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The mal imaging a plan le el o assess he c op-wa e s a us in almond ees (c .
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Gua a) unde de ici i iga ion s a egies
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Ga cía-Teje o I.F.1*, Rubio, A.E2., Viñuela, I1., He nández, A1., Gu ié ez-Go dillo, S1., Rod íguez-Pleguezuelo, C.R.3,
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Du án-Zuazo V.H.3
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1 Ins i u o Andaluz de In es igación y Fo mación Ag a ia, Pesque a y de la P oducción Ecológica (IFAPA). Cen o “Las
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To es – Tomejil”. C a. Se illa-Cazalla Km. 12,2. 41.200. Alcalá del Río, Se illa, Spain.
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2 Facul ad de Biología. Depa amen o de Biología Vege al y Ecología. Uni e sidad de Se illa. A enida de Reina
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Me cedes s/n. 41012. Se illa, Spain.
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3 Ins i u o Andaluz de In es igación y Fo mación Ag a ia, Pesque a y de la P oducción Ecológica (IFAPA). Cen o
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“Camino de Pu chil”. Apdo. 2027, 18080, G anada, Spain
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*e-mail: i an .ga cia@jun adeandalucia.es
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Abs ac
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Almond (P unnus dulcis Mill.) has been adi ionally associa ed o ma ginal land cul i a ion and ain- ed
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ag icul u e in Sou h Spain. Howe e , in he las yea s, his c op is being p og essi ely in oduced in mo e
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p oduc i e ag icul u al a eas wi hin he Guadalqui i i e basin, whe e he a ailable wa e esou ces a e
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no enough o sa is y he adequa e c op-wa e equi emen s. Conside ing his limi a ion, a mo e p ecise
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i iga ion scheduling o maximize he yield is equi ed. In a ed he mal imaging eme ges as al e na i e o
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o he adi ional me hodologies o assess he c op-wa e s a us, especially when de ici i iga ion (DI)
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s a egies a e being applied. The aim o his s udy was o de ine he me hodology o assess he almond
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wa e s a us by means o he mal in o ma ion. The ial was conduc ed du ing 2014, du ing he ke nel- illing
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pe iod, in an almond expe imen al o cha d (SW Spain), wi h 5-yea -old ees, subjec ed o h ee i iga ion
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egimes: i) a ull-i iga ion ea men (C-100), which ecei ed 100% o ETC; ii) a egula ed de ici i iga ion
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(RDI-50), which ecei ed 100% o ETC excep du ing he ke nel illing pe iod, when his ea men was
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i iga ed wi h 50% o ETC; iii) and a low- equency de ici i iga ion ea men (LFDI), which ecei ed 100%
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o ETC excep du ing he ke nel illing pe iod, when i was subjec ed o con inuous pe iods o i iga ion-
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es ic ion, de ined in e ms o he h eshold alues o shaded lea wa e po en ial (Ψlea ). Th ee daily cu es
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o canopy empe a u e (TC), s oma al conduc ance o wa e apou (gs) and Ψlea wi h measu emen s a 8:00,
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11:00, 14:00, 17:00 and 20:00 we e de eloped. Addi ionally, C op Wa e S ess Index (CWSI), empe a u e
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di e ence be ween canopy and he su ounding ai (ΔTcanopy-ai ), and he ela i e index o s oma al
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conduc ance (IG) ob ained a di e en scales (canopy and ow) we e es ima ed. Signi ican co ela ions o
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in a ed he mal in o ma ion s. Ψlea and gs we e ob ained (p ≤ 0.05 and p ≤ 0.01), in pa icula , by using
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he he mal eadings aken a 11:30, 14:30 a 17:30 h, especially obus we e he ela ionships ob ained
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be ween TC and CWSI wi h Ψlea a 11:30 h; and be ween TC and CWSI wi h gs, and Ψlea a 14:30 h. Finally,
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conside ing he in a ed he mal moni o ing p ocedu e ( eadings a ee and ow le el), simila alues o TC
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we e ob ained, and he e o e, he images aken a ow le el o e ed a be e in o ma ion wi h a highe
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easibili y in e ms o image p ocessing.
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Keywo ds: The mog aphy, he mal indexes, wa e s ess, lea gas exchange and lea wa e po en ial.
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1.- In oduc ion
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I iga ed ag icul u e in he Sou h o Eu ope, and mo e conc e ely in semi-a id a eas such as Andalusia (S
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Spain), is c ucial o hei de elopmen , especially in hose u al egions wi h a lowe economic po en ial. In
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his line, o he case o Andalusia, i iga ed ag icul u e gene a es mo e han 60% o u al employmen s, and
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ep esen s 64% o ag icul u al p oduc ion. Cu en ly, 1,176,000 ha a e de o ed o i iga ed ag icul u e,
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co esponding o 24% o o al Andalusian ag icul u al su ace, and his being 33% o he i iga ed ag icul u e
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in Spain (ARA, 2011).
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Clima ic condi ions in his a ea a e cha ac e ized by he sca ci y and i egula i y o ain all, coinciding he
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d y pe iod wi h he season o highes e apo anspi a ion. Mo eo e , he las o ecas p edic ions a gue
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signi ican wa e esou ces deple ions; wi h an impo an declining in he soil wa e ese es, mo e accused
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pe iods o ain all es ic ions and inc easing in he a e age empe a u es (IPCC, 2014). In his ag eemen ,
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i is expec ed ha his si ua ion p omo es an imbalance be ween he i iga ion demand and he a ailable
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wa e esou ces in he Medi e anean ag icul u e (Daccache e al. 2012, Olesen e al. 2011). This ac will
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suppose an impo an cons ain o he compe i i eness be ween ag icul u e and o he mo e p oduc i e
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sec o s such as he indus y o ou ism. In addi ion, he in oduc ion o al e na i e c ops in o de o maximize
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he p o i abili y o ag oecosys ems will be equi ed, oge he wi h di e en s a egies o imp o e he
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ag icul u al wa e managemen (Ga cía-Teje o e al. 2014a).
