The even-aged forest development computer program SIMPLAG: design, structure and application

Predikcija stanja šumskih resursa nezaobilazan je čimbenik u procesu planiranja gospodarenja šumama. Brojni modeli razvoja sastojina i šuma imaju zadatak predvidjeti posljedice postupaka gospodarenja i time unaprijediti proces planiranja gospodarenja. U radu je prikazana struktura računalnog programa SIMPLAG namijenjenog projekciji razvoja regularne, mješovite šume hrasta lužnjaka, simuliranjem različitih scenarija gospodarenja kao podrška za učinkovito planiranje gospodarenja. Osnovnu strukturu programa čine modeli razvoja strukture sastojina, modul za određivanje etata glavnog prihoda i algoritam za oblikovanje scenarija gospodarenja. Modeli razvoja sastojina baziraju se na raspoloživim optimalnim modelima razvoja lužnjakovih sastojina, te smanjenju broja stabala uslijed mortaliteta. Odabir dijelova sastojina za obnovu temelji se na ekonomskom kriteriju razlike potencijalnog prihoda, u okviru ostalih zadanih odrednica (maksimalni površinski etat glavnog prihoda, najmanja i najveća površina sastojine za obnovu, najmanja starost sastojina koje mogu biti obuhvaćene obnovom, najmanja udaljenost između sastojina) unutar scenarija gospodarenja. Modeli sortimentne strukture i cijenik drvnih sortimenata u programu omogućuju projekciju prihoda tjekom simulacijskog razdoblja. Primjena računalnog programa SIMPLAG rezultira podacima o razvoju prostorne i dobne strukture šume, te vrsti, iznosu i vrijednosti očekivanih prihoda za svaki korak simulacije, što omogućava sveobuhvatno vrednovanje postavljenih scenarija gospodarenja te odabir i primjenu optimalnog scenarija gospodarenja.Forest management planning in many cases is based on predicting of the development and future state of forest resources. A numerous stand development and forest development models are used as a support in forest management. During the last two decades the development and use of simulation models aimed to design of an integrated computer application as useful support for managing not only the forest but the natural resources in general. This paper presents the architecture of the computer program SIMPLAG, for simulation of development of an even-aged forest, particularly of pedunculate oak forests with an irregular structure (age class distribution, understocked old stands). The main components of the program are stand structure development models, the module for planning of stand regeneration (spatial and temporal) and the algorithm for the creation of the management scenarios. Development of the program was aimed to achieve: simulations of the pedunculate oak forest development based on the different management scenarios, and possibility of choosing of an appropriate management options which could lead to improving of the forest and stand structure in a long term. Built-in stand development models are based on available theoretical models for the pedunculate oak, and on reducing the number of trees due to mortality. According to a separate development models, development structure of the old stands up to time of regeneration (reduction of oak trees due to mortality, thinning and the formation of secondary stand to preserve soil), and development of newly regenerated stands (denser, mixed stands and thus more stable), are projected. There are separate structure development models for four tree species: pedunculate oak (Quercus robur L.), narrow-leaved ash (Fraxinus angustyfolia), hornbeam (Carpinus betulus L.) and "other broad-leaved trees". Ranking and selection of stands or a part of stands according to regeneration priority are based on the economic criterion. The criterion means difference in potential revenue as a result of decision: prompt stand regeneration or adjournment of stand regeneration for 20 years. Habitat characteristics, structural and economic features of the stand are included too (Cavlovic et al. 2011a). As a base for a rough selection of part of stand for regeneration, the program uses inventory data (0.09 ha circular sample plots on network 100 * 100 m, each sample plot represent 1 ha of the stand). Calculation of the potential revenues during the projection period is based on the obtained relevant models of assortment structure and the prices of wood assortments, which are integrated in the program. Through a complex algorithm within the guidelines for the creating scenarios of future forest management (the maximum 10-year regeneration area, minimum and maximum area of the stand for regeneration, the minimum age of stands considered for regeneration, the minimum distance between regenerated stands), allows the numerous projections of the spatial and temporal forest development. Each step of the projection is showed on an interactive map that can display information for each 1 ha area or stand (group of 1 ha areas) separately (Figure 3, Figure 5). The basis of the spatial view is ESRI shape file that is required to set before creating the simulation. Plotting the spatial view is created by using GDI + programming instructions. The program is fully developed on .NET Framework 3.5 platform, using development tools Visual Studio 2008 and MS Access 2007 database. Used development language is C#. The SIMPLAG program provides information’s of the spatial and temporal forest development, development of age class distribution, stand development, amount and value of the revenues generated for each step of the projection, according to the different management scenarios. This information’s allow a comprehensive evaluation of a different management scenarios and selection of the most suitable management options

THE EFFECTS OF DIFFERENT STAND REGENERATION PLANNING ON MANAGEMENT AND PEDUNCULATE OAK FOREST DEVELOPMENT – A SMALL SIZE MANAGEMENT CLASS CASE STUDY

