Sirvi Autor "Korjus, Henn (advisor)" järgi
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Kirje Analysis of tree competition and structural indices with a focus on modelling Silver birch (Betula pendula Roth) stands(Eesti Maaülikool, 2016) Maleki, Kobra; Korjus, Henn (advisor); Kiviste, Andres (advisor); von Gadow, Klaus (advisor); Petrauskas, Edmundas (opponent)The thesis is designed to establish and assess different approaches of competition measurement, incorporated with various competitor selection methods, focusing on silver birch in Estonia. The effect of competition and some other tree and stand variables on the growth and the mortality of trees are explored. Moreover, stands are characterized employing several structural indices calculated for sample plots of different shapes and sizes. The findings indicate that the measures including the trees spatial information, have superiority over the measures ignoring the trees locations within a forest stand, when studying the dynamics of stands and their effects on the structure and functioning of forest ecosystems. Also, plots with different shapes showed almost equal estimation accuracy, thus circular plots are preferred due to their smaller ratio of perimeter to surface. Besides, the optimum plot size depends on the stand structure, with an attempt to keep sample plots as small as possible to reduce the assessment efforts and costs.Kirje Assessment of private forest owners’ cooperation in Estonia(Eesti Maaülikool, 2015) Põllumäe, Priit; Korjus, Henn (advisor)The sustainable management of forest resources is important as it is linked to many goods and services that people need, e.g. timber, mushrooms, berries, and biodiversity. Therefore, it is important that these resources are managed in a sustainable way in order to satisfy the present and future needs. If land properties are small and forests belong to a large number of forest owners, sustainable forest management might be difficult to achieve. In Estonia, private forests are owned by approximately 97,000 owners, among whom 93,000 are private individuals. The size of an average private forest holding is about 10 hectares. With such ownership fragmentation, cooperation between forest owners could be a solution. In fact, such cooperation is highlighted and supported through various measures at state level. Despite this, there is still a lack of interest in cooperation as only about 6-8% of forest owners are members of special cooperation organisations (forest owners’ organisations). There are several reasons for this. Firstly, we need to consider the history of ownership as private forest ownership was only re-established some 25 years ago. The majority of owners are not aware of specific forestry issues and in some cases might not have linkages with the property. Secondly, the management objectives and values are very diverse and change in time. Since such cooperation between forest owners has mainly an economic function, it might often contradict the forest owners’ objectives. Policy formulation and implementation has not considered such diversity and therefore, the objectives of the policy might not be reached.Kirje Assessment of the structure and dynamics of Natura 2000 forest habitats in Estonia(Estonian University of Life Sciences, 2025) Paluots, Teele; Korjus, Henn (advisor); Franklin Jerry F. (advisor); Institute of Forestry and Engineering; Elferts, Didzis (opponent)ABSTRACT. Hemiboreal forests, including Natura 2000 forest habitats such as the Western taiga (N9010) and herb-rich spruce forests (N9050), play a crucial role in conserving biodiversity and supporting ecological processes. This doctoral thesis examines the structural complexity, biodiversity, and conservation effectiveness of these habitats using data from 308 permanent forest research plots in Estonia and the Lahemaa National Park inventory. Tree spatial patterns and interactions were analysed using structural indices, while historical and contemporary forest management impacts were assessed through archival materials, aerial photographs, and expert interviews. The results showed that protected areas had higher understory species diversity, particularly among bryophytes, indicating the presence of specific microhabitats. In N9010 forests, 63 species of conservation importance were identified, including bryophytes (12), vascular plants (7), lichens (17), fungi (11), and beetles (16). The average volume of deadwood ranged from 49.3 to 86.8 m³ ha⁻¹, exceeding values reported in earlier studies in Estonia and Finland. The distribution of deadwood revealed that it was more often found alongside living trees in natural forests, reflecting natural dynamics rather than being solely a result of large disturbances. Protected forest stands exhibited greater variation in tree diameters and a higher