31 Les/Wood, Vol. 71, No. 1, June 2022 TREE-RING CHRONOLOGIES OF PICEA ABIES, LARIX DECIDUA AND FAGUS SYLVATICA ALONG ALTITUDINAL GRADIENTS KRONOLOGIJE ŠIRIN BRANIK DREVESNIH VRST PICEA ABIES, LARIX DECIDUA IN FAGUS SYLVATICA VZDOLŽ GRADIENTOV NADMORSKE VIŠINE Klemen Novak 1* , Martin de Luis 2 , Nina Škrk 1 , Aleš Straže 1 , Katarina Čufar 1 UDK 630*561.24:630*111 Received / Prispelo: 31. 5. 2022 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 9. 6. 2022 . Abstract / Izvleč ek Abstract: The dendrochronological climate signal of Norway spruce (Picea abies), European larch (Larix decidua), and European beech (Fagus sylvatica), among others, depends on altitude, therefore we have to collect dendrochronological data systematically for each species along altitude gradients. To this end, we established local tree-ring chronologies for the three species along two elevation gradients: (1) Kokra – Jezersko with sites at 750, 780, 950, 1200, 1250, 1380, 1600 m a.s.l., and (2) Bled – Radovna – Krma with sites at 518, 550, 580, 700, 750, 900, 950, 1000, 1200, 1400, 1600, 1760, 1900, 2040 m a.s.l. We present the main characteristics of the chronologies and the results of the dendroclimatological analyses, which show how the climatic factors influence the variation of the tree rings in dependence of altitude and species. We also present the agreement of the different chronologies in terms of standard dendrochronological parameters such as the t-value and discuss the potential use of the presented database. Keywords: Norway spruce (Picea abies), European larch (Larix decidua), European beech (Fagus sylvatica), tree rings, dendrochronology, altitudinal gradients, climate, Slovenia Izvleček: Dendrokronološki signal navadne smreke (Picea abies), evropskega macesna (Larix decidua) in navadne bukve (Fagus sylvatica) je med drugim odvisen od nadmorske višine, zato moramo za razumevanje dendrokronološkega signala sistematično zbirati podatke o posamezni vrsti vzdolž višinskih gradientov. V ta namen smo zbrali vzorce lesa in sestavili lokalne kronologije širin branik omenjenih treh vrst z območij vzdolž dveh gradientov: (1) Kokra – Jezersko, ki vključuje lokacije na 750, 780, 950, 1200, 1250, 1380 in 1600 m nadmorske višine, in (2) Bled – Radovna – Krma z rastišči na 518, 550, 580, 700, 750, 900, 950, 1000, 1200, 1400, 1600, 1760, 1900, 2040 m n. v. Predstavljamo glavne značilnosti kronologij in rezultate dendroklimatoloških analiz, ki so potrdile, da se podnebni dejavniki, ki vplivajo na variiranje širin branik, spreminjajo z nadmorsko višino in da je to spreminjanje širin branik različno pri posamezni drevesni vrsti. Predstavljamo tudi ujemanje različnih kronologij z vidika standardnih dendrokronoloških parametrov, kot je t-vrednost, in razpravljamo o možni uporabi predstavljene podatkovne baze. Ključne besede: navadna smreka (Picea abies), evropski macesen (Larix decidua), navadna bukev (Fagus sylvatica), branike, dendrokronologija, gradient nadmorske višine, podnebje, Slovenija 1 INTRODUCTION 1 UVOD Norway spruce (Picea abies), European larch (Larix decidua), and European beech (Fagus syl- vatica) in Slovenia have particular species-specific tree-ring characteristics in relation to climatic fac- tors which affect the importance of each species in dendrochronology. Since the climatic signal de- pends on altitude, the construction of local chro- nologies of trees from known sites along altitudi- Vol. 71, No. 1, 31-46 DOI: https://doi.org/10.26614/les-wood.2022.v71n01a04 1 Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo, Jamnikarjeva 101, 1000 Ljubljana, SLO * e-mail: klemen.novak@bf.uni-lj.si 2 Universidad de Zaragoza, Departamento de Geografia, Calle de San Juan Bosco 7, 50009 Zaragoza, ES 32 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine nal gradients represents an important step in their dendrochronological characterization, including the issues of teleconnection (similarity of the den- drochronological signal of the same species over longer distances) and heteroconnection (similarity of the dendrochronological signal between differ- ent species). European beech has a wide natural range and grows on a great variety of sites (Euforgen, 2022), and is important for dendroecological studies throughout Europe (e.g., Di Filippo et al., 2007; Martinez del Castillo et al., 2022). The dendrochron- ological signal of beech shows a variable response to climatic factors depending on altitude and lat- itude (Čufar et al., 2008; Di Filippo et al., 2007; Martinez del Castillo et al., 2018). In temperate zones of Central Europe, including Slovenia, low- land beech responds mainly negatively to hot and dry late spring and early summer (May, June, July) weather, while at higher elevations and cold sites it responds positively to summer temperatures (e.g., Čufar et al., 2008; Di Filippo et al., 2007). Numerous studies have also shown that frequent climatic ex- tremes such as ice storms, late frosts, and excessive summer heat negatively affect beech growth (Bas- cietto et al., 2018; Decuyper et al., 2020; Gazol et al., 2019; Martinez del Castillo et al., 2022; Rožen- bergar et al., 2020). It is thus assumed that beech might decline at numerous sites as climate change progresses (Martinez del Castillo et al., 2022). Beech is currently the most common forest tree species in Slovenia, accounting for 32.9% in the wood