5 Les/Wood, Vol. 69, No. 2, December 2020 INTER-TREE VARIABILITY OF AUTUMN LEAF PHENOLOGY OF EUROPEAN BEECH (FAGUS SYLVATICA) ON A SITE IN LJUBLJANA, SLOVENIA VARIABILNOST JESENSKE LISTNE FENOLOGIJE MED DREVESI NAVADNE BUKVE (FAGUS SYLVATICA) NA RASTIŠČU V LJUBLJANI Nina Škrk 1* , Ang ela Balz ano 1 , Z alik a Čr epinšek 2 , K a t arina Č uf ar 1 UDK 630*181.8:630*176.1 Fagus sylvatica Original scien tific article / Iz virni znans tv eni članek R eceiv ed / Prispelo : 23. 11. 2020 Accep t ed / Spr eje t o: 2. 12. 2020 V ol. 69, No. 2, 5-20 DOI: h ttp s://doi.or g /10.26614/les-w ood.2020. v69n02a09 Abstract / Izvleček Abstract: Temporal variability of leaf senescence (autumn phenology) was observed in 2020 in 11 European beech (F agus s ylv a tic a) trees in Tivoli, Rožnik and Šišenski hrib Landscape Park in Ljubljana, Slovenia, and also observed for spring phenology in the same year. General leaf colouring, BBCH94, occurred between 19 and 24 October 2020, with lower inter-individual variability than that of leaf unfolding, BBCH11. The trees had active leaves (time between leaf unfolding and leaf colouring) between 177 and 199 days. In only three trees total leaf fall, BBCH97, occurred before 19 November 2020. Leaf colouring of the tree included in the long-term monitoring program of the Slovenian Environment Agency ARSO occurred on 24 October 2020. This is 7 days later than the 65-year average of the same tree/location and is ascribed to weather conditions. Investigation of tree tissues showed that the width of the last formed tree-ring in the wood varied between 0.39 and 9.61 mm and in the phloem between 0.09 and 0.26 mm, and that the tissues reflect the health condition of the trees. Keywords: leaf phenology, autumn, leaf colouring, leaf fall, wood formation, inter-individual variability, European beech (F agus s ylv a tic a), Slovenia Izvleček: V letu 2020 smo spremljali jesensko fenologijo listov 11 dreves navadne bukve (F agus s ylv a tic a) v Krajinskem parku Tivoli, Rožnik in Šišenski hrib v Ljubljani, Slovenija. Na teh drevesih smo spomladi 2020 spremljali proces olistanja. Splošno obarvanje listov, BBCH94, je nastopilo med 19. in 24. oktobrom 2020, v ožjem časovnem intervalu kot spomladansko olistanje, BBCH11. Drevesa so imela aktivne liste (čas med olistanjem in obarvanjem listov) od 177 do 199 dni. Samo s treh dreves je do 19. novembra 2020 odpadlo vse listje, BBCH97. Pri drevesu, ki je vključeno v dolgoletni program spremljanja fenologije listov Agencije Republike Slovenije za okolje ARSO, je obarvanje listov nastopilo 24. oktobra 2020, kar je za 7 dni kasneje od 65-letnega povprečja za isto drevo / lokacijo. Raziskave drevesnih tkiv so pokazale, da je znašala širina zadnje branike v lesu med 0,39 in 9,61 mm in v floemu med 0,09 in 0,26 mm in da tkiva nakazujejo zdravstveno stanje dreves. Ključne besede: fenologija, jesen, obarvanje listov, odpad listov, nastajanje lesa, variabilnost med osebki, bukev (F agus s ylv a tic a), Slovenija 1 INTRODUCTION 1 UVOD The main lea f phenology e v en ts in t emper a t e tr ees li k e Eur opean beech (Fagus sylvatica) ar e oft en divided in t o spring and autumn phenology . Spring phenology has g ener ally been s tudied mor e fr equen tly than autumn phenology (Gallina t e t al., 2015), which c o v er s the pr ocesses r ela t ed 1 Univ erz a v Lju bljani, Biot ehniš k a f ak ult e t a, Oddelek z a lesar s tv o , Jamnik arje v a 101, 1000 Ljubljana, SL O * e-mail: nina.skrk@b f .uni-lj.si 2 Univ erz a v Lju bljani, Biot ehniš k a f ak ult e t a, Oddelek z a agr onomijo , Jamnik arje v a 101, 1000 Ljubljana, SL O t o lea f senescence, includin g lea f c olouring and lea f f all be f or e the tr ee en t er s win t er dormancy (Žus t, 2015). Phenology is g ener ally driv en b y clima t e (Doi & T ak ahashi, 2008), but ther e e xis t species-specific r esponses t o clima t e (Ibáñe z e t al., 2010). Higher summer t emper a tur es g ener ally dela y the occurr ence of lea f senescence in beech in autu mn (Ču f ar e t al., 2012), and some models pr edict dela y ed lea f c olouring f or beech of 1.4 and 1.7 da y s per dec ade due t o pr ogr essing clima tic chang e (Delpi err e e t al., 2009). On the other hand, lea f senescence ma y be adv anced due t o summer dr ou gh t, e x tr emel y high t emper a tur es which damag e the lea v es, lo w t emper a tur es and 6 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: V ariabilnos t jesensk e lis tne f enologije med dr e v esi na v adne bukv e (Fagus sylvatica) na r as tišču v Ljubljani in v er sions (Schus t er e t al., 2014). Foliar senesce nce which c an be visually ob ser v ed is acc ompanied b y cessa tion of xylem and phloem f orma tion b y the c ambium, which c an only be s tudie d under the micr osc ope a ft er tissue sampling and pr epar a tion (Ču f ar e t al., 2008; Prislan e t al., 2013a, 2013b). The c ombina tion of the tw o appr oaches is ther e f or e of gr ea t r esear ch in t er es t (Čuf ar e t al., 2008; Do x e t al., 2020). Ob ser v a tions of lea f phenol ogy of Eur opean beech ar e included in the Slo v enian Na tional Phenologic al Ne tw ork of the Slo v enian En vir onmen t Ag ency (AR SO) within the Minis tr y of En vir onmen t and Spa tial Planning c oor dina t ed b y the In t erna tion al Phenologic al Gar dens (IPG) (The in t erna tional …, 2020; Chmiele w ski e t al., 2013; Žus t, 2015). In autumn the y monit or the g ener al lea f c olouring and lea f f all (Žus t, 2015). A s tudy based on da t a on lea f phenology in beec h c olle ct ed b y AR SO fr om 47 loc alities in Slo v enia (altitudes 55 t o 1,050 m a.s.l.) in the period 1955-2007, sho w ed tha t g ener al lea f c olouring occurr ed be tw een 2 Oct ober and 29 Oct ober (da y of the y ear (DO Y) 275-302). It occurr ed earlier a t higher altitudes (1.9 da y s ear lier per 100 m altitude incr ease). Lea f c olouring w as f ound t o be positiv ely c orr ela t ed with t emper a tur es fr om Augus