Soluble N compound profiles and concentrations in European beech (Fagus sylvatica L.) are influenced by local climate and thinning

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1 Eur J Forest Res (26) 125: 1 14 DOI 1.17/s ORIGINAL PAPER Michel Nhm Æ Thoms Holst Æ Andres Mtzrkis Helmut Myer Æ Heinz Rennenerg Æ Arthur Geßler Solule N compound profiles nd concentrtions in Europen eech (Fgus sylvtic L.) re influenced y locl climte nd thinning Received: 11 Octoer 24 / Accepted: 11 July 25 / Pulished online: 14 Decemer 25 Ó Springer-Verlg 25 Astrct We ssessed sesonl chnges of totl solule nonprotein nitrogen compounds (TSNN) in dult Europen eech trees (Fgus sylvtic, L.) growing under different locl climte during the growing seson immeditely following thinning tretment nd 3 yers lter. In oth yers, smples of leves, xylem sp nd phloem exudtes from eech trees growing in thinned nd unthinned (control) stnds on dry, wrm SW exposed nd cooler, moist NE exposed site were collected in My, July nd Septemer. In My of oth yers, sprgine (Asn) nd glutmine (Gln) were most undnt in leves nd xylem, respectively, wheres rginine (Arg) dominted in the phloem. In July, TSNN concentrtions decresed in ll tissues nd sites, ut differences in wter vilility etween spects were reflected in TSNN concentrtions. In Septemer, differences in the increse of Arg concentrtion in the phloem were relted to differences in the onset of senescence etween tretments. Thinning tretment incresed mino compound concentrtions of eech tissues in July on oth spects, prticulrly t the NE thinned site. It is supposed tht, the N lnce of dult eech is fvoured y oth, the thinning tretments s well s the cool-moist climte previling t the NE spect. Communicted y Frnz Mkeschin M. Nhm Æ H. Rennenerg Æ A. Geßler Chir of Tree Physiology, Institute of Forest Botny nd Tree Physiology, Alert Ludwigs University of Freiurg, Georges-Ko hler-allee, Geäude 53/54, 7911 Freiurg, Germny T. Holst Æ A. Mtzrkis Æ H. Myer Meteorologicl Institute, Alert Ludwigs University of Freiurg, Werderring 1, 7985 Freiurg, Germny Present ddress: A. Geßler (&) School of Forest nd Ecosystem Science, University of Melourne, Wter Street, 3363 Creswick, VIC, Austrli E-mil: rthur.gessler@sonne.uni-freiurg.de Tel.: Keywords Amino compounds Æ Sp flow density Æ N flow in the xylem Æ Adult Europen eech Æ Thinning Æ Climte Æ N remoilistion Introduction In Centrl Europe, Europen eech (Fgus sylvstic L.) is the dominnt deciduous tree species of the potentil nturl vegettion (Ellenerg 1992). Wheres eech forests hve een replced y conifer plnttions during the lst two centuries, eech is recently fvoured y forest policy to sustitute prts of monoculturl spruce forests (Dertz 1996), ecuse these monocultures re ecologiclly of low vlue nd hve shown sensitivity to clmities cused y storms nd insects. For instnce, the stte of Bden-Wu rttemerg (Germny) ims t mplifying the reltive portion of eech forests from c. 2% to more thn 3% of the forested re within this century (Moosmyer 22). Beech is drought-sensitive species, nd its southern re of distriution is minly limited y wter vilility (Ellenerg 1992). Since climte projections for Centrl Europe predict elevted tempertures nd prolonged drought periods during summer within the next decdes (IPCC 21; Sch r et l. 24), eech trees re supposed to experience environmentl conditions tht impir their wter lnce nd reduce nutrient uptke in future (Fotelli et l. 22; Spiecker et l. 21). Thinning or selective felling s frequently pplied forest mngement prctice to promote dult trget trees or nturl regenertion in deciduous forests (Trp et l. 2) lso chnges the microclimte in forest stnds y incresing incoming rdition (Myer et l. 22). Especilly eech stnds growing on shllow soils of low wter storge cpcity derived from limestone (Rendzin soils) might e negtively ffected y oth, dry future climte nd silviculturl tretments (Geßler et l. 21), since wter lnce of eech cn e impired y thinning under unfvourle climtic conditions such s drought periods during the growing seson (Cˇ ermk

2 2 et l. 1993; Bred et l. 1995; Geßler et l. 21). Since nutrient uptke in eech is lrgely dependent on wter vilility (Fotelli et l. 21, 22), dditionl effects of drought on minerl nutrition hve to e ssumed. Among minerl nutrients, N is mjor growth-limiting fctor in nturl forest ecosystems with low nthropogenic N input (Rennenerg et l. 1998), nd chnges in N vilility or uptke influence growth ptterns of eech (Mrschner 1995). Fotelli et l. (24) found tht thinning ffected nitrte uptke of nturl eech regenertion differently under different climtic conditions. It incresed pedospheric N uptke in cool nd moist eech stnds, wheres uptke ws decresed in dry nd wrm stnds. For dult trees, positive effects of thinning on the remining trees, e.g. improved growth prmeters (Yu et l. 23), nutrient vilility (Thiodeu et l. 2), or drought resistnce (Lurent et l. 23) hve frequently een oserved. However, the comined effects of climte nd thinning on the N lnce of dult eech trees growing on lime stone derived soils hve not yet een ssessed nd n integrtive physiologicl mesure to predict nutritionl responses of dult eech trees to these fctors is lcking. In previous studies, the ptterns of totl solule nonprotein nitrogen compounds (TSNN) cycling within the plnt hve een used to chrcterise the N lnce of trees (Fotelli et l. 22; Geßler et l. 1998; Nordin et l. 21). The pool of mino compounds cycling etween roots nd shoot is involved in N trnsloction, storge nd remoilistion nd in the regultion of pedospheric N uptke (Millrd 1996; Cputo nd Brneix 1997; Geßler et l. 23; Collier et l. 23). Studies with different plnt species (whet, rye, Scots pine, Norwy spruce, Europen eech) support the hypothesis tht lloction of specific mino compounds (especilly Gln) etween shoot nd root nd vice vers is influenced y the rtio etween N supply nd N demnd (Cooper nd Clrkson 1989; Gezelius nd N sholm 1993; Muller et l. 1996; Schneider et l. 1996; Kreuzwieser et l. 1997; Geßler et l. 1998). In ddition, the ssessment of sesonl chnges