stock (ZGS, 2021). Its wood is a highly val- ued industrial timber for numerous uses (Čufar et al., 2017). Despite this, it is rarely found in historical objects, and we do not have long composed region- al chronologies for dating (Čufar et al., 2012). Norway spruce is one of the most important coniferous tree species with a wide distribution area (Euforgen, 2022). Basically, it is a species of cold environments, which has been widely artifi- cially spread in Central Europe (including Austria, Germany, Czech Republic, Switzerland, Slovenia) even in lowland areas (e.g., Caudullo et al., 2016; Jansen et al., 2017; Kolář et al., 2020; Marincek et al., 2003). It is an important wood species for vari- ous uses (Straže et al., 2022), wood formation and dendroecology (e.g., Kolář et al., 2020; Martinez del Castillo et al., 2018), dendrochronology and for dating historical objects, including musical instru- ments (Bernabei et al., 2017; Cherubini, 2021; Wil- son et al., 2004). Norway spruce is currently the second most common forest tree species in Slovenia, accounting for 30.2% of the wood stock (ZGS, 2021). Its natu- ral range in Slovenia is restricted to high altitudes, mainly in the Alps and the Dinaric Mountains (Brus, 2012; ZGS, 2022). Since the early 19 th century, the species has been artificially spread throughout Slo- venia, including the lowlands (ZGS, 2022), where it is currently severely affected by climate change and associated bark beetle infestations (e.g., de Groot et al., 2021). The dendroclimatological signal of spruce is strongly influenced by local climatic conditions and varies considerably with altitude. This variability is particularly high in Slovenia, where we lack an ad- equate collection of chronologies for dating histor- ical objects (e.g., Bernabei et al., 2018; Čufar et al., 2020). In Slovenia, spruce is found in numerous ob- jects that are often difficult to date, therefore the knowledge of its signal along elevational gradients is particularly important. European larch is a pioneer tree species, able to colonize open land on disturbed soils; it can tolerate very cold temperatures during winter. Its natural range is mainly limited to high mountains, especially the Alps (Euforgen, 2022). In Slovenia it has a share of 1.2% in the wood stock (ZGS, 2021). Its wood is highly valued for its high density and durable heartwood (Čufar, 2006; Gričar & Prislan, 2021). It is and was valued for modern and histori- cal constructions, and can be found in many prom- inent buildings of the Venetian Republic (Levanič et al., 2001). Therefore, long composed tree-ring chronologies have been constructed for this spe- cies, based on wood from trees and historical con- structions (Bebber, 1990; Nicolussi, 1995; Sieben- list-Kerner, 1984). Using subfossil stems preserved in bogs and glaciers it was possible to construct one of the longest multimillennial chronologies of conifers, including Larix decidua, Pinus cembra and Picea abies, spanning 9,111 years (7109 BC to AD 2002) (Nicolussi et al., 2009). Larch from high elevation shows excellent teleconnection over larger areas (Levanič, 2005a; Levanič et al., 2001). However, detailed studies in Slovenia have shown that its dendrochronological 33 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients signal also depends on altitude (Levanič, 2005b) which often makes the dating of historical objects made of “lowland larch” extremely difficult. The main objective of this study is to present the tree-ring chronologies of Norway spruce (Picea abies), European larch (Larix decidua), and Euro- pean beech (Fagus sylvatica) along two altitudinal gradients in the Kamnik-Savinja Alps and the Julian Alps, starting from the lowlands to the altitudinal limit of species distribution in the studied areas. We present (1) the constructed tree-ring chronolo- gies and their main characteristics, (2) how climatic Figure 1. Sampling areas with (a) map of Slovenia, (b) Kokra – Jezersko, and Bled – Radovna – Krma with sampling locations and (c) detailed views of site locations along the altitudinal gradients for three tree spe- cies: European beech (Fagus sylvatica) – FASY; European larch (Larix decidua) – LADE; and Norway spruce – (Picea abies), PCAB. For details see Tables 1 and 2. Source of maps: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroG- rid, IGN, and the GIS User Community. Slika 1. Mesta vzorčenja (a) zemljevid Slovenije, (b) Kokra – Jezersko in Bled – Radovna – Krma z oznakami lokacij vzorčenja ter (c) mesta vzorčenja vzdolž višinskih gradientov za tri vrste: navadno bukev (Fagus syl- vatica)–FASY, evropski macesen (Larix decidua)–LADE in navadno smreko (Picea abies)–PCAB. Za podrob- nosti primerjajte preglednici 1 in 2. Vir zemljevidov: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroG- rid, IGN, and the GIS User Community. 34 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine factors influence tree-ring variations, (3) the vari- ation of their dendrochronological signal, and (4) the potential of the database for future studies ad- dressing various issues related to ecology, climate, and cultural heritage. 