Modelling Stand Variables of Beech Coppice Forest Using Spectral Sentinel-2A Data and the Machine Learning Approach

Background and Purpose: Coppice forests have a particular socio-economic and ecological role in forestry and environmental management. Their production sustainability and spatial stability become imperative for forestry sector as well as for local and global communities. Recently, integrated forest inventory and remotely sensed data analysed with non-parametrical statistical methods have enabled more detailed insight into forest structural characteristics. The aim of this research was to estimate forest attributes of beech coppice forest stands in the Sarajevo Canton through the integration of inventory and Sentinel S2A satellite data using machine learning methods. Materials and Methods: Basal area, mean stand diameter, growing stock and total volume data were determined from the forest inventory designed for represented stands of coppice forests. Spectral data were collected from bands of Sentinel S2A satellite image, vegetation indices (difference, normalized difference and ratio vegetation index) and biophysical variables (fraction of absorbed photosynthetically active radiation, leaf area index, fraction of vegetation cover, chlorophyll content in the leaf and canopy water content). Machine learning rule-based M5 model tree (M5P) and random forest (RF) methods were used for forest attribute estimation. Predictor subset selection was based on wrapping assuming M5P and RF learning schemes. Models were developed on training data subsets (402 sample plots) and evaluations were performed on validation data subsets (207 sample plots). Performance of the models was evaluated by the percentage of the root mean squared error over the mean value (rRMSE) and the square of the correlation coefficient between the observed and estimated stand variables. Results and Conclusions: Predictor subset selection resulted in a varied number of predictors for forest attributes and methods with their larger contribution in RF (between 8 and 11). Spectral biophysical variables dominated in subsets. The RF resulted in smaller errors for training sets for all attributes than M5P, while both methods delivered very high errors for validation sets (rRMSE above 50%). The lowest rRMSE of 50% was obtained for stand basal area. The observed variability explained by the M5P and RF models in training subsets was about 30% and 95% respectively, but those values were lower in test subsets (below 12%) but still significant. Differences of the sample and modelled forest attribute means were not significant, while modelled variability for all forest attributes was significantly lower (p<0.01). It seems that additional information is needed to increase prediction accuracy, so stand information (management classes, site class, soil type, canopy closure and others), new sampling strategy and new spectral products could be integrated and examined in further more complex modelling of forest attributes

PHENOLOGICAL VARIABILITY OF EUROPEAN BEECH (Fagus sylvatica L.) IN THE INTERNATIONAL PROVENANCE TRIAL

U članku su prikazani rezultati istraživanja fenološke varijabilnosti 22 provenijencije obične bukve u međunarodnom pokusu kod Kaknja (BiH), i to za svojstva jesenje obojenosti i zimske retencije lišća. Pokus sadrži osam provenijencija iz Bosne i Hercegovine, četiri iz Njemačke, tri iz Srbije, po dvije iz Hrvatske, Rumunjske i Švicarske, te jednu iz Mađarske. Pokus je osnovan u slučajno randomiziranom blok sustavu sa tri ponavljanja. Analizom varijance utvrđeno je postojanje statistički značajne fenološke varijabilnosti između svih provenijencija u početku, trajanju i završetku pojedinih fenofaza. Provenijencije iz Hrvatske i Bosne i Hercegovine u pravilu su listale ranije od stranih, a kao početak vegetacije može se uzeti 10. travanj. Analizom svojstva obojenosti lišća utvrđena je prisutnost različitih grupa boja u različitim nijansama u određenom periodu. Za svojstvo zimske retencije lišća utvrđeno je da 65,92 % biljaka u pokusu nezadržava list, a da je najveći postotak za to svojstvo iskazala provenijencija Hoellerbach sa 91,05 %. Za sva istraživana fenološka svojstva utvrđena je visoka razina genetičke diferencijacije istraživanih provenijencija. Dobiveni rezultati mogu pronaći svoju primjenu u oplemenjivanju obične bukve, kao i u aktivnostima na očuvanju genetske varijabilnosti metodama in situ i ex situ.Common beech (Fagus sylvatica L.) is the most important species of forest trees in Bosnia and Herzegovina. This research provides the results of investigation into the phenological variability of 22 common beech provenances in the international trial near Kakanj (Bosnia and Herzegovina), both for the properties of autumn coloration and winter leaf retention. The experiment included eight provenances from Bosnia and Herzegovina, four from Germany, three from Serbia, two from Croatia, Romania and Switzerland each and one from Hungary. The experiment was established in a randomized block system with three repetitions.The goal of this research was to establish whether there were differences in variability between the investigated provenances and what features would be important for future management and regeneration of beech forests, as well as for increased production and adaptability.Based on the investigated phenological properties, statistically significant variability was found between all the studied provenances. The established differences included the beginning, duration and end of particular phenophases. There are considerable statistically significant differences in flushing among the studied provenances. Provenances from Croatia and Bosnia and Herzegovina flush earlier than foreign provenances. April the 10th can be considered as the beginning of common beech vegetation in this international trial, because this is the date on which bud opening occurred in twelve out of 22 provenances.The analysis of leaf colour of different common beech provenances revealed variations in the presence of different groups of colours with varying shades in a particular period. Current differences in winter leaf retention indicate that 65.92 % of the plants in the entire experiment do not retain the leaves. The highest proportion of leaf non-retention, amounting to 91.05 %, was manifested by the provenance from Germany (Hoellerbach). It can be concluded that common beech is genetically differentiated according to ecological and vegetation areas and that it shows different morphological and physiological characteristics from different provenance areas. This proves that morphological and physiological properties of common beech are influenced by a number of factors and that each of the investigated properties is determined by a large number of genes.The obtained results can be used in the breeding programme of common beech, as well as in the activities related to the conservation of genetic variability using the in situ and ex situ methods