Planiranje budućeg gospodarenja šumama hrasta lužnjaka posebno je zahtjevno u uvjetima narušene dobne strukture šume, propadanja stabala i strukture sastojina. Izlučivanje površina (novih sastojina) s obzirom na strukturne značajke i pravodobna provedba obnove značajno je pitanje gospodarenja šumama hrasta lužnjaka. Stoga je u radu cilj istražiti učinke primjene dva suprotna pristupa rangiranja sastojina prema prioritetu za obnovu i intenzitetima obnove šume, na razvoj strukture sastojina, dobne i prostorne strukture šume, kao i na očekivano kretanje količine i vrijednosti budućih prihoda. Kao objekt istraživanja poslužila je stvarna šuma (uređajni razred hrasta lužnjaka) u gospodarskoj jedinici Opeke površine 429,4 ha (26 sastojina prosječne površine od 16,5 ha), sastavljena od sastojina starijih od 110 godina. Provedena je projekcija gospodarenja i prostorno-vremenskog razvoja regularne šume tijekom budućih četrnaest 10-godišnjih razdoblja (ophodnja 140 godina) pomoću računalnog programa SIMPLAG, te vrednovanje različitih pristupa gospodarenja na temelju usporedbi i odstupanja aktualnih od teoretskih kriterija gospodarenja. Rezultati su pokazali utjecaj intenziteta obnove šume i načina određivanja sastojina za obnovu:, (1) na razvoj prostorne i dobne strukture šume, 2) na kretanje i ukupne iznose etata te bruto i neto prihoda i na 3) drvne zalihe šume. Intenzivnom obnovom šume postigla bi se veća prosječna drvna zaliha šume, veći iznosi etata i prihodi, uz veliko odstupanje od teoretskih. Pristupom prioritetne obnove sastojina lošije strukture postigli bi se isto tako veći iznosi etata i prihoda uz manje odstupanje od teoretskih, što je u smislu potrajnosti gospodarenja prihvatljivije. Buduće gospodarenje istraživanom šumom temeljeno na postupnoj obnovi šume tijekom duljeg razdoblja, prioritetnom obnovom novoizlučenih površina do 5 ha na dijelovima postojećih sastojina lošije strukture, može se preporučiti s obzirom da bi taj pristup dugoročno vodio oblikovanju odgovarajuće prostorne i dobne strukture šume uz najveće ekološke i ekonomske učinke.Pedunculate oak forests in Croatia are characterized with an irregular age-class distribution (larg share of mature stands), pedunculate oak dieback and decreasing stand structure quality, as well as large sized stands and they spatial heterogenity (density of pedunculate oak). Future management and development of the forest depend on actual age-class structure, intensity and spatial-temporal dynamics of forest regeneration. Thereby, spatial dividing of an appropriate size areas (new stands) and defining priority of their regeneration over future periods, which should be based on an objective criteria (e.g. potential rent difference as a consequence of the decision of regeneration (prompt or adjournment) of a potentially mature pedunculate oak stands), is key question. Based on developed computer program application, paper aim is to research effects of two opposite approaches of regeneration priority stand ranking and different intensities of forest regeneration on: stands growth, development of age-class structure and spatial forest structure, as well as possible trends in amounts and values of future revenues. Object of the research is real even-aged forest (management class of pedunculate oak) in Opeke management unit. Area of the forest is 429.5 ha divided into 26 stands of average area of 16.5 ha. Youngest stand is 107 years old and the oldest is 185 years. There is large deviation between actual and theoretical age-class distribution of the forest (table 1). Projection of management and spatial-temporal development of the even-aged pedunculate oak forest over future fourteen 10-year periods (rotation) is performed by computer program SIMPLAG (Teslak i dr., 2012). Within "theoretical" intensity of regeneration (30 ha in 10-year regeneration area, 2–6 ha stand regeneration size, 250 m minimal distance between regenerated stands), and intensive regeneration (50 ha in 10-year regeneration area, 3–13 ha stand regeneration size, 250 m minimal distance between regenerated stands), there were two approaches of regeneration priority stand ranking: – stand regeneration ranking according to lowest potential rent difference (poor structure stand has highest regeneration priority – NSR); – stand regeneration ranking according to highest potential rent difference (well structure stand has highest regeneration priority – OSR) Different management approach validation is performed using comparison and deviation indices (actual vs. theoretical management criteria average deviation). Results showed that less intensive regeneration approach with appurtenant requirements would lead to development of an optimal forest structure as to larger number, smaller sized (5 ha average area), and more homogeneous stands (fig. 1a). Development of age-class forest structure has indirectly manifested in trends of average stand age (fig. 1b). An approach of intensive forest regeneration would result with fast decrease of average stand age, oscillating around theoretical stand age and never would achieve theoretical age-class structure. A question of maintenance and conservation of pedunculate oak stands for long period, up to stand age above 250 years, is very important, particular in a case of less intensive regeneration over long regeneration period of forest. Influence of forest regeneration intensity and approach of regeneration priority stand ranking on trends and total amont of forest growing stock, intermediate and regeneration fellings (fig. 2, tab. 2 and 3), as well as on value of fellings (fig. 3, tab. 2 and 3), has obtained. More intensive regeneration would result with larger average growing stock, total fellings and gross/net value of fellings, meanwhile with large deviations around theoretical models. Approach of priority regeneration of poor quality stands would achieve larger amounts of fellings and revenues too, but with less deviations, what is in terms of sustainability, more acceptable. Future forest management for the forest (and forests of such structure) based on gradually forest regeneration over longer period, by priority regeneration of areas up to 5 ha within poor quality structure parts of current forest stands (new stands), is recommended. This management approach would lead to forming of an appropriate spatial forest structure and development of a balanced age-class structure, with the highest ecological and economic effects

