Effect of planting density on diameter structure of black poplar clones S6-7 and M-1 - section Aigeiros [Duby]

The parameters of diameter structure of two black poplar clones in the section Aigeiros Duby (S6-7 and M-1) are presented depending on three different spacings: 3x3 m, 4.25x4.25 m and 6x6 m. Modeling of diameter structure was performed by Weibull’s function of probability distribution. We determined the effect of spacing (density) and clone both on the parameters and on the model diameter structure

Modeli debljinske strukture selekcionisanih klonova crne topole sekcije aigeiros (duby) dobijeni Weibull-ovom distribucijom

The present study was performed in an experimental plantation with six 20-year-old black poplar clones in the Section Aigeiros(Duby). The diameter structure models were constructed using the Weibull probability density distribution with three parameters based on periodical measurements of diameters at breast height. The unidentified parameters were calculated by the so-called “hybrid system” (Knoebel, et al, 1986): location parameter (a) was calculated by percentile method, scale parameter (b) and shape parameter (c) were calculated by moments method. The applied method of estimating the location parameter (a) showed that in 90.6 % of the study sample, the parameter “a” ranged between 50 and 90 %, and in 52.4 % of the sample, “a” ranged from 80 to 90 % of the minimal diameter. With higher plantation ages, location parameter (a) and scale parameter (b) also increased with small oscillations, which was confirmed by the significance of the correlation coefficient of 0.71 and 0.73 respectively. This was shown by the shift of the curve of diameter structure model to the right, towards larger diameters, and in a wider range of diameters at breast height with a lower relative frequency of the modal degree. In the initial period, F-ratio of all three parameters of diameter structure model decreased and reached the minimal value in the eighth year, and the predominantly increasing trend started in the twelfth year, which points to the changes in diameter structure of the study clones depending on the age. The plantation growth elements (dg, G) and the Kolmogorov-Smirnov test, as well as the analysis of variance test and LSD test for the percentage of the number of trees with diameters at breast height above 40 cm, confirmed the grouping of diameter structure models of the study poplar clones in two groups. This makes it possible to define the differentiated management procedures with individual groups.Cilj rada je utvrditi pogodnost Weibull-ove distribucije za konstrukciju modela debljinske strukture više klonova topola sekcije Aigeiros (Duby), uz primjenu tzv. “hibridnog sustava” nalaženja parametara modela iz uzorka, pri čemu se za nalaženje nepoznatog parametra lokacije (a) modela koristi više percentila minimalnog promjera u rasponu od 0÷dmin. Također, cilj rada je ispitati promjenu parametara modela u zavisnosti od starosti nasada i klona topole, kao i njihov odnos s elementima rasta nasada (dg, G). Istraživanja su obavljena u pokusnom nasadu starom 20 godina, koji se sastoji od više klonova (sorti) crnih topola sekcije Aigeiros (Duby): S6-36, NS1-3, NS11-8, Pannonia, PE 19/66 i S6-7. Nasad je osnovan na zemljištu tipa fluvisol, pjeskovito-ilovaste forme, pri razmaku sadnje od 5 × 5 m (400 stabala po hektaru), sa sadnicama tipa 2+0. U pokusnom nasadu svaki klon ima četiri reda (ponavljanja) i po 20–25 biljaka u svakom redu. U pokusnom nasadu su periodično mejreni prsni promjeri svih stabala (s točnošću od 1 mm), nakon prve, druge, pete, osme, dvanaeste, sedamnaeste i dvadesete godine od osnivanja. Mjereni prsni promjeri stabala u svakom redu, za svaki istraživani klon i godinu izmjere, predstavljali su uzorak stabala za konstrukciju modela debljinske strukture (ukupno 168 uzoraka). Za svaki uzorak stabala izračunata je temeljni ca, kao zbroj temeljnica svih stabala, te izračunat srednji promjer po temeljnici. Kao model izabrana je Weibull-ova distribucija s tri parametra, čija je funkcija gustoće definirana izrazom (1), a kumulativne distribucije izrazom (2). Za nalaženje nepoznatih parametara Weibull-ove distrbucije korišten je tzv. “hibridni sustav”, odnosno metoda momenata u kombinaciji s metodom percentila (Knoebel, et al, 1986). Parametar položaja (a) dobiven je po metodi percentila, pri čemu su korišteni sljedeći percentili minimalnog promjera: 0,00; 0,01; 0,05; 0,10; 0,15; 0,20; 0,25; 0,30; 0,35; 0,40; 0,45; 0,50; 0,55; 0,60; 0,65; 0,70; 0,75; 0,80; 0,85; 0,90; 0,95; 0,99; 1,00. Parametri skaliranja (b)i oblika (c) dobiveni su po metodi momenata, pri čemu je za njihovo nalaženje izvršeno oduzimanje mjerenih veličina (prsnih