Istraživanje mehaničkih oštećenja stabala jele i drugih vrsta tijekom eksploatacije – Slučaj Šumarije „Glamoč“

Mechanisation used in forest utilisation has an impact on the occurrence of damage in stand and on forest land. The research in this work had the objective of determining damage on fir trees and other tree species during felling and processing of trees and their skidding using the forest cable-skidder. The research wasconducted in mixed beech and fir forests in the area of FMA “Glamočko”, M.U. “Hrbinje-Kujača”. The following data were gathered on damaged trees: tree type, breast height diameter, economic importance of the tree, amount of damage, location of damage, cause of damage, types of damage. Damage was recorded on a total of 305 trees, 133 trees of silver fir (Abies alba), 130 trees of European beech (Fagus sylvatica), 33 trees of European spruce (Picea abies), 8 trees of rowan/mountain-ash (Sorbusaucuparia) and one tree of sycamore (Acer pseudoplatanus). The overall damage intensity was 18.7%, but together with the old damages, the overall number of ‘wounds’ is 496. According to this, when the old damage isalso considered, then the intensity of damage amounts to 30.6%. The largest amount of damage is in the diameter sub-class ranging from 10 to 14.99 cm. According to the cause of damage, the largest amount of damage occurred during the wood extraction phase (217 trees), while during the felling phase, 88 trees or 29% were damaged. Since the wood extraction phase is divided into the winching and skidding phases, the total number of damaged trees during the winching phase amounted to 157 or 52%, while during the skidding phase, the number of damaged trees was 60 or 19%. To reduce damage to the trees during following operations in forest utilisation, it is necessary to perform more frequent training of all employees working on forest utilisation, to increase controls in execution of operations during forest utilisation, modernise machines used during forest exploitation, and in quality manner open compartments with forest road infrastructure.Mehanizacija koja se koristi u iskorištavanju šuma utječe na pojavu oštećenja u sastojini i na šumskom tlu. Istraživanja u ovom radu su imala za cilj utvrđivanje oštećenja na stablima jele i drugih vrsta drvća pri sječi i izradi drvnih sortimenata te privlačenju šumskim zglobnim traktorom.Istraživanja su obavljena u mješovitim šumama bukve i jele sa smrekom na području ŠGP „Glamočko”, G.J. „Hrbinje-Kujača“. Prikupljeni su sljedeći podaci o oštećenim stablima: vrsta drveća, prsni promjer stabla, privredna važnost stabla, broj oštećenja, mjesto oštećenja, uzrok oštećenja, vrsta oštećenja.Oštećenja su evidentirana kod ukupno 305 stabala, 133 stabala jele (Abies alba), 130 stabala bukve (Fagus sylvatica), 33 stabla smreke (Picea abies), osam stabala jarebike (Sorbus aucuparia) i jedno (1) stablo gorskog javora (Acer pseudoplatanus). Ukupan intenzitet oštećenja je iznosio 18,7%, a kad tome pridodamo i stara oštećenja, ukupan broj ozljeda iznosi 496. Prema tomu, kada se u obzir uzmu i stara oštećenja, tada intenzitet oštećenja iznosi 30,6%. Najveći broj oštećenja se nalazi u debljinskom stepenu od 10 do 14,99 cm.Prema uzroku oštećenja, najveći broj oštećenja je nastao prilikom faze privlačenja (217 stabala), dok je prilikom sječe oštećeno 88 ili 29% stabala. Kako je faza privlačenja podijeljena na fazu primicanja i privlačenja, ukupan broj oštećenih stabala tijekom faze primicanja iznosio je 157 ili 52%, dok je tijekom privlačenja broj oštećenih stabala iznosio 60 ili 19%.Da bi se prilikom sljedećih operacija iskorištavanja šuma smanjile štete na stablima, potrebna je češća edukacija svih djelatnika koji obavljaju poslove iskorištavanja šuma, potrebno je povećati kontrole obavljanja svih poslova prilikom iskorištavanja šuma, modernizirati strojeve koji se koriste prilikom eksploatacije šuma te na kvalitetan način otvoriti odjele šumskim komunikacijama