Economic Consequences of Different Management Approaches to Even-Aged Silver Fir Forests

Economic analysis of even-aged fir stand management was illustrated using the example of the forests of the Croatian Dinaric region, as well as their transformation into more stable unevenaged structures. Two scenarios (even-aged, uneven-aged) were simulated against the backdrop of the existing forest stand structure of future forest stand management during a 140-year period using forest growth modeling software MOSES version 3.0 in order to identify economic differences amongst different scenarios both at stand level and at forest level. The research included forest management analysis throughout the transformation period and subsequently the continuation of balanced state forest management. Moreover, the research also provided the opportunity of forest purchase within the price range from 1000 to 12,500 EUR/ha, amid assumed fluctuation of selling prices of timber assortments throughout the simulation period. Discount rates from 1% to 5% were used during the economic analysis. The research findings showed that, according to harvesting costs, Net Present Value and Internal Rate of Return, uneven-aged forest management system, including the transformation period, achieved superior economic results, albeit at discount rates that exceeded 1.24%. The conclusion was reached that, according to all economic criteria, uneven-aged mixed silver fir-beech management system is preferred compared with the pure even-aged silver fir management

PEDUNCULATE OAK (Quercus robur L.) TREES QUALITATIVE STRUCTURE AS A CRITERIA OF THE STAND REGENERATION PLANNING

Gospodarenje šumama hrasta lužnjaka opterećeno je pojavom propadanja i odumiranja stabala te danas predstavlja značajan gospodarski i ekološki problem u šumarstvu Hrvatske. Narušavanje strukture starijih i starih sastojina posljedično uzrokuje smanjenja kvalitativne (sortimentne) strukture drva, odnosno vrijednosti drvne zalihe sastojina. Prsni promjer srednjeg plošnog stabla sastojine (d_SPS) i udio obujma drva razreda kakvoće A i B (vABp) u ukupnom obujmu SPS hrasta u ovom radu izdvojene su kao zavisne varijable u postupku istraživanja multivarijatnog utjecaja skupina sastojinskih, stanišnih i gospodarskih čimbenika višefaktorskom analizom varijance na kvalitativnu (sortimentnu) strukturu preostalih stabala hrasta lužnjaka u starijim i starim lužnjakovim sastojinama srednje Posavine. S obzirom na rezultate varijabilnosti kvalitativne strukture, predloženi su modeli procjene strukture obujma drva po razredima kakvoće prema Hrvatskoj normi HRN EN 1361-1. Na iznimnu kvalitetu sastojina i potencijal staništa ukazuje aritmetički srednji prsni promjer SPS hrasta lužnjaka od 64 cm te sadržaj prosječno 35 % obujma drva kvalitativno svrstanih u A i B razrede kakvoće. Kompleksan utjecaj skupina sastojinskih i stanišnih varijabli na prsni promjer i kvalitetu SPS hrasta lužnjaka znatno je manje izražen od utjecaja skupine gospodarskih varijabli. Kvaliteta staništa i sklopljenost sastojine, kroz utjecaj na dužinu debla, čistoću od grana i dr., očekivano statistički značajno utječu na kvalitativnu strukturu stabala hrasta. Objašnjenost varijabiliteta obujma pojedinog razreda kakvoće drva izabranom jednadžbom kreće se u rasponu od 63,4 % za razred kakvoće C do 92,1 % za drvni ostatak (DO). Neovisno o deklarativno različitim uvjetima u kojima su se razvijale istraživane sastojine, preostala lužnjakova stabla ujednačene su i velike kvalitativne strukture, no vrijednost drvne zalihe značajno je smanjena uslijed smanjenja obrasta. U budućim postupcima planiranja gospodarenja uputno je pronalaziti i izdvajati strukturno očuvane i stabilne dijelove šume na kojima bi se akumulirao vrijednosni pri­rast s ciljem uspostavljanja ravnoteže u dobi sječe sastojina i unapređenju dobne strukture šuma hrasta lužnjaka.Pedunculate oak forest management is complicated by the appearance of tree dieback and nowadays represents the most significant economic and environmental problem in Croatian forestry. The consequences are evident through large economic losses amounting to 40 % of potential market value of the timber, stand value decrease due to minor stocking and weakening of beneficial functions of forests.Structure violation of the