t t o Sep t ember , wher eas long-t erm tr ends and r ela tion t o altitude w er e not s t a tis tic ally signific an t (Čuf ar e t al., 2012). In addition t o the long-t erm ob ser v a tions of AR SO on r epr esen t a tiv e tr ees, w e need be tt er kno wledg e on the v ariability of phenologic al e v en ts in the same species (in t er -individual or be tw een tr ee v ariability) and in the same tr ee (in tr a-individual or within tr ee v ariability). A s tudy on deciduous tr ees in t emper a t e la titudes sho w ed tha t the in t er - individual v ariability of spring phenology depends on the species, tr ee siz e and autumn phenology of the pr e viou s y ear (Denéchèr e e t al., 2019). The same s tudy pr oposed a minim um sample siz e of 23 tr ees t o f ollo w lea f senescen ce, and sho w ed tha t the within-pop ula tion a v er ag e s t andar d de via tion w as nearly tw o times lar g er f or lea f senescence (8.5 da y s) than f or budbur s t (4.0 da y s). A r ecen t s tudy on the v ariability of spring phenology , i.e. lea f de v elopmen t, in Eur opean beech gr o wing on a sit e in Ljubljana-Tiv oli, Slo v enia, sho w ed tha t g ener al lea f un f olding in diff er en t tr ees on the same sit e occurr ed within an in t er v al of almos t thr ee w eek s (be tw een 7 and 25 April 2020) (Škrk e t al., 2020a). Mor eo v er , the occurr ence and dur a tion of mor e pr ecisely de fined phases of lea f de v elopmen t sho w ed lar g e v aria tions within and be tw een tr ees. Among the ob ser v ed tr ees w as also a s t and ar d bee ch tr ee (Fagus sylvatica Har degsen, plan t iden tific a tion number 221, plan ting y ear 1969, origin German y) inclu ded in the long-t erm monit oring pr ogr am of AR SO; its lea f un f olding w as ob ser v ed on 14 April 2020, which w as 4 da y s earlier than the long- t erm a v er ag e of the same tr ee/loc a tion (Škrk e t al., 2020a). E arly lea f de v elopmen t in 2020 w as ascribed t o the abo v e- a v er ag e t emper a tur es in win t er 2019/2020. As the beech tr ees in Ljubljana-Tiv oli ob ser v ed in spring 2020 pr o vided v aluable in f orma tion on in t er -tr ee v ariability on spring phenology , w e c on tinued their monit oring till la t e autumn of 2020. The aim of the pr esen t s tudy is t o pr esen t the pr ogr ession of lea f senescence, especially lea f c olouring and lea f f all, and t o r ela t e them t o clima t e da t a and long-t erm lea f c olouring da t a f or beech in Ljubl jana. In additi on, w e e v alua t ed the c ondition of tr ee tissues, las t f ormed w ood and phloem, sampled ar ound the da y of g ener al lea f c olouring and their possible use t o e v alua t e the gr o w th pot en tial and health c ondition of the tr ees. 2 MATERIALS AND METHODS 2 MATERIAL IN METODE 2.1 STUDY SITE AND TREES 2.1 OPAZOVANA PLOSKEV IN DREVESA The select ed s tudy ar ea w as Tiv oli, R o žnik and Šišenski hrib Landsc ape P ark in Ljubljana. The 11 tr ees select ed f or ob ser v a tion w er e ob ser v ed daily f or lea f phenology in spring of 2020 (Škrk e t al., 2020a, 2020b). W e ob ser v ed the tr ees on thr ee loc a tions : (1) tr ees 11-19 and (2) tr ee 20 – all on the pa th w a y P od T urnom, near the w a t er r eser v oir; and (3) tr ee 30 near the Cekin Mansion, which is included in the long-t erm monit oring of the Slo v enian Na tional Phenologic al Ne tw ork (Fagus sylvatica Har degsen, plan t iden tific a tion number 221, plan ting y ear 1969, origin German y) of the Slo v enian En vir onmen t Ag ency as a part of the In t erna tion al Phenologic al Gar dens of Eur ope (Figur e 1). 7 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: In t er -tr ee v ariability of autumn lea f phenology of Eur opean beech (Fagus sylvatica) on a sit e in Ljubljana, Slov enia The g eogr aphic al c oor dina t es of tr ees and tr ee gr oup ar e be tw een 46.052697°- 46.058247° N, 14.489115° and 14.495366° E, and 307-316 m a.s.l. (Škrk e t al., 2020a). 2.2 FIELD OBSERVATIONS OF LEAF PHENOLOGY 2.2 TERENSKA OPAZOVANJA RAZVOJA LISTOV F or monit oring phenologic al phases of lea f c olouring w e visit ed the select ed tr ees be tw een 10 Sept ember and the end of Nov ember 2020. Fir s t, w e obser v ed them once a w eek, but then with the onse t of lea f c olouring and its in t ense pr ogr ess w e obser v ed them 3 times a w eek. W e t ook digit al phot os of all select ed tr ees. W e r ec or ded g ener al lea f c olouring (y ellowing) (BBCH94), which occur s when mor e than half of the lea v es turn y ellow in autumn (T able 1) (Žus t, 2015). In addition, w e also t ook not es on lea f f all, BBCH97, when 100% of lea v es f ell down fr om tr ees t o the gr ound (K och e t al., 2009; Žus t, 2015) if it occurr ed till 19 Nov ember 2020. F or a be tt er o v er vie w of lea f c olouring and lea f f all w e also t oo k panor amic phot os of the ob ser v ed sit e. Th e phot os w er e t ak en fr om the Nebotičnik sky scr aper and fr om the Ljubljana Cas tle hill. 2.3 CLIMATIC AND PHENOLOGICAL DATA FOR COMPARISON 2.3 KLIMATSKI IN FENOLOŠKI PODATKI ZA PRIMERJAVO T o illus tr a t e the w ea ther c onditions during the obser v ed lea f c olouring w e used the daily me t eor ologic al da t a, minimum and ma ximum t emper a tur es and sums of pr ecipit a tion f or Ljubljana f or the period Ma y -Nov 2020 and c ompar ed them t o the long-t erm a v er ag e f or Figure 1. Study trees on 10 September 2020 before the onset of autumn leaf colouring. Trees 11-20 belong to a beech forest site, while tree 30 grows in the park and is a clone (F agus s ylv a tic a Hardegsen) included in the International Phenological Gardens for long-term observations of leaf phenology conducted by ARSO. Slika 1. Preučevana drevesa 10. septembra 2020 pred nastopom jesenskega obarvanja listov. Drevesa 11–20 pripadajo območju bukovega gozda, medtem ko drevo 30 raste v parku in je klon (F agus s ylv a tic a Hardegsen), vključen v Mednarodni fenološki vrt za dolgoročno opazovanje