Leaf area index and light distribution in olive tree canopies (Olea europaea L.)

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1 RESEARCH PAPER OPEN ACCESS Lef re index nd light distriution in olive tree cnopies (Ole europe L.) Interntionl Journl of Agronomy nd Agriculturl Reserch (IJAAR) ISSN: (Print) (Online) Vol. 8, No. 5, p , 2016 Moun Aïchi Mezghni 1, Gout Hssoun 1, Lrii Itissem 2, Foued Lidi 1 1 Olive Tree Institute, Sttion of Sousse, Sousse, Tunisi 2 Institut Supérieure Agronomique Chott Mériem; Sousse, Tunisi Article pulished on My 25, 2016 Key words: Olive tree, Vse form, LAI, Photosyntheticlly ctive rdition, rtio PART/PARI. Astrct The lef re index (LAI) nd the sptil lef rrngements re the min fctors which influenced the rdint energy distriution within the tree. The lef re index hs een shown to e n importnt fctor of the olive productivity. Although, the photosyntheticlly ctive rdition intercepted y leves (PAR) is the min environmentl fctor tht determined the dry mtter production, which is the min source of energy for the photosynthesis. Therefore, commercil sensor for LAI determintion (Sun scn DELTA-T Devices Ltd), ws tested for olive trees, in n olive orchrd locted ner Sousse, centrl Tunisi (36N, 10E). The plnts were cultivted t 7m 7m nd trined on vse system. Mesurements were mde t two tree s lyers; on lower nd upper prt of the cnopy nd on the four crdinl directions (north, south, est nd west). The results showed tht the LAI ws more importnt on the lower prt of the cnopy thn on the upper one for ll directions. LAI ws lso higher on South nd Est side of tree. The Incident Photosyntheticlly Active Rdition PARI, ws quite constnt for ll directions. However, the trnsmitted frction PART decresed inside the tree cnopy. The lower prt of the cnopy ws less shded for the vse tree form. There is significnt negtive reltionship etween LAI nd rtio PART/PARI. These results will e the fundmentl sis of the olive pruning sis nd to estlish new intensive olive orchrds with fully developed cnopies which intercepted the mximum solr rdition. * Corresponding Author: Moun Aïchi Mezghni ychimoun@yhoo.fr Mezghni et l. Pge 60

2 Introduction In ll fruit orchrds, the high productive plnting must e pursued. Trees should express long the yer high photosynthesis for using the principl ssimiltes on fruit production. All processes long the productive cycle must e optimised nd completed without nomlies nd disorders which compromise the yield nd the life of plnting (Tomesi, 2006). Leves re the ctive interfce of energy, cron nd wter exchnges etween tree cnopies nd the tmosphere. The ssimilte production depends on lef re nd its light exposure expressed y the cnopy volume, the lef density, the lef light interception. The lef cnopy component cn e determined y Lef Are Index (LAI) which regultes numer of physiologicl processes such s the evpotrnsportion nd the photosynthesis (Villloos et l., 1995; Cutini et l., 1998). The photosynthetic ctive rdition (PAR) intercepted y crop cnopy, is the min fctor tht determines dry mtter production. This mount is determined y the incident rdition conditions. The cnopy photosynthesis nd thus iomss production were the result of the photosynthetic response of leves nd the distriution of rdition within the cnopy (Mriscl et l., 2000). Olive orchrds re the min component of numerous griculturl systems in the Mediterrnen region. An olive orchrd is heterogeneous stnd, since the leves re locted within n envelope tht is distriuted in the spce ccording to the plnting pttern nd the row orienttion (Mriscl et l., 2000). The intensity of incident light decreses through the olive crown nd this ttenution my vry ccording to the trining system nd the cnopy density. Within heterogeneous stnd, the ttenution of rdition resulting from sorption nd scttering y leves cretes verticl grdient of men irrdince. Extensive cropping systems intercept round 20-30% of the solr rdition while new intensive orchrds intercept t most 70% of the solr (Villloos et l., 1995; Mriscl et l., 2000). The lef component of cnopy my e quntified y its structurl ttriute LAI (projected lef re per unit of ground re). Its distriution in field crops is more homogeneous thn in rrys of trees. The leves re not distriuted homogeneously nd there re lrge gps within the vegettion (Villloos et l., 