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We present a technical note that supplements published procedures on optimal sample preparation for performing wood and phloem formation analyses. Before beginning sampling, it is important to learn about the characteristics of the tree or shrub species to be investigated. Some tips are given how to use the Trephor tool in the best way, how to remove the outer hard bark (periderm), how microcores should be handled after removal from the tree, and how they should be oriented for embedding in paraffin, and cutting thin sections for microscopy. Possible defects that may result from improper handling are illustrated and discussed. We also present optimal images to accurately identify different cell development stages in phloem and xylem, which is particularly challenging in hardwoods and Mediterranean tree and shrub species. Predstavljamo tehnična navodila, ki dopolnjujejo objavljene postopke za optimalno pripravo vzorcev za izvajanje analiz nastajanja lesa in floema. Pred začetkom vzorčenja je potrebno poznati značilnosti drevesne ali grmovne vrste, ki jo želimo preiskovati. Podanih je nekaj nasvetov, kako najbolje uporabiti orodje Trephor, kako odstraniti zunanjo trdo skorjo (periderm), kako ravnati z mikro izvrtki po odvzemu iz debla in kako jih orientirati za vklapljanje v parafin in rezanje tankih rezin za mikroskopske preiskave. Prikazane in razložene so možne napake, ki lahko nastanejo zaradi neustreznega ravnanja v različnih korakih postopka. Predstavljamo tudi optimalne slike tkiv za prepoznavanje različnih razvojnih faz celic v floemu in ksilemu, ki je še posebej zahtevno pri listavcih ter sredozemskih drevesnih in grmovnih vrstah.

Temporal variability of leaf senescence (autumn phenology) was observed in 2020 in 11 European beech (Fagus sylvatica) trees in Tivoli, Rožnik and Šišenski hrib Landscape Park in Ljubljana, Slovenia, previously this year observed also for spring phenology. General leaf colouring (LC) BBCH94 occurred, between 19 and 24 October 2020, with lower inter-individual variability than that of leaf unfolding (LU), BBCH11. The trees had active leaves (LC-LU) between 177 and 199 days. In only 3 trees total leaf fall (LF), BBCH97, occurred before 19 November 2020. LC 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 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 phloem between 0.09 and 0.26 mm and that the tissues reflect health condition of the trees. V letu 2020 smo spremljali jesensko fenologijo listov 11 dreves evropske bukve (Fagus sylvatica) v Krajinskem parku Tivoli, Rožnik in Šišenski hrib v Ljubljani, Slovenija. Pri istih drevesih smo spomladi spremljali proces olistanja. Splošno obarvanje listov (LC), BBCH94, je nastopilo med 19. in 24. oktobrom 2020, v ožjem časovnem intervalu kot spomladansko olistanje (LU), BBCH11. Drevesa so imela aktivne liste (LC-LU) od 177 do 199 dni. Samo s 3 dreves je do 19. novembra 2020 odpadlo vse listje (LF), 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.

Cessation of xylem formation or wood growth (CWG) and onset of foliar senescence (OFS) are key autumn phenological events in temperate deciduous trees. Their timing is fundamental for the development and survival of trees, ecosystem nutrient cycling and the seasonal exchange of matter and energy between the biosphere and atmosphere, and affects the impact and feedback of forests to global change. A large-scale experimental effort and improved observational methods have allowed us to compare the timing of CWG and OFS for different deciduous tree species in Western Europe, particularly in silver birch, a pioneer species, and European beech, a late-succession species, at stands of different latitudes, of different levels of site fertility, for 2 years with contrasting meteorological and drought conditions, i.e., the low moderately dry 2017 and the extremely dry 2018. Specifically, we tested whether foliar senescence started before, after or concurrently with CWG. Onset of foliar senescence and CWG occurred generally between late September and early November, with larger differences across species and sites for OFS. Foliar senescence started concurrently with CWG in most cases, except for the drier 2018 and, for beech, at the coldest site, where OFS occurred significantly later than CWG. The behavior of beech in Spain, the southern edge of its European distribution, was unclear, with no CWG, but very low wood growth at the time of OFS. Our study suggests that OFS is generally triggered by the same drivers of CWG or when wood growth decreases in late summer, indicating an overarching mechanism of sink limitation as a possible regulator of the timing of foliar senescence.