promjera) od prethodno definiranog parametra “a”. Ova metoda zasniva se na jednadžbama prvog (x-) i drugog (x–2) običnog momenta Weibull-ove dvoparametarske distribucije (5, 6). Procijenjena varijanca (s2) Weibull-ove distribucije definirana je izrazom (7), a koeficijent varijacije (cv) izrazom (8). Nalaženjem prvog i drugog običnog momenta, kao i koeficijenta varijacije iz uzorka i stavljanjem u formulu 8, koeficijent varijacije je funkcija samo jednog parametra (c), te se može dobiti postupkom iteracije. U radu je korištena kombinacija metode sekante i metode polovljenja intervala uz unaprijed zadanu točnost od 10-6(Conte i de Boor, 1973). Dobivena veličina parametra „c“ poslužila je da se dobije veličina parametra “b” iz relacije (9). Za svaki od navedenih percentila u svakom ponavljanju dobiven je parametar „a“ modela, a metodom momenata parametri “b” i “c”. Zatim je izvršena usporedba empirijske debljinske strukture i modela primjenom Anderson-Darling statistike (A2) (Anderson i Darling, 1954) po formuli (10). Izbor percentila minimalnog promjera izvršen je na temelju minimalne veličine A2statistike za sva 4 ponavljanja u okviru istog klona i starosti nasada. Za svaki od izabranih percentila minimalnog promjera u okviru svakog klona i starosti nasada izvršeno je ponovno nalaženje sva tri parametra Weibull-ove distribucije za svako ponavljanje. Stupanj slaganja modela debljinske strukture i empirijske distribucije izvršen je neparametarskim testom Kolmogorov-Smirnova, nalaženjem |D| statistike (11). Dobiveni parametri Weibull-ove distribucije po pojedinim ponavljanjima korišteni su za utvrđivanje razlika između istraživanih klonova u pojedinim starostima (godina nakon sadnje), pri čemu je korišten statistički test analize varijance i test najmanje značajne razlike (NZR), na razini rizika od 5 %. Istraživani klonovi ostvarili su značajne razlike u elementima rasta (dg, G) na kraju istraživanog razdoblja od 20 godina, što pruža osnovu za njihovo proizvodno diferenciranje. Na osnovi periodičnih izmjera prsnih promjera utvrđen je različit rast istraživanih klonova u debljinu, u zavisnosti od starosti: u početnom razdoblju razvoja klonovi Populus deltoides Bartr. ex Marsh. (S6-7, NS1-3, PE 19/66, NS11-8, S6-36) rastu intenzivnije od klona Pannonia (Populus × euramericana (Dode) Guinier), a kasnije klon Pannonia ima intenzivniji rast, dok između klonova P. deltoides Bartr. ex Marsh. dolazi do međusobnog diferenciranja. Tijekom cijelog razdoblja od 20 godina klon PE 19/66 ostvario je najveće veličine, kako srednjeg promjera po temeljnici (dg), tako i ukupne temeljnice po hektaru (G) i izdvaja se od ostalih klonova po testu NZR na razini rizika od 5 % (tablice 1, 2, grafikon 1). Model Weibull-ove distribucije pokazao se pogodnim za modeliranje debljinske strukture istraživanih klonova topola u različitim starostima nasada, a primijenjena metoda nalaženja parametra položaja (a) modela Weibull-ove distribucije pokazala je da se u 93,1 % istaživanog uzorka parametar „a“ nalazi o rasponu od 50–90 %, a u 54,2 % u rasponu od 80–90 % minimalnog promjera uzorka (grafikon 2). Usporedbom modela kumulativne distribucije i empirijske kumulativne distribucije neparametarskim testom Kolmogorov-Smirnova, povrđena je sličnost kod svih 168 uzoraka. Uz male oscilacije s povećanjem starosti nasada povećavaju se parametri položaja (a) i skaliranja (b), što je potvrđeno koeficijentom korelacije od 0,71 i 0,73 (grafikon 3). Tose manifestira u pomicanju krivulje modela debljinske strukture udesno k većim promjerima i u širem rasponu prsnih promjera s manjom relativnom frekvencijom modalnog stupnja (grafikon 4). Promjene parametra oblika raspodjele (c) manje su izražene, što potvrđuje iznos koeficijenta korelacije od 0,36 (grafikon 3). Međutim, njegovo značenje na razini rizika od 0.001 ukazuje na trend povećanja sa starošću nasada, odnosno na promjenu oblika debljinske strukture. U početnom razdoblju koda sva tri parametra modela debljinske strukture po Weibull-u F-količnik ima trend opadanja i dostizanja minimalne vrijednosti u osmoj godini, a u dvanaestoj godini pokazuje porast, odnosno pretežito trend povećanja, što ukazuje na promjene u debljinskoj strukturi istraživanih klonova u zavisnosti od starosti. Konstruirani modeli debljinske strukture istraživanih klonova topola pokazuju grupiranje klonova u dvije grupe, što je potvrđeno neparametarskim testom Kolmogorov-Smirnova, kao i testom analize varijance i testom NZR za učešće broja stabala prsnih promjera debljih od 40 cm, te ukazuje na mogućnost i potrebu njihovog grupiranja pri definiranju odgovarajućih gospodarskih postupaka

Utjecaj jakih prorjeda na prirast i stabilnost stabala i sastojine smreke u starosti od 32. do 50. godine