1995). Tomesi (2006) noted tht trees with cnopy volume of m 3.h -1, showed lef re index equl to 6.I. LAI often pproched to 2.5 for olive orchrd with density equls to 300 trees h -1 [5]. Different instruments hve een developed in order to mesure rpidly nd relily LAI of plnt cnopies like plnt cnopy nlyzer (Villloos et l., 1995) nd hemisphericl photogrphs (Bonhomme nd Chrtier, 1972). The ojectives of this work were () to evlute the use of Sun scn DELTA-T Devices Ltd for mesuring LAI in olive trees (Ole europe L. cv Meski) nd studying the vrition of folige density within the tree nd () to nlyze the distriution of photosyntheticlly ctive rdition over the cnopy nd its extinction within the tree. Mteril nd methods Study site nd plnt mteril The experiment ws performed during 2008 in n olive orchrd locted in Centrl Tunisi, out 40 km from Sousse (36.08 N, E). In this region, climte is semi-rid with rinfll concentrted from utumn to spring (350mm yer -1 ) nd n evpotrnspirtion (ET0) round 1400mm. The orchrd ws plnted in 1985 with 7mx7m spcing (204 trees h -1 ), which is the density usully used in this region for intensive plnttion. The used vriety ws Meski ( locl tle olive cultivr) which ws known for hving mrked lternte ering ehviour, nd is used for tle olive production due to its lrge fruit size. The olive trees were trined to vse form. The tree skeleton ws formed y single trunk of 0.7m height nd 3 to 4 primry rnch, oriented on different directions with n ngle of 45. This system hs for dvntge tht is known for its uniform light distriution nd is suitle for tle Mezghni et l. Pge 61

3 olives. Olive trees were drip irrigted during the dry seson, from April to end of Septemer. Mesurements Mesurements were mde during the lst week of Novemer when shoot growth cesed. Vegettive growth prmeters like height nd width trunk, tree height nd cnopy width were noted. Then, crown volume pr tree nd per hectre, fruit setting re nd cnopy ground index, were clculted. The LAI nd the Light interception mesurements were relized y SunScn system (Eijkelkmp). The SunScn pckge consists of light interception proe, dt collection module nd externl PAR sensor. A direct reltion exists etween the quntity of incoming rdition sored (intercepted) nd iomss creted. The SunScn system suited for mesurement nd nlysis of the PAR in the cnopy of crop. Ry redings nd derived functions such s light trnsmission nd lef re index (LAI= vrition in light perfortion y cnopy) cn e shown, collected nd stored. Mesurements were crried out on eighteen trees. Mesurements were noted elow nd inside the tree precisely in the centrl prt of the tree, during cler dys, etween 9.00 nd solr time. These mesurements were lso relised on the four crdinl directions North, South, Est nd West. The incident photosyntheticlly ctive rdition (PARI) nd the trnsmitted photosyntheticlly ctive rdition (PART) were recorded. The reltionship etween the rtio PART / PARI nd LAI were investigted in order to study the evolution etween these two prmeters. Sttisticl nlyses Mens nd stndrd devition were clculted. Anlysis on vrince (ANOVA) ws performed y using SPSS When significnt differences occurred, mens were seprted y the Duncn s multiple rnge test t (P<0.05). Results Tree growth All mesurements noted on trunks nd cnopies were reported in Tle 1. The verge height trunk tree ws equl to 37.2cm while their width ws out of 24.4cm. Tree height reched n verge of 4.6 m while its width ws out of 4.8 m. Finl cnopy volume ws clculted per tree nd then reported per hectre y multiplying it to numer of trees. For density of 204 trees h -1 used in his orchrd, the volume cnopy per tree nd per hectre ws equl to 48.4 m 3 nd m3/h, respectively. Fruit setting reched 19.1 m 2 Tree -1. The ground cover index ws estimted to 39% of totl soil. Tle 1. Vegettive prmeters mesured on olives trees. Unit Vlues Trunk height cm 37.2 ±10.9 Trunk width cm 24.4 ± 3.1 Tree height m 4.6 ± 0.6 Cnopy height m 4.1 ± 0.6 Cnopy width m 4.8 ±0.7 Crown volume m3/ Tree 48.4 ± 9.4 m3/h ± Fruit setting surfce m2/tree 19.1 ±5.2 Cnopy ground index % 39 ± 10.7 Lef re index The lef re index vried etween 1.6 nd 3.1 m 2 m - 2 considering the entire tree nd the different directions. Although, the verge vlue of LAI clculted for the different directions, ws equl to 2.8 ± 0.55 m 2 m -2 nd 2.0 ± 0.11 m 2 m -2, respectively on the lower nd the upper prt of the cnopy (Fig. 1). The difference etween the two dt ws significnt (P 0.05). Our results showed tht LAI ws more importnt on the lower prt of the tree nd this result ws verified for ll directions. Differences etween LAI mesured on the two level height of the tree, were sttisticlly different for the north nd the est direction nd not significnt for the south nd west one. LAI ws higher on the south direction nd est direction. LAI ws equl to 2.92 ± 0.61m 2 m -2 (South) nd 3.10 ± 0.43 m 2 m -2 (est) nd 2.37± 0.35 m 2 m -2 (South) nd 2.20± 0.44 m 2 m -2 (est) respectively for the lower nd the upper tree prt, respectively. These Mezghni et l. Pge 62

4 PART/PARI Trnsmitted PAR (µmole/m 2 /s) LAI Incident PAR( μmole/m 2 /s) Int. J. Agri. Agri. R. results showed tendency of the tree to e more developed on these directions nd on the lower prt. Lower cnopy Higher cnopy 4,0 3,5 3,0 2,5 2,0 1,5 1,0 0,5 0,0 Tree North South Est West Direction Fig. 1. LAI mesured on the two prts of the tree nd for the four directions. Ech vlue is the verge of eighteen trees. Vlues re mens ± stndrd errors which is represented s verticl rs. Dt with different letters indicte significnt differences mong the two levels prt of the tree (Duncn tests, P<0.05). Photosyntheticlly ctive rdition The incident photosyntheticlly ctive rdition PARI ws more or less constnt on the different prt of the tree nd for the different directions (Fig.2A). It vried from 1353 to 1383 µmol/m 2 /s on the lower prt of the tree nd etween µmol/m 2 /s on upper one. The differences etween the dt mesured on the two levels of the tree were not significnt for ll directions. The trnsmitted Photosyntheticlly ctive rdition PART ws higher t the upper prt of the cnopy. The PART tree vlue (verge vlue recorded etween the four directions) ws equl to ± 63.2µmol/m2/s on the lower prt of the tree nd ± 102.3µmol/m2/s on the upper one. It seems tht the trnsmitted PART decresed on the tree ecuse the density of folige ws more importnt on the upper prt of the tree. For the lower prt of the tree, vlues vried etween minimum of ± 37.5 µmol/m2/s (Est direction) nd ±84.43 (West one). For the higher prt, it rnged until ± 79.9 µmol/m2/s (south direction) to 441.1± µmol/m2/s (North). The differences etween the two lyers of tree were significntly different only for north nd est directions (Fig. 2B). Mezghni et l A Tree North South Est West Lower cnopy Higher cnopy Direction B Tree North South Est West Lower cnopy Higher cnopy Direction Fig. 2. PARI () nd PART() estimted on the tree nd on the different directions for the two prt of the cnopy. Vlues re mens ± stndrd errors which is represented s verticl rs. Dt with different letters indicte significnt differences mong the two levels prt of the tree (Duncn tests, P<0.05). NS: no significnt Exponentil reltion etween ll mesured vlues of LAI nd the rtio etween trnsmitted photosyntheticlly ctive rdition nd incident photosyntheticlly ctive rdition PARI ws found with R 2 equls to The coefficient ws significnt t p = (y = 0,8831e -0,704x, x ws LAI nd y ws the rtio vlue). When LAI incresed, the rtio vlue recorded etween trnsmitted photosyntheticlly ctive rdition nd incident photosyntheticlly ctive reduced (Fig. 3). 0,6 0,5 0,4 0,3 0,2 0,1 0 y = 0,8831e -0,704x R² = 0, ,5 1 1,5 2 2,5 3 3,5 4 4,5 LAI Fig. 3. Reltionship etween LAI nd rtio of trnsmitted photosyntheticlly ctive rdition y Incident photosyntheticlly ctive rdition PARI. Mesurements were tken in the different prts of the tree. Pge 63

5 Discussion According to our experiment conditions, the trees showed crown volume equl to 48 m 3 /tree nd m 3 /h, respectively. These results re in ccordnce with those reported y Pstor (1983) nd Pstor nd Humnes (1990) which indicted the sme vlue for cnopy size oserved in intensive plnttion in Andluci. Pstor nd Humnes (1990), Pstor Munõz-Coo et l. (2006) nd Aïchi (2014) indicted tht optimum olive orchrd volume rnged etween m 3 /h in rin-fed conditions nd etween m 3 /h in irrigted one. When totl crown volume ws higher thn m 3 /h, it ws oserved competition etween trees for the light distriution. In our experiment, LAI mesurements on isolted trees in the field were ccurtely determined using the Sun scn DELTA-T Devices Ltd. The lef re index LAI is rnging etween 1.6 m 2 m -2 