fenologije listov, ki ga opravlja ARSO. Phase / Faza Name / Ime Description Opis faze BBCH94 Ge ner al lea f c olouring (y e llo wing) / Splošno obar v anje (rumene nje ) lis t o v Mor e than 50% of the lea v es turn y e llo w V e č k ot polo vic a lis t o v je sensk o obar v anih BBCH97 Ge ner al lea f f all / Splošno odpadanje lis t o v 100% of lea v e s f e ll do wn fr om tr ee s t o the gr ound 100 % lis t o v odpade z dr e v e s Table 1. Description of autumn phenological phases Preglednica 1. Opis jesenskih faz listne fenologije 8 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: V ariabilnos t jesensk e lis tne f enologije med dr e v esi na v adne bukv e (Fagus sylvatica) na r as tišču v Ljubljani 1981-2010. Clima tic da t a w er e obt ained fr om the online me t eor ologic al ar chiv e AR SO METE O (AR SO , 2020). The ob ser v ed lea f c olourin g w as c ompar ed with lo ng-t erm phenologic al da t a of g ener al lea f c olouring f or Ljubljana f or the period 1955-2019 fr om the da t abase of the Slo v enian Na tional Phenologic al Ne tw ork of AR SO (Žus t, 2015). 2.4 MICROCORE SAMPLING AND INCREMENT OF WOOD AND PHLOEM 2.4 ODVZEM MIKRO IZVRTKOV IN PRIRASTEK LESA IN FLOEMA As tr ee siz e and vit ality migh t a ff ect lea f phenology , w e also measur ed the diame t er s a t br eas t heigh t (1.3 m) f or 7 char act eris tic tr ees (number s 11, 12, 13, 14, 19, 20, 30). As tr ees gr o w in an import an t r ecr ea tion ar ea r epr esen ting the “ gr een lungs” of Ljubljana, the y c annot be c or ed t o de t e rmine their ag es. Ther e f or e, w e es tima t ed the ag e based on nearb y f elled tr ees. T o es tima t e the curr en t gr o w th with min imal tr ee w ounding , w e t ook micr oc or es fr om the 6 select ed tr ees. The micr oc or es w er e t ak en fr om the s t ems on 13 Oct ober 2020 with a T r ephor t ool a t 1.3 m abo v e gr ound. The micr oc or e s w er e pr ocessed in agr eemen t with the me thod olo gy of sample c oll ection and tissue pr epar a tion pr ot oc ol of Prislan e t al. (2013a, 2014). The 9 µm thick tr ans v er se sections s t ained with sa fr anin and as tr a blue w er e ob ser v ed with a Nik on eclip se 800 ligh t micr osc ope, and analy sed with NIS Elemen ts imag e analy sis pr ogr am. W e inspect ed the c ondition (s t a t e of diff er en tia tion, cell char act e ris tics) and measur ed the dim ensions (width and cell number) of the tissues including c ambium, las t f ormed xylem and phloem incr em en ts of 2020 along the thr ee r adial files (Prislan e t al., 2013a). Figure 2. Variability of leaf colouring (a) among trees and within the same tree, and (b) within the same branch on 31 October 2020 (DOY 305). Slika 2. Razlike v obarvanju listov (a) med drevesi in znotraj istega drevesa ter (b) znotraj iste veje 31. oktobra 2020 (dan 305). 9 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: In t er -tr ee v ariability of autumn lea f phenology of Eur opean beech (Fagus sylvatica) on a sit e in Ljubljana, Slov enia 3 RESULTS AND DISCUSSION 3 REZULTATI IN RAZPRAVA 3.1 DYNAMICS OF AUTUMN LEAF COLOURING IN 2020 3.1 DINAMIKA JESENSKEGA OBARVANJA LISTOV V LETU 2020 On 10 Sep t em ber 2020 the ob ser v ed tr ees had some y ello w lea v es, but the majority w er e gr een (Figur e 1). Aft er tha t da t e w e r ec or ded the gr adual onse t of lea f c olouring , which v aried within the same tr ee and be tw een the tr ees (Figur e 2). Lea f c olouring oft en fir s t occurr ed near the t op of a tr ee and pr ogr essed t o w ar ds the lo w er parts of the cr o wn. While the t op w as alr eady y ello w or the lea v es alr eady s t art ed t o f all, the lea v es a t the bott om of the tr ee c ould s till be gr een. Ther e w er e also gr e a t diff e r ences in pr ogr ess of lea f c olouring within the same br anches. Lea f c olouring w as slowly pr ogr essing fr om the end of Sept ember till mid-Oct ober , and bec ame f as t er especially a ft er 20 Oct ober , when mos t tr ees chang ed lea f c olour within a f e w da y s (Figur es 3, 4, 5). Gener al lea f c olouring , when mor e than 50% of lea v e s turned y ello w , as de fined b y IPG (T able 1), w as fir s t ob ser v ed in tr ees 12 and 14 (DO Y 293), tw o da y s la t er in tr ee 11 (DO Y 295), f ollo w ed b y tr ee 19 (DO Y 296). In tr ees 20 and 13 g ener al lea f c olouring w as ob ser v ed on 23 Oct ober (DO Y 297) (Figur es 4, 5, 6, T able 2). The phot os also sho w the dynamics of lea f f all. In t er es tingly , tr ee 14, which had the la t es t lea f un f olding in sprin g , w as the fir s t tr ee which los t all its lea v es b y the end of Oct ober . B y 19 No v ember , tr ees 11 and 12 also los t all their lea v es. T r ee 19 did not v ar y fr om other tr ees r eg ar ding timing of lea f c olouring , while in spring this tr ee had a v er y la t e lea f un f oldin g (Figur e 6, T able 2). T r ee 19 gr o w s solit ar y a ft er the nearb y tr ees w er e damag ed b y an ice s t orm in F ebruar y 2014, and has been r eport ed t o sho w a decline char act eriz ed b y dea th of shoo ts, twigs, br anches and tr anslucen t and spar se c anop y (Ogris, 2020). Compar ed t o the spring dynamics of lea f un f olding , when the diff er ence be tw een the earlies t and la t es t tr ee w as 18 da y s, the timing of g ener al lea f c ol ouring w as less v ariable; with a diff er ence be tw een the earlies t and the la t es t lea f c olouring of 5 da y s (T able 2). Lea f f all phase (BBCH97), when 100% of lea v es f all fr om tr ees t o the gr ound, mainly depends on Figure 3. Study site and trees in Tivoli, Rožnik forest as seen (a) from the Ljubljana Skyscraper (Nebotičnik) on 24 September (DOY 268) and (b) from the Ljubljana Castle on 30 October 2020 (DOY 304). Slika 3. Opazovano območje in drevesa na območju krajinskega parka Tivoli, Rožnik, fotografirana (a) z ljubljanskega Nebotičnika 24. septembra (dan 268) in (b) z Ljubljanskega gradu 30. oktobra 2020 (dan 304). 