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In his con ex , almond (P unus dulcis Mill.) is he hi d c op in e ms o su ace in Spain, ep esen ing globally
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almos 40%, and 84% wi hin he EU. Howe e , only 5% o he global p oduc ion is de eloped in Spain
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(FAOSTAT, 2016). Conc e ely, he su ace o almond in Andalusia is abou 152,000 ha, and wi hin hem,
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95% a e associa ed o ma ginal and ain- ed ag icul u e because o he clima e limi a ions, whe e annual
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ain alls does no exceed o 300 mm wi h low nu yields (CAPDR, 2016). Howe e , in he las ew yea s, he
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ag icul u al su ace de o ed o almond c op has signi ican inc eased, specially, in a eas whe e his c op
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was no adi ionally cul i a ed, hese new o cha ds being cul i a ed unde in ensi e and i iga ion p ac ices.
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Thus, almond can be ound unde e y di e en ag icul u al sys ems om he mos ma ginal si ua ions o
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he mos in ensi e o cha ds, which p omo es a wide ange o yields ( om 150 o 2,600 kg ha-1) (CAPDR,
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2016).
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Acco ding o Goldhame and Fe e es (2016), i iga ion is he mos limi ing ac o o his c op, wi h c op
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wa e - equi emen s oscilla ing be ween 900 and 1,350 mm (Goldhame and Gi ona, 2012). In his
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ag eemen , Goldhame and Fe e es (2016) epo ed alues close o 4,000 kg ha-1 (depending on he
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cul i a ) o i iga ion doses a ound 1,250 mm, wi h yield educ ions close o 14% when he i iga ion doses
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we e close o 1,000 mm. Mo e ecen ly, López-López e al. (2018) in a long- e m expe ience de eloped in
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he p o ince o Có doba (Andalusia, Sou h Spain), epo ed maximum yield alues ( 2,500 kg ha-1) in
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ma u e almond ees (c . Gua a), when hese ees we e i iga ed ecei ing he maximum c op wa e
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equi emen s (close o 10,000 m3 ha-1).
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In spi e o his, almond is conside ed a d ough - esis an c op because o i s xe omo phic p ope ies
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(To ecillas e al. 1996), and many au ho s ha e epo ed di e en esul s ela ed o he e ec s o de ici
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i iga ion (DI) s a egies (Pue o e al., 2013; Phoga e al., 2013; 2018; Spinelli e al., 2016; among o he s).
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Mo e ecen ly, López-López e al. (2018) discussed he e ec s o wa e de ici s in almond ees in e ms o
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wa e use, e alua ing di e en de ici i iga ion (DI) s a egies du ing h ee consecu i e yea s. These au ho s
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ound ha almond ees unde di e en mode a e DI s a egies we e able o keeping canopy olumes simila
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o hose ees ha we e ully i iga ed, hese being di ec ly ela ed wi h he almond capabili y o ob ain yield
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alues unde mode a e de ici i iga ion simila o hose epo ed by ully i iga ed ees; his ac being
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accompanied wi h simila soil wa e deple ions and anspi a ion le el.
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Taking in o accoun he maximum c op-wa e demand, he wa e sca ci y in semi-a id a eas, and he p ope
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esponse o his c op o mode a e wa e s ess, DI would be a sui able al e na i e o each equilib ium
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be ween he a ailable wa e esou ces and a p ope c op de elopmen wi h inal yields able o ensu e he
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compe i i eness and easibili y o his c op (Ga cía-Teje o e al., 2016a). Howe e , he applica ion o DI
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s a egies equi es a p ope knowledge abou he c op physiological s a us, wi h he aim o ensu ing he
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co ec c op de elopmen wi hou signi ican comp omising he yield and ui -quali y, especially when wa e -
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s ess is applied in di e en c op s ages (Spinelli e al., 2016). In his sense, acco ding o Pue o e al. (2013),
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when a DI s a egy is applied in ui ees, his is mainly de eloped supplying a speci ic wa e wi hholding,
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aken as e e ence he c op wa e equi emen s by means o he c op e apo anspi a ion (ETC), wi hou
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aking in o accoun he e ec s o canopy a chi ec u e, he deg ee o canopy co e o he soil managemen
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(among o he s); o wi hou conside ing he c op physiological s a us when his wa e s ess is applied. In
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his ega d, he mos p ope i iga ion scheduling should conside he whole o soil-plan -a mosphe e sys em;
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al hough in e ms o ep esen a i eness, he li e componen (plan ) would be o e ing he mos aluable
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in o ma ion, inasmuch as his e lec s he mos in eg a i e in o ma ion, mainly in e ms o inal yield.
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T adi ionally, c op wa e moni o ing has been de eloped by using punc ual measu emen s o s em (Ψs em)
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o lea (Ψlea ) wa e po en ial a midday o p e-dawn (Ψpd) (Shackel, 2011; No es e al., 2005) o moni o ing
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he gas-exchange pa ame e s such as anspi a ion (E), s oma al conduc ance (gs) o ne pho osyn he ic
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a e (A) (Gomes-La anjo e al., 2006).
