Circular Sample Plot Size Impact on Structure Elements Estimation in Selected Pedunculate Oak Stands

Uređajna izmjera šuma u Hrvatskoj najčešće se vrši na privremenim jedinicama uzorka, kao što su primjerni krugovi ili primjerne pruge. U sastojinama koje se u prvom polurazdoblju propisuju za sječu glavnog prihoda, prema Pravilniku o uređivanju šuma (Narodne novine 141/08) mjere se sva stabla, osim u panjačama. U radu se na uzorku od 86 primjernih ploha kružnog oblika, postavljenih na području g.j. Repaš-Gabajeva Greda, šumarije Repaš, UŠP Koprivnica, promatra promjena osnovnih taksacijskih elemenata (broj stabala – N, temeljnica–G, volumen–V) smanjenjem polumjera kruga. Plohe su postavljene u sastojinama od III. do VII. dobnog razreda. Svakom je stablu određen položaj u prostoru, pa se smanjivanje polumjera kružne plohe vršilo simulacijom iz baze podataka. Za procijenjene strukturne elemente izračunate su osnovne statističke veličine, koeficijent varijacije (CV) i preciznost procjene (SP). Rezultati su pokazali kako se kreću vrijednosti procjene strukturnih elemenata i statističkih veličina uz smanjenje polumjera kruga. Za III., IV. i VII. dobni razred, zbog malog broja izmjerenih ploha nije bilo moguće donijeti čvrste zaključke. U V. i VI. dobnom razredu rezultati su pokazali da se smanjenjem polumjera kružne plohe za 10 m vrijednosti procjene strukturnih elemenata ne mijenjaju značajno. Stoga u V. dobnom razredu kod danih sastojinskih uvjeta nije potrebno niti opravdano vršiti izmjeru na kružnim plohama polumjera većeg od 15 m, a u VI. dobnom razredu 20 m. Povećanjem broja ploha u III., IV. i V. dobnom razredu te ispitivanjem kretanja procjene strukturnih elemenata uz manje polumjere kružne plohe od onih ispitanih u ovom radu, moglo bi se doći do najmanjeg polumjera kružne plohe koji osigurava pouzdanu i preciznu procjenu sastojinskih elemenata.Data collecting in forest inventory in Croatia are carried out on a temporary sample plots (circles or strips). In this article, sample of 86 circular plots established in Repaš-Gabajeva Greda management unit (Fig. 1), Repaš forest office, Koprivnica regional forest office, is used to see how the basic structural elements (stem number – N, basal area – G and stand volume –V) are changing when the sample plot radius is decreasing. Research area is typical lowland pedunculate oak and hornbeam stand (Carpino betuli-Quercetum roboris (Anić 1959) Rauš 1969. Sample plots covered the whole management unit area and stands older than 40 years, from 3rd to 7th age class. Sample units were circular, with radius 15 to 30 m, bigger than in regular forest inventory (Table 1) which are usually 12,62 m and 18 m in radius. All trees above 10 cm in dbh within circular plot were measured. Plot center was marked with iron bolt below ground level. Position of each tree is determined with distance and angle from plot center. Haglof caliper was used to measure two dbh of each tree. Total tree height was taken with Suunto hypsometer. Data collected in a field, were entered to database created in Microsoft Access. For each plot, number of trees per hectare, basal area per hectare, and volume per hectare, were calculated, separately for tree species and total. These basic structure elements were calculated for different plot sizes, lower than taken in field. It has been done using database queries, thanks to recorded position of each tree. For a particular criteria (distance from plot center), only trees that are within required radius were selected. In 3rd and 4thage class, plot radius from 5 to 15 m, with 1 m step, is used to calculate structure elements (Table 2). In 5thage class, examined plot radius range was 15–25 m, and in 6thand 7thage class 20–30 m (Table 3). Calculated elements were examined with simple statistical analyses in order to get variation coefficient (CV), and precision (SP). The results showed that in 3rd, 4thand 7thage class there is not enough sample plots to bring conclusions because variation coefficient values are high and precision is at poor level. (Fig. 3–8). In 5th and 6th age class for all examined plot radii, estimated precision of basal area and stand volume is better than 5 % (Fig.7, Fig.8), and variation coefficient is in range of 15,3–26,4 % (Fig. 4, Fig. 5). Stem number estimation shows precision of 5,3–6,0 % (Fig. 6). In given research area and stand conditions, conclusions are: – in 3rd, 4thand 7thage class variability in small amount of sample plots is too high to bring resolute conclusion – regarding to variation coefficient and estimation precision values, there is no need to use sample plot radius greater than 15 m in 5thage class, and 20 m in 6thage class - with more sample plots in 3rd, 4thand 7thage class, and use of lower sample plot sizes in 5thand 6thage class, optimal plot radius that gives reliable and precise stand structure elements estimation could be reached

