Increases in organic carbon and nitrogen concentrations in boreal forested catchments — Changes driven by climate and deposition

Highlights • Brownification is an increasing threat to aquatic ecosystems. • Reasons behind changes in C and N concentrations in forested streams were studied. • TOC and TON concentrations increased significantly in 7–10 of 12 forested catchments in 30 yrs. • Air temperature and sulphate concentrations explained 83% of the TOC variation. • TON trends were connected to TOC and linked to climatic factors and drainage-%.Brownification, caused by increasing dissolved organic carbon (DOC) concentrations is a threat to aquatic ecosystems over large areas in Europe. The increasing concentrations of DOC in northern boreal streams and lakes have attracted considerable attention with proposed important drivers such as climate, deposition and land-use, and complex interactions between them. Changes in total organic N (TON) concentrations have received less attention, even though carbon and nitrogen losses are highly related to each other. We used long-term (1990–2019) monitoring records of 12 small data-rich headwater forested catchments in a large gradient of climate and deposition. We found that total organic carbon (TOC) concentrations were significantly increasing in almost all study catchments. The mean air temperature and change in sulphate concentrations had a strong, significant correlation to TOC change-%. Both explained, alone, more than 65% of the change in TOC concentrations, and, together, up to 83% of the variation. Sulphur deposition has already decreased to low levels, our results indicate that its importance as a driver of TOC leaching has decreased but is still clearly detected, while the impact of climate warming as a driver of TOC leaching will be even more pronounced in the future. A positive correlation was found between drainage-% and increases in TON, suggesting also importance of land management. TON trends were tightly connected to changes in TOC, but not directly linked to decreasing S deposition

Post-drainage stand growth and peat mineralization impair water quality from forested peatlands

Many recent studies have indicated upward trends in carbon and nutrient concentrations from drained peatland forests over time since their initial drainage, but the mechanisms behind these trends are still poorly understood. We gathered data on nitrogen and phosphorus concentrations discharged from 37 drained boreal peatland forests where we also had data on peat and tree stand characteristics. We found that tree stand volume and peat bulk density were positively correlated with the nitrogen and phosphorus concentrations discharged from particularly the deep-peated sites. We interpret these results to indicate that a plausible reason for the reported upward trends in nutrient concentrations is the maturing and growing of the tree stands over time since initial drainage and the consequent increasing evapotranspiration capacity, which results in lowered soil water levels and enhanced aerobic peat mineralization. We discuss how our results should be considered in the management of drained peatland forests

Long-term nitrogen and phosphorus dynamics in waters discharging from forestry-drained and undrained boreal peatlands

Contradictory results for the long-term evolution of nitrogen and phosphorus concentrations in waters discharging from drained peatland forests need reconciliation. We gathered long-term (10–29 years) water quality data from 29 forested catchments, 18 forestry-drained and 11 undrained peatlands. Trend analysis of the nitrogen and phosphorus concentration data indicated variable trends from clearly decreasing to considerably increasing temporal trends. While the variations in phosphorus concentration trends over time did not correlate with any of our explanatory factors, trends in nitrogen concentrations correlated positively with tree stand volume in the catchments and temperature sum. A positive correlation of increasing nitrogen concentrations with temperature sum raises concerns of the future evolution of nitrogen dynamics under a warming climate. Furthermore, the correlation with tree stand volume is troublesome due to the generally accepted policy to tackle the climate crisis by enhancing tree growth. However, future research is still needed to assess which are the actual processes related to stand volume and temperature sum that contribute to increasing TN concentrations

Long-term nitrogen and phosphorus dynamics in waters discharging from forestry-drained and undrained boreal peatlands

