Browsing by Subject "kuivuus"

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  • Neefjes, Ivo; Laapas, Mikko; Liu, Yang; Médus, Erika; Miettunen, Elina; Ahonen, Lauri; Quéléver, Lauriane; Aalto, Juho; Bäck, Jaana; Kerminen, Veli-Matti; Lampilahti, Janne; Luomao, Krista; Mäki, Mari; Mammarella, Ivan; Petäjä, Tuukka; Räty, Meri; Sarnela, Nina; Ylivinkka, Ilona; Hakala, Simo; Kulmala, Markku; Nieminen, Tuomo; Lintunen, Anna (Finnish Environment Institute, 2022)
    Boreal environment research
    Boreal forests are an important source of trace gases and atmospheric aerosols, as well as a crucial carbon sink. As such, they form a strongly interconnected coupled system with the atmosphere. The SMEAR II station is located in a boreal Scots pine forest in Hyytiälä, Finland, and has over 25 years of continuous measurements of atmospheric and ecosystem variables. In this study, we analyse the seasonal variations of trace gases, atmospheric aerosols, greenhouse gases, and meteorological variables, measured at the SMEAR II sta-tion during the past two and a half decades. Several ecosystem and atmospheric variables show seasonal correlations with each other, which suggests seasonal interactions within the climate system that links together ecosystem processes, greenhouse gases, trace gases and atmospheric aerosols. For instance, increased global radiation in summer increases air temperature and consequently affects the plant phenology, which promotes the ecosystem carbon exchange and biogenic volatile organic compound (biogenic VOC) release. This further affects the ambient concentrations of highly oxygenated organic molecules (HOMs) as well as the formation and growth of atmospheric organic aerosols. Organic aerosols subsequently influence aerosol optical properties and, through increased scattering, have the potential to cool the climate. We also discuss the impacts of the warm and dry summers of 2010 and 2018 on the studied variables. For these years, we find a higher-than-average ecosystem primary production especially in June, leading to an increased VOC flux from the forest. The increased VOC flux in turn leads to higher HOM and secondary aerosol concentration in the atmosphere. The latter increases light scattering by atmospheric aero-sol particles and thus leads to climate cooling. The results obtained in this study improve our understanding of how boreal forests respond to climate change.
  • Ahopelto, Lauri; Veijalainen, Noora; Guillaume, Joseph H. A.; Keskinen, Marko; Marttunen, Mika; Varis, Olli (MDPI, 2019)
    Sustainability 2019, 11, 1548
    Severe droughts can affect water security even in countries with ample water resources. In addition, droughts are estimated to become more frequent in several regions due to changing climate. Drought affects many socio-economic sectors (e.g., agriculture, water supply, and industry), as it did in 2018 in Finland. Understanding the basin-wide picture is crucial in drought management planning. To identify vulnerable and water stressed areas in Finland, a water use-to-availability analysis was executed with a reference drought. Water stress was analyzed with the Water Depletion Index WDI. The analysis was executed using national water permits and databases. To represent a severe but realistic drought event, we modelled discharges and runoffs from the worst drought of the last century in Finland (1939–1942). The potential for performing similar analyses in data scarce contexts was also tested using estimates from global models as a screening tool. The results show that the South and Southwest of Finland would have problems with water availability during a severe drought. The most vulnerable areas would benefit from drought mitigation measures and management plans. These measures could be incorporated into the EU River Basin Management Plans.