Circular Sample Plot Size Impact on Structure Elements Estimation in Selected Pedunculate Oak Stands

Uređajna izmjera šuma u Hrvatskoj najčešće se vrši na privremenim jedinicama uzorka, kao što su primjerni krugovi ili primjerne pruge. U sastojinama koje se u prvom polurazdoblju propisuju za sječu glavnog prihoda, prema Pravilniku o uređivanju šuma (Narodne novine 141/08) mjere se sva stabla, osim u panjačama. U radu se na uzorku od 86 primjernih ploha kružnog oblika, postavljenih na području g.j. Repaš-Gabajeva Greda, šumarije Repaš, UŠP Koprivnica, promatra promjena osnovnih taksacijskih elemenata (broj stabala – N, temeljnica–G, volumen–V) smanjenjem polumjera kruga. Plohe su postavljene u sastojinama od III. do VII. dobnog razreda. Svakom je stablu određen položaj u prostoru, pa se smanjivanje polumjera kružne plohe vršilo simulacijom iz baze podataka. Za procijenjene strukturne elemente izračunate su osnovne statističke veličine, koeficijent varijacije (CV) i preciznost procjene (SP). Rezultati su pokazali kako se kreću vrijednosti procjene strukturnih elemenata i statističkih veličina uz smanjenje polumjera kruga. Za III., IV. i VII. dobni razred, zbog malog broja izmjerenih ploha nije bilo moguće donijeti čvrste zaključke. U V. i VI. dobnom razredu rezultati su pokazali da se smanjenjem polumjera kružne plohe za 10 m vrijednosti procjene strukturnih elemenata ne mijenjaju značajno. Stoga u V. dobnom razredu kod danih sastojinskih uvjeta nije potrebno niti opravdano vršiti izmjeru na kružnim plohama polumjera većeg od 15 m, a u VI. dobnom razredu 20 m. Povećanjem broja ploha u III., IV. i V. dobnom razredu te ispitivanjem kretanja procjene strukturnih elemenata uz manje polumjere kružne plohe od onih ispitanih u ovom radu, moglo bi se doći do najmanjeg polumjera kružne plohe koji osigurava pouzdanu i preciznu procjenu sastojinskih elemenata.Data collecting in forest inventory in Croatia are carried out on a temporary sample plots (circles or strips). In this article, sample of 86 circular plots established in Repaš-Gabajeva Greda management unit (Fig. 1), Repaš forest office, Koprivnica regional forest office, is used to see how the basic structural elements (stem number – N, basal area – G and stand volume –V) are changing when the sample plot radius is decreasing. Research area is typical lowland pedunculate oak and hornbeam stand (Carpino betuli-Quercetum roboris (Anić 1959) Rauš 1969. Sample plots covered the whole management unit area and stands older than 40 years, from 3rd to 7th age class. Sample units were circular, with radius 15 to 30 m, bigger than in regular forest inventory (Table 1) which are usually 12,62 m and 18 m in radius. All trees above 10 cm in dbh within circular plot were measured. Plot center was marked with iron bolt below ground level. Position of each tree is determined with distance and angle from plot center. Haglof caliper was used to measure two dbh of each tree. Total tree height was taken with Suunto hypsometer. Data collected in a field, were entered to database created in Microsoft Access. For each plot, number of trees per hectare, basal area per hectare, and volume per hectare, were calculated, separately for tree species and total. These basic structure elements were calculated for different plot sizes, lower than taken in field. It has been done using database queries, thanks to recorded position of each tree. For a particular criteria (distance from plot center), only trees that are within required radius were selected. In 3rd and 4thage class, plot radius from 5 to 15 m, with 1 m step, is used to calculate structure elements (Table 2). In 5thage class, examined plot radius range was 15–25 m, and in 6thand 7thage class 20–30 m (Table 3). Calculated elements were examined with simple statistical analyses in order to get variation coefficient (CV), and precision (SP). The results showed that in 3rd, 4thand 7thage class there is not enough sample plots to bring conclusions because variation coefficient values are high and precision is at poor level. (Fig. 3–8). In 5th and 6th age class for all examined plot radii, estimated precision of basal area and stand volume is better than 5 % (Fig.7, Fig.8), and variation coefficient is in range of 15,3–26,4 % (Fig. 4, Fig. 5). Stem number estimation shows precision of 5,3–6,0 % (Fig. 6). In given research area and stand conditions, conclusions are: – in 3rd, 4thand 7thage class variability in small amount of sample plots is too high to bring resolute conclusion – regarding to variation coefficient and estimation precision values, there is no need to use sample plot radius greater than 15 m in 5thage class, and 20 m in 6thage class - with more sample plots in 3rd, 4thand 7thage class, and use of lower sample plot sizes in 5thand 6thage class, optimal plot radius that gives reliable and precise stand structure elements estimation could be reached

