?< 8GG8I<EK ;<:I<8J< @E J8G M<CF:@KP 8=K<I K?@J
M8CL< N8J EFK @EK<IGI<K89C< K K?< FE<;8P K@D< J:8C< EF @EK<I8:K@FE
9<KN<<E D<8E JF@C 01 8E; 0* N8J ;<K<:K<; 9P DF;<C  .89 
J@D@C8ICP KF N?8K N8J =FLE; 8K K?< JL9;8@CP K@D<J:8C< .89 
4. Discussion
4.1. Climate
.?< D<8JLI<; :C@D8K< F= K?<  ;IP J<8JFE  @>  N8J I<G
I<J<EK8K@M< =FI K?< :FE;@K@FEJ <OG<I@<E:<; 9P :8:8F ;LI@E> K?@J K@D< F=
K?< P<8I @E K?< 8JK<IE I<>@FE F= !?8E8 J JF@C 01 8GGIF8:?<; K?<
N@CK@E> GF@EK @E K?< :FEKIFC GCFK 8@I ?LD@;@KP ;IFGG<; <M<E 9<CFN 
8E; K<DG<I8KLI<J N<I< JL9FGK@D8C  @>J 8E;  FE 8 ;8@CP 98J@J
K?< D<8JLI<; :FE;@K@FEJ N<I< =FLE; KF 9< JKI<JJ=LC 8::FI;@E> KF K?< ;<=
@E@K@FEJ >@M<E =FI JF@C 8E; 8KDFJG?<I@: JKI<JJ<J J<< -<:K@FE 
Fig. C.2. )9J<IM<; 89J:@JJ8 MJ GI<;@:K<; FI;@E8K<J J8G M<CF:@KP K?< :FII<JGFE;@E> C@E<8I I<>I<JJ@FE ;8J?<; C@E< 8E; PO C@E< =LCC 9C8:B C@E< =FI K?< ,. ;8@CP
DF;<C DF;<C  K<JK ;8K8
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
Fig. 9. )M<IM@<N F= 8:8FJ ;8@CP J8G M<CF:@KP I<JGFEJ< KF K?< D8@E <EM@IFED<EK8C ;I@M<IJ 8::FI;@E> KF 8 ,. DF;<C DF;<C  .?< I<JGFEJ<J 8I< :8C:LC8K<; =FI
;8@CP 8M<I8><J ;LI@E> K?< <EK@I< G<I@F; F= K?@J JKL;P LE:K@FE8C J?8G<J F= K?< I<JGFEJ< F= J8G M<CF:@KP KF K?< <EM@IFED<EK8C M8I@89C<J 0* *, -F@C 01 &# 8E;
KI<< ;@8D<K<I 8:? M8I@89C< @J GI<J<EK<; N@K? K?< I<C8K@M< @DGFIK8E:< F= @KJ M8I@8K@FE FE K?8K F= J8G M<CF:@KP N@K?@E G8I<EK?<J<J.?< I<; ;FKK<; C@E<J I<GI<J<EK K?<
&)-- JDFFK?@E> =FI <8:? I<JGFEJ< =LE:K@FE
Table 2
#EK<I8:K@FEJ 9<KN<<E K?< M8I@89C<J :FEJ@;<I<; @E K?< ,. 'F;<C  @E <OGC8@E
@E> :8:8F J8G M<CF:@KP 8K 8 JL9;8@CP K@D<J:8C< FI <8:? G8@I F= M8I@89C<J K?<
K89C< I<GFIKJ K?< D<8E M8CL< F= K?< I<J@;L8CJ N?@:? I<GI<J<EKJ K?< JKI<E>K? F=
K?< @EK<I8:K@FE #E 9FC; K?< @EK<I8:K@FEJ :FEJ@;<I<; JKIFE> K?LJ J@>E@=@:8EK
9P K?< DF;<C
*,79FM< &# -F@C701 0* @8D<K<I
*,79FM<   5507.51 
&# 19350.06  
-F@C701  
0*   
@8D<K<I 
Fig. 10. .?I<<;@D<EJ@FE8C G8IK@8C ;<G<E;<E:< GCFKJ =FI K?< @EK<I8:K@FE 9<
KN<<E JF@C 01   8E; &#   @E K?< ,. DF;<C
 =FI ;8@CP 8M<I8>< J8G M<CF:@KP   @E :8:8F KI<<J CC M8I@89C<J <O:<GK
K?FJ< GCFKK<; 8I< ?<C; :FEJK8EK 8K K?<@I D<8E M8CL<J
