The effects of repeated cutting on coppice response of Terminalia sericea

Transcription

1 Trees (215) 29: DOI 1.17/s ORIGINAL PAPER The effets of repeted utting on oppie response of Terminli serie Hloniphni Moyo M. C. Sholes W. Twine Reeived: 2 Jnury 214 / Revised: 17 August 214 / Aepted: 25 Septemer 214 / Pulished online: 9 Otoer 214 Ó The Author(s) 214. This rtile is pulished with open ess t Springerlink.om Astrt Key messge Although exposure to multiple utting yles redues stored reserves, shoot dimeter nd shoot length, it, however, inreses shoot prodution per resprouting stump nd folir nitrogen. Astrt In disturne-prone environments with flututing sesonl rinfll suh s svnns, the repeted utting of the sme trees eventully results in possile deline in tree undne. The effets of sujeting Terminli serie trees to one, two nd multiple (eight) utting events over period of 2 yers on oppie response were investigted in svnn woodlnd in South Afri. Resprout shoot dimeter, shoot length nd the totl umultive dimeter were lower in trees exposed to high numer of utting events ompred to trees exposed to one utting event. Inresing the numer of utting events signifintly redued stem totl non-struturl rohydrte levels in trees inditing depletion of stored reserves. Folir ron ontent remined lrgely the sme, while lef nitrogen nd phosphorus onentrtions signifintly inresed with eh utting event, reltive to unut trees. Results indite tht trees ut one hd not replenished depleted rohydrte reserves even fter period of 18 months during whih no utting took ple. Sustinle Communited y K. Msk. H. Moyo M. C. Sholes W. Twine Authors Shool of Animl, Plnt nd Environmentl Sienes, University of the Witwtersrnd, WITS 25, Johnnesurg, South Afri Present Address: H. Moyo (&) Wits Rurl Fility, P/Bg X42, Aornhoek 136, South Afri e-mil: hmthunzi@gmil.om utiliztion of this tree speies must llow for t lest more thn 18 months of undistured growth etween hrvests to llow for the replenishing of reserves. Keywords Repeted utting Coppie response Stored reserves Totl non-struturl rohydrtes Depleted Replenishment Introdution There is muh onern out the sustinility of intensive utting of trees for firewood in ommunl rngelnds in Afri (Twine et l. 23; Kshul et l. 25; Neke et l. 26; Shkelton et l. 24). Cumultive over-hrvesting in these res hs ontriuted to degrded woodlnds nd thus diminished the vilility of wood s soure of energy. Intensive utting of trees severely depletes stored ron reserves nd potentilly redues growth. The proess of replenishing stored rohydrte reserves is lrgely dependent on trees striking the lne in eing le to photosynthesize effiiently, grow suffiiently nd then eing le to hve exess ron for storge; ll of this eing dependent on soil moisture ontent nd nutrient sttus (Cruz et l. 23). However, little is known out the ftors tht ontrol the reserve ontent of plnt, how muh of the reserve is utilized fter disturne suh s hrvest (Cruz et l. 23), nd the hnges in the reovery of nutrients suh s nitrogen nd ron lost during disturne. These ftors hve signifint implitions for the sustinle use of rngelnds sujeted to intensive wood hrvesting. In systems prone to disturnes, suh s svnns, the ility of svnn tree speies to oppie is key ttriute of their resiliene nd produtivity (Shkleton 21;

2 162 Trees (215) 29: Kshul et l. 25) euse oppie growth is tolernt of drought nd nutrient-poor soils (Kennedy 1998; Kshul et l. 25). However, the ility of woody plnt to oppie nd remin vigorous lrgely depends on the severity of the disturne with referene to ove ground iomss, vilility of wter nd nutrients, nd lso on the vilility nd moiliztion of resoures ove nd elow-ground (Nzund et l. 28). Although resprouting hs eome reognized s key funtionl trit in plnt eology over the pst dede (Lwes nd Clrke 211), there is still limited informtion out the physiology nd growth strtegies of resprouting trees in svnns (Neke 24; Pote et l. 26). Aville informtion out the influene of disturne nd utting frequeny omes from eosystems tht re different when ompred with svnns. Coppiing is generlly the primry regenertion mehnism fter woody plnt hs een ut or severely dmged, where stem nd roots remin in ple (Forrester et l. 23). As mngement tool, it hs een proposed s method for minimizing dmge to indigenous vegettion through sustinle fuelwood prodution (Kennedy 1998). This is euse oppie shoots grow fster thn seedlings nd they exhiit pil dominne, produing woody mteril for homested utiliztion (Kennedy 1998; Hrdesty 1987). The resprouting ility of plnt n hve mjor impts on tree reovery nd reestlishment to redue eosystem