Photogrammetric estimates of stand volume in pedunculate oak stands of the Pokupsko basin

U radu je dodatno istražena i evaluirana točnost fotogrametrijske procjene volumena na razini sastojine. Konkretno, na području šuma hrasta lužnjaka Pokupskog bazena (g.j. Jastrebarski lugovi) testirana je mogućnost korištenja fotogrametrijske metode bazirane na postojećim i lako dostupnim podacima (aerosnimke, digitalni model reljefa, podaci osnove gospodarenja) kao i postojećih fotogrametrijskih modela procjene sastojinskog volumena izrađenih za šume hrasta lužnjaka Spačvanskog bazena. Iz aerosnimaka i digitalnog modela reljefa izrađen je digitalni model visine krošanja (DMVK) prostorne rezolucije 5 m. Iz DMVK-a su dobiveni metrički podaci, koji su potom korišteni kao nezavisne varijable u modelima procjene volumena sastojine. Uspoređena je točnost procjene izvornih modela izrađenih za područje Spačvanskog bazena (SB modeli) te istih modela, ali s naknadno procijenjenim lokalnim parametrima za područje Pokupskog bazena (PB modeli). Fotogrametrijski procijenjeni volumeni validirani su s volumenom sastojina iz osnove gospodarenja. Dobiveni rezultati ukazuju na značajno poboljšanje točnosti fotogrametrijske procjene volumena kod PB modela u odnosu na SB modele. Korištenjem izvornih SB modela, volumen sastojine procijenjen je s korijenom srednje kvadratne pogreške od 18,47%, dok je korištenjem dodatno parametriziranih PB modela volumen procijenjen s pogreškom od 12,03%. U ovom radu prikazana fotogrametrijska metoda procjene volumena sastojina ne može zamijeniti klasične terenske metode za potrebe uređajne inventure šuma, međutim, budući da ne zahtijeva dodatna terenska mjerenja, već se u potpunosti bazira na postojećim podacima (aerosnimke, DMR, podaci osnove gospodarenja), a uz to pruža i zadovoljavajuću točnost, može poslužiti kao učinkovita i financijski isplativa metoda u slučajevima kada je u vrlo kratkom vremenu potrebno provesti inventuru nekog većeg šumskog područja.The application of digital aerial photogrammetry in forest inventory has been in the focus of a number of studies during the last decade (White et al. 2016, Goodbody et al. 2019). The results were tested and evaluated mostly on plot-level, and less often on stand-level (Bohlin et al. 2012, Rahlf et al. 2014, Gobakken et al. 2015, Pitt et al. 2015, Stepper et al. 2015, Puliti et al. 2016, Balenović et al. 2017, Iqbal et al. 2019). In almost all studies, a classic Area-Based Approach (ABA) which includes modelling at plot-level and ‘wall-to-wall’ mapping to estimate forest variables at stand-level were applied. A somewhat different ABA approach which implies direct modelling and estimation at stand-level were proposed by Balenović et al. (2017). This new approach, hereinafter referred to as Stand-Based Approach (SBA), is based on existing and easily available photogrammetric materials and data (aerial images from regular national topographic surveys, official national digital terrain data) as well as on data from existing forest management plans. The main precondition for the SBA method application is the approximate time coincidence between the time of aerial images acquisition and the time of the field data collection for the forest management plan generation. Similar to classical ABA, SBA also requires models (equations) for forest variable estimations. However, in SBA case, models are developed on the certain number of stands (subcompartments) of similar structural characteristics (e.g. forest management classes). In SBA, independent variables are metric stand-level data obtained from aerial images and its product (normalized point clouds or canopy height models), while reference (modelling or validation) data are obtained from regular forest management plans. Compared to classical ABA, SBA does not require additional field measurements, and