The paper studies effects of two heavy thinnings on the increment and slenderness of various categories of trees and stability of the stand as a whole. The research was conducted on a permanent experimental plot in an Norway spruce (Picea abies /L./ Karst.) monoculture in Serbia. This monoculture was established with 5,000 seedlings per hectare on the site of mountain beech forest and the effects of heavy thinnings were investigated in the 33-40 and 41-50 age periods.To determine the thinning effects we compared current diameter increments (idt) and current height increments (iht) of dominant trees (D100 and D400) obtained by a detailed analysis of trees and of mean stand dominant trees (D100 and D400). At the stand level, we compared the current diameter (id), basal area (IG) and volume (IV) increments of all trees and of the same collective of aspirants in two periods after the thinnings, between the ages of 33 and 40, and between the ages of 41 and 50.The first thinning was carried out at the age of 32 when the dominant trees were 15 m tall and the next at the age of 40 when the dominant trees were above 20 m in height. They were both low (qd <0.85) and heavy selective thinnings (34-36% of the volume). A more significant increase in the diameter increment was recorded after the second thinning between the ages of 41 and 50. It amounted to 29.1% in aspirants and 36-42% in dominant trees (D100 and D400) compared to the period after the first thinning, i.e., between the ages of 33 and 40. The thinnings further contributed to the establishment of more favorable relations in diameter and height increments of the trees in the studied culture and thus improved their stability.Istraživanja su obavljena u kulturi smreke (Picea abies /L./ Karst.), koja je osnovana sa 5.000 sadnica po hektaru na staništu planinske šume bukve na nadmorskoj visini 870 m. Na osnovi usporedbe elemenata rasta istraživane kulture s elementima rasta u drugim mladim do srednjedobnim kulturama smreke, istraživana kultura je u kategoriji visokoproizvodnih kultura u Srbiji i šire u Europi.Na trajnoj pokusnoj plohi, u dobro sklopljenom dijelu istraživane smrekove kulture u starosti 32 godine, izmjereno je 3.911 stabala po hektaru, s volumenom od 384,17 m3·ha-1, a ukupno evidentiran prirast drvne zalihe sastojine do 40. godine iznosio je 561,85 m3·ha-1, a do 50. godine 819,1 m3·ha-1. Na osnovi dvije prorjede, u 32. i 40. godini i naknadno posječenih tanjih stabala u razdoblju od 33. do 40. god., na pokusnoj plohi ukupno je posječeno 2.844 stabla po hektaru (72,7%) volumena 279,4 m3·ha-1 (tablica 1). Numerički pokazatelji strukture stabala na pokusnoj plohi u 32., 40. i 50. godini prikazani su u tablici 2, a debljinska struktura na grafikonima 2, 3 i 4.Za definiranje utjecaja prorjeda na prirast stabala uspoređen je tečajni debljinski (idt) i visinski (iht) prirast u razdoblju od 25. do 32. godine i 33.-40. godine kod detaljno analiziranih dominantnih stabala (D100 i D400), a na sastojinskoj razini uspoređen je tečajni debljinski (idt) i visinski (iht) prirast u razdoblju od 33. do 40. godine i 41.do 50. godine kod dominantnih stabala (D100 i D400). Testiranje razlika između tečajnih prirasta u različitim razdobljima obavljeno je uz pomoć t-testa. Na razini sastojine uspoređen je i tečajni prirast promjera, temeljnice i volumena svih stabala i stabala budućnosti (311 kom.∙ha-1) u razdoblju od 33.-40. godine i u razdoblju od 41.-50. godine. Neparametrijski Kolmogorov-Smirnov test korišten je za međusobnu usporedbu struktura stupnja vitkosti (odnos h/d1,3). Istraživanja su omogućila da se definira utjecaj prorjeda na prirast i stupanj vitkosti različitih kategorija stabla i sastojine u dva starosna razdoblja sastojine, 33.-40. i 41.-50. godine. Prva prorjeda u 32. godini, pri visini dominantnih stabala 15 m, imala je karakter selektivne prorjede, bila je niska (qd<0,85) i jaka (jačina prorjede je 36% volumena). Prorjeda je obavljena u starosti sastojine koja značajnije ne odstupa od razdoblja kada se izvode prve „komercijalne“ prorjede u Europi. Međutim, tokovi tečajnog debljinskog prirasta detaljno analiziranih dominantnih stabala (D100 i D400)  pokazali su da je prekasno izvršiti prorjedu u 32. godini, a model rasta (prirasta) visina је pokazao kulminaciju u 25. godini (kada su dominantna stabla postigla visinu 11 m), pa bi se 25. godina mogla označiti i kao godina u kojoj je najkasnije trebalo izvršiti prvu komercijalnu prorjedu (grafikon 7). Zatečeni velik broj stabala, s velikom drvnom zalihom po hektaru, u 32. godini i jaka prorjeda uvjetovali su  visoki iznos prorjednog etata, od 115,13 m3∙ha-1, što je u kategoriji najviših iznosa volumena koji se okvirno preporučuju u literaturi za sličnu starost smrekovih kultura. U razdoblju od 33.-40 godine debljinski prirast je iznosio kod preostalih stabala 0,31 cm∙god-1, a kod stabala budućnosti 0,54 cm∙god.-1 (tablica 7). Dominantna stabla, posebno 400 najdebljih stabala po hektaru, nalazila su se u fazi velikog visinskog prirasta u vrijeme i poslije prorjede u 32. godini (tablica 5 i 6), što je za posljedicu imalo povećanje stupnja vitkosti stabala, odnosno povećanje nestabilnosti sastojine (grafikon 8). Druga prorjeda u 40. godini, pri visini dominantnih stabala preko 20 m, imala je karakter selektivne prorjede, bila je niska (qd<0,85) i jaka (jačina prorjede je 34% volumena). Jaka prorjeda u 40. godini, s prorjednim etatom 142,28 m3∙ha-1, uvjetovala je veći debljinski prirast, odnosno bolju reakciju debljinskog prirasta na preostalim stablima, u odnosu na prorjedu u 32. godini. Stabla budućnosti imali su za 29%, a dominantna stabala (D100 i D400) za 36-42%, veći debljinski prirast u starosnom razdoblju od 41.-50. godine, u odnosu na starosno razdoblje 33.-40. godine, što je uz opadajući trend visinskog prirasta uvjetovalo i manji stupanj vitkosti, odnosno veću stabilnost stabala i sastojine (grafikon 8).Na osnovi navedenog, proizlazi da su provedene jake prorjede doprinijele uspostavljanju povoljnih odnosa u debljinskom i visinskom rastu stabala u istraživanoj kulturi i time poboljšale njihovu stabilnost