dependene on seed prodution nd germintion for popultion mintenne nd growth, euse seedling estlishment is not relile mens of re-estlishment, espeilly where resoures suh s wter re limited (Bond nd Midgley 21). The effet of ontinued shoot removl on totl nonstruturl rohydrtes nd regrowth of trees is poorly understood (Crpenter et l. 28; Luostrinen nd Kuppi 25), espeilly in semi-rid, nutrient-poor rngelnd eosystems. In ddition, the role of rohydrte reserves in regrowth of intensively hrvested woody speies remins unler, nd therefore merits ttention onsidering tht some studies hve suggested tht trees moilize stored nitrogen for use in regrowth insted of stored rohydrtes (Druege et l. 2; El Omri et l. 23; Wendler et l. 1995; Millrd nd Proe 1992). Sine the vilility of stored reserves is entrl to the vegettive regenertion fter utting event, trees will respond through lloting resoures to growth or defene strtegies (Rooke nd Bergstrom 27). This llotion of resoures is determined y vrious ftors whih inlude the vilility of wter, nutrients nd sunlight during nd fter the disturne, nd the severity of dmge on the plnt used y the disturne (Ktjiu nd Wrd 26). For plnts, it is iologil dvntge to hve redily ville soure of energy fter disturne (Fornr nd Du Toit 27). This is euse vegettive prts need to e mintined to initite estlishment of new photosyntheti surfes for shoot reovery (Bowen nd Pte 1993; Luostrinen nd Kuppi 25; Kozlowski 22). Some woody plnts store enough rohydrte reserves in stumps nd roots to meet more thn one resprouting event following disturne (Crpenter et l. 28; Luostrinen nd Kuppi 25). To reover fter rowsing event whih removes lef mteril, plnt needs vile meristems nd ron reserves, t lest until new shoots eome funtionl nd n photosynthesize (Key nd Ski 25). Resprouting trees lso rely on stored rohydrte reserves to support growth nd respirtion until suffiient lef re hs een regrown for ron ssimiltion to meet growth demnds (Chpin et l. 199; Bond nd Midgley 21). When photosynthetilly effiient, resprouting plnt n reh pek growth nd then llote ron towrds storge (Key nd Ski 25). For exmple, Vn der Heyden nd Stok (1996) showed tht fter rnh utting, regrowth of the shru Osteospermum sinutum Norl. ws dependent on stored ron nd this reline shifted to photosynthtes produed y new nd remining leves. Cndell nd Lopez-Sori (1998) lso demonstrted tht lrge mount of totl non-struturl rohydrtes re moilized when Eri rore L. nd Arutus unedo L. were exposed to multiple lipping events. Bowen nd Pte (1993) found tht prodution of Stirlingi ltifoli R. Br. deresed due to suessive hrvests, with root strh reserves higher for plnts tht were urnt one nd llowed to reover ompred to trees tht were urnt nd lipped. Shoot prodution ws lower in frequently ut Gliriidi sepium (Jq) ompred to less frequently ut trees (Erdmnn et l. 1993). Also, repeted lipping of the Eulyptus kohii Miden resulted in eventul deth of the tree, with TNC reserves shown to e higher for trees not ut ompred to trees reovering from single ut (Wildy nd Pte 22). The ojetive of this study ws to investigte how repeted utting of trees ffets their ility to regenerte nd lso how the onentrtion of stem-stored reserves hnges, s well s folir ron (C), nitrogen (N) nd phosphorus (P). It ws hypothesized tht repeted utting negtively ffeted resprouting fter 2 yer utting period, while lso signifintly reduing stem totl nonstruturl rohydrtes nd inresing folir N nd P ut with no effets on folir C. Methods Study site The study ws onduted t the Wits Rurl Fility (WRF), 35-h reserh sttion owned y the University of the

3 Trees (215) 29: Witwtersrnd, in the entrl svnn lowveld eoregion of Limpopo Provine, South Afri (24 o 3 S; 31 6 E). The study site is semi-rid, with men nnul preipittion (MAP) of *65 mm, onentrted in the summer seson (etween Otoer nd April) (Kshul et l. 25; Shkleton 1997; Neke et l. 26). The study spnned 2-yer period (Sept 21 Sept 212), strting t the end of the dry seson of 21, during the period when trees egin lef-flush. Rinfll totls over the study period were oveverge (825 nd 915 mm in yers 1 nd 2, respetively). The men nnul temperture is 22 C (Neke et l. 26; Shkleton 1993). Drought events re ommon nd our out every 4 yers (Neke 24). The most ommon soil types in this region re the shllow, sndy, nutrient poor lithosols, underlin y grniti gneiss (Shkleton 21; Neke et l. 26; Kshul et l. 25; 25). The vegettion is dominted y tree speies in the Comretee (notly Terminli serie) s well s Mimosee (e.g. Ai gerrrdii Benth) fmilies, hrteristi of the Mixed Lowveld Bushveld vegettion type (Shkleton 21; Neke