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Acco ding o Remo ini and Massai (2003), S em is no only a p ope indica o o plan -wa e s a us as well
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as he c op p oduc i i y. In he same ein, Mi ás-A alos e al. (2016) epo ed ha wa e po en ial is a
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sui able indica o o almond wa e s a us, al hough i s use ulness is educed, because o a minimum numbe
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o eplica ions a e equi ed, and he ep esen a i eness in he whole plan is educed.
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In he las yea s, he use o emo e sensing in ag icul u e, and mo e conc e ely, in a ed he mal imaging o
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moni o he c op wa e s a us has been p og essi ely in oduced (Cos a e al., 2013). This echnique has
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been p ope ly desc ibed as a good me hodology o c op-wa e moni o ing in di e en woody c ops such as
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ci us (Ga cía-Teje o e al., 2011; González-Dugo e al., 2014); young almonds (Ga cía-Teje o e al., 2012),
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ines (Ga cía-Teje o e al., 2016b) o oli es (Egea e al., 2017). This echnique is based on he lea ene gy
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balance. When a wa e s ess si ua ion is applied, plan s esponds wi h a pa ial s oma al closu e, educing
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he s oma al conduc ance, limi ing he lea anspi a ion and p omo ing an a enua ion o he e apo a i e
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cooling p ocess, esul ing in highe lea / canopy empe a u e alues (Jones, 1999; 2004).
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This echnique can be applied a di e en moni o ing scales, om “lea o canopy” o “o cha d o basin” le el
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(Poble e-Eche e ía e al., 2014; 2016). The selec ion o he mos p ope me hodology will be ela ed wi h
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he desi ed goal and he economic a ailabili y (Cos a e al., 2013). In his sense, he use o he mog aphy
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a o cha d scale by using sa elli es images, allows o ake decisions ela ed o c op a iabili y o i iga ion
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scheduling, bu some cons ain s mus be aken in o accoun . On one hand, he mal images aking by
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sa elli es ha e he di icul y o depending o he momen in which he sa elli e passes abo e he o cha d;
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and on he o he hand, he spa ial and spec al esolu ion is no p ope . These cons ain s could be sol ed
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by using o unmanned ae ial ehicles (UAVs), despi e i s economically es ic ions. In his sense, he use o
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he mal images a o cha d scale, aken by means o UAVs, equi es ha ing he p ope echnology; and his
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ac can inc ease he cos o his ool, becoming less accessible he use o his echnology. By he con as ,
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hese senso s can be used a plan le el, wi h he mal came as much mo e p o i able, easing he
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accessibili y o his echnique by he i iga ion communi ies o echnicians.
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Likewise, he main cons ain s o his echnique a e ocused in he image p ocessing (many imes equi ing
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high ime consuming), and he co ec in e p e a ion o he in a ed he mal in o ma ion (Ga cía-Teje o e al.,
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2015a). Because o his, many imes di e en ela ionships be ween in a ed he mal in o ma ion and o he
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physiological pa ame e s such as gs, A, E, o Ψs em a e equi ed (Jones 2004; Jones e al., 2009), al hough
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hese ela ionships a e no always enough obus because o he high dependence o he me eo ological
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condi ions (Jones, 1999; 2004), he moni o ing p oceedings (Cos a el al., 2013), he cul i a (Cos a e al.,
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2012; Ga cía-Teje o e al., 2016b) o e en, he c op phenological s age (Cohen e al., 2015).
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Up o day, se e al au ho s ha e de eloped s a egies o op imize his echnique, de eloping di e en
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p o ocols and s a egies o ake he mal eadings unde ield condi ions (Jones e al., 2009; Pou e al., 2014;
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Poble e-Eche e ía e al., 2014, 2016, Ga cía-Teje o e al., 2012, 2016b) and desc ibing di e en
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ela ionships be ween in a ed he mal in o ma ion and physiological pa ame e s.
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We hypo hesize ha he mog aphy could be a sui able echnique o moni o almond wa e s a us, especially
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when his is subjec ed o DI p og ams. The aim o he p esen wo k was o e alua e he pe o mance o
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he mog aphy unde ield condi ions a wo moni o ing le els (plan and ow) o assess he c op wa e s a us
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in almond ees (c . Gua a), de e mining he bes momen o he day o ob ain he he mal in o ma ion and
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he mos obus he mal index o in e p e p ope ly he c op-wa e s a us.
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2. Ma e ial and me hods
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2.1. Expe imen al si e
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The ial was conduc ed du ing 2014 in an expe imen al o cha d o almonds (P unus dulcis Mill. D.A. Webb
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c . Gua a, g a ed on o GF677), loca ed in he Guadalqui i i e basin (37º 30’ 47’’ N; 5º 58’ 2’’ O) (Se ille,
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SW Spain). Plan ed in 2009, he ees we e spaced 6 x 7 m, and d ip i iga ed using wo pipe lines wi h
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emi e s o 2.3 L h-1, and 14 emi e s pe ee. The soil is sil y loam, ypical Flu isol (USDA, 2010), 2.5 m
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deep, e ile, and low ino ganic ma e con en (< 15.0 g kg-1). The oo s a e loca ed p edomina ely in he
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i s 50 cm o soil, co esponding o he in ended we ing dep h, al hough hese exceed mo e han one me e
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in dep h. Soil-wa e con en alues a ield capaci y (–0.033 MPa) and wil ing poin (–1.5 MPa) we e 0.35
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and 0.12 m3 m–3 espec i ely, wi h an allowable soil-wa e deple ion le el o 0.27 m3 m–3.
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The clima ology in he s udy a ea is a enua ed meso-Medi e anean, wi h an annual ET0 a e o 1,400 mm
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and accumula ed ain all o 540 mm, mainly dis ibu ed om Oc obe o Ap il.