Po ţledolomu 2014 je v gozdovih ostalo veliko poškodovanih, a ţivih dreves. Ker znanja o dogajanju v poškodovanih drevesih primanjkuje, smo v Arboretumu Volčji Potok izvedli raziskavo na drevesih, ki so v ţledolomu utrpela poškodbo krošnje. Izbrali smo 14 bukev in 12 smrek, jih razvrstili v 4 razrede glede na stopnjo poškodovanosti krošnje (K % nepoškodovana, A % do 50 %, B % med 50 in 75 %, C % več kot 75 % poškodovana krošnja), v dvotedenskih intervalih na njih odvzemali mikroizvrtke z orodjem Trephor in opazovali spremembe v krošnjah. Iz mikroizvrtkov smo pripravili mikroskopske preparate lesa, kambija in skorje in jih analizirali s svetlobnim mikroskopom in sistemom za analizo slike. Poškodovanost krošnje ni vplivala na čas olistanja pri bukvi in pojav mladih poganjkov pri smreki. Bukve so revitalizirale svoje krošnje različno uspešno ne glede na stopnjo poškodbe krošnje. Smreke še niso revitalizirale svojih krošenj. Poškodovane bukve so proizvedle od 20 do 95 %, poškodovane smreke pa 35 % oţje ksilemske branike kot nepoškodovane. Manjši je bil tudi prirastek floema. Produkcija lesa se je v poškodovanih bukvah začela in zaključila prej kot v nepoškodovanih, na drugi strani se je v poškodovanih smrekah začela kasneje in zaključila prej kot v nepoškodovanih. Izmed štirih razredov poškodovanosti so se pri bukvi največje razlike v kambijevi aktivnosti pokazale med razredoma A in B, pri smreki pa med razredoma K in A. After the severe ice storm of 2014 a high number of damaged trees were not removed from forests. Due to lack of general knowledge about processes occurring in damaged trees, a study involving 14 European beech and 12 Norway spruce trees was conducted in Arboretum Volčji Potok. Trees were categorized by crown injury injury class K % undamaged, A % damaged less than 50 %, B % damaged between 50 and 75 % or C % damaged more than 75 %. During the 2014 growth season microcores were collected every fortnight using a Trephor tool. Changes in crowns were also observed and noted. Transverse sections of microcores were prepared and observed using light microscopy and a picture analysis system. Crown injury had no effect on leaf unfolding date in beech and young sprouts occurrence in spruce. Success of crown restoration in beech differed from tree to tree regardless of severity of crown injury. No crown restoration was seen in spruce. On average, xylem rings were 20 to 95 % narrower in damaged beech trees and 35 % narrower in damaged spruce trees compared to the undamaged trees. Damaged trees also produced narrower phloem rings. In damaged beech trees xylogenesis started and finished sooner than in undamaged ones. On the other hand xylogenesis started later and finished sooner in damaged spruce trees compared to the undamaged ones. The biggest differences in cambial activity in beech appeared between class A and class B, and in spruce between class K and class A.

Po žledolomu leta 2014 je v gozdovih ostalo veliko poškodovanih dreves. Ker znanja o nastajanju lesa in skorje v poškodovanih drevesih primanjkuje, smo v Arboretumu Volčji Potok opravili raziskavo vpliva žledoloma na nastajanje lesa in skorje na drevesih, ki so v žledolomu pretrpela poškodbo krošnje. Izbrali smo 14 bukev, jih razvrstili v 4 razrede glede na stopnjo poškodovanosti krošnje (K % nepoškodovana, A % do 50 %, B % med 50 in 75 %, C % več kot 75 % poškodovana krošnja). V dvotedenskih intervalih smo iz njih odvzemali mikro-izvrtke z orodjem Trephor. Iz mikro-izvrtkov smo pripravili preparate lesa, kambija in skorje in jih analizirali s svetlobnim mikroskopom in sistemom za analizo slike. Poškodovane bukve so proizvedle od 20 do 95 % ožje ksilemske branike kot nepoškodovane, manjši je bil tudi prirastek floema. Izmed štirih razredov poškodovanosti so se pri bukvi največje razlike v debelinski rasti pokazale med razredoma A in B. After the severe ice storm in 2014, numerous damaged trees were not removed from forests. Due to the lack of general knowledge about the processes occurring in damaged trees, a study involving 14 European beeches was conducted in the Arboretum Volčji Potok. Trees were categorized by crown injury injury class K % undamaged, A % damaged less than 50 %, B % damaged between 50 and 75 %, and C % damaged more than 75 %. During the 2014 growing season, micro-cores were collected every fortnight using a Trephor tool. Changes in crowns were also observed and noted. Transverse sections of micro-cores were prepared and observed using light microscopy and an image analysis system. Xylem growth rings were 20 to 95 % narrower in damaged beech trees compared to the undamaged trees. Damaged trees also produced narrower phloem rings. The biggest differences in cambial activity in beech appeared between Class A and Class B.