in the mount of Arg cn e used to chrcterise N remoilistion nd storge processes in spring nd utumn, respectively (Geßler et l. 1998; Fotelli et l. 22). Due to trnsloction nd signlling functions, the pool of solule N compounds rects rpidly to chnges in N vilility nd demnd nd, hence, is supposed to e sensitive indictor of the plnt s internl N sttus nd growth potentil (Rennenerg nd Geßler 1999; Fotelli et l. 22; Novitsky et l. 22; Foyer et l. 23), in contrst to totl N concentrtion which does not vry intensively over wide rnge of different N vilility (Geßler nd Rennenerg 2). Therefore, sesonl chnges in TSNN composition nd concentrtion in vrious tissues of dult eech trees grown in the field under different locl climtic conditions nd in different thinning tretments were exmined in the present study. With this pproch we wnted to ssess the pplicility of TSNN nlysis for chrcteristion of the N nutrition sttus of dult eech trees s ws ssessed previously for eech seedlings (Fotelli et l. 22). The min hypothesis sed on the wter lnce of dult eech trees (Geßler et l. 21; Keitel et l. 23) nd the N nutrition of eech seedlings (Fotelli et l. 22, 24) t the sme field sites ws tht the N lnce of dult trees ws ffected y oth locl climte nd silviculturl tretment. We expected etter N supply nd, hence, incresed TSNN concentrtions in vrious tissues of eech grown on the NE slope compred to the dry-wrm SW slope which is supposed to e locl climtic model for the generl climtic conditions in Centrl Europe within the next 5 1 yers (Geßler et l. 24) nd higher TSNN concentrtions on the thinned stnds compred to the controls. To clrify if potentil effects of thinning on the N sttus of dult eech re trnsient or persisted over longer time period, TSNN composition nd concentrtions were determined in the growing seson immeditely following the thinning tretment nd 3 yers lter. Mteril nd methods Experimentl sites The experimentl sites of this study re locted in southern Germny, out 1 km south southwest from Stuttgrt (longitude: 8 45 E; ltitude: 48 N) in low mountin rnge (Schw ische Al, m ove se level). Long-term men nnul regionl ir temperture mesured t climte sttion of the Germn Wether Service (DWD) out 6 km from the experimentl sites, is out 6.6 C, nd men temperture during the growing seson (My to Octoer) is out 11.5 C. Men nnul precipittion is 856 mm with monthly mxim in June nd July, the totl precipittion during the growing seson (My to end of Septemer) mounts to men vlues of 41 mm. In the growing seson of 1999, men ir temperture ws 14.8 C nd precipittion reched 478 mm, wheres the temperture in 22 ws slightly lower (14.3 C) nd the totl precipittion mounted to 551 mm (Tle 1). The experimentl sites re locted on two opposing slopes of nrrow vlley, less thn 1, m prt from ech other. One of the sites fces to the north-est (NE) nd the other to the south-west (SW). Forests on oth sides of the vlley re dominted y Europen eech (F. sylvtic L.) ged 7 8 yers, contriuting to >9% of the sl re of dult trees. Soil profiles re chrcterised s Rendzic Leptosols (WRB-clssifiction, ISSS 1998) derived from limestone (Weissjur et nd gmm series) nd re shllow on oth sites, verging less thn.2 m depth of topsoil efore ecoming dominted y prent rock interspersed with pockets of orgnic mtter nd minerl soil. The soil profile t the SW site is especilly rocky, contining more thn 4% (volumetric sis) rocks nd stones (>6 mm dimeter) in the top.2 m of the soil nd rising to 8% elow

3 3 Tle 1 Climte chrcteristics of the experimentl sites during growing seson (My to end of Septemer) 1999 nd 22 Tuttlingen climte sttion NE spect SW spect Men ir temperture 1999 ( C) 14.8 Totl precipittion 1999 (mm) 478 Men ir temperture 22 ( C) Totl precipittion 22 (mm) c 784 c Climte chrcteristics of the four sites in 22 Control Tretment Control Tretment Men T ir in 1.5 m height ( C) Men middy T ir in 1.5 m height ( C) d Men T soil in 5 cm depth ( C) Men T soil in 1 cm depth ( C) Men RH (%) Men PAR in 1.5 m height (lmol m 2 s 1 ) Totl throughfll (mm) e Bsl re of dult trees (m 2 h 1 ) The experiments were crried out on two opposing slopes in smll vlley, fcing north-est (NE) nd south-west (SW) nd were either sujected to thinning (T) or remined unthinned s controls. In 1999, climte dt could only e otined from the climte sttion Tuttlingen of the Germn Wether Service, 6 km est of the sites. Men vlues shown re verges of dily (24 h) mens Mesurement t 2 m.g.l Mesurement ove the cnopy c Mesurement ove the cnopy (42 m.g.l.) d Dt re mens of tempertures mesured etween 13: nd 15: CET e Totl throughfll refers to the mount of precipittion pssing through the cnopy of the trees nd reching the forest floor.5 m. The soil t the NE site contins 15% rocks nd stones in the uppermost.2 m of the soil nd c. 3% elow.5 m. Soil ph (H 2 O) is 5.7 in the orgnic surfce lyer nd 7.5 t 6 cm depth. The difference in spects (NE, SW) produces difference in rdition interception per m 2 of inclined surfce re with higher energy ville on the SW site (Geßler et l. 21; Myer et l. 22). According to the retrospective nlyses of meteorologicl dt, s well s the growth nd wter sttus of dult eech trees (Geßler et l. 21) nd eech seedlings (Fotelli et l. 22), the SW-exposed site hs permnently lower wter vilility (Keitel et l. 23) s well s incresed soil tempertures ner ground (Holst et l. 24; Tle 1). Thus, the understorey vegettion differs etween the two sites (Pul 23) nd the clssifiction of the stnd on the NE site is Hordelymo-Fgetum nd on the SW site, Crici-Fgetum (Oerdorfer 1992). To ssess the effects of thinning, selective felling of trees ws performed in Mrch 1999 on oth sides of the vlley. The totl sl re (BA) of trees on the untreted control plots vried etween sites; on the NE site the men BA in control plots ws 27 m 2 h 1, while on the SW site the control plot BA ws out 2 m 2 h 1. Thinning reduced BA of dult trees to c. 1 m 2 h 1 on oth spects (for further detils see Fotelli et l. 22). It resulted in incresed PAR on the forest floor (Myer et l. 22; Tle 1) nd, hence, in higher soil tempertures on