Klimatski signali u kronologijama ranog drva, kasnog drva i širini goda hrasta kitnjaka (Quercus petraea (Matt.) Liebl.) iz Majdanpeka, sjeveroistočna Srbija

In this article, the dependence of the sessile oak (Quercus petraea (Matt.) Liebl.) radial growth (tree-ring, earlywood, and latewood widths) on climate (the mean monthly temperature and precipitation totals) was studied in the Majdanpek area, north-eastern Serbia. The growth response of the oak trees to the prevailing climate conditions was dendroecologically investigated, by applying the correlation and response function, as well as by pointer years analysis. The site chronology covered 159 years (1855-2013). We found that latewood and total tree-ring width contain the imprinted positive response to the amount of precipitation in summer months (June and July) of the current growing season. The earlywood width showed no direct dependence on climate data, but it was significantly affected by the previous-year latewood width. Moreover, 40 % of the variation in the latewood width is explained by the earlywood variation in the same season. The temperature was not found to have any significant effect on the growth of oak at the study site. The use of pointer years, determined by applying several calculation procedures, has highlighted previous results, indicating that the precipitation in summer months was the deciding climate factor leading to the occurrence of the years with exceptionally wide or narrow tree-rings and latewood. To enhance our understanding of the response of the sessile oak growth at south-oriented sites with a shallow soil profile to precipitation and temperature variations, and expand the current database and knowledge, future studies should be undertaken.U radu je proučavana ovisnost radijalnog prirasta (širine goda, širine ranoga i kasnog drva) hrasta kitnjaka (Quercus petraea (Matt.) Liebl.) o klimi (srednjoj mjesečnoj temperaturi i količini oborina) na području Majdanpeka, u sjeveroistočnoj Srbiji. Odziv radijalnog rasta hrastovih stabala na prevladavajuće klimatske uvjete istražen je dendrokronološki, primjenom korelacijske i odzivne funkcije, kao i analizom pokaznih godina. Kronologija staništa obuhvatila je 159 godina (1855. – 2013.). Otkrili smo da kasno drvo i ukupna širina goda sadržavaju utisnut pozitivan odziv na količinu oborina u ljetnim mjesecima (lipnju i srpnju) tekuće sezone rasta. Širina ranog drva nije pokazala izravnu ovisnost s klimatskim uvjetima, ali je na nju značajno utjecala širina kasnog drva iz prethodne godine. Nadalje, 40 % varijacija širine kasnog drva objašnjava se varijacijama ranog drva iz iste sezone. Na istraživanom staništu nije utvrđeno da temperatura ima značajan utjecaj na rast hrasta. Primjena pokaznih godina, koje su određene primjenom nekoliko računskih postupaka, potvrdila je prethodne rezultate upućujući na to da je prevladavajući klimatski čimbenik koji je doveo do pojave izrazito širokih ili uskih godova i kasnoga drva u pojedinim godinama bila količina oborina u ljetnim mjesecima. Da bi se sveobuhvatno razumjela reakcija rasta hrasta kitnjaka na promjene temperature i količinu oborina na južnim ekspozicijama i s plitkim profilom tla, trebalo bi provesti dodatne studije kako bi se proširila baza podataka i spoznaja

First Dendroclimatological Insight into Austrian Pine (Pinus nigra Arnold) Climate-Growth Relationship in Belgrade Area, Serbia

In order to assess the impact of climate variations on Austrian pine forest in the Belgrade area, the radial growth of artificially-established Austrian pine trees and its dependence on temperature and precipitation was studied using dendroclimatological methods. The site is classified as Quercetum-frainetto cerris Rudski. Standard and residual chronologies were established and several common statistics were calculated. A dendroclimatic study was carried out using the correlation and response function analysis. The Pearson correlation coefficients between the chronology indices and 13 seasonal (3-month period) precipitation and temperature data were calculated for the period from 1959 to 2014. The applied response function analysis included 24 precipitation and temperature variables from October of the prior year to September of the current year. The results of the correlation analysis pointed out that there was a strong tendency towards a positive response to the summer and late summer/early autumn precipitation and a weak significant negative response to the spring and summer temperatures. Climate-growth relationships were further first studied using the response functions for the significant seasons that were detected from the correlation analysis and then for individual months from previous October to current September. These results also highlighted the findings that higher precipitation in the current summer months has a beneficial effect on the tree-ring width. The conducted correlation between the residual chronology and the Standardised Precipitation Evapotranspiration Index indicated that a high summer value of this drought index had a positive impact on the pine growth and reinforced the previously detected relevance of September as an important month for the Austrian pine growth. These preliminary results point out that some additional climate-Austrian pine growth studies (application of various tree-ring features, growth data with a much longer time span, more sites/stands, etc.) should be performed to obtain new and valuable knowledge important for the sustainable management of Austrian pine forests

Polimorfne krivulje indeksa staništa europske bukve (Fagus sylvatica L.) u centralnoj i istočnoj Srbiji