2 MATERIALS AND METHODS 2 MATERIAL IN METODE 2.1 STUDY SITES AND TREES 2.1 RAZISKOVALNE PLOSKVE IN DREVESA The experimental design was based on a se- lection of mature dominant or codominant trees of Norway spruce, European larch, and European beech felled in the areas of Kokra – Jezersko, be- tween the Karawanks and Kamnik-Savinja Alps, and Bled – Radovna – Krma, Julian Alps in northwestern Slovenia (Figure 1). The sampling area Kokra – Jezersko is orient- ed south-east in the Kamnik-Savinja Alps. The sam- pling was performed on localities at 750, 780, 950, 1200, 1250, 1380, 1600 m a. s. l.) (Figures 1, 2a, Table 1). The area Bled – Radovna – Krma included lo- calities on 518, 550, 580, 700, 750, 900, 950, 1000, 1200, 1400, 1600, 1760, 1900, 2040 m a. s. l. (Fig- ures 1, 2b, Table 2). 2.2 SAMPLE COLLECTION AND PREPARATION 2.2 VZORČENJE IN OBDELAVA VZORCEV The fieldwork with the collection of samples was carried out from March until November 2019 in cooperation with forest owners, the Slovenia For- est Service, local foresters, the Triglav National Park in the area Bled – Radovna – Krma, and the Munic- ipality of Jezersko in the area Kokra – Jezersko with corresponding permissions. We aimed to collect 15 trees per site. After regular felling we collect- ed discs at the lower part of the trees (mainly 4 m above ground level). If the number of felled trees was not sufficient, additional samples were collect- ed by coring from the nearby living trees. For this purpose, two cores per tree were extracted at the breast height, perpendicular to the tree axis from the bark to the pith using a Haglöf increment corer combined with a Haglöf increment borer chuck and a cordless drilling machine (Milwaukee, M18 FDD2- 502X FUEL-135 Nm). The samples were labelled with the identifying system of the codes, which contained information on sampling site, tree species, tree number and the radius. The sampled discs and cores fixed on wooden supports were transported to the workshop and air dried. Their transversal surfaces were sanded with the belt sander using progressively finer sandpa- per, from 80, 120, 180, 220, 280, and 360 grit until the tree rings and individual cells in the wood on the transversal section were perfectly visible under a stereo microscope. The wood surface was scanned with a Mustek S-series 2400 Plus flatbed scanner with the reso- lution set at 1200 dpi and the images were pro- cessed with Adobe Photoshop Elements 2020. In the case of extremely narrow rings the structure of Figure 2. Selected locations from two areas with similar site characteristics: (a) Kokra – Jezersko with sam- pling locations J02, J03, J04 and J06, and (b) Krma with sampling locations KR1, KR2, KR3 and KR4. Slika 2. Izbrane lokacije z dveh območij s podobnimi rastiščnimi razmerami: (a) Kokra – Jezersko z lokacija- mi vzorčenja J02, J03, J04 in J06 in (b) Krma z lokacijami vzorčenja KR1, KR2, KR3 and KR4. 35 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients wood was additionally checked under an Olympus stereo microscope S2 11 or images were obtained with the help of confocal laser scanning microscope CLSM (Balzano et al., 2019). 2.3 DATA ACQUISITION AND PROCESSING 2.3 ZAJEM IN OBDELAVA PODATKOV Tree-ring widths were measured using calibrat- ed high-resolution digital photos along two radii of each tree, to the nearest 0.01 mm using the CDen- dro / CooRecorder 9.5 image analysis program (Cy- bis Elektronik, 2022 http://www.cybis.se/forfun/ dendro/helpcoorecorder7/index.php). The TSAP- Win program (Frank Rinn, Heidelberg, Germany) and R Studio program using the dplR library (Bunn, 2010) were used for visual and statistical cross-dat- ing and verification. Cross-dated tree-ring series were assembled into local chronologies using R Studio and the dplR package (Bunn, 2008). 2.4 TREE RING CHRONOLOGIES AND CLIMATE 2.4 KRONOLOGIJE ŠIRIN BRANIK IN KLIMA The climatic influence on tree growth was ana- lysed using the residual version of each chronology with R Studio. For this purpose, the original tree- ring width series were standardized in a two-step procedure. First, the long-term trend was removed by fitting a negative exponential function (regres- sion line) to each tree-ring series. Second, more flexible detrending was carried out by applying a cubic smoothing spline with a 50% frequency re- sponse of 30 years to further reduce non-climatic variance. Subsequently, autoregressive modelling of the residuals and bi-weight robust estimation of the mean were applied (Cook & Peters, 1997). Local climatic data for calculation were ob- tained from the SLOCLIM data base (Škrk et al., 2021) which is a publicly available modelled climat- ic database which contains a daily gridded dataset of maximum and minimum temperature and pre- cipitation data with 1×1 km spatial resolution cov- ering the entire territory of Slovenia from 1950 to 2018. The data are available on zenodo (Škrk et al., 2020, 2021) and on the web page www.sloclim.eu. For each sampling location we extracted the climat- ic data of the nearest grid point and aggregated the daily data into monthly mean values. Pearson correlation function coefficients (CFC) were calculated by using the residual version of each tree-ring chronology as a dependent variable and the regressors monthly minimum and maxi- mum temperatures and the monthly sums of pre- cipitation for each biological year from the previous January to current December, as well as for the past and current spring, summer, autumn and current winter for the period 1950-2018. The climate and growth relationships were calculated using the pro- gram packages library(“dplR”), library(“stringr”), and library(“plyr”). The CFC values were considered statistically significant when p<0.05. 