CANOPY TRANSPIRATION RESPONSE TO ENVIRONMENTAL VARIATIONS IN PLATYCLADUS ORIENTALIS: PROPERTIES AND MODELLING

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1 Pak. J. Bot., 44(2): , CANOPY TRANSPIRATION RESPONSE TO ENVIRONMENTAL VARIATIONS IN PLATYCLADUS ORIENTALIS: PROPERTIES AND MODELLING LEI HAN 1,2, KANGNING HE 2*, XINGBO HU 2 AND DONG ZHANG 2 1 New Technology Application and Reearch Center, Ningxia Univerity, Yinchuan , China 2 College of Soil and Water Conervation, Beijing Foretry Univerity, Beijing , China * Correponding author huibaoervice@163.com; Tel:(+86) ; Fax: (+86) Abtract Regrowth of tall, dene foret conume more water, with the reult that catchment yield may decline and even oil deiccation occurred epecially in the emi-arid Loe Plateau of China. In thi tudy, meteorological meaurement combined with ap flow technique provided a low-cot option to tudy the rate of water uptake by individual tree of Platycladu orientali repone to environmental factor on a continuou bai. A erie of environmental control function: vapour preure deficit, olar radiation and air temperature were ued to characterize canopy tranpiration (E c ). A Jarvi-type model, modified to directly etimate the E c rather than canopy conductance, explained 89% of the variation oberved in E c. Cro validation how that thi model provided good prediction of canopy tranpiration for P. orientali. Such a methodology offer a reaonable etimation of water ue in the determination of water balance for land water reource planning, vegetation management and impact aement of rehabilitation. Introduction Tree planting and afforetation ha been a key project of oil and water conervation for ecological environment management on the Loe Plateau of China. Some reearcher have reported that regrowth of tall, dene foret conume more water, with the reult that catchment yield may decline and even oil deiccation occurred (Cornih & Vertey, 2001; Robert et al., 2001; Vertey et al., 2001; Li et al., 2008; Macfarlane et al., 2010). So how to evaluate water ue and requirement a well a the effect of increaing artificial foret cultivation on the hydrological cycle become a key iue for reearch. A i an important component of the water balance in foret, tranpiration of whole foret canopie ha been experimentally meaured in a wide range of environment, from boreal to tropical, uing different methodologie. Sap flow technique baed on thermal diipation probe (TDP) method ha been commonly ued to etimate tranpiration from different pecie or a ingle component of mixed vegetation (Granier, 1996; Lu et al., 2003; Rana et al., 2005; Oguntunde et al., 2007). Theoretically, for a well-coupled foret, where tranpiration i controlled by tomatal aperture in repone to meteorological change, E c can be calculated from g c and vapour preure deficit (VPD) ince E c =g c VPD (Whitehead, 1998; Whitley et al., 2008). If we aume a negligible effect of aerodynamic conductance on tranpiration (that i, aerodynamic conductance i much greater than g c ), then we can expre g c a a function of it driving environmental variable (Jarvi, 1976; Stewart,1988; Wright et al., 1995; Han et al., 2011): g c =k 1 f(vpd) f( R ) f(t a ), where k 1 repreent maximum tomatal conductance. Thi Jarvi-type model for g c require only three environmental variable and hort-term meaurement of ap flow and i much impler to fit (Harri et al., 2004; Bernier et al., 2006). In thi tudy, we ued a modified Jarvi-type model combined with ap flow method to directly model tree canopy tranpiration (E c ) pecifically rather than inverting the Penman-Monteith (P-M) equation to derive meaurement of canopy conductance (g c ) and then uing P-M again to etimate E c from g c a ha been applied in the pat (Lu et al., 2003; Oguntunde et al., 2007). The aim of thi tudy i to (1) invetigated how variation in the driving variable impact E c, (2) develop a model in E c for P. orientali which ha been widely planted in China, and (3) compare the predicted E c value (modelled E c ) uing the modified Jarvi-type model (ee below), with the oberved ap flow data (oberved E c ). Material and Method Study ite: The tudy wa conducted in a P. orientali plantation at Tuqiaogou waterhed of Fanghan County in Shanxi province of China (37 36 N, E, elevation 1200 m). The plot i characterized by continental monoon climate, and mean annual temperature ( ) wa 7.3 C and annual rainfall averaged 416mm, concentrated in the June September period with the oil texture within the plot a generally medium loam. The P. orientali tree (pacing of 1.5 m 4 m