This study was mainly aimed at constructing polymorphic site index curves for beech in the central (Rudnik mountain – RU, about 15,000 ha) and eastern (Žagubica – ŽA, about 7,000 ha) part of its distribution in Serbia. To obtain suitable height-age data and evaluate the best-fit growth model we used 107 felled dominant beech trees. The Korf, Korsun and Chapman-Richards growth functions per site class were first parameterized and then mutually compared with respect to residual statistics and the significance of their parameters. They were additionally parameterized in line with empirical data on the value and age of the culmination of current annual height increment (CAIh). The obtained results indicated that the Chapman-Richards growth function showed the best results both by statistical (residuals standard error, significance of the parameters, distribution of residuals, and homoscedasticity) and by empirical criteria (the CAIh culmination time, the maximal values of the CAIh, and the attained height of trees at a certain age) of the height-age beech modelling in the analyzed regions. The obtained polymorphic site index curves which classify sites with regard to their productivity can be very helpful in planning appropriate silvicultural treatments, and for decision-making in forest management planning, forest policy and ecology and, consequently, in the sustainable management of beech forests in Serbia and some neighbouring countries with a similar forestry sector development.Moderno uzgajanje šuma, predviđanje rasta i prirasta, uređivanje šuma i donošenje odluka na različitim razinama, zahtijevaju pouzdane pokazatelje proizvodnosti staništa. Najvažniji pokazatelj potencijalne proizvodnosti šumskih staništa je dominantna visina sastojine u referentnoj dobi – stanišni indeks. Usprkos velikom značenju evaluacije proizvodnog potencijala staništa za gospodarenje šumama, istraživanja proizvodnosti staništa u vidu stanišnih indeksa nisu intenzivno provođena u Srbiji, ali i u cijeloj regiji zemalja s prostora bivše države Jugoslavije (s izuzetkom Slovenije). Stoga je cilj istraživanja bio (1) modeliranje odnosa visine i starosti dominantnih stabala bukve i (2) konstrukcija polimorfnih krivulja stanišnih indeksa za bukvu u središnjoj i istočnoj Srbiji te (3) usporedba dobivenih rezultata iz Srbije s rezultatima o visinskom rastu i prirastu bukve iz zemalja u neposrednoj blizini.Istraživanje je provedeno u bukovim jednodobnim sastojinama u području Žagubice – ŽA, u istočnoj Srbiji (oko 15.000 ha ukupne površine pod šumom) i planine Rudnik – RU, u središnjoj Srbiji (oko 7.000 ha ukupne površine pod šumom). Uzorak od 53 (ŽA) i 53 (RU) dominantnih stabala bukve korišten je za dobivanje odgovarajućih podataka o visini stabala u različitim dobima. Stabla su odabrana tako da pokrivaju širok raspon dobi i uvjeta staništa unutar područja istraživanih kompleksa bukovih šuma. Za utvrđivanje polimorfnih krivulja staništa testirane su funkcije Korfa, Korsuna i Chapman-Richardsa (CHR), čiji su parametri utvrđeni metodom predviđanja vrijednosti parametara. Rezultati dobiveni u našoj studiji ukazali su da se CHR model pokazao najboljim i kada su u pitanju značajnost i preciznost predviđanja parametara modela, ali i biološke značajke modela koje se odnose na uklapanje modela u mjerene podatke o visinskom rastu i prirastu bukve. Također, raspodjela reziduala kod CHR modela pokazala je najmanja odstupanja od normalne, dok su ostala dva modela imala određeni stupanj heteroscedastičnosti. Drugi poželjan kriterij za ocjenu modela indeksa staništa može biti njegovo „ponašanje“ u pogledu sličnosti rezultata dobivenih primjenom modela i empirijskih rezultata, u ovome slučaju s empirijskim podacima o dobi kulminacije i maksimalnih vrijednosti tečajnog visinskog prirasta (CAIh) po klasi staništa. Dobiveni rezultati sugeriraju da su se krivulje indeksa staništa generirane funkcijom CHR najbolje uklopile u podatke dobivene postupkom analize stabla. Modeli Korf i Korsun dali su relativno točne rezultate za najbolje dvije klase staništa (bonitete), ali generirali su nerealne procjene za slabije produktivna staništa. Stoga se može zaključiti da se CHR model pokazao najboljim i prema ovom biološkom kriteriju. Modelirani podaci o dobi kulminacije CAIh pokazali su da bukva na području RU i ŽA dostiže dob kulminacije godišnjeg tečajnog visinskog prirasta (CAIh) kasnije nego u Austriji i Hrvatskoj, dok je slična dobi utvrđenoj u Sloveniji i Srbiji (sa drugog područja). Dobivene krivulje indeksa staništa ponajprije se trebaju koristiti za procjenu proizvodnog potencijala bukve na srednjim i nisko produktivnim staništima u Srbiji. Daljnje istraživanje u Srbiji treba provesti na najproizvodnijim staništima i u smjeru primjene nekih ‘’od bazične dobi nezavisnih’’ pristupa, kao što su algebrični diferencijalni pristup - ADA i generalizirani algebrični diferencijalni pristup – GADA. Determinirane polimorfne krivulje stanišnih indeksa bukve su vrlo korisne u određivanju odgovarajućih uzgojnih tretmana, općoj klasifikaciji staništa s obzirom na njihovu kvalitetu i za primjenu načela potrajnog gospodarenja šumama