2.5 TELECONNECTION AND HETEROCONNECTION 2.5 TELEKONEKCIJA IN HETEROKONEKCIJA To test the potential of the chronologies with regard to establishing regional chronologies for dat- ing purposes, we made basic comparisons among the chronologies by calculating standard statistical values, including the t-value after Baillie and Pilcher (tBP) and sign test (Gleichläufigkeit–Glk) using the TSAP-Win program. We also tested the chronologies for telecon- nection (agreement between the chronologies of the same species from different sites) and for het- eroconnection (agreement between different tree species from the same site). 3 RESULTS AND DISCUSSION 3 REZULTATI IN RAZPRAVA 3.1 TREE-RING DATA AND THE CHRONOLOGIES 3.1 KRONOLOGIJE ŠIRIN BRANIK The database consists of 47 chronologies of three species along two altitudinal gradients in the Alps of Slovenia. We present their locations and time spans (Table 1 and 2). The local chronologies had average lengths of 156 (69-296) years for Euro- pean beech, 139 (57-355) years for Norway spruce, and 191 (56-378) years for European larch. At Kokra – Jezersko the corresponding averag- es (minimum-maximum) for seven beech chronol- ogies were 133 (69-296) years, for seven spruce chronologies 135 (57-246) years, and for six larch chronologies 156 (56-214) years (Table 1). At Bled – Radovna – Krma the averages (min- imum-maximum) for seven beech chronologies 36 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine Code / Koda Spe- cies / Dre- vesna vrsta Alti- tude / Nad- mor- ska višina Latitude / Zemljepisna širina Longitude / Zemljepisna dolžina Num- ber of trees / Število dreves Chro- nology Length / Kro- nologija Razpon Start / Zače- tek End / Konec m N / S E / V Years / leta Year / leto Year / leto J01A FASY 750 46.380118° 14.457731° 7 121 1899 2019 J01B FASY 780 46.389231° 14.483326° 10 122 1898 2019 J02 FASY 950 46.410676° 14.505766° 12 78 1941 2018 J12 FASY 1200 46.378934° 14.530259° 18 130 1890 2019 J03 FASY 1250 46.411992° 14.494944° 8 151 1869 2019 J04 FASY 1380 46.419799° 14.499313° 11 169 1850 2018 J06 FASY 1600 46.413493° 14.479713° 10 160 1860 2019 J01B LADE 780 46.389231° 14.483326° 10 162 1858 2019 J02 LADE 950 46.410676° 14.505766° 5 163 1856 2018 J03 LADE 1250 46.411992° 14.494944° 4 153 1866 2018 J04 LADE 1380 46.419799° 14.499313° 10 214 1805 2018 J06 LADE 1600 46.413493° 14.479713° 13 189 1832 2020 J24 LADE 1600 46.396635° 14.550305° 10 56 1964 2019 J01A PCAB 750 46.380118° 14.457731° 18 145 1874 2018 J01B PCAB 780 46.389231° 14.483326° 15 174 1846 2019 J02 PCAB 950 46.410676° 14.505766° 30 89 1930 2018 J12 PCAB 1200 46.378934° 14.530259° 17 138 1882 2019 J03 PCAB 1250 46.411992° 14.494944° 14 133 1887 2019 J04 PCAB 1380 46.419799° 14.499313° 15 97 1922 2018 J06 PCAB 1600 46.413493° 14.479713° 12 246 1774 2019 Table 1. Kokra – Jezersko, ba- sic information on the sites and chronologies along the gradient (short code, species, altitude, latitude, longitude, number of trees, useful length of the chro- nology and its start and end date) for three tree species: European beech (Fagus sylvatica) – FASY: European larch (Larix decidua) – LADE, and Norway spruce (Picea abies) – PCAB. Preglednica 1. Kokra – Jezersko, osnovni podatki o rastiščih in kro- nologijah vzdolž gradienta nad- morske višine (kratka koda, dre- vesna vrsta, nadmorska višina, zemljepisna širina, zemljepisna dolžina, število dreves, uporab- na dolžina kronologije ter prvo in zadnje leto) za tri drevesne vrste: navadna bukev (Fagus syl- vatica)–FASY, evropski macesen (Larix decidua)–LADE in navadna smreka (Picea abies)–PCAB. were 179 (69-296) years, for 11 spruce chronologies 142 (81-355) years, and for nine larch chronologies 215 (84-378) years. The oldest trees were sampled in Krma (KR*) (Table 2). 3.2 TREE-RINGS AND CLIMATE 3.2 ŠIRINE BRANIK IN KLIMA Correlation function coefficients (CFCs) for re- sidual chronologies and monthly minimum (Tmin) and maximum temperatures (Tmax) and precipita- tion (PCP) (Figures 3 and 4) from the previous Jan- uary to current December and from the previous and current spring, summer, autumn and current winter show that each of the species has a unique response to climate and that the response varies with elevation. For example, in Kokra – Jezersko (Figure 3) beech shows a negative response to June temper- atures (especially Tmax) and a positive response to June precipitation. The values of the CFCs gener- ally decrease from lower to higher altitude, while at 1600 m a.s.l. we observe a positive response to temperatures in July, August and September. Spruce shows a negative response to tempera- tures in July and August and a positive response to precipitation in July at the same gradient, while at 1600 m a.s.l. a positive response to temperatures in May and August is observed. Larch shows a neg- ative response to Tmax in March and a positive re- sponse to summer temperatures, while at altitudes above 1250 m a.s.l. we observe a positive response to May temperatures, especially Tmax, and a pos- 37 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients itive response to August temperatures with lower values of correlation coefficients. Species responses along the Bled – Radovna – Krma slope differ from those at Jezersko. Beech