elderly and mature stands consequently causes a significant deviation from optimal, theoretical estimating models of timber quality. A more precise estimation of quality classes and stand structure quality and thus the value of its timber stock, allows efficient management planning towards primarily regeneration of forest (or stands) parts with most disrupted structure. In Croatia timber is traditionally classified by its purpose (e.g. Croatian standards HRN (1995)) as opposed to the newer standards (e.g. Croatian standards HRN EN 1361-1 (1999)) which are based on the Western European practice where timber is classified according to its quality, without prejudice of its purpose.Previous research into the possibility of forming patterns and finding the best model to evaluate the quality class structure suggest the limited use of certain models due to stratification of the sample according to the level of tree species, management class, silvicultural forest type, age class, cutting type, the revenue type, share of dieback trees, etc. This paper explored the factors influencing the qualitative (quality class) structure of the remaining trees in elderly and mature pedunculate oak stands of central Posavina. Based on results of the qualitative structure variability, habitat and economic variables, structure models were constructed to estimate the volume of quality classes according to Croatian standards EN 1361-1.Within the pedunculate oak management class in middle Posavina (size of 29 190 ha) randomly was chosen 37 stands older than 100 years with reduced stocking where was placed 146 circular plots with radius of 35 m. On average, the plots covered 5 pedunculate oak trees closest to the plot centre. According to Danhelovski method qualitative structure of selected observed trees was estimated and calculated. On the observed plots has been estimated a wide range of habitat, stand and economic variables (Table 1). Equalizing the volume of quality classes was conducted by quality formula (3) which is in previous studies (suitable function for equalizing the quality class volume depending on DHB) marked as suitable. Breast height diameter of mean tree (d_SPS) and the volume share of quality classes A and B (vABp) were chosen in this study as the dependent variables in the process of multivariable research influence of factor groups; stand, environmental and management factors by multifactorial analysis of variance.The total volume of sample trees of 3 964 m3 mostly constitutes quality class D (30 %) while the remaining three quality classes are equally represented,(about 20 %) (Table 1). The complex influence of stands and habitat group variables to breast height diameter of mean tree is much less important than the economic variables group (Tables 3 and 4). As expected, site index and canopy density significantly affect the qualitative structure of pedunculate oak trees through the length of the trunk, height of first branch and other factors (Table 3). Identified arithmetic mean tree breast height diameter (SPS) of pedunculate oak (64 cm) and an average content of 35 % volume of A and B quality classes (Table 2) indicates the exceptional quality of the stands. Explanation of the volume variability for each quality class by function (3) is in the range of 92.1 % for quality class DO to 63.4 % for quality class C (Table 5).Comparison of modelled and estimated quality class structure (Figure 2) indicates the acceptability of the selected models. The volume distribution per quality classes indicates homogeneity above DBH of 67.5 diameter class and pointing the fact that the oldest trees retain their quality (Figure 3) above DBH of 70 cm. The quality and tree value does not necessarily follow the stand value for the fact of constant dieback and sanitary cutting which declines stand stock and the volume proportion of pedunculate oak, and thus the value of the stands. In these circumstances it is necessary to find and isolate structurally maintained and stable forests parts where should be accumulated value increment in order to establish a balance at rotation period and improving the forest age structure

Status and challenges of small-scale private forest management in actual ecological and social circumstances : Croatia case study