Karakteristike asinhrone mašine sa dvostranim napajanjem i primena za korišćenje energije vetra

This paper presents the characteristics of an asynchronous machine with winded rotor, fed both from stator and from rotor side. Mathematical model and the equivalent circuit of this mode of asynchronous machine’s work are defined and expressions for characteristic values are derived. On the basis of the obtained characteristics it is pointed out that this kind of electrical machines, while working in generating mode, may be used in systems where electric power is generated from wind energy. Main characteristics of wind turbine – doubly-fed asynchronous machine system are processed.U radu su date karakteristike asinhrone mašine sa namotanim rotorom koja se napaja i sa strane statora i sa strane rotora. Definisani su matematički model i ekvivalentna šema ovog režima rada asinhrone mašine i izvedeni su izrazi za karakteristične veličine. Na osnovu dobijenih karakteristika ukazano je na mogućnost korišćenja ove vrste električnih mašina, kada rade u generatorskom režimu rada, u sistemima za generisanje električne energije iz energije vetra i obrađene su osnovne karakteristike sistema vetroturbina – asinhrona mašina sa dvostranim napajanjem

Usporedna analiza utjecaja klimatskih čimbenika na radijalni rast autohtonih vrsta borova (Pinus spp.) u središnjoj Bosni i Hercegovini

In central Bosnia and Herzegovina, in the Zavidovići-Teslić area, the study of the radial growth of Austrian and Scots pine (autochthonous pine species) trees was conducted using the dendrochronological method in order to identify the differences between the species in terms of the influence of climatic variables on the tree ring formation. Trees were sampled in five experimental areas or five sites. The first site had a Scots pine stand, while the second had an Austrian pine stand, and the other three sites had mixed stands of Scots and Austrian pine. Cross-dating was conducted using visual on-screen techniques of CDendro software and statistical methods using Cofecha software. The tree ring series were standardized using the Arstan program and cubic smoothing spline. It produced Scots pine regional chronology, 145 years long (1870-2014), and Austrian pine regional chronology, 180 years long (1835-2014). Correlation analysis of the relationship between the index of tree-ring width and precipitation and temperature in the characteristic periods of the year showed a negative effect of temperature (except in winter months) and a positive effect of precipitation on the tree ring formation. The statistically significant dependence of the tree-ring width index on the SPEI indices indicates a significant impact of moisture deficiency on the tree ring formation in the period from June to August (r = 0.33 in June, r = 0.45 in July and r = 0.47 in August) for Scots pine and in the period from June to September (r = 0.36 in June, r = 0.43 in July, r = 0.47 in August and r = 0.30 in September) for Austrian pine. The analysis of the relationship between climatic parameters and the chronologies of Scots and Austrian pine shows similar relationships between radial growth and climate but the influence of climate is somewhat more pronounced in Austrian pine. In the study area, the radial growth of both tree species is significantly determined by climate conditions. In other words, the chronology of these species has a good climatic signal, especially the drought signal in the summer months.U Zavidovićko - Teslićkom području, u središnjoj Bosni i Hercegovini, dendrokronološkom metodom je proučavan radijalni rast stabala crnog i bijelog bora, autohtonih vrsta u pomatranom području. Cilj je bio identifikacija razlika između spomenutih vrsta glede utjecaja klimatskih čimbenika. Uzorci su uzeti iz stabala s pet lokaliteta. Na prvom lokalitetu je sastojina bijelog bora, na drugom crnog bora, a na ostala tri lokaliteta su mješovite sastojine. Standardizacija serija širina godova (radijalnih prirasta) obavljena je primjenom Arstan programa. Dobivena je regionalna kronologija bijeloga bora dužine 145 godina (od 1870. do 2014.) i regionalna kronologija crnoga bora dužine 180 godina (od 1835. do 2014.). Ispitivanje zavisnosti između indeksa širine goda i oborina odnosno temperature u pojedinim karakterističnim periodima godine, pokazalo je negativan utjecaj temperature (osim u zimskim mjesecima) na formiranje goda i pozitivan utjecaj oborina. Statistički značajna zavisnost indeksa širine goda od SPEI indeksa ukazuje na značajan utjecaj nedostatka vlage u periodu lipanj – kolovoz (r = 0,33 u lipnju, r = 0,45 u srpnju i r = 0,47 u kolovozu) za bijeli bor i periodu lipanj - rujan (r = 0,36 u lipnju, r = 0,43 u srpanju, r = 0,47 u kolovozu i r = 0,30 u rujnu) za crni bor na formiranje godova. Analiza odnosa klimatskih parametara i formiranih kronologija bijeloga i crnoga bora pokazuje slične odnose između širine goda i klime, ali je utjecaj klimatskih čimbenika nešto više izražen kod crnog bora, kojemu više odgovaraju uvjeti staništa na promatranom području. U promatranom području radijalni prirast stabala obje vrste drveća značajno je uvjetovan klimatskim čimbenicima, odnosno kronologije navedenih vrsta imaju dobar klimatski signal, a posebno signal suše u ljetnim mjesecima

