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Research ArticleEffects of Drought Frequency on Growth Performance andTranspiration of Young Black Locust (Robinia pseudoacacia L)

Dario Mantovani12 Maik Veste3 and Dirk Freese2

1 International Graduate School Brandenburg University of Technology Cottbus-Senftenberg Konrad-Wachsmann-Allee 603046 Cottbus Germany

2 Chair of Soil Protection and Recultivation Brandenburg University of Technology Cottbus-Senftenberg Konrad-Wachsmann-Allee 603046 Cottbus Germany

3 Centre for Energy Technology Brandenburg eV (CEBra) Friedlieb-Runge-Straszlige 3 03046 Cottbus Germany

Correspondence should be addressed to Dario Mantovani mantdar2gmailcom

Received 19 November 2013 Revised 28 January 2014 Accepted 28 January 2014 Published 17 March 2014

Academic Editor Kihachiro Kikuzawa

Copyright copy 2014 Dario Mantovani et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Black locust (Robinia pseudoacacia L) is a drought-tolerant fast growing tree which could be an alternative to the more commontree species used in short-rotation coppice on marginal land The plasticity of black locust in the form of ecophysiological andmorphological adaptations to drought is an important precondition for its successful growth in such areas However adaptationto drought stress is detrimental to primary production Furthermore the soil water availability condition of the initial stage ofdevelopment may have an impact on the tree resilience We aimed to investigate the effect of drought stress applied during theresprouting on the drought tolerance of the plant by examining the black locust growth patterns We exposed young trees inlysimeters to different cycles of drought The drought memory affected the plant growth performance and its drought tolerancethe plants resprouting under drought conditions were more drought tolerant than the well-watered ones Black locust toleratesdrastic soil water availability variations without altering its water use efficiency (257 g Lminus1) evaluated under drought stress Due toits constant water use efficiency and the high phenotypic plasticity black locust could become an important species to be cultivatedon marginal land

1 Introduction

Summer drought as observed during extreme events inCentral Europe in 2003 [1] is one of the major abioticstress factors that limit plant growth and have drastic effectson the ecosystem productivity The ongoing climate changeamplifies the interannual climate variability and changesthe seasonal distribution of rainfall in Central Europe [2]Within Central Europe particularly the southern parts ofBrandenburg and Poland will be highly vulnerable to climatechange and a decrease in summer precipitation is forecastedConsequently drought periods during the growth season areto be expected [3] In this region the reduced soil wateravailability (SWA) in combination with sandy soils has ledto negative effects on the productivity of the ecosystem [4]An integrated concept of active species selection and an

appropriate management of tree stands could mitigate theeffect of the climatic stress to a certain extent Therefore itis important to assess the plasticity of the species to droughtstress by understanding the plant response in terms of waterconsumption growth performance and production [5] Thisis particularly important for short-rotation coppice (SRC)systems where the primary production is driven mainly bythe SWA [6 7] Black locust (Robinia pseudoacacia L) as adrought tolerant species suitable for SRC can be grown evenon reclaimed post-mining sites where the edaphic conditionsare extreme [8] Various studies emphasize the black locustmorphological and ecophysiological adaptations in copingwith long-term drought stress [9ndash11] Hence the ecologicalstress memory defined by Walter et al [12] as any responseof a single plant after a stress experience which improves theresponse of the same plant towards future stress experiences

Hindawi Publishing CorporationInternational Journal of Forestry ResearchVolume 2014 Article ID 821891 11 pageshttpdxdoiorg1011552014821891

2 International Journal of Forestry Research

could be an important factor when evaluating the droughtstress tolerance of the species Depending on the droughtstress severity a reduction of the primary production dueto these morphological and physiological adjustments is tobe expected [13ndash15] Stomatal closure is a typical temporaryreaction to drought stress leading to a reduced CO

2

uptakeand finally influencing carbon budgets and growth perfor-mances [16 17] Besides physiological adjustments droughtstress occurring during the tree development induces mor-phological adaptations from the roots to the crown whichwill characterize the hydraulic architecture of the tree [18ndash23] As a consequence the transpiration of the plant will beinfluenced along with its tolerance to drought stress [18ndash20]Hence the recovering process after drought stress in termsof growth increment could be affected by the SWA at theinitial stage of resprouting In spite of the importance of thistopic for coppicing practices up to this date there is stilla considerable informational gap the effect of the droughtoccurring during the resprouting period on the drought toler-ance biomass production andwater use under drought stresshas not been investigated In our study we aimed to assessthe impact of drought cycles applied during the resproutingphase on the drought resilience of black locust trees Wedefined the physiological conditions in terms of plant waterstatus at which the growth performance is compromisedand analyzed the influence of drought applied during theresprouting phase on the hydraulic architecture of the treeevaluating the relation between root system and the totaltranspiring surfaceThe effect of the different root weight leafarea ratio was evaluated by analyzing (i) growth performance(ii) transpiration rate (iii) aboveground biomass productionand (iv) the water use efficiency under cyclic drought stressThe information gathered enlightened the importance ofblack locust as an appropriate tree for marginal land and thestrong implication that the SWAduring the resprouting phasehas on the later drought tolerance and productivity of thespecies

2 Material and Methods

21 Plants and Drought Stress Treatment The study wascarried out with three-year-old black locust trees in alysimeter experiment under a light transmissive rain-outshelter arranged at the Brandenburg University of Tech-nology Cottbus-Senftenberg The water was supplied solelyby an automatic irrigation system The plant material wascollected from a short-rotation plantation in the postminingarea of Welzow-Sud Brandenburg Germany (N 51∘3610158401410158401015840E 14∘1910158405110158401015840) approximately 25 km south from the lysimeterfacility The climate at the collection site and at the lysimeterfacility is comparable It is a transition from the Atlanticto the continental climate with mean annual rainfall of556mm and mean annual temperature of 93∘C (1951ndash2003DeutscherWetterdienst) During the experiment the highestair temperature in Cottbus was reached in August 2012with more than 365∘C The monthly mean temperature was+07∘C above the long-term average while the early summerwas minus05∘C (June) and minus03∘C (July) colder than the average

However extreme conditions with air temperatures above30∘C and even 35∘C as observed in 2012 are common inBrandenburg All the selected trees presented a comparablecrown architecture with three main branches (mean radiusof 106 plusmn 19 cm) connected to the trunk (mean radius of134 plusmn 19 cm height approx 30 cm) At the beginning ofthe experiment all the primary branches were cut backat 10 cm from the trunk After a period of establishment(March 20 to June 1 2012) during which the plants were wellwatered the drought cycle experiment started on June 1 untilOctober 11 with two treatments short-term drought stress(STS) and long-term drought stress (LTS) each executed inthree replicas (119899 = 3) In our context we defined droughtstress as a condition where the mean soil water content(120579) was maintained at values of 7 which is the value atwhich the growth rate drastically decreases to values closeto zero The well-watered condition instead correspondedto the hydrostatic state of the lysimeter where the mean ofthe 120579 was set at 20 with full availability of water Sinceall treatments started developing new leaves during the lastweek of May we considered the resprouting phase the periodfrom the 23rd to the 26th week of the year (WOY) Thecycling of drought and full availability of water was scheduledas follows the LTS plants experienced drought conditionsthroughout the four weeks of the resprouting period Insteadthe STS plants were exposed only to one week of drought(24th WOY) during the same period After the resproutingphase three weeks of well-watered conditions followed forboth treatments From the 30th WOY on both treatmentswere exposed to drought stress for two weeks From the33rd WOY until the end of the experiment (41st WOY)the STS plants were subjected to short-term drought stress(one week of drought and two well-watered ones) while theLTS plants were subjected to long-term drought stress (twoweeks of drought stress followed by oneweek of well-wateredcondition)

