Sensitivity of 21st century simulated ecosystem indicators to model parameters, prescribed climate drivers, RCP scenarios and forest management actions for two Finnish boreal forest sites

Forest ecosystems are already responding to changing environmental conditions that are driven by increased atmospheric CO2 concentrations. These developments affect how societies can utilise and benefit from the woodland areas in the future, be it for example climate change mitigation as carbon sinks, lumber for wood industry, or preserved for nature tourism and recreational activities. We assess the effect and the relative magnitude of different uncertainty sources in ecosystem model simulations from the year 1980 to 2100 for two Finnish boreal forest sites. The models used in this study are the land ecosystem model JSBACH and the forest growth model PREBAS. The considered uncertainty sources for both models are model parameters and four prescribed climates with two RCP (representative concentration pathway) scenarios. Usually, model parameter uncertainty is not included in these types of uncertainty studies. PREBAS simulations also include two forest management scenarios. We assess the effect of these sources of variation at four different points in time on several ecosystem indicators, e.g. gross primary production (GPP), ecosystem respiration, soil moisture, recurrence of drought, length of the vegetation active period (VAP), length of the snow melting period and the stand volume. The uncertainty induced by the climate models remains roughly the same throughout the simulations and is overtaken by the RCP scenario impact halfway through the experiment. The management actions are the most dominant uncertainty factors for Hyytiala and as important as RCP scenarios at the end of the simulations, but they contribute only half as much for Sodankyla. The parameter uncertainty is the least influential of the examined uncertainty sources, but it is also the most elusive to estimate due to non-linear and adverse effects on the simulated ecosystem indicators. Our analysis underlines the importance of carefully considering the implementation of forest use when simulating future ecosystem conditions, as human impact is evident and even increasing in boreal forested regions.Peer reviewe

Consistent estimates of gross primary production of Finnish forests : comparison of estimates of two process models

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Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

The influence of drought on plant functioning has received considerable attention in recent years, however our understanding of the response of carbon and water coupling to drought in terrestrial ecosystems still needs to be improved. A severe soil moisture drought occurred in southern Finland in the late summer of 2006. In this study, we investigated the response of water use efficiency to summer drought in a boreal Scots pine forest (Pinus sylvestris) on the daily time scale mainly using eddy covariance flux data from the Hyytiala (southern Finland) flux site. In addition, simulation results from the JSBACH land surface model were evaluated against the observed results. Based on observed data, the ecosystem level water use efficiency (EWUE; the ratio of gross primary production, GPP, to evapotranspiration, ET) showed a decrease during the severe soil moisture drought, while the inherent water use efficiency (IWUE; a quantity defined as EWUE multiplied with mean daytime vapour pressure deficit, VPD) increased and the underlying water use efficiency (uWUE, a metric based on IWUE and a simple stomatal model, is the ratio of GPP multiplied with a square root of VPD to ET) was unchanged during the drought. The decrease in EWUE was due to the stronger decline in GPP than in ET. The increase in IWUE was because of the decreased stomatal conductance under increased VPD. The unchanged uWUE indicates that the trade-off between carbon assimilation and transpiration of the boreal Scots pine forest was not disturbed by this drought event at the site. The JSBACH simulation showed declines of both GPP and ET under the severe soil moisture drought, but to a smaller extent compared to the observed GPP and ET. Simulated GPP and ET led to a smaller decrease in EWUE but a larger increase in IWUE because of the severe soil moisture drought in comparison to observations. As in the observations, the simulated uWUE showed no changes in the drought event. The model deficiencies exist mainly due to the lack of the limiting effect of increased VPD on stomatal conductance during the low soil moisture condition. Our study provides a deeper understanding of the coupling of carbon and water cycles in the boreal Scots pine forest ecosystem and suggests possible improvements to land surface models, which play an important role in the prediction of biosphere-atmosphere feedbacks in the climate system.Peer reviewe

Energiajärjestelmän ja kasvihuonekaasujen kehitykset : Hiilineutraali Suomi 2035 – ilmasto- ja energiapolitiikan toimet ja vaikutukset