Modelling Bark Thickness of Norway Spruce (Picea abies Karst)

Background and Purpose: Bark thickness and its share in the volume of roundwood are the most important characteristics of the bark, particularly in the process of timber harvesting, and during scaling of processed logs. Therefore it is very important to have at disposal relatively accurate data regarding these characteristics of bark for particular tree species. The main goal of this paper is to investigate the thickness of the bark and its share in the volume of roundwood of Norway spruce. Materials and Methods: The research was carried out in the area of the Canton 10 of the Federation of Bosnia and Herzegovina and it encompassed 393 trees of Norway spruce from 10 cm to 115 cm of thickness at breast height. Measuring of the mean diameter and double thickness of bark was conducted by section method. In total, 4,647 diameters and bark thicknesses were measured in different relative lengths of stems or in average 10.6 measurements per one stem. Results: As an optimal model for the evaluation of double thickness of the bark of Norway spruce depending on mean diameter of roundwood the function with designated determination coefficient of 0.7142 was selected. The obtained results have confirmed the previously defined relations of investigate characteristics, which are as following: a) with the increase of mean diameter of roundwood (section) double bark thickness is increased from 9.26 mm (thickness class 12.5 cm) to 31.65 mm (thickness class 92.5 cm); b) with the increase of mean diameter of roundwood the share of bark in its volume decreased from 14.26% (thickness class 12.5 cm) to 6.73% (thickness class 92.5 cm). Conclusions: By the actual method of estimating bark thickness or the share of bark in the volume of roundwood of Norway spruce in the forestry of the Federation of Bosnia and Herzegovina a significant error was created which increases with the increase of mean diameter. The obtained results point to the necessity of investigation of these bark characteristics in Bosnia and Herzegovina and represent an inevitable starting point for making adequate tables of bark thickness and its percentage share in the volume of roundwood of Norway spruce

Modeling bark thickness of beech (Fagus sylvatica L.)