22 Lysimeter and Soil Water Status In order to control theSWA and to calculate the water budget the plants were grownin lysimeters (50 cm diameter 50 cm height) under a lighttransmissive rain-out shelter [11] The daily transpiration wascalculated by the difference between the measured irrigationand the sum of the estimated daily water storage variationand the leachate collected Evaporation from bare soil wasminimized by covering the soil with a double leaflet Tofacilitate the infiltration rate the sandy loam soil column wasfilled at bulk density 13 kgmminus3 The soil relatively low inorganic carbon (13) and total nitrogen (008) presentedthe oxalate-extractable Al Fe and Mn content values of065 153 and 008mg gminus1 respectivelyThe irrigation systemwas automatically controlled by a data logger (GP1 Delta-TDevices Cambridge UK) and the water was dispensed fromfour drippers per lysimeterThe volume of water was suppliedin relation to the volumetric soil water content measuredat 20 cm depth by a frequency domain reflectometry probe(SM-200 Soil Moisture Sensor Delta-T Devices CambridgeUK) To evaluate the storage variation of the weekly waterbudget the 120579 was measured at four depths (10 20 30 and

International Journal of Forestry Research 3

Soil moisture (vol-)

Soil matric potentialPlant water potential

Plan

t wat

er p

oten

tial (

MPa

)

Soil

mat

ric p

oten

tial (

MPa

)

00

minus05

minus10

minus15

minus206 8 10 12 14 16 18 20 22

000

minus005

minus010

minus015

minus020

Figure 1 Predawn leaf water potential and soil matric potential inrelation to the soil moisture and soil water retention curve

40 cm) with a profile probe (PR24w-02 Delta-T DevicesCambridge UK) The climatic variables air temperature andrelative humidity weremonitored on an hourly basis by usingthermistor-hygrometers (HC2-S Rotronic AG BassersdorfGermany) The vapor pressure deficit (VPD) values werecalculated for the daytime by the air temperature and relativehumidity recorded from 0900 HR to 1800 HR local summertime

23 Leaf Water Potential We linked the physiological con-dition of the trees in terms of plant water status to thegrowth rate by measuring the leaf water potential (Ψ

119871

) atdifferent soil moisture conditions The leaf water potentialwas measured at predawn time on three fully developedleaves for each tree by using the Scholander pressure chamber(Plant Water Status Console 3000 Soilmoisture Inc SantaBarbara CA USA) after Veste et al [24] The water potentialof the distal part of the rachis approximately 10 cm completedwith leaflets was measured immediately after the excisionWe linked the Ψ

119871

to the SWA by using the soil waterretention curve of the lysimeter soil column after Mantovaniet al [11] to convert the soil 120579 values read by the sensorsinto soil matric potential (Ψ

119878

) values (MPa) (Figure 1) Thecorrelations between Ψ

119878

and Ψ119871

and between Ψ119871

and 120579 aresignificant with a coefficient of correlation of minus0749 andminus0757 respectively (Figure 1)

Having this way both variables expressed in the same unit(MPa) we used the linear relation (Ψ

119871

= 9013 lowast Ψ

119878

1199032 =086) described in Figure 2 to set the indirect plant-basedirrigation control and monitoring system

24 Growth Rate and Biomass Production The response todrought stress in terms of growth increment throughout thevegetation period was evaluated on a different time scale byusing dendrometers (DD-S Ecomatik Dachau Germany)and a caliper The dendrometers were installed around thetrunk of each plant at 20 cm height from the soil and theradial variations were recorded daily at dawn time 0500HR to avoid bias measurements due to excessive trunkshrinkage Tominimize the effect of the different initial trunk

Plan

t wat

er p

oten

tial (

MPa

)

Soil matric potential (MPa)

00

minus05

minus10

minus15

minus20

minus020 minus015 minus010 minus005 000

Figure 2 Relation between the measured predawn leaf waterpotential and the calculated soil matric potential

radii the data series was compared in relative terms as apercentage of the growth The monthly growth rate insteadwas evaluated by measuring the trunk radius at 25 cm heightfrom the soil with the caliper and the main branch at approx-imately 10 cm from the trunk Also the monthly growth rateis expressed as a percentage of the growth Furthermorethe data series is plotted after normalization The biomassproduction wasmeasured at the end of the vegetation periodThe total aboveground biomass (secondary branches andleaves) was harvested before the defoliation (October 112012) and oven-dried separately at 65∘C until a constantdry weight was reached The gravimetric increment of thetrunk and the primary brancheswas estimated bymultiplyingthe seasonal volumetric increment recorded throughout theexperiment making use of the calculated specific weightof the black locust dry wood (076 g cmminus3) estimated fromthe secondary branches The water use efficiency (WUE)under different drought stress durations was calculated afterthe harvest by the ratio between the dry total abovegroundbiomass produced during the vegetation period and thewater used On the other hand the economical water useefficiency (EWUE) under different drought stress durationswas calculated considering only the dry aboveground woodproduction

25 Leaf Area and Root Vertical Distribution The total leafarea (m2) for a single tree was calculated at the harvest bymultiplying the black locust specific leaf area (gmminus2) by theweight of the total dry leaves collected from each tree Thespecific leaf area was calculated from the ratio between themeasured area of 10 fully developed single leaves for each treeand their single dry weight

In order to evaluate the vertical spatial distribution of theroot weight without the stump root samplingwas performedat 5 cm 20 cm and 40 cm soil depth at the end of theexperiment (October 11 2012) We used six steal rings ofknown volume (5 cm radius times 10 cm height) at each soildepth To homogenize the operation three samples werecollected at 10 cm from the center of the lysimeter and threesamples at 10 cm from the lysimeter wall for each layer Allthe roots contained in the rings were separated and the soilwas removed from the roots with a brush The roots were


0

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(∘C)

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(b)

Figure 3 Mean of the daily temperature and relative humiditymeasured on a hourly basis calculated from 0900 HR to 1800 HRrecorded throughout the vegetation period

washed carefully in a dish of water to remove any residual soilSubsequently they were oven-dried at 65∘C till steady weightThe total root biomass (g) for each depth was determined byweighing the roots of each sample and multiplying the meanof the root weight density (g cm3) by the soil volume of eachdepth amounting to 32773 cm3

26 Statistical Analysis The nonparametric Spearman rhocorrelation (119875 lt 005) was applied to correlate (i) the weeklywater use growth rate and the VPD (ii) the Ψ

119878

and theΨ

119871

and (iii) the Ψ119871

and the 120579 The non-parametric analysisMann-Whitney 119880 test (119875 lt 005) was performed to compare(i) the mean weekly growth rate (ii) the cumulative wateruse (iii) the trunk and branch radial increments (iv) theaboveground biomass production (v) the root weight verticaldistribution (vi) the total leaf area and (vii) the WUE andthe EWUE under drought stress between and within thetreatments All the analyses were executed by using the IBMSPSS version 21 (SPSS Inc Chicago IL USA)

0

10

20

30

40

50

60

IrrigationTranspiration

StorageLeachate

Wat

er (L

)

minus10

22 24 26 28 30 32 34 36 38 40 42Week of the year

(a)

22 24 26 28 30 32 34 36 38 40 42Week of the year

0

10

20

30

40

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Wat

er (L

)

minus10


StorageLeachate

(b)

Figure 4Mean of theweekly experimental water balance calculatedthroughout the vegetation period

3 Results

31 Water Use The mean of the daily air temperature andrelative humidity recorded during the vegetation period isshown in Figure 3 During the vegetation period for 18 daysthe mean of the daily temperature was above 30∘C and 7days above 34∘C with a peak of 365∘C in August The lastday with a temperature 30∘C was September 10 After thatthe temperature slowly decreased till reaching the minimumvalues of 125∘C at the end of the experiment