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2.2. I iga ion ea men s
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Th ee i iga ion ea men s we e applied: i) a ull i iga ed ea men (C-100), which ecei ed 100% o he
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c op e apo anspi a ion (ETc) du ing he i iga ion pe iod (60 – 304 day o he yea , DOY), ii) a egula ed
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de ici i iga ion (RDI-50), which ecei ed 100% o ETC excep du ing he ke nel illing pe iod and p e-ha es ;
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when his ea men was i iga ed a 50% o ETC. Acco ding o his, he ke nel- illing pe iod ook place om
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171 o 227 DOY and p e-ha es om 228 o 243 DOY; his pe iod coinciding wi h he ime in which he
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ke nel has inished i s g ow h and he nu spli pe iod begins, jus be o e he i iga ion wi hholding (250 DOY)
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se en days be o e he ha es ing (257 DOY). iii) and a low- equency de ici i iga ion (LFDI) which ecei ed
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he 100% ETc du ing he i iga ion pe iod, excep du ing he ke nel- illing s age and p e-ha es ; when his
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ea men was i iga ed acco ding he egis e ed alues o Ψlea measu ed in shaded lea es. In his sense,
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du ing he ke nel- illing pe iod ( om 171 o 227 DOY) his ea men was subjec ed o i iga ion- es ic ion
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cycles wi h he ollowing i iga ion dynamic: Once s a ed he ke nel- illing pe iod, i iga ion was sup essed,
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ill eaching alues o Ψlea close o -2.0 MPa. Then, ees we e e-wa e ed wi h he same pe iodici y and
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amoun o wa e as C-100 (app oxima ely du ing 5 - 7 days) ill eaching simila alues o Ψlea o hose
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egis e ed in C-100. Once his h eshold alue was eached, his ea men was subjec ed o a new es ic ion
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pe iod un il he h eshold o Ψlea (~ -2.0 MPa) was again su passed. This dynamic o i iga ion- es ic ion
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cycles was main ained du ing whole s age o ke nel illing pe iod un il ha es ing.
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I iga ion doses we e calcula ed acco ding o he me hodology p oposed by Allen e al. (1998), ob aining he
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alues o e e ence e apo anspi a ion acco ding o he Penman-Mon ei h equa ion; by using a wea he
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s a ion ins alled in he same expe imen al o cha d; and using he c op coe icien s ob ained by Ga cía-Teje o
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e al. (2015b), which anged be ween 0.6 and 1.2. Acco ding o his, i iga ion doses applied o C-100, RDI-
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50 and LFDI we e 6,850, 4,400 and 4,180 m3 ha-1, espec i ely (Table 1).
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2.3. Plan measu emen s
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Du ing he expe imen al pe iod, h ee daily cu es o canopy empe a u e (TC), s oma al conduc ance o
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wa e apou (gs) and lea wa e po en ial (Ψlea ) we e ob ained du ing he ke nel illing and p e-ha es
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pe iod. These eadings we e aken a 08:30, 11:30, 14:30, 17:30 and 20:00 h local ime, du ing he days
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29 h July (Cu e 1) (210 DOY); 5 h Augus (Cu e 2) (217 DOY) and 27 h Augus (Cu e 3) (239 DOY). These
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days coincided wi h he i iga ion es ic ion pe iods o LFDI, wi h he aim o egis e ing he c op physiological
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s a us du ing pe iods o maximum wa e s ess in his ea men . In his sense, Cu e 2 was de eloped a
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week a e Cu e 1. The eason was ha , when Cu e 1 was de eloped, LFDI has been subjec ed o se en
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days o i iga ion es ic ion. Taking in o accoun he ob ained esul s du ing his cu e, i was decided o
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ex end his pe iod once mo e week, in o de o egis e he c op physiological esponse unde a si ua ion o
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maximum s ess. Finally, be ween Cu e 2 and 3, he e was a eco e y pe iod ( om 218 o 225 DOY), being
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he Cu e 3 de eloped a e 14 days wi hou i iga ion (in simila condi ions a Cu e 2).
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Table 2 shows he alues o ai empe a u e (Tai ), ela i e humidi y (RH), and apou p essu e de ici (VPD)
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egis e ed du ing he sampling days and o each moni o ing hou .
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Measu emen s o Ψlea we e conduc ed by using a p essu e chambe (Soil Mois u e Equipmen Co p., S a.
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Ba ba a, CA, USA), moni o ing 12 ees pe i iga ion ea men (one lea pe ee), loca ed in he no h side
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o he ee and being o ally ma u e, esh and shaded, a 1.5 m o heigh , app oxima ely. Addi ionally, he
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s oma al conduc ance o wa e apo (gs), was measu ed in hese same ees, by using a po ome e SC-1
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(Decagon De ices, INC, WA, USA), on one lea comple ely exposed o he sun pe moni o ed ee, and a
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1.5 m o heigh .
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TC was measu ed by using a The maCam (Fli SC660, Fli Sys ems, USA, 7-13 μm, 640x480 pixels)
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h oughou he day (8:30h, 11:30h, 14:30h, 17:30h, and 20:00h local ime), wi h emissi i y (ε) se a 0.96.
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Each pixel co esponds o an e ec i e empe a u e eading (Jones, 2004). Two me hodologies we e es ed
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o moni o he canopy empe a u e: i) 12 images we e aken a ee le el (one image pe ee assessed,
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hee being he same ees in which he measu emen s o Ψlea and gs we e de eloped), o each daily cu e,
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ea men and momen o he day), and ii) du ing Cu es 1 and 2, he mal images we e aken a ow le el,
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so ha , he ees moni o ed in he same image we e subjec ed o he same i iga ion ea men (Fig. 1).
