Search

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.

Half of the Finnish peatland area is drained for forestry. The remaining undrained peatlands are not all pristine, because surrounding drainage may disturb their hydrology. This concerns especially aapa mires, which are dependent on hydrological connections to their upper catchments. We investigated the amount and sizes of Finnish undrained peatlands, the drainage state of their margins, and the naturalness of aapa mires in large (> 50 ha) undrained peatland areas, using a GIS analysis based on digital map data, aerial images and an elevation model. The results show that a majority (66.7 % of count, 84.7 % of area) of undrained peatland areas have at least partly drained margins. Drainage activities commonly disturb minerotrophic water discharge to aapa mires. In the middle boreal zone, on average 41.6 % (median 42.8 %) of the catchment area of aapa mires is such that hydrological connection with the mire is disturbed by intervening drainage. In the southern boreal zone, the figure is 25.1 % (median 16.1 %), and in the southern part of the northern boreal zone 24.2 % (median 9.9 %). Possible implications of the disturbances include tree encroachment, hummock formation and fen–bog transition, which is likely to cause a loss of biodiversity but could potentially increase peat growth and carbon sequestration.

1. Growing bioeconomy is increasing the pressure to clear-cut drained peatland forests. Yet, the cumulative effects of peatland drainage and clear-cutting on the biodiversity of recipient freshwater ecosystems are largely unknown. 2. We studied the isolated and combined effects of peatland drainage and clear-cutting on stream macroinvertebrate communities. We further explored whether the impact of these forestry-driven catchment alterations to benthic invertebrates is related to stream size. We quantified the impact on invertebrate biodiversity by comparing communities in forestry-impacted streams to expected communities modelled with a multi-taxon niche model. 3. The impact of clear-cutting of drained peatland forests exceeded the sum of the independent effects of drainage and clear-cutting, indicating a synergistic interaction between the two disturbances in small streams. Peatland drainage reduced benthic biodiversity in both small and large streams, whereas clear-cutting did the same only in small streams. Small headwater streams were more sensitive to forestry impacts than the larger downstream sites. 4. We found 11 taxa (out of 25 modelled) to respond to forestry disturbances. These taxa were mainly different from those previously reported as sensitive to forestry-driven alterations, indicating the context dependence of taxonomic responses to forestry. In contrast, most of the functional traits previously identified as responsive to agricultural sedimentation also responded to forestry pressures. In particular, taxa that live temporarily in hyporheic habitats, move by crawling, disperse actively in water, live longer than 1 year, use eggs as resistance form and obtain their food by scraping became less abundant than expected, particularly in streams impacted by both drainage and clear-cutting. 5. Synthesis and applications. Drained peatland forests in boreal areas are reaching maturity and will soon be harvested. Clear-cutting of these forests incurs multiple environmental hazards but previous studies have focused on terrestrial ecosystems. Our results show that the combined impacts of peatland drainage and clear-cutting may extend across ecosystem boundaries and cause significant biodiversity loss in recipient freshwater ecosystems. This information supports a paradigm shift in boreal forest management, whereby continuous-cover forestry based on partial harvest may provide the most sustainable approach to peatland forestry.

Spatiotemporal information on historical peatland drainage is needed to relate past land use to observed changes in catchment hydrology. Comprehensive knowledge of historical development of peatland management is largely unknown at the catchment scale. Aerial photos and light detection and ranging (LIDAR) data enlarge the possibilities for identifying past peatland drainage patterns. Here, our objectives are (1) to develop techniques for semiautomatically mapping the location of ditch networks in peat-dominated catchments using aerial photos and LIDAR data, and (2) to generate time series of drainage networks. Our approaches provide open-access techniques to systematically map ditches in peat-dominated catchments through time. We focused on the algorithm in such a way that we can identify the ditch networks from raw aerial images and LIDAR data based on the modification of multiple filters and number of threshold values. Such data are needed to relate spatiotemporal drainage patterns to observed changes in many northern rivers. We demonstrate our approach using data from the Simojoki River catchment (3,160 km²) in northern Finland. The catchment is dominated by forests and peatlands that were almost all drained after 1960. For two representative locations in cultivated peatland (downstream) and peatland forest (upstream) areas of the catchment; we found total ditch length density (km/km²), estimated from aerial images and LIDAR data based on our proposed algorithm, to have varied from 2% to 50% compared with the monitored ditch length available from