oth spects (Holst et l. 24; Tle 1). Precipittion throughfll in 22 ws notly higher on the SW thn on the NE spect; oth slopes received more precipittion thn the djcent DWD climte sttion Tuttlingen (Tle 1). Throughfll t the forest floor ws higher in the thinned stnds s compred to the controls on oth spects (Tle 1). Elementl nlysis of leves performed in July 1999 (Tle 2) provided no indictions of nutrient deficiencies nd/or imlnces (cp. Buer et l. 2; Rothe 1998) on oth spects nd in oth silviculturl tretments. Thinning decresed plnt re index [PAI (m 2 m 2 )] from 5.2 (control) to 1.7 in the thinning tretment on the NE spect nd from 5.1 to 2.1 on the SW spect in the first yer fter the tretment (Holst et l. 24). Until 22 PAI incresed to pproximtely 2.7 in the thinning tretment of oth spects nd remined constnt in the controls. Plnt mteril Twigs nd leves from sun crowns of dult eech trees growing in thinned stnds (T) nd n unthinned control stnd (C) were hrvested on oth spects of the vlley. Smpling cmpigns were conducted during the growing sesons of the yers 1999 nd 22 in My (immeditely fter ud rek: 6 to 7 My 1999 nd 5 to 7 My 22), July (in the middle of the growing seson: 15 to 16 July 1999 nd 1 to 2 July 22) nd in Septemer (t the end of the growing seson: 6 to 17 Septemer 1999 nd 18 to 19 Septemer 22). Figure 1 nd show the cumultive dimeter distriution (dimeter t rest height, DBH) of trees in the control tretment of the NE nd SW spect wheres Fig. 1c nd d show the sme prmeter on the thinned plots. In the thinning tretment minly trees with low DBH were removed nd, thus thinning incresed the men DBH of the trees t these plots. Due to the different long-term growing conditions the medin of the DBH vlues ws lower on the SW s compred to the

4 4 Tle 2 Elementl concentrtions of leves of dult eech trees grown on two opposing slopes of nrrow vlley, eing exposed to NE nd SW, respectively Site N S P Mg C N K NEC 1.6±.4 44.± ± ± ±59.4.6± ±68.1 NET 1.7± ± ± ± ±72.3.8± ±47.7 SWC 1.8± ± ±4. 65.± ±87.2.7± ±36.5 SWT 1.7± ± ± ± ± ± ±46. On oth slopes, the forest stnd ws sujected to thinning (T), wheres nother stnd remined untreted nd is referred to s control stnd (C). Concentrtions were determined in smples collected in July 1999 nd re given in lmol g 1 dry wt. with stndrd devition, except concentrtions of Nitrogen, which re given in mmol g 1 dry wt. NE spect. In order to compre comprle trees etween tretments nd to ccount in ddition for the different long-term growing conditions etween spects our selection criterion ws the following: we hve chosen for oth, control nd tretment, trees with DBH vlues ove the medin of the respective control tretment (NE or SW) ut excluded the 1% of trees with highest DBH vlues. Thus, we hve only selected dominnt trees within the dimeter rnge of cm in oth tretments t the NE spect nd within the dimeter rnge cm in oth tretments on the SW spect. The DBH vlues of the prticulr trees exmined re given in Tle 3. During ll cmpigns in 1999 nd 22 the sme trees were smpled. The twigs from the dult trees were otined y professionl tree climers cutting two twigs from ech of four trees per site nd tretment during ech smpling cmpign. Leves, phloem exudtes nd xylem sp were collected from ech twig. During ech mesurement cmpign the smples were tken etween 9: nd 11: to minimise influences of diurnl chnges in Percent 5. Percent DBH [cm] DBH [cm] Percent 5. Percent DBH [cm] DBH [cm] Fig. 1 Cumultive frequency distriution of dimeter in rest height (DBH) of the unthinned control plots of the NE () nd SW () spect nd the thinned plots of the NE (c) nd SW spect (d) of the experimentl site. Mesurement of DBH ws performed in Ferury Totl numer of trees (N) ws 625 (SW control), 468 (NE control), 226 (SW tretment) nd 216 (NE tretment). For ech r the men vlue (x cm) of dimeter group is given. The group rnges from x 1.5 to x cm. In ddition ox plot displys medin, twenty-fifth nd seventy-fifth percentiles s well s upper nd lower djcent vlues nd outliers. (Source: Institute of Forest Growth nd Institute of Silviculture, Alert-Ludwigs Universit t Freiurg)

5 5 TSNN. Leves nd xylem sp were immeditely frozen in liquid N 2 nd stored t 8 C. Collection of phloem exudte Phloem exudtes of twigs from dult eech trees were otined pplying the EDTA-technique descried y Schneider et l. (1996). Smll pieces of rk (c. 3 mg FW) were cut from the twig nd incuted for 5 h in 2 ml exudtion solution contining 1 mm EDTA nd.15 mm chlormphenicol t ph 7. After 5 h, the rk pieces were removed from the solution nd the remining exudte ws stored in liquid N 2. Previous studies (Schneider et l. 1996) showed tht contmintion of phloem exudtes of eech with cellulr constituents cn e neglected under the experimentl conditions pplied. Collection of xylem sp Xylem sp of roots ws collected y the modifiction of the procedure of Scholnder et l. (1965) descried y Schneider et l. (1996). After removing the rk from the cut end t length of c. 3 mm, twigs of 3 5 cm length were plced in pressure chmer with the cut end protruding c. 1 mm. Susequently, incresing pressure ws pplied t rte of.1.2 MP min 1. The pressure t which xylem sp first ws visile t the cut end ws recorded s current wter potentil of the twig. The outflow of xylem sp ws collected with pipettes nd trnsferred into Eppendorf vils, which were frozen in liquid N 2. Contmintion with cellulr components ws checked under the experimentl conditions pplied y mesuring luminometriclly the ATP concentrtions of the xylem sp (Schupp 1991; Rennenerg et l. 1998) nd ws found to e elow.5% (Schneider et l. 1996; Geßler et l. 1998). Extrction of mino compounds, mmonium nd nitrte Smples of frozen leves were ground in liquid N 2 with mortr nd pestle. For extrction of mino compounds nd mmonium, liquots of.1 g of the frozen powder were homogenised in.2 ml uffer (ph 7.) contining 2 mm Hepes, 5 mm EGTA nd 1 mm NF, in 1 ml chloroform: methnol (1.5:3.5, v:v) ccording to Winter Tle 3 DBH vlues (cm) of the trees exmined on the different spects nd tretments s determined in 1999 NE-C NE-T SW-C SW-T et