Contradictory results for the long-term evolution of nitrogen and phosphorus concentrations in waters discharging from drained peatland forests need reconciliation. We gathered long-term (10–29 years) water quality data from 29 forested catchments, 18 forestry-drained and 11 undrained peatlands. Trend analysis of the nitrogen and phosphorus concentration data indicated variable trends from clearly decreasing to considerably increasing temporal trends. While the variations in phosphorus concentration trends over time did not correlate with any of our explanatory factors, trends in nitrogen concentrations correlated positively with tree stand volume in the catchments and temperature sum. A positive correlation of increasing nitrogen concentrations with temperature sum raises concerns of the future evolution of nitrogen dynamics under a warming climate. Furthermore, the correlation with tree stand volume is troublesome due to the generally accepted policy to tackle the climate crisis by enhancing tree growth. However, future research is still needed to assess which are the actual processes related to stand volume and temperature sum that contribute to increasing TN concentrations

Metsäojitettujen soiden typpi- ja fosforikuormitus Suomessa

Viime vuosina julkaistujen tutkimusten mukaan metsäojitettujen soiden vesistökuormituksen epäillään olevan moninkertaisesti aiemmin arvioitua suurempaa. Syynä tähän on se, että kuormitusta syntyy aiemmista käsityksistä poiketen silloinkin, kun ojitusalueilla ei ole vuosikausiin tehty mitään toimenpiteitä. Tässä työssä arvioitiin metsäojitusalueilta syntyvä vesistökuormitus ottamalla huomioon sekä tämä nykyisistä metsätaloustoimenpiteistä riippumaton ”ojituslisä” että kunnostusojituksen, lannoituksen ja hakkuiden aiheuttama kuormitus. Tehdyn arvion mukaan metsätaloudesta ojitetuilla soilla syntyy Suomessa vuosittain typpikuormitusta noin 8 500 Mg ja fosforikuormitusta 590 Mg. Kun ojituslisä otetaan huomioon, typpikuormitus on noin 18-kertainen ja fosforikuormitus 6–7-kertainen aiempiin vain eri toimenpiteiden kuormitukset huomioon ottaviin arvioihin verrattuna. Vesiensuojelun kannalta oleellista olisi selvittää, mitkä tekijät ojitusalueilla aiheuttavat ojituslisän muodossa tapahtuvaa pysyvää kuormitusta ja mitä tämän kuormituksen torjumiseksi on tehtävissä.Peer reviewe

Metsistä ja soilta tuleva vesistökuormitus 2020

Metsätalouden osuus metsistä ja soilta tulevasta typen kokonaiskuormituksesta on uuden arvion mukaan 16 % (7 300 tonnia/v), fosforikuormituksesta 25 % (440 tonnia/v) ja orgaanisen hiilen kuormituksesta 78 000 tonnia/v. Uusissa typpi- ja fosforikuormitusarvioissa näkyy selvästi metsäojitusten vaikutus. Metsätalouden osuus kaikesta ihmistoiminnan aiheuttamasta typpikuormituksesta nousee 6 %:sta 12 %:iin ja fosforikuormituksesta vastaavasti 8 %:sta 14 %:iin. Vuosittaiseksi metsistä ja soilta tulevaksi typen kokonaiskuormitukseksi arvioidaan 44 600 tonnia, fosforin kokonaiskuormitukseksi 1 760 tonnia ja orgaanisen hiilen kokonaiskuormitukseksi 1,8 miljoonaa tonnia. Luonnonhuuhtouma on suurinta Etelä-Suomessa. Metsätalouden aiheuttama ravinnekuormitus on puolestaan suurinta Pohjanmaalla ja Kainuussa, missä on paljon ojitettuja soita. Aiemmin metsäojituksen on oletettu aiheuttavan ravinnekuormitusta 10 vuoden ajan. Uusien tulosten mukaan kuormitus jatkuu pidempään. Hankkeen tulosten mukaan metsistä tuleva fosforikuormitus on vähentynyt viime vuosiin asti. Valumaveden typen- ja orgaanisen hiilen pitoisuuksissa havaittiin nousevia trendejä vuosina 1978–2018. Samanaikaisesti ilman lämpötilassa, hydrologiassa ja happamassa laskeuma on tapahtunut muutoksia, jotka voivat selittää kuormitusta. Tutkijoiden mukaan typen ja orgaanisen hiilen kuormituksen hallintaan tulisi kehittää uusia menetelmiä erityisesti turvemaille. MetsäVesi-hankkeen tulokset tulisi sisällyttää vesienhoidossa käytettävään VEMALA-mallijärjestelmään, ja ne tulisi jatkossa huomioida myös virallisissa raportoinneissa. MetsäVesi-hanke toteutettiin vuoden 2019 aikana yhteistyössä Luonnonvarakeskuksen (Luke), Suomen ympäristökeskuksen (SYKE), Tapio Oy:n ja Oulun yliopiston tutkijoiden kanssa. Työssä hyödynnettiin laajoja valtakunnallisia veden laadun ja virtaaman seuranta-aineistoja

