Growth performance and management in mixed forest stands

In 2017, the global population stands at about 7.6 billion. Due to the medium variant of the population projections, developed by the UN, the world population will grow to nearly 10 billion by the middle of this century. As a consequence, the worldwide demand for wood will increase. Therefore, the forest sector has to develop concepts in order to cope with the increasing demand for wood, the altering environmental conditions and the challenge of climate change. Modified silvicultural treatment programs may contribute to solving these questions. Appropriate measures are the conversion of pure stands into mixed stands, the promotion of natural regeneration instead of artificial regeneration and the creation of structured forests consisting of indigenous or foreign tree species, which are better adapted to climate change and/or are growing faster. Mixed stands often exceed the volume as well as the biomass productivity of pure stands and increase the biodiversity of forest landscapes. Forest simulation models are a prerequisite for the management of mixed stands. They provide enhanced opportunities of planning for forest conversion and facilitate the decision support in forest practice. These model approaches support the development of goal oriented thinning programs and make it possible to test and optimize alternative silvicultural concepts without the establishment of experimental plots. The Bavarian State Forest Enterprise (Bayerische Staatsforsten) is managing 808731 ha of forest area in the southern part of Germany. Since 2005 this enterprise is converting pure, coniferous stands (> 200000 ha of forest area) into mixed, uneven-aged forests. A simulation program (single tree simulator) is used in order to achieve this goal

Būtinas naujas požiūris – mišrūs medynai, jų našumas bei ūkininkavimo juose principai

Vytauto Didžiojo universitetasŽemės ūkio akademij

Generic applicability of non-destructive biomass yield models for willow short rotation coppice: A case study for Germany and Lithuania

Rapid development and cultivation of willow Short Rotation Coppice (SRC), driven by international companies, demand reliable, easily applicable and cheap, non-destructive biomass yield estimation methods that are not yet available in Lithuania. During the last years, knowledge transfer between research institutions and industry across Europe has therefore been an important and fostered topic in this area. This study focuses on non-destructive biomass estimation methods, developed by German research institutions, and evaluates them under Lithuanian growth conditions. The common allometric power equation (APE), quadratic mean diameter (QMD), and yield appraisal (YA) approaches were tested for estimation bias, precision and accuracy. In total, data from 39 commercial willow SRC were used for the analyses. According to the results, mean annual oven dried biomass increment was higher in German willow SRC compared to Lithuanian willow SRC. However, there were no statistically significant differences between the scaling coefficients of plot specific allometric power equations. The developed country-specific common APE were characterize by very high coefficients of determination (R2 >0.96). Predictions of both common models were in line with predictions of plot-specific models and none of these models produced a higher bias or a significantly lower precision compared to plot-specific APE models. Compared with the other applied methods (QMD and YA), common APEs produced the most accurate estimations for Lithuanian and German willow SRC. Based on our findings we conclude that the transfer of non-destructive biomass estimation methods between Lithuania and Germany is scientifically sound and offers an important synergetic potential for local industriesMiškų ir ekologijos fakultetasVytauto Didžiojo universiteta

Biomass Models for Short Rotation Willow Plantations in Lithuania

Puslapiai nurodyti pagal pataisytą leidinįDespite of increasing areas of short rotation willow plantations in Lithuania, only very few studies have been done so far regarding the biomass production in these plantations. To fill this gap, the aim of this study was to develop biomass equations for fresh-weighted and for oven-dried willow biomass and to estimate the yield of short rotation plantations as expressed in fresh- weighted and oven-dried biomass. The data required by this study was gathered in the western part of Lithuania, in the Šilutė and Tauragė regions. For this purpose, sample plots were established in 21 short rotation willow plantations managed by “Klasmann-Deilmann Bioenergy“. All of them were first rotation plantations grown for 3 to 4 years. It was found that mean annual oven-dried biomass increment varied in these plantations from 0.2 to 7.6 tons per hectare per year. Additionally, the relations between stand level values were evaluated and a stand biomass yield model based on the mean stand height was developed. Relations on the plant level were analysed as well. As a result we developed biomass models based on the individual plant diameter for plant height as well as for fresh-weighted and for oven-dried biomassVytauto Didžiojo universitetasŽemės ūkio akademij

The new forest growth modelling approach in Lithuania: single tree level models

Single tree level models simulate mixed or pure stands of different age and structure, provide more flexible possibilities and alternatives in forest management. Therefore, these forest management tools could be very useful in solving present and future challenges in Lithuanian forestry sector: increasing proportions of mixed, uneven aged forests, diverse needs of wood industry, economic forest management efficiency. Yet, these models are not used in Lithuania. The aim of this study was to introduce single tree level modelling approach, to do critical qualitative assessment of single tree level models and their core elements id., competition, tree diameter, height increment and mortality modules. The main criteria for evaluation were set as follows: logic and biological realism of the model, data availability required for the model, evaluation of independent parameters used in the model, modelling simplicity, applicability to local conditions. The main conclusion was that single tree level models could be created and applied to Lithuanian forestryVytauto Didžiojo universitetasŽemės ūkio akademij

The impact of competition for growing space to diameter, basal area and height growth of trees

Competition between trees exists because of scarce resources required for trees growth. Growth dependent competitive situation of each tree in growth models is described by calculating distance dependent and distance independent competition indices. The first aim of the research was to compare distance dependent and distance independent competition indices and find the best ones with highest predictive capacity to simulate basal area and height growth of pine trees under Lithuanian conditions. The second aim was by using competition indices with highest predictive capacity, to describe the impact of growth dependent competition to tree diameter and height growth of pine trees. The research was based on data, collected from eighteen permanent sample plots. Plots were established by LRCAF Forest Institute, in various parts of Lithuania, with dominated pine forests of natural formation. The subject of research represents well normally and partially accelerated formation, Lithuanian pine forests, with age range from seven to ninety seven years that grow on mineral, low and average fertility, sitesVytauto Didžiojo universitetasŽemės ūkio akademij

The Impact of Competition for Growing Space on Diameter, Basal Area and Height Growth in Pine Trees

Competition between trees exists due to limited resources required for tree growth. The growth dependent competitive situation of each tree is described in growth models by calculating distance dependent and distance independent competition indices, CIs. The first aim of the research was to compare distance dependent and distance independent CIs and find the best variant with highest predictive capacity to simulate basal area and height growth of pine trees under Lithuanian conditions. The second aim was to describe the impact of competition on the tree diameter and height growth of pine trees by using those CIs that showed the highest predictive capacity. The research was based on data collected from eighteen permanent sample plots. The study evaluated 2 distance independent and 18 distance dependent CIs using partial correlation analysis.The results showed that the distance dependent CIs had a higher predictive capacity for basal area growth of pine trees. The CI proposed by Biging and Dobbertin (1992) combined with the selection method of an inverse search cone at height to crown base with opening angle of 80 degrees is recommended for developing basal area increment models used in single tree level growth simulators in Lithuania.While modelling tree height growth, distance dependent CIs did not show better results than the distance independent CIs. Hegyi's (1974) distance independent CI scored the highest partial correlation coefficients in predicting mean annual height increment. Generally, poor ability of competition indices to predict periodic mean annual height increment was observed under growth conditions prevalent in Lithuania.The results also showed that an increase in competition always had a negative impact on tree diameter growth, but a low level of competition increased tree height growth compared to no competition and additional competition had a negative impact to tree height growthLietuvos agrarinių ir miškų mokslų centro filialas Miškų institutasVytauto Didžiojo universitetasŽemės ūkio akademij

Species-specific and generic biomass equations for seedlings and saplings of European tree species

Biomass equations are a helpful tool to estimate the tree and stand biomass production and standing stock. Such estimations are of great interest for science but also of great importance for global reports on the carbon cycle and the global climate system. Even though there are various collections and generic meta-analyses available with biomass equations for mature trees, reports on biomass equations for juvenile trees (seedlings and saplings) are mainly missing. Against the background of an increasing amount of reforestation and afforestation projects and forests in young successional stages, such equations are required. In this study we have collected data from various studies on the aboveground woody biomass of 19 common tree species growing in Europe. The aim of this paper was to calculate species-specific biomass equations for the aboveground woody biomass of single trees in dependence of root-collar-diameter (RCD), height (H) and the combination of the two (RCD2 H). Next to calculating species-specific biomass equations for the species available in the dataset, we also calculated generic biomass equations for all broadleaved species and all conifer species. The biomass equations should be a contribution to the pool of published biomass equations, whereas the novelty is here that the equations were exclusively derived for young trees