therefore presents a fast and cost-effective alternative to ABA. An additional assumption is that models developed for the certain area can be applied for other forest areas with similar forest characteristics. This work presents the continuation of previous study (Balenović i dr. 2017) with the aim to additionally test the effectiveness and accuracy of SBA method. More precisely, SBA method and existing models of stand volume estimation originally developed for lowland pedunculate oak (Quercus robur L.) of Spačva basin forest complex (Eastern Croatia) were tested in pedunculated oak forest of Pokupsko basin forest complex (Central Croatia). A total of 87 even-aged pedunculate oak forest stands of Jastrebarski lugovi management unit were included in this study (Figure 1, Table 1). Photogrammetric data (aerial images, digital terrain data) were provided by the Croatian State Geodetic Administration, and were used to generate Digital Surface Model (DSM) and Digital Terrain Model (DTM). A raster Canopy Height Model (CHM) of 5 m resolution was generated by subtracting DTM from DSM (Figure 2). Metrics extracted from CHM for each stand and used for stand-level volume estimation are presented in Table 2. Equations (1) and (2) present photogrammetric models for stand-level volume estimation. A more detailed description of the models can be found in Table 3. SB-1 and SB-2 models consist of independent variables and parameters (regression constant and coefficients) originally developed for the Spačva basin area (Table 4). PB-1 and PB-2 models consisted of the same variables as SB-1 and SB-2 models, but their parameters were developed for the present study area (Pokupsko basin) (Table 4). All models were validated using the reference stand volume from the forest management plan. SB-1 and SB-2 models were validated using the entire dataset (87 stands), whereas PB-1 and PB-2 models were validated using the randomly selected 29 stands (other 58 stands were used for parameters estimation). According to validation results (Table 2, Figure 3), PB models showed considerably greater performance than SB-models. Compared to SB-1 model, PB-1 model achieved 11% higher R2adj values, for 3,92% MD% values (absolute), and for 6,44% higher RMSE% values. Also, the results showed that the inclusion of stand age (SA) as an additional predictor in SB-2 and PB-2 models did not contribute significantly on model performance. All models showed a similar trend (Figure 3), i.e. volume in stands with lover volume values were overestimated, while in stands with higher volume values were underestimated. However, overestimations (&8776; 8,5%) using SB models were considerably greater than underestimations (&8776; -4%) using PB models. Differences in SB and PB models performance are probably due to differences in stand and site characteristics between two forest areas (Spačva basin and Pokupsko basin). The obtained results suggest that the model with independent variables (Equation 1) originally developed for Spačva basin area can be used for Pokupsko basin and other areas with similar forest characteristics, but local model parameters have to be estimated in order to increase estimation accuracy. It has to be emphasized that the photogrammetric method tested in this paper can not replace the conventional field methods in regular forest inventory. However, its application is based on existing and easily available data (aerial images from regular topographic surveys, official DTM, forest management plan) and does not require additional field measurements and therefore present effective and low-cost solution when in a very short period large areas have to be inventoried. Further research should be focused on other important forest variables (e.g. mean stand height, mean stand diameter, basal area, stand density, biomass, etc.) and different forest types