Fig. 11. .?I<<;@D<EJ@FE8C G8IK@8C ;<G<E;<E:< GCFKJ =FI K?< @EK<I8:K@FE 9<
KN<<E *,   8E; 0*   @E K?< ,. DF;<C  =FI ;8@CP 8M
<I8>< J8G M<CF:@KP   @E :8:8F KI<<J CC M8I@89C<J <O:<GK K?FJ< GCFKK<;
8I< ?<C; :FEJK8EK 8K K?<@I D<8E M8CL<J
4.2. Canopy
<JG@K< K?< F::LII<E:< F= ?@>? K<DG<I8KLI<J K?< KI<<J N<I< 89C< KF
:FG< N@K? K?< :C@D8K< @E <:<D9<I 1< 8I>L< JF 9<:8LJ< N< ;@; EFK F9
J<IM< 8EP ;<:C@E< @E &# @E <@K?<I N8K<I@E> KI<8KD<EK @E C@E< N@K? GI<M@
FLJ JKL;@<J N@K? EF 8KDFJG?<I@: JKI<JJ '@P8A@ <K 8C  'FJ<I <K 8C
 &<8= J?<;;@E> @J 8 :FDDFE I<JGFEJ< KF ;IFL>?K F= KIFG@:8C 8E;
JL9KIFG@:8C JG<:@<J L::@ <K 8C  C-?8IB8NP  8J @K 8CCFNJ
KI<<J KF I<;L:< KI8EJG@I8K@FE I8K<J 8E; ?<E:< 8MF@; ?P;I8LC@: =8@CLI<
#E C@E< N@K? K?< @;<8 K?8K :8:8F KI<<J 8GGCP K?@J ;IFL>?K:FG@E> JKI8K<>P
;LI@E> K?< DFI< J<M<I< G8IK F= K?< ;IP J<8JFE =IFD $8EL8IP FEN8I;J
&# ;<:I<8J<; @E 9FK? N8K<I@E> KI<8KD<EKJ 8CK?FL>? 8K 8 =8JK<I I8K< @E
K?< :FEKIFC GCFK  @>  JLGGFIK@E> K?< @;<8 K?8K C<8= J?<;;@E> ?<CGJ :8
:8F KF :FG< N@K? JF@C ;IFL>?K "FN<M<I >@M<E K?8K &# 8CJF ;<:I<8J<;
P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
@E K?< @II@>8K<; GCFK K?IFL>?FLK K?< <OG<I@D<EK8C G<I@F; @K @J C@B<CP K?8K
KI<<J @E K?< @II@>8K<; GCFK 8CJF JL==<I<; =IFD N8K<I JKI<JJ #K :FLC; 9< 8I
>L<; K?8K K?< @II@>8K@FE C<M<C  &KI<< FE 8CK<IE8K< ;8PJ <HL@M8C<EK KF
>8K< JF@C ;IFL>?K  @>  ;<JG@K< 9<@E> @E C@E< N@K? K?< N8K<I I<HL@I<
D<EK F= 8 D8KLI< KI<< =FLE; @E C@K<I8KLI< 8II 8E; &F:BNFF; 
CK<IE8K@M<CP @K :8E 9< @EK<IGI<K<; 8J K?< 8KDFJG?<I@: ;IFL>?K ?8M
@E> :FEKI@9LK<; KF C<8= J?<;;@E> .?@J C8KK<I @EK<IGI<K8K@FE @J JLGGFIK<;
9P K?< DFI< 89LE;8EK C@KK<I GIF;L:K@FE F9J<IM<; @E <:<D9<I N?<E
K?< JF@C 01 N8J J@>E@=@:8EKCP ?@>?<I @E K?< @II@>8K<; GCFK K?8E @E K?<
:FEKIFC 9LK 8@I ?LD@;@KP 8E; K<DG<I8KLI< I<8:?<; M8CL<J 89FM< JKI<JJ
=LC K?I<J?FC;J  @>J  8E;  .?< K@D@E> F= K?< ;IFG @E &# JL>
><JKJ K?8K K?< B<P 8KDFJG?<I@: :FE;@K@FE @DG8:K@E> K?< :8EFGP N8J K?<
<OKI<D<CP CFN 8@I ?LD@;@KP KF N?@:? :8:8F C<8M<J D@>?K EFK 9<
8;8GK<; <JG<:@8CCP :FEJ@;<I@E> K?8K :8:8F ;<M<CFG<; LE;<I M<IP ?@>?