In order to calculate the weekly transpiration the exper-imental water balance was performed (Figure 4) During theperiods when the plants were well watered the leachate wasminimized by maintaining the soil column at the hydrostaticstate in order to avoid excessive soil particle translocationDuring the transition phase from well-watered to droughtcondition the irrigation was stopped and the plants used thewater stored into the soil till the predefined value of 7 wasreached On the other hand during the transition phase fromdrought condition to well watered the irrigation supplied


0

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mul

ativ

e tra

nspi

ratio

n (L

)

22 24 26 28 30 32 34 36 38 40 42Week of the year

STSLTS

VPD

VPD

(kPa

Paminus1)

(a)

0

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Wee

kly

trans

pira

tion

(L)

22 24 26 28 30 32 34 36 38 40 42Week of the year

000

minus010

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Soil

mat

ric p

oten

tial (

MPa

)

Matric potentialWater use

(b)

0

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22 24 26 28 30 32 34 36 38 40 42Week of the year

Wee

kly

trans

pira

tion

(L)

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa

)Matric potentialWater use

(c)

Figure 5 (a) Mean and standard deviation of the weekly vapor pressure deficit and cumulative water use (b) short-term stress treatmentmean and standard deviation of the weekly water use and mean of the soil matric potential and (c) long-term stress treatment mean andstandard deviation of the weekly water use and mean of the soil matric potential lowastDrought stress periods are marked with a black rectanglebeneath the bars

additional water to recharge the storage till the predefinedvalue of 20 was reached

The mean transpiration from the LTS treatment duringthe vegetation period amounted to 2600 plusmn 76 L corre-sponding to 57 of the water used by the STS treatment(4568 plusmn 253 L) (Figure 5(a)) The mean of the weekly wateruse of the STS treatment was more affected by the meanof the weekly VPD as compared to the LTS treatmentThe correlation was significant for both treatments withcoefficients of 0680 and 0499 for STS and LTS respectivelyFrom the analysis of the weekly water balance we canvisualize the different plant responses to the SWA variationin terms of water use (Figures 5(b) and 5(c)) During the firstfour weeks of our investigation (WOY 23ndash26) the LTS wateruse was only 26 compared to the STS For the followingthree weeks (WOY 27 28 and 29) the trees were alreadydifferentiated and the LTS used only 50 of the water usedby the STS plantsWhen imposing the drought regime (WOY30 and 31) both treatments reduced their water use Howeverthe STS still transpired 52 more water than the LTS

After the drought period (WOY 32) the plants of bothtreatments recovered quickly and the water use rose up by50 and 74 for the STS and LTS respectively DuringWOY 33 both treatments drastically dropped their waterconsumption to values comparable to the values recordedduring the previous phase of drought stress (WOY 31) TheSTS trees did not recover their functions fully since thewater consumption increased only by 14 (WOY 34) andwasfollowed by a further decrease of 25 (WOY 35) During thesubsequent stress period (WOY 36) defoliation started andthe water consumption was reduced by 34 not to recoveranymore till it reached the minimum mean weekly value of69 plusmn 03 L during the last week of the investigation (WOY41) The LTS instead did not change its water consumptionsubstantially during the last two drought stress cycles tillreaching the minimummean weekly value of 79 L

32 Growth The correlation between the mean weekly rel-ative trunk radial increment and the mean weekly Ψ

119871

was


0

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01

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04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(a)

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ive t

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m)

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kly

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k in

crem

ent()

DailyWeekly

(b)

5

10

15

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t()

STSLTS

(c)

Figure 6 Mean daily trunk increment and mean standard variation of the weekly relative trunk increment (a) short-term stress (b) long-term stress and (c) mean cumulative relative trunk increase of STS and LTS

not significantThe STS treatment decreased the trunk radialincrement by 58 after WOY 24 and only recovered slowlybefore the following drought stress (WOY 28) (Figure 6(a))The mean LTS radial increment (Figure 6(b)) after the stress(WOY 23ndash26) on the other hand increased dramatically by119 and kept on increasing for the following three weeks(WOY 27 28 and 29) After one week of stress (WOY 30) wehad a drastic reduction of the mean weekly radial incrementof 72 and 61 for the STS and LTS respectively Howeverduring the second week of stress (WOY 31) where the meanweekly VPD reached values of 293 kPa Paminus1 the mean trunkradial increment increased by 26 and 36 for the STSand LTS respectively By rewatering (WOY 32) the plantsof both treatments recovered The mean of the STS trunkradial increment increased by 60 while the LTS increasedby 48 During the third drought stress period (WOY 33)the mean of the STS trunk radial increment decreased andthe plants stopped growing altogether in WOY 36The meanof the LTS trunk radial increment rate instead still increasedby 29 after the third drought stress term (WOY 33 and 34)and decreased slowly till the end of the experiment (WOY41) with the minimum weekly values of 0015 The effect

of the VPD on the mean weekly radial increment measuredby dendrometers was more incisive for the STS than the LTStreatments with a coefficient of correlation of 0619 and 0548respectively (Figure 6(c))

Analyzing the mean water use calculated during variousphases of growth the difference between the LTS and STSdecreased from60during the first period (WOY23 to 27) to7 during the last period (WOY 35 to 41) (Figure 7(a)) Thefrequency of the drought stress neither significantly affectedthe mean primary branch radial increment measured withthe caliper (Figure 7(b)) nor was a significant differencefound between the treatments by normalizing the dataset(Figure 7(c))

33 Root Vertical Distribution and Total Leaf Area Themeanof the total root biomass production was not significantlydifferent between the treatments however the LTS mean ofthe root weight (3408 g) was 13more compared to the rootweight of the STS treatment (2984 g) For both treatments themean of the root weight at 5 cm was significantly differentcompared to the mean root weight estimated at 20 and 40 cm


00

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Week of the year

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27 32 37 42

STSLTS

Wat

er u

se (L

)N

orm

aliz

ed ra

dial

incr

emen

t Radi

al in

crem

ent (

)

minus05

minus10

minus15

22 27 32 37 42

STS LTS(a)

(b) (c)

STSLTS

Figure 7 (a) Mean weekly water use and (b) mean and standarddeviation of the primary branches relative radial increments mea-sured with caliper and (c) mean primary branch radial incrementsnormalized measured with caliper

depth The portion of the root developed at 5 cm depth was66 and 74 of the total for the STS and LTS treatmentrespectively (Figure 8)

Notwithstanding the fact that the difference between thetreatments in terms of total leaf area was not significant(Figure 9(a)) the estimated mean of the LTS total leaf area(62m2) was 17 higher than the mean of the STS total leafarea (52m2) The mean of the ratio root weight leaf areawas significantly different between the treatments being forSTS (336) only 31 compared to the LTS treatment (1064)(Figure 9(b))

34 Production The total dry aboveground biomass pro-duced during the vegetation period was comparable betweenthe treatments (Figure 10(a)) However the mean of the STSdry aboveground biomass amounted to 11415 plusmn 1352 gwhich was 36 more than with the LTS production (7302 plusmn766 g) The mean STS dry wood production amounted to8214 plusmn 398 g which was 44 higher than the LTS drywood production (4620 plusmn 711 g) (Figure 10(a)) The STStreatments produced the higher amount of abovegroundbiomass even though its branch radial increment was lowerthan the one of the LTS This incongruence is due to

Dep

th (c

m)

Dry weight (g)

STSLTS

aa

bb

b

b

0 50 100 150 200 250 300 350

5

20

40

Figure 8 Mean and standard deviation of the root weight at 5 20and 40 cm depth lowastNonparametric analysis Mann-Whitney 119880 testlowastDifferent letters indicate significant difference (119875 lt 005)

the branch radius dimension of the two treatmentsThemeanprimary branch radius of the LTS at the beginning of theexperiment amounted only to 78 compared to the STSIn terms of a comparable relative growth we have a moresubstantial absolute increase of biomassThe leaf wood ratiowas 041 for the STS and 059 for the LTS treatment TheWUE of the LTS was slightly higher compared to the STSbut the difference was not significant between the treatments(Figure 10(b))