Gospodarenje šumama u Hrvatskoj je pretežito koncentrirano i usmjereno prema šumama u državnom vlasništvu, koje je stoga obilježeno stalnošću i dosljednošću planiranja i provedbe postupaka gospodarenja, te se provode načela održivog gospodarenja na svim razinama. Nasuprot tomu, privatne šume su uslijed povijesnih okolnosti te male zastupljenosti i usitnjenosti bile značajno zapostavljene sve do nedavno. Stoga je cilj ovog rada analizirati i prikazati postojeća obilježja privatnih šuma, šumoposjeda i šumoposjednika, kao i okolnosti gospodarenja tj. institucionalnog i regulatornog okvira u kojemu se ono odvija.Površinski udio od 24% i drvnu zalihu od 156 m3/ha uz bogatstvo vrstama i razvojnim stadijima čini privatne šume vrlo vrijednim prirodnim resursom. Iako je posljednjih godina ostvaren značajni napredak, neriješeni imovinsko-pravni odnosi, nedorečen Zakonski okvir te nepovoljna sociološka obilježja šumoposjednika (velik udio starije populacije i niska razina obrazovanja) otežavaju daljnje unaprjeđenje gospodarenja.Za razliku od katastarske baze podataka anketni upitnici vrijedan su izvor informacija o obilježjima šumoposjeda i šumoposjednika, poglavito za znanstvena istraživanja. Prosječna obilježja šumoposjednika prikazana u ovome radu (prosječna dob od 60 godina i razmjerno niska razina obrazovanja) nisu ohrabrujuća. Međutim, ipak bi donošenje šumarskih politika trebalo biti utemeljeno na spoznajama o tipovima i stavovima šumoposjednika, posebno onih koji su spremni aktivno se baviti šumarstvom. Pri tome jasno treba razdvojiti šumoposjednika koji gospodari šumom i stavlja šumske proizvode na tržište (šumoposjednici upisani u Upisnik) i vlasnika sitnih šumskih čestica koji šumu u većoj ili manjoj mjeri koriste za vlastite potrebe.Poseban problem planiranja uravnoteženog i održivog gospodarenja je postojeći usporedni sustav planiranja i gospodarenja razdvojen prema vlasništvu. Objedinjavanjem svih javnih nadležnosti nad šumama u jedinstvenu instituciju uz ustrojavanje većeg broja šumskogospodarskih područja omogućilo bi ispunjavanje zahtjeva potrajnog gospodarenja i održivosti šuma uz ostvarivanje dugoročnih javnih interesa.Za učinkovitu i potpunu uspostavu sveobuhvatnog i potrajnog gospodarenja šumama potrebno je od strane svih dionika usvajanje spoznaja o specifičnostima gospodarenja privatnim šumama, uključujući i primjenu dobivenih rezultata provedenih znanstvenih istraživanja.Forest management in Croatia traditionally has been dominantly concentrated and directed toward state owned forests, thus it characterized with continuity and consistency of forest management planning and performance of management treatments, as well as fulfillment of principles of sustainable management on all levels. On the contrary, due to historic circumstances, small share and scattered fragmented forest distribution private forests was significantly uncared for management until not long ago. Thus, aim of this paper is to analyze and to present actual characteristics of private forests, forest estate and forest owners, as well as management circumstances namely institutional and legislative framework in which it is exists.Share of 24 % according to area and growing stock of 156 m3/ha with richness tree species and tree/stand developmental stages indicate on valuable natural forest resource in Croatia. Although during last years has achieved particular progress, existing property-juridical and land-register questions, unsuitable institutional framework and adverse socio-demographic characteristics of forest owners (large share of old population, low level of education) load with further improvements of private forest management.With absence of complete data base, results of researches and surveys are valuable information sources describing the private forest owner’s characteristics. In consideration on obtained results of average characteristics of forest owners (average age of 60 years, low education level) are not satisfactory, strategy and guidelines making should be based on knowledge of private forest owners preferences and types, especially of that which are active and which are ready to be active in forest management. Thereby, there is need to segregate forest owners which manage their forests and offer forest products on market (recorded in Register) from forest owners which owns small forest parcels and more or less use their forests for their own needs.Improvement of balanced and sustainable private forest management planing would be based on transformation of the existing parallel forest management planning system divided according to categories of forest property (state, private). By integration of all publc competences over forests within unique institution with establishment more forest management regions, would provide fullfilment of requirements of sustainable forest management and long-term public interests. An effective and comprehensive establishment of sustainable private forest management is based on adoptation of knowledge and private forest management particularities including actual results of relevant scientific researches, from the all copartners of the forest management system

Harmonised statistics and maps of forest biomass and increment in Europe.

peer reviewedForest biomass is an essential resource in relation to the green transition and its assessment is key for the sustainable management of forest resources. Here, we present a forest biomass dataset for Europe based on the best available inventory and satellite data, with a higher level of harmonisation and spatial resolution than other existing data. This database provides statistics and maps of the forest area, biomass stock and their share available for wood supply in the year 2020, and statistics on gross and net volume increment in 2010-2020, for 38 European countries. The statistics of most countries are available at a sub-national scale and are derived from National Forest Inventory data, harmonised using common reference definitions and estimation methodology, and updated to a common year using a modelling approach. For those counties without harmonised statistics, data were derived from the State of Europe's Forest 2020 Report at the national scale. The maps are coherent with the statistics and depict the spatial distribution of the forest variables at 100 m resolution

THE EFFECTS OF DIFFERENT STAND REGENERATION PLANNING ON MANAGEMENT AND PEDUNCULATE OAK FOREST DEVELOPMENT – A SMALL SIZE MANAGEMENT CLASS CASE STUDY