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P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
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5. Conclusions
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F= :8:8F 8E; FK?<I JG<:@<J
Declaration of Competing Interest
.?< 8LK?FIJ ;<:C8I< K?8K K?<P ?8M< EF BEFNE :FDG<K@E> ^E8E:@8C
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P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
Appendix A. Atmospheric stressors
Appendix B. Leaf area index
Appendix C. Boosted Regression Trees analysis
C1. parameterization of the models
C2. Evaluation of BRT models on the test data
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P.D. Sala et al. Agricultural and Forest Meteorology xxx (xxxx) 108670
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... The results show that, with the exception of the Coastal zone where an 86% rise in RR is commensurate with a 14% rise in SM, the Savannah and Forest zones show signi cantly low SM responses to RR, while the Transition zone shows a slight negative SM response of 0.01-99% increment in RR by the start of the season. The slightly negative and low responses for the stations in the Transitional, Savannah, and Forest zones respectively, may be attributed to SM de cits as a result of the high atmospheric evaporative power during the dry Harmattan season which commensurate with the boreal winter which climatologically extends from late November through to February [40][41][42] . ...
... The Harmattan season is characterized by low RR and intense atmospheric dryness along with strong dusty north-easterly winds developed from a continental scale pressure difference between the subtropical subsidence zone and the ITCZ, looming southward and lingering along the Gulf of Guinea [42] . ...
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The interplay of soil moisture (SM) and rainfall (RR) has practical importance for pluvial flood prevention and prediction, drought monitoring, and weather forecasting for agricultural applications. Recent satellite products have shown complicated SM - RR relationships over varied ecosystems, with a diverse range of positive to negative correlation indices. This study presents an assessment of the SM - RR interplay over contrasting tropical ecosystems across Ghana in the West Africa terrain, using RR gauge measurements and satellite-based root zone SM for 22 Synoptic stations spanning 30 years (1990–2019). Spatiotemporal distributions, percentage changes about onset dates, and statistical strength of correlations are presented and discussed. Findings show that, generally, SM decreases northward by a gradient of 0.01, showing weak to strong correlations of 0.38–0.82 ± 0.10 with RR countrywide, the highest is found for stations in the northern Savannah and Coastal Savannah zones, the weakest for stations in the Forest zone. Meanwhile, based on the RR onset dates, the Coastal zone exhibits the highest percentage change in SM, whereas the Forest, Transition, and Savannah zones exhibit low to slightly negative percentage changes. This has been attributed to SM deficits resulting from the dry Harmattan season before RR onset, strongly suggesting a respective delineation of Coastal and Savannah regions as flood and drought-prone zones. The results are in tandem with global-scale assessments, and present a theoretical framework to develop ecosystem water and pluvial flood management schemes over the sub-region.
... In cocoa, water use efficiency can vary greatly depending on the genotype and water conditions (Agudelo-Castañeda et al., 2018;Hebbar et al., 2020). Cocoa originates from a humid environment; therefore, it presents marked responses to water deficit, exhibiting a fast loss of leaf turgor, chlorosis, and chronic photoinhibition (Della Sala et al., 2021;Jegadeeswari and Kumar, 2019;Salazar et al., 2018). Although the rainfall regime in tropical regions where cocoa is grown is not considered a current threat, global climate change has projected significant changes in temperatures and rainfall regimes that can drastically affect these crops (Farooq et al., 2019;Hatfield and Dold, 2019). ...