shows a negative response to June temperatures in Hom (518 a.s.l.), while the Radovna and Krma sites respond mainly positively to May temperatures and negatively to March temperatures. Spruce at lower elevations shows a positive influence of January, February and March temperatures, while at ele- vations above 1000 m a positive influence of May temperatures is observed. Larch shows a negative response to Tmax in March and a positive response to temperatures in May. Code / Koda Spe- cies / Dre- vesna vrsta Alti- tude / Nad- mor- ska višina Latitude / Zemljepisna širina Longitude / Zemljepisna dolžina Num- ber of trees / Število dreves Chro- nology Length / Krono- logija Razpon Start / Zače- tek End / Konec m N / S E / V Years / leta Year / leto Year / leto HOM FASY 550 46.401975° 14.117478° 15 146 1874 2019 RA01 FASY 700 46.430571° 13.952667° 14 69 1951 2019 RA02 FASY 750 46.423824° 13.938677° 15 115 1905 2019 RA03 FASY 900 46.435654° 13.928797° 20 188 1833 2020 KR01 FASY 1000 46.386683° 13.907620° 18 239 1780 2018 KR02 FASY 1200 46.370348° 13.888781° 10 198 1822 2019 KR03 FASY 1400 46.366540° 13.879257° 10 296 1724 2019 RA01 LADE 700 46.430571° 13.952667° 20 174 1846 2019 RA02 LADE 750 46.423824° 13.938677° 12 195 1824 2018 RA03 LADE 900 46.435654° 13.928797° 7 84 1936 2019 KR01 LADE 1000 46.386683° 13.907620° 15 181 1833 2013 KR02 LADE 1200 46.370348° 13.888781° 10 154 1866 2019 KR03 LADE 1400 46.366540° 13.879257° 16 141 1880 2020 KR04 LADE 1600 46.366383° 13.869982° 7 328 1692 2019 KR05 LADE 1760 46.368392° 13.867702° 12 378 1642 2019 KR06 LADE 1900- 2040 46.370559° 13.861593° 12 303 1717 2019 HOM PCAB 518 46.359262° 14.110083° 11 110 1910 2019 BLS PCAB 580 46.399197° 14.117837° 12 98 1922 2019 RA01 PCAB 700 46.430571° 13.952667° 20 107 1913 2019 RA02 PCAB 750 46.423824° 13.938677° 23 155 1864 2018 RA03 PCAB 900 46.435654° 13.928797° 12 110 1909 2018 PER PCAB 950 46.402138° 14.021151° 15 81 1939 2019 KR01 PCAB 1000 46.386683° 13.907620° 19 164 1855 2018 KR02 PCAB 1200 46.370348° 13.888781° 9 172 1848 2019 KR03 PCAB 1400 46.366540° 13.879257° 15 116 1904 2019 KR04 PCAB 1600 46.366383° 13.869982° 11 355 1665 2019 KR05 PCAB 1760 46.368392° 13.867702° 4 95 1925 2019 Table 2. Bled – Radovna – Krma, basic information on the sites and chronologies along the gra- dient (short code, species, alti- tude, latitude, longitude, num- ber of trees, useful length of the chronology and its start and end date) for three tree species: European beech (Fagus sylvati- ca) – FASY, European larch (Lar- ix decidua) – LADE, and Norway spruce (Picea abies) – PCAB. Preglednica 2. Bled – Radovna – Krma, osnovni podatki o ras- tiščih in kronologijah vzdolž gra- dienta nadmorske višine (kratka koda, drevesna vrsta, nadmor- ska višina, zemljepisna širina, zemljepisna dolžina, število dre- ves, uporabna dolžina kronolo- gije ter prvo in zadnje leto) za tri drevesne vrste: navadna bukev (Fagus sylvatica)–FASY, evropski macesen (Larix decidua)–LADE in navadna smreka (Picea abies)– PCAB. 38 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine Figure 3. Kokra-Jezersko correlation function coefficients between tree-ring width indices and climate var- iables (for details, see Figure 4 caption). Slika 3. Kokra – Jezersko korelacijski koeficienti med indeksi širin branik in klimatskimi spremenljivkami (za podrobnosti glejte napis pod sliko 4). 39 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients 40 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine The presented complex response to climatic parameters with similarities and differences among species and sites requires confirmation with fur- ther studies using principal component analysis (e.g., Čufar et al., 2014, 2008) or other methods. 3.2 COMPARISONS OF CHRONOLOGIES 3.2 PRIMERJAVA KRONOLOGIJ The comparison of chronologies using tBP values shows that at the Kokra – Jezersko gradi- ent most of the chronologies of the same species showed tBP≥4, which is considered to indicate sta- tistically significant similarity (Table 3). Comparison of the chronologies J2, J3, J4 and J6 from locations on the same slope (Figure 2a) showed the highest similarity between nearby altitudes and smallest between the two extreme altitudes at 950 and 1600 m a.s.l. Heteroconnection, i.e. similarity be- tween the chronologies of different species, is ob- served only occasionally (Table 3). The cross-correlations at the Bled – Radov- na – Krma gradient of the same species generally show some similarity between nearby locations and no similarity between lowest and highest el- evations (Table 4). Highest similarity between the chronologies KR1, KR2, KR3 and KR4 could be partly explained by the location of the sites in the valley (Figure 2b) Heteroconnection is observed only oc- casionally (Table 4). 