et l. 26; Shkleton 1993). Study speies The speies hosen for this study ws Terminli serie Burh. ex. DC, lso known lolly s silver luster lef. It is ommon tree speies in dystrophi svnns ourring from Tnzni nd the Demorti Repuli of Congo, southwrds to Angol, Nmii, Zimwe, Botswn nd South Afri (Cotes-Plgrve 22). T. serie is medium sized semi-deiduous tree speies, growing (when unoppied) s single-stemmed tree rehing up to 8 m in height or multi-stemmed shru 4 6 m tll (Cotes-Plgrve 22). T. serie is prtiulrly prolifi on the mid-slope seeplines of these eozones, where it grows in dense groups of vrious sizes forming thikets produing very lrge iomss (Amri 211). It is one of the most ommonly used fuelwood speies in mny prts of southern Afri, nd is lso used for mediinl purposes suh s uring dirrhoe, in rurl ommunities (Crr 1994; Neke 24). T. serie ws hosen s the study speies euse more knowledge of its regenertive pity n ontriute to mngement reommendtions for sustinle utiliztion. This ws lso euse of its high pity for oppiing nd its tendeny to form thik stnds (Shkleton 1993; Neke 24; Shkleton et l. 24). Experimentl proedure A ompletely rndomized experiment with three tretments replited t three sites ws estlished in Septemer 21, to determine the effets of repeted utting on the oppie response of ut trees. Ten trees were seleted per tretment plot, numering totl of 9 trees for the experiment. Although there were differenes in initil stump dimeter, single-stump trees were seleted sed on initil tree stump dimeter; whih ws stndrdized (from 5 to 9 m) to ontrol its effets on oppie response. In ses where single stump trees ould not e used, multi-stump trees of omined dimeter rnging etween 5 nd 9 m were used. Stumps of tht dimeter rnge were onsidered mediumsized nd were hosen euse it hs een suggested tht lrger stumps tke shorter time to respond to utting event, positively influening initil oppie growth through hving lrger residul root system (Shkleton 1997). Trees were exposed to three utting regimes over 2-yer period, sed on pilot studies nd unpulished dt on tree utting intensities in the nery ommunl lnds. Tretments egn in Septemer 21 to Septemer 212 s follows (Fig. 1) 1. Cut one over the 2 yer period in Septemer 212, termed utting regime (CR); 2. Cut twie over the 2 yer period in Septemer 21 nd in Septemer 212, utting regime (CR), nd 3. Cut in three-month yles over the 2-yer period eginning in Septemer 21 nd ending in Septemer 212, resulting in eight suessive utting events, utting regime (CR). For the first ut under eh regime, trees were ut t height of pproximtely, 25 m from the ground. Sine reserh hs shown tht the prodution of resprouting shoots inreses with utting height (Shkleton 1997; Khn nd Tripthi 1986; Irhim et l. 27; Kshul et l. 25), the height used in this study ws kept onstnt to minimize its effets on resprouting. Suessive hrvests for CR nd CR were done through removing ll resprouting shoots from the stumps. Morphology mesurements Monitoring of trees for morphologil hnges strted t the end of Otoer 212 nd ended t the end of Ferury 213 euse trees in CR were eing used in other experiments. For eh resprouting stump, the following vriles were mesured monthly: (1) totl numer of shoots resprouting, (2) numer of leves on the leder shoot, (3) shoot length on the leder shoot nd (4) shoot dimeter on the leder shoot. Shoot prodution ws lulted s the numer of shoots produed per unit re of stump whih ws lulted from the stump dimeter, while totl umultive dimeter (TCD) ws lulted s the produt of the dimeter of eh leder shoot nd the totl numer of shoots produed per stump. The ssumption ws tht the dimeter mesured on eh of the leder

4 164 Trees (215) 29: Shoot prod (m -2 ) A Ot-12 Nov-12 De-12 Jn-13 Fe-13 Months CR1 CR2 CR3 Men no. of leves B Ot-12 Nov-12 De-12 Jn-13 Fe-13 Shoot dim (m) D Shoot length (m) C CR1 CR2 CR3 Ot-12 Nov-12 De-12 Jn-13 Fe-13 Ot-12 Nov-12 De-12 Jn-13 Fe-13 Totl umul ve dimeter (m) E Ot-12 Nov-12 De-12 Jn-13 Fe-13 Months CR CR CR Fig. 1 The monthly effets of exposing T. serie to different utting regimes on shoot prodution, men numer of leves, resprout shoot dimeter, d resprout shoot length nd e totl umultive dimeter from Otoer 212 to Ferury 213. Mens within month hving different smll letters (,, ) re signifintly different t p \.5. Men differenes for men numer of leves s indited y the smll letters (,, ) were ompred using simple mens omprisons. CR ut one, CR ut twie, CR ut eight times. Mens re represented with stndrd error rs resprouting shoots ws representtive of the men of ll resprouting shoots per stump. Aove-ground