Global climate changes include more intense and concentrated rainy seasons, al well as more severe and longer-lasting dry seasons. In this context, the benefits carried out within agroforestry systems (AFS) have played a significant role, especially for tropical crops such as cocoa. The present study evaluated the changes in photo-synthetic traits in cocoa and the physical, chemical, and microbiological soil properties in response to different shading tree species arrangements. Three cocoa genotypes (CCN51, TCS01, and TCS19) were cultivated under three AFS designs, differing in the accompanying shade tree species (Cariniana pyriformis, Tabebuia rosea, and Terminalia superba). No significant differences in CO 2 assimilation rates among the different cocoa genotypes were observed. However, TCS01 exhibited a 20% higher leaf water use efficiency (WUEl) than the TCS19 genotype , associated with decreased stomatal conductance. The designs combining C. pyriformis with CCN51 and TCS01, as well as the design associating CCN51 with T. rosea, exhibited significantly higher WUEl for cocoa plants as compared to the systems involving T. superba combined with TCS19. In addition, the cocoa genotype TCS01 exhibited the highest potential for carbon storage when combined with C. pyriformis, whereas TCS19 exhibited the lowest potential for this feature under the T. superba association. Soil's chemical, physical and biological properties were evaluated, and an orthoPLS-DA multivariate analysis was performed to contrast the differences between TCS01 associated with C. pyriformis (higher WUEl and C sequestration) with the combination of TCS19 with T. superba (lower WUEl and carbon sequestration). The results highlight the importance of soil acidity, and [Al], [Mn], and [Mg] concentrations for a better physiological performance exhibited by TCS01 under C. pyriformis AFS as compared to TCS19 under T. superba. Thus, the data obtained here suggest that species-genotype-dependent interactions in AFS-cocoa may determine soil characteristics, which may indirectly affect important physiological traits, such as leaf water use efficiency and long-term carbon storage of cocoa plants.
... The smaller drip discharge flux had greater vertical depth of soil wetted zone than the higher drip discharge flux (Elmaloglou and Diamantopoulos, 2010), explaining why the Q1P3 had 59% and 32% smaller soil matric potential than Q2P3 and Q3P3 at shallow soil depth (10-40 cm) and 56% and 20% higher than Q2P3 and Q3P3 at deep soil depth (70 cm), respectively (Figs. 3 and 5). With the same irrigation amount, the smaller drip discharge flux might cause soil water stress at shallow soil depth which was not favorable for crop growth and decreased water use efficiency (Shock et al., 2007;Della Sala et al., 2021). However the larger drip discharge flux might result in a wide and shallow wetted zone and even lead to surface runoff, especially for potato grown with raised bed (Li Table 2 Potato tuber number per plant from treatments of different soil wetted percentages (15%, P1; 25%, P2; 50%, P3; and 75%, P4) and drip discharge fluxes (Q1, 1.38 L/h; Q2, 2.0 L/h; and Q3, 3.0 L/h) in 2016 (5 plants sampled) and 2017 (30 plants sampled). ...