4 CONCLUSIONS 4 ZAKLJUČKI The 47 tree-ring chronologies of Norway spruce (Picea abies), European larch (Larix decid- ua), and European beech (Fagus sylvatica) for two altitudinal ranges in the Kamnik-Savinja Alps and the Julian Alps, starting from the lowlands to the altitudinal limit of species distribution, show varia- bility in tree-ring response to climate. Correlation function coefficients (CFCs) for re- sidual chronologies and monthly minimum (Tmin) and maximum temperatures (Tmax) and precip- itation from the previous January to current De- cember and from the previous and current spring, summer, autumn and current winter vary along the altitudinal gradient. Figure 4. Bled – Radovna – Krma: correlation function coefficients for the residual chronologies of Euro- pean beech (FASY), Norway spruce (PCAB), European larch (LADE) from various elevations and monthly minimum (Tmin, gray lines) and maximum temperatures (Tmax, orange lines) and precipitation (PCP, bars) from the previous January (01p) to current December (12) and the past and current spring (pSPR, SPR), summer (pSUM, SUM), autumn (pAUT, AUT) and current winter (WIN) for the period 1950-2018. CFC val- ues are statistically significant (p<0.05) if >0.2084 or <-0.2084 (for legend, see Figure 3). Slika 4. Bled – Krma: korelacijski koeficienti med rezidualnimi verzijami kronologij za navadno bukev (FASY), navadno smreko (PCAB) in evropski macesen (LADE) ter mesečnimi minimalnimi (Tmin, sive črte) in maksi- malnimi temperaturami (Tmax, oranžne črte) ter padavinami (PCP, stolpci) od preteklega januarja (01p) do decembra (12) tekočega leta, ter za preteklo in tekočo pomlad (pSPR, SPR), poletje (pSUM, SUM), jesen (pAUT, AUT) in zimo (WIN) za obdobje 1950–2018.Vrednosti koeficientov so statistično značilne (p<0,05), če so manjše od -0,2084, ali večje od 0,2084 (za legendo glejte sliko 3). 41 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients Standard dendrochronological parameters (tBP) calculated between the chronologies from the Kokra–Jezersko gradient showed that most of the chronologies of the same species along the gra- dient showed similarity (tBP≥4). In the subset of chronologies from locations on the same slope the greatest similarity was found between the nearby altitudes and smallest between the two extreme al- titudes at 950 and 1600 m a.s.l. Heteroconnection, i.e. similarity between the chronologies of different species, was observed only occasionally. The rela- tionships between the Bled – Radovna – Krma chro- nologies seem to be more complex, and require a detailed study. The presented results show that the relation- ship between tree growth and climate is not only affected by altitude and the corresponding climatic conditions. The complex relationships need to be further investigated with an appropriate methodol- ogy, such as principal component analysis. The database shows great potential for future studies of spruce, larch, and beech from cold envi- ronments in the southern Alps in a time of chang- ing climate. The local chronologies with average lengths of 156 (69-296) years for beech, 139 (57- 355) years for spruce, and 191 (56-378) years for larch also provide a basis for the construction of master chronologies for dating cultural heritage ob- jects. In Slovenia and in the surrounding areas such Table 3. Cross-correlation values of tBP (t-value after Baillie and Picher) between Kokra – Jezersko raw chronologies (J1A-J6, maximum overlap) of Norway spruce, Picea abies, PCAB, European larch, Larix decid- ua, LADE, and European beech, Fagus sylvatica, FASY, from different altitudes. Values tBP≥4 with statisti- cally significant similarity are marked. Preglednica 3. Korelacijske vrednosti tBP (t-vrednost po Baillieju in Picherju) med surovimi kronologijami Kokra – Jezersko (J1A-J6, maksimalno prekrivanje) smreke, Picea abies, PCAB, evropskega macesna, Larix decidua, LADE in evropske bukve, Fagus sylvatica, FASY, z različnih nadmorskih višin. Vrednosti tBP≥4 so statistično značilne in so označene. 42 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine chronologies are particularly needed for spruce (e.g., Bernabei et al., 2017; Čufar et al., 2020). The sampling material and data are stored in the archive of the Chair for Wood Science at the Department of Wood Science and Technology, Bio- technical Faculty, University of Ljubljana. 5 SUMMARY 5 POVZETEK Predstavljamo mrežo lokalnih kronologij na- vadne smreke (Picea abies), evropskega macesna (Larix decidua) in navadne bukve (Fagus sylvatica) vzdolž dveh gradientov nadmorskih višin na obmo- čju Kokra – Jezersko v Kamniško Savinjskih Alpah in Bled – Radovna – Krma v Julijskih Alpah v Sloveniji. Vsaka od izbranih vrst ima svoje posebnosti z vidika dendrokronologije. Bukev, ki je v Evropi in Sloveniji zelo razširjena, pogosto uporabljamo kot modelno vrsto v dendroekologiji ter za proučevanje učinkov klimatskih sprememb na vegetacijo (npr. Čufar et al., 2008; Di Filippo et al., 2007; Martínez del Castillo et al., 2019, 2022). Redkeje se srečamo z bukovimi predmeti iz preteklih obdobij, ki bi jih želeli dendro- kronološko datirati (Čufar et al., 2012). Smreka je prav tako zelo razširjena v Evropi in Sloveniji. V splošnem je to vrsta hladnih okolij, ki so jo v zadnjih dvesto letih razširili tudi na manj primerna rastišča na nižjih nadmorskih višinah. Pogosto jo proučuje- mo kot modelno drevesno vrsto v dendroekologiji (npr. Martinez del Castillo et al., 2018). Smreka je pogosta v zgodovinskih konstrukcijah, predmetih Table 4. Cross-correlation values of tBP (t-value after Baillie and Picher) between Bled – Radovna – Krma raw chronologies (HOM-KR6, common period 1900-2020) of Norway spruce, Picea abies, PCAB, European larch, Larix decidua, LADE, and European beech, Fagus sylvatica, FASY, from different altitudes. Values of tBP≥4 with statistically significant similarity are marked. Preglednica 4. Korelacijske vrednosti tBP (t-vrednost po Baillieju in Picherju) med surovimi kronologijami Bled – Radovna – Krma (HOM-KR6, skupno obdobje 1900–2020) smreke, Picea abies, PCAB, evropskega macesna, Larix decidua, LADE, in evropske bukve, Fagus sylvatica, FASY, z različnih nadmorskih višin. Vred- nosti tBP≥4 so statistično značilne in so označene. 