storge nlysis Totl non-struturl rohydrte reserves were determined for ll experimentl trees using wood ores, eh of 3 m long with dimeter of 4.3 mm. Sine mesurements were mde efore the end of the experiment, smples were olleted from the unut, trees ut one nd trees ut seven times t the time of smpling. Two ores were extrted per tree stump (t 7 nd 2 m ove soil level) using n inrement orer, t the end of the growing seson in April 212. This mens stem smples were olleted when CR trees hd een ut seven times, CR trees hd een ut one nd CR trees hd not een ut t the time of smple olletion. Before storing the ores in irtight plsti ottles, the outer tree rk ws immeditely removed from ores fter smpling. The ore smples were then ottled nd pled inside freezer. Drying of smples ws done t

5 Trees (215) 29: C for 2 dys (ssumed dry) nd then smples ground using offee grinder efore finer grinding through 4 lm-mesh Wiley mill sreen, t the University of Florid, USA. A omposite smple ws otined fter grinding. The TNC ws determined on dry weight sis using the nthrone method desried y Edwrds et l. (211). The TNC vlues reported here re the sum of the solule (gluose nd surose) nd insolule (strh) frtions. Folir nlysis For C, N nd P levels, lef smples were olleted from unut trees nd trees ut seven times t the end of the 18-month smpling period (end of Mrh 212). Trees from CR were eing used for nother experiment t the time smpling nd ould not e used t tht time. Leves were olleted month fter lef flushing t the eginning of eh growing seson during the study (end of Septemer 21 nd 211), nd in the middle of eh growing seson during the study (Jnury 211, 212), when lef prodution ws ssumed to e t its highest, nd t the end of eh growing seson during the study (Mrh 211, 212). Leves were not olleted in the dry sesons during the study euse trees were shedding leves during tht period (i.e. etween June nd August). Leves olleted were oven-dried t 6 C for 48 h nd then ground using the Wiley mill. Lef smples from totl of seven hrvests ( period of 18 months) were tken to the University of Florid Lortory for C, N nd P onentrtion nlyses. Totl C nd N were mesured using Costeh ECS 41 Elementl Anlyzer (Vleni, CA, USA), while P ws mesured using the modified single solution method desried y Murphy nd Riley (1962). Sttistil nlyses The totl numer of shoots, shoot dimeter nd length dt were log-trnsformed euse dt were not normlly distriuted, prior to nlysis. No other dt were logtrnsformed. For the response vriles of numer of shoots on resprouting trees nd men numer of leves on resprouting shoots generlized liner mixed model (GLMM) ws fitted y onsidering n underlied Poisson distriution with logit link. The liner model inluded the fixed effets of utting regime. In ddition, rndom terms of site nd tree within site were inluded. All models were fitted using the proedure GLIMMIX s implemented in SAS v. 9.2 (SAS Institute, Cry NC, USA). Signifine of fixed effet terms were evluted with n pproximted F-test, nd men omprisons etween regimes were otined using lest squre mens with Dunnett s T3. The simple mens omprison (unproteted) ws used to otin the level of signifine for the totl numer of shoots. The effets of repetedly utting T. serie on oppie response (shoot dimeter nd length), totl non-struturl rohydrtes were nlysed using nlysis of vrine, while the effets of utting on C, N nd P levels were nlysed using the repeted mesures nlysis of vrine. Dunnett s T3 test ws used for men omprison t p \.5 (Tle 1). Results Effets on oppie response The totl numer of shoots ws signifintly higher in CR trees ompred to CR in Otoer 212, Jnury nd Ferury 213, while there were no signifint differenes in the totl numer of shoots due to tretment effets in Deemer 213 (Tle 2). Exposing T. serie to different utting regimes hd signifint effets on the oppie response of resprouting trees. Shoot prodution ws signifintly higher in repetedly ut trees (CR) through-out the monitoring period ompred to the other tretments Tle 1 The representtion of tretments in the study in three sites showing the three tretments rndomly lloted to eh site Site 1 Site 2 Site 3 Cut one (Septemer 212) (CR) Cut in 3-month yles from Septemer 21 till Septemer 212 Cut twie; (1) Septemer 21 (2) Septemer 212 Cut one (Septemer 212) (CR) Cut in 3 month yles from Septemer 21 till Septemer 212 Cut one (Septemer 212) (CR) Cut twie; Cut in 3 month Cut twie; (1) Septemer 21 yles from (1) Septemer 21 Septemer 21 till (2) Septemer 212 (2) Septemer 212 Septemer 212 Tle 2 The monthly effets of exposing T. serie to different utting regimes on the totl numer of shoots CR CR CR Totl no. of shoots Otoer 15 ± 4 27 ± 5 22 ± 5 Novemer 2 ± 6 24 ± 5 23 ± 5 Deemer 29 ± 6 3 ± 5 33 ± 4 Jnury 25 ± 5 32 ± 5 33 ± 4 Ferury 18 ± 3 22 ± 6 24 ± 4 Supersript letters ompre tretment mens within month. Mens with different letters (, ) indite signifine ross tretments (tested using simple mens omprisons). Mens re represented with the stndrd devition CR ut one, CR ut twie, CR ut eight times