Anamorfne krivulje indeksa staništa mezijske bukve (Fagus × taurica Popl.) u području Žagubica, istočna Srbija

Data on average age and height of dominant moesian beech trees from 109 temporary sample plots were used to establish anamorphic site index curves (SI) calculated from seven growth functions (Chapman-Richards, Korf, Korsun, Hosfeld IV, Todorović, Schumacher and Prodan). The base age for calculation of SI was 100 (SI100). The guide curve method was applied. For the evaluation of the models, statistical as well as visual examinations were considered. The results showed that all the applied models had a relatively high coefficient of determination (R2) value, indicating that the models accounted for more than 65% of the variation in the dominant height, which can be considered as large effects. Korsun’s function shows the best overall statistics, which makes this model the most suitable for the construction of anamorphic site index curves for the study area.The obtained results are of importance for effective decision making in forest management planning, forest policy, and ecology in Serbia. Namely, regarding the relatively large sample and well-distributed sample units per age and site classes as well as the source of data (temporary sample plots), the developed site index curves and the method of stratifying the sites according to their productivity were performed for the first time in Serbia. Future studies should be performed in order to expand the knowledge on the dominant beech height-age relationships in the studied region using another well-known procedure of site index construction – polymorphic site index curves and stem analysis data.Dosadašnja istraživanja i njihovi rezultati u čistim i mješovitim sastojinama mezijske bukve na različitim staništima, kao najrasprostranjenije i najvažnije vrste drveća u Srbiji, nisu dovoljna za potpuno sagledavanje i sistematizaciju staništa i sastojina prema trenutnoj i potencijalnoj razini proizvodnosti (Vučković i Stajić 2005). Postoji više različitih načina utvrđivanja potencijalne proizvodnosti staništa. U tom kontekstu, visina stabala je generalno prihvaćena kao najznačajniji indikator proizvodnosti staništa. S obzirom na to, potencijalna proizvodnost staništa najčešće se utvrđuje preko stanišnog indeksa (eng. site index – SI) koji se određuje kao iznos dominantne visine sastojine u određenoj starosti (Monserud 1984; Sterba and Monserud,1993; Bravo and Montero 2001; Gadow 2002; Skovskaard and Vanclay 2008; Pretzsch 2009; Zlatanov et al. 2012; Bontemps and Bouriaud 2014; Kitikidou et al. 2015).Usprkos velikom značenju evaluacije proizvodnog potencijala staništa za gospodarenje šumama, istraživanja proizvodnosti staništa u vidu stanišnih indeksa nisu intenzivno provođena u Srbiji, ali i u cijeloj regiji zemalja s prostora bivše države Jugoslavije (s izuzetkom Slovenije). U šumarstvu Srbije klasifikacija staništa prema proizvodnosti provodi se pomoću tzv. bonitetnih visinskih grafikona, koji predstavljaju izjednačenu ovisnost visine o prsnom promjeru i bonitetu staništa u obliku visinskih krivulja. Broj izjednačenih linija visina u ovisnosti o prsnom promjeru predstavlja broj bonitetnih razreda, ujedno i broj nizova obujma u tarifama, koji se određuju prema potrebi (Banković and Pantić 2006). U cilju poboljšanja postojećeg sustava klasifikacije staništa prema proizvodnosti, njegove usklađenosti s dominantnim načinom klasifikacije staništa po proizvodnosti i kreiranja mogućnosti za usporedbu dobivenih