Planiranje budućeg gospodarenja šumama hrasta lužnjaka posebno je zahtjevno u uvjetima narušene dobne strukture šume, propadanja stabala i strukture sastojina. Izlučivanje površina (novih sastojina) s obzirom na strukturne značajke i pravodobna provedba obnove značajno je pitanje gospodarenja šumama hrasta lužnjaka. Stoga je u radu cilj istražiti učinke primjene dva suprotna pristupa rangiranja sastojina prema prioritetu za obnovu i intenzitetima obnove šume, na razvoj strukture sastojina, dobne i prostorne strukture šume, kao i na očekivano kretanje količine i vrijednosti budućih prihoda. Kao objekt istraživanja poslužila je stvarna šuma (uređajni razred hrasta lužnjaka) u gospodarskoj jedinici Opeke površine 429,4 ha (26 sastojina prosječne površine od 16,5 ha), sastavljena od sastojina starijih od 110 godina. Provedena je projekcija gospodarenja i prostorno-vremenskog razvoja regularne šume tijekom budućih četrnaest 10-godišnjih razdoblja (ophodnja 140 godina) pomoću računalnog programa SIMPLAG, te vrednovanje različitih pristupa gospodarenja na temelju usporedbi i odstupanja aktualnih od teoretskih kriterija gospodarenja. Rezultati su pokazali utjecaj intenziteta obnove šume i načina određivanja sastojina za obnovu:, (1) na razvoj prostorne i dobne strukture šume, 2) na kretanje i ukupne iznose etata te bruto i neto prihoda i na 3) drvne zalihe šume. Intenzivnom obnovom šume postigla bi se veća prosječna drvna zaliha šume, veći iznosi etata i prihodi, uz veliko odstupanje od teoretskih. Pristupom prioritetne obnove sastojina lošije strukture postigli bi se isto tako veći iznosi etata i prihoda uz manje odstupanje od teoretskih, što je u smislu potrajnosti gospodarenja prihvatljivije. Buduće gospodarenje istraživanom šumom temeljeno na postupnoj obnovi šume tijekom duljeg razdoblja, prioritetnom obnovom novoizlučenih površina do 5 ha na dijelovima postojećih sastojina lošije strukture, može se preporučiti s obzirom da bi taj pristup dugoročno vodio oblikovanju odgovarajuće prostorne i dobne strukture šume uz najveće ekološke i ekonomske učinke.Pedunculate oak forests in Croatia are characterized with an irregular age-class distribution (larg share of mature stands), pedunculate oak dieback and decreasing stand structure quality, as well as large sized stands and they spatial heterogenity (density of pedunculate oak). Future management and development of the forest depend on actual age-class structure, intensity and spatial-temporal dynamics of forest regeneration. Thereby, spatial dividing of an appropriate size areas (new stands) and defining priority of their regeneration over future periods, which should be based on an objective criteria (e.g. potential rent difference as a consequence of the decision of regeneration (prompt or adjournment) of a potentially mature pedunculate oak stands), is key question. Based on developed computer program application, paper aim is to research effects of two opposite approaches of regeneration priority stand ranking and different intensities of forest regeneration on: stands growth, development of age-class structure and spatial forest structure, as well as possible trends in amounts and values of future revenues. Object of the research is real even-aged forest (management class of pedunculate oak) in Opeke management unit. Area of the forest is 429.5 ha divided into 26 stands of average area of 16.5 ha. Youngest stand is 107 years old and the oldest is 185 years. There is large deviation between actual and theoretical age-class distribution of the forest (table 1). Projection of management and spatial-temporal development of the even-aged pedunculate oak forest over future fourteen 10-year periods (rotation) is performed by computer program SIMPLAG (Teslak i dr., 2012). Within "theoretical" intensity of regeneration (30 ha in 10-year regeneration area, 2–6 ha stand regeneration size, 250 m minimal distance between regenerated stands), and intensive regeneration (50 ha in 10-year regeneration area, 3–13 ha stand regeneration size, 250 m minimal distance between regenerated stands), there were two approaches of regeneration priority stand ranking: – stand regeneration ranking according to lowest potential rent difference (poor structure stand has highest regeneration priority – NSR); – stand regeneration ranking according to highest potential rent difference (well structure stand has highest regeneration priority – OSR) Different management approach validation is performed using comparison and deviation indices (actual vs. theoretical management criteria average deviation). Results showed that less intensive regeneration approach with appurtenant requirements would lead to development of an optimal forest structure as to larger number, smaller sized (5 ha average area), and more homogeneous stands (fig. 1a). Development of age-class forest structure has indirectly manifested in trends of average stand age (fig. 1b). An approach of intensive forest regeneration would result with fast decrease of average stand age, oscillating around theoretical stand age and never would achieve theoretical age-class structure. A question of maintenance and conservation of pedunculate oak stands for long period, up to stand age above 250 years, is very important, particular in a case of less intensive regeneration over long regeneration period of forest. Influence of forest regeneration intensity and approach of regeneration priority stand ranking on trends and total amont of forest growing stock, intermediate and regeneration fellings (fig. 2, tab. 2 and 3), as well as on value of fellings (fig. 3, tab. 2 and 3), has obtained. More intensive regeneration would result with larger average growing stock, total fellings and gross/net value of fellings, meanwhile with large deviations around theoretical models. Approach of priority regeneration of poor quality stands would achieve larger amounts of fellings and revenues too, but with less deviations, what is in terms of sustainability, more acceptable. Future forest management for the forest (and forests of such structure) based on gradually forest regeneration over longer period, by priority regeneration of areas up to 5 ha within poor quality structure parts of current forest stands (new stands), is recommended. This management approach would lead to forming of an appropriate spatial forest structure and development of a balanced age-class structure, with the highest ecological and economic effects