nd 3.16 m 2 m -2. These vlues seem to e similr to those oserved y Bongi nd Pllioti (1994) which noted vlue equl to 2.5. Our results showed tht LAI ws more importnt on the lower prt of the tree nd this result ws verified for ll directions. The results showed tendency of the tree to e more developed on the est nd south directions for the lower prt of the tree. These result confirmed the fct tht the olive orchrd is heterogeneous stnd, since the leves re locted within n envelope tht is distriuted in the spce ccording to plnting nd row orienttion (Mriscl et l., 2000). For these types of cnopy, interctions etween stnd structure nd rdition re complicted to del with in field trils. Folige is the centrl nd sic descriptor of vegettion condition in wide vriety of physiologicl, climtologicl nd iochemicl studies (Asner et l., 2003). The trnsmitted Photosyntheticlly ctive rdition (PART) decresed through the olive cnopy nd light extinction my vry ccording to the shpe of the tree nd the density of the leves explined y higher LAI on lower prt of the cnopy, like suggested y Bongi nd Pllioti (1994). Most rditive trnsfer Mezghni et l. reserches relized on homogeneous cnopy re no suitle for forest tree nd fruit tree. Two nd three dimensionl chrcteriztion hve een used nd the tree grown hs een descried using ellipsoids, cones nd cylinders forms (Cutini et l., 1998; Gnis, 1997; Aris et l., 2007). Olive orchrds re complex system in which the min difficulties in modelling the flowfield nd light interception re linked to the sptil non-homogeneity of folige tree. Conclusion These results will e the fundmentl sis of olive pruning nd to estlish new intensive olive orchrds with fully developed cnopies which intercepted the mximum solr rdition. In Order to completely chrcterize the light distriution within the crows of trees trined to different systems (vse system, centrl leder, free form), more extensive studies must e conducted. However, further reserch should e crried out to study light interception in the whole crown form from sunrise to sunset ccording different vrieties nd tree density in the field ecuse of the different comintions (site, cultivr, density, seson ) References Aïchi Mezghni M Olive Vriety Suitility nd Trining System for Modern Olive Growing: Plnt Growth nd Yield Components. Editor: Antonell de Leonrdis, Virgin Olive oil: Production, composition, uses nd enefits for mn, Chpter 7, p Aris D, Clvo-Alvrdo J, Dohrenusch A Clirtion of LAI-2000 estimte lef Are index (LAI) nd ssessment of its reltionship with stnd productivity in six ntive nd introduced trees species in Cost Ric. Forest Ecology nd Mngement 247, Asner GP, Scurlock JMO, Hicke JA Glol synthesis of lef re index oservtions: implictions for ecologicl nd remote sensing studies. Glol. Ecologicl Biogeogrphy 12, Pge 64

6 Bongi G, Plliotti A Olive. In. B Schffer et PC Anderson (eds), Hndook of environmentl physiology of fruit crop, CRC Press Inc, USA p Bonhomme R, Chrtier P The interprettion nd utomtic mesurement of hemisphericl photogrphs to otin sunlit folige re nd frequency. Isrel Journl Agriculturl Reserch 22, Cutini A, Mtteucci G, Mugnozz GS Estimtion of lef re index with the Li-Cor LAI 2000 in deciduous forests. Forest Ecologicl Mngement 105, Gnis A Rdition trnsfer estimte in row cnnopy: simple procedure. Agriculturl nd Forest Meteorology 88, Pstor M, Humnes J Plnttion density experiments of non-irrigted olive groves in Andluci. Act horticulture 286, Pstor Munõz-Coo M, Hidlgo Moy JC, Veg Mcis V, Fereres Cstieel E Vriilidd gronomico y economico de ls plntciones superintensivs en Andluci. Journées d études reltives u développement de l oléiculture à huile. Mriscl MJ, Orgz F, Villloos FJ Modelling nd mesurement of rdition interception y olive cnopies. Agriculturl nd Forest Meteorology 100, Tomesi A Plnting systems, cnopy mngement nd mechnicl hrvesting. In : Recent dvnces in olive industry, Specil seminrs nd invited lectures. Oliveioteq, Novemer 2006, Mrsl, Mzr Del Vllo, Itly, Alcmo: Presso Cmpo pp Villloos FJ, Orgz F, Mteos L Non destructive mesurement of lef re in olive (Ole europe L.) trees using gp inversion method. Agriculturl nd Forest Meteorology 73, Pstor M Plnttion density. Proceedings of Interntionl Course F.A.O. on fertilistion nd intensifiction of olive cultivtion, Cordo, p Mezghni et l. Pge 65