The effects of elevated humidity, extreme weather conditions and clear-cut on greenhouse gas emissions in fast growing deciduous forests
Date
2016-03-11
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Abstract
Põhja-Euroopas võib tulevikus suureneda õhuniiskus ning sageneda kuumalained ja suvine põud. Seetõttu on oluline teada: (i) kuidas metsad, mis on kõige levinumad ökosüsteemid Põhja-Euroopas, muutuvates tingimustes käituvad ja (ii) mis mõju on ökosüsteemide kohanemisel kasvuhoonegaaside voogudele. Kiirekasvuliste lehtmetsade aktiivne (lühikese raieringiga) majandamine võimaldab vähendada fossiilsete kütuste kasutamist ja leevendada edasisi kliimamuutuseid, kuid sellega kaasnev lageraie ja lageraiele järgnev metsauuendus on tugevad häiringud metsamullale, mis koos peapuuliigiga võivad muuta mulla kasvuhoonegaasi voogusid. Seni pole kliimamuutuste ja metsamajandamise mõju kasvuhoonegaaside voogudele mullast atmosfääri piisavalt analüüsitud. Töö peamiseks eesmärgiks oli analüüsida kliimamuutuste (suurenenud õhuniiskuse, kuumalainete ja põua) ning metsamajandamise (lageraie, metsauuendusviisi ja puuliigi) mõju kasvuhoonegaaside süsihappegaasi (CO2), metaani (CH4) ja naerugaasi (N2O) voogudele kiirekasvulistes lehtmetsades. Suurenenud õhuniiskus, lageraie ja puuliigid mõjutasid kõiki kasvuhoonegaaside voogusid, samuti olid ekstreemsed ilmastikutingimused ja metsauuendus olulised tegurid CO2 ja CH4 voogude bilansi kujunemisel. Suurenenud õhuniiskus võis nii suurendada kui ka vähendada CO2 emissiooni ning toime sõltus teistest abiootilistest ja biootilistest teguritest. Seejuures võis kaasikute ja haavikute CH4 sidumine mulda ning haavikute N2O emissioon mullast olla pärsitud suurenenud õhuniiskuse tingimustes. Lageraie hall-lepikus vähendas N2O kadusid, kuid suurendas süsiniku gaasilist emissiooni. See töö annab esialgse ülevaate tuleviku kliima ja metsamajandamise mõjudest kiirekasvuliste lehtmetsade kasvuhoonegaasi voogudele.
Elevated humidity, heat waves and summer drought are some possible scenarios for future climate in northern Europe. Therefore it is important to know how forest – the main ecosystem type in northern Europe, will react and adapt to changes, and whether there is a positive feedback on soil-atmosphere greenhouse gas fluxes. Short rotation forestry in fast-growing deciduous stands is one possible solution to reduce the use of fossil fuels and to mitigate further climate change. On the other hand, clear-cutting and the following stand establishment are considerable disturbances for the forest soil, hence these disturbances, as well as the selected tree species, may have an effect on greenhouse gas fluxes. However, the effects of climate change, such as increased humidity, heat waves, and drought, on fast-growing deciduous forest ecosystems and the soil-atmosphere greenhouse gas fluxes of ecosystems, and the effects of forest management, such as tree species, stand establishment, and clear-cut on greenhouse gases are not sufficiently well studied. This thesis was a pilot study of several climate and management factors affecting greenhouse gas fluxes. The main aim of the thesis was to analyze the effect of climate change (elevated air humidity, extreme climate events) and forest management (clear-cut, stand establishment, tree species) on soil greenhouse gas (CO2, CH4, and N2O) emissions in fast-growing deciduous stands. Elevated humidity, clear-cut and tree species affected all the measured greenhouse gas fluxes. Extreme weather conditions and stand establishment influenced CO2 emissions and CH4 uptake. Elevated humidity had various effects on CO2 emissions, depending on abiotic and biotic factors. At the same time, CH4 uptake from both tree stands and N2O emissions in hybrid aspen stands were often decreased by humidity treatment. Clear-cut of grey alder forest decreased N2O loss but enhanced gaseous C losses. The results of this thesis provide a useful insight into future deciduous forest greenhouse gas dynamics.
Elevated humidity, heat waves and summer drought are some possible scenarios for future climate in northern Europe. Therefore it is important to know how forest – the main ecosystem type in northern Europe, will react and adapt to changes, and whether there is a positive feedback on soil-atmosphere greenhouse gas fluxes. Short rotation forestry in fast-growing deciduous stands is one possible solution to reduce the use of fossil fuels and to mitigate further climate change. On the other hand, clear-cutting and the following stand establishment are considerable disturbances for the forest soil, hence these disturbances, as well as the selected tree species, may have an effect on greenhouse gas fluxes. However, the effects of climate change, such as increased humidity, heat waves, and drought, on fast-growing deciduous forest ecosystems and the soil-atmosphere greenhouse gas fluxes of ecosystems, and the effects of forest management, such as tree species, stand establishment, and clear-cut on greenhouse gases are not sufficiently well studied. This thesis was a pilot study of several climate and management factors affecting greenhouse gas fluxes. The main aim of the thesis was to analyze the effect of climate change (elevated air humidity, extreme climate events) and forest management (clear-cut, stand establishment, tree species) on soil greenhouse gas (CO2, CH4, and N2O) emissions in fast-growing deciduous stands. Elevated humidity, clear-cut and tree species affected all the measured greenhouse gas fluxes. Extreme weather conditions and stand establishment influenced CO2 emissions and CH4 uptake. Elevated humidity had various effects on CO2 emissions, depending on abiotic and biotic factors. At the same time, CH4 uptake from both tree stands and N2O emissions in hybrid aspen stands were often decreased by humidity treatment. Clear-cut of grey alder forest decreased N2O loss but enhanced gaseous C losses. The results of this thesis provide a useful insight into future deciduous forest greenhouse gas dynamics.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
õhuniiskus, ilmastik, lageraie, mõjud, kasvuhoonegaasid, lehtmetsad, air humidity, weather, clear cutting, impacts, greenhouse gases, deciduous forests