rezultata s rezultatima ocjene proizvodnog potencijala staništa bukve u Europi, neophodno je definirati krivulje stanišnih indeksa (eng. site index curves) za ovu vrstu drveća. Stoga, cilj istraživanja je (1) modeliranje odnosa visine i starosti dominantnih stabala bukve i (2) konstrukcija anamorfnih krivulja stanišnih indeksa za bukvu na području Žagubice u istočnoj Srbiji.Istraživanje je provedeno u bukovim jednodobnim sastojinama u području Žagubice (oko 15 000 ha ukupne površine pod šumom). Nadmorska visina je od 650 do 1250 m. Prosječna godišnja temperatura i količina oborina iznose 9,8 °C i 682 mm. Za utvrđivanje stanišnih indeksa korišteni su podaci o starosti i visinama dominantnih stabala sa 109 subjektivno odabranih privremenih kružnih pokusnih ploha (u cilju pokrivanja cjelokupnog raspona stanišnih uvjeta i dobnih razreda), veličine 500 m2. Na svakoj plohi je utvrđena prosječna starost i srednja visina 10% najdebljih stabala. Izmjereni podaci o visinama u različitim starostima upotrijebljeni su za dobivanje prosječne krivulje rasta u visinu (metoda vodeće krivulje, eng. guide-curve method). Prosječna krivulja visinskog rasta je modelirana pomoću 7 različitih funkcija rasta (Tablica 2). Temeljna starost za izračun SI iznosi 100 godina (SI100). Kriteriji za odabir najboljeg modela bili su sljedeći: koeficijent determinacije, suma kvadrata relativnih odstupanja i relativna prosječna kvadratna greška (%). Odgovarajućim procedurama dobivene su tzv. anamorfne krivulje stanišnih indeksa.Prvi dobiveni rezultati provedene analize pokazuju da primijenjeni modeli imaju relativno visoke koeficijente determinacije, ukazujući na to da objašnjavaju više od 65% varijacije u dominantnim visinama, što se prema kriterijima Cohena (1986) može smatrati kao veliki učinak. Između ostalih, modeli Korsuna i Schumachera pokazuju najbolje ukupne statističke značajke. Ipak, Korsunov model je preliminarno izabran za kalkulacije stanišnih indeksa zbog nešto boljih statističkih indikatora. U cilju dodatne ocjene primjenjivosti Korsunove funkcije i ostalih modela, konstruirane su i grafički predstavljene prosječne krivulje visinskog rasta (Slika 1). Korsunova se funkcija pokazala kao najbolja s obzirom na promatrane statističke indikatore i po praćenju tijekova rasta, pa je definitivno izabrana kao model za konstrukciju seta anamorfnih krivulja stanišnih indeksa (Slika 2).Ovaj rad ima veliko značenje za šumarski sektor u Srbiji i bukvu kao dominantnu vrstu. U izvjesnom smislu, imajući u vidu veliki uzorak s dobro distribuiranim jedinicama unutar različitih starosti i stanišnih razreda, ovo istraživanje je prvo obimno istraživanje proizvodnosti bukovih staništa. Uz to, primijenjena metoda stratifikacije staništa prema proizvodnosti je po prvi puta provedena na bazi stanišnih indeksa dobivenih s privremenih pokusnih ploha. Dobivena saznanja imaju praktičnu primjenjivost u okviru gospodarenja šumama, kao temelj za donošenje odluka na polju planiranja, šumarske politike i ekologije. Naravno, potrebno je provoditi daljnja istraživanja u cilju proširivanja baze podataka i saznanja o odnosu između dominantnih visina i starosti u bukovim sastojinama u proučavanom području, kao i pristupiti konstrukciji polimofrnih krivulja stanišnih indeksa. Na taj način polimorfne krivulje stanišnih indeksa bile bi takođe vrlo korisne i u određivanju odgovarajućih uzgojnih tretmana, općoj klasifikaciji staništa s obzirom na njihovu kvalitetu i za implementaciju načela potrajnog gospodarenja šumama