43 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients in glasbenih inštrumentih. Dendrokronološki signal smreke po Sloveniji zelo variira, ker je v veliki meri odvisen od nadmorske višine, zato za Slovenijo še nismo uspeli sestaviti dobrih referenčnih krono- logij za datiranje (npr. Bernabei et al., 2017; Čufar et al., 2020). Macesen je v Sloveniji manj razširjen kot bukev in smreka (ZGS, 2021), a je pomemben z vidika uporabe lesa, ter tudi za dendrokronološke raziskave. Kot cenjena lesna vrsta je pogost tudi v predmetih kulturne dediščine. Macesen z visokih nadmorskih višin, ki je bil uporabljen za prestižne konstrukcije Benečanov, ima dobro telekonekcijo (Levanič et al., 2001). Tudi dendrokronološki signal macesna je zelo odvisen od nadmorske višine, zato za nižje nadmorske višine še nimamo ustreznih kro- nologij za datiranje. Cilj te študije je bil predstaviti (1) kronologije in njihove glavne značilnosti, (2) kako podnebni de- javniki vplivajo na variiranje širin branik, (3) kako se dendrokronološki signal posamezne vrste spremi- nja z nadmorsko višino in (4) kakšen potencial ima predstavljena podatkovna zbirka za bodoče raziska- ve na področju ekologije in kulturne dediščine. Vzorce lesa za raziskave smo pridobili na različ- nih nadmorskih višinah: (1) Kokra-Jezersko, na 750, 780, 950, 1200, 1250, 1380 in 1600 m in (2) Bled – Radovna – Krma z rastišči na 518, 550, 580, 700, 750, 900, 950, 1000, 1200, 1400, 1600, 1760, 1900, 2040 m n. v. Na vsakem rastišču smo v času redne sečnje iz posekanih dreves na nivoju 4 m od baze drevesa odžagali kolut. V kolikor število posekanih dreves ni bilo zadostno, smo iz rastočih dreves na posame- znem rastišču odvzeli izvrtke. Prečne prereze vzorcev smo gladko zbrusili in jih skenirali pri ločljivosti 1200 dpi. Na slikah smo izmerili širine branik s programom CDendro / Cooo Recorder 9.5 (Cybis Elektronik, 2022 http://www. cybis.se/forfun/dendro/helpcoorecorder7/index. php). Za vizualno in statistično sinhronizacijo smo uporabili program TSAP-Win (Frank Rinn, Heidel- berg, Nemčija) in paket dplR v programu R Studio (Bunn, 2010). Sinhronizirana in datirana zaporedja širin bra- nik smo uporabili za sestavo lokalnih kronologij s programom R Studio z uporabo paketa dplR (Bunn, 2008). Izračunali smo tri različice kronologij: kro- nologijo širin branik ter standardno in rezidualno kronologijo. Za proučevanje vpliva klime na rast dreves smo uporabili rezidualno kronologijo z upo- rabo programa R Studio. Lokalni vremenski podatki za izračune so bili pridobljeni iz podatkovne baze SLOCLIM (Škrk et al., 2021). Opravili smo osnovne primerjave med krono- logijami z izračunom standardnih statističnih vred- nosti (predvsem t-vrednost Baillie in Pilcher, tBP) s programom TSAP-Win. Kronologije smo testirali tudi z vidika teleko- nekcije (ujemanje med kronologijami iste vrste z različnih lokacij) in heterokonekcije (ujemanje med kronologijami različnih drevesnih vrst z istega ob- močja). Za vseh 47 kronologij za 3 drevesne vrste smo predstavili natančne zemljepisne koordinate, števi- lo dreves, uporabno dolžino ter prvo in zadnje leto kronologije (preglednica 1 in 2). Za vseh 47 kronologij 3 drevesnih vrst smo predstavili korelacijske koeficiente (CFC) med inde- ksi širin branik (rezidualne kronologije) ter meseč- nimi minimalnimi (Tmin) in maksimalnimi tempe- raturami (Tmax), padavinami (PCP) od preteklega januarja do decembra tekočega leta, ter za preteklo in tekočo pomlad, poletje, jesen in zimo za obdobje 1950–2018. Rezultati za Kokro – Jezersko (slika 3) kažejo, da se bukev negativno odziva na junijske tempera- ture (zlasti Tmax), pozitivno pa na junijske padavi- ne. Vrednosti korelacijskih koeficientov (CFC) se na splošno zmanjšujejo od nižje proti višji nadmorski višini, medtem ko na nadmorski višini 1600 m opa- žamo pozitiven odziv na temperature v juliju, avgu- stu in septembru. Smreka se negativno odziva na temperature julija in avgusta ter pozitivno na pa- davine julija na večini gradienta, medtem ko je na 1600 m nadmorske višine opazen pozitiven odziv na temperature v maju in avgustu. Macesen kaže negativen odziv na Tmax v marcu in pozitiven odziv na poletne temperature, medtem ko na nadmorski višini nad 1250 m opažamo pozitiven odziv na maj- ske temperature, zlasti Tmax, in pozitiven odziv na avgustovske temperature z nižjimi vrednostmi ko- relacijskih koeficientov. Rezultati na območju Bled – Radovna – Krma se razlikujejo od rezultatov na Jezerskem. Bukev kaže negativen odziv na junijske temperature na Homu (518 m n. v.), medtem ko se na rastiščih v Ra- dovni in Krmi drevesa odzivajo večinoma pozitivno na majske temperature in negativno na marčevske. 