PEDUNCULATE OAK (Quercus robur L.) TREES QUALITATIVE STRUCTURE AS A CRITERIA OF THE STAND REGENERATION PLANNING

Gospodarenje šumama hrasta lužnjaka opterećeno je pojavom propadanja i odumiranja stabala te danas predstavlja značajan gospodarski i ekološki problem u šumarstvu Hrvatske. Narušavanje strukture starijih i starih sastojina posljedično uzrokuje smanjenja kvalitativne (sortimentne) strukture drva, odnosno vrijednosti drvne zalihe sastojina. Prsni promjer srednjeg plošnog stabla sastojine (d_SPS) i udio obujma drva razreda kakvoće A i B (vABp) u ukupnom obujmu SPS hrasta u ovom radu izdvojene su kao zavisne varijable u postupku istraživanja multivarijatnog utjecaja skupina sastojinskih, stanišnih i gospodarskih čimbenika višefaktorskom analizom varijance na kvalitativnu (sortimentnu) strukturu preostalih stabala hrasta lužnjaka u starijim i starim lužnjakovim sastojinama srednje Posavine. S obzirom na rezultate varijabilnosti kvalitativne strukture, predloženi su modeli procjene strukture obujma drva po razredima kakvoće prema Hrvatskoj normi HRN EN 1361-1. Na iznimnu kvalitetu sastojina i potencijal staništa ukazuje aritmetički srednji prsni promjer SPS hrasta lužnjaka od 64 cm te sadržaj prosječno 35 % obujma drva kvalitativno svrstanih u A i B razrede kakvoće. Kompleksan utjecaj skupina sastojinskih i stanišnih varijabli na prsni promjer i kvalitetu SPS hrasta lužnjaka znatno je manje izražen od utjecaja skupine gospodarskih varijabli. Kvaliteta staništa i sklopljenost sastojine, kroz utjecaj na dužinu debla, čistoću od grana i dr., očekivano statistički značajno utječu na kvalitativnu strukturu stabala hrasta. Objašnjenost varijabiliteta obujma pojedinog razreda kakvoće drva izabranom jednadžbom kreće se u rasponu od 63,4 % za razred kakvoće C do 92,1 % za drvni ostatak (DO). Neovisno o deklarativno različitim uvjetima u kojima su se razvijale istraživane sastojine, preostala lužnjakova stabla ujednačene su i velike kvalitativne strukture, no vrijednost drvne zalihe značajno je smanjena uslijed smanjenja obrasta. U budućim postupcima planiranja gospodarenja uputno je pronalaziti i izdvajati strukturno očuvane i stabilne dijelove šume na kojima bi se akumulirao vrijednosni pri­rast s ciljem uspostavljanja ravnoteže u dobi sječe sastojina i unapređenju dobne strukture šuma hrasta lužnjaka.Pedunculate oak forest management is complicated by the appearance of tree dieback and nowadays represents the most significant economic and environmental problem in Croatian forestry. The consequences are evident through large economic losses amounting to 40 % of potential market value of the timber, stand value decrease due to minor stocking and weakening of beneficial functions of forests.Structure violation of the elderly and mature stands consequently causes a significant deviation from optimal, theoretical estimating models of timber quality. A more precise estimation of quality classes and stand structure quality and thus the value of its timber stock, allows efficient management planning towards primarily regeneration of forest (or stands) parts with most disrupted structure. In Croatia timber is traditionally classified by its purpose (e.g. Croatian standards HRN (1995)) as opposed to the newer standards (e.g. Croatian standards HRN EN 1361-1 (1999)) which are based on the Western European practice where timber is classified according to its quality, without prejudice of its purpose.Previous research into the possibility of forming patterns and finding the best model to evaluate the quality class structure suggest the limited use of certain models due to stratification of the sample according to the level of tree species, management class, silvicultural forest type, age class, cutting type, the revenue type, share of dieback trees, etc. This paper explored the factors influencing the qualitative (quality class) structure of the remaining trees in elderly and mature pedunculate oak stands of central Posavina. Based on results of the qualitative structure variability, habitat and economic variables, structure models were constructed to estimate the volume of quality classes according to Croatian standards EN 1361-1.Within the pedunculate oak management class in middle Posavina (size of 29 190 ha) randomly was chosen 37 stands older than 100 years with reduced stocking where was placed 146 circular plots with radius of 35 m. On average, the plots covered 5 pedunculate oak trees closest to the plot centre. According to Danhelovski method qualitative structure of selected observed trees was estimated and calculated. On the observed plots has been estimated a wide range of habitat, stand and economic variables (Table 1). Equalizing the volume of quality classes was conducted by quality formula (3) which is in previous studies (suitable function for equalizing the quality class volume depending on DHB) marked as suitable. Breast height diameter of mean tree (d_SPS) and the volume share of quality classes A and B (vABp) were chosen in this study as the dependent variables in the process of multivariable research influence of factor groups; stand, environmental and management factors by multifactorial analysis of variance.The total volume of sample trees of 3 964 m3 mostly constitutes quality class D (30 %) while the remaining three quality classes are equally represented,(about 20 %) (Table 1). The complex influence of stands and habitat group variables to breast height diameter of mean tree is much less important than the economic variables group (Tables 3 and 4). As expected, site index and canopy density significantly affect the qualitative structure of pedunculate oak trees through the length of the trunk, height of first branch and other factors (Table 3). Identified arithmetic mean tree breast height diameter (SPS) of pedunculate oak (64 cm) and an average content of 35 % volume of A and B quality classes (Table 2) indicates the exceptional quality of the stands. Explanation of the volume variability for each quality class by function (3) is in the range of 92.1 % for quality class DO to 63.4 % for quality class C (Table 5).Comparison of modelled and estimated quality class structure (Figure 2) indicates the acceptability of the selected models. The volume distribution per quality classes indicates homogeneity above DBH of 67.5 diameter class and pointing the fact that the oldest trees retain their quality (Figure 3) above DBH of 70 cm. The quality and tree value does not necessarily follow the stand value for the fact of constant dieback and sanitary cutting which declines stand stock and the volume proportion of pedunculate oak, and thus the value of the stands. In these circumstances it is necessary to find and isolate structurally maintained and stable forests parts where should be accumulated value increment in order to establish a balance at rotation period and improving the forest age structure