Jednofazni asinhroni generator sa dva namotaja na statoru

The paper describes a particular realization of the single-phase asynchronous generator with a double coil on the stator, which is suited for applications in agriculture in cases where the safety mandates the use of low voltages. We provide basic elements of the design, define equivalent circuits and report the results of experimental testing.U radu je prikazana jedna posebna izvedba jednofaznog asinhronog generatora sa dva namotaja na statoru, pogodna za primenu u poljoprivredi u onim slučajevima gde je, radi zaštite od opasnog dejstva električne struje obavezna primena malih napona. Dati su osnovni elementi konstrukcije definisane ekvivalentne šeme i prikazani rezultati eksperimentalnog ispitivanja

Konstrukcija, karakteristike i primena u poljoprivredi elektromagneta za magnetnu obradu vode

This paper presents the characteristics of a special, transformer-type electromagnet MOV - 2 that can be used in the magnetic treatments of water, for the purpose of its further use in various fields of science, industry, agriculture and medicine. This electromagnet is the original technical solution. Its construction makes it possible to obtain high values of magnetic induction, to regulate magnetic field parameters and continuously adjust the length of the air-gap in which a tube containing water which is treated magnetically is placed. The use of magnetized water is applied to the field of agriculture.U radu su date karakteristike specijalnog elektromagneta transformatorskog tipa MOV – 2 za magnetnu obradu vode radi njene dalje upotrebe u raznim oblastima nauke, industrije, poljoprivrede i medicine. Elektromagnet je originalno tehničko rešenje koje svojom konstrukcijom omogućava dobijanje visokih vrednosti magnetne indukcije, regulaciju parametara magnetnog polja i kontinualno podešavanje optimalne dužine vazdušnog zazora u kome se nalazi cev sa vodom koja se magnetno obrađuje. Primena magnetisane vode konkretizovana je na oblast poljoprivrede