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs (2) the occurrence of IADFs in different species and environments (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events.

We present wood formation in chestnut (Castanea sativa) during the growing seasons 2008 and 2009, compare its dynamics in the two years and discuss possible effects on wood quality. To this purpose, microcores containing wood, cambium and phloem were collected at weekly intervals from 10 chestnut trees growing at the Cimini mountains near Viterbo, Central Italy. In 2008, the onset of wood formation started before the first sampling on 17 April 2008. Onset of lignifi cation of the fi rst formed vessels was observed around 23 April (day of the year DOY 113.8 ± 5.3) and the fi rst latewood vessels were observed around 5 June 2008 (DOY 156.5 ± 7.7). Latewood formation continued until 29 September 2008 (DOY 273.9 ± 10.5) when the terminal cells of the newly formed xylem ring were fully lignifi ed. In 2009, the main phases of wood formation generally occurred earlier than in 2008. The expansion of earlywood vessels was observed around 10 April (DOY 99.7 ± 6.1), the onset of lignifi cation around 22 April (DOY 111.9 ± 7.4) and the first latewood vessels around 28 May 2009 (DOY 147.9 ± 4.7). Lignifi cation of the last formed cells was completed by 26 September 2009 (DOY 273.9 ± 10.5). The average duration of tree-ring formation was 161 days in 2008 and 169 days in 2009, the average ring widths were 3296 ± 1514 μm in 2008 and 3166 ± 1073 μm in 2009, and latewood percentages comprised 76% and 74% of the 2008 and 2009 tree-rings, respectively. The small differences in timing of wood formation phases in the two study years are probably due to small variations in climatic conditions between the two years and they did not seem to have a major impact on ring widths and latewood percentages, which are two important parameters affecting wood quality in ring porous wood species. Rad obrađuje stvaranje drva pitomog kestena (Castanea sativa) tijekom vegetacije u 2008. i 2009. godini. Uspoređuje se dinamika stvaranja drva u te dvije godine i raspravlja o mogućem utjecaju na njegovu kvalitetu. Za tu su svrhu s deset stabala pitomog kestena u planinama Cimini, pokraj mjesta Viterbo u središnjoj Italiji, u tjednim intervalima skupljeni mikroizvrtci koji su sadržavali drvo, kambij i fl oem. Početak stvaranja drva u 2008. godini dogodio se prije uzimanja prvih uzoraka 17. travnja 2008. Početak lignifi kacije prvooblikovanih traheja primijećen je oko 23. travnja (dan u godini DOY 113,8 ± 5,3), a prve traheje kasnog drva primijećene su oko 5. lipnja (DOY 156,5 ± 7,7). Stvaranje kasnog drva nastavljeno je do 29. rujna 2008. (DOY 273,9 ± 10,5), kad su završne stanice novostvorenoga goda drva bile potpuno lignifi cirane. U 2009. godini glavne su se faze stvaranja drva uglavnom pojavile ranije nego u 2008. godini. Širenje traheja ranog drva primijećeno je oko 10. travnja (DOY 99,7 ± 6,1), početak lignifi kacije oko 22. travnja (DOY 111,9 ± 7,4), a prve traheje kasnog drva oko 28. svibnja 2009. (DOY 147,9 ± 4,7). Lignifi kacija zadnjih proizvedenih stanica završena je do 26. rujna 2009.(DOY 273,9 ± 10,5). Prosječno trajanje stvaranja goda drva u 2008. godini iznosilo je 161 dan, a u 2009. godini 169 dana. Prosječne širine godova bile su 3296 ± 1514 μm u 2008. godini i 3166 ± 1073 μm u 2009. godini, a postotni udjel kasnog drva iznosio je 76 i 74% godova u 2008., odnosno u 2009. godini. Male razlike u vremenu početka pojedine faza stvaranja drva u dvjema promatranim godinama vjerojatno su posljedica malih varijacija klimatskih uvjeta između te dvije godine i čini se da nemaju velik utjecaj na širinu godova ni na postotak kasnog drva, a to su dva važna čimbenika koji utječu na kvalitetu drva prstenasto poroznih vrsta.