Structural Complexity Index (SCI), indicating more diverse stand structures. Unmanaged spruce forests were significantly more heterogeneous, showing greater species mingling and deadwood clustering. However, only 80% of the N9050 habitats met the Natura 2000 criteria, emphasizing the need for improved habitat mapping and restoration efforts. The study concludes that achieving a balance between conservation, sustainable management, and restoration requires integrated approaches. Structural indices are effective tools for assessing forest dynamics and supporting adaptive management. Improving deadwood evaluation systems, incorporating biodiversity into forest management plans, and restoring degraded habitats are essential strategies for the long-term conservation of hemiboreal forests.Kirje Monitoring and evaluation of forest ecosystem restoration(Eesti Maaülikool, 2014) Laarmann, Diana; Korjus, Henn (advisor); Stanturf, John A. (advisor); Abrudan, Ioan Vasile (opponent)Doktoritöö käsitleb metsaökosüsteemide taastamist Eestis, hõlmates nii kaevandamisega rikutud alade taasmetsastamist kui ka loodusmetsade struktuurikomponentide tekitamist madala loodusväärtusega aladele ning aladele, kus loodusliku taastumise protsess on aeglane. Intensiivne metsade majandamine on põhjustanud metsade struktuuri ja liigilise koosseisu lihtsustumist ning muutnud looduslike häiringute dünaamikat. Metsi oskuslikult majandades saab vähendada majandamisvõtete negatiivset mõju elurikkusele ja säilitada metsaökosüsteemide looduslikke funktsioone. Samuti tuleks eelkõige kaitsealustes metsades jälgida ja taastada metsade looduslikku funktsionaalsust. Ökoloogilise taastamise eesmärk on kiirendada muudetud, rikutud või hävitatud ökosüsteemides loodusliku taastumise protsesse. Doktoritöös käsitletakse ja analüüsitakse metsade taastamise erinevaid aspekte ja komponente ning otsesteks eesmärkideks on: a) uurida puistute looduslikkuse indikaatoreid ning hinnata puistute looduslikkust, b) määrata puistus üksikpuu suremist mõjutavad faktorid, c) analüüsida looduslikkuse taastamise võtete mõju puistu dünaamikale ja elurikkusele, d) analüüsida kaevandamisjärgsel taasmetsastamisel tekkinud ökosüsteemi. Püstitatud eesmärkide täitmiseks viidi läbi välitööd kokku 640 püsiproovitükil. Doktoritöös leiti, et surnud puidu kogus, surnud puude ruumiline paiknemine puistus, samuti suremise kiirus ja põhjused on tihedas seoses puistu looduslikkusega. Surnud puidu maht looduslikus seisundis ja majandatud metsas erinevad üksteisest oluliselt. Puude suremise hindamine võimaldab paremini aru saada metsaökosüsteemi struktuurist ja seal toimivatest protsessidest. Puu ellujäämine sõltub puu suhtelisest suurusest puistus ning puude suremise põhjused erinevat tüüpi puistutes on erinevad. Suremise põhjuste mitmekesisus on suurem looduslikus seisundis puistutes ning samuti on surnud puude paiknemine sellises puistus rohkem hajutatud. Töös väljatöötatud indeksid pakuvad võimalusi paremini hinnata puistu looduslikkust ja seejuures eristada puistus toimunud hiljutisi häiringuid. Looduslikkuse taastamise võtted olid läbi viidud ühetaolistes keskealistes okaspuupuistutes, kus peale taastamisvõtete tegemist puistustruktuur mitmekesistus, näiteks surnud puidu maht suurenes lagupuidu tekitamise võtte korral kuni 67 m3 ha-1. Loodusliku uuenduse arvukus oli kõrgeim pindalalt suuremas häilus ning ülepõletatud häilu korral. Taastamisvõtted avaldasid erinevatele liigirühmadele erinevat mõju: rohttaimede mitmekesisus suurenes enim ülepõletatud häilu korral, sammalde mitmekesisus lagupuidu tekitamise korral, samblike mitmekesisus suurenes enim häilu tekitamisel, ülepõletatud häilu korral mitmekesisus aga vähenes. Kontrollaladest eristus kõige rohkem rohttaimede, sammalde ja samblike puhul häilu ülepõletamise võte. Mardikaliste suurenenud arvukus ja liigiline mitmekesisus on puistu valgustingimuste muutuse ning elupaikade lisandumise otsene tulemus. Võrreldes ühe taastamisvõtte rakendamisega suurendab erinevate taastamisvõtete üheaegne kasutamine puistu heterogeensust ja tänu sellele suureneb ka elurikkus. Kaevandamisjärgse taasmetsastamise eesmärk on taastada ökosüsteemide kaevandamiseelne olukord. Üldjuhul on võimatu taastada minevikus olnud seisundit, sest kaevandamisega on kasvupinnast täielikult muudetud ning tihtipeale areneb seal välja hoopis uudne ökosüsteem. Taastamisedukuse hindamine põhineb mullanäitajate dünaamika, liigilise mitmekesisuse, taimkatte struktuuri ja ökoloogiliste protsesside uurimisel. Endise kaevandamisala mullad erinesid tüüpilistest metsamuldadest ja seetõttu on seal taimestiku arenguks tekkinud teistsugused tingimused. Samuti erinesid sealsed taimekooslused tüüpilistest metsas esinevatest kooslustest. Puistu takseernäitajad olid sarnaseimad sinilille kasvukohatüübi puistute takseernäitajatega. Ala looduslikule