  • Rolls, Robert J.; Chessman, Bruce C.; Heino, Jani; Wolfenden, Ben; Thurtell, Lisa A.; Cheshire, Katherine J. M.; Ryan, David; Butler, Gavin; Growns, Ivor; Curwen, Graeme (Springer Science and Business Media LLC, 2022)
    Landscape Ecology
    Context A core theme in ecohydrology is understanding how hydrology affects spatial variation in the composition of species assemblages (i.e., beta diversity). However, most empirical evidence is from research in upland rivers spanning small spatial extents. Relatively little is known of the consequences of hydrological variation for beta diversity across multiple spatial scales in lowland rivers. Objectives We sought to examine how spatial variation in hydrology and fish beta diversity within and among rivers changed over time in response to intensification and cessation of hydrological drought. Methods We used monitoring data of fish assemblages, coupled with hydrological and biophysical data, to test how spatial variation in hydrology and multiple components of fish beta diversity in lowland rivers of the Murray—Darling Basin (Australia) varied across spatial scales during contrasting hydrological phases. Results Spatial variation in hydrology among rivers declined with increasing duration of drought before increasing during a return to above-average flows. Spatial variation in hydrology within rivers did not show consistent changes between hydrological phases. Beta diversity among and within rivers showed variable, river-specific changes among hydrological phases for both incidence- and abundance-based components of assemblage composition. Conclusions Inconsistent hydrology—beta diversity patterns found here suggest that mechanisms and outcomes of drought and flooding impacts to beta diversity are context-dependent and not broadly generalisable. Our findings indicate that hydrological fluctuations occurring in the Murray—Darling Basin in the period analysed here did not cause significant or consistent homogenisation or differentiation of freshwater fish assemblages.
  • Freitas, Aline A.; Drumond, Anita; Carvalho, Vanessa S. B.; Reboita, Michelle S.; Silva, Benedito C.; Uvo, Cintia B. (MDPI AG, 2022)
    Atmosphere
    The São Francisco River Basin (SFRB) is one of the main watersheds in Brazil, standing out for generating energy and consumption, among other ecosystem services. Hence, it is important to identify hydrological drought events and the anomalous climate patterns associated with dry conditions. The Standard Precipitation Index (SPI) for 12 months was used to identify hydrological drought episodes over SFRB 1979 and 2020. For these episodes, the severity, duration, intensity, and peak were obtained, and SPI-1 was applied for the longest and most severe episode to identify months with wet and dry conditions within the rainy season (Nov–Mar). Anomalous atmospheric and oceanic patterns associated with this episode were also analyzed. The results revealed the longest and most severe hydrological drought episode over the basin occurred between 2012 and 2020. The episode over the Upper portion of the basin lasted 103 months. The results showed a deficit of monthly precipitation up to 250 mm in the southeast and northeast regions of the country during the anomalous dry months identified through SPI-1. The dry conditions observed during the rainy season of this episode were associated with an anomalous high-pressure system acting close to the coast of Southeast Brazil, hindering the formation of precipitating systems.
  • Truchy, Amélie; Sarremejane, Romain; Muotka, Timo; Mykrä, Heikki; Angeler, David G.; Lehosmaa, Kaisa; Huusko, Ari; Johnson, Richard K.; Sponseller, Ryan A.; McKie, Brendan G. (Wiley, 2020)
    Global Change Biology 26 6 (2020)
    Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post-drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (a) algal biomass accrual; (b) microbial respiration; and (c) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An 8-day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5 weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal dieback began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short-term droughts can have extended consequences for stream ecosystems in the world's vast boreal region, and especially on the ecosystem processes and services mediated by algal biofilms.