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These images a ee le el we e aken in he sunli side o he ees, wi h he image placed a 2 m o he
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canopy (Fig. 1). Backg ound empe a u e was de e mined by measu ing he empe a u e o a c umpled
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shee o aluminium oil placed close o he lea es o in e es using ε= 1 (Jones e al. 2002). To acili a e he
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u he analysis o hese images, a cooled whi e sc een was used as backg ound, his being placed behind
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o each moni o ed ee o simpli y he isola ion o he canopy su ace h ough image p ocessing.
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The mal images a ee le el we e analysed wi h he so wa e de eloped by Ga cía-Teje o e al. (2012). This
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so wa e allows o emo e hose a eas o pixels conside ed s em and he backg ound (Fig. 2).
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Fo he case o he images aken a ow le el, hese we e analysed using he so wa e The maCam
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Resea ch P o (Fli Sys ems, USA), selec ing a speci ic a ea on he le and on he igh and ob aining he
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a e age alue o TC o each a ea (Fig. 3). This me hodology is much as e han he p e ious desc ibed by
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Ga cía-Teje o e al. (2012), al hough i does no disc imina es he ep esen a i e a eas wi h he same
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easibili y, and he a eas selec ion is done acco ding o he isual pe spec i e o he ope a o .
220
Conside ing he TC alues ob ained a ee le el, h ee di e en he mal indica o s we e calcula ed: he
221
di e ence be ween canopy and he su ounding ai (ΔTcanopy-ai ), he c op wa e s ess index (CWSI), and he
222
index o he ela i e s oma al conduc ance hese being calcula ed as ollows (Cos a e al., 2013):
223
224
ΔTcanopy-ai = TC - Tai (1)
225
226
𝐶𝑊𝑆𝐼 = ∆𝑇𝑐𝑎𝑛𝑜𝑝𝑦−𝑎𝑖𝑟− ∆𝑇𝑤𝑒𝑡
∆𝑇𝑑𝑟𝑦− ∆𝑇𝑤𝑒𝑡 (2)
227
228
𝐼𝐺= ∆𝑇𝑑𝑟𝑦− ∆𝑇𝑐𝑎𝑛𝑜𝑝𝑦−𝑎𝑖𝑟
∆𝑇𝑐𝑎𝑛𝑜𝑝𝑦−𝑎𝑖𝑟− ∆𝑇𝑤𝑒𝑡 (3)
229
whe e ΔTcanopy-ai , ∆Td y and ∆Twe a e he di e ences be ween canopy and ai empe a u e o he c op in
230
he momen o he measu emen , when he c op has he s oma a ully closed and when i is ully anspi ing,
231
espec i ely. TC is he canopy empe a u e and Tai he empe a u e o he su ounding ai .
232
To ob ain he e e ence alues o ∆Twe , he e was es ima ed he non-wa e s ess baseline (ΔTcanopy-ai = a
233
+ b*VPD) acco ding o Idso e al. (1981), using a ∆Td y alue equal o 5 ºC, as i was p oposed by Jackson
234
e al. (1981). Non-wa e s ess baseline was es ima ed using he canopy empe a u e eadings ob ained
235
om ull i iga ed ees (C-100).
236
237
2.4. Expe imen al design and s a is ical analysis
238
The expe imen al design was o andomized blocks, wi h ou eplica ions pe i iga ion ea men . Each
239
eplica ion had 15 ees (3 ows and 5 ees pe ow), being moni o ed he h ee cen al ows o each
240
eplica ion (n=12).
241
Fo each measu emen day, an explo a o y desc ip i e analysis o da a (Ψlea , gs and TC) was conduc ed by
242
applying a Le ene’s es o check he a iance homogenei y o he s udied a iables. Signi ican di e ences
243
be ween i iga ion ea men s (p ≤ 0.05) in he s udied a iables we e iden i ied by applying a one-way
244
ANOVA and a Tukey’s es o ea men sepa a ion, wi h he SPSS s a is ical so wa e (SPSS Inc., 15.0
245
S a is ical package; Chicago, IL, USA).
246
To e alua e he non-wa e s ess baselines, a linea co ela ion analysis was made (n = 15). To e alua e
247
he ela ionships be ween a iables, a linea co ela ion analysis be ween he alues o he mal indica o s
248
(TC, ΔTcanopy-ai , CWSI and IG) and he c op physiological a iables (Ψlea and gs) was made, by using he
249
a e age alues o each ea men and sampling ime (n = 9). The ob ained co ela ion coe icien s we e
250
8
used o iden i y which would be he bes ime o ca y ou TC eadings and he mos ep esen a i e he mal
251
index as a p oxy o c op physiology ai s.
252
Finally, compa a i e s udy be ween he TC eadings aken a ee and ow le el was conduc ed by means o
253
a linea co ela ion analysis be ween hese alues, using he a e age alues o each ea men and he
254
whole da a ob ained du ing he wo i s daily cu es (n=30).