Stand Regeneration Characteristics of Beech and Fir Forests in Gorski Kotar Region

Background and Purpose: Beech-fir forests cover about 13% of forest land in Croatia, thus being a significant forest resource that is dominantly managed by uneven-aged selection management system. Continuous and successful regeneration is an essential prerequisite for this kind of forest management. Therefore updated and sound information on the present state of regeneration is important, especially in the context of climate change and the actual structure of beech and fir forests. The aim of this paper is to present and analyse current state of regeneration in beech and silver fir forests of Gorski kotar region, with regard to forest ownership (management model), forest communities and habitat characteristics. Materials and Methods: Field measurement has been done on 313 plots in the beech and fir forests of Gorski kotar region, Croatia. The assessment of regeneration was based on measurement of trees ranging from 0 to 10 cm dbh (species, number of trees, average height) and also the estimation of seedlings up to 1.30 m high (regenerated area in 10% classes, the share of tree species, the origin of stand establishment, regeneration quality). Results: Attributes like the success of regeneration, the structure of seedlings by species and the recruitment of saplings were analysed with regards to ownership, forest communities and the aim of forest management. The results indicate poor incidence of regeneration especially of silver fir (more than 50% percent of field plots with no regeneration). Silver fir saplings (height>1.3 m, dbh ≤10 cm) are registered on 9% of plots, average number being only 165 per ha (all species together 2044 per ha). The estimated average share of the regenerated area is 16.3% of total forest area, contributed by 5.2% of conifers and 3.8% silver fir. A total of 14 tree species were recorded on regenerated areas, clearly dominated by broadleaves, especially beech (over 50%). Conclusions: Significant differences in regeneration attributes were proven by ANOVA between ownership categories, forest communities and habitat characteristics. In order to get better insight on the structure of regeneration, it is recommended to improve future assessment by establishing special sub-plots for measurement of seedlings by species

Harmonised statistics and maps of forest biomass and increment in Europe

Abstract Forest biomass is an essential resource in relation to the green transition and its assessment is key for the sustainable management of forest resources. Here, we present a forest biomass dataset for Europe based on the best available inventory and satellite data, with a higher level of harmonisation and spatial resolution than other existing data. This database provides statistics and maps of the forest area, biomass stock and their share available for wood supply in the year 2020, and statistics on gross and net volume increment in 2010–2020, for 38 European countries. The statistics of most countries are available at a sub-national scale and are derived from National Forest Inventory data, harmonised using common reference definitions and estimation methodology, and updated to a common year using a modelling approach. For those counties without harmonised statistics, data were derived from the State of Europe’s Forest 2020 Report at the national scale. The maps are coherent with the statistics and depict the spatial distribution of the forest variables at 100 m resolution