Annual volume increment of the European forests—description and evaluation of the national methods used

International audienceAbstractKey messageIn order to obtain the necessary information for decision making etc., it is of increasing importance to be able to assess increment in a reliable way. Only repeated measurements on permanent sample plots in national forest inventories can provide accurate and comprehensive information on the various components of annual increment. Such inventory systems are increasingly employed in European countries. The felling/increment ratio, characterizing wood use sustainability, should be expressed as the ratio of felled living trees (excluding dead trees) and net increment.ContextReporting of gross and net annual increment is an element of international forest resource assessments and crucial for sustainable forest management. A number of approaches exist for the estimation of increment and its various sub-components. AimsThe main objectives of the study are to assess in detail what methods European countries have used and are planning to use in the future for international reporting of increment. Also, the usefulness of the various approaches for the assessment of increment is evaluated.MethodsA questionnaire asking about their assessment methods was distributed among the UNECE/FAO national correspondents of all European countries and members of the UNECE/FAO Team of Specialists on Monitoring Sustainable Forest Management. Databases of the Temperate and Boreal Forest Resource Assessment 2000 and of the State of Europe’s Forests 2011 were also used. Furthermore, the methodological background was described on the basis of relevant literature sources and some examples for country groups presented.ResultsCountries have indicated what methods they used for assessment of various increment components, and the percentage of countries, forest area, and growing stock corresponding to these replies has been calculated. With regard to gross annual increment, these metrics represent about one third for inventories based on permanent sample plots, but this percentage is on the increase.ConclusionThe concept of the “control method” for forest management was developed more than 100 years ago but only utilized at the local level. The same methodology is now widely used at the national and regional level due to the implementation of modern national forest inventories using permanent sample plots. Care should be taken to utilize the data correctly for international forest resource assessments, in order to, e.g., avoid double counting of dead trees

Comparison of methods used in European National Forest Inventories for the estimation of volume increment: towards harmonisation

International audienceAbstractKey messageThe increment estimation methods of European NFIs were explored by means of 12 essential NFI features. The results indicate various differences among NFIs within the commonly acknowledged methodological frame. The perspectives for harmonisation at the European level are promising.ContextThe estimation of increment is implemented differently in European National Forest Inventories (NFIs) due to different historical origins of NFIs and sampling designs and field assessments accommodated to country-specific conditions. The aspired harmonisation of increment estimation requires a comparison and an analysis of NFI methods.AimsThe objective was to investigate the differences in volume increment estimation methods used in European NFIs. The conducted work shall set a basis for harmonisation at the European level which is needed to improve information on forest resources for various strategic processes. MethodsA comprehensive enquiry was conducted during Cost Action FP1001 to explore the methods of increment estimation of 29 European NFIs. The enquiry built upon the preceding Cost Action E43 and was complemented by an analysis of literature to demonstrate the methodological backgrounds. ResultsThe comparison of methods revealed differences concerning the NFI features such as sampling grids, periodicity of assessments, permanent and temporary plots, use of remote sensing, sample tree selection, components of forest growth, forest area changes, sampling thresholds, field measurements, drain assessment, involved models and tree parts included in estimates. ConclusionIncrement estimation methods differ considerably among European NFIs. Their harmonisation introduces new issues into the harmonisation process. Recent accomplishments and the increased use of sample-based inventories in Europe make perspectives for harmonised reporting of increment estimation promising