l. (1992). The homogente ws incuted for 3 min t 4 C nd susequently, wter-solule metolites were extrcted twice with.6 ml doule-deminerlised wter fter centrifugtion t 4 C for 5 min t 16,g. The queous phses were comined, centrifuged for 1 min gin nd then freeze-dried (Alph 2 4, Christ, Osterode, Germny). For the extrction of nitrte in leves liqouts of.25 g of the frozen powder were incuted for 1 h with 1.5 ml doule-deminerlised wter nd 7 mg PVPP t 5 C to remove phenolic compounds. Susequently, the smple ws heted t 95 C for 5 min, shortly stored on ice for recovery to room temperture nd centrifuged for 5 min t 16,g. The superntnt ws extrcted nd stored t 8 C. Phloem exudtes were treted similrly for nitrte nlyses: 1 ml of the exudte were incuted in 9 ml doule-deminerlised wter with 7 mg PVPP for 1 h, heted t 95 C for 5 min nd centrifuged fterwrds. Determintion of TSNN Freeze-dried lef smples were dissolved in 1 ml lithium citrte uffer (.2 M, ph 2.2). The ph vlues of this solution s well s liqouts of the phloem exudte were djusted to ph 2.2 efore centrifugtion t 4 C for 5 min t 16,g. An liquot of 2 75 ll of ech smple ws injected into n utomted mino cid nlyser (Biochrom, Phrmci LKB, Freiurg, Germny). Xylem sp ws directly injected into the mino cid nlystor without pre-tretment. The mino cids were seprted on PEEK column (Ultrpc 8 Resin, Lithium mm, Biochrom, Phrmci, Freiurg, Germny) working with system of five lithium citrte uffers generting ph grdient from ph 2.8 to 3.55 to seprte the mino compounds s descried y Geßler et l. (1998). After seprtion, the different mino cids nd mmonium were derivtised with ninhydrin nd detected spectrophotometriclly t 44 nd 57 nm. The peks were identified nd quntified using stndrd solution contining 39 mino cids nd mmonium (Sigm Chemie, Deisenhofen, Germny). For nitrte nlysis, liquots of.5 ml of the superntnts were injected into n ion exchnge chromtogrphy system (DX 1, Dionex, Idstein, Germny). Anions were seprted on n IonPc Ò column (AS9-Sc 25 4 mm, Dionex, Idstein, Germny) using solution contining 1.8 mm N 2 CO 3 plus 1.7 mm NHCO 3 t flow rte of 1. ml min 1. Nitrte ws detected with conductivity detector module (CDM, Dionex, Idstein, Germny). The detection limit of this method is <.3 nmol ml 1. In the phloem exudtes determintion of nitrte concentrtions ws performed with UV-VIS detector (SPD-6AV, Shimdzu, Duisurg, Germny) t 21 nm s descried y Hyshi nd Chino (1985). The detection limit of this method is <.3 nmol ml 1.

6 6 Stnd trnspirtion, sp wood re nd mss flow densities Stnd trnspirtion ws clculted using the wter lnce model WBS3 (Schmidt 199), forest-hydrologicl model tht requires dily men vlues of ir temperture nd dily precipittion s meteorologicl inputs. Timeindependent input vriles of the WBS3-simultions re: sl re of the stnd, mixing rtio of deciduous trees, mixing rtio of coniferous trees, type of soil, slope ngle, slope direction nd geogrphicl ltitude. For evpotrnspirtion, trnspirtion nd interception of forests, vlidtions of WBS3 showed good greement etween results from model clcultions nd mesurements for different res nd slopes (Fritsch 1998; Mtzrkis et l. 2). Model clcultions for oth yers were conducted with dt from the nery DWD climte sttion Tuttlingen, strting t My 15 since model pplicility depends on full lef expnsion. For vlidtion of the model we plotted the sums of dily trnspirtion of the two control plots clculted with the WBS 3 model for the growing seson 2 ginst vlues otined from up-scled xylem flow mesurements (Fig. 2) with Grnier-style sensors (see Keitel et l. 23). There ws resonle good greement etween the two pproches for oth spects, even though the control stnds on the two slopes differed in stem density nd timer volume (Geßler et l. 24). On oth spects, sp wood res (SA in m 2 spwood m 2 forest floor) of 25 trees were determined using flourescent ererine-chlorid solution following the method descried in Glvc et l. (1989). On the sis of SA nd stnd trnspirtion (ST in 1m 2 dy 1 ), sp flow densities (SD in ml H 2 O cm 2 dy 1 ) were clculted ccording to the following eqution: SD ¼ ST SA : Mss flow of N (mmol cm 2 dy 1 ) ws otined y multiplying sp flow density with the TSNN concentrtion of the xylem. 4. Recovery rtes Stnd trnspirtion clculted from xylem flux [mm d -1 ] NE control For vlidtion of the extrction methods pplied the recovery rtes of mmonium, sprtic cid (Asp), sprgine (Asn), glutmic cid (Glu), glutmine (Gln) nd rginine (Arg) pplied s internl stndrds hve previously een determined in the phloem exudtes nd in leves of eech. Recovery rtes mounted to etween c. 82±16% nd 18±12% for the different TSNN compounds in the different tissues (Geßler 1999). Dt nlysis Stnd trnspirtion clculted from xylem flux [mm 1 ] SW control Stnd trnspirtion clculted y WBS 3 [mm 1 ] Fig. 2 The dily sums of stnd trnspirtion otined from the WBS 3 model for the control plots of the SW nd NE spect during the growing seson 2, plotted ginst stnd trnspirtion clculted from sp flux mesurements. The dt for xylem flux densities up-scled from singles tree to the stnd trnspirtion level were tken from Keitel et l. (23) Sttisticl nlysis ws performed using SPSS 11. (SPSS, Inc., USA). The effect of spect nd thinning tretment on TSNN nd on the concentrtions of the most undnt mino compounds were ssessed using one-wy ANOVA. Results Sp flow densities During oth the growing sesons in 1999 nd 22, the sp flow rised from mid My to rech mximum vlues of c. 2 ml H 2 Ocm 2 dy 1 t the thinned stnds nd mximum vlues of c. 16 ml H 2 Ocm 2 dy 1 t the control stnds in mid summer, nd susequently decresed gin until the end of Septemer (Fig. 3). Throughout the two growing sesons, trees grown on the thinned stnds constntly displyed higher sp flow densities compred to the control stnds on either spect. During oth yers, lowest sp flow densities were