255
256
3. Resul s and discussion
257
3.1. Daily e olu ion o c op physiological s a us
258
Figu e 4 shows he e olu ion o Ψlea , gs, and TC measu ed a ee le el du ing he h ee daily cu es
259
de eloped du ing he i iga ion pe iod in which he wa e s ess egimes we e imposed. On o e all, as he
260
clima ic condi ions along he day became mo e ad e se, Ψlea eached mo e nega i e alues, wi h a inal
261
eco e y a he end o he day. By con as , gs inc eased du ing he i s eadings un il eaching a maximum
262
poin in which a signi ican dec ease was obse ed, his coinciding wi h he momen o he day in which he
263
clima ic condi ions we e mo e ex eme. A e his poin a sligh eco e y o gs was ound wi h he las
264
measu emen s o he day. In ela ion o TC his a iable showed a mo e dependen end on he clima ic
265
condi ions along he day, eaching he maximum alues in hose momen s in which he Tai alues we e he
266
highes . Du ing cu es 1 and 2, he lowes alues o Ψlea we e eached a 17:30 h, coinciding wi h he highes
267
VPD alues egis e ed du ing hese days; and wi h he momen s in which he TC alues we e maximum.
268
Conside ing he ob ained alues o each ea men , no di e ences we e obse ed a 8:30 h, bu hese we e
269
appea ing along he day wi hou obse ing a o al eco e y be ween he DI ea men s and C-100 a 20:00
270
h. I is ema kable ha he obse ed di e ences in e ms o Ψlea we e highe du ing he Cu e 2, his being
271
associa ed wi h he mo e se e e clima ic condi ions de ec ed and he imposed wa e es ic ion pe iod o
272
LFDI in his cu e, which had been p olonged o a u he se en days, in compa ison o Cu e 1.
273
Rega ding o gs, du ing Cu e 1, all he ea men s showed a g owing endency, eaching he maximum
274
alues a 14:30 h (VPD = 2.61 kPa). Howe e , du ing he Cu e 2, he maximum alues we e obse ed a
275
11:30 h (VPD = 1.82), om which gs dec eased, showing a pa ial eco e ing in C-100 a he end o he day.
276
This di e ence obse ed o he case o gs could be associa ed wi h he mo e se e e clima ic condi ions
277
egis e ed du ing he Cu e 2, in compa ison o he p e ious one. Finally, i is no iceable ha he deple ion
278
in TC was accompanied wi h a sligh eco e y o gs and he sligh eco e y o Ψlea and gs du ing he eadings
279
a 20:00 h.
280
Rega ding o he alues ob ained du ing he Cu e 3, i was ob ained h ee weeks a e Cu e 2, when
281
clima e condi ions we e simila o hose obse ed in he p e ious one, and LFDI was subjec ed o 15 days
282
o i iga ion es ic ion. In his sense, i was obse ed a simila end o ha de ec ed in Cu e 2, wi h he
283
highes alues o gs obse ed a 11:30 (VPD = 1.31 kPa), wi h a signi ican educ ion in all he ea men s a
284
14:30 h, ollowed by a pa ial eco e y a 17:30 h, and a new descend a he end o he day. This dec easing
285
end occu ed a 14:30 h, being his esponse associa ed wi h a pa ial s oma al closu e, when clima ic
286
condi ions, specially he VPD alues a e s ongly ele a ed. E en mo e, his descend in he alues o gs
287
9
p omo ed ha , he eadings o Ψlea be ween 11:30 and 14:30 we e simila , and he pa ial eco e y o gs a
288
17:30 was accompanied wi h a signi ican lessen alues o Ψlea .
289
Rela ing o he TC eadings, hese we e highly de e mined by he clima ic condi ions. On o e all, TC eadings
290
in he h ee s udied ea men s we e below o ai empe a u e (Tai ), excep he eadings aken a 08:30 and
291
11:30 h o he Cu es 2 and 3. The highes di e ences in TC be ween ea men s we e de ec ed specially
292
in he eadings aken a 11:30, 14:30 and 17:00, al hough hese we e no as pa en as o he case o Ψlea .
293
On o e all, and aking in o accoun he moni o ed physiological a iables, i can be assumed ha Ψlea was
294
he pa ame e ha e lec ed he highes di e ences be ween ea men s. In his sense, du ing he Cu e 1,
295
signi ican di e ences we e obse ed be ween C-100 and he emaining ea men s a 11:30 and 14:30 h,
296
wi h an ab up descend in he eadings conduc ed a 17:30 (<-2.0 MPa), wi hou di e ences be ween he
297
h ee i iga ion ea men s. Du ing he Cu e 2, he Ψlea alues egis e ed in C-100 we e signi ican di e en
298
han hose egis e ed in he emaining ea men s du ing all day (excep a 8:30 h), no being eached he
299
h eshold alue o -1.5 MPa in C-100. Finally, i also d aws a en ion ha , du ing Cu e 3, C-100 eached
300
again Ψlea alues close o -2.0 MPa, as i was i ed o he Cu e 1.
301
I is ema kable ha , whe eas Ψlea was able o show signi ican di e ences be ween ea men s, his ac
302
was no as pa en in e ms o gs, because o he low capaci y o almond o egula e he s oma al closu e
303
unde d ough condi ions. In his ega d, almond ees p esen a as eco e y o wa e po en ial, bu a delay
304
in he alues o gs as i has been s a ed by au ho s such as To ecillas e al. (1996) o Rome o e al. (2004).
305
In his line, in physiological e ms, when almond is subjec ed o a mild- o-mode a e wa e s ess si ua ion a
306
s oma al conduc ance educ ion is no as pa en as he e ec s in e ms o wa e po en ial because o i s low
307
capabili y o egula ing he s oma a when a wa e s ess si ua ion is applied, as i has been discussed by
308
some au ho s such as Wa ingue e al. (1990), Egea e al. (2011) o Eichi (2013). In his ag eemen ,
309
p e iously o obse e a signi ican educ ion in gs, almond esponds wi h signi ican descends in e ms o
310
lea o s em wa e po en ial, (Ga cía-Teje o e al, 2012, 2015b). Consequen ly, almond would be able o
311
main ain accep able le els o gs (p omo ing signi ican descends in he c op-wa e po en ial) bu , keeping
312
op imum alues o ca bon assimila ion, pho osyn he ic a e, and hence inc easing he in insic wa e -use
313
e iciency (McCu chan and Shackel, 1992; Rouhi e al., 2007).