10 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: V ariabilnos t jesensk e lis tne f enologije med dr e v esi na v adne bukv e (Fagus sylvatica) na r as tišču v Ljubljani Figure 4. Phenology of leaf senescence in the observed beech trees between 18 September (DOY 262) and 25 October 2020 (DOY 299). Slika 4. Fenologija senescence listov opazovanih bukev med 18. septembrom (dan 262) in 25. oktobrom 2020 (dan 299). 11 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: In t er -tr ee v ariability of autumn lea f phenology of Eur opean beech (Fagus sylvatica) on a sit e in Ljubljana, Slov enia Figure 5. Phenology of leaf senescence in the observed beech trees between 28 October 2020 (DOY 302) and 22 November 2020 (DOY 327). Slika 5. Fenologija senescence listov opazovanih bukev med 28. oktobrom (dan 302) in 22. novembrom 2020 (dan 327). 12 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: V ariabilnos t jesensk e lis tne f enologije med dr e v esi na v adne bukv e (Fagus sylvatica) na r as tišču v Ljubljani curr en t c onditions (wind, r ain e t c). Gr adual lea f f all s t art ed soon a ft er lea f c olouring , with the e x cep tion of tr ee 30. T ot al lea f f all w as b y 19 No v ember 2020 only ob ser v ed in 3 tr ees, while on the other tr ees Figure 6. Tree 19 – detailed views of the crown with progressing leaf senescence from September till November 2020. Slika 6. Drevo 19 - podroben pogled na krošnjo in napredovanje senescence listov od septembra do novembra 2020. the lea v es wilt ed a ft er 21 No v ember when the t emper a tur e f ell belo w z er o f or the fir s t time. Aft er tha t time, and especially on tr ees 20 and 30, some of the lea v es r emained a tt ached t o the twigs. 13 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: In t er -tr ee v ariability of autumn lea f phenology of Eur opean beech (Fagus sylvatica) on a sit e in Ljubljana, Slov enia of the Slo v enian Na tional Phenologic al Ne tw ork included in the IPG (plan t nu mber 221), and is one of a series of g ene tic ally iden tic al tr ees tha t ar e plan t ed all o v er Eur ope (The in t erna tional …, 2020). Lea f c olouring in Ljubljana has v aried o v er time. The long-t erm (1955-2 019) a v er ag e da y of lea f c olouring is 18 Oct ober (DO Y 291, when not a leap y ear as in 2020). The earlies t lea f c olouring in this tr ee w as ob ser v ed on DO Y 270 (27 Sep t ember 1979), and the la t es t on DO Y 307 (3 No v ember 1991 and 1997) (Figur e 8). In 2020 lea f c olouring of tr ee 30 w as ob ser v ed on DO Y 298 (24 Oct ober 2020), which is 7 da y s la t er than the long-t erm a v er ag e. In Ljubljana ther e is a g ener al tr end t o w ar ds la t er lea f c olou ring , but Čuf ar e t al. (2012) sho w ed tha t the tr end w as not s t a tis tic ally signific an t in the period 1955-2007. Table 2. Dates of general leaf colouring compared to dates of leaf unfolding, days with active leaves (days between leaf unfolding and leaf colouring) and a note if the leaf fall occurred by 19 November 2020. Preglednica 2. Datumi splošnega obarvanja listov pri izbranih drevesih, datumi razvoja listov, dnevi z aktivnimi listi (dnevi med olistanjem in obarvanjem listov) in zaznamek, če je bil odpad listov zaključen do 19. novembra 2020. 3.2 LEAF COLOURING IN THE LIGHT OF LONG-TERM OBSERVATIONS 3.2 OBARVANJE LISTOV V LUČI DOLGOLETNIH OPAZOVANJ In tr ee 30 (inclu ded in the long -t erm phenology monit oring of AR SO) g ener al lea f c olouring occurr ed a t the la t es t da t e, on 24 Oct ober , DO Y 298 (Figur e 7, T able 2). On 22 No v ember (DO Y 327) the tr ee s til l had numer ous br o wn wilt ed lea v es in the upper part of the cr o wn (Figur e 5). This agr ees with the ob ser v a tion of numer ous wilt ed lea v es in the upper cr o wn ob ser v ed in spri ng of 2020. The wilt ed lea v es of the pr e vious y ear r emained on the tr ee till the un f oldin g of ne w lea v e s in spring (Škrk e t al., 2020a, 2020b). As men tioned be f or e, tr ee 30 is a r e f er ence tr ee f or Ljubl jana monit or ed in the fr ame w ork Tree / Drevo Leaf unfolding / Razvoj listov Leaf colouring / Obarvanje listov Days with active leaves / Dnevi z aktivnimi listi Leaf fall till 19 Nov 2020 / Odpad listov do 19.11.2020 Date / Datum DOY / Dan v letu Date / Datum DOY / Dan v letu Days / Dnevi 11 9.4.2020 100 21.10.2020 295 195 y es / da 12 9.4.2020 100 19.10.2020 293 193 y es / da 13 16.4.2020 107 23.10.2020 297 190 14 25.4.2020 116 19.10.2020 293 177 y es / da 19 22.4.2020 113 22.10.2020 296 183 20 7.4.2020 98 23.10.2020 297 199 30 14.4.2020 105 24.10.2020 298 193 A v e r ag e / P o vpr . 106 296 190 Minimum / Min. 98 293 177 Ma ximum / Mak s. 116 298 199 ST D 6.90 1.99 7.55 14 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: V ariabilnos t jesensk e lis tne f enologije med dr e v esi na v adne bukv e (Fagus sylvatica) na r as tišču v Ljubljani Figure 7. Progression of leaf colouring in tree 30 between 18 September (DOY 262) and 22 November (DOY 327) with detailed view of crown top. General leaf colouring occurred on 24 October 2020 (DOY 298). The tree (F agus s ylv a tic a Hardegsen, plant identification number 221, planting year 1969, origin Germany) is included in the long-term monitoring of the Slovenian National Phenological Network of the Slovenian Environment Agency (ARSO). Slika 7. Napredovanje obarvanja listov na drevesu 30 med 18. septembrom (dan 262) in 13. novembrom (dan 318) s podrobnim pogledom vrha krošnje. Splošno obarvanje listov se je zgodilo 24. oktobra 2020 (dan 298). Drevo (F agus s ylv a tic a Hardegsen, identifikacijska številka rastline 221, leto sajenja 1969, poreklo Nemčija) je vključeno v dolgoročno spremljanje fenologije v okviru Slovenske nacionalne fenološke mreže Agencije RS za okolje (ARSO). Figure 8. General leaf colouring of beech 30 in Ljubljana (plant 221, IPG) in the period 1955-2020 and the corresponding average (dotted line). DOY - day of the year. Data ARSO (2020). Slika 8. Dan obarvanja listov bukve 30 v Ljubljani (drevo 221, IPG) v obdobju 1955-2020 in pripadajoče povprečje (črtkana črta). DOY – zaporedni dan v letu. Podatki ARSO (2020). 