7 7 Fig. 3 Precipittion nd sp flow densities of dult Europen eech trees grown t two differently exposed sites (NE vs. SW) in control stnds (C) nd in stnds sujected to thinning (T) during the vegettion periods 1999 nd 22 when leves were fully expnded. Arrows indicte the times of smpling cmpigns in July nd Septemer. The My cmpigns re not indicted since they took plce efore full lef expnsion Sp flow density [ml H 2 O cm -2 d -1 ] NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T Precipittion [mm] My 15 Jun 15 Jul 15 Aug 15 Sep oserved with trees of the NE control stnd, wheres highest sp flow densities were displyed y trees grown on the dry-wrm SW thinned stnd prticulrly fter the middle of July. In mid summer months sp fluxes were enhnced during periods of low precipittion nd long sunshine durtion, especilly during the dry period in June 22. TSNN compound profile nd concentrtions in the xylem During the growing sesons 1999 nd 22 there ws cler trend to decrese in TSNN concentrtion from the eginning to the end of the growing seson (Fig. 4). In My 1999, TSNN concentrtions vried etween 19.7 Fig. 4 TSNN composition nd concentrtions in twig xylem sp of dult Europen eech trees grown in control stnds (C) nd in stnds sujected to thinning (T) t two differently exposed sites (NE vs. SW). The concentrtions of the six most undnt mino compounds nd mmonium re shown, s well s the sum of ll other proteinogenic (Spr) nd nonproteinogenic (Snr) mino compounds including nitrte G: c-minoutyric cid. Xylem sp ws collected t six smpling cmpigns in My, July nd Septemer 1999 nd 22. Sttisticl nlysis ws performed y one-wy Anov followed y Tukey post hoc test. Different letters indicte differences in TSNN concentrtion etween spects nd tretments (P<.5). The vlues shown re mens (+SD) of four trees N composition in the xylem sp [µmol N ml -1 ] 7 1 M y J u l y S e p t c NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T M y J u l y S e p t NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T Aspect nd tretment Asp Asn Glu Gln G + NH 4 Arg Spr Snr

8 8 nd 24.9 lmol N ml 1, ut no significnt effect of tretment or spect on TSNN or prticulr compound ws oserved. Independent of site or tretment, Gln nd Asn were the most undnt mino compounds comprising c. 44% nd 3% of TSNN, respectively. In July 1999, TSNN decresed notly on oth spects nd in oth tretments. The lowest concentrtion of 1.7 lmol Nml 1 ws oserved t the NE control site wheres the July mximum (6.8 lmol N ml 1 ) ws detected t the SW thinned site. The decrese etween My nd July ws due to reduction of ll mjor components. A significnt difference in TSNN concentrtions ws oserved in oth thinned stnds s compred to the respective control sites. Compring the sme tretments on the two spects, TSNN concentrtions were higher on the SW spect, though differences were significnt only for the thinned stnds. In Septemer 1999, TSNN of xylem sp decresed slightly compred to July mounting to lmol N ml 1. Neither TSNN nor single compounds showed significnt differences etween spect nd tretment. In My 22, TSNN concentrtions were higher in oth tretments on the SW spect nd on the control tretment of the NE spect s compred to TSNN mounted to etween 22. lmol N ml 1 (NET) nd 5.5 lmol N ml 1 (NEC). The reltive composition of TSNN ws comprle to 1999 with Gln (46%) nd Asn (28%) s most undnt compounds. The significntly lower TSNN concentrtion in the NE thinned stnd s compred to the other stnds ws minly consequence of reduced Asn nd Gln concentrtions. In July 22, TSNN decresed drsticlly compred to My, ut significnt influence of site or tretment ws not detected. In Septemer 22, TSNN concentrtions of the NE thinned stnd nd oth SW stnds decresed slightly compred to July, mounting to etween 1.1 nd 3.8 lmol N ml 1. Highest TSNN concentrtions were oserved in the xylem of trees from the NE control site, minly s consequence of high Arg concentrtions. Throughout the two growing seson, nitrte in xylem mounted to <1% of TSNN. Nitrogen mss flow in the xylem In July 1999, N mss flow reched vlues etween.15 nd.9 mmol N cm 2 dy 1, nd ws significntly higher on oth thinned stnds compred to the control stnds (Fig. 5). Moreover, xylem N flow ws significntly enhnced on the SW thinned site compred to the NE thinned site. In Septemer 1999, N flow decresed to similr vlues of c..1 mmol N cm 2 dy 1 on ll four sites. In July 22, N flow mounted to.21 nd.56 mmol N cm 2 dy 1. As in July 1999, the thinned stnds displyed higher N flow thn the control stnds, ut the only significnt difference ws oserved etween the NE thinned stnd nd the SW control stnd. In Septemer 22, N flow ws gin reduced to similr vlues of c..1 mmol N cm 2 dy 1 on ll four sites exmined. TSNN compound profile nd concentrtions in the leves As in the xylem, there ws cler trend to decrese in leve TSNN concentrtion in leves from the eginning to the end of the growing seson in oth yers (Fig. 6) July Sept. July Sept. N flux [mmol N cm -2 d -1 ] c. NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T NE-C NE-T SW-C Aspect nd tretment SW -T NE-C NE-T SW-C SW -T Fig. 5 N flux in the xylem of dult Europen eech trees grown in control stnds (C) nd in stnds sujected to thinning (T) t two differently exposed sites (NE vs. SW). N flux ws clculted on the sis of totl solule N (TSNN) in the xylem, sp wood re of the trees nd stnd trnspirtion fter full lef expnsion; thus the My cmpigns re excluded. Xylem sp ws collected from eech twigs t four smpling cmpigns in July nd Septemer 1999 nd 22. Sttisticl nlysis ws performed y one-wy Anov followed y Tukey post hoc test. Different letters indicte differences in TSNN concentrtion etween spects nd tretments (P<.5). The vlues shown re mens (+SD) of four trees