314
Gomes-La anjo e al. (2006) epo ed alues o Ψlea o di e en cul i a s, which anged be ween -1.72 and
315
-2.0 MPa in Glo ie a; -1.71 and -2.40 MPa in Fe agnes; -1.91 and -2.34 MPa in F ancoli; -1.97 and -2.26
316
MPa in Lau anne, and -1.88 and -1.92 MPa in Masbo e a. In his line, hese alues co espond o
317
measu emen s done a midday in well-wa e ed ees, which a e in line wi h he h eshold ange be ween -
318
1.5 and -2.0 MPa conside ed and ob ained in his wo k o C-100.
319
Ob iously, his wa e po en ial deple ion a ec s o lea gas exchange. In his sense, o ull i iga ed
320
condi ions, daily cycle o gas exchange is almos cons an when no adia ion limi a ion occu (To ecillas e
321
al., 1988; Klein e al., 2001; Rome o e al., 2006) and apou p essu e de ici (VPD) is no highe han 2 KPa
322
(Rome o e al., 2006). Howe e , in ou case, he alues o VPD we e highe han his alue du ing he h ee
323
cu es when he eadings we e aken be ween 11:30 and 20:00 h, which would explain he daily a ia ion
324
16
conse ación del agua en ambien es semiá idos. Tocina Es udios Locales, Re is a de In es igación
535
Local, 5, 175-190.
536
Ga cía-Teje o, I.F., Cos a, J.M., Egip o, R., Lima, R.S.N., Du án, V.H., Lópes, C., Cha es, M.M. 2016b.
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The mal da a o moni o c op-wa e s a us in i iga ed Medi e anean i icul u e. Ag ic. Wa e
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Ga cía-Teje o, I., He nández, A., Padilla-Díaz, C.M., Diaz-Espejo, A., Fe nández, J.E. 2017. Assessing plan
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Goldhame , D.A., Fe e es, E. 2016. Es ablishing an almond wa e p oduc ion unc ion o Cali o nia using
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Gomes-La anjo, J., Cou inho, J.P., Galhano, V., Co dei o, V. 2006. Responses o i e almond cul i a s o
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almond ees when subjec ed o wa e de ici s. Ag ic. Wa e Manage. 195, 84-93.
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To ecillas, A., Ruiz-Sanchez, M.C., del Amo , F., León, A. 1988. Seasonal a ia ions on wa e ela ions o
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To ecillas, A., Ala cón, J.J., Domingo, R., Planes, J., Sánchez-Blanco, M.J. 1996. S a egies o d ough
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esis ance in lea es o wo almond cul i a s. Plan Sci. 118, 135–143.
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Resou ce Conse a ion Se ice, 334 pp.
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Wa inge , A., Heilmeie , H., Ha ung, W., Schulze, E.D. 1990. Daily and seasonal cou ses o lea
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conduc ance and abscisic acid in he xylem sap o almond ees (P unus dulcis (Mille ) D.A.Webb)
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Za co-Tejada, P.J., Be ni, J.A.J., Suá ez, L., sepulc é-Can ó, G., Mo ales, F., Mille , J.R. 2009. Imaging
629
chlo ophyll luo escence wi h an ai bone na ow-band mul ispec al came a o ege a ion s ess
630
de ec ion. Remo e Sens. En i on. 113, 1262-1275.
631
632
633
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19
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FIGURES
641
642
643
644
Figu e 1. Example o he mal images a plan (le ) and ow ( igh ) le el
645
646
647
648
Figu e 2. Example o image p ocessing using he so wa e de eloped by Ga cía-Teje o e al (2012).
649
On he igh , he ini ial he mal imaging; on he le , a bi map image, in which he black a ea
650
ep esen s he pixels o he he mal image conside ed o calcula e he canopy empe a u e.
651
652
653
654
Figu e 3. Example o image p ocessing a ow le el using he The maCam Resea ch P o (Fli
655
Sys ems, USA).
656
657
20
658
Figu e 4. Daily cu es o lea wa e po en ial (Ψlea ), s oma al conduc ance (gs) canopy empe a u e
659
(Tc) and ai empe a u e (Tai ) in almond ees subjec ed o di e en i iga ion doses: C-100, ull
660
i iga ed ea men ; RDI-50, egula ed de ici i iga ion; LFDI, low- equency de ici i iga ion. Le e s
661
a, b, and c show signi ican di e ences be ween C-100, RDI-50 and LFDI ea men s, espec i ely
662
(p<0.05).
663
664
665
666
21
Figu e 5. Non-wa e s ess baseline (∆Tcanopy-ai ) = a*VPD + b. Da a ob ained o he DOYs 210, 217
667
and 239 and using he eadings aken a 8:30, 11:30, 14:30, 15:30 and 20:00.
668
669
670
671
Figu e 6. Rela ionships be ween canopy empe a u e eadings (TC), he di e ence be ween
672
canopy and ai empe a u e (ΔTcanopy-ai ) and c op wa e s ess index (CWSI) wi h lea -wa e
673
po en ial (Ψlea ).
674
675
676
Figu e 7. Rela ionships be ween canopy empe a u e eadings (TC) a ee and ow le el.