Rast i struktura linijskog zasada talijanske johe (Alnus cordata /Loisel./ Duby) u dobi 11 i 16 godina na Fruškoj gori (Srbija)

Growth and structure of Italian alder (Alnus cordata /Loisel/ Duby) trees were analyzed in a linear plantation established by planting two-year-old seedlings at Fruška Gora (Serbia). The aim of this paper is to point out the growth characteristics and the structure of the Italian alder linear plantation at age 11 and 16 years and contribute to the knowledge of adaptive and productive potential of the species in the available plantation in Serbia.The spacing between the trees was 7 m (200 trees per hectare). The plantation is located on anthropogenically changed pedunculate oak and hornbeam site at 125 m above sea level. On the basis of 35 measured trees at age 11 and 16 years, the top height was 15 and 21 m, and the Lorey’s mean height 13.4 and 19.5 m. The dominant diameter was 32.4 cm at age 11 and 59.4 cm at age 16 years. The mean quadratic diameter was 25.1 and 47 cm.The productivity of the plantation is high. At age 11 years, the basal area was 9.9 m2∙ha−1, and the standing volume 107.2 m3∙ha−1 while at age 16 years, it was 34.7 m2∙ha−1 and 305.1 m3∙ha−1, respectively. In the period from 11 to 16 years of age, the periodic annual increment in diameter was 4.4 cm∙year−1, height 1.22 m∙year−1, and in basal area and volume 4.9 m2∙ha−1·year−1and 39.6 m3·ha−1·year−1, respectively, pointing to fast growth of Italian alder.Despite the limits due to a small sample and the fact that the linear plantation was analyzed, we generalise the ­following conclusion: the measured growth characteristics at age 11 and 16 years of Italian alder trees show that the species can grow fast and could be usable in similar areas.Analizirani su rast i struktura linijskog zasada talijanske johe (Alnus cordata /Loisel/ Duby) na Fruškoj gori (Srbija). Cilj ovoga rada je da ukaže na elemente rasta i strukturu linijskog zasada talijanske johe u starosti 11 i 16 godina, i time doprinese upoznavanju adaptivnog i proizvodnog potencijala ove vrste u raspoloživom zasadu u Srbiji.Zasad je osnovan dvogodišnjim sadnicama s međusobnim razmakom 7 m, odnosno sa 200 stabala po hektaru, na antropogeno izmijenjenom staništu lužnjaka i graba, na nadmorskoj visini 125 m. Na temelju usporednog dendrometrijskog premjera 35 stabala u dobi 11 i 16 godina, dominantna visina iznosila je 15 i 21 m, a srednja visina po Loraju 13,4 i 19,5 m. Dominantni promjer iznosio je 32,4 cm u 11. godini, a 59,4 cm u 16. godini, dok je srednji promjer iznosio 25,1 cm i 47 cm. Na temelju izračuna da se po hektaru nalazi 200 stabala u 11. godini temeljnica je iznosila blizu 10 m2∙ha−1, a volumen preko 100 m3∙ha−1, a u 16. godini temeljnica je iznosila blizu 35 m2∙ha−1, a volumen preko 300 m3∙ha−1 (Tablica 1). Debljinska struktura stabala u zasadu je unimodalna u obje životne dobi (Tablica 2, Slika 1), a visinska struktura iskazana grupiranjem visina u stupnjeve širine 3 m, ima opadajući oblik u 11. godini i zvonasti unimodalni oblik u 16. godini (Tablica 3, Slika 2). Parametri modela ovisnosti visina stabala o njihovim početnim prsnim promjerima i značajke njegove ocjene ukazuju da se u dobi 11 godina 55% varijabilnosti visina može pripisati njihovim prsnim promjerima, dok je u dobi 16 godina ovisnost manje izražena (Tablica 3, Slika 3). Stupanj vitkosti opada sa starošću. U dobi 11 godina stupanj vitkosti je bio u rasponu 38–79, prosječno 54, a u dobi 16 godina u rasponu je 31–64, prosječno 43 (Tablica 4, Slika 4). U razdoblju od 11. do 16. godine tečajni prirast promjera iznosio je 4,4 cm∙god−1, visine 1,22 m∙god−1, a temeljnice i volumena po hektaru 4,9 m2∙ha−1·god−1 i 39,6 m3·ha−1·god−1 (Tablica 6). Oblik raspodjele tečajnog prirasta prsnih promjera, temeljnice i volumena stabala je sličan, sa slabo izraženom desnom asimetrijom i platikurtičnim rasporedom, a tečajni prirast visina stabala karakterizira izražena lijeva asimetrija i neizražen platikurtični raspored. U razdoblju 11.–16. godine stupanj vitkosti se prosječno smanjuje za veličinu 2,25 godišnje, uz raspon od 0,68–4,10 (Tablica 7). Zavisnost tečajnih prirasta promjera, temeljnice i volumena o njihovim početnim veličinama u 11. godini dobro opisuje linearni model, gdje se 50–70% varijabliteta može pripisati njihovim početnim veličinama. Tečajni prirast visina nije uvjetovan njihovim visinama u dobi 11 godina. Međutim, promjena stupnja vitkosti u razdoblju 11–16 godina ima jasno izražen negativan linearan trend, odnosno stabla s većim stupnjem vitkosti u dobi 11 godina također su imala i veći pad (Tablica 8). Uz sva ograničenja za generalizaciju zaključaka zbog malog uzorka stabala i linijskog zasada značajke rasta u 11. i 16. godini dobi ukazuju da talijanska joha ima karakteristike brzog rasta i može predstavljati potencijalno primjenjivu vrstu u sličnim područjima