9 9 In My 1999, TSNN vried etween 26.8 nd 86.9 lmol N g 1 f.wt. Asn ws the previling mino compound with c. 26% of TSNN. Concentrtions of TSNN, Asn, mmonium displyed significnt exposition effect, i.e. n increse on oth SW sites compred to the NE sites. Moreover, the concentrtion of Arg ws significntly incresed on the SW thinned site compred to the NE thinned site. In July 1999, TSNN ws drsticlly reduced compred to My, mounting to etween 3.6 nd 5.7 lmol N g 1 f.wt. Similr to My, TSNN of the SW thinned stnd significntly exceeded TSNN of the NE thinned stnd. TSNN in the leves mounted to etween.5 nd.7% of totl N (dt not shown). In Septemer 1999, TSNN decresed slightly to vlues from 2.8 to 3.4 lmol N g 1 f.wt. Effects of spect or tretment were not detected. Throughout the growing seson, Nitrte ws lmost sent in the leves (<1% of TSNN). In My 22, TSNN vried from 26.6 to 35.9 lmol N g 1 f.wt. Min mino compounds were Asn with 29% of TSNN nd Glu with c. 16%. In contrst to My 1999, no significnt differences in TSNN were oserved etween spect nd tretment. In July 22, TSNN ws mrkedly reduced to etween 3.2 nd 7.7 lmol N g 1 f.wt, rnge comprle to July This effect could e ttriuted to reduction of Asn nd Glu. The predominnt mino compound ws Glu (24%), followed y Asp (13%). In the thinned stnds, TSNN, Asp, Glu, Gln nd mmonium were significntly higher on the NE spect, pttern inverse to tht oserved 3 yers efore. TSNN mounted to etween.5 nd 1.2% of totl N in the leves (dt not shown). In Septemer 22, TSNN decresed slightly compred to July. It mounted to etween 2.8 lmol N g 1 f.wt in the SW thinned stnd nd 5.1 lmol N g 1 f.wt in the NE thinned stnd. In the SW thinned stnd, TSNN ws significntly lower s compred to the SW control stnd nd the NE thinned stnd, wheres TSNN ws significntly incresed on the NE thinned stnd. Throughout the two growing seson, nitrte in leves mounted to <1 2% of TSNN. TSNN compound profile nd concentrtions in the phloem Comprle to the trend of TSNN concentrtions in xylem nd leves, there ws decrese in phloem TSNN concentrtion from the eginning to the end of the growing seson 1999 (Fig. 7). By contrst, phloem TSNN concentrtions in 22 reched mximum in Septemer. In My 1999, TSNN vried etween 4. nd 15.4 lmol N g 1 f.wt. The dominnt mino compound ws Arg, comprising c. 51% of TSNN. A significnt tretment nd exposition effect with incresed concentrtions of TSNN, Asn, Gln nd Arg ws oserved on the NE thinned stnd with significntly higher vlues compred to the NE control stnd nd the SW thinned stnd. In July 1999, TSNN declined to etween 1.4 lmol N g 1 f.wt (SW-T) nd 2.6 lmol N g 1 f.wt (NE- C), which ws primrily due to decrese of Arg. Fig. 6 TSNN composition nd concentrtions in leves of dult Europen eech trees grown in control stnds (C) nd in stnds sujected to thinning (T) t two differently exposed sites (NE vs. SW). The concentrtions of the six most undnt mino compounds nd mmonium re shown, s well s the sum of ll other proteinogenic (Spr) nd nonproteinogenic (Snr) mino compounds including nitrte. The leves were collected t six smpling cmpigns in My, July nd Septemer 1999 nd 22. Sttisticl nlysis ws performed y one-wy Anov followed y Tukey post hoc test. Different letters indicte differences in TSNN concentrtion etween spects nd tretments (P<.5). The vlues shown re mens (+SD) of four trees N composition in leves [µmol N g -1 f.wt] M y c c NE-C NE-T SW-C SW-T J u l y Se p t NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T 1 M y 2 2 Ju l y Se p t. 2 2 c 8 7 c NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T Aspect nd tretment Asp Asn Glu Gln G + NH 4 Arg Spr Snr

10 1 Fig. 7 TSNN composition nd concentrtions in twig phloem sp of dult Europen eech trees grown in control stnds (C) nd in stnds sujected to thinning (T) t two differently exposed sites (NE vs. SW). The concentrtions of the six most undnt mino compounds nd mmonium re shown, s well s the sum of ll other proteinogenic (Spr) nd nonproteinogenic (Snr) mino compounds including nitrte. Phloem sp ws collected t six smpling cmpigns in My, July nd Septemer 1999 nd 22. Sttisticl nlysis ws performed y one-wy Anov followed y Tukey post hoc test. Different letters indicte differences in TSNN concentrtion etween spects nd tretments (P<.5). The vlues shown re mens (+SD) of four trees N composition in phloem exudtes [µmol N g -1 f.wt] M y J u l y S e p t NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-TNE-C NE-T SW-C SW-T 2 18 M y 2 2 J u l y 2 2 S e p t c c NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T NE-C NE-T SW-C SW-T Aspect nd tretment Asp Asn Glu Gln G + NH 4 Arg Spr Snr Differences etween spects or tretments were not oserved. In Septemer 1999, TSNN vried etween 1.5 nd 2.2 lmol N g 1 f.wt nd did not show ny significnt differences etween spects nd tretments. In My 22, TSNN mounted to c. 9 lmol N g 1 f.wt t ll spect nd tretment. The most undnt mino compounds were Arg (33% of TSNN) nd Asn (14%). In July 22, TSNN decresed to 1.7 lmol N g 1 f.wt t the SW control stnd nd to 5.3 lmol N g 1 f.wt t the NE thinned stnd. At this time of the yer, the most undnt mino compound ws Al, comprising 24% of TSNN nd 49% of the proteinogenic rest. A significnt tretment effect ws oserved on the NE spect with incresed concentrtions of TSNN, Glu, nd Gln in the thinned stnd. In ddition, TSNN, Gln, nd mmonium were significntly higher on the NE thinned stnd s compred to the SW thinned stnd. In Septemer 22, TSNN rised gin on three stnds, mounting to highest concentrtions mesured during the growing seson 22 in phloem t the NE thinned site with 12.5 lmol N g 1 f.wt. The minimum remined t 2.8 lmol N g 1 f.wt t the SW control site. The dominnt mino compound ws Arg (28% of TSNN), followed y Al (18% of TSNN nd 48% of proteinogenic rest). Effects of exposition nd tretment were detected on the SW control site. TSNN nd ll mino compounds with the exception of mmonium were decresed in the phloem of trees from the SW control site s compred to the NE control site nd the SW thinned site, respectively. Moreover, TSNN concentrtions of NET exceeded tht of SWT. Throughout the two growing sesons in 1999 nd 22, nitrte in the phloem ws elow the limit of detection. Discussion In the present study we ssessed the effects of thinning under different meso-climtic conditions (temperture, wter vilility, rdition) on TSNN in xylem, leves nd phloem of dult eech trees during the growing sesons in 1999 nd 22. The two different yers were chosen in order to compre the nitrogen lnce shortly fter thinning tretment ws pplied nd 3 yers lter. The experimentl sites were locted on opposing slopes with different exposition (NE vs. SW) of nrrow vlley differing in locl climtic conditions. Previous studies reveled tht only trees growing on the SW spect were sujected to wter shortge during periods of low precipittion in summer, due to higher soil nd ir tempertures comined with lower wter storge cpcity of the soil compred to the NE spect (Geßler et l. 21). Findings for eech regenertion suggested tht N sttus nd uptke ws improved on the cool moist NE spect ut impired under the wrm dry conditions on the SW spect (Fotelli et l. 22, 24). Since not only ir tempertures ut lso prolonged drought periods during summer re expected to increse in frequency in Centrl Europe (IPCC 21; Schär et l. 24), this experimentl design is regrded pproprite to ssess the influence of climte chnge on the nitrogen nd,