15 Les/Wood, Vol. 69, No. 2, December 2020 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: In t er -tr ee v ariability of autumn lea f phenology of Eur opean beech (Fagus sylvatica) on a sit e in Ljubljana, Slov enia 3.3 WEATHER CONDITIONS AND THEIR IMPACT ON LEAF SENESCENCE 3.3 VREMENSKE RAZMERE IN NJIHOV VPLIV NA SENESCENCO LISTOV Summer 2020 in Slo v enia w as w armer (+0.9°C) and w e tt er (119% pr ecipit a tion) than the long-t erm a v er ag e 1981-2010. The surplus in t emper a tur e w as r ela tiv ely small in June and July , wher eas Augus t w as sign ific an tly w arm er than the long-t erm a v er ag e. Ne v ertheless, summer 2020 g ener ally had a lo w er t empe r a tur e than other summer s in the las t 5 y ear s. In Ljubljana the ma ximum summer t emper a tur e in 2020 w as 33.2°C , with 25 da y s with a ma ximum daily t emper a tur e of a t leas t 30°C (Fi gur e 9). The sum of pr ecipit a tion e x ceeded the lon g-t erm a v er ag e on mos t summer da y s in Ljubljana (Cegnar , 2020). Sept ember 2020 w as also w armer (+1.5°C) than the long-t erm a v er ag e in Ljubljana, but had only 90% of the long-t erm pr ecipit a tion. The las t 5 da y s of Sept ember w er e c ooler . The a v er ag e t emper a tur e in Oct ober w as 11.9°C, which is 0.6°C w armer than usual. The amoun t of pr ecipit a tion w as 138% c ompar ed t o the long-t erm a v er ag e. Ther e w as a sligh t c ool-w e t period a ft er 10 Oct ober 2020. Acc or ding t o the w ea ther c onditions in summer and autumn 2020, it w as less lik ely tha t summer t emper a tur es w ould damag e the lea v es and c ause pr ema tur e lea f c olouring. Ther e f or e, w arm and moder a t ely w e t c onditions in summer and autumn 2020 mos t lik ely f a v our ed la t er occurr ence of lea f c olouring and lea f f all. 3.4 CAMBIUM, WOOD AND PHLOEM AT THE TIME OF LEAF COLOURING 3.4 KAMBIJ, LES IN FLOEM V ČASU OBARVANJA LISTOV In v es tig a tion of tr ee tissues c ollect ed fr om the tr ees b y micr o-c oring in mid -Oct ober (ar ound the long-t erm a v e r ag e da y of lea f c olouring) sho w ed tha t w ood f orma tion w as c omple t ed in all tr ees, e x cep t in one (tr ee 30). Th e width of the las t f ormed tr ee ring 2020 in the w ood v aried be tw een 0.39 and 9.61 mm and in the phloem be tw een 0.09 and 0.26 mm (T able 3). The tr ees in g ener al had v er y narr o w la t e phloem with mainly 1-2 cells per r adial r o w . Figure 9. Minimum and maximum daily temperatures (T) and precipitation (P) in Ljubljana between May and November 2020 and average minimum and maximum temperatures for the period 1981-2010 (data ARSO, 2020). Slika 9. Minimalne in maksimalne dnevne temperature (T) ter padavine (P) v Ljubljani od maja do novembra 2020 in povprečne minimalne ter maksimalne temperature za obdobje 1981-2010 (podatki ARSO, 2020). 16 Les/Wood, Vol. 69, No. 2, December 2020 The ob ser v ed tr ees ar e char act eriz ed b y lar g e diame t er s and heigh ts (T able 3). The char act eris tics of tr ees 11-20 gr o wing on the loc a tion of na tur al beech f or es t de via t e fr om tho se of tr ee 30, which is a clone gr o wing in the phenologic al g ar den. T r ees 11-20 ha v e an es tima t ed ag e c a. 120- 150 y ear s based on tr ee-ring c oun t of the nearb y f elled tr ees. Th eir cr oss-sections sho w ed tha t the c ambium alr eady s t opped the pr oduction of w ood and ph loem, and tha t the w ood diff er en tia ting w as c omple t ed (with the e x cep tion of tr ee 30). The wid th of the las t f ormed xylem tr ee-ring 2020 (TR2020) v aried be tw een 0.39 and 2.34. T r ee 14 had the narr o w es t tr ee-rings especially a ft er 1993 (a v er ag e 0.38 mm f or 1994 -2020). T r ee 14 w as also the la t es t in spring phenology , the fir s t in lea f c olouring and the fir s t which los t all lea v es, in line with the findings of Fu e t al. (2014). T w o tr ees (13 and 19) sho w ed a pr onounced r eduction of tr ee- ring width in 2020, which migh t be r ela t ed t o tr ee decline r eport ed f or beech in Tiv oli (Ogris, 2020). T r ees 11-20 ha v e gr owth rings 2020 in the phloem be tw een 90 and 185 µm wide, with 3-5 early phloem (E) and 1-2 la t e phloem (L) cells. LP is g ener ally narr ow er than in tr ees a t P anšk a r ek a with similar clima tic c onditions (Prislan e t al., 2013a). The char act eris tics of tr ee 30 de via t ed fr om the ones of the other tr ees (T able 3). This is possibly Figure 10. Cross-sections of microcores showing: (a) wood, cambium and bark, and (b) detailed view of the tree 19 with last formed xylem tree-ring 2020 (TR2020), cambium (CC), non-collapsed phloem (NPh), divided in early (E) and late phloem (L), and part of the bark with collapsed phloem (CPh). Slika 10. Prečni prerezi mikro-izvrtkov, ki prikazujejo: (a) les, kambij in del skorje in (b) podroben pregled tkiv drevesa 19 vključno z zadnjo ksilemsko braniko 2020 (TR2020), kambijem (CC), nekolabiranim floemom (NPh), razdeljenim na rani (E) in kasni floem (L) ter delom kolabiranega floema (CPh). Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: V ariabilnos t jesensk e lis tne f enologije med dr e v esi na v adne bukv e (Fagus sylvatica) na r as tišču v Ljubljani 17 Les/Wood, Vol. 69, No. 2, December 2020 Table 3. European beech (F agus s ylv a tic a), Ljubljana: tree diameter at breast height (DBH), 2020 xylem and phloem ring width, and number of cells in early and late phloem on DOY 287 (13 October, 2020). Preglednica 3. Navadna bukev (F agus s ylv a tic a), Ljubljana: premeri dreves na prsni višini (DBH), širine ksilemske in floemske branike, nastale v letu 2020, ter število celic v ranem in kasnem floemu na dan 287 (13. oktober 2020). Tree / Drevo DBH / Premer Xylem ring width 2020 / Širina ksilemske branike 2020 Phloem ring width 2020 / Širina floemske branike 2020 Early phloem / Rani floem Late phloem / Kasni floem [cm] [mm] [µm] Number of cells / Število celic 11 68 1.73 175 5 2 12 64 1.07 169 4 1 13 59 0.39 90 3 1 14 66 0.48 185 6 1 19 58 0.40 182 4 1 20 70 2.34 147 5 2 30 53 9.61 256 3 4 A v er ag e / P o vpr . 