Effects of heavy thinning on Turkey oak (Quercus cerris L.) tree and stand increment

Na trajnim pokusnim plohama u umjetno podignutoj, srednjedobnoj, sastojini cera analizirani su efekti jake prorede na prirast stabala i sastojine, 5 i 10 godina od izvođenja. U 56. godini na pokusnoj plohi 1 (jaka proreda) prirašćivalo je 62% stabala, a na plohi 2 (sanitarna sječa) prirašćivalo je 95% stabala u odnosu na početno stanje u 46. godini. Pet godina poslije jake prorede na O.P.-1 tekući prirast temeljnice po hektaru iznosio je 89%, a zapremine 88%, u odnosu na (O.P.-2). U narednom petogodišnjem periodu tekući prirast temeljnice istih stabala na O.P.-1 iznosio je 95 %, a zapremine 92 %, u odnosu na O.P.-2. U cjelokupnom promatranom periodu tekući prirast temeljnice i zapremine preostalih stabala po hektaru na O.P.-1 iznosio je 92 %, odnosno 90 %, u odnosu na O.P.-2. Tekući prirast promjera, temeljnice i zapremine po stablu na O.P.-1. u prvom petogodišnjem periodu bio je veći za 21-22%, u drugom petogodišnjem periodu bio je veći za 26-30%, a u cjelokupnom promatranom periodu bio je veći za 23-25%, u odnosu na O.P.-2. Posle 10 godina na O.P.-1 srednji promjer preostalih stabala povećan je za 16,1%, temeljnica za 34,7%, a zapremina za 50,8%. Za isti period na O.P.-2 srednji promjer preostalih stabala povećan je za 13,2%, temeljnica za 28,4%, a zapremina za 40,4%. Zaključak je kako je jaka proreda povoljno utjecala na povećanje prirasta preostalih stabala. Ukupna produkcija na pokusnim plohama u 56. godini, pored isključivanja 38 % stabala iz proizvodnje na O.P.-1, približno je identična i održan je uspostavljeni rang (sa manjom razlikom) u veličini ukupne produkcije između oglednih ploha pre jake prorede.On permanent sample plots in middle-aged, artificially established, Turkey oak stand, the effects of heavy thinning (S.P.-1) and sanitation cutting (S.P.-2) were analysed on trees and stand increment, 5 and 10 years after cutting at the age of 46 years. Till the age of 56 years, 62% trees incremented on S.P.-1, and 95% trees on S.P.-2, compared to the initial state at the age of 46 years. Due to the devitalisation in the previous period, the remaining trees had the reduced capacity of growth reaction to the spatial increase and they compensated the increment loss slowly, which resulted due to the reduction of a great number of trees (38%) and volume (31%) on S.P.-1. Five years after heavy thinning on S.P.-1 the compensated volume was 57.4 % compared to the state before thinning, and after 10 years, the volume increased by 10% compared to the state before thinning. Compared to the volume per ha on S.P.-2 at the age of 56 years, the volume on S.P.-1 was lower by 20.6%. However, total production on sample plots at the age of 56 years, regardless of the elimination of 38% trees on S.P.-1, was approximately identical, and the established rank was maintained (with minor differences) in the size of the total production between the sample plots before the heavy thinning. Five years after heavy thinning on S.P.-1, current increment of basal area per ha was 89 %, and volume 88 %, compared to S.P.-2. In the following five-year period, current increment of basal area per ha of the same trees on S.P.-1 was 95%, and volume 92%, compared to S.P.-2. Throughout the study period, current increment of basal area and volume of the remaining trees per ha on S.P.-1 was 92% and 90%, compared to S.P.-2., as the consequence, primarily, of the different number of trees which incremented on sample plots. Current increment of diameter, basal area and volume per tree on S.P.-1. during the first five-year period was higher by 21-22%, during the second five-year period it was higher by 26-30%, and in the entire study period, it was higher by was 23-25%, compared to S.P.-2, and it is the consequence, primarily, of the different intensity of increment of the remaining trees on sample plots. In both five-year periods, the trees on S.P.-1 had greater diameter increment compared to the trees on S.P.-2 in all diameter degrees. After 10 years, on S.P.-1, mean diameter of the remaining trees increased by 16.1%, basal area by 34.7%, and volume by 50.8%. During the same period on S.P.-2 mean diameter of the remaining trees increased by 13.2%, basal area by 28.4%, and volume by 40.4%, so it can be concluded that heavy thinning had a favourable effect on the increase of increment of the remaining trees during the study period