Debljina kore i njen udio u obujmu oblog drva predstavljaju bitne značajke u tehnološkom procesu pridobivanja drva, posebno u fazi preuzimanja drva. S obzirom da je itekako važno raspolagati s relativno točnim podacima ovih značajki kore za pojedine vrste drveća, osnovni cilj ovoga rada je istražiti navedene značajke kore bukve. Istraživanje je provedeno na području Kantona 10, a obuhvatilo je 678 stabla bukve od 10 do 85 cm promjera na prsnoj visini i od 5 do 40 m visine. Mjerenje srednjeg promjera i debljine kore obavljeno je metodom sekcioniranja, a ukupno je izmjereno 6.403 promjera i debljina kore ili 9,4 mjerenja po jednom stablu u prosjeku. Rezultati su pokazali sljedeće: a) povećanjem srednjeg promjera oblog drva dvostruka debljina kore povećava se od 6,05 mm (debljinski razred 12,5&nbsp;cm) do 20,69 mm (debljinski razred 82,5 cm); b) povećanjem srednjeg promjera oblog drva udio se kore u obujmu eksponencijalno smanjuje od 9,44% (debljinski razred 12,5 cm) do 4,95% (debljinski razred 82,5 cm). ­Utvrđene razlike u komparaciji s drugim autorima koji su istraživali ove značajke kore bukve, ukazuju na važnost nastavka istraživanja i na drugim područjima u BiH. Na taj način bi se dobili pouzdaniji rezultati koji bi bili primjenjivi za cijelu državu ili parcijalno za pojedine njene dijelove, ako se razlika između područja pokaže statistički ­značajnom. Dobiveni rezultati predstavljaju nezaobilaznu polaznu osnovu za izradu tablica kore bukve i novog ­pravilnika o načinu izmjere oblog drva i utvrđivanja količina.Thickness and share in volume of tree and/or round wood represent the most important features of the bark, especially in the process of timber harvesting, during scaling of processed logs. In forestry of Federation of B&amp;H there are no rules or tables for deduction of double bark thickness based on scientific research. Wood assortments tables for our most important tree species, besides a whole series of wood assortments, also contain the category of waste. From a practical point of view this category can be divided into “real waste” and losses. The real waste in this sense consists of various logging slash and sawdust, while the loss constitutes a prescribed method of measuring the dimensions and calculation of volume and the deduction of the double bark thickness. So, it is very important to have relatively accurate data of the bark thickness for certain tree species. Therefore, the objecti    ve of this paper is to explore double bark thickness and share of bark in the volume of beech round wood. The research was carried out in the area of the Canton 10 of Federation of B&amp;H. The research included 678 sample trees from 10 cm to 85 cm diameter breast height (DBH) and from 5 m to 40 m of height with 6,403 pairs were measured for double bark thickness and diameter in the middle of the round wood (section). Data of double bark thickness in relation to mid diameter of round wood were equalized by following equation with coefficient of determination R2=0.722.The results of research confirmed the regularities defined in previous research and has shown as follows: a) by the increase of mid diameter of round wood, double bark thickness increases from 6.05 mm (thickness class 12.5 cm) to 20.69 mm (thickness class 82.5 cm), b) by the increase of mid diameter of round wood, bark share in the volume decrease exponentially from 9.44 % (thickness class 12.5 cm) to 4.95 % (thickness class 82.5 cm).The research have indicated the need to use the results and incorporating it into applicable rules of deducting the bark on logs or share of bark in the volume depending on diameter over the bark

Model for estimation merchantable wood volume of spruce (Picea abies Karst) in Canton 10, Federation of Bosnia and Herzegovina