6 166 Trees (215) 29: (Fig. 1). In some instnes, e.g. in Novemer 212 nd Ferury 213, differenes etween trees ut one (CR) nd trees ut twie (CR) in shoot prodution were not signifint. For the numer of leves produed, there were no signifint differenes etween CR nd CR trees in Otoer 212, Novemer 212 nd Jnury 213, while CR nd CR trees hd signifintly higher men lef numers ompred to CR trees in Deemer 212 nd Ferury 213 (Fig. 1). Resprout shoot dimeter nd shoot length for CR nd CR trees (Fig. 1, d) were signifintly higher thn those for CR trees throughout the study, while CR trees reorded higher resprout shoot length nd shoot dimeter thn CR trees from Novemer 212 onwrds. The TCD ws signifintly lower in CR trees ompred to the other tretments from Novemer 212 onwrds (Fig. 1e). Effets on totl non-struturl rohydrtes (TNC) Exposing T. serie to different utting regimes hd signifint effet on TNC levels, with levels delining signifintly with n inrese in the utting frequeny (Fig. 2). The TNC levels in trees ut seven times t the time of smpling were one-third tht of unut trees, while levels in trees ut one were hlf the levels in unut trees. Effets on Folir C, N nd P levels (%) There ws signifint utting effet (F = 42.97; p \.5) of trees on folir N levels (Fig. 3). Cutting trees from the period Septemer 21 to Mrh 212 (time effet) lso hd n overll positive signifint effet (F = 27.73; p \.5) on folir N levels of ut trees, while there ws lso signifint intertion etween time (period of exposure to utting tretments (Septemer 21 Mrh 212) nd utting effet (F = 3.87; p \.5) on N TNC (mg g -1 ) Unut Cut one Cut 7- mes Tretments Fig. 2 Men (dry weight) totl non-struturl rohydrtes (TNC) in three hrvesting regimes in April 212. Brs with different smll letters (,, ) indite signifint differenes t p \.5. Mens re represented with stndrd error rs levels. There were no signifint utting effets (F = 1.17; p [.5) on folir C levels. The period of exposure to utting tretments lso hd no signifint effet on C levels (F =.42; p [.5), nd there ws no signifint intertion (F = 2.49; p [.5) etween time nd utting effets on C levels (Fig. 3). There ws signifint utting effet (F = 9.92; p \.5) of trees on folir P levels. The time effet lso hd signifint positive effet (F = 6.85; p \.5) on P levels, while there ws lso signifint intertion etween the time effet nd utting effet (F = 5.49; p \.5) (Fig. 3). Disussion Effets on oppie response The higher shoot prodution, ut with fewer leves for the repetedly ut trees my hve een response to inrese the surfe re for photosynthesis, inresing ron ssimiltion for use in either growth or replenishment of stem rohydrte reserves. High shoot prodution in repetedly ut trees my lso hve een result of higher reserve moiliztion lte in the dry seson nd erly into the growing seson s suggested y Wildy nd Pte (22); Cruz nd Moreno (21). However, the reltive derese in the resprout shoot dimeter in repetedly ut trees ws not off-set y the reltive inrese in the totl numer of shoots nd lso with the high shoot prodution in repetedly ut trees not ompensting for the disdvntge of the smll size of the resprouting shoots. Sine stored TNC reserves re the most importnt soure of ron to support growth nd reovery of plnt fter disturne (Cndell nd Lopez-Sori 1998; Chpin et l. 199; Vn der Heyden nd Stok 1996), the similrities in the response of trees ut one nd trees ut twie n e explined with referene to flututions in stored rohydrte reserves. This is euse trees ut twie were not ut until fter 2-yer period, thus potentilly llowing restortion of stored reserves moilized fter the first ut in 21. Erly growth of shoots is ssoited with the moiliztion of previously umulted reserves of either nutrients or strh (Ltt et l. 2; Gri et l. 21; Cndell nd Lopez-Sori 1998). Repetedly ut trees hd the lowest oppie response when onsidering the other response vriles in this study other thn shoot prodution minly euse insuffiient time for TNC replenishment etween suessive utting events ws short s suggested y Ltt et l. (2). For this study, the 3-month period etween the utting events ws proly not suffiiently long to llow for trees to regrow nd estlish new photosyntheti mss.

