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Inimmõjust põhjustatud metsade degradeerumise hindamine erinevates bioomides kasutades satelliitandmete ruumianalüüsi

Authors: Montibeller, Bruno;

Inimmõjust põhjustatud metsade degradeerumise hindamine erinevates bioomides kasutades satelliitandmete ruumianalüüsi

Abstract

Forests are strongly impacted by human activities. While the deforestation is very likely the most common examples of human impact on forested areas, the remaining standing forests are susceptible to other types of direct or indirect forest degradation by humans. The direct human-induced impacts can be exemplified by forest fragmentation or selective logging while the indirect human-induced impacts can be related to the changes in the ecosystem services (e.g., carbon and water cycling) induced by anthropogenic climate change. The aim of this thesis was to evaluate two processes related to forest degradation: (i) fragmentation of tropical forest cover in the Brazilian Amazon and (ii) changes in forest evapotranspiration over/across the Baltic countries and the carbon cycle in undisturbed forest areas across Europe. Satellite derived data and spatial analyses were used to assess the impacts of forest degradation in these three different case studies. The results of this thesis showed that although the anti-deforestation initiatives have played an important role in reducing deforestation in the Brazilian Amazon region, the forest fragmentation has increased mainly because of the decrease in the size of forest loss patches and the spatial shift into areas previously isolated areas. Hence, more forest areas are potentially being degraded because of the edge effects (e.g., tree mortality) caused by the fragmentation. For the Baltic region, the results indicated an intensification of the evapotranspiration rates over undisturbed forest areas. The intensification occurred mainly during spring and early autumn months because of the longer growing season induced by the increasing temperatures during these periods. Changes in the climate patterns were also the potential cause for changes in the carbon assimilation rates over the European forests. Approximately 25% of the undisturbed European forests showed reduced total carbon assimilation. That shows the vulnerability and incapacity of certain forest areas to act as carbon sink.

Metsaökosüsteemid võivad siduda kuni 12% inimtekkelisest süsihappegaasist ning tagastada atmosfääri kuni 40% kohalikest sademetest. Seetõttu on metsaökosüsteemidel oluline roll süsihappegaasi emissioonide vähendamisel ja veeringe reguleerimisel. Samal ajal väheneb metsade pindala ning metsad degradeeruvad läbi killustumise ning nende süsiniku- ja veeringe reguleerimise võime võib väheneda kliimamuutuste tõttu. Käesoleva doktoritöö eesmärgiks oli hinnata kahte metsade degradeerumisega seotud protsessi: (1) troopilise vihmametsa killustumist Brasiilia Amasoonias ja (2) muutuseid evapotranspiratsioonis ja süsinikuringes Baltikumi ja Eurooma muutumatuna püsinud metsamassiivides. Käesoleva doktoritöö tulemused näitasid, et kuigi Brasiilias on metsatustumise vastased poliitikad vähendanud metsade raadamist, siis samal ajal on suurenenud metsade killustumine, sest raiutakse väiksemate eraldiste kaupa ja liikudes endiselt varem raadamata aladele. Killustunud metsas on rohkem metsaserva, kust on süsinikukaod suuremad nii leostumise kui ka gaasilise emissioonina. Baltikumis leiti, et pikem taimekasvuperiood on suurendanud evapotranspiratsiooni kevadel ja sügisel, kuid samal ajal on suvel evapotranspiratsioon mõnedes piirkondades vähenenud. Kuigi evapotranspiratsiooni suurenemisel ei ole metsade ökosüsteemile otseselt negatiivset mõju, siis võib sellel olla ebasoovitav mõju regiooni veeringele, sest suurenenud evapotranspiratsioon suurendab tõenäosust, et suveperioodil on mullas vähem vett, mis omakorda suurendab põuaohtu. Lisaks selgus, et neljandikus Euroopa muutumatuna püsinud metsamassiivides on süsiniku sidumine vähenenud. Vähenenud süsiniku sidumisega metsamassiivid paiknesid üle kogu Euroopa ning hõlmasid erinevaid metsatüüpe. Kliimamuutuste mõjul võib metsade süsiniku sidumine väheneda veelgi rohkem, mis seab kahtluse alla varasemalt eeldatud metsade võimekuse leevendada kliimamuutuste mõjusid.

Väitekirja elektrooniline versioon ei sisalda publikatsioone

https://www.ester.ee/record=b5519495

Country
Estonia
Related Organizations
Keywords

forests, dissertations, kliimamuutused, human impact, spatial analysis, forest ecosystems, dissertatsioonid, metsatustamine, ETD, Brasiilia, veeringe, Euroopa, metsaökosüsteemid, climatic changes, Europe, väitekirjad, remote sensing, carbon cycle, ruumianalüüs, inimmõju, süsinikuringe, kaugseire, Brazil, metsad

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  • citations
    This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    0
    popularity
    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
    Average
    influence
    This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
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    impulse
    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
    Average
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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
0
Average
Average
Average
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