The annual excursion of the Nordic Bryological Society (NBS) and the Finnish Bryophyte Expert Group to Finnish Lapland in 2019

The Nordic Bryological Society held its Annual meeting and excursion from 5 to 9 August 2019 in Sodankylä, Kittilä and Kolari in northern Finland. The excursion was attended by twenty-one participants. Special emphasis was given to boreal aapa mires and their Sphagnum species. A multitude of Sphagnum species typical to the area was encountered. Also, Red Listed species of meso- and eutrophic flark fens were discovered, e.g. Hamatocaulis vernicosus, H. lapponicus, Meesia longiseta, Schistochilopsis grandiretis and Moerckia flotoviana. Sphagnum annulatum, S. flexuosum, S. divinum, Heterogemma laxa and Scapania umbrosa were collected for the first time from Kittilän Lappi biogeographical province. Sphagnum annulatum, S. divinum, Campylium laxifolium, Pohlia sphagnicola, Gymnocolea borealis and Heterogemma laxa were collected for the first time from Sompion Lappi biogeographical province. In total, 54 records of Red Listed species were made.</p

Sources and sinks of greenhouse gases in the landscape : Approach for spatially explicit estimates

Climate change mitigation is a global response that requires actions at the local level. Quantifying local sources and sinks of greenhouse gases (GHG) facilitate evaluating mitigation options. We present an approach to collate spatially explicit estimated fluxes of GHGs (carbon dioxide, methane and nitrous oxide) for main land use sectors in the landscape, to aggregate, and to calculate the net emissions of an entire region. Our procedure was developed and tested in a large river basin in Finland, providing information from intensively studied eLTER research sites. To evaluate the full GHG balance, fluxes from natural ecosystems (lakes, rivers, and undrained mires) were included together with fluxes from anthropogenic activities, agriculture and forestry. We quantified the fluxes based on calculations with an anthropogenic emissions model (FRES) and a forest growth and carbon balance model (PREBAS), as well as on emission coefficients from the literature regarding emissions from lakes, rivers, undrained mires, peat extraction sites and cropland. Spatial data sources included CORINE land use data, soil map, lake and river shorelines, national forest inventory data, and statistical data on anthropogenic activities. Emission uncertainties were evaluated with Monte Carlo simulations. Artificial surfaces were the most emission intensive land-cover class. Lakes and rivers were about as emission intensive as arable land. Forests were the dominant land cover in the region (66%), and the C sink of the forests decreased the total emissions of the region by 72%. The region's net emissions amounted to 4.37 +/- 1.43 Tg CO2-eq yr(-1), corresponding to a net emission intensity 0.16 Gg CO2-eq km(-2) yr(-1), and estimated per capita net emissions of 5.6 Mg CO2-eq yr(-1). Our landscape approach opens opportunities to examine the sensitivities of important GHG fluxes to changes in land use and climate, management actions, and mitigation of anthropogenic emissions. (C) 2021 The Authors. Published by Elsevier B.V.peerReviewe