giving a denity of 1666 tree ha -1 ) etablihed in 1993 from four year old bare root eedling ha an average height of 6.5m and average trunk diameter of 6.2 cm. Baal area and diameter at breat height (DBH) of all tree were meaured in five replicate 20 m 20 m plot. Environmental variable: Solar radiation (R ), air temperature (T a ), relative humidity (RH), wind peed (u) and rainfall were recorded a 15 minute average with an automatic weather tation intalled about 200 m away from the plot. Volumetric oil water content (%) wa regularly meaured by oven drying method by 10 cm depth interval down to 100cm. Water ue by individual tree: The water tranpired by individual tree wa meaured by ap flow technique with the TDP method of Granier (1987). Five repreentative tree were elected to cover the range ize ditribution at the tand (mean tree height 6.5±0.2 m and apwood area

2 542 LEI HAN ET AL., 44.1±6.17 cm 2 ). Two cylindrical enor probe about 2 mm in diameter, each containing a copper-contantan thermocouple, were inerted in the apwood of the tree trunk with one probe about 10 cm above the other. The probe were intalled in the trunk at a point halfway between the oil urface and the lowet actively growing branch, then the trunk wa hielded with aluminium foil, to minimize the effect of thermal fluctuation on the meaurement (Lu et al., 2004). Tranpiration (E c, mm h - 1 ) of an individual tree wa calculated a: Aw E c = J Ac where J i the whole tree ap flux denity (cm -1 ), A w i the apwood area (cm 2 ) and A c i the projected canopy area (cm 2 ). Sap flow meaurement, ampled at 15-min interval in tep with the weather data, were made between 30 June [Day of Year (DOY) 181] and 16 (DOY 228) Augut Modeling: Canopy tranpiration wa modeled directly (E c mod, mm h -1 ) from function of vapour preure deficit (VPD, kpa), R and T a (Jarvi, 1976; Stewart, 1988; Whitley et al., 2009): mod E = E f ( VPD) f ( T ) f ( R ) (1) c c max a f ( VPD) k1vpd exp k2 2 f ( Ta ) exp{ k3( Ta Topt ) f ( R ) ( VPD) = (2) = } (3) R k 1000 R + k 4 = (4) 4 where E cmax i a theoretical maximum canopy tranpiration under optimal environmental and leaf condition. T opt i the optimum temperature limit to tranpiration. The function form (f, 0 f 1) for thi tudy were baed on thoe of Stewart (1988), Wright et al., (1995) and Niu et al., (2005). Parameter k 1 k 4 were optimized uing the Levenberg-Marquart algorithm (Marquardt, 1963). Root mean quare error (RMSE) wa ued to weighted the deviation between the ith experimental value (y i ) and the ith predicted value (ŷ i ) of E c. Where we expre the RMSE a: 1 ) RMSE = i n ( y i y ) 1/ 2 2 (5) Daily meaurement of ap flow were filtered to exclude hour when olar radiation wa zero (night) within Day with rainfall event were alo excluded to eliminate wet-canopy condition. To avoid circularity and to validate the elected model, the whole data wa divided into two group, covering the odd day (Databae A) and even day (Databae B) of meaurement repectively. The elected model wa then fitted eparately to each of the two group and cro-validated on each other. Thi type of validation procedure ha been decribed a robut and conitent (Stewart, 1988; Lu et al., 2003). Reult and Dicuion Soil moiture: A wa hown in Fig. 1, average volumetric oil moiture in the trial during the ap flow meaurement ranged from of 8.35% to 21.56%, and the SWC in root zone averaged 16.98% (the oil depth from 40cm to 80cm). Drought tre tudie conducted by He et al. (2003) and Tian et al., (2005) howed that the uitable oil moiture for P. orientali growing ranged from 9.88% to 13.21%, while the oil moiture to maintain the maximum of leaf tranpiration wa between 16% and 19%. Thi ugget that tree water ue during thi period wa not limited by oil water content. Bauerle et al., (2002) noted that when oil water wa extractable, meaured and modelled tranpiration wa mainly controlled by atmopheric demand. Fig. 1. Variation of the volumetric oil moiture in trial Canopy tranpiration: Normalized canopy tranpiration (E c / E cmax ) wa plotted againt the function of R, VPD and T a in Fig. 2. The functional form of the curve decribed by Eq.2~4 fitted to the experimental data repectively. The boundary curve howed a hyperbolic increae from zero to a maximum in E c with increaing R