Effects of Thinning in a Plantation of Poplar Clone I-214 withWide Spacing

U nasadu topole klona I-214, osnovanom pri razmaku sadnje 6 × 6 m u sistemu kvadratne veze na zemljištu srednje povoljnom za uzgoj topola, analizirani su učinci prorjede koja je izvedena 11 godina nakon osnivanja nasada. Prorjeda je imala selektivan karakter, odnosno izdvojena je grupa tzv. perspektivnih stabala u broju koji odgovara prosječnom razmaku od 8,5 × 8,5 m i uklonjeni su njihovi izraziti konkurenti. Uzgojno neperspektivna stabla i stabla zaostala u rastu, što je uglavnom posljedica naknadnih popunjavanja, također su uklonjena. Prorjedom su uklonjena 122 stabla po hektaru (46 %), 6,45 m2/ha (43 %), 66,08 m3/ha (42 %) i 2645 m2/ha (40 %) površine projekcije krošnje, što je jačina zahvata iznad tzv. kritične temeljnice. Sortimentna struktura prorjednog etata pri selektivnoj prorjedi povoljnija je od shematskih prorjeda u mlađim nasadima na povoljnijim staništima i daje 50 % tehničkog drva, 30 % celuloznog drva i 20 % otpatka. Nakon 5 godina na prorijeđenoj je površini srednji promjer po temeljnici veći za 10,6 %, volumen srednjeg stabla veći je za 21,9 %, a površina projekcije krošnje srednjeg stabla veća je za 59,0 % u odnosu na neprorijeđenu površinu. Nasuprot tomu, srednja visina po Loraju na prorijeđenoj je površini za 4,2 % manja u odnosu na neprorijeđenu površinu. Veći tečajni prirast promjera, volumena i površine projekcije krošnje stabala na prorijeđenoj površini ukazuje na mogućnost produžetka ophodnje i povoljniju sortimentnu strukturu u odnosu na kontrolnu površinu.Research was conducted in the experiment plot of euramerican poplar, clone I-214, which was founded with one year seedling type 1/1 with spacing 6 × 6 m in the square system on the alluvial soils of river Sava basin in which browning processes is expressed. Eleven years after the plantation establishment 3 blocks with two experimental plot of 0.2016 ha, which are separated by a so-called. protective order, were singled out. In the experimental plot all the trees were numbered and measured by two cross-dbh, with an accuracy of 1 mm, and height, with an accuracy of 1 dm. The crown projection radius of 8 positions, each rotated to 45o, were measured. On the three experimental plots (one in each block) selective thinning was carried out (PP-E), at which in each plots 50 % of trees were cut down, or the distance between the trees raised on average 8.5 × 8.5 m. Firstly, a collective called. promising trees set aside, in the number that corresponds to an average distance of 8.5 × 8.5 m, and their main competitors were removed. The trees behind in development, which is mainly due to additional filling in plantations two years after planting, are also removed because they were judged as silvicutural non-perspective. The remaining three experimental plots were control (PP-K). In each repetition trees for dendrometric analysis were sampled, the dominant one (dg20%) and a mean tree which has mean quadratic diameter (dg). In the 16thyears of plantation development diameters at breast height (dbh) and height of each tree were re-measured, sa well as crown projection radius. The development of mean and dominant trees showed that the investigated habitat is the medium favorable for the cultivation of the poplar clone I-214. Current increment of diameter, height and volume in the 11thyear was in the intensive phase, where volume increment has not yet culminated (Figure 1–3). As a suitable element of growth to determine the start of thinning operation on a biological point of view, can be ring width along the spindle tree. In the first five years the tree has had a full solitary growth, and from the seventh year there is a competitive relationship between trees in plantation, which is manifested by changing the ring width along the spindle tree (Figure 4 and 5). This means that before the seventh year thinning does not have any biological justification. Models 1 and 2 of volume tables, constructed measuring felled trees from thinning (Table 2), and which are the dependence of the volume of tree from diameter at breast height (model 1) and from the diameter at breast and height (model 2), proved to be equally good at calculating the volume per hectare in the 11thyear and more convenient compared to other tables and models (Table 3). To calculate the volume in the 16thyear two input volume tables can be successfully used (model 2), while the application of model 1 is limited at the 11thyear. In the 11th year at the experimental plot an average of 263–266 trees per hectare are found, which represents a survival rate of about 95 %. Total basal area averaged from 14.70 to 14.97 m2/ha, while volume was an average from 156.67 to 157.62 m3·ha-1. By applying the statistical t-test significant difference in the number of trees, basal area and volume per hectare was not determined within the experimental plots before applying the silvicultural treatments (Table 4). By applying thinning operation,122 trees per hectare (46%), 6.45 m2/ha (43 %) of the total basal area, 66.08 m3/ha (42%) of the total volume and 2645 m2/ha (40 %) of the the crown projection area were removed, which represent a strong procedure and is located above the so-called. critical basal area (Table 4, 13).Size of allowable cut in the thinning of 66.08 m3/ha was in the limits expected on the basis of previous research for the density of 278 trees per hectare and the habitat medium favorable for the development of poplar clone I-214. However, the assortment structureof allowable cut is more favorable compared to thinning in younger plantations in the more favorable habitats and produces 50 % of technical wood, 30% of pulpwood and 20 % of wastewood (Table 4, 9, 15). Between 11 and 16 years on both series of experimental plot the mortality of trees was not determined. Five years after application of thinning treatment a significant difference in the number of trees, basal area, volume and crown projection areas of trees per hectarewere determined between the experimental and control plots (Table 4). The significant difference in the mean diameters, heights and crown projection areas of the mean and the dominant trees (Table 5, 6), as well as between the diameter strucures (Figure 7) were also determined between investigated plots. For a period of 5 years after application of thinning operation at the experimental field current basal area and volume increment per hectare accounted 85 % of basal area increment and 75 % of volume increment of the control plots wich had the number of trees twice higher than experimental plots (Table 14). For five years of positive reactions to increase growing space of remaining trees on the experimental plots the size of the total basal area and volume of trees removed by thinning operation is not compensated: the total basal area and the volume per hectare amounted to 2/3, and the crown projection area amounted 87 % of the size of the control plot. The reaction of trees on experimental plot with thinning treatment for 5 years is great and is reflected in greater mean diameter by 10.6 %, greater mean tree volume by 21.9 % and increased the crown projection area by 59.0 % compared to control plot. In contrast, the mean Lorey’s height at the experimental plot with thinning treatment decreased by 4.2 % compared to control plot. This has contributed to the intensification of the current (average periodic) volume increment compared to the period before applying thinning operation. Greater assimilation apparatus of trees in the experimental plots with thinning tretament and higher current diameter and volume increment indicate the need to extend the production cycle at the best assortment structure compared to the control plot. The research results indicate the validity of efforts that the thinning operation in poplar plantations should be treated as a biological and an economic category. As a biological category the thinning operation contributes to accelerating the growth of the remaining phenotypically better established trees and achieve optimum production. As economic categories with thinning operation realized the previous crop, and it being understood that the assortment of allowable cut in the thinning cover cost cutting and the establishment of plantations with more trees. In this framework it is necessary to direct further research, because the poplar plantations,which are aimed to applying thinning operation, are flexible enough to allow adaptation to changing market conditions