China has the largest potato (Solanum tuberosum L.) production, while the average potato tuber yield is still lower than the world level. In order to improve potato cultivation, field experiments were conducted at the Special Potato Experimental Station, China Agricultural University, Rizhao, Shandong Province in 2016 and 2017 to explore the effects of drip discharge fluxes (1.38 L/h, Q1; 2.0 L/h, Q2; and 3.0 L/h, Q3) and soil wetted percentages (15%, P1 only in 2016; 25%, P2; 50%, P3; and 75%, P4 only in 2017) on soil water distribution and potato growth under drip irrigation with film mulch. With the same soil wetted percentage, Q1 provide drier soil at shallow layer and wetter at deep layer than Q2 and Q3. With the same drip discharge flux, the average daily soil matric potential decreased and soil matric potential range increased with the soil wetted percentage increasing. For different drip discharge fluxes, Q2 and Q3 had 10.4% and 13.6% significantly greater IWUE than Q1 in 2017. For different soil wetted percentages, P3 had significantly 15.9% and 8.6% more marketable tubers, and 19.1% and 11.2% more large plus jumbo tubers than P1 and P2 in mass, respectively in 2017. P3 had 17.4% and 14.7% significantly greater yield than P2 and P4 in 2016 and 15.1% and 7.6% significantly greater than P1 and P2 in 2017, respectively. The IWUE decreased with the soil wetted percentage increasing. Drip discharge flux Q2 and soil wetted percentage P3 was a more favorable combination for potato growth in this area.
... Les résultats présentés dans cet article concernent spécifiquement les projections issues des dernières données CMIP6 (Coupled Model Intercomparison Project Phase 6) pour comprendre les principales évolutions attendues de certaines contraintes agroclimatiques thermo-pluviométriques à moyen et long terme. Ces précisions climatologiques à l'échelle régionale doivent permettre de raffiner et améliorer les diverses applications et modélisations des conditions agronomiques et hydrométéorologiques en Afrique (Nooni et al., 2021 ;Della Sala et al., 2021). L'ensemble de ce travail de recherche s'effectue dans le cadre d'un projet franco-ivoirien soutenu par la Région Auvergne-Rhône-Alpes (Pack Ambition International) intitulé « Evolution des agrosystèmes d'Abidjan à Aboisso et apports des services climatiques en Côte d'Ivoire : projections, résilience et aide à la décision », et associant notamment les Universités de Grenoble, Lyon, La Réunion, ainsi que celles de Félix Houphouet-Boigny et de Nangui-Abrogoua à Abidjan. ...
Conference Paper
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La Côte d'Ivoire est au coeur d'enjeux agro-écologiques et socio-économiques considérables, ses filières étant rendues très vulnérables par le changement climatique. Les analyses présentées s'appuient sur les simulations climatiques CMIP6 (et sur certains indicateurs provenant des données CMIP5) à l'échelle du sud-est du pays, représentatif de grandes plantations industrielles associées à un foncier villageois très dynamique. Les résultats indiquent qu'au-delà des hausses attendues des températures, ce sont surtout les séquences pluviométriques et leur évolution intrasaisonnière qui vont conditionner les tolérances des principales productions agricoles du Sud-Comoé, malgré certaines incertitudes des simulations numériques.
... Various genetic, ontogenic, morphogenetic, and environmental factors can influence the biosynthesis and accumulation of secondary metabolites. Cocoa production of secondary metabolites can be gradually generated in response to environmental stress, and hence plant secondary metabolism can be viewed as a plant behavior that is in part the ability of a plant to adapt and survive in response to environmental stimuli during its lifetime [27]. ...
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Fine flavor cocoa is a unique category of cocoa that produces almonds with high aromatic potential and several sensory benefits that make it different from the basic or ordinary cocoas. Ecuador is the world’s leader in the production and export of fine flavor cocoa, responsible for 63% of the world’s total production due to the commercialization of the Arriba Nacional variety, known to possess an intense aroma that is unique in the cocoa world market. Besides its organoleptic specificity, this variety represents a source of important bioactive compounds associated with both sensory and health properties. This study evaluates the influence of an abiotic factor, nutritional soil status, on the phytochemical composition (methylxantines and phenolic compounds), and antioxidant and sensory properties of Arriba variety cocoa beans originating from three different geographical regions of Ecuador. We used the Diagnosis and Recommendation Integrated System (DRIS), Folin–Ciocalteau, high-performance liquid chromatography (HPLC), ABTS free-radical-scavenging activity, the α, α-diphenyl-β-picrylhydrazyl free-radical-scavenging method (DPPH), and Ferric reducing antioxidant power (FRAP) analysis to reveal a significant correlation between Mn ions and total phenolic content, a positive implication of N in methylxanthine composition and antioxidant properties, and the importance of Ca, Mg, and K ions in increasing the flavonoid and anthocyanin content of raw cocoa beans. We showed that these nutritional elements can interfere with the nutraceutical and sensory properties of cocoa beans, as Cu, Mg, and K are correlated with anthocyaninic content, while Fe, Ca, P and Zn influenced the flavonoid content. We underline that the Arriba variety is suitable not only for the production of high-quality chocolate, but also for the increasing worldwide nutraceutical market, generating qualitative and competitive products.