44 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine Smreka na nižjih nadmorskih višinah kaže pozitiven odziv na januarske, februarske in marčevske tem- perature, medtem ko je na nadmorskih višinah nad 1000 m opazen pozitiven vpliv majskih temperatur. Macesen kaže negativen odziv na Tmax v marcu in pozitiven odziv na temperature v maju. Ker je odziv različnih vrst na različnih nadmor- skih višinah na dveh območjih zelo kompleksen, bi bilo dobljene podatke treba analizirati še z drugimi metodami, na primer z analizo glavnih komponent (npr. Čufar et al., 2008, 2014). Navzkrižne korelacije z izračunom parametra tBP (kjer tBP≥4 pomeni statistično značilno podob- nost), kažejo, da je na Jezerskem večina kronologij vsaj v določeni meri podobnih (tBP≥4) (pregledni- ca 3). Primerjava kronologij J2, J3, J4 in J6 z lokacij z enako ekspozicijo (slika 2a) je pokazala največjo podobnost med bližnjimi nadmorskimi višinami in najmanjšo med dvema skrajnima nadmorskima višinama na 950 in 1600 m. Heterokonekcija, tj. primerjava kronologij različnih vrst, je pokazala, da imajo različne vrste na isti lokaciji podoben dendro- kronološki signal samo v posameznih primerih (pre- glednica 3). Korelacije med kronologijami vzdolž gradienta Bled – Radovna – Krma kažejo nekaj podobnosti iste vrste na bližnjih lokacijah. Med kronologijami z najnižjih in najvišjih nadmorskih višin pa ni bilo po- dobnosti v dendrokronološkem signalu (pregledni- ca 4). Najbolj so si bile podobne kronologije KR1, KR2, KR3 in KR4, kar bi lahko delno pojasnili z lego rastišč v isti dolini (slika 2b). Podobnost dendrokro- noloških signalov med vrstami (heterokonekcija) je bila zabeležena le v nekaj primerih (preglednica 4). Predstavljeni rezultati kažejo, da na rast (vari- iranje širin branik) ne vplivajo le nadmorska višina in pripadajoče podnebne razmere. Kompleksne odnose med kronologijami bi bilo treba dodatno raziskati. Prikazani rezultati kažejo na velik potencial po- datkovne zbirke za prihodnje študije dendrokrono- loških posebnosti vrst navadne smreke (Picea abi- es), evropskega macesna (Larix decidua) in navadne bukve (Fagus sylvatica) iz hladnih okolij v južnih Al- pah v spreminjajočem se podnebju. Lokalne krono- logije, ki so v povprečju dolge 156 (69-296) let za bukev, 139 (57-355) za smreko in 191 (56-378) let za macesen, predstavljajo tudi osnovo za izdelavo sestavljenih referenčnih kronologij, ki jih zlasti za smreko potrebujemo za datiranje lesenih predme- tov kulturne dediščine (prim. Čufar et al., 2020). Vzorci za to raziskavo in podatki so shranjeni v arhivu Katedre za tehnologijo lesa na Oddelku za lesarstvo Biotehniške fakultete Univerze v Ljubljani. Pri terenskem in laboratorijskem delu smo bili deležni velike podpore posameznikov, ustanov in podjetij, ki se jim zahvaljujemo za njihovo izjemno pomoč. Zahvaljujemo se tudi za finančno podporo projekta. Podrobnosti so navedene v zahvali. ACKNOWLEDGEMENTS AND FUNDING ZAHVALA IN FINANCIRANJE We would like to thank the numerous individ- uals, organizations, and companies who assisted us in conducting this research: Jeles, proizvodnja in trgovina z lesom (Rok Jelenc and Peter Mohorič), Triglav National Park, Oddelek za varstvo narave (Andrej Arih and Tan- ja Menegalija), Slovenia Forest Service, Območna enota Bled (Janja Lukanc, Rudi Kunstelj and his son Peter, Ferdinand Kokalj), Slovenski državni gozdovi (SiDG) (Štefan Bezovnik) and Gozdno gospodarstvo Bled (Iztok Soklič, Uroš Ambrožič and Matija Ben- edičič), Novomeška nadškofija (Janko Tavčar, Ben- eficij d.o.o.), Ljubljanska nadškofija, forests owners and loggers (Bojan Ambrožič, Matija Pretnar, Luka Karlin, Marko Janša, Janez Lipovec – Psnak), Trgo- vina in servis Resman – Vrbnje, Trgovina in servis Brinca – Lesce, Zavod za varstvo kulturne dediščine Slovenije, Območna enota Kranj (Saša Roškar), The Municipality of Jezersko (Drejc Karničar), Slove- nia Forest Service, Krajevna enota Preddvor (Ivan Srečnik, Tomaž Polajnar, Rolando Nardoni, Igor Nahtigal), Šenkova domačija (Polona V. Karničar in Drejc Karničar), Roblekova Domačija, (Marko Šink- ovec, Matic Šinkovec, Roblek les), Kmetija Spodnji Kovk (Janez Smrtnik), Posek in spravilo lesa Gozd Kokra (Anton Povšnar) We would like to thank Miha Rakar for process- ing the majority of the samples, the members of the Chair for Wood Science for their co-operation and continuous support, Luka Krže, Aleš Straže, Maks Merela, Denis Plavčak, Angela Balzano, Željko Gorišek, Jože Planinšič, Daša Krapež Tomec and the staff of the Department of Wood Science and Tech- nology BF UL for their great support. 45 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients Funding. This study was supported by the project of Ad-Futura (Raziskovalno gostovanje v okviru Javnega razpisa sofinanciranja gostovanj na slovenskih visokošolskih zavodih, 257. JR) and project “Researchers-2.1-UL-BF-952011”, contract no. C3330-19-952011; co-financed by the Ministry of Education, Science, and Sport of the Republic of Slovenia and the EU European Regional Develop- ment Fund and by the Slovenian Research Agency (ARRS) Programs P4-0015 (Wood and lignocellulos- ic composites) and P4-0430 (Forest timber chain and climate change: the transition to a circular bio-economy) and the research project CRP , V4- 2016 LesGoBio supported by the Ministry of Agri- culture, Forestry and Food of the Republic of Slo- venia (MKGP) and ARRS. International cooperation was supported by the by the LLP ERASMUS bilateral agreement between the University of Ljubljana and the University of Alicante. REFERENCES VIRI Balzano, A., Novak, K., Humar, M., & Čufar, K. (2019). Application of confocal laser scanning microscopy in dendrochronology. Les/ Wood, 68(2), 5–17. Bascietto, M., Bajocco, S., Mazzenga, F., & Matteucci, G. (2018). 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