7 Trees (215) 29: Fig. 3 Men (%) nitrogen, ron nd phosphorus folir onentrtions of trees Cut 7-times nd Unut trees (from Septemer 21 to Mrh 212) (Cut 7-times represents trees from CR, while Unut represents CR trees). Mens re represented with stndrd error rs Effets on stem TNC levels After 18 months of reovery, trees ut one hd not restored TNC levels to levels in unut trees. The expettion ws tht fter more thn yer of regrowth, TNC levels would hve rehed those of unut trees. Bowen nd Pte (1993), proposed tht TNC reserve levels initilly derese fter utting event nd tht the reserve levels re expeted to inrese only fter shoot iomss hs rehed similr levels to tht efore utting. Trees ut one hd signifintly higher TNC levels ompred to repetedly ut trees euse there ws regrowth period of more thn yer, during whih the trees hd the opportunity to lne the TNC sink nd soure tivity tht ws shifted fter utting. The results imply tht when trees re ut one, higher quntities of TNC reserves re moilized for regrowth ompred to when trees re ut seven times. Results from the study gree with other studies in whih TNC reserves in woody plnts hve een shown to derese s regrowth ourred fter utting, urning nd defolition (Miynishi nd Ellmn 1986; Bowen nd Pte 1993; Cndell nd Lopez-Sori 1998; Lndhusser nd Lieffers 22; Shutz et l. 29; MPherson nd Willims 1998; Luostrinen nd Kuppi 25). Conentrtions of TNC were lso highest in trees ut less frequently ompred to trees hrvested more frequently in Gliriidi sepium (Jq.) (Gri et l. 21), in Slix nigr (Crpenter et l. 28) nd lso in Populus mximowizii (Henry) (Tshplinski nd Blke 1995). Effets on Folir properties Sujeting trees to repeted utting signifintly inresed lef N ompred to unut trees, espeilly fter 18 months. Lef smples my hve een of different ges, leding to younger leves in repetedly ut trees hving higher N levels. The C:N rtio in trees ut seven times ws 18 wheres in the unut trees it ws 33. This implies tht the trees ut multiple times umulted signifintly more N in their tissue reltive to C ompred with trees whih were unut. This evidene points to the hnged metoli stte of younger leves in the multiple ut trees. Alterntively, n inrese in lef N n lso e explined y inresed investment in the prodution of lef defenes suh s lkloids (Eloff et l. 28; Onod et l. 24) euse

8 168 Trees (215) 29: high levels of polyhydroxylkloids hve een found in T. serie (Eloff et l. 28; Ktjiu nd Wrd 26). Short-term responses to ove ground rnh removl in Comretum piultum Sonder showed tht over the seson, lef N levels were higher on severely defolited trees ompred to trees not defolited (Rooke nd Bergstrom 27). Lef N levels were higher for Crdiopetlum llophylum (Annonee) nd Mproune guinensis (Euphoriee) trees lipped monthly ompred to trees lipped fter every 3 months (Mundim et l. 212). There were lso higher lef N levels on hevily rowsed Ai nigresens, Miller, ompred to lightly rowsed trees (Fornr nd Du Toit 27). Sine trees were smpled for TNC fter seven events, it would e interesting to follow how the TNC levels hnge s the utting yles re inresed to more thn seven euse it hs een proposed tht mortlity in trees eventully ours if the reserves re suffiiently depleted through trees eing repetedly lipped (Cruz et l. 23; Miynishi nd Ellmn 1986; Wildy nd Pte 22). Implitions Repetedly ut trees utilized TNC reserves fter every utting event, depleting stored reserves nd ontriuting to redued oppie response. Although utting trees repetedly my result in the highest numer of resprouting shoots, this my not neessrily result in higher resprouting or regrowth rtes euse the dimeter of the shoots do not ompenste for the higher numer of shoots produed to inrese the resprouting response. The period etween suessive utting events is ritil for replenishing stored TNC reserves. To ensure sustinle utiliztion, this study indites tht trees require t lest minimum period of more thn 3 months to replenish stored reserves. This would llow the reovery nd replenishing of TNC reserves etween suessive utting events nd redue the possiility of exhusting reserves, with the potentil for ultimte mortlity. It is proposed tht rottionl period or reovery time of t lest 6 months e used to llow trees to replenish prt of the stored reserve moilized fter the initil hrvest. Authors ontriution sttement H. Moyo s the first uthor, designed the study, rried