The coefficient of correlations between water use and drytotal biomass (0997) and water use and dry wood (0928)was significant For both the relation is linear the WUE andthe EWUE under drought condition amounted of 257 g Lminus1(1199032 = 084) and 179 g Lminus1 (1199032 = 099) respectively (Figure 11)

4 Discussion

41 Leaf Water Potential and Growth The severity of thedrought stress is tightly related to the soil characteristicsrather than the absolute values of the 120579 Therefore theΨ

119871

is effective as a drought stress indicator to evaluate theplant sensitivity to the reduction of the soil water availability[24ndash27] Unlike indirect methods (eg soil moisture or soilmatric potentialmeasurements) a plant-based directmethodpresents the advantage of evaluating the true water status ofthe plant rather than the soil conditions Under the simulatedsoil moisture conditions in the lysimeter the tree growth wasnot influenced by the plant water status and no noteworthyrelation between the mean of the weekly growth increase andthe mean of the weekly Ψ

119871

could be found

42 Water Use Black locust is a ring-porous tree withwide early wood pores and if watered well it demonstrateshigh water consumption as generally recorded for treeswith a comparable hydraulic architecture arrangement [28]However black locust demonstrated a high plasticity sincethe species can cope with a wide range of environmental con-ditions [10 29] As the water availability decreases stomatal


a

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tal l

eaf a

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TreatmentLTS STS

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a

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200

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Root

wei

ght

leaf

area

(b)

Figure 9 Mean and standard deviation of the (a) total leaf area and (b) root weightleaf area ratio at 5 20 and 40 cm depth lowastNon parametricanalysis Mann-Whitney 119880-Test lowastDifferent letters indicate significant difference (119901 lt 005)

LTS STSTreatment

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Lminus1)

(b)

Figure 10 (a) Mean and standard deviation of the above ground dry total biomass and dry wood biomass produced during the vegetationperiod (b) mean and standard deviation of the water use efficiency under different drought stress duration lowastNonparametric analysis Mann-Whitney 119880 test lowastDifferent letters indicate significant difference (119875 lt 005)


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Figure 11 Water use efficiency under different drought stressdurations for the dry wood and the dry total aboveground biomass

regulation takes place in order to minimize the transpirationat the expense of the photosynthetic carbon gain [30] Ifthe stress is protracted physiological adjustments [13 3132] and hydraulic architecture acclimation occur [18ndash20 2223] in order to maintain the functionality of the vascularsystem [33 34] As found in our studies morphologicaladaptations occurred in response to the induced droughtstress Due to the lower total leaf area the LTS treatmentresulted to be more tolerant to drought stress A higher ratioroot weight total leaf area calculated for LTS enhanced itsefficiency in using the water resources during the droughtstress periods Furthermore due to the reduction of the totalleaf area its potential transpiration decreased reducing thewater loss during the days with relatively high VPD andlimited water availability As a matter of fact the LTS plantsthat resprouted under water constraint after the winter weremore tolerant to the imposed drought stress extreme heatconditions in August 2012 than the STS plants Also for otherbroad leaf species such as Fagus sylvatica it has been foundthat the previous summer drought stress had effects on thetranspiration and photosynthesis of the following years andinfluenced the growth performance [35] On the other handthe STS underwent only temporary adjustments to cope withthe short-term drought stress applied during the resproutingphase The plants evidently acclimatized to well-wateredconditions in terms of potential transpiring surface ratherthan through the xylem hydraulic capacity differentiation[33] demonstrated by the higher water consumption alreadyat the early stages A larger transpiring leaf surface meanshigher potential transpiration which is beneficial only whenthe water supply is sufficient However by reducing the soilwater availability or increasing the VPD stomatal regulationtakes place [10] and if the stress persists a reduction of thetranspiring surface occurs to minimize the embolism hazard[36]

43 Growth Increment and Biomass Production The soilwater availability reduction at the initial stage of the plantdevelopment was revealed to be a critical factor to enhance

the ability for recovery after subsequent drought stressas reported in previous studies [23 37] Higher biomassproduction was characterized by higher water consumptionindependent of the growth rate and the drought stressduration The WUE value of 256 g Lminus1 was calculated forblack locust under drought stress this value lying withinthe same range of the typical values estimated for trees suchas Populus and Salix growing in temperate climate zonesnamely between 142 and 666 g Lminus1 [38ndash41] Therefore thelink between the drought stress transpiration and primaryproduction is clear independently from the drought stressfrequency and duration the primary production is directlyproportional to the water used

5 Conclusions

The experiment emphasized the importance of the combi-nation of preconditions and drought cycles on the droughttolerance of Robinia pseudoacacia L Prestressed trees havealready a lower total leaf area and therefore lower waterconsumption Under increased transpiration demands withincreasing summer temperature they tolerate the applieddrought stress better than the STS with a larger leaf area Inthe STS trees the potential water demand is higher than thesoil water availability The water imbalance in combinationwith the high temperatures leads to a drastic leaf fall andfully stops of the growth under such conditions A moreextended root system together with the reduction of thetotal leaf area as an adaptive strategy appears to be effectivein order to enhance the drought tolerance of black locustHowever its growth performance is strongly affected by thesoil water availability The initial conditions of resproutingplay a central role in defining the recovery processes afterdrought stress which is of fundamental importance for thegrowth performance of black locust on marginal lands at theedges of its distribution area in Central Europe where wateris a limiting factor and summer droughts and temperaturesabove 30∘C occur This has important implication for themanagement of short-rotation forestry systems The highplasticity of Robinia and its recovery potential after stressmakes the tree species relevant for the production of biomassas raw material in the drier regions of Central and EasternEurope

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] P Ciais M Reichstein N Viovy et al ldquoEurope-wide reductionin primary productivity caused by the heat and drought in2003rdquo Nature vol 437 no 7058 pp 529ndash533 2005

[2] U Cubasch and C Kadow ldquoGlobal climate change and aspectsof regional climate change in the Berlin-Brandenburg regionrdquoErde vol 142 no 1-2 pp 3ndash20 2011

[3] N Schaller I Mahlstein J Cermak and R Knutti ldquoAnalyzingprecipitation projections a comparison of different approaches


to climatemodel evaluationrdquo Journal of Geophysical Research DAtmospheres vol 116 no 10 Article ID D10118 pp 1984ndash20122011

[4] A Holsten T Vetter K Vohland and V Krysanova ldquoImpact ofclimate change on soil moisture dynamics in Brandenburg witha focus on nature conservation areasrdquo Ecological Modelling vol220 no 17 pp 2076ndash2087 2009

[5] R Monclus E Dreyer M Villar et al ldquoImpact of drought onproductivity andwater use efficiency in 29 genotypes of Populusdeltoides x Populus nigrardquo New Phytologist vol 169 no 4 pp765ndash777 2006

[6] E Sevigne C M Gasol F Brun et al ldquoWater and energyconsumption of Populus spp bioenergy systems a case study inSouthern Europerdquo Renewable and Sustainable Energy Reviewsvol 15 no 2 pp 1133ndash1140 2011

[7] R S Zalesny D M Donner D R Coyle and W L HeadleeldquoAn approach for siting poplar energy production systems toincrease productivity and associated ecosystem servicesrdquo ForestEcology and Management vol 284 pp 45ndash58 2012