Effects of Thinning in a Plantation of Poplar Clone I-214 withWide Spacing

U nasadu topole klona I-214, osnovanom pri razmaku sadnje 6 × 6 m u sistemu kvadratne veze na zemljištu srednje povoljnom za uzgoj topola, analizirani su učinci prorjede koja je izvedena 11 godina nakon osnivanja nasada. Prorjeda je imala selektivan karakter, odnosno izdvojena je grupa tzv. perspektivnih stabala u broju koji odgovara prosječnom razmaku od 8,5 × 8,5 m i uklonjeni su njihovi izraziti konkurenti. Uzgojno neperspektivna stabla i stabla zaostala u rastu, što je uglavnom posljedica naknadnih popunjavanja, također su uklonjena. Prorjedom su uklonjena 122 stabla po hektaru (46 %), 6,45 m2/ha (43 %), 66,08 m3/ha (42 %) i 2645 m2/ha (40 %) površine projekcije krošnje, što je jačina zahvata iznad tzv. kritične temeljnice. Sortimentna struktura prorjednog etata pri selektivnoj prorjedi povoljnija je od shematskih prorjeda u mlađim nasadima na povoljnijim staništima i daje 50 % tehničkog drva, 30 % celuloznog drva i 20 % otpatka. Nakon 5 godina na prorijeđenoj je površini srednji promjer po temeljnici veći za 10,6 %, volumen srednjeg stabla veći je za 21,9 %, a površina projekcije krošnje srednjeg stabla veća je za 59,0 % u odnosu na neprorijeđenu površinu. Nasuprot tomu, srednja visina po Loraju na prorijeđenoj je površini za 4,2 % manja u odnosu na neprorijeđenu površinu. Veći tečajni prirast promjera, volumena i površine projekcije krošnje stabala na prorijeđenoj površini ukazuje na mogućnost produžetka ophodnje i povoljniju sortimentnu strukturu u odnosu na kontrolnu površinu.Research was conducted in the experiment plot of euramerican poplar, clone I-214, which was founded with one year seedling type 1/1 with spacing 6 × 6 m in the square system on the alluvial soils of river Sava basin in which browning processes is expressed. Eleven years after the plantation establishment 3 blocks with two experimental plot of 0.2016 ha, which are separated by a so-called. protective order, were singled out. In the experimental plot all the trees were numbered and measured by two cross-dbh, with an accuracy of 1 mm, and height, with an accuracy of 1 dm. The crown projection radius of 8 positions, each rotated to 45o, were measured. On the three experimental plots (one in each block) selective thinning was carried out (PP-E), at which in each plots 50 % of trees were cut down, or the distance between the trees raised on average 8.5 × 8.5 m. Firstly, a collective called. promising trees set aside, in the number that corresponds to an average distance of 8.5 × 8.5 m, and their main competitors were removed. The trees behind in development, which is mainly due to additional filling in plantations two years after planting, are also removed because they were judged as silvicutural non-perspective. The remaining three experimental plots were control (PP-K). In each repetition trees for dendrometric analysis were sampled, the dominant one (dg20%) and a mean tree which has mean quadratic diameter (dg). In the 16thyears of plantation development diameters at breast height (dbh) and height of each tree were re-measured, sa well as crown projection radius. The development of mean and dominant trees showed that the investigated habitat is the medium favorable for the cultivation of the poplar clone I-214. Current increment of diameter, height and volume in the 11thyear was in the intensive phase, where volume increment has not yet culminated (Figure 1–3). As a suitable element of growth to determine the start of thinning operation on a biological point of view, can be ring width along the spindle tree. In the first five years the tree has had a full solitary growth, and from the seventh year there is a competitive relationship between trees in plantation, which is manifested by changing the ring width along the spindle tree (Figure 4 and 5). This means that before the seventh year thinning does not have any biological justification. Models 1 and 2 of volume tables, constructed measuring felled trees from thinning (Table 2), and which are the dependence of the volume of tree from diameter at breast height (model 1) and from the diameter at breast and height (model 2), proved to be equally good at calculating the volume per hectare in the 11thyear and more convenient compared to other tables and models (Table 3). To calculate the volume in the 16thyear two input volume tables can be successfully used (model 2), while the application of model 1 is limited at the 11thyear. In the 11th year at the experimental plot an average of 263–266 trees per hectare are found, which represents a survival rate of about 95 %. Total basal area averaged from 14.70 to 14.97 m2/ha, while volume was an average from 156.67 to 157.62 m3·ha-1. By applying the statistical t-test significant difference in the number of trees, basal area and volume per hectare was not determined within the experimental plots before applying the silvicultural treatments (Table 4). By applying thinning operation,122 trees per hectare (46%), 6.45 m2/ha (43 %) of the total basal area, 66.08 m3/ha (42%) of the total volume and 2645 m2/ha (40 %) of the the crown projection area were removed, which represent a strong procedure and is located above the so-called. critical basal area (Table 4, 13).Size of allowable cut in the thinning of 66.08 m3/ha was in the limits expected on the basis of previous research for the density of 278 trees per hectare and the habitat medium favorable for the development of poplar clone I-214. However, the assortment structureof allowable cut is more favorable compared to thinning in younger plantations in the more favorable habitats and produces 50 % of technical wood, 30% of pulpwood and 20 % of wastewood (Table 4, 9, 15). Between 11 and 16 years on both series of experimental plot the mortality of trees was not determined. Five years after application of thinning treatment a significant difference in the number of trees, basal area, volume and crown projection areas of trees per hectarewere determined between the experimental and control plots (Table 4). The significant difference in the mean diameters, heights and crown projection areas of the mean and the dominant trees (Table 5, 6), as well as between the diameter strucures (Figure 7) were also determined between investigated plots. For a period of 5 years after application of thinning operation at the experimental field current basal area and volume increment per hectare accounted 85 % of basal area increment and 75 % of volume increment of the control plots wich had the number of trees twice higher than experimental plots (Table 14). For five years of positive reactions to increase growing space of remaining trees on the experimental plots the size of the total basal area and volume of trees removed by thinning operation is not compensated: the total basal area and the volume per hectare amounted to 2/3, and the crown projection area amounted 87 % of the size of the control plot. The reaction of trees on experimental plot with thinning treatment for 5 years is great and is reflected in greater mean diameter by 10.6 %, greater mean tree volume by 21.9 % and increased the crown projection area by 59.0 % compared to control plot. In contrast, the mean Lorey’s height at the experimental plot with thinning treatment decreased by 4.2 % compared to control plot. This has contributed to the intensification of the current (average periodic) volume increment compared to the period before applying thinning operation. Greater assimilation apparatus of trees in the experimental plots with thinning tretament and higher current diameter and volume increment indicate the need to extend the production cycle at the best assortment structure compared to the control plot. The research results indicate the validity of efforts that the thinning operation in poplar plantations should be treated as a biological and an economic category. As a biological category the thinning operation contributes to accelerating the growth of the remaining phenotypically better established trees and achieve optimum production. As economic categories with thinning operation realized the previous crop, and it being understood that the assortment of allowable cut in the thinning cover cost cutting and the establishment of plantations with more trees. In this framework it is necessary to direct further research, because the poplar plantations,which are aimed to applying thinning operation, are flexible enough to allow adaptation to changing market conditions