677
678
679
680
681
682

22
TABLES
683
684
Table 1. Clima ic condi ions, wa e equi emen s and i iga ion doses applied du ing he season
685
Pe iod
(DOY)
Tai
(ºC)
RH
(%)
Rain all
(mm)
ET0
(mm)
KC
ETC
(mm)
C-100
(mm)
RDI-50
(mm)
LFDI
(mm)
60 o 90
13.53
70.18
55.6
92.11
0.3
27.63
0
0
0
91 o 120
17.95
72.96
35.6
114.84
0.55
34.74
8.03
8.03
8.031
121 o 151
21.42
54.06
12.6
175.79
0.9
118.66
109.21
109.21
109.21
152 o 181
23.40
58.88
7.4
176.94
1.05
167.21
161.66
108.32
107.88
182 o 212
25.24
58.81
0.2
184.24
1.15
190.69
190.54
91.46
77.85
213 o 243
26.05
54.06
0
173.82
1.15
179.90
179.90
88.15
79.56
244 o 273
22.66
78.06
175.8
104.99
0.8
75.59
23.02
23.02
23.02
274 o 304
19.93
77.67
73.2
79.86
0.7
50.31
12.5
12.5
12.5
DOY. day o he yea ; Tai . a e age ai empe a u e; RH. a e age ela i e humidi y. ET0. e e ence
686
e apo anspi a ion; KC. c op coe icien ; ETC. c op e apo anspi a ion; C-100. con ol ea men ; SDI-50.
687
egula ed de ici i iga ion a 50% o ETC du ing he ke nel illing pe iod; LFDI. low- equency de ici i iga ion
688
du ing he ke nel illing pe iod.
689
690
691
Table 2. A e age alues o ai empe a u e (Tai ). ela i e humidi y (RH) and apou p essu e de ici
692
(VPD) egis e ed du ing he daily cu es
693
Cu e 1 (210 DOY)
Cu e 2 (217 DOY)
Cu e 3 (239 DOY)
Hou
Tai (ºC)
RH (%)
VPD (kPa)
Tai (ºC)
RH (%)
VPD (kPa)
Tai (ºC)
RH (%)
VPD (kPa)
08:30
24.4
63
0.94
16.6
63
0.70
21.3
60
1.01
11:30
25.3
69
0.99
27.4
50
1.82
27.4
64
1.31
14:30
34.1
51
2.61
33.4
45
2.82
37.5
31
4.43
17:30
34.5
42
2.29
42.1
21
6.49
41.0
25
5.81
20:00
31
41
1.84
34.1
27
3.90
38.8
26
5.10
Tai . a e age ai empe a u e; RH. a e age ela i e humidi y; VPD. apou p essu e de ici
694
695
696
697
698
699
700
701
702
703
23
Table 3. Pea son’s co ela ion coe icien s be ween he mal in o ma ion and he s udied
704
physiological a iables
705
Hou
TC
∆Tcanopy-ai
CWSI
IG
8:30
gs
-0.32*
ns
-0.40*
ns
Ψlea
ns
ns
ns
ns
11:30
gs
ns
ns
ns
ns
Ψlea
-0.85**
-0.69*
-0.85**
ns
14:30
gs
-0.70*
ns
-0.82**
ns
Ψlea
-0.39*
ns
-0.69*
ns
17:30
gs
ns
-0.70*
-0.62*
ns
Ψlea
-0.39*
ns
-0.34*
0.74**
20:00
gs
-0.75*
ns
ns
ns
Ψlea
ns
ns
ns
ns
TC. canopy empe a u e; ∆Tcanopy-ai . di e ence be ween canopy and ai empe a u e; CWSI. c op-
706
wa e s ess index; IG. ela i e index o s oma al conduc ance; gs. s oma al conduc ance o wa e
707
apou ; Ψlea . lea -wa e po en ial in shaded lea es. * and ** show signi ican ela ionships a
708
con idence le el o 95 and 99%. espec i ely.
709
710
711
712
713
714
715
716
717
718
719
720
721
9
Table 4. Example o alse-colou ed images aken a ee and ow le el du ing he Cu e 1 in he di e en i iga ion ea men s and momen o he day.
The alues o canopy empe a u e (TC) co espond o he a e age o i e measu emen s aken o each ea men and momen o he day.
T ee le el
Row le el
C-100
RDI-50
LFDI
C-100
RDI-50
LFDI
08:30
TC (ºC)
21.7
21.6
21.4
21.3
21.3
21.4
11:30
TC (ºC)
23.3
23.6
23.4
23.5
23.6
23.4
14:30
TC (ºC)
26.9
27.0
29.9
27.4
28.6
29.1
17:30
TC (ºC)
32.5
30.9
30.0
32.3
30.7
31.0
20:00
TC (ºC)
29.2
28.6
28.9
29.1
28.6
29.0
10
Table 5. Example o alse-colou ed images aken a ee and ow le el du ing he Cu e 2 in he di e en i iga ion ea men s and momen o he day.
The alues o canopy empe a u e (TC) co espond o he a e age o i e measu emen s aken o each ea men and momen o he day.
T ee le el
Row le el
C-100
RDI-50
LFDI
C-100
RDI-50
LFDI
08:30
TC (ºC)
20.9
20.5
22.2
21.2
21.2
21.4
11:30
TC (ºC)
27.4
28.6
29.1
27.6
28.7
29.0
14:30
TC (ºC)
30.2
32.5
32.9
30.7
32.8
33.1
17:30
TC (ºC)
31.8
32.2
31.1
30.5
30.5
31.2
20:00
TC (ºC)
31.1
31.5
31.9
31.3
31.7
32.2