[8] H Grunewald C Bohm A Quinkenstein P GrundmannJ Eberts and G von Wuhlisch ldquoRobinia pseudoacacia L alesser known tree species for biomass productionrdquo BioenergyResearch vol 2 no 3 pp 123ndash133 2009

[9] F Xu W Guo W Xu Y Wei and R Wang ldquoLeaf morphologycorrelates with water and light availability what consequencesfor simple and compound leavesrdquo Progress in Natural Sciencevol 19 no 12 pp 1789ndash1798 2009

[10] M Veste and W U Kriebitzsch ldquoInfluence of drought stresson photosynthesis transpiration and growth of juvenile blacklocust (Robinia pseudoacacia L)rdquo Forstarchiv vol 84 no 2 pp35ndash42 2013

[11] D Mantovani M Veste A Badorreck and D Freese ldquoEvalua-tion of fast growing tree water use under different soil moistureregimes using wick lysimetersrdquo iForest vol 6 pp 190ndash200 2013

[12] JWalter A Jentsch C Beierkuhnlein and J Kreyling ldquoEcolog-ical stressmemory and cross stress tolerance in plants in the faceof climate extremesrdquo Environmental and Experimental Botanyvol 94 pp 3ndash8 2012

[13] H Lambers F S Chapin III and T L Pons Plant PhysiologicalEcology Springer New York NY USA 1998

[14] S Leuzinger G Zotz R Asshoff and C Korner ldquoResponses ofdeciduous forest trees to severe drought inCentral EuroperdquoTreePhysiology vol 25 no 6 pp 641ndash650 2005

[15] N Breda R Huc A Granier and E Dreyer ldquoTemperateforest trees and stands under severe drought a review ofecophysiological responses adaptation processes and long-term consequencesrdquo Annals of Forest Science vol 63 no 6 pp625ndash644 2006

[16] K J Bradford and T C Hsiao ldquoPhysiological responses tomoderate water stressrdquo in Physiological Plant Ecology O LLange P S Nobel B Osmond and H Ziegler Eds vol 2 pp263ndash324 Springer Berlin Germany 1982

[17] H Cochard L Coll X Le Roux and T Ameglio ldquoUnravelingthe effects of plant hydraulics on stomatal closure during waterstress in walnutrdquo Plant Physiology vol 128 no 1 pp 282ndash2902002

[18] M T Tyree and FW Ewers ldquoThe hydraulic architecture of treesand other woody plantsrdquo New Phytologist vol 119 no 3 pp345ndash360 1991

[19] H Cochard N Breda A Granier and G Aussenac ldquoVulnera-bility to air embolism of three European oak species (Quercus

petraea (Matt) Liebl Q pubescens Willd Q robur L)rdquo Annalesdes Sciences Forestieres vol 49 no 3 pp 225ndash233 1992

[20] J A Jarbeau F W Ewers and S D Davis ldquoThe mechanismof water-stress-induced embolism in two species of chaparralshrubsrdquo Plant Cell and Environment vol 18 no 2 pp 189ndash1961995

[21] C Lovisolo and A Schubert ldquoEffects of water stress on vesselsize and xylem hydraulic conductivity in Vitis vinifera LrdquoJournal of Experimental Botany vol 49 no 321 pp 693ndash7001998

[22] M Pigliucci Phenotypic Plasticity Beyond Nature and NurtureJohn Hopkins University Press Baltimore Md USA 2001

[23] G S Newman M A Arthur and R N Muller ldquoAbove- andbelowground net primary production in a temperate mixeddeciduous forestrdquo Ecosystems vol 9 no 3 pp 317ndash329 2006

[24] MVesteM Staudinger andMKuppers ldquoSpatial and temporalvariability of soil water in drylands plant water potential as adiagnostic toolrdquo Forestry Studies in China vol 10 no 2 pp 74ndash80 2008

[25] N Z Saliendra J S Sperry and J P Comstock ldquoInfluence ofleaf water status on stomatal response to humidity hydraulicconductance and soil drought in Betula occidentalisrdquo Plantavol 196 no 2 pp 357ndash366 1995

[26] L Donovan M Linton and J Richards ldquoPredawn plantwater potential does not necessarily equilibrate with soil waterpotential under well-watered conditionsrdquo Oecologia vol 129no 3 pp 328ndash335 2001

[27] A Galle P Haldimann and U Feller ldquoPhotosynthetic perfor-mance and water relations in young pubescent oak (Quercuspubescens) trees during drought stress and recoveryrdquo NewPhytologist vol 174 no 4 pp 799ndash810 2007

[28] M D Abrams ldquoAdaptations and responses to drought inQuercus species of North Americardquo Tree Physiology vol 7 pp227ndash238 1990

[29] F Xu W Guo R Wang W Xu N Du and Y WangldquoLeaf movement and photosynthetic plasticity of black locust(Robinia pseudoacacia) alleviate stress under different light andwater conditionsrdquo Acta Physiologiae Plantarum vol 31 no 3pp 553ndash563 2009

[30] J S Sperry ldquoHydraulic constraints on plant gas exchangerdquoAgricultural and Forest Meteorology vol 104 no 1 pp 13ndash232000

[31] H J Bohnert ldquoWhat makes desiccation tolerablerdquo GenomeBiology vol 1 no 2 pp 15ndash16 2000

[32] S Munne-Bosch and L Alegre ldquoChanges in carotenoidstocopherols and diterpenes during drought and recovery andthe biological significance of chlorophyll loss in Rosmarinusofficinalis plantsrdquo Planta vol 210 no 6 pp 925ndash931 2000

[33] D L Shumway K C Steiner and M D Abrams ldquoEffect ofdrought stress on hydraulic architecture of seedlings from fivepopulation of green ashrdquo Canadian Journal of Botany vol 69pp 2158ndash2164 1991

[34] L Poorter I McDonald A Alarcon et al ldquoThe importanceof wood traits and hydraulic conductance for the performanceand life history strategies of 42 rainforest tree speciesrdquo NewPhytologist vol 185 no 2 pp 481ndash492 2010

[35] W U Kriebitzsch andM Veste ldquoBedeutung trockener Sommerfur die Photosynthese und Transpiration von verschiedenenHerkunften der Rot-Buche (Fagus sylvatica L)rdquo Landbauforschvol 62 no 4 pp 193ndash209 2012


[36] R Tognetti A Longobucco and A Raschi ldquoVulnerability ofxylem to embolism in relation to plant hydraulic resistancein Quercus pubescens and Quercus ilex co-occurring in aMediterranean coppice stand in central Italyrdquo New Phytologistvol 139 no 3 pp 437ndash447 1998

[37] T J A Bruce M C Matthes J A Napier and J A PickettldquoStressful ldquomemoriesrdquo of plants evidence and possible mech-anismsrdquo Plant Science vol 173 no 6 pp 603ndash608 2007

[38] H S Grip S Halldin A Lindroth and G Persson ldquoEvap-otranspiration from a willow stand on wetlandrdquo Ecology andManagement of Forest Biomass Production Systems vol 15 pp47ndash61 1984

[39] A Lindroth T Verwijst and S Halldin ldquoWater-use efficiencyof willow variation with season humidity and biomass alloca-tionrdquo Journal of Hydrology vol 156 no 1ndash4 pp 1ndash19 1994

[40] C Yin X Wang B Duan J Luo and C Li ldquoEarly growthdry matter allocation and water use efficiency of two sympatricPopulus species as affected by water stressrdquo Environmental andExperimental Botany vol 53 no 3 pp 315ndash322 2005

[41] Z-S Liang J-W Yang H-B Shao and R-L Han ldquoInves-tigation on water consumption characteristics and water useefficiency of poplar under soil water deficits on the LoessPlateaurdquo Colloids and Surfaces B Biointerfaces vol 53 no 1 pp23ndash28 2006

Submit your manuscripts athttpwwwhindawicom

Forestry ResearchInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Environmental and Public Health