out the field work nd dt olletion inluding the nlysis nd writing up of the pper. M. C. Sholes s the o-supervisor, ssisted with guiding the first uthor nd reding drfts of the pper. W. Twine- s the prinipl supervisor, red nd orreted drfts of the pper s well s formulting the study design. Aknowledgments Reserh ws funded y the Andrew Mellon Foundtion nd the Centre for Tree Helth nd Biotehnology, University of Pretori. The ssistne of Juli Reiskind, Mihelle Mk, Rirdo Holdo, Ed Witkowski nd Slly Arhild is gretly ppreited. The WRF mngement is knowledged for llowing ess to the study site. Conflit of interest of interest. The uthors delre tht they hve no onflit Open Aess This rtile is distriuted under the terms of the Cretive Commons Attriution Liense whih permits ny use, distriution, nd reprodution in ny medium, provided the originl uthor(s) nd the soure re redited. Referenes Amri E (211) Germintion of Terminli serie Buh. ex seeds: the effets of temperture regime, photoperiod, gierelli id nd potssium nitrte. Int J Appl Biol Phr Teh 2(2):14 11 Bond WJ, Midgley JJ (21) Eology of sprouting in woody plnts: the persistene nihe. Trends Eol Evol 16(1):45 51 Bowen BJ, Pte JS (1993) The signifine of root strh in post-fire shoot reovery of the resprouter Stirlingi ltifoli R. Br. (Proteee). Ann Bot 72:7 16 Cndell J, Lopez-Sori L (1998) Lignotuer reserves support regrowth following lipping of two Mediterrnen shrus. Funt Eol 12:31 38 Crpenter LT, Pezeshki SR, Shields FD Jr (28) Responses of nonstruturl rohydrtes to shoot removl nd soil moisture tretments in Slix nigr. Trees 22: Crr JD (1994) The propgtion nd ultivtion of indigenous trees nd shrus on the Highveld. Sndton Nture Conservtion Soiety nd the Tree Soiety of Southern Afri, Johnnesurg Chpin FS III, Shulze E, Mooney HA (199) The eology nd eonomis of storge in plnts. Annu Rev Eol Syst 21: Cotes-Plgrve M (22) Trees of Southern Afri. In: Cotes- Plgrve K (ed) Trees of Centrl Afri. Struik Pulishers, Cpe Town Cruz A, Moreno JM (21) Sesonl ourse of totl non-struturl rohydrtes in the lignotuerous mediterrnen type shru Eri ustrlis. Oeologi 128: Cruz A, Perez B, Moreno JM (23) Plnt stored reserves do not drive resprouting of the lignotuerous shru Eri ustrlis. New Phytol 157: Druege U, Zerhe S, Kdner R, Ernst M (2) Reltion etween nitrogen sttus, rohydrte distriution nd susequent rooting of Chrysnthemum uttings s ffeted y pre-hrvest nitrogen supply nd old-storge. Ann Bot 85: Edwrds EJ, Downie AF, Clingeleffer PR (211) A simple miroplte ssy to quntify non-struturl rohydrtes of Grpevine tissues. Am J Enol Viti 62(1): El Omri B, Arnd X, Verdguer D, Psul G, Flek I (23) Resoure remoiliztion in Querus ilex L. resprouts. Plnt Soil 252: Eloff JN, Kterere DR, MGw LJ (28) The iologil tivity nd hemistry of the southern Afrin Comretee. J Ethnophrmol 119: Erdmnn TK, Nir PKR, Kng BT (1993) Effets of utting frequeny nd utting height on reserve rohydrtes in Gliriidi sepium (Jq.) Wlp. For Eol Mnge 57:45 6 Fornr DA, Du Toit JT (27) Browsing lwns? Responses of Ai nigresens to ungulte rowsing in n Afrin svnn. Eology 88(1):2 29 Forrester D, Buhus J, Connell M (23) Competition in thinned Silvertop Ash (Eulyptus sieeri L. Johnson) stnds from erly oppie growth. For Eol Mnge 174(1 3): Gri H, Nygren P, Desfontines L (21) Dynmis of nonstruturl rohydrtes nd iomss yield in fodder legume tree t different hrvest intensities. Tree Physiol 21: Hrdesty LH (1987) Coppiing: using forester s tool on rngelnds. Rngelnds 9(3):

9 Trees (215) 29: Irhim A, Mpongmetsem PM, Bouitng D, Hssn B (27) Regenertion of some fuelwood tree speies of humid svnn of Admw, Cmeroon: effets of seson nd utting height. Ghn J Si 47:45 57 Key D, Ski S (25) The reltive importne of rohydrte nd nitrogen for the resprouting ility of Querus rispul seedlings. Ann Bot 96: Kshul S, Twine W, Sholes M (25) Coppie hrvesting of fuelwood speies on South Afrin ommon: utilizing sientifi nd indigenous knowledge in Community Bsed Nturl Resoure Mngement. Hum Eol 33: Kshul SA, Twine WC, Sholes MC (25) The effet of ten position nd stump hrteristis on the oppie response of three svnnh fuelwood speies. Environ Conserv 32(1):76 84 Ktjiu M, Wrd D (26) Resistne nd tolerne of Terminli serie trees to simulted herivore dmge under different soil nutrient nd moisture onditions. J Chem Eol 32(7): Kennedy AD (1998) Coppiing of Tronnthus