Tutkimus on tehty Hiilineutraali Suomi 2035 -hankkeessa ja käsittelee hallitusohjelman, uuden ilmastolakiehdotuksen sekä Euroopan Unionin Suomelle esittämien energia- ja ilmastotavoitteiden kustannustehokasta ja johdonmukaista saavuttamista. Selvitys palvelee kansallisen ilmasto- ja energiastrategian ja keskipitkän aikavälin ilmastopolitiikan suunnitelman (KAISU) valmistelua. Analyysien pohjana ovat kaksi skenaariota, WEM ja WAM, joista WAM-skenaario sisältää hahmotellut uudet politiikkatoimet ja ohjauskeinot. Työssä on laadittu sektorikohtaiset analyysit kotimaan-liikenteelle, työkoneille, maataloudelle ja rakennusten energiakäytölle sekä integroiva koko energiajärjestelmän skenaariotarkastelu vuoteen 2050. Tulosten mukaan Suomi voi WAM-skenaarion mukaisin politiikkatoimin saavuttaa sekä ilmastolakiehdotuksen mukaiset tiukennetut kasvihuonekaasujen kokonaispäästöjen vähennystavoitteet että EU:n taakanjakosektorille esittämät uudet tavoitteet vuonna 2030, kunhan ilmastotietoisuus heijastuu riittävästi kuluttajien ja muiden toimijoiden valinnoissa sekä investoineissa. Integroidussa tarkastelussa kasvihuonekaasupäästöjen lisävähennystarve taakanjakosektorilla on 5,2–5,5 Mt CO2-ekv. vuosina 2030–2035. Lisävähennyksistä huomattavin osa kohdistuisi liikenteeseen (1,6–2,5 Mt) muun muassa voimakkaamman sähköistymisen, biokaasun käytön ja energiatehokkuuden paranemisen myötä. Hiilineutraali Suomi 2035 – Ilmasto- ja energiapolitiikan toimet ja vaikutukset (HIISI) -hankkeen raportit: Synteesiraportti – Johtopäätökset ja suositukset Maankäyttö- ja maataloussektorin skenaariot Ilmasto- ja energiapolitiikan toimien ympäristövaikutusten arviointi Kansantalouden skenaariot Metsiin kohdistuvien ilmastopoliittisten toimenpiteiden toteutettavuus ja puun tarjonta yksityisen metsänomistuksen näkökulmasta Energiajärjestelmän ja kasvihuonekaasujen kehitykset Tämä julkaisu on toteutettu osana valtioneuvoston selvitys- ja tutkimussuunnitelman toimeenpanoa (tietokayttoon.fi). Julkaisun sisällöstä vastaavat tiedon tuottajat, eikä tekstisisältö välttämättä edusta valtioneuvoston näkemystä

Modelling spatio-temporal soil moisture dynamics in mountain tundra

Abstract Soil moisture has a fundamental influence on the processes and functions of tundra ecosystems. Yet, the local dynamics of soil moisture are often ignored, due to the lack of fine resolution, spatially extensive data. In this study, we modelled soil moisture with two mechanistic models, SpaFHy (a catchment-scale hydrological model) and JSBACH (a global land surface model), and examined the results in comparison with extensive growing-season field measurements over a mountain tundra area in northwestern Finland. Our results show that soil moisture varies considerably in the study area and this variation creates a mosaic of moisture conditions, ranging from dry ridges (growing season average 12 VWC%, Volumetric Water Content) to water-logged mires (65 VWC%). The models, particularly SpaFHy, simulated temporal soil moisture dynamics reasonably well in parts of the landscape, but both underestimated the range of variation spatially and temporally. Soil properties and topography were important drivers of spatial variation in soil moisture dynamics. By testing the applicability of two mechanistic models to predict fine-scale spatial and temporal variability in soil moisture, this study paves the way towards understanding the functioning of tundra ecosystems under climate change. This article is protected by copyright. All rights reserved.Peer reviewe