11 11 thus, nutrient sttus of dult eech trees grown on limestone (Geßler et l. 24). Differences etween spects nd tretments in TSNN concentrtions in phloem, xylem nd leves t the eginning of the growing seson indicte differences in the timing of N remoilistion During oth the yers of mesurement, TSNN concentrtions of xylem nd leves reched their mximum in My, nd lso phloem TSNN concentrtions were generlly incresed compred to summer. Similr ptterns were oserved y Fotelli et l. (22) nd Schneider et l. (1996) for eech. The high TSNN concentrtions t the onset of the growing seson cn e ttriuted to xylem nd phloem loding of N compounds from storge tissue shortly efore nd during ud rek in order to supply newly developing leves. In My 1999, no significnt differences in TSNN concentrtions were oserved in the xylem (Fig. 4), ut considerle differences in TSNN concentrtions were found in leves (Fig. 6) nd phloem (Fig. 7). TSNN concentrtions in leves or phloem on the NEC, SWC nd SWT sites were similr nd only trees from the NET site showed divergent ptterns. In the phloem, TSNN ws mrkedly incresed minly due to high Arg, Gln nd Asn concentrtions, wheres concentrtion ws decresed in the newly developing leves. In My 22 such differences were not oserved. Then in contrst, TSNN concentrtion in the xylem sp ws lowest in trees from the NET site. The oserved ptterns of TSNN concentrtions of xylem sp nd phloem exudtes in My 1999 nd 22 my e ttriuted to differences in timing of N remoilistion etween the plots. Erly in the growing seson immeditely efore nd during ud rek, phloem trnsport is supposed to contriute to cropetl trnsloction of remoilised N compounds (D Silv nd Shelp 199). This view is supported here y the finding tht Arg, mjor N storge compound in eech (Geßler et l. 1998), is the most undnt N compound of the phloem exudtes in spring (Fig. 7). After unfolding of leves nd onset of trnspirtion, trnsport of solule N compounds vi the xylem is supposed to e the min N source for the developing leves (e.g. Peuke nd Kiser 1996). Geßler (1999) oserved strong increse in TSNN concentrtions in the phloem exudtes of eech out 2 weeks efore ud rek, which decresed gin shrply immeditely efore leves strted to unfold. Comprle peking of TSNN concentrtions ws lso found in leves nd xylem sp, ut showed time lg with mximum vlues during ud rek. Since verge ir tempertures mesured during the 4 weeks efore smpling in My 22 were lowest on the NE spect, prticulrly t the thinned site (NET: 6.4 C; NEC: 6.6 C, SWT: 6.9 C; SWC: 6.9 C) it is ssumed tht the strt of N remoilistion ws retrded t the NE thinned site. As consequence the pek in TSNN concentrtion in the xylem sp ws, in contrst to the other sites, not yet reched when the smples were tken. As the temperture ptterns determined in spring 22 were lso oserved in other yers (Keitel 24), it is concluded tht dely in spring remoilistion of stored N ws lso the reson for the low TSNN concentrtion in leves nd the mximum vlues in the phloem detected in the thinning tretment of the NE spect in In view of the fct tht Geßler (1999) oserved time-lg etween TSNN spring mximum in phloem exudtes nd leves; it is concluded tht the trees from the NEC, SWC nd SWT sites hd lredy een pssed the spring pek in the phloem nd reched the mximum of TSNN concentrtions in reking uds wheres the individuls from the NET site were hrvested when they showed mximum TSNN concentrtions in the phloem. These oservtions re supported y the ssessment of lef phenology (udding stge, lef development stge) during the growing seson in 2 (Kirchg ßner 21). It ws oserved tht ud rek nd unfolding of leves occurred erlier in the control tretments of the NE spect s compred to the respective thinning tretment. TSNN concentrtions in mid summer reflect environmentl differences etween yers, tretments nd spects In July 1999 nd 22, TSNN in xylem, leves nd phloem decresed hevily compred to My of oth yers, finding lso oserved in other studies with eech regenertion (Fotelli et l. 22) or dult eech nd spruce (Schneider et l. 1996). Lowered TSNN concentrtions in ll tissues during mid-growing seson cn e explined y lower N demnd of the lredy developed leves. The thinned stnds displyed significntly higher N mss flow nd TSNN concentrtions on oth spects in the xylem sp in July 1999 nd showed the sme tendency, lthough not significnt, in July 22. Higher N trnsport rtes in xylem in oth thinned stnds point to higher N vilility nd uptke or to intensive phloemto-xylem exchnge, oth leding to incresed xylem loding with mino compounds. Consistent with the first ssumption, incresing soil nutrient undnce within the first yers fter thinning hve een reported (Thiodeu et l. 2) nd etter wter supply for the remining trees hs een suggested (Lurent et l. 23). Moreover, N uptke in eech roots is positively correlted with soil temperture (Geßler et l. 1998), which ws elevted in the thinned stnds of ech spect (Tle 1). Hence, pedospheric N uptke might hve een fcilitted prticulrly in the first yer fter thinning, owing to lrge cnopy gps permitting incresed precipittion throughfll nd rdition perception (Tle 1). Highest TSNN concentrtions 3 yers fter the thinning tretment in phloem, leves nd xylem were found in the thinned stnd of the NE spect, indicting most fvourle growth conditions.