62 2.29 172 4 2 Minimum / Min. 53 0.39 90 3 1 Ma ximum / Mak s. 70 9.61 256 6 4 ST D 6.27 3.31 49.48 1.11 1.11 bec ause tr ee 30 is a clone, gr o w s in the park (c a. 600 m apart fr om the other ob ser v ed beech tr ees), had the smalles t diame t er , heigh t and possibly ag e (c a. 50-60 y ear s), the lar g es t xylem (9.61 mm) and phloem ring (256 µm) f ormed in 2020, and the wides t la t e ph loem (4 cells) . It w as the only tr ee wher e diff er en tia tion of the las t f ormed xylem w as not y e t c ompl e t ed (Figur e 10). The tr ee also had the la t es t lea f c olouring (Fig ur es 1, 3, 7, 8, T ables 2, 3) and lea v es which w er e wilt ed a t the end of No v ember , but ma y r emain on the tr ee till the ne x t lea f un f olding (as ob ser v ed in spring of 2020). 4 CONCLUSIONS 4 ZAKLJUČKI W e pr esen t in t er -tr ee v ariability in the autumn leaf phenology of select ed beech tr ees in Ljubljana, which w er e also monit or ed in spring of the same y ear , 2020 (Škrk et al., 2020a). Although ther e w er e lar g e diff er ences in the dynamics of spring phenology with an 18-da y diff er ence f or leaf unf olding phase, all select ed tr ees r eached leaf c olouring , phase BBCH94, within a 5-da y in t er v al betw een 19 and 24 Oct ober 2020. Although chang es w er e gr adual fr om mid-Sept ember , the y bec ame v ery r apid aft er 19 Oct ober , when a lar g e per cen t ag e of tr ee lea v es chang ed c olour within a f ew da y s. W e also obser v ed a high in tr a- individual v ariability . T r ees 12 and 14, which gr ow in the immedia t e vicinity , w er e the fir s t t o ha v e 50% of all lea v es c olour ed (DO Y 293). The las t leaf c olouring w as obser v ed in tr ee 30, which is a clone and is included in the In t erna tional Phenologic al Gar dens. In tr ee 30, leaf c olouring occurr ed 7 da y s la t er c ompar ed t o the long t erm a v er ag e (DO Y 298). Lea f senescence is mos tly a ff ect ed b y summer t emper a tur es and b y ma ximum t emper a tur es fr om Sep t ember t o Oct ober . Acc or ding t o AR SO , t emper a tur es in Ljubljana ar e g ener ally incr easing , which r esults in a g ener al dela y in lea f senescence in autu mn. On the ob ser v ed sit e the summer w as v er y w arm with an abo v e a v er ag e amoun t of pr ecipit a tion. Oct ober 2020 in particular w as w armer than long t erm a v er ag e, and it also had 38% mor e pr ec ipit a tion, whic h migh t f a v our a dela y in lea f c olouring. Since t emper a tur es ma y be a dominan t f act or , w e c an e xpect, in the c on t e x t of global w arming , dela y ed da t es of lea f senescence in ar eas without w a t er limit a tion, such as Ljubljana. Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: In t er -tr ee v ariability of autumn lea f phenology of Eur opean beech (Fagus sylvatica) on a sit e in Ljubljana, Slov enia 18 Les/Wood, Vol. 69, No. 2, December 2020 5 SUMMARY 5 POVZETEK Jesensk a f enologija lis t opadnih dr e v es, k ot je na v adna buk e v (Fagus sylvatica), pr oučuje obar v anje in odpadanje lis t o v , pr eden dr e v o v s t opi v zimsk o mir o v anje (Žus t, 2015) in tudi f enološk e dog odk e, po v e z ane s pr enehanjem k ambije v e pr oduk cije lesa in floema (Čuf ar e t al., 2008; Prislan e t al., 2013a, 2013b). Opaz o v anje lis tne f enologije na v adne bukv e je vključeno v Slo v ensk o nacionalno f enološk o mr e ž o Ag encije R S z a ok olje (AR SO) pri Minis tr s tvu z a ok olje in pr os t or (Žus t, 2015). Pr edhodna š tudija f enologije lis t o v bukv e je na osno vi poda tk o v , ki jih je zbr al AR SO na 47 r as tiščih po Slo v eniji (n admor sk e višine od 55 do 1.050 m) v ob dob ju 195 5-2007, pok az ala, da obar v anje v eč k ot polo vice lis t o v pri bukvi v Slo v eniji nas t opi od 2. do 29. ok t obr a. Obar v anje se poja vi pr ej na višjih nadmor skih višinah in je po zitivno po v e z ano s t emper a tur ami od a v gus t a do sep t embr a (Čuf ar e t al., 2012). V K r ajinsk em park u Tiv oli, R o žnik in Šišenski hrib v Ljubljani smo spomladi 2020 opaz o v ali 11 izbr anih buk e v in pridobili in f ormacije o r azlik ah spomladansk eg a r az v oja lis t o v med dr e v esi. Namen t okr a tne š tudije pa je bil spr emlja ti pr oces senescence lis t o v , zlas ti obar v anja in odpada lis t o v t er jih po v e z a ti z vr emens kimi in dolg or očnimi f enološkimi poda tki. P oleg t eg a smo ocenili s t anje dr e v esnih tkiv , k ambija, lesa in floema sr edi ok t obr a. Z a spr emljanje obar v anja lis t o v smo izbr ana dr e v esa opaz o v ali od 10. sep t embr a do k onc a no v embr a 202 0. Ob v sak em opaz o v anju smo jih f ot ogr a fir ali in pripr a vili g alerije slik (slik a 1, 4, 5, 6, 7). Z abele žili smo splošno obar v anje (rumenenje) lis t o v (BBCH94), k o se oba r v a v eč k ot polo vic a lis t o v (p r eglednic a 1), in odp ad lis t o v , ki se z aključi s f az o BBCH97, k o je 100 % lis t o v odpadlo z dr e v esa (Žus t, 2015). Z a boljši pr egled obar v anja in odpada lis t o v smo po sneli tudi panor amsk e f ot ogr a fije opaz o v aneg a r as tišč a. F ot ogr a fije smo posneli z ljubljansk eg a N ebotičnik a in z Ljubljansk eg a gr adu (slik a 3). Z a pr ouče v anje vr emenskih r azmer smo upor abili dne vne poda tk e z a Ljubljano iz sple tneg a me t eor ološk eg a arhiv a AR SO METE O . Obar v anje lis t o v smo primerjali z dolg or očnimi f enološkimi poda tki z a Ljubljano z a obdobje 1955-2019 iz baz e poda tk o v Slo v ensk e naciona lne f enološk e mr e ž e AR SO (Žus t, 2015). Opr a vili smo tudi odv z em mikr o iz vrtk o v pri 7 dr e v esih, izmerili pr emer e dr e v es in ocenili njiho v o s t ar os t. Mikr o iz vrtk e iz debel dr e v es smo