Miško sklypo dydžio įtaka medynų našumui ir tvarumui

Sklypo dydžio įtaką medynų našumui ir tvarumui nustatėme, įvertinę įvairaus dydžio sklypų pasiskirstymo į zonas proporcijas bei pagrindinių medyno rodiklių reikšmes išskirtose ribinėje, paribio ir vidinėje sklypo zonose (Kuliešis, Kuliešis, 2006). Buvo tiriami Lietuvos pušynai, eglynai, beržynai ir juodalksnynai. Medyno našumą vertinome sukauptu medienos tūriu, o tvarumą – vidutiniu medžių nulaibėjimu, t.y. medžių skersmens ir aukščio santykiu. Darbe panaudojome nacionalinės miškų inventorizacijos metu išmatuotų įvairiose medyno dalyse pastovių apskaitos barelių ir jų sektorių duomenis bei valstybės miškų kadastro duomenis. Nustatėme sklypo dydžio įtakos medyno našumo pokyčiui tendenciją. Padidėjus sklypo plotui 1–9 ha intervale 1 ha, medienos tūrio kaupimas sklype sumažėja 0,2–1,3 m³/ha. Didžiausia sklypo dydžio įtaka medynų našumui nustatyta vyresnio amžiaus pušynuose, beržynuose ir juodalksnynuose, mažiausia – brandžiuose ir pribręstančiuose eglynuose, kas paaiškinama eglynų pažeidžiamumu bei įvairių trikdžių įtaka, išbalansuojant zoniškumo formavimąsi eglynuose. Ribinėje zonoje augančių miškų vidutinis nulaibėjimas patikimai, esant tikimybei 0,683, yra didesnis už vidinėje medyno zonoje augančių medžių minkštųjų lapuočių medynuose 10–15%, o spygliuočių medynuose – 9%. Mažėjant sklypo plotui didėja ribinės zonos dalis, o tuo pačiu ir medžių su didesniu nulaibėjimu, užtikrinančių medyno stabilumą ir tvarumą, dalis. Medyno zonos yra labai svarbus struktūrinis elementas, reikšmingai įtakojantis tiek medyno stabilumo, tvarumo, tiek ir jo našumo pokyčius, o sklypų smulkėjimas teigiamai veikia tiek medynų našumą, tiek ir jo tvarumąInfluence of forest compartment size on forest stand yield and sustainability was estimated differentiating compartment by zones – edge, preedge and interior (Kuliešis, Kuliešis, 2006) and determining various stand parameters in different compartment zones. Scotch pine, Norway spruce, Commont birch and Commont birch and Common alder stands of Lithuanian forest were investigated. Forest stand yield was estimated by accumulated growing stock volume, sustainability – by mean trees stem tapering, determined by ratio of diameters and heights of trees. Measurement data on permanent plots and their sectors of national forest inventory as well as data of forest cadastre were used. As result of this study the tendency of forest stand yield changes due to forest compartment area changes was determined. Growing stock volume decreases by 0.2–1.3 m³/ha due to forest compartment area increasing by 1 ha in the range 1–9 ha. This tendency mostly was determined in the Scotch pine, Common birch and Common alder stands of older age and at least – in premature and mature spruce stands. It is a reason of high damagability and least level of zonation of spruce stands especially in older age. Ratio of diameter and heights of trees, growing in the edge zone of compartment reliably, with probability 0.683, is higher to compare with trees, growing in the interior zone. The differences in the ratio of diameter and heights of trees, growing in different zones of compartment for the stands of broadleaves species contain 15%, for coniferous species – 9%. The share of compartment edge zone as well as share of trees with higher tapering of stem increases when compartment area decreases. The zones of the compartment are very important element, reliably influencing resistance, sustainability and yield of forest stand. Decreasing of compartments area positively influence forest stand yield, stand resistance and sustainabilityVytauto Didžiojo universitetasŽemės ūkio akademij