  • Vienonen, Sanna; Rintala, Jari; Orvomaa, Mirjam; Santala, Erkki; Maunula, Markku (Suomen ympäristökeskus, 2012)
    Suomen ympäristö 24/2012
    Tutkimuksen tavoitteena oli selvittää ilmastonmuutoksen vaikutuksia vesihuollossa sekä keinoja sopeutua muutoksiin. Tutkimus tehtiin pääosin kirjallisuusselvityksenä. Lisäksi kuultiin noin 50 vesihuollon asiantuntijaa. Kirjallisuuden perusteella tarkasteltiin myös eri ilmastoskenaarioissa ja -malleissa esitettyjä arvioita raaka-vesivarastojen määrässä ja laadussa tapahtuvista muutoksista. Ilmastonmuutoksen vaikutukset vesihuoltoon voivat olla joko haitallisia tai myönteisiä, suoria tai välillisiä, ja niiden arviointiin liittyy monia epävarmuustekijöitä. Suurimmat vaikutukset aiheutuvat äärevien sääilmiöiden kuten pitkien kuivuusjaksojen, rankkasateiden ja myrskyjen yleistymisestä. Myrskyjen seurauksena sähkökatkokset vesihuoltolaitoksilla lisääntyvät, mikä vaikeuttaa veden käsittelyä ja johtamista. Vesistöjen pinnannousun ja tulvien seurauksena pintavesiä voi kulkeutua pohjavesimuodostumiin ja vedenottamoille, ja jätevesipumppaamojen ylivuotoriski kasvaa. Pitkät kuivuusjaksot voivat aiheuttaa ongelmia lähinnä pienten raakavesilähteiden vedenlaadulle ja riittävyydelle. Ilmastonmuutoksella on vaikutuksensa myös maan-käyttöön, josta voi paikoin muodostua yhä merkittävämpi riski raakavesilähteille. Keskeisimpiä ilmastonmuutokseen sopeutumisen keinoja vesihuollossa ovat vedenottokaivojen sijoittaminenantoisuudeltaan otollisimpiin paikkoihin tulvariskialueiden ulkopuolelle, jäteveden pumppaamojen sijoittaminenpohjavesialueiden ja tulvariskialueiden ulkopuolelle, vedenkäsittelyvalmiuden parantaminen niin normaali- kuin erityistilanteissa, pienten pohjavesimuodostumien antoisuuden selvittäminen sekä vesihuoltolaitosten varavesi ja varavoimalähteiden turvaaminen. Lisäksi suunnitelmilla, vesihuoltolaitosten välisellä yhteistyöllä, maankäytön ohjauksella sekä tietojärjestelmien ja mallinnusten hyödyntämisellä voidaan tehostaa vesihuoltolaitosten sopeutumista ilmastonmuutokseen
  • Venäläinen, Ari; Lehtonen, Ilari; Mäkelä, Antti (Ilmatieteen laitos, 2016)
    Raportteja - Rapporter - Reports 2016:3
  • Rikala, Risto; Puttonen, Pasi (Suomen metsätieteellinen seura, 1988)
  • Grönlund, Leila (Helsingfors universitet, 2011)
    Muuttuva ilmasto, erityisesti kohoava lämpötila ja hiilidioksidipitoisuus, ei voi olla vaikuttamatta metsien kasvuun Suomessa. Metsätalouden sopeutumistoimilla voidaan pyrkiä lisääntyvän tuotospotentiaalin hyödyntämiseen ja metsätuhoriskien pienentämiseen. Sopeutumistoimien suunnittelemiseksi tarvitaan kuitenkin ensin tietoa siitä, miten ilmasto muuttuu ja mitä vaikutuksia ilmastonmuutoksella on. Työni oli osa vuonna 2005 käynnistettyä Ilmastonmuutoksen sopeutumistutkimusohjelmaa (ISTO). ISTO, ja näin myös oma tutkimukseni, tuottaa siis tietoa, jonka avulla voidaan mukauttaa metsänhoitoa vastaamaan muuttuvia ilmastooloja. Työssä tarkasteltiin maan vesipitoisuutta menneessä, nykyisessä ja muuttuvassa ilmastossa. Tavoitteena oli ennustaa, miten kuivuuden esiintyminen muuttuu Suomessa. Lisäksi menneiden kuivien vuosien kasvuvaikutuksia tutkittiin lustomittausten avulla. Vesitasemuutoksia lähdettiin tutkimaan mallilaskelmilla. Laskelmat perustuivat yksinkertaiseen open bucket – tyyppiseen vesimalliin. Mallissa maaperä ajatellaan tilana, johon sadanta ja lumen sulaminen tuovat vettä. Haihdunta ja valunta päinvastaisesti vähentävät sitä. Mallia sovellettiin Metlan yhdeksällä provenienssikoealueella, joihin lukeutui sekä kuusikoita että männiköitä eri kasvupaikoilta. Mallin yksinkertaisuuden takia