Journal of



EcosystemsJournal of


MeteorologyAdvances in

EcologyInternational Journal of


Marine BiologyJournal of


Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Advances in


Environmental Chemistry

Atmospheric SciencesInternational Journal of



Waste ManagementJournal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics


Geological ResearchJournal of

EarthquakesJournal of


BiodiversityInternational Journal of


ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


ClimatologyJournal of


could be an important factor when evaluating the droughtstress tolerance of the species Depending on the droughtstress severity a reduction of the primary production dueto these morphological and physiological adjustments is tobe expected [13ndash15] Stomatal closure is a typical temporaryreaction to drought stress leading to a reduced CO

2

uptakeand finally influencing carbon budgets and growth perfor-mances [16 17] Besides physiological adjustments droughtstress occurring during the tree development induces mor-phological adaptations from the roots to the crown whichwill characterize the hydraulic architecture of the tree [18ndash23] As a consequence the transpiration of the plant will beinfluenced along with its tolerance to drought stress [18ndash20]Hence the recovering process after drought stress in termsof growth increment could be affected by the SWA at theinitial stage of resprouting In spite of the importance of thistopic for coppicing practices up to this date there is stilla considerable informational gap the effect of the droughtoccurring during the resprouting period on the drought toler-ance biomass production andwater use under drought stresshas not been investigated In our study we aimed to assessthe impact of drought cycles applied during the resproutingphase on the drought resilience of black locust trees Wedefined the physiological conditions in terms of plant waterstatus at which the growth performance is compromisedand analyzed the influence of drought applied during theresprouting phase on the hydraulic architecture of the treeevaluating the relation between root system and the totaltranspiring surfaceThe effect of the different root weight leafarea ratio was evaluated by analyzing (i) growth performance(ii) transpiration rate (iii) aboveground biomass productionand (iv) the water use efficiency under cyclic drought stressThe information gathered enlightened the importance ofblack locust as an appropriate tree for marginal land and thestrong implication that the SWAduring the resprouting phasehas on the later drought tolerance and productivity of thespecies

2 Material and Methods

21 Plants and Drought Stress Treatment The study wascarried out with three-year-old black locust trees in alysimeter experiment under a light transmissive rain-outshelter arranged at the Brandenburg University of Tech-nology Cottbus-Senftenberg The water was supplied solelyby an automatic irrigation system The plant material wascollected from a short-rotation plantation in the postminingarea of Welzow-Sud Brandenburg Germany (N 51∘3610158401410158401015840E 14∘1910158405110158401015840) approximately 25 km south from the lysimeterfacility The climate at the collection site and at the lysimeterfacility is comparable It is a transition from the Atlanticto the continental climate with mean annual rainfall of556mm and mean annual temperature of 93∘C (1951ndash2003DeutscherWetterdienst) During the experiment the highestair temperature in Cottbus was reached in August 2012with more than 365∘C The monthly mean temperature was+07∘C above the long-term average while the early summerwas minus05∘C (June) and minus03∘C (July) colder than the average

However extreme conditions with air temperatures above30∘C and even 35∘C as observed in 2012 are common inBrandenburg All the selected trees presented a comparablecrown architecture with three main branches (mean radiusof 106 plusmn 19 cm) connected to the trunk (mean radius of134 plusmn 19 cm height approx 30 cm) At the beginning ofthe experiment all the primary branches were cut backat 10 cm from the trunk After a period of establishment(March 20 to June 1 2012) during which the plants were wellwatered the drought cycle experiment started on June 1 untilOctober 11 with two treatments short-term drought stress(STS) and long-term drought stress (LTS) each executed inthree replicas (119899 = 3) In our context we defined droughtstress as a condition where the mean soil water content(120579) was maintained at values of 7 which is the value atwhich the growth rate drastically decreases to values closeto zero The well-watered condition instead correspondedto the hydrostatic state of the lysimeter where the mean ofthe 120579 was set at 20 with full availability of water Sinceall treatments started developing new leaves during the lastweek of May we considered the resprouting phase the periodfrom the 23rd to the 26th week of the year (WOY) Thecycling of drought and full availability of water was scheduledas follows the LTS plants experienced drought conditionsthroughout the four weeks of the resprouting period Insteadthe STS plants were exposed only to one week of drought(24th WOY) during the same period After the resproutingphase three weeks of well-watered conditions followed forboth treatments From the 30th WOY on both treatmentswere exposed to drought stress for two weeks From the33rd WOY until the end of the experiment (41st WOY)the STS plants were subjected to short-term drought stress(one week of drought and two well-watered ones) while theLTS plants were subjected to long-term drought stress (twoweeks of drought stress followed by oneweek of well-wateredcondition)

22 Lysimeter and Soil Water Status In order to control theSWA and to calculate the water budget the plants were grownin lysimeters (50 cm diameter 50 cm height) under a lighttransmissive rain-out shelter [11] The daily transpiration wascalculated by the difference between the measured irrigationand the sum of the estimated daily water storage variationand the leachate collected Evaporation from bare soil wasminimized by covering the soil with a double leaflet Tofacilitate the infiltration rate the sandy loam soil column wasfilled at bulk density 13 kgmminus3 The soil relatively low inorganic carbon (13) and total nitrogen (008) presentedthe oxalate-extractable Al Fe and Mn content values of065 153 and 008mg gminus1 respectivelyThe irrigation systemwas automatically controlled by a data logger (GP1 Delta-TDevices Cambridge UK) and the water was dispensed fromfour drippers per lysimeterThe volume of water was suppliedin relation to the volumetric soil water content measuredat 20 cm depth by a frequency domain reflectometry probe(SM-200 Soil Moisture Sensor Delta-T Devices CambridgeUK) To evaluate the storage variation of the weekly waterbudget the 120579 was measured at four depths (10 20 30 and




Plan

t wat

er p

oten

tial (

MPa

)

Soil

mat

ric p

oten

tial (

MPa

)

00

minus05

minus10

minus15

minus206 8 10 12 14 16 18 20 22

000

minus005

minus010

minus015

minus020




119871


119871


119878


119878

and Ψ119871




119871

= 9013 lowast Ψ

119878



Plan

t wat

er p

oten

tial (

MPa

)


00

minus05

minus10

minus15

minus20







0

5

10

15

20

25

30

35

40

Mea

n ai

r tem

pera

ture

(∘C)

Date

1-Ju

n8

-Jun

15-Ju

n

6-Ju

l13

-Jul

20-Ju

l27

-Jul

3-A

ug

10-A

ug

17-A

ug

24-A

ug

31

-Aug

7

-Sep

14

-Sep

21

-Sep

28

-Sep

5

-Oct

12

-Oct

22-Ju

n29

-Jun

(a)

0

20

40

60

80

100

Mea

n re

lativ

e hum

idity

()

Date

1-Ju

n8

-Jun

15-Ju

n

6-Ju

l13

-Jul

20-Ju

l27

-Jul

3-A

ug

10-A

ug

17-A

ug

24-A

ug

31

-Aug

7

-Sep

14

-Sep

21

-Sep

28

-Sep

5

-Oct

12

-Oct

22-Ju

n29

-Jun

(b)




119878

and theΨ

119871



0

10

20

30

40

50

60


StorageLeachate

Wat

er (L

)

minus10

22 24 26 28 30 32 34 36 38 40 42Week of the year

(a)

22 24 26 28 30 32 34 36 38 40 42Week of the year

0

10

20

30

40

50

60

Wat

er (L

)

minus10


StorageLeachate

(b)


3 Results




0

1

2

3

4

5

6

0

100

200

300

400

500Cu

mul

ativ

e tra

nspi

ratio

n (L

)

22 24 26 28 30 32 34 36 38 40 42Week of the year

STSLTS

VPD

VPD

(kPa

Paminus1)