GROWTH CHARACTERISTICS OF SOME BLACK POPLAR CLONES

U poljskom pokusu osnovanom pri gustoći od 400 stabala·ha-1 u zaštićenom dijelu vlažnog zemljišta, tipa fluvisol, srednjeg Podunavlja, pjeskovito-ilovaste forme, istraživane su karakteristike rasta tri klona (sorte) crnih topola: "PE 19/66", "S6-7" i "M-1" starosti 11 godina. Karakteristike rasta promjera, visine i volumena srednjih stabala ukazuju na značaj izbora klona (sorte) crnih topola pri osnivanju nasada za razlčite namjene: klonovi "PE 19/66" i "S6-7" (Populus deltoides Bartr.) u istraživanim uvjetima staništa i gustoće postižu kulminaciju prosječnog prirasta volumena u starosti od 11 godina, pri čemu se postiže drvna masa od 220-290 m3·ha-1 namijenjenog za kombiniranu proizvodnju tehničkog i celuloznog drveta. Sorta "M1" (Populus × euramericana (Dode) Guinier) za 11 godina postiže kulminaciju tekućeg prirasta volumena te se procjenjuje znatno duži proizvodni ciklus i kvalitetnija struktura dobijenih sortimenata.Growth characteristics of three black poplar clones, PE 19/66, S6-7, and M-1, were investigated in the field experiment established at plant distance of 5m x 5m in the protected area of central Danube basin, on the fluvisol of sandy-clayey form, after ten years of culture development. The characteristics of diameter, height and volume growth of medium trees show significant differences among the investigated black poplar clones. The research clearly highlights the significance of the clone (species) of black poplar at establishing the plantation for different purposes: clones PE 19/66 and S6-7, (Populus deltoides Bartr.) under the research conditions of the habitat and planting distance reach the culmination of average volume increment 11 years since the beginning of planting, reaching a wood volume of 220-290 m3·ha-1 for the purposes of combined production of technical and pulp timber. Clone M-1, a hybrid of domestic and American black poplar (Populus x euramericana (Dode) Guinier), demonstrates different growth properties, while the culmination of average volume increment at age 15 since the planting is estimated to have a considerably better assortment structure

Growth dynamics of crown shapes in stands of pedunculate oak and common hornbeam

Background and Purpose: Structure of crowns in forest stands is one of the main factors which determines growth and development of trees. Dynamic change occurs with the age of the stand due to silvicultural interventions or natural disturbances duringwhich trees are removed fromthe stand. The aim of this article is to analyse the structure of the crown shape of pedunculate oak and common hornbean trees with regard to diameter at breast height (DBH) and the age of the stand in one of the most important forest community in Croatia. Materials andMethods: The investigation is based on data collected on 47 permanent experimental plotswhichwere established as a chronosequence in a natural range of forests of pedunculate oak and common hornbeam in Croatia. The total surface of all plots amounts to 33.45 ha. Breast height diameter, tree height and stem height were measured on the trees in the experimental plots, and a detailed ground plan was made of horizontal crown projections, from which the crown diameters were calculated. In total 1505 pedunculate oak trees and 2026 common hornbeam trees were measured. For each tree the crown shape was calculated and trees were then grouped in age classes of 20 years, and the shape of the crown analysed according to species and age classes. Correlation between crown shapes and diameter at breast height was investigated for stands of the sixth age class (101 – 120 years) for each species by means of linear regression. Results and Discussion: The shape of the crown of pedunculate oak, although it shows a trend toward growth in relation to diameter at breast height, the regularity pattern of the shape indicates weak character (r=0.441), i.e. variability is explained with only 19%. Crown shapes of common hornbeam are almost constant in relation to diameter at breast height (r=114), and correlation between the examined values cannot be equated by any rational analytical term. Investigation of growth dynamics of crown shape structure was carried out according to the species of trees and age classes, and the interval inwhich 68%(x ± 1.0 s) and 95%of data (x ± 1.96 s)were included. Conclusions: The results of the investigation indicate that dependence on crown shape and diameter at breast height of pendunculate oak and common hornbeam cannot be described by any rational analytical term. Average values of the crown shapes according to age classes can be used as form factors for calculation of crown volume.Data are applicable in various applications, such as for example their integration in a simulator of growth and development of forest stands and examination of the effect of different silvicultural scenario