U radu su korišteni podaci izmjere 377 modelnih stabala smreke koja su mjerena u oborenom stanju na širem području unutar državnih raznodobnih sastojina u Kantonu 10 (Hercegbosanski Kanton). Za određivanje volumena krupnog drveta stabala primijenjena je metoda sekcioniranja sa sekcijama nejednakih apsolutnih dužina (najčešće od 1 – 2 m). Za izravnanje veličina volumena krupnog drveta od prsnog promjera i visine stabala primijenjena je metoda višestruke regresijske analize. Za procjenu parametara korištenih funkcija, testiranje značajnosti njihovih razlika te provođenje raznih transformacija, kao softversko rješenje korišteni su StatGraphics Centurion XVII. i Statistica 8.0. U cilju izbora „najboljeg“ modela za procjenu volumena krupnog drveta testiran je veći broj poznatih dendrometrijskih dvoparametarskih volumnih funkcija. Kvaliteta izjednačenja i prikladnost testiranih modela ocjenjivani su na bazi utvrđenih veličina osnovnih statističkih pokazatelja za karakteriziranje jačine korelacijskih veza. Najbolje ocjene parametara pokazao je model V7=a0+a1d1,3+a2h+a3d1,3h+a4d1,32+a5 d1,32h uz utvrđeni koeficijent determinacije: R2 = 0,99 i veličinu standardne greške regresije Sey=0,24 m3. Testirajući značajnost razlika između stvarnih volumena stabala iz uzorka i volumena tih istih stabala utvrđenih primjenom odabranog regresijskog modela, utvrđen je prosječni postotak odstupanja od 0,44%. To znači da su u prosjeku za 0,44% niži volumeni u odnosu na stvarne volumene na uzorku od 377 stabala smreke, što ukazuje da je ovaj regresijski model upotrebljiv za primjenu u praktičnom radu, jer je taj prosječni postotak manji od 1%.For assessment of growing stock in B&amp;H forestry praxis as scientific baseline we are using volume tables and tariffs (Drinići dr. 1990). Having in mind the fact that these are constructed based on volume coefficients of the trees taken from German tree volume tables, which originate from single-age assortments, it is justified to suspect that by applying these tables one will get certain differences in quantity of large wood mass related to the actual status of those volumes. It is known that trees of the same tree species coming from single-age assortments are more full-bodied because they have larger volume coefficients compared to the trees of the same species from variable aged and selection forest assortments. That is why the objective of this research is to find “the best” regression model for levelling of volume of large wood of spruce, as dependent variable depending on diameter at breast height and tree height, as independent variables. To achieve this objective we have selected 377 model trees of spruce that were measured in felled condition on wider area of state owned variable aged assortments in Canton 10 (Livno Canton). To determine volume of large wood of trees we applied section method with sections of uneven absolute lengths (most often from 1 – 2 m). For levelling of volumes of large wood depending on diameter at breast height and tree height we applied method of multi-regression analysis. Quality of levelling and appropriateness of tested models was evaluated on the basis of determined values of basic statistical indicators for characterisation of the strength of correlation connections. The best values of the parameters showed model: V7=a0+a1d1,3+a2h+a3d1,3h+a4d1,32+a5 d1,32h with determined determination coefficient: R2 = 0,99 and size of standard regression error: Sey=0,245 m3. By testing significance of differences between actual/real tree volumes from the sample and volume of those trees determined by application of selected regression model by using t-test of pairs, no statistically significant differences were recorded. Average percentage of deviation was -0.44%. That means that in average we get 0.44% lower volumes comparing to the actual volumes in the sample of 377 spruce trees which shows that this regression model is usable for application in practice, because that average percentage is less than 1%. Statistically significant differences were recorded between volumes of trees of selected regression model and volume tables and models of other authors (Stojanović i dr. 1978; Banković i dr. 2003; Špiranec, 1976.). Those deviations vary in the range from 2.53% up to 22.7%. The largest deviations were determined exactly in model that is used in B&amp;H (Stojanović i dr. 1978) and are in amount of 22.7% while the lower deviations were determined for volumes estimated by using model created for spruce trees from Sub-Alpine belt for area of Kopaonik (Banković i dr. 2003) and those amount to 2.53%

Alternative tree species under climate warming in managed European forests

This study estimates the present and future distribution potential of 12 thermophilic and rare tree species for Europe based on climate-soil sensitive species distribution models (SDMs), and compares them to the two major temperate and boreal tree species (Fagus sylvatica and Picea abies). We used European national forest inventory data with 1.3 million plots to predict the distribution of the 12 + 2 tree species in Europe today and under future warming scenarios of +2.9 and +4.5 °C. The SDMs that were used to calculate the distributions were in a first step only given climate variables for explanation. In a second step, deviations which could not be explained by the climate models were tested in an additional soil variable-based model. Site-index models were applied to the found species distribution to estimate the growth performance (site index) under the given climate. We find a northward shift of 461 km and 697 km for the thermophilic species over the regarded time period from 2060 to 2080 under a warming scenario of 2.9 °C and 4.5 °C, respectively. Potential winners of climatic warming have their distribution centroid below 48°N. Fagus sylvatica and Picea abies will lose great parts of their potential distribution range (approx. 55 and 60%, respectively). An index of area gain and growth performance revealed Ulmus laevis, Quercus rubra, Quercus cerris and Robinia pseudoacacia as interesting alternatives in managed temperate forests currently dominated by F. sylvatica and P. abies. The 12 investigated species are already in focus in forestry and it has been shown that the changing climate creates conditions for a targeted promotion in European forests. Nevertheless, area winners exhibited lower growth performances. So, forest conversion with these warm-adapted species goes hand in hand with loss of overall growth performance compared to current species composition. So, the results are a premise for a further discussion on the ecological consequences and the consistency with forest socio-economic goals and conservation policies