12 12 Geßler et l. (25) showed tht nitrte uptke potentil s well s pedospheric vilility of inorgnic N ws generlly higher t the NE s compred to the SW spect. Due to higher soil tempertures (Tle 1; Fotelli et l. 23; Holst et l. 24) nd reduced intrspecific competition, effective nitrte uptke is supposed to e highest in the NE thinning tretment, thus leding to the incresed solule N concentrtions oserved in 22. This result is consistent with findings from Fotelli et l. (24) who oserved thinning to cuse incresed N concentrtions in eech seedling on the NE spect. In July 1999, however, TSNN concentrtions in leves were lower in the thinning tretment on the NE site compred to the respective control nd even on oth SW sites, despite higher N mss flow in the xylem on oth thinned stnds nd, thus, puttive higher N supply of the crown. Since thinning induces strong increse in crown iomss in the first yer fter tretment (Mitscherlich nd Gnssen 1951), the reduced folir TSNN concentrtion my e ttriuted to dilution of nitrogen within the expnding crown, n effect not oserved 3 yers fter thinning tretment, when PAI ws incresed prticulrly t the thinned sites (Holst et l. 24) nd cnopy structure ws lrgely closed gin. Phloem TSNN concentrtions in lte summer re sensitive to tretment-specific onset of senescence In Septemer 22, TSNN nd prticulrly Arg concentrtions in the phloem on the SW site were significntly higher in the thinned stnd compred to the control stnd. Comprle leit not significnt ptterns were oserved in the sme yer t the NE spect nd in Septemer 1999 t oth spects. In 22, it is ovious tht lef TSNN concentrtions of trees from the NEC, NET nd SWT stnds decresed etween July nd Septemer, ut showed on the contrry strong increse in TSNN nd Arg in the phloem within the sme period of time. Rised Arg concentrtions in phloem were frequently oserved t the end of the growing seson, nd re supposed to indicte remoilistion of N from decomposed proteins in leves (Geßler et l. 1998; Fotelli et l. 22; Schneider et l. 1996). Phenologicl studies of Kirchg ßner (21) showed tht lef senescence (i.e. lef yellowing) strted slightly erlier in the thinned stnds. Thus, the significntly higher phloem TSNN concentrtion of the SW thinned stnd s compred to the control tretment in Septemer 22 my e result of the erlier onset of phloem trnsport of remoilised N from the senescing leves to the storge tissues in rk nd wood. Similrly, Grci-Plzol nd Becerril (21) oserved ntecedent onset of lef senescence in sun exposed eech leves s compred to shde leves, owing to erlier chlorophyll degrdtion. Moreover, the eginning of lef senescence is triggered y vriety of different iotic nd iotic fctors such s CO 2 concentrtions in the tmosphere (Sigurdsson 21), nutrient supply (Sigurdsson 21), metolic imlnce etween source nd sink t whole plnt level (Pul nd Foyer 21) or wter vilility (Amlin nd Rood 23; Pic et l. 22). Kirchg ßner (21) concluded tht the erlier initition of lef senescence in the thinned stnds ws due to incresed middy ir tempertures (Tle 1), leding to incresed evpotrnspirtion. As consequence soil wter vilility could e reduced fter periods of low rinfll in lte summer s in fct oserved for the thinning tretments on the SW spect (Geßler et l. 21), hence, leding to impired growth conditions. Yet, vriety of prmeters might interct in the regultion of senescence nd relted N storge processes. Conclusions Previous studies with eech reveled tht concentrtions nd compound profile of TSNN cn e sensitive indictor of short-term physiologicl responses to environmentl influence on trees (Geßler et l. 1998; Fotelli et l. 22), reflecting chnges in their internl nitrogen sttus in much more detil thn totl N concentrtions, which re constnt over wide rnge of climtic nd nutritionl conditions (Rennenerg et l. 1998; Geßler nd Rennenerg 2). In the present study we showed tht TSNN reflects sesonl chnges in the N lnce of dult eech s influenced y locl climte nd silviculturl tretment. Tking xylem sp flow densities into ccount, the ssessment of the TSNN concentrtions nd composition cn e used s tool to chrcterise N remoilistion nd storge ptterns. It ws shown tht the thinning tretment on the cool-moist NE spect resulted in retrded onset of N remoilistion, proly due to reduction of ir tempertures in erly spring. In mid summer, thinning resulted in enhnced cropetl N flow, indicting improved N vilility for the trees. This effect ws more pronounced in the yer following the silviculturl tretment thn 3 yers lter. Yet, thinning ccelerted remoilistion of structurl N from leves vi the phloem to storge tissues on the wrm-dry SWspect in lte summer, possily due to impired growth conditions. The ptterns of remoilistion nd storge fitted well with phenologicl oservtion mde t the experimentl sites. In July 22, during dvnced closure of the stnd cnopy, trees grown on the thinned stnd on the NE spect displyed mximum TSNN concentrtions in ll tissues. Thus, it is supposed tht the N lnce of dult eech is fvoured y thinning tretments s well s the cool-moist climte previling on the NE spect. On the other hnd, lower N concentrtions found in trees grown on the wrm-dry SW-spect my reflect the reduced tree growth s oserved y Geßler et l. (21). Acknowledgements This reserch ws prt of project funded y the Deutsche Forschungsgemeinschft under contrct numers

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