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In this study, we measured diurnal patterns of sap flow (Vs) in cacao trees growing in three types of agroforestry systems (AFs) that differ in the incident solar radiation they receive. We modeled the relationship of Vs with several microclimatic characteristics of the AFs using mixed linear models. We characterized microclimatic variables that may have an effect on diurnal patterns of sap flow: air relative humidity, air temperature, photosynthetically active radiation and vapor pressure deficit. Overall, our model predicted the differences between cacao Vs in the three different AFs, with cacao plants with dense Musaceae plantation and high mean diurnal incident radiation (HPAR) displaying the highest differences compared to the other agroforestry arrangements. The model was also able to predict situations such as nocturnal transpiration in HPAR and inverse nocturnal sap flows indicative of hydraulic redistribution in the other AFs receiving less incident radiation. Overall, the model we present here can be a useful and cost-effective tool for predicting transpiration and water use in cacao trees, as well as for managing cacao agroforestry systems in the Amazon rainforest.
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Cocoa plantations in Brazil have been expanding beyond the borders of traditional regions by implementing a strategy based on irrigation and the establishment of crops exposed to full sunlight. The quantification of transpiration is essential to the establishment and management of crops, and is the main factor in the determination of water demand. This study had as its objective the estimating of transpiration of young cocoa trees as a function of reference evapotranspiration (ETo) and soil matric potential (Ψw). Two experiments were conducted, one in a greenhouse and the other in the field, using clones and seminal plants. Soil water content, plant transpiration and reference evapotranspiration were monitored. Cocoa trees were subjected to soil moisture reduction and their transpiration decreased linearly both in the field and in the greenhouse, due to decreases in the soil matric potential beyond a critical point. In the greenhouse average transpiration could be linearly estimated as a function of ETo when Ψw was higher than –24.89 kP. Drying soil conditions resulted in a reduction in transpiration by approximately a 2 % per unit decrease in Ψw. Under field conditions; clonal plant transpiration decreased linearly beyond the critical matric potential of –65.02 kPa, while in seminal plants this reduction occurred beyond –79.48 kPa. Clonal plants were more sensitive to soil water variations with average transpiration lower than that of seminal cocoa tree plants.
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Plants continue to lose water from their leaves even after complete stomatal closure. Although this minimum conductance (gleaf-res ) has substantial impacts on strategies of water use and conservation, little is known about the potential drivers underlying the variability of this trait across species. We thus untangled the relative contribution of water leaks from the cuticle and stomata in order to investigate how the variability in leaf morphological and anatomical traits is related to the variation in gleaf-res and carbon assimilation capacity across 30 diverse species from the Brazilian Cerrado. In addition to cuticle permeance, water leaks from stomata had a significant impact on gleaf-res . The differential patterns of stomata distribution in the epidermis was a key factor driving this variation, suggesting the existence of a trade-off between carbon assimilation and water loss through gleaf-res . For instance, higher gleaf-res , observed in fast-growing species, was associated with the investment in small and numerous stomata, which allowed higher carbon assimilation rates but also increased water leaks, with negative impacts on leaf survival under drought. Variation in cuticle structural properties was not linked to gleaf-res . Our results therefore suggest the existence of a trade-off between carbon assimilation efficiency and dehydration tolerance at foliar level.