Edge Effect on Forest Stand Growth and Development

Edge, pre-edge and interior zones were distinguished in the forest compartments of Scotch pine, Norway spruce, Common birch and Common alder stands. The edge zone is located at 10-12 m, pre-edge at 12-27 m distance from the borderline. The most favourable growth conditions for trees at the stage of stand formation are in the pre-edge zone. In the beginning trees are characterized by a faster growth, however, later it approaches the growth of trees in the interior zone. In the edge zone, during stand formation plants suffer from additional competition for sunlight and nutrients on account of the adjacent stand, leading to the formation of sparsely stocked stands with lower and thicker trees. Growing more sparsely, trees later attain higher yield than trees growing in the interior part. The edge zone trees of lower diameter and height ratio form a buffer zone of the stand and increase its stability. The highest differences in the growing stock volume of stands growing in the edge zone and comprising 38-47 m3/ ha at maturity, as compared to the volume of stands growing in the interior part of compartments, were found in Scotch pine and Common alder stands, while the least - 8 m3/ha - in Norway spruce stands. Volumes of trees growing in the pre-edge zone, as compared to the volumes of stands growing in the interior part, remain higher up to maturity in Scotch pine by 3-4, Norway spruce by 1-2, Common birch by 9-10 and in Common alder stands by 1-3 %. Stand yield formation in the edge zone of a compartment is closer to the normal or slowed types, while in the interior and pre-edge parts - to the accelerated or normal typesVytauto Didžiojo universitetasŽemės ūkio akademij

Validation of Generalized Height-Diameter Model Based on Lithuanian NFI Data

The height estimation of every tree included in NFI sample plots is based on height-diameter ratio measurements of small amount of subsample trees. Height is measured for systematically selected every seventh tree on the sample plot (Kuliešis et al. 2003a, 2009b). On an average, height and diameter of 1–7 trees of prevailing and 1–3 trees of admixture tree species are measured per one plot. Heights of the remaining trees are estimated using generalized height-diameter model (Kuliešis 1993) based on measured diameters of all trees as well as height-diameter ratio of subsample trees. The goal of this study is to estimate the accuracy of tree height prediction using generalized height-diameter model based on measurement of height-diameter relation of small amount of subsample trees. This study makes use of the data of height-diameter ratio measurements on 1998–2010 NFI plots. This data derives from 47.5 thousand subsample trees of prevailing eight tree species as follows: pine, spruce, birch, aspen, black alder, grey alder, oak, and ash, and 24.6 thousand subsample trees of the same tree species as admixture in stands. Deviations of modeled heights from measured ones and their significance were estimated in respect of tree species, tree position – prevailing or admixture, mean diameter, and mean height. Spruce and oak stands have the most, and black alder and aspen stands have the least tree height variation per group with the range of mean diameter ± 2 cm and the range of mean height ± 1 m. Accuracy of mean tree height estimation per plot shifts from 3–5% in stands with mean diameter equal to 40 cm and more up to 5–15% in stands with mean diameter equal to 4–20 cm. Mean height deviations of predicted values from those obtained by measuring all tree populations on stand is negligible for all species, -0.6 cm per prevailing tree, -2.5 cm per admixture tree and -1.3 cm per any treeVytauto Didžiojo universitetasŽemės ūkio akademij

Objektyvaus sklypų skyrimo bandymas Dubravos miško medynų struktūros analizės pavyzdžiu

Santr. liet., angl., rusBibliogr.: p. 41Vytauto Didžiojo universitetasŽemės ūkio akademij

Tradicinė 50-oji medžioklė

Vytauto Didžiojo universitetasŽemės ūkio akademij

Looking for new solutions in delineating forest stands: segmentation of multi-source data

Up to date the main source of forest related information in Lithuania remains the standwise forest inventory. Delineation of stands all the time was based on the use of aerial photography. Changing economic conditions and new approaches in using satellite and GIS data requires looking for new solutions in conventional forest inventory techniques. This presentation would dea] with testing segmentation method for generating possibly homogeneous in terms of forestry variables units, corresponding to forest stands. The data sei of multi-source information, to be used for segmentation, consists of Spot and Landsai images, digital aerial photographs, old forest maps, boundaries of cutting areas, soil maps, digital elevation model, general GIS dala. A systematic network of field plots (Apr. 8 plots per ha) was developed for the test area. Minimization of within stand variance of main foresi parameters and correspondence with the expert-done stand discretization are used as the main criterions for assessment the segmentation results. The very first results indicate the possibility to achieve segmentation accuracy acceptable for forest inventory aimsVytauto Didžiojo universitetasŽemės ūkio akademij