Growth dynamics of crown shapes in stands of pedunculate oak and common hornbeam

Background and Purpose: Structure of crowns in forest stands is one of the main factors which determines growth and development of trees. Dynamic change occurs with the age of the stand due to silvicultural interventions or natural disturbances duringwhich trees are removed fromthe stand. The aim of this article is to analyse the structure of the crown shape of pedunculate oak and common hornbean trees with regard to diameter at breast height (DBH) and the age of the stand in one of the most important forest community in Croatia. Materials andMethods: The investigation is based on data collected on 47 permanent experimental plotswhichwere established as a chronosequence in a natural range of forests of pedunculate oak and common hornbeam in Croatia. The total surface of all plots amounts to 33.45 ha. Breast height diameter, tree height and stem height were measured on the trees in the experimental plots, and a detailed ground plan was made of horizontal crown projections, from which the crown diameters were calculated. In total 1505 pedunculate oak trees and 2026 common hornbeam trees were measured. For each tree the crown shape was calculated and trees were then grouped in age classes of 20 years, and the shape of the crown analysed according to species and age classes. Correlation between crown shapes and diameter at breast height was investigated for stands of the sixth age class (101 – 120 years) for each species by means of linear regression. Results and Discussion: The shape of the crown of pedunculate oak, although it shows a trend toward growth in relation to diameter at breast height, the regularity pattern of the shape indicates weak character (r=0.441), i.e. variability is explained with only 19%. Crown shapes of common hornbeam are almost constant in relation to diameter at breast height (r=114), and correlation between the examined values cannot be equated by any rational analytical term. Investigation of growth dynamics of crown shape structure was carried out according to the species of trees and age classes, and the interval inwhich 68%(x ± 1.0 s) and 95%of data (x ± 1.96 s)were included. Conclusions: The results of the investigation indicate that dependence on crown shape and diameter at breast height of pendunculate oak and common hornbeam cannot be described by any rational analytical term. Average values of the crown shapes according to age classes can be used as form factors for calculation of crown volume.Data are applicable in various applications, such as for example their integration in a simulator of growth and development of forest stands and examination of the effect of different silvicultural scenario

Effects of two different thinning methods on the diameter and basal area increments of silver lime (Tilia tomentosa Moench) target trees in Fruška Gora (Serbia)

This paper analyses the cumulative effects of selective thinning and thinning from below on diameter and basal area increments of target trees after 25/26 years in 52, 69- and 86-year-old silver lime (Tilia tomentosa Moench) stands. Two target tree collectives were analysed: (1) elite trees selected between 1993–1994 from permanent sampling plots (selective thinning method), and (2) a ‘comparable collective’ of target trees selected in 2019 (25/26 years later) according to the same criteria as the elite trees, in the same stands thinned from below. Elite trees that were selectively thinned had: higher diameter, basal area and volume per tree, higher diameter and basal area increment for a given time period, and lower slenderness coefficients compared to the target trees that were thinned from below at 52 and 69 yr. While diameter increment decreases with age, and differences between elite trees of different ages are clearly delineated, diameter increments of trees thinned from below are not significantly different at 52 and 69 yr. In addition, basal area increment of trees is highest at 69 yr with selective thinning. When thinning from below, there were no significant differences in basal area increments between trees at 69 and 86 yr. Silver lime shows a strong growth response after selective thinning at ages 25/26 and 44 yr. However, our results show that this response is less pronounced when selective thinning begins at 61 yr

Effects of Silvicultural Measures in Devitalized Middle Aged Oak Stand (Quercus Robur L.) on Chernozem in Vojvodina