koealueilta tarvittiin ainaostaan päivittäiset tiedot lämpötilasta, sadannasta, säteilystä ja VPD:stä. Lisäksi tuli selvittää kasvupaikkojen savi- ja hiekkapitoisuudet maaperäparametrien laskemiseksi. Vesimallilla tehtiin kahdet laskelmat. Ensimmäisissä laskettiin päivittäistä vesitasetta vuosina 1961-2008 mitattua sääaineistoa käyttäen. Toisissa laskelmissa käytettiin mitatusta säädatasta modifioitua sääennustetta. Lämpötilaa ja sadantaa oli kasvatettu vastaamaan vuosisadan lopulle tehtyä ennustetta. Näiden kahden laskelman tuloksia vertailtiin keskenään kuivuuspäivien lukumäärän osalta. Malliin oli siis ohjelmoitu kuivuuspäiväindeksi. Indeksin perusteella kuivuutta katsottiin olleen päivänä, jolloin kasveille käyttökelpoisen veden määrä laski alle 4 prosentin ja haihdunta leikkaantui 90 prosentilla normaalitasoon nähden. Kuivuuspäivät lisääntyivät kaikilla provenienssikoealueilla. Suurin muutos olisi tulosten perusteella odotettavissa etelärannikolla ja männyn kasvupaikoilla, jotka jo entuudestaan olivat alueista kuivimpia. Vähäisin muutos olisi taas odotettavissa kuusen kasvupaikoilla, etenkin jos sijainti ei ole aivan eteläisimmässä Suomessa. Kasvuvaikutuksia koskevien tulosten perusteella maan vesipitoisuus ei ole ollut merkittävä lustojen kasvua rajoittava tekijä provenienssikoealueilla menneinä vuosikymmeninä. Kuivuuspäivien määriin ei tule suhtautua absoluuttisina totuuksina, sillä ne ovat määritelmänsä mukaisesti vain suuntaa antavia. Niiden avulla voidaan tehdä ainoastaan päätelmiä metsiköiden ja vuosien välisistä suhteellisista eroista ja kehityssuunnista. Suoria johtopäätöksiä puuston kasvusta tai elinvoimaisuudesta ei pystytä tekemään. Eikä myöskään pystytä arvioimaan, reagoivatko mänty ja kuusi ennustettuihin muutoksiin eri tavoin. Voidaan kuitenkin päätellä, että keskimääräisten vuotuisten kuivuuspäivien lukumäärän kasvu johtaa brutto- ja nettoprimäärituotoksen vähenemiseen. Tätä kautta kuivuuden lisääntyminen alentaa myös kasvua verrattuna tilanteeseen, jossa kuivuuspäivien määrä pysyisi muuttumattomana.
  • Veijalainen, Noora; Ahopelto, Lauri; Marttunen, Mika; Jääskeläinen, Jaakko; Britschgi, Ritva; Orvomaa, Mirjam; Belinskij, Antti; Keskinen, Marko (MDPI, 2019)
    Sustainability
    Severe droughts cause substantial damage to different socio-economic sectors, and even Finland, which has abundant water resources, is not immune to their impacts. To assess the implications of a severe drought in Finland, we carried out a national scale drought impact analysis. Firstly, we simulated water levels and discharges during the severe drought of 1939–1942 (the reference drought) in present-day Finland with a hydrological model. Secondly, we estimated how climate change would alter droughts. Thirdly, we assessed the impact of drought on key water use sectors, with a focus on hydropower and water supply. The results indicate that the long-lasting reference drought caused the discharges to decrease at most by 80% compared to the average annual minimum discharges. The water levels generally fell to the lowest levels in the largest lakes in Central and South-Eastern Finland. Climate change scenarios project on average a small decrease in the lowest water levels during droughts. Severe drought would have a significant impact on water-related sectors, reducing water supply and hydropower production. In this way drought is a risk multiplier for the water–energy–food security nexus. We suggest that the resilience to droughts could be improved with region-specific drought management plans and by including droughts in existing regional preparedness exercises.