(a)

0

20

40

60

80

Wee

kly

trans

pira

tion

(L)

22 24 26 28 30 32 34 36 38 40 42Week of the year

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa

)


(b)

0

20

40

60

80

22 24 26 28 30 32 34 36 38 40 42Week of the year

Wee

kly

trans

pira

tion

(L)

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa


(c)






119871

was


0

2000

4000

6000

8000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(a)

0

2000

4000

6000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(b)

5

10

15

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t()

STSLTS

(c)







00

05

10

0

10

20

30

40

50

0

10

20

30

40

50

22 27 32 37 42

Week of the year

Week of the year

Week of the year

27 32 37 42

STSLTS

Wat

er u

se (L

)N

orm

aliz

ed ra

dial

incr

emen

t Radi

al in

crem

ent (

)

minus05

minus10

minus15

22 27 32 37 42

STS LTS(a)

(b) (c)

STSLTS





Dep

th (c

m)

Dry weight (g)

STSLTS

aa

bb

b

b

0 50 100 150 200 250 300 350

5

20

40




4 Discussion


119871


119871

could be found



a

aTo

tal l

eaf a

rea(m

2)

TreatmentLTS STS

10

8

6

4

2

0

(a)

a

b

TreatmentLTS STS

200

150

100

50

0

Root

wei

ght

leaf

area

(b)


LTS STSTreatment

0

400

800

1200

1600

B

b

a

A

Total Wood

Dry

bio

mas

s (g)

(a)

Treatment

0

1

2

3

4

5

a a

LTS STS

Wat

er u

se effi

cien

cy (g

Lminus1)

(b)



0 50 100 150 200 250 300 350 400 450 500Water use (L)

0

200

400

600

800

1000

1200

1400


Dry

bio

mas

s (g)





5 Conclusions




References


















































Journal of












Volume 2014

Advances in









Geophysics

















Plan

t wat

er p

oten

tial (

MPa

)

Soil

mat

ric p

oten

tial (

MPa

)

00

minus05

minus10

minus15

minus206 8 10 12 14 16 18 20 22

000

minus005

minus010

minus015

minus020




119871


119871


119878


119878

and Ψ119871




119871

= 9013 lowast Ψ

119878



Plan

t wat

er p

oten

tial (

MPa

)


00

minus05

minus10

minus15

minus20







0

5

10

15

20

25

30

35

40

Mea

n ai

r tem

pera

ture

(∘C)

Date

1-Ju

n8

-Jun

15-Ju

n

6-Ju

l13

-Jul

20-Ju

l27

-Jul

3-A

ug

10-A

ug

17-A

ug

24-A

ug

31

-Aug

7

-Sep

14

-Sep

21

-Sep

28

-Sep

5

-Oct

12

-Oct

22-Ju

n29

-Jun

(a)

0

20

40

60

80

100

Mea

n re

lativ

e hum

idity

()

Date

1-Ju

n8

-Jun

15-Ju

n

6-Ju

l13

-Jul

20-Ju

l27

-Jul

3-A

ug

10-A

ug

17-A

ug

24-A

ug

31

-Aug

7

-Sep

14

-Sep

21

-Sep

28

-Sep

5

-Oct

12

-Oct

22-Ju

n29

-Jun

(b)




119878

and theΨ

119871



0

10

20

30

40

50

60


StorageLeachate

Wat

er (L

)

minus10

22 24 26 28 30 32 34 36 38 40 42Week of the year

(a)

22 24 26 28 30 32 34 36 38 40 42Week of the year

0

10

20

30

40

50

60

Wat

er (L

)

minus10


StorageLeachate

(b)


3 Results




0

1

2

3

4

5

6

0

100

200

300

400

500Cu

mul

ativ

e tra

nspi

ratio

n (L

)

22 24 26 28 30 32 34 36 38 40 42Week of the year

STSLTS

VPD

VPD

(kPa

Paminus1)

(a)

0

20

40

60

80

Wee

kly

trans

pira

tion

(L)

22 24 26 28 30 32 34 36 38 40 42Week of the year

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa

)


(b)

0

20

40

60

80

22 24 26 28 30 32 34 36 38 40 42Week of the year

Wee

kly

trans

pira

tion

(L)

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa


(c)






119871

was


0

2000

4000

6000

8000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(a)

0

2000

4000

6000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(b)

5

10

15

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t()

STSLTS

(c)







00

05

10

0

10

20

30

40

50

0

10

20

30

40

50

22 27 32 37 42

Week of the year

Week of the year

Week of the year

27 32 37 42

STSLTS

Wat

er u

se (L

)N

orm

aliz

ed ra

dial

incr

emen

t Radi

al in

crem

ent (

)

minus05

minus10

minus15

22 27 32 37 42

STS LTS(a)

(b) (c)

STSLTS





Dep

th (c

m)

Dry weight (g)

STSLTS

aa

bb

b

b

0 50 100 150 200 250 300 350

5

20

40




4 Discussion


119871


119871

could be found



a

aTo

tal l

eaf a

rea(m

2)

TreatmentLTS STS

10

8

6

4

2

0

(a)

a

b

TreatmentLTS STS

200

150

100

50

0

Root

wei

ght

leaf

area

(b)


LTS STSTreatment

0

400

800

1200

1600

B

b

a

A

Total Wood

Dry

bio

mas

s (g)

(a)

Treatment

0

1

2

3

4

5

a a

LTS STS

Wat

er u

se effi

cien

cy (g

Lminus1)

(b)



0 50 100 150 200 250 300 350 400 450 500Water use (L)

0

200

400

600

800

1000

1200

1400


Dry

bio

mas

s (g)





5 Conclusions




References


















































Journal of












Volume 2014

Advances in









Geophysics















0

5

10

15

20

25

30

35

40

Mea

n ai

r tem

pera

ture

(∘C)

Date

1-Ju

n8

-Jun

15-Ju

n

6-Ju

l13

-Jul

20-Ju

l27

-Jul

3-A

ug

10-A

ug

17-A

ug

24-A

ug

31

-Aug

7

-Sep

14

-Sep

21

-Sep

28

-Sep

5

-Oct

12

-Oct

22-Ju

n29

-Jun

(a)

0

20

40

60

80

100

Mea

n re

lativ

e hum

idity

()

Date

1-Ju

n8

-Jun

15-Ju

n

6-Ju

l13

-Jul

20-Ju

l27

-Jul

3-A

ug

10-A

ug

17-A

ug

24-A

ug

31

-Aug

7

-Sep

14

-Sep

21

-Sep

28

-Sep

5

-Oct

12

-Oct

22-Ju

n29

-Jun

(b)




119878

and theΨ

119871



0

10

20

30

40

50

60


StorageLeachate

Wat

er (L

)

minus10

22 24 26 28 30 32 34 36 38 40 42Week of the year

(a)

22 24 26 28 30 32 34 36 38 40 42Week of the year

0

10

20

30

40

50

60

Wat

er (L

)

minus10


StorageLeachate

(b)


3 Results




0

1

2

3

4

5

6

0

100

200

300

400

500Cu

mul

ativ

e tra

nspi

ratio

n (L

)

22 24 26 28 30 32 34 36 38 40 42Week of the year

STSLTS

VPD

VPD

(kPa

Paminus1)

(a)

0

20

40

60

80

Wee

kly

trans

pira

tion

(L)

22 24 26 28 30 32 34 36 38 40 42Week of the year

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa

)


(b)

0

20

40

60

80

22 24 26 28 30 32 34 36 38 40 42Week of the year

Wee

kly

trans

pira

tion

(L)

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa


(c)






119871

was


0

2000

4000

6000

8000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(a)

0

2000

4000

6000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(b)

5

10

15

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t()