mphortes (Composite) s soure of sustinle fuelwood prodution: n exmple from the Likipi Plteu, Keny. Afrin. J Eol 36: Khn ML, Tripthi RS (1986) Tree regenertion in distured sutropil wet hill forest of north-est Indi: effet of stump dimeter nd height on sprouting of four tree speies. For Eol Mnge 17: Kozlowski TT (22) Physiologil eology of nturl regenertion of hrvested nd distured forest stnds: implitions for forest mngement. For Eol Mnge 158(1 3): Lndhusser SM, Lieffers VJ (22) Lef re renewl, root retention nd rohydrte reserves in lonl tree speies following ove-ground disturne. J Eol 9: Ltt CR, Nir PKR, Kng BT (2) Intertions mong utting frequeny, reserve rohydrtes, nd post-utting iomss prodution in Gliriidi sepium nd Leuen leuoephl. Agrofor Syst 5:27 46 Lwes MJ, Clrke PJ (211) Eology of plnt resprouting: popultions to ommunity responses in fire-prone eosystems. Plnt Eol 212: Luostrinen K, Kuppi A (25) Effets of oppiing on the root nd stump rohydrte dynmis in irhes. New For. 29: MPherson K, Willims K (1998) The role of rohydrte reserves in the growth, resiliene, nd persistene of ge plm seedlings (Sl plmetto). Oeologi 117: Millrd P, Proe MF (1992) Storge nd internl yling of nitrogen in reltion to sesonl growth of Sitk sprue. Tree Physiol 1:33 43 Miynishi K, Ellmn M (1986) The role of root nutrient reserves in regrowth of two svnn shrus. Cn J Bot 64: Mundim FM, Brun EM, Vieir-Neto EHM, Vsonelos HL (212) Attk frequeny nd the tolerne to herivory of Neotropil svnn trees. Oeologi 168: Murphy J, Riley JP (1962) A modified single solution method for the determintion of phosphte in nturl wters. Anl Chim At 27:31 36 Neke KS (24) The regenertion eology of svnn woodlnds in reltion to humn utilistion. University of the Witwtersrnd, Johnnesurg Neke KS, Owen-Smith N, Witkowski ETF (26) Comprtive resprouting response of Svnn woody plnt speies following hrvesting: the vlue of persistene. For Eol Mnge 232(1 3):114 Nzund EF, Griffiths ME, Lwes MJ (28) Sprouting y remoiliztion of ove-ground resoures ensures persistene fter disturne of ostl dune forest trees. Funt Eol 22: Onod Y, Hikosk AK, Hirose T (24) Allotion of nitrogen to ell wlls dereses photosyntheti nitrogen-use effiieny. Funt Eol 18: Pote J, Shkleton C, Coks M, Luke R (26) Fuelwood hrvesting nd seletion in Vlley Thiket South Afri. J Arid Environ 67(2): Rooke T, Bergstrom R (27) Growth, hemil responses nd herivory fter simulted lef rowsing in Comretum piultum. Plnt Eol 189: Shutz AEN, Bond WJ, Crmer MD (29) Juggling ron: llotion ptterns of dominnt tree in fire-prone svnn. Oeologi 16: Shkelton CM, Grundy IM, Willims A (24) Use of South Afri s woodlnds for energy nd onstrution. In: Lwes MJ, Eeley HC, Shkleton CM, Geh BGS (eds) Indigenous forests nd woodlnds in South Afri: poliy, people nd prtie. University of Kwzulu Ntl Press, Pietermritzurg, pp Shkleton CM (1993) Fuelwood hrvesting nd sustinle utilistion in ommunl grzing lnd nd proteted re of the Estern Trnsvl lowveld. Biol Conserv 63: Shkleton CM (1997) The predition of woody plnt produtivity in the Svnn iome. University of the Witwtersrnd, Johnnesurg Shkleton CM (21) Mnging regrowth of n indigenous svnn tree speies (Terminli serie) for fuelwood: the influene of stump dimensions nd post-hrvest oppie pruning. Biomss Bioenerg 2: Shkleton CM, Buiten E, Anneke W, Bnks D, Bester J, Everson T, Friius C, Hm C, Kees M, Modise M, Phgo M, Prsd G, Smit W, Twine W, Underwood M, von Mltitz G, Wenzel P (24) Fuelwood nd poverty llevition in South Afri: opportunities, onstrints nd intervention options. Deprtment of Wter Affirs nd Forestry, Pretori Tshplinski TJ, Blke TJ (1995) Growth nd rohydrte sttus of oppie shoots of hyrid poplr following shoot pruning. Tree Physiol 15: Twine WC, Moshe D, Netshiluvhi T, Siphugu V (23) Consumption nd diret-use vlues of svnn io-resoures used y rurl households in Mmetj, semi-rid re of Limpopo provine, South Afri. S A J Si 99: Vn der Heyden F, Stok WD (1996) Regrowth of semirid shru following simulted rowsing: the role of reserve ron. Funt Eol 1: Wendler R, Crvlho PO, Pereir JS, Millrd P (1995) Role of nitrogen remoiliztion from old leves for new lef growth of Eulyptus gloulus seedlings. Tree Physiol 15: Wildy DT, Pte JS (22) Quntifying ove- nd elow-ground growth responses of Western Austrlin Oil Mllee, Eulyptus kohii sus. plenissim, to ontrsting depittion regimes. Ann Bot 9: