Ahto Kangur

Natural stand structures, disturbance regimes and successional dynamics in the Eurasian boreal forests: a review with special reference to Russian studies

Abstract• This review summarizes early stand-scale studies of pristine forest structures, disturbance regimes and successional patterns carried out in boreal Eurasia. We attempt to reveal, characterize and classify stand dynamic types that can be used as templates for nature-based forest management.• The studies reviewed demonstrate multiple successional pathways in stand development in all types of pristine forests. All-aged stands driven by small-scale disturbances are formed over successional development of several hundreds of years. This endogenous development can be interrupted by stand-replacing or partial disturbances leading to successions with even-aged or cohort-structured stands, respectively. In Western Europe, the most common disturbances are windthrows, surface fires and fluctuations in moisture regime; in Eastern Europe and Siberia, the most common disturbances are crown and surface fires and insect outbreaks. Type, return interval and severity of disturbances are strongly influenced by the site conditions and successional stage of a stand.• Based on characteristics of forest stands and disturbance regime, four main types of pristine boreal forest stand dynamics can be distinguished: (1) even-aged, compositional change dynamics, (2) even-aged, mono-dominant dynamics, (3) cohort dynamics and (4) fine-scale gap dynamics. These types can be mimicked in developing scenarios of ecological sustainable forest management in Eurasian boreal forests.Résumé• Cette revue bibliographique résume les résultats de nombreuses études anciennes sur la structure des peuplements forestiers, sur les régimes de perturbation et sur les dynamiques de succession en forêt boréale eurasienne. Une typologie des modes de succession est proposée pour servir de cadre à une gestion forestière proche de la nature.• Les études analysées montrent l’existence de multiples modes de succession et de développement des peuplements dans tous les types de forêts vierges analysées. Des peuplements mélangés comportant des arbres de tous âges se développent en réponse à des perturbations locales avec des dynamiques de plusieurs siècles. Ce développement endogène peut être interrompu par des renouvellements massifs ou des perturbations partielles qui conduisent à des successions basées sur des peuplements équiennes ou structurés en cohortes, respectivement. En Europe occidentale, les perturbations les plus fréquentes sont les chablis, les incendies de surface et des fluctuations des régimes hydriques ; en Europe oriental et en Sibérie, ce sont les incendies de surface et de canopée, et les attaques massives par des insectes.• En se basant sur les caractéristiques des peuplements et des types de perturbations, nous avons pu identifier quatre types principaux de dynamiques forestières : (1) une dynamique de changement de composition spécifique avec une structure équienne ; (2) une dynamique de domination par une espèce avec une structure équienne ; (3) une dynamique de cohortes ; et (4) une dynamique de trouées locales. Ces types de succession peuvent servir de base pour le développement de scénarios de gestion forestière durable de ces forêts boréales eurasiennes.

A conceptual model of forest stand development based on permanent sample-plot data in Estonia

Abstract Ecosystem management assumes that management practices based on natural disturbance patterns are likely to preserve both natural biodiversity and ecosystem functions. Ecosystem management thus combines traditional natural resource management and forestry practices together with classical notions of protection that are focused on sustaining a naturally evolving ecosystem. Increased knowledge and understanding of natural disturbance dynamics in boreal forest ecosystems allow for the creation of a template for sustainable forest management that is based on mimicking disturbances that are thought to contribute to the biodiversity of the ecosystem. The observed trends of natural development are discussed in this paper. Permanent sample-plot data are used to develop a conceptual model of stand succession following natural disturbance. The distinctive characteristics of disturbances that are relevant to forest management planning are identified and modelled.

SMEAR Estonia: Perspectives of a large-scale forest ecosystem – atmosphere research infrastructure

Abstract Establishment of the SMEAR Estonia at a hemiboreal mixed deciduous broad-leaved-evergreen needle-leaved forest at Järvselja, South-Eastern Estonia, has strongly enhanced the possibilities for national and international cooperation in the fields of forest ecosystem – atmosphere research and impacts of climatic changes on forest ecosystems, atmospheric trace gases, aerosols and air ions. The station provides a multitude of comprehensive continuously measured data covering key climatic and atmospheric characteristics (state and dynamics of solar radiation, trace gases, aerosols and air ions, meteorological parameters) and forest ecosystem traits (net primary productivity, individual tree growth, gas-exchange characteristics, soil variables). The station follows a multidisciplinary and multiscale approach covering processes in spatial dimensions ranging from nanometres to several hundred square kilometres, being thus able to significantly contribute to worldwide measurement networks and the SMEAR network. Here we present an overview of the station, its data produced and we envision future developments towards sustainable research and development of the large-scale scientific infrastructure SMEAR Estonia.

Monitoring and modeling of forest ecosystems: the Estonian Network of Forest Research Plots / Metsaökosüsteemide seire ja modelleerimine metsa kasvukäigu püsiproovitükkide võrgustiku abil

Abstract Forest research has long traditions in Estonia that can be traced back to the 19th century. Data from long-term forest experiments are available since 1921. The first studies mainly focused on silvicultural treatments and application of such data for understanding and modeling ecological processes was limited. The Department of Forest Management of the Estonian University of Life Sciences started to develop the Estonian Network of Forest Research Plots (ENFRP) in 1995. Since then, plots have been continuously re-measured with 5-year interval. Approximately 100-150 permanent sample plots were measured annually. In 2014, the long-term research network consisted of 729 permanent sample plots, of which 699 have been re-measured at least once, 667 plots - twice and 367 plots - three times. The total number of trees recorded in the network database amounts to 130,479. The plots are systematically distributed throughout the country. Detailed dendrometric measurements including tree spatial distribution are part of the survey protocol. Initially the network was set up to produce suitable data for development of individual tree growth models for Estonia. The significance of the network for the Estonian forest research is continuously increasing and nowadays ENFRP is recognized as an important national research infrastructure.

Why do we need a research and demonstration area of forest management planning at Järvselja

Abstract Changes in the society have created a need for a systematic approach in forestry combining forest management, timber harvest analysis, research and demonstration of new technologies. A research and demonstration area is an option for explaining and visualising frameworks of forest design, modelling and planning in the real nature. A research and demonstration area of forest management planning can be defined as a forested landscape that combines various forest uses and aims to ensure and explain forest management strategies as well as conservation of ecosystems and natural resources. A suitable area for creating the research and demonstration area of forest management planning is at Järvselja Training and Experimental Forest Centre in Estonia. It has naturally diverse forests and these include also habitats of several rare and endangered species and already comprise different sets of nature conservation areas. The centre has been used for forestry higher education and research for over 90 years and therefore all essential infrastructure has been developed including dormitories and lecture rooms for field training as well as different nature paths, old field experiments (e.g. initial spacing and thinning experiments) and new modern research facilities. Forest management plans and inventory data since 1922 still exist for the area. The area at Järvselja is expected to demonstrate present studies and research work in the most comprehensive way as well as the implications to forest management and the newest technologies in forest management and planning. Different systems and techniques of forest management can be studied and demonstrated to the wider public by establishing the research and demonstration area of forest management planning at Järvselja.

Dynamics of Carbon and Nitrogen Fluxes and Pools in Forest Ecosystem

Metabolism of trees, ground vegetation and microbes generate carbon and nitrogen fluxes in forest ecosystems. Carbon flows through the system, and nitrogen circulates between vegetation and soil. Trees synthesise sugars in photosynthesis and take nitrogen from soil. The biochemical regulation system allocates the annual amounts of synthesised sugars and nitrogen taken up to the growth of needles, wood and fine roots. The regularities in tree structure, generated by the action of the biochemical regulation system, determine the allocation to different tree components.