  • Sarremejane, Romain; Truchy, Amélie; McKie, Brendan G.; Mykrä, Heikki; Johnson, Richard K.; Huusko, Ari; Sponseller, Ryan A.; Muotka, Timo (John Wiley & Sons, 2021)
    Journal of Animal Ecology 90 (4), 886-898
    1. Community responses to and recovery from disturbances depend on local (e.g. presence of refuges) and regional (connectivity to recolonization sources) factors. Droughts are becoming more frequent in boreal regions, and are likely to constitute a severe disturbance for boreal stream communities where organisms largely lack adaptations to such hydrological extremes. 2. We conducted an experiment in 24 semi-natural stream flumes to assess the effects of local and regional factors on the responses of benthic invertebrate communities to a short-term drought. We manipulated flow (drought vs. constant-flow), spatial arrangement of leaf litter patches (aggregated vs. evenly distributed) and colonization from regional species pool (enhanced vs. ambient connectivity) to test the combined effects of disturbance, resource arrangement and connectivity on the structural and functional responses of benthic invertebrate communities. 3. We found that a drought as short as 1 week reduced invertebrate taxonomic richness and abundance, mainly through stochastic extinctions. Such changes in richness were not reflected in functional diversity. This suggests that communities were characterized by a high degree of functional redundancy, which allowed maintenance of functional diversity despite species losses. Feeding groups responded differently to drought, with organic matter decomposers responding more than scrapers and predators. 4. Three weeks were insufficient for complete invertebrate community recovery from drought. However, recovery was greater in channels subjected to enhanced connectivity, which increased taxonomic diversity and abundance of certain taxa. Spatial configuration of resources explained the least variation in our response variables, having a significant effect only on invertebrate abundance and evenness (both sampling occasions) and taxonomic richness (end of recovery period). 5. Even a short drought, if occurring late in the season, may not allow communities to recover before the onset of winter, thus having a potentially long-lasting effect on stream communities. For boreal headwaters, extreme dewatering poses a novel disturbance regime that may trigger substantial and potentially irreversible changes. An improved understanding of such changes is needed to underpin adaptive management strategies in these increasingly fragmented and disturbed ecosystems.
  • Smolander, Heikki; Lappi, Juha (Suomen metsätieteellinen seura, 1984)
  • Van Looy, Kris; Tonkin, Jonathan D.; Floury, Mathieu; Leigh, Catherine; Soininen, Janne; Larsen, Stefano; Heino, Jani; Poff, N. LeRoy; Delong, Michael; Jaehnig, Sonja C.; Datry, Thibault; Bonada, Nuria; Rosebery, Juliette; Jamoneau, Aurélien; Ormerod, Steve J.; Collier, Kevin J.; Wolter, Christian (2019)
    River Research and Applications 35 (2): 107-120
    Resilience in river ecosystems requires that organisms must persist in the face of highly dynamic hydrological and geomorphological variations. Disturbance events such as floods and droughts are postulated to shape life history traits that support resilience, but river management and conservation would benefit from greater understanding of the emergent effects in communities of river organisms. We unify current knowledge of taxonomic-, phylogenetic-, and trait-based aspects of river communities that might aid the identification and quantification of resilience mechanisms. Temporal variations in river productivity, physical connectivity, and environmental heterogeneity resulting from floods and droughts are highlighted as key characteristics that promote resilience in these dynamic ecosystems. Three community-wide mechanisms that underlie resilience are (a) partitioning (competition/facilitation) of dynamically varying resources, (b) dispersal, recolonization, and recruitment promoted by connectivity, and (c) functional redundancy in communities promoted by resource heterogeneity and refugia. Along with taxonomic and phylogenetic identity, biological traits related to feeding specialization, dispersal ability, and habitat specialization mediate organism responses to disturbance. Measures of these factors might also enable assessment of the relative contributions of different mechanisms to community resilience. Interactions between abiotic drivers and biotic aspects of resource use, dispersal, and persistence have clear implications for river conservation and management. To support these management needs, we propose a set of taxonomic, phylogenetic, and life-history trait metrics that might be used to measure resilience mechanisms. By identifying such indicators, our proposed framework can enable targeted management strategies to adapt river ecosystems to global change.