od v z eli 13. ok t obr a 202 0 z or odjem T r ephor , jih obd elali in pripr a vili v skladu s pr ot ok olom, ki g a je pr edlag al Prislan s sod ela v ci (2013a, 2014) t er prip r a vili pr ečne pr er e z e z a opaz o v anje pod mikr osk opom. Splošno obar v anje lis t o v , BBCH94, je nas t opilo med 19. in 24. ok t obr om 2020, v o žjem č aso vnem in t er v alu k ot spomladansk o olis t anje, BBCH11. Dr e v esa so imela ak tivne lis t e (dne vi med olis t anjem in sploš nim ob ar v anjem lis t o v) od 177 do 199 dni. Samo s 3 dr e v es je do 19. no v embr a odpadlo v se lis tje (slik e 2, 4, 5, 6, 7, 8, pr eglednic a 2). Pri os t alih dr e v esih je po pr vi zmrz ali 21. no v embr a 2020 v se lis tje uv elo , a je pr edv sem pri dr e v esih 20 in 30 os t alo na dr e v esih. Pri dr e v esu 30, ki je vključeno v dolg ole tni pr ogr am spr emljanja f enol ogije lis t o v Ag encije R epublik e Slo v enije z a ok olj e AR SO , je obar v anje lis t o v nas t opilo 24. ok t obr a 2020, k ar je z a 7 dni k asneje od 65-le tneg a po vpr ečja z a is t o dr e v o / lok acijo (slik a 7, pr eglednic a 2). Na dr e v esu je bilo 22. no v embr a (DO Y 327) v z g ornjem delu kr ošnje še v edno v elik o uv elih lis t o v . P ole tje 2020 v Slo v eniji je bi lo t oplejše (+ 0,9 °C) in bolj vlažno (119 % pada vin) k ot dolg ole tno po vpr ečje 1981-2010, a manj vr oče k ot pole tja v z adnjih 5 le tih. K oličina pada vin v Ljubljani je bila pole ti z a manj k ot ods t ot ek manjša od dolg ole tneg a po vpr ečja. T udi sep t ember je bil t oplejši (+1,5 °C) od dolg ole tneg a po vpr eč ja, v endar je imel le 90 % dolg ole tnih pada vin. P o vpr ečna ok t obr sk a t emper a tur a je bila 11,9 °C , k ar je z a 0,6 °C v eč k ot obič ajno. K oličina pada vin je bila v primerja vi z dolg or očnim obdobjem v ečja (138 %). Opisane vr emensk e r azmer e so najv erje tneje vpliv ale na po znejše obar v anje in odpad lis t o v . Dr e v esa 11-20, ki r as t ejo ob v zno žju hriba na območju nek daj nar a vneg a buk o v eg a g o z da, so s t ar a približno 120-150 le t. Mikr osk op sk a analiz a tkiv je pok az ala, da je bila k ambije v a pr oiz v odnja t er s t em dif er e nciacija lesa in floema sr edi ok t obr a ž e z aključena (z izjemo dr e v esa 30). Širina z adnje br anik e v lesu , nas t ale v le tu 2020, je bila pri dr e v esih od 0, 39 do 2,34 mm. Dr e v o 14 je imelo najo žje br anik e in se je spo mladi olis t alo z adnje, Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: V ariabilnos t jesensk e lis tne f enologije med dr e v esi na v adne bukv e (Fagus sylvatica) na r as tišču v Ljubljani 19 Les/Wood, Vol. 69, No. 2, December 2020 jeseni pa se je pr v o obar v alo in odvr glo lis t e. Dr e v esi 13 in 19 s t a imeli v le tu 2020 manjši prir as t ek k ot v pr edhodnih le tih, k ar je mor da po v e z ano s hir anjem bukv e, ki so g a opazili tudi na območju Tiv olija (Ogris, 2020). Dr e v esa 11-20 so imela br anik e floema, nas t ale v le tu 2020, šir ok e od 90 do 185 µm, v r anem lesu smo z abele žili 3-5 celic, v k asnem pa 1-2 celici v r adialnih nizih. Dr e v o 30 se je v v seh pogledih r azlik o v alo od os t alih opaz o v anih dr e v es (pr eglednic a 3). T o je mor da z a t o , k er je dr e v o klon, ki r as t e v park o vnem delu Tiv olija. Ima najmanjši pr emer , višino in s t ar os t (približno 50–60 le t), najšir šo z adnjo k silemsk o (9,61 mm) in flo emsk o (256 µm) br anik o , t er najšir ši k asni floem (4 celice), dif er enciacija lesa z adnje br anik e pa sr edi ok t obr a še ni bila z aključena (slik a 10). Obar v anje lis t o v je pri t em dr e v esu nas t opilo najk asneje. S pr eds t a vljeno š tudijo smo orisali r azlik e v jesenski f enologiji med dr e v esi. SUPPLEMENT DODATEK The supplem en t r ela t ed t o this article is a v ailable online in the R eposit or y of the Univ er sity of Ljubljana (RUL) and c an be accessed thr ough h ttp s://r epo zit orij.uni-lj.si/IzpisGr adiv a. php?id=122429, and cit ed as Škrk e t al. (2020c). It c on t ains de t ailed phot os of lea f senescence in Eur op ean beech (Fagus sylvatica) (tr ee 30 in this s tudy) which is as a plan t nu mber 221 included in the long-t erm monit oring of the Slo v enian Na tional Phenologic al N e tw ork of the En vir onmen t al Ag ency of the R epublic of Slo v enia (AR SO) within the Minis tr y of the En vir onmen t and Spa tial Planning as a part of the In t erna tional Phenologic al Gar dens of Eur ope. Doda t ek, po v e z an s t em člank om, je pr os t o dos t open na sple tu v R epo zit oriju Univ erz e v Ljubljani (RUL). Dos t op do njeg a je mo ž en pr ek o po v e z a v e h ttp s://r epo zit orij.uni-lj.si/IzpisGr adiv a. php?id=122429 in se g a citir a k ot Škrk e t al. (2020c). Doda t ek v sebuje podr obne f ot ogr a fije senescence lis t o v pri na v adni bukvi Fagus sylvatica (dr e v o š t e vilk a 30 v t ej š tud iji), ki je k ot dr e v o z iden tifik acijsk o š t e vilk o 221 vključeno v dolg ole tno spr emljanje v okviru Sl o v ensk e nacionalne f enološk e mr e ž e Ag encije R epublik e Slo v enije z a ok ol je (AR SO) Minis tr s tv a z a ok olje in pr os t or R epublik e Slo v enije, ki je vključen v ak tivnos ti Mednar odnih f enoloških vrt o v E vr ope. ACKNOWLEDGEMENTS ZAHVALA The s tudy w as support ed b y the Slo v enian R esear ch Ag ency (pr ogr ams P4-0015 and P4- 0085 and y ou ng r esear cher s’ pr ogr am). Clima tic and lon g-t erm phenologic al da t a w er e pr o vided b y the Slo v enian En vir onm en t Ag ency (AR SO) within the Minis tr y of the En vir onmen t and Spa tial Planning. W e thank Ana Žus t f or her support with phenologic al da t a, as w ell as P aul St eed and Darja V r anjek f or English and Slo v ene languag e editing , r espectiv ely . Študijo je podprla Ja vna ag encija z a r azisk o v alno deja vnos t r epublik e Slo v enije ARR S (pr ogr ama P4- 0015 in P4-008 5 t er pr ogr am mladih r azisk o v alce v). Me t eor ološk e in dolg ole tne f enološk e poda tk e je posr edo v ala Ag encija R S z a ok olje (AR SO) pri Minis tr s tvu z a ok olje in pr os t or . Z ah v aljujemo se Ani Žus t z a v so pomoč t er P aulu St eedu in Darji V r anjek z a lek t orir anje anglešk eg a in slo v ensk eg a besedila. REFERENCES VIRI AR SO , arhiv me t eor oloških poda tk o v . (19. 