3 CANOPY TRANSPIRATION RESPONSE TO ENVIRONMENTAL VARIATIONS IN PLATYCLADUS ORIENTALIS 543 (Fig. 2A). At low level of radiation, energy upply limit evaporation, but further increae in R, leaf toma cloed to avoid exceive water lo and prevent leaf water potential from falling to a dangerou level (Tyree & Sperry, 1988). Similar form to thee repone were noted by Oguntunde & van de Gieen (2005), Morri et al., (2006) and Whitley et al., (2008). Canopy tranpiration alo exhibit a linear increae repone to the increaing vapour preure deficit (VPD) at lower value (VPD < 1.2 kpa) (Fig. 2B). For the higher value of VPD ( kPa), water tranpired by individual tree howed a minimal decline a VPD increaed. Thi follow from the argument that tomatal cloure would more than offet the increaed evaporative demand (Jarvi, 1980; Pataki & Oren, 2000; Zahid et al., 2010). A reult hown in Fig. 2C, air temperature eemed to be reached near the threhold value of 25~27 C o that further increae in T a led to correponding decreae in canopy tranpiration. Thee trend may further confirm that high enitivity of P. orientali leave to changing atmopheric variation and hence the regulation of it tranpiration at the canopy level. Fig. 2. Normalied canopy tranpiration repone to (A) olar radiation (R ), (B) vapour preure deficit (VPD) and (C) air temperature (T a ). Modelled canopy tranpiration: Table 1 how the optimied parameter and their tandard error for the modified Jarvi-type model. The three tamatal control function of R, VPD and T a explained above 89% of variation in E c. The predicted maximal value for E c ranging from mm h -1 to mm h -1 i very cloe to but under the oberved maximal value of 0.11 mm h -1. Thee value were found to be low compared to 0.24 mm h -1 in citru (Oguntunde et al., 2007) and 0.13 mm h -1 in Eucommia ulmoide (Li et al., 2008). The optimum temperature for P. orientali tranpiration wa about 26.9~28.8 C compared to 28.5 C (Wright et al., 1995), and 25.5 C (Oguntunde et al., 2007). Predicted E c followed cloely thoe meaured on rainle day though the model may either lightly underpredict or over-etimate midday rate of tranpiration (Fig. 3). Thi could be conidered acceptable, a the predicted value were alo within the threhold of tandard error in oberved E c. The weighted mean for modelled water ue by individual tree wa 0.76mm d -1 and for meaured one it wa 0.78mm d -1. Thi may be connected to the fact that P. orientali preent a very high reitance to flow compared to everal other pecie.

4 544 LEI HAN ET AL., Table 1. Parameter from the optimization of the modified Jarvi model predicting canopy tranpiration for P. orientali for a weighted nonlinear leat quare regime. Parameter R 2 RMSE E cmax k 1 k 2 k 3 k 4 T opt Databae A value (n=229) S.E Databae B value (n=219) S.E All data value (n=448) S.E Fig. 3. Diurnal coure of modelled canopy tranpiration compared with oberved data (vertical bar are ±S.E. of the mean). Databae A and B were analyzed by cro-validation which ha been verified to be a more tringent tet of the model than electing random ubet (Lu et al., 2003; Han et al., 2011). The regreion in Fig. 4 howed good agreement (R 2 >0.86, P<0.001) between predicted and oberved E c for the two ubet. Comparing with the trend line of each dataet, ome catted point were motly on one ide of the line but not noticeable further away from it. Thi becaue the VPD and R fluctuated dramatically epecially when cloud increaed uddenly in certain time of day. Fig. 4. Cro validation between predicted and oberved canopy tranpiration in Databae A (olid line and cloed grey ymbol) and B (dotted line with open ymbol).

5 CANOPY TRANSPIRATION RESPONSE TO ENVIRONMENTAL VARIATIONS IN PLATYCLADUS ORIENTALIS 545 Concluion Thi tudy characterize the impact of main environmental variable on canopy water flux of P. orientali and a modified Jarvi-type model baed on a erie function of meterological factor ha been ued to directly etimate water tranpired by individual tree. Functional form of the modified Jarvi-type model i found uitable for predicting the canopy tranpiration to variation in vapour preure deficit, olar radiation and air temperature. Though there are ome uncertainty preent in the meaurement, thi parameterized model explain about 89% of the variation oberved in E c. Cro validation how that thi model work well with an acceptable level of error between oberved and modeled value. Acknowledgement Thi work wa upported by the 12th Five Scientific & Technological Sutaining Reearch Program of China (2011BAD38B05). Reference Bauerle, W.L., C.J. Pot, M.F. McLeod, J.B. Dudley and J.E. Toler Meaurement and modeling of the tranpiration of a temperate red maple container nurery. Agric. For. Meteorol., 114: Bernier, P.Y., P. Bartlett, T.A. Black and A. Barr Drought contraint on tranpiration and canopy conductance in