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Sap flow, the movement of fluid in the xylem of plants, is commonly measured with the heat pulse velocity (Vh) family of methods. The observable range of Vh in plants is ~−10 to ~+270 cm/h. However, most Vh methods only measure a limited portion of this range, which restricts their utility. Previous research attempted to extend the range of Vh methods, yet these approaches were analytically intensive or impractical to implement. The Dual Method Approach (DMA), which is derived from the optimal measurement ranges of two Vh methods, the Tmax and the heat ratio method (HRM), also known as the “slow rates of flow” method (SRFM), is proposed to measure the full range of sap flow observable in plants. The DMA adopts an algorithm to dynamically choose the optimal Vh measurement via the Tmax or HRM/SRFM. The DMA was tested by measuring sap flux density (Js) on Tecoma capensis (Thunb.) Lindl., stems and comparing the results against Js measured gravimetrically. The DMA successfully measured the entire range of Vh observed in the experiment from 0.020 to 168.578 cm/h, whereas the HRM/SRFM range was between 0.020 and 45.063 cm/h, and the Tmax range was between 2.049 cm/h and 168.578 cm/h. A linear regression of DMA Js against gravimetric Js found an R2 of 0.918 and error of 1.2%, whereas the HRM had an R2 of 0.458 and an error of 49.1%, and the Tmax had an R2 of 0.826 and an error of 0.5%. Different methods to calculate sapwood thermal diffusivity (k) were also compared with the kVand method showing better accuracy. This study demonstrates that the DMA can measure the entire range of Vh in plants and improve the accuracy of sap flow measurements.
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Cacao (Theobroma cacao L.) is a tropical perennial crop which is of great economic importance to the confectionary industry and to the economies of many countries of the humid tropics where it is grown. Some recent studies have suggested that climate change could severely impact cacao production in West Africa. It is essential to incorporate our understanding of the physiology and genetic variation within cacao germplasm when discussing the implications of climate change on cacao productivity and developing strategies for climate resilience in cacao production. Here, we review the current research on the physiological responses of cacao to various climate factors. Our main findings are as follows: (1) water limitation causes significant yield reduction in cacao, but genotypic variation in sensitivity is evident; (2) in the field, cacao experiences higher temperatures than is often reported in the literature; (3) the complexity of the cacao/shade tree interaction can lead to contradictory results; (4) elevated CO2 may alleviate some negative effects of climate change; (5) implementation of mitigation strategies can help reduce environmental stress; and (6) significant gaps in the research need addressing to accelerate the development of climate resilience. Harnessing the significant genetic variation apparent within cacao germplasm is essential to develop modern varieties capable of high yields in non-optimal conditions. Mitigation strategies will also be essential, but to use shading to best effect shade tree selection is crucial to avoid resource competition. Cacao is often described as being sensitive to climate change, but genetic variation, adaptive responses, appropriate mitigation strategies and interactive climate effects should all be considered when predicting the future of cacao production. Incorporating these physiological responses to various environmental conditions and developing a deeper understanding of the processes underlying these responses will help to accelerate the development of a more resource use efficient tree ensuring sustainable production into the future.
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Cacao (Theobroma cacao L.) has traditionally been considered a crop that requires shade, and consequently it is implemented under agroforestry systems (AFs) in order to regulate the level of incident solar radiation. However, optimal shade levels for this tree crop may vary depending on the climate conditions of where it is grown. Here we analyzed the physiological performance of cacao under three different AFs in the Colombian Amazon that differed in solar radiation patterns: high (HPAR), medium (MPAR), or low (LPAR) mean daily incident radiation. The physiological performance was characterized using photosynthetic variables in leaves such as light- and CO2-response curves, chlorophyll a fluorescence parameters, and total chlorophyll and carotenoid contents, in conjunction with other leaf functional traits. Cacao trees exposed to HPAR showed an improved physiological performance as compared to those from the other two AFs. Compared to MPAR and LPAR, cacao trees in HPAR doubled the rate of net carbon assimilation and reached higher maximum rates of RuBisCO carboxylation and RuBP regeneration. Moreover, cacao trees in HPAR presented photoprotection mechanisms that avoided photoinhibition, which was accompanied by a greater non-photochemical quenching coefficient and biochemical and morphological adjustments (low chlorophyll but higher carotenoid contents and low specific leaf area) compared to cacao trees from the other AFs. Overall, our results show that, due to the high cloud cover in the Colombian Amazon, cacao plantations under conditions of sparse shade maximized their carbon use, showing an improved physiological performance as a result of higher photosynthetic rates and energy dissipation mechanisms. If the crop were managed with sparse shade, the paradigm that favors the cultivation of cacao under shade would be called into question in the Colombian Amazon and other regions with similar climatic conditions.