Spatial Structure Indices of Mature Pedunculate Oak Stands in NW Croatia

Background and Purpose: In order to potentiate a valid comparison of forest stands, numerous indices were developed to express forest structure numerically. Each of those indices described a specific measured or calculated value. In the present study, three of the stand structure indicators, dependent on tree distance, were used: the aggregation index of Clark and Evans, the species mingling index and the diameter differentiation index. The objectives of this study were: to obtain further information about forest structure using the selected indices and to discover any limitations that the implemented indices might display. Materials and Methods: Mature pedunculate oak stands were selected as objects of the study, all located within the “Repaš – Gabajeva Greda” forest management unit, the Forest Administration of Koprivnica. The stands were aged 75 to 132 years. A systematic 500 m grid of 45 circle sample plots was established. The sample plot radius was 15, 25 or 30 meters, depending on the stand\u27s age. In 2001, the DBH (diameter at breast height) and tree positions in regard to the centre of a plot were measured on each sample plot. The mutual distances between trees were calculated, as well as the values of the three selected stand structure indices. The two procedures of the aggregation index of Clark and Evans were calculated for all 45 sample plots. In the first case only the pedunculate oak trees were observed, and in the other all trees on the plot. The species mingling index and the diameter differentiation index were calculated for each tree in two procedures: in relation to three and four nearest neighbouring trees. The plot/stand totals were managed as the average index of individual trees. Results: Values of the aggregation index of Clark and Evans after all trees have been observed were from 0.89 to 1.28, which indicated a random distribution of trees. In case of considering only pedunculate oak trees, the index of the plots was 1.02 to 1.51. This indicated a tendency to a regular distribution of trees. The species mingling index that considered three nearest neighbouring trees was 0.395 to 0.620. When observing four nearest neighbouring trees, the index values showed slight decreases in all age classes. The diameter differentiation index (0.407-0.424) when three or four nearest neighbour trees were taken into account, showed almost the same differentiation in the 5th, 6th and 7th age class. Conclusion: Though they contained the component of distance between the trees and were based on individual trees parameters, the three analysed stand structure indicators were a useful tool in further categorizing of forest stands

Height to Crown Base Modelling for the Main Tree Species in an Even-Aged Pedunculate Oak Forest: A Case Study from Central Croatia

The height to crown base (hcb) is a critical measure used in many investigations as an input variable to investigate the vigour of the stands, the social position of the trees, and to evaluate the behaviour of forest fires, among other uses. Though measuring height-related variables in the field is always time-consuming, the foremost benefits offered by modelling hcb are that it permits to generalize and average a very uneven attribute and, furthermore, provides insights about which tree and stand variables have a significant impact on hcb. However, there are many species in which models of the crown base height have not been developed in Croatia. The objective of this research was to develop a height to base crown model for each of the main species present in the two-layered mixed stands of this study. According to previous investigations, logistic models provide the highest precision and require the lowest inventory cost owing to less frequent measurements. Tree- and plot-level variables with distance-independent competition indexes were studied in the fitting model. In this research, we obtained models for the main stand species: Acer campestre (root mean squared error (RMSE) = 2.28 m, R2 = 82.80%); Alnus glutinosa (RMSE = 1.78 m, R2 = 85.36%); Carpinus betulus (RMSE = 2.47 m, R2 = 67.55%); Fraxinus angustifolia (RMSE = 2.46 m, R2 = 82.45%); Quercus robur (RMSE = 2.60 m, R2 = 80.57%); Tilia sp. (RMSE = 2.01 m, R2 = 89.07%); and Ulmus laevis (RMSE = 1.71 m, R2 = 92.42%). The combination of the total height, tree, and plot-level variables with distance-independent competition indexes contributed to the prediction accuracy of proposed model significantly

Forest biomass and sequestered carbon estimation according to main tree components on the forest stand scale

Background and Purpose: The estimation of forest woody biomass has a significant role in forestry due to several reasons. One of the reasons is that good woody biomass estimation is important for the planning of forest woody assortments production, for main commercial roundwood assortment and for assortments like »waste wood« or »recovered wood« as a potential for electricity (heat) generation (firewood, wood bricks, wood pellets etc.). Economic and political meaning of woody biomass estimation is important to know forest biomass resources in the country and present these facts to international institutions or in treaties as needed. The estimation is also important for strategic planning of the use of renewable energy sources from woody biomass. On the other hand, estimation of the carbon content in forest woody biomass has importance in global climatemitigation policy and processes (Kyoto- and post-Kyoto period). The purpose of this paper is to present methodology applied for estimation of forest woody biomass and its carbon content according to main tree components, on the forest stand scale. Material and Methods: As research area, two representative Croatian forest communities/stands were selected. The one represents flooded lowland pedunculate oak forest of Pokupski Basin, and the other represents mountain fir-beech forest of the Gorski Kotar region. Emphasis in the paper is on themethodology which was developed for the purpose of research. The methods applied in this study consist of: a) dendrometrical measurements on selected forest stands (research sites), b) sampling of main tree components and sample analyses in laboratory, and c) calculation of forest woody biomass and its carbon content according to main tree components. Results: General result of the laboratory analyses of the samples of main tree componets is that the carbon content in biomass was around 50,0% of the dry matter of a component. In line with volume allocation of main tree components are the biomass of tree components and the content of carbon sequestered in these components. Stem had the largest share in total tree biomass while foliage or needle biomass had the smallest share. The shares of main tree components in total biomass of the tree depend on morphology each of tree species. Conclusion: This research was a pilot and pioneering research of forest biomass in Croatian forestry, and it should be continued to acquire better knowledge of relations in forest woody biomass in main forest communities in Croatia