STSLTS

(c)







00

05

10

0

10

20

30

40

50

0

10

20

30

40

50

22 27 32 37 42

Week of the year

Week of the year

Week of the year

27 32 37 42

STSLTS

Wat

er u

se (L

)N

orm

aliz

ed ra

dial

incr

emen

t Radi

al in

crem

ent (

)

minus05

minus10

minus15

22 27 32 37 42

STS LTS(a)

(b) (c)

STSLTS





Dep

th (c

m)

Dry weight (g)

STSLTS

aa

bb

b

b

0 50 100 150 200 250 300 350

5

20

40




4 Discussion


119871


119871

could be found



a

aTo

tal l

eaf a

rea(m

2)

TreatmentLTS STS

10

8

6

4

2

0

(a)

a

b

TreatmentLTS STS

200

150

100

50

0

Root

wei

ght

leaf

area

(b)


LTS STSTreatment

0

400

800

1200

1600

B

b

a

A

Total Wood

Dry

bio

mas

s (g)

(a)

Treatment

0

1

2

3

4

5

a a

LTS STS

Wat

er u

se effi

cien

cy (g

Lminus1)

(b)



0 50 100 150 200 250 300 350 400 450 500Water use (L)

0

200

400

600

800

1000

1200

1400


Dry

bio

mas

s (g)





5 Conclusions




References


















































Journal of












Volume 2014

Advances in









Geophysics















0

1

2

3

4

5

6

0

100

200

300

400

500Cu

mul

ativ

e tra

nspi

ratio

n (L

)

22 24 26 28 30 32 34 36 38 40 42Week of the year

STSLTS

VPD

VPD

(kPa

Paminus1)

(a)

0

20

40

60

80

Wee

kly

trans

pira

tion

(L)

22 24 26 28 30 32 34 36 38 40 42Week of the year

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa

)


(b)

0

20

40

60

80

22 24 26 28 30 32 34 36 38 40 42Week of the year

Wee

kly

trans

pira

tion

(L)

000

minus010

minus020

minus030

Soil

mat

ric p

oten

tial (

MPa


(c)






119871

was


0

2000

4000

6000

8000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(a)

0

2000

4000

6000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(b)

5

10

15

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t()

STSLTS

(c)







00

05

10

0

10

20

30

40

50

0

10

20

30

40

50

22 27 32 37 42

Week of the year

Week of the year

Week of the year

27 32 37 42

STSLTS

Wat

er u

se (L

)N

orm

aliz

ed ra

dial

incr

emen

t Radi

al in

crem

ent (

)

minus05

minus10

minus15

22 27 32 37 42

STS LTS(a)

(b) (c)

STSLTS





Dep

th (c

m)

Dry weight (g)

STSLTS

aa

bb

b

b

0 50 100 150 200 250 300 350

5

20

40




4 Discussion


119871


119871

could be found



a

aTo

tal l

eaf a

rea(m

2)

TreatmentLTS STS

10

8

6

4

2

0

(a)

a

b

TreatmentLTS STS

200

150

100

50

0

Root

wei

ght

leaf

area

(b)


LTS STSTreatment

0

400

800

1200

1600

B

b

a

A

Total Wood

Dry

bio

mas

s (g)

(a)

Treatment

0

1

2

3

4

5

a a

LTS STS

Wat

er u

se effi

cien

cy (g

Lminus1)

(b)



0 50 100 150 200 250 300 350 400 450 500Water use (L)

0

200

400

600

800

1000

1200

1400


Dry

bio

mas

s (g)





5 Conclusions




References


















































Journal of












Volume 2014

Advances in









Geophysics















0

2000

4000

6000

8000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(a)

0

2000

4000

6000

00

01

02

03

04

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t(120583

m)

Wee

kly

trun

k in

crem

ent()

DailyWeekly

(b)

5

10

15

22 24 26 28 30 32 34 36 38 40 42Week of the year

Cum

ulat

ive t

runk

incr

emen

t()

STSLTS

(c)







00

05

10

0

10

20

30

40

50

0

10

20

30

40

50

22 27 32 37 42

Week of the year

Week of the year

Week of the year

27 32 37 42

STSLTS

Wat

er u

se (L

)N

orm

aliz

ed ra

dial

incr

emen

t Radi

al in

crem

ent (

)

minus05

minus10

minus15

22 27 32 37 42

STS LTS(a)

(b) (c)

STSLTS





Dep

th (c

m)

Dry weight (g)

STSLTS

aa

bb

b

b

0 50 100 150 200 250 300 350

5

20

40




4 Discussion


119871


119871

could be found



a

aTo

tal l

eaf a

rea(m

2)

TreatmentLTS STS

10

8

6

4

2

0

(a)

a

b

TreatmentLTS STS

200

150

100

50

0

Root

wei

ght

leaf

area

(b)


LTS STSTreatment

0

400

800

1200

1600

B

b

a

A

Total Wood

Dry

bio

mas

s (g)

(a)

Treatment

0

1

2

3

4

5

a a

LTS STS

Wat

er u

se effi

cien

cy (g

Lminus1)

(b)



0 50 100 150 200 250 300 350 400 450 500Water use (L)

0

200

400

600

800

1000

1200

1400


Dry

bio

mas

s (g)





5 Conclusions




References


















































Journal of












Volume 2014

Advances in









Geophysics















00

05

10

0

10

20

30

40

50

0

10

20

30

40

50

22 27 32 37 42

Week of the year

Week of the year

Week of the year

27 32 37 42

STSLTS

Wat

er u

se (L

)N

orm

aliz

ed ra

dial

incr

emen

t Radi

al in

crem

ent (

)

minus05

minus10

minus15

22 27 32 37 42

STS LTS(a)

(b) (c)

STSLTS





Dep

th (c

m)

Dry weight (g)

STSLTS

aa

bb

b

b

0 50 100 150 200 250 300 350

5

20

40




4 Discussion


119871


119871

could be found



a

aTo

tal l

eaf a

rea(m

2)

TreatmentLTS STS

10

8

6

4

2

0

(a)

a

b

TreatmentLTS STS

200

150

100

50

0

Root

wei

ght

leaf

area

(b)


LTS STSTreatment

0

400

800

1200

1600

B

b

a

A

Total Wood

Dry

bio

mas

s (g)

(a)

Treatment

0

1

2

3

4

5

a a

LTS STS

Wat

er u

se effi

cien

cy (g

Lminus1)

(b)



0 50 100 150 200 250 300 350 400 450 500Water use (L)

0

200

400

600

800

1000

1200

1400


Dry

bio

mas

s (g)





5 Conclusions




References


















































Journal of












Volume 2014

Advances in









Geophysics















a

aTo

tal l

eaf a

rea(m

2)

TreatmentLTS STS

10

8

6

4

2

0

(a)

a

b

TreatmentLTS STS

200

150

100

50

0

Root

wei

ght

leaf

area

(b)


LTS STSTreatment

0

400

800

1200

1600

B

b

a

A

Total Wood

Dry

bio

mas

s (g)

(a)

Treatment

0

1

2

3

4

5

a a

LTS STS

Wat

er u

se effi

cien

cy (g

Lminus1)

(b)



0 50 100 150 200 250 300 350 400 450 500Water use (L)

0

200

400

600

800

1000

1200

1400


Dry

bio

mas

s (g)





5 Conclusions




References


















































Journal of












Volume 2014

Advances in









Geophysics















0 50 100 150 200 250 300 350 400 450 500Water use (L)

0

200

400

600

800

1000

1200

1400


Dry

bio

mas

s (g)





5 Conclusions




References


















































Journal of












Volume 2014

Advances in









Geophysics




























































Journal of












Volume 2014

Advances in









Geophysics














research article effects of drought frequency on growth ... · development may have an impact on...

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