Improving management practices of cocoa (Theobroma cacao L.) cultivation especially under future climate change requires knowledge of yield gaps and their determining factors. In this study, we assessed yield gaps and their determining factors through multiple regression modelling in smallholder cocoa agroforestry systems in Ghana along a climatic gradient. The studied zones referred to as dry, mid and wet with annual rainfall of 1200, 1200-1400 and 1400-2000 mm respectively, represent established "climate suitability zones" across the cocoa belt of West Africa, where 70% of the global cocoa is produced. Data was collected from 150 cocoa farmers and their plantation across the zones. Information about socioeconomic and management characteristics was collected through interviews. In each plantation, soil characteristics and cocoa plantation properties were recorded. Yield data for three consecutive years (2012/13-2014/15) and soil properties (0-30 cm layer) were analysed. Yield gap was estimated as the difference between attainable yield (AY) and actual farmers yield (FY) in each zone based on the approach of maximum farmer yields determined from survey. Average farmer and attainable yield of 211 and 645 kg ha −1 year −1 in the dry, 477 and 1174 kg ha −1 year −1 in the mid and 999 and 2125 kg ha −1 year −1 in the wet zone were recorded, respectively. Relative yield gaps were significantly larger in the dry (67%) than the wet zone (53%). In the dry zone with significantly older farmers (average age of 64), increasing labour cost (use of hired labour) significantly reduced yield gap. Contrary, increasing labour cost significantly increased yield gap in the mid zone where plantations were significantly larger. Yield gap increased significantly with increasing farmer age (54 years) in the mid zone but decreased significantly with farmer age (47 years) in the wet zone. Significant positive relationship between plantation size and yield gap was observed in both mid and wet zones. Soil available phosphorous (P) and fungicide use significantly reduced yield gap in the dry and mid zones. Finally, quantity of pesticide, proportion of hybrid cocoa plants and number of trainings received by farmers significantly reduced yield gap in the wet zone. In the dry zone, closing the yield gap against https://doi.
Vapour pressure deficit (D) is projected to increase in the future as temperatures rise. In response to increased D, stomatal conductance (gs) and photosynthesis (A) are reduced, which may result in significant reductions in terrestrial carbon, water, and energy fluxes. It is thus important for gas exchange models to capture the observed responses of gs and A with increasing D. We tested a series of coupled A-gs models against leaf gas exchange measurements from the Cumberland Plain Woodland (Australia), where D regularly exceeds 2 kPa and can reach 8 kPa in summer. Two commonly used A-gs models (Leuning 1995 and Medlyn et al. 2011) were not able to capture the observed decrease in A and gs with increasing D at the leaf scale. To explain this decrease in A and gs, two alternative hypotheses were tested: hydraulic limitation (i.e., plants reduce gs and/or A due to insufficient water supply) and non-stomatal limitation (i.e., downregulation of photosynthetic capacity). We found that the model that incorporated a non-stomatal limitation captured the observations with high fidelity and required the fewest number of parameters. While the model incorporating hydraulic limitation captured the observed A and gs, it did so via a physical mechanism that is incorrect. We then incorporated a non-stomatal limitation into the stand model, MAESPA, to examine its impact on canopy transpiration and gross primary production. Accounting for a non-stomatal limitation reduced the predicted transpiration by ~19%, improving the correspondence with sap flow measurements, and gross primary production by ~14%. Given the projected global increases in D associated with future warming, these findings suggest that models may need to incorporate non-stomatal limitation to accurately simulate A and gs in the future with high D. Further data on non-stomatal limitation at high D should be a priority, in order to determine the generality of our results and develop a widely applicable model.