arengule jätmine võib taastamisel olla oluline alternatiiv metsaistutamisele, eriti juhul, kui rikutud ala on väike ja ümbritsetud loodusliku taimkattega ning kui alale pole määratud soovitavat eesmärki ning taastumise tähtaega.Kirje Quantitative assessment of stand structural traits and health condition in hemiboreal forest ecosystems(Estonian University of Life Sciences, 2022) Põldveer, Eneli; Korjus, Henn (advisor); Laarmann, Diana (advisor); Institute of Forestry and Engineering; Marozas, Vitas (opponent)In recent years, the focus of Estonian forestry has been on the better integration of economical, ecological and social functions, and consideration of ecosystem services. Although forest conservation is an important step for maintaining biodiversity, it may insufficiently provide expected ecological value. Efforts should promote stand structural diversity also in commercial forests, as the variety of stand structural elements that form structural patterns will promote resources for different species and ecosystem services. Loss of structural diversity negatively affects forest resistance to different abiotic and biotic factors. The current thesis synthesizes several methods that could be used in forest management and planning to focus on ecosystem values. The main aims of the thesis are to quantify the structural heterogeneity and spatial patterns of stands with different management history, to quantify the proportion of visually healthy trees with internal decay indicating decreased vitality in intensively managed conifer forest stands and to distinguish the spatial location of trees with internal decay. The thesis is based on the data collected from the Estonian Network of Forest Research Plots and different structural indices were used to reach the set aims. The results showed that the variety of structural elements and patterns (multiple tree species and sizes, such as large old trees or regrowth, deadwood abundance, different spatial distribution of dead and alive trees) in forest stands with different management history showed significant differences but depended on the main tree species. Heterogeneous stand structures were generally significantly more abundant in unmanaged (natural, recovering or conservation) forests compared to other forest types. For example, unmanaged Norway spruce stands were significantly more heterogeneous in mingling of species and differences in tree dimensions when compared to managed stands, and the positioning of trees was more irregular. Living trees were significantly more often surrounded with dead trees in Scots pine stands belonging to natural forests than in recovering or managed forests, and dead trees more frequently clumped in natural forests. Despite the lack of visual symptoms of internal damage, conifers in intensively managed stands had well-developed decay at the root collar, especially in Norway spruce stands. Additionally, visually healthy trees with internal decay were relatively often clumped, especially in Norway spruce stands. Structural indices are effective tools that provide quantitative information about spatial forest structure, e.g., how trees of different species, dimensions or vitality status are mixed in space and how heterogeneous the structure of a forest stand is. The importance of such indices will increase in forest management as high-resolution remote sensing data providing tree-level information will be used on a large scale.Kirje The role of forest certification in climate change mitigation: a comparative study of FSC and PEFC certified forests(Eesti Maaülikool, 2025) Allala, Benedicta; Korjus, Henn (advisor); Chair of Land Management and Wood Processing TechnologiesThis thesis explores the impact of forest certification on carbon sequestration in Estonia, Latvia, and Lithuania. It compares two major certification schemes, the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC), assessing their effectiveness in promoting sustainable forest management and climate change mitigation. Analysis of forest inventory data, emission statistics, and stakeholder surveys, the study finds that FSC-certified forests generally sequester more carbon than PEFC-certified or non-certified forests. Latvia and Lithuania have stronger forest sink capacities compared to Estonia, although it has the highest FSC-certified forest area. However, survey responses reveal divided opinions on whether certification contributes to sustainability, highlighting the need for improved public awareness and transparency. The research concludes that while certification supports carbon sequestration, its success depends on forest policy implementation and local ecological conditions. The study recommends aligning certification practices more closely with national climate goals and enhancing carbon monitoring efforts across the region.