Ūkininkavimas privačiuose miškuose

Vytauto Didžiojo universitetasŽemės ūkio akademij

Forest inventory system and its development corresponding to intensive forestry requirements

Praeito amžiaus septintojo-devintojo dešimtmečių darbų, skirtą atrankinei miškų inventorizacijai tobulinti, analizė parodė, jog dalis pasiūlymų, rekomendacijų, skirtų inventorizacijos efektyvumui padidinti, buvo parengta atsisakant principinių atrankos metodui nustatytų reikalavimų- tai apskaitos barelių, patenkančių ant sklypo ribos, vietos keitimas, kintamo dydžio, priklausomai nuo medžių skaičiaus, apskaitos barelių naudojimas, barelio centro susiejimas su medžio padėtimi, ribinių medžių padėties vizualinis įvertinimas, apskaitos medžių parinkimas matuotojų nuožiūra ir pan. Tokie ir kiti panašūs "patobulinimai" leido atpiginti darbus, tačiau negalėjo neatsiliepti inventorizacijos darbų kokybei. Medynų tūriai 2000-2009 metų sklypinėje miškų inventorizacijoje, taikant supaprastintą atrankinės inventorizacijos metodą, įvertinami su 10-15 % poslinkiais. Poslinkiai didėja didėjant medynų tūriams. Šie poslinkiai kartais yra didesni už poslinkius, gaunamus taikant akinės inventorizacijos metodą. Pagrindinė šių poslinkių priežastis yra atrankiniam metodui svarbių sąlygų nesilaikymas. Griežtas atrankos sąlygų laikymasis mažo objekto - sklypo lygmenyje reikalauja neadekvačiai padidinti inventorizacijos darbo sąnaudas. Todėl inventorizacijos praktikoje tikslingiausia yra derinti mažų objektų -sklypų akinę inventorizaciją, papildytą reikalingais matavimais ir objektų visumos atrankinę inventorizaciją. Pastovių, reguliariai permatuojamų, barelių sistema stambioje valdoje, kartu su palaipsniniu sklypų ribų bei medynų rodiklių tikslinimu vietoj periodiškai vykdomo atsitiktinio jų atnaujinimo, sudarytų naujas prielaidas nepertraukiamos miškotvarkos principams įgyvendinti bei informacijos (tiek grafinės, tiek aprašomosios) sklypo lygmenyje, perimamumui ir nuolatiniam tikslinimui užtikrintiThe analysis of research works performed in the last century seventies-nineties years and designated to develop a sampling forest inventory showed that some of the proposals and recommendations made to increase the efficiency of the inventory were prepared ignoring the principles of sampling method. It was: acceptance of relocation of sample plots falling on the site boundaries, the use of variable size sample plots depending on the number of trees, allocation of the plot centre relating it to the position of a tree, the visual judgment of location of boundary trees, selection of sample trees at the discretion of a surveyor and so on. These and other such "improvements" has made the inventory cheaper, but also impacted the quality of final results. Stands volumes during standwise forest inventory in the 2000-2009, using a simplified sampling inventory method, were estimated with a 10-15 % systematic error. The errors increase with the increase of stand volumes. These errors are sometimes larger than the errors obtained using the visual inventory method. The main reason of these biases is ignoring the basic requirements of sampling method. Astrict compliance with the sampling method requirements in a small object - on a forest site level, requires inadequate increase of inventory costs. Therefore, the most convenient and cost efficient forest inventory of small objects - is visual inventory of individual stands, supplemented by the necessary measurements, and objective sampling of entire objectsVytauto Didžiojo universitetasŽemės ūkio akademij