Geospatial analysis of the state of the Marjan Forest Park based on photogrammetric data of the unmanned aerial vehicle

Tijekom 2017. godine u Park šumi Marjan zamijećeno je intenzivno sušenje stabala alepskog bora (Pinus halepensis Mill.) uzrokovano mediteranskim potkornjakom (Orthotomicus erosus Woll.) koje se je intenziviralo i kulminiralo u 2018. i 2019. godini. S ciljem uklanjanja suhih i zaraženih stabala te sprječavanja daljnjeg širenja uzročnika i propadanja stabala, tijekom 2019. godine provedena je sanitarna sječa. Kako bi se dobio brz i detaljan uvid u stanje vegetacije Park šume Marjan, neposredno nakon obavljenih sanitarnih sječa, provedeno je snimanje bespilotnom letjelicom korištenjem klasične fotogrametrijske kamere te multispektralne kamere. Glavni cilj je bio dobiti ‘nulto stanje’ vegetacije koje će predstavljati temelj za uspostavu daljnjeg monitoringa i izvođenje pravovremenih preventivnih stručnih aktivnosti, a u svrhu očuvanja Park šume Marjan. Na temelju snimaka bespilotne letjelice vrlo visoke prostorne i spektralne razlučivosti izrađen je niz fotogrametrijskih i geoinformacijskih proizvoda koji su korišteni za detaljne geoprostorne analize stanja šumskog pokrova Park šume Marjan nakon napada potkornjakom te provedenih zahvata sanitarne sječe. Istraživanje je potvrdilo veliki potencijal bespilotnih letjelica i korištenih senzora za dobivanje kvalitetnih i pouzdanih informacija o stanju šuma u vrlo kratkom vremenu s relativno malih površina. Utvrđena je da zadovoljavajuća pokrovnost površine Park šume Marjan s vegetacijom iznad 5 m visine (45%). Međutim, zabrinjavajuće je mali udio vegetacije u rasponu od 2 – 5 m visine, a koja bi u bliskoj budućnosti trebala preuzeti ulogu visoke vegetacije (nadstojne etaže). Nadalje, detektirane su i izdvojene dvije ‘žarišne’ površine (13,7 ha) koje imaju najveće udjele otvorenih površina (visinska kategorija 0.4) in time of UAV survey (August 2019). Visual interpretation of multispectral images revealed a total of 491 remaining dry and chlorophyll-deficient trees. Since these trees are precisely spatially defined, they should be easily find in the field and removed by sanitary felling

Review of nonmarket forest goods and services evaluation methods

Background and Purpose: Natural resource systems that are commercially exploitable, such as forests, are valued by using many different factors. Policy makers and other decision makers must choose between scenarios in which there can be clear market values with easy to document influences on economy or scenarios in which the value is placed on difficult to document factors, such as the importance of natural systems, forest services without market values, and the benefits to human wellbeing. Several methods are described in this paper for documenting the non-market values that forest goods and services provide. We discuss different methods and assessment tools that provide different types of information, quantitative and qualitative, with respective strengths and weaknesses from varied scientific and decision-support perspective. In an attempt to provide scientists with different views and ideas, as well as planners and managers with a general appreciation of methods and their application, we have included selected examples that influence policy and/or management practices. Material and Methods: Most of the material has been developed based on a number of basic text books describing evaluation methods from the perspective of development and grounded in economical theory with a wide range of application. The second part has been developed from a list of references dealing with application in European countries and enriched with details and examples from documents based on seventeen country reports. The structure of those country reports was predefined, discussed, harmonized and completed by a group of scientists and professionals involved in COST action E-33, »Forest for recreation and tourism.« Evaluation methods related to forest goods and services were described from theoretical and practical viewpoints with emphasis on their applicability to a specific type of research. Results and Conclusion: Nonmarket values of forest goods and services can be estimated in a number of different ways. The methods can be divided into two basic categories: first, based on market prices, and second, based on non-market evaluation. Our focus is on the second strategy where the market prices are not known. Further division of this method goes in two broad categories according to the nature of the data generated for modelling and estimation: (a) »stated preference methods« where individuals’ preferences are not observed but rather stated, and (b) »revealed preference methods« where we can observe people acting in real-world settings where people live with the consequences of their choices.The most widely used method for valuing natural resources is the contingent valuation (CV) method. Choice experiments (CE) and hedonic pricing (HP) methods have been included in far fewer empirical studies, but the application of these methods has passed the demonstration stage. We also discuss the newly developed methods of benefit transfer and meta-analysis which use values, functions, and other descriptions from other studies to evaluate natural resources