mature apen and jack pine tand. Agric. For. Meteorol., 140: Cornih, P.M. and R.A. Vertey Foret age-induced change in evapotranpiration and water yield in a eucalypt foret. J. Hydrol., 242: Granier, A Evaluation of tranpiration in a Dougla-fir tand by mean of ap flow meaurement. Tree Phyiol., 3: Granier, A., R. Huc and S.T. Barigah Tranpiration of natural rain foret and it dependence on climatic factor. Agric. For. Meteorol., 78: Han, L., K.N. He, X.B. Hu, D. Zhang, J. Qin, M. Dong and A.C. Li Characteritic and modelling of canopy conductance and tranpiration of Platycladu orientali (L.) Franco in Loe Plateau of China. Afr. J. Agr. Re., 6: Harri, P.P., C. Huntingford, P.M. Coxb, J.H.C. Gaha and Y. Malhi Effect of oil moiture on canopy conductance of Amazonian rainforet. Agric. For. Meteorol., 122: He, K.N., G.C. Zhang, Y. Tian, C.Q. Shi and J.H. Song The uitable oil moiture condition for foret growth in catchment afforeatation in emi-arid region on Loe Plateau. Sci. Silvae Sinicae, 39: (in Chinee) Jarvi, P.G Stomatal repone to water tre in conifer. In: Adaptation of Plant to Water and High Temperature Stre. (Ed.): N.C. Turner and P.J. Kramer John Wiley and Son, New York, pp Jarvi, P.G The interpretation of the variation in leaf water potential and tomatal conductance found in canopie in the field. Philo. Tran. R. Soc. Lond., Ser. B., 273: Li, J., B. Chen, X.F. Li and Y.J. Zhao Effect of deep oil deiccation on artificial foretland in different vegetation zone on the Loe Plateau of China. Acta Ecol. Sinica, 28: Lu, P., L. Urban and P. Zhao Granier thermal diipation probe (TDP) method for meauring ap flow in tree: theory and practice. Acta Bot. Sinica, 46: Lu, P., I.A.M. Yunua, R.R. Walker and J. Muller Regulation of canopy conductance and tranpiration and their modeling in irrigated grapevine. Funct. Plant Biol., 30: Macfarlane, C., C. Bond, D.A. White, A.H. Grigg, G.N. Ogden and R. Silbertein Tranpiration and hydraulic trait of old and regrowth eucalypt foret in outhwetern Autralia. For. Ecol. Manage., 260: Marquardt, D.W An algorithm for leat quare etimation of non-linear parameter. J. Appl. Math., 11: Morri, J., J. Collopy and K. Mahmood Canopy conductance and water ue in Eucalyptu plantation. Pak. J. Bot., 38(5): Niu, H.S., R. Xu, Z.C. Zhang and Z.Z. Chen A Jarvi tomatal conductance model under conidering oil moiture condition. Chin. J. Ecol., 24: (in Chinee) Oguntunde, P.G. and N. van de Gieen Water flux meaurement and prediction in young cahew tree uing ap flow data. Hydrol. Proce., 19: Oguntunde, P.G., N. van de Gieen and H.H.G. Savenije Meaurement and modelling of tranpiration of a rain-fed citru orchard under ub-humid tropical condition. Agric. Water Manage., 87: Pataki, D.E., R. Oren and W.K. Smith Sap flux of cooccurring pecie in a wetern ubalpine foret during eaonal oil drought. Ecology. 81: Rana, G., N. Katerji and F. de Lorenzi Meaurement and modeling of evapotranpiration of irrigated citru orchard under Mediterranean condition. Agric. For. Meteorol., 128: Robert, S., R.A. Vertey and R. Grayon Tranpiration from Eucalyptu ieberi (L. Johnon) foret of different age. For. Ecol. Manage., 143: Stewart, J.B Modelling urface conductance of pine foret. Agric. For. Meteorol., 43: Tian, J.H., K.N. He, B.T. Wang, W.Q. Zhang and J. Yin Relationhip between tranpiration of Platycladu orientali and environmental factor in emi-arid region on Loe Plateau. J. Beijing For. Univ., 27: (in Chinee) Tyree, M.T. and J.S. Sperry Do woody plant operate near the point of catatrophic xylem dyfunction caued by dynamic water tre? Anwer from a model. Plant Phyiol., 16: Vertey, R.A., F.G.R. Waton and S.K. O Sullivan Factor determining relation between tand age and catchment water balance in mountain ah foret. For. Ecol. Manage., 143: Wright, I.R., A.O. Manzi and H.R. de Rocha Surface conductance of Amazonian pature: model application and calibration for canopy climate. Agric. For. Meteorol., 75: Whitley, R., M. Zeppel, N. Armtrong, C. Macinni-Ng, I. Yunua and D. Eamu A modified Jarvi-Stewart model for predicting tand-cale tranpiration of an Autralian native foret. Plant Soil, 305: Whitley, R., B. Medlyn, M. Zepple, C. Macinni-Ng and D. Eamu Comparing the Penman-Monteith equation and a modified Jarvi-Stewart model with an artificial neural network to etimate tand-cale tranpiration and canopy conductance. J. Hydrol., 373: Zahid, D.M., F. Shah and A. Majeed Planting Eucalyptu Camalduleni in arid environment i it ueful pecie under water deficit ytem? Pak. J. Bot., 42(3): (Received for publication 17 June 2010)