Na dvije trajne pokusne površine (P.P.-1 i P.P.-2) u jednoj sred nje dobnoj lužnjakovoj monokulturi, analizirani su učinci različitih uzgojnih mjera, koje su poduzimane u svrhu njege sastojine i saniranja posljedica devi talizacije stabala. Proces devitalizacije utvrđen je u 42. godini starosti sastojine i manifestirao se u koincidenciji nepovoljnog sastojinskog stanja i nepovoljnih egzogenih utjecaja. Na P.P.-1 u 42. i 48. godini provedena je uzgojno-sanitar na sječa umjerenog i jakog zahvata, a na P.P.-2 uklanjana su suha stabla. Za defi niranje učinaka različitih uzgojnih mjera u starosnom razdoblju od 43–52. go-di ne, korišten je tečajni (prosječni periodički) debljinski prirast (id), svih preostalih stabala i stabala budućnosti. Na P.P.-1 srednja veličina te čajnog debljinskog prirasta svih stabala veća je za 37 %, a stabala budućno sti za 35 %, u odnosu na P.P.-2. Ovisnost debljinskog prirasta od prsnih pro mjera kod svih stabala pokazuje srednje jaku korelaciju (R = 0,52–0,54), a za grupu stabala budućnosti korelacija je slabije izražena (R = 0,28–0,32).Past experience has shown that the application of silcivultural measures to pedunculate oak stands of lessened functional capacity is met with severe restrictions for the achievement of the desired results and goals. This work analyzes the effects of different silci vultural measures in comparative permanent sample plots (P.P. -1 and P.P. -2), undertaken with the purpose of tending the stands and improving the consequences of devitalisation. Research was undertaken in an artificially established monoculture of pedunculate oak in Vojvodina (.n=45° 49’, .e=18° 39’). The altitude is 88 m, and the soil is chernozem non-carbonate, with the depth of the humus accumulative horizon of about 40–50 cm. Mean annual air temperature is 10.9 °C, and mean annual rainfall is 584 mm. During the dormant vegetation season, two cross-section diameters were measured with an accuracy of 1 mm on all trees aged 42 and 52. All the marked trees were also measured when they reached the age of 48. A silvicultural-salvage cut of moderate to heavy intensity was performed in P.P. 1 at the age of 42 and 48. A total of 128 future trees (FT) per hectare were selected in P.P.-1 at tree age 42. At the age of 52, the status was retained by 124 trees. The primary measure in P.P.-1 involved removing the strongest competition against future trees from the stand, so the treatment also had the character of selective thinning. Using similar silvicultural prin ciples, 156 dominant trees aged 42 were selected for comparison in P.P.-2. Of these, 148 trees retained the status of future trees at age 52, while P.P.-2 was left to natural tree se lection. During measurements in the year 42, a crown class (CC) and the degree of crown freedom position (CF) was determined for each tree. To assess crown damage intensity (defoliation), classification with degrees 0–4 was used. Data processing consisted of determining the numerical parameters of diameter struc ture, while the non-parametric Kolmogorov-Smirnov test (|D| statistics) was used to com pare diameter distribution with the distribution of diameter increment. The .2test for independence was used to define dependence of the degree of crown freedom position and the degree of crown defoliation, as well as the crown class and the degree of crown defo liation in sample plots at stand age 42. The effects of different stand treatments were ana lyzed in the age period 43–52. The current (average periodical) diameter increments (id) obtained with the control method was compared for all the trees in the sample plots and separately for the future trees in P.P.-1, and the comparison trees in P.P.-2. The statistical t-test was used to assess the impact of silvicultural treatments on the increment size. Growth elements of all the trees and future trees in the sample plots at age 42 and 52, as well as the trees cut at ages 42 and 48, are given in Table 1. Table 2 contains numerical indicators of their diameter distribution. Cumulative curves of diameter distribution of all the trees show that at age 42 the trees in P.P.-2 have a somewhat bigger breast diameter. Due to differential silvicultural treatments and different increment tree reactions, diame ter distribution of all the trees and future trees were approximated at age 52, which was also confirmed by the Kolmogorov-Smirnov test (Graph 1, Table 2). Based on the test for independence applied at age 42, high dependence was found in the monoculture of the degree of crown defoliation on the crown class and the degree of crown freedom position. This indicates that the devitalization process in directly linked with stand structure, i.e. silvicultural treatments in the previous period (Table 3 and 4, Figure 1). The Kolmogorov-Smirnov test confirmed the difference in diameter distribution of selec ted trees in the sample plots in the 42ndand 48thyear (Graph 2, Table 2). The thinning indi cator (qd) shows that tree selection in the sample plots had the character of low thinning. In the age period between 43 and 52, a more intensive treatment of silvicultural-sanitary cuts (P.P.-1) showed that the current diameter increment was on average higher by 37 % in all the other trees and by 35 % in future trees, in relation to the sanitary cut (Graph 3). Cumu lative curves of diameter increment in P.P.-1, for all the trees and for future trees, are shifted rightwards towards higher increment values, in relation to P.P.-2. There are also differences in the shape of the curve, which implies a difference in the variability of diameter increment (Graph 4). The Kolmogorov-Smirnov test confirmed considerable differences in the distri bution of diameter increment, both for the entire group of trees and for future trees (Table 5). Dependence of diameter increment on diameters at breast height (Graph 5 and Table 6) in all the trees shows moderate correlation ((R = 0.52-0.54), whereas correlation is less dis tinct (R = 0.28-0.32) for the collective of futures. For all the remaining trees, the impor tance of a regression coefficient of diameter increment dependence on diameters at breast height confirms that at this developmental stage the recovery from stressful impacts de pends on the intensity and character of silvicultural measures and on the tree´s increment potential. For the collective of future trees in P.P.-1 (and potentially for the group of domi nant comparison trees in P.P.-2), which are the first object of tending, recovery from adverse impacts primarily depends on the nature and intensity of silvicultural measures