Quality assessment of high density digital surface model over different land cover classes

Background and Purpose: Recent research on generation of digital surface models (DSMs) using image matching methods revealed a great potential of DSM application in forestry, especially in forest inventory. However, research dealing with DSM generation from digital aerial images are still lacking in Croatia. Therefore, the main objective of this study was to present the workflow for generating high density DSM from colour infrared (CIR) digital stereo aerial images using area-based image matching algorithm. Materials and Methods: The high density DSM was generated from colour infrared digital aerial stereo images using Dense DTM algorithm of PHOTOMOD software - an area-based image matching algorithm which operates on the principle of cross-correlation approach. To evaluate the quality of the generated DSM, an agreement assessment with manual stereo measurements was conducted over three different land cover classes (forests, shrubs, grasslands) using the same images as for DSM generation. Results: The good vertical agreement between the generated DSM and stereo measurement was achieved for all three land cover classes present at the research area. The highest vertical agreement was obtained for the grassland land cover class (RMSE=0.36), slightly lower for forest (RMSE=0.62), whereas the lowest vertical agreement was obtained for shrub land cover class (RMSE=0.83). Conclusions: The results of this research are very promising and suggest that the high density DSM generated from digital aerial stereo images and by using the proposed methodology has the potential to be used in forestry, primarily in forest inventory. Therefore, further research should be focused on generation of CHM by subtracting available DTM from the high density DSM and on the examination of its potential for deriving various forest attributes

Review of nonmarket forest goods and services evaluation methods

Background and Purpose: Natural resource systems that are commercially exploitable, such as forests, are valued by using many different factors. Policy makers and other decision makers must choose between scenarios in which there can be clear market values with easy to document influences on economy or scenarios in which the value is placed on difficult to document factors, such as the importance of natural systems, forest services without market values, and the benefits to human wellbeing. Several methods are described in this paper for documenting the non-market values that forest goods and services provide. We discuss different methods and assessment tools that provide different types of information, quantitative and qualitative, with respective strengths and weaknesses from varied scientific and decision-support perspective. In an attempt to provide scientists with different views and ideas, as well as planners and managers with a general appreciation of methods and their application, we have included selected examples that influence policy and/or management practices. Material and Methods: Most of the material has been developed based on a number of basic text books describing evaluation methods from the perspective of development and grounded in economical theory with a wide range of application. The second part has been developed from a list of references dealing with application in European countries and enriched with details and examples from documents based on seventeen country reports. The structure of those country reports was predefined, discussed, harmonized and completed by a group of scientists and professionals involved in COST action E-33, »Forest for recreation and tourism.« Evaluation methods related to forest goods and services were described from theoretical and practical viewpoints with emphasis on their applicability to a specific type of research. Results and Conclusion: Nonmarket values of forest goods and services can be estimated in a number of different ways. The methods can be divided into two basic categories: first, based on market prices, and second, based on non-market evaluation. Our focus is on the second strategy where the market prices are not known. Further division of this method goes in two broad categories according to the nature of the data generated for modelling and estimation: (a) »stated preference methods« where individuals’ preferences are not observed but rather stated, and (b) »revealed preference methods« where we can observe people acting in real-world settings where people live with the consequences of their choices.The most widely used method for valuing natural resources is the contingent valuation (CV) method. Choice experiments (CE) and hedonic pricing (HP) methods have been included in far fewer empirical studies, but the application of these methods has passed the demonstration stage. We also discuss the newly developed methods of benefit transfer and meta-analysis which use values, functions, and other descriptions from other studies to evaluate natural resources