11. 2020). R e trie v ed fr om h ttp s://me t e o.ar so. g o v .si/me t/ sl/ ar chiv e / Cegnar , T . (2020). P odnebne r azme r e v a v gus tu 2020 = Clima t e in Augus t 2020. N aše ok olje, 27 (8), 115. Chmiele w ski, F . -M., Heide r , S., Mor y son, S., & Bruns, E. (2013). In t e rna tional phe nologic al ob se r v a tion ne tw ork s - Conce p t of IP G and GPM. In M. D . Sch w artz (E d.), Phe nology: An In t e gr a tiv e En vir onme n t al Scie nce , 137-153. Čuf ar , K ., Prislan, P ., De Luis, M., & Grič ar , J . (2008). T r ee -ring v aria tion, w ood f orma tion and phe nology of be ech (Fagus sylvatica) fr om a r e pr e sen t a tiv e sit e in Slo v enia, SE Cen tr al Eur ope. T r ee s, 22 (6), 749-758. Čuf ar , K ., de Luis, M., Saz, M. A ., Čr e pinše k, Z., & K ajf e ž-Bog a t aj, L. (2012). T empor al shifts in le a f phe nology of be ech (Fagus sylvatica) de pend on ele v a tion. T r ee s, 26 (4), 1091-1100. Delpierr e, N., Dufr êne, E., Soudani, K., Ulrich, E., Cecchini, S., Boé, J ., & Fr anç ois, C. (2009). Modelling in t er annual and spa tial v ariability of lea f senescence f or thr ee deciduous tr ee species in Fr ance. Agricultur al and F or es t Me t eor ology , 149 (6-7), 938-948. Dené chè r e , R ., Delpie rr e, N ., Apos t ol, E. N ., Be r v eiller , D ., Bonne , F ., Cole, ... & Vincen t, G. (2019). The within-popula tion Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: In t er -tr ee v ariability of autumn lea f phenology of Eur opean beech (Fagus sylvatica) on a sit e in Ljubljana, Slov enia 20 Les/Wood, Vol. 69, No. 2, December 2020 v ariability of le a f spring and autumn phe nology is in fluenced b y t empe r a tur e in t empe r a t e de ciduous tr ee s. In t e rna tional Journal of Biome t e or ology , 1-11. Doi, H., & T ak ahashi, M. (2008). La titudinal pa tt erns in the phenologic al r esponses of lea f c olouring and lea f f all t o clima t e chang e in Japan. Global E c ology and Biog eogr aph y , 17 (4), 556-561. Do x, I., Grič ar , J ., Mar chand, L. J ., Le y s, S., Zucc arini, P ., Ge r on, C., Prislan, P ., ... & Campioli, M. (2020). Timeline of autumn phe nology in t empe r a t e de ciduous tr ee s. T r ee ph y siology , 40 (8), 1001-1013. Fu, Y . S. H., Campioli, M., Vit asse , Y ., De Boeck, H. J ., V an Den Be r g e , J ., AbdElg a w ad, H., ... & Jansse ns, I. A . (2014). V aria tion in le a f flushing da t e in fluences autumnal sene sce nce and ne x t y ear ’ s flushing da t e in tw o t empe r a t e tr ee species. Pr ocee dings of the N a tional Ac ade m y of Sciences, 111 (20), 7355-7360. Gallina t, A . S., Primack, R . B., & W agne r , D . L. (2015). Autumn, the ne glect e d season in clima t e chang e r e sear ch. T r ends in E c ology & E v olution, 30 (3), 169-176. Ibáñe z, I., Primack, R. B., Miller -Rushing , A . J ., Ellw ood, E., Higuchi, H., Lee, S. D ., K obori, H., & Silander , J . A . (2010). F or ec as ting phenology under global w arming. Philosophic al T r ansactions of the R oy al Socie ty B: Biologic al Sciences, 365 (1555), 3247-3260. K och, E., Bruns, E., Chmiele w ski, F . M., De fila, C., Lipa, W ., & Anne tt e, M. (2009). Guideline s f or Plan t Phe nologic al Ob ser v a tions W orld Clima t e Pr ogr amme. W orld Clima t e Da t a and Monit oring Pr ogr amme. Ogris, N . (2020). Hir anje na v adne bukv e po v se j Slo v eniji 2010-2019. N o vice iz v ar s tv a g o z do v , 13, 3-7. Prislan, P ., Grič ar , J ., de Luis, M., Smith, K . T ., & Čuf ar , K . (2013a). Phe nologic al v aria tion in xylem and phloem f orma tion in Fagus sylvatica fr om tw o c on tr as ting sit es. Agricultur al and f or e s t me t e or ology , 180, 142-151. Prislan, P ., Čuf ar , K ., K och, G., Schmitt, U ., & Gric ar , J . (2013b). R e vie w of ce llular and subcellular chang es in the c ambium. IA W A journal, 34 (4), 391-407. Prislan, P ., Grič ar , J ., & Čuf ar , K . (2014). W ood sample pr epar a tion f or micr osc opic analy sis. Univ e r sity of Ljubljana, Departmen t of W ood Science and T echnology . Schus t er , C., K ir chner , M., Jak obi, G., & Me nz el, A . (2014). Fr eque ncy of in v e r sions a ff ects sene sce nce phe nology of Acer pseudoplatanus and Fagus sylvatica. In t e rna tional Journal of Biome t eor ology , 58 (4), 485-498. Škrk, N ., Čr e pinše k, Z., & Čuf ar , K . (2020a). Phe nology of le a f de v e lopme n t in Eur opean be ech (Fagus sylvatica) on a sit e in Ljubljana, Slo v e nia in 2020. Les/W ood, 69 (1), 5-19. Škrk, N ., Čr e pinše k, Z., & Čuf ar , K . (2020b). Phe nology of le a f de v e lopme n t in Eur opean be ech (Fagus sylvatica) on a sit e in Ljubljana, Slo v enia in 2020 (da t a), [online] R e trie v ed fr om: h ttp s://r e po zit orij.uni-lj.si/IzpisGr adiv a. php?lang=slv&id=116807 Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K. (2020c). In t er -tr ee v ariability of autumn lea f phenology of Eur opean beech (Fagus sylvatica) on a sit e in Ljubljana, Slo v enia (da t a),[online] R e trie v ed fr om: h ttp s://r epo zit orij.uni-lj.si/IzpisGr adiv a.php?id=122429 The In t e rna tional Phe nologic al Gar dens of Eur ope. Humboldt Univ e r sity of Be rlin. (19. 11. 2020). R e trie v ed fr om h ttp: //ipg. hu-berlin.de Žus t, A . (2015). F enologija v Slo v eniji: Prir očnik z a f e nološk a opaz o v anja [Phenology in Slo v enia: Manual f or phe nologic al ob se r v a tions]. Minis tr y of En vir onmen t, Slo v enian En vir onmen t Ag ency , Ljubljana, Slo v e nia, 1-4. Škrk, N., Balz ano , A ., Čr epinšek, Z., & Čuf ar , K.: V ariabilnos t jesensk e lis tne f enologije med dr e v esi na v adne bukv e (Fagus sylvatica) na r as tišču v Ljubljani