Online streaming public participation in forest management planning

Abstract A new paradigm in forest management using a streaming input of public participation needs effective online solutions. The process should be real-time, secure, effective and efficient. People are expected to share their data and thoughts on forest management with forest owners for improving forest management and planning. The participatory approach supports communication within society and can be designed as an interactive web-based solution. Many pre-requisites have already been met and society is ready for a successful start of an interactive participatory forest planning system in Estonia. People use digital identification for various purposes and the state already maintains an online public forest register. Motivating people to participate in the planning process is always challenging yet important for the successful implementation of the system. The system should allow simulating the development and management of forest stands following the participatory input and using ecosystem models and economic calculations. The outputs from the system include management alternatives, risk assessments and financial reports. The system requires a reliable financial compensation scheme to ensure overall long-term stability of the system and agreements between interested persons or groups and forest owners.

Tree height distribution dynamics in young naturally regenerated study plots

Abstract Growth assessment of young stands gives the possibility of assessing forest site potential, tree species-dependent competition and developing realistic predictions for the following periods. The study is conducted in naturally regenerated broadleaves dominated stands in 2005 at Järvselja Training and Experimental Forest Center. The current study material is collected from 9 study plots established in three forest stands (regeneration felling years respectively 1996, 2000 and 2002). The study plots were re-measured 4–6 times respectively between the years of 2006 and 2012. The Weibull distribution function fit for empirical height distributions in consecutive years was tested and the estimated Weibull parameters were analysed. Results indicate that empirical height distributions of young regenerated forests do not fit well to theoretical distributions, but in many cases, empirical and theoretical distribution are similar. The Weibull distribution shape parameter was related to the maximum height and range of the height, and the scale parameter was related to the mean, quadratic mean and median height.

Approaches for forest disturbance studies: natural variability and tree regeneration

Sustainable ecosystem management requires an understanding of complex generative ecosystem processes (Jogiste et al. 2007). These include natural disturbance regimes and the responses of the ecosystems to the affecting disturbances (Parmesan and Yohe 2003). An understanding of these ecosystem functions, which integrate physical and chemical processes with adaptations of individual organisms, requires multidisciplinary and interdisciplinary approaches (Jogiste et al. 2009). In this context the challenge is to bring together a wide range of experts on the subject matter to develop a shared and well based understanding of the ecosystem and affecting processes to encompass the objectives of improved forest resource utilization and planning. Forestry is an essential component of ecological, economical, and social structure. Traditional forest management is focused on a few commodities and the resulting forests lead to concerns about to the resilience and sustainability of the ecosystem. These concerns are particularly relevant in the context of changes in global climate and social and economic conditions. Society expects a broader range of forest values to be sustained. Studies on natural disturbances and disturbance regimes provide an opportunity to examine sound management plans for future forests. For this kind of research, specific study design or methodological setup becomes essential. In order to face the topic, an international workshop of the SNS (Nordic Forest Research Co-operation Committee) network ‘‘Natural Disturbance Dynamics Analysis for Forest Ecosystem Management’’, organized jointly by the SNS and Estonian University of Life Sciences, was held on 21–25 September 2009 at Vihterpalu, Estonia. The title of the workshop was ‘‘Approaches for forest disturbance studies’’ and it was the 8th international event of the network (Kangur et al. 2009). The research results presented in this workshop included eleven articles covering various types of forest condition from boreal Fennoscandia and Northern America, hemiboreal Baltic States to sub-tropical forest in Japan. Presented studies bring forward a variety of study approaches when addressing a broad range of topics related to natural and human-induced forest disturbances. In the beginning of the feature we list two review articles with regard to forest disturbances; Vodde et al. (2011) reviewed the studies of forest regeneration patterns in boreal and hemi-boreal forests depending on the wind-induced microsites, and Seedre et al. (2011) synthesized literature on carbon dynamics of boreal forests in North America after stand replacing wildfire and clear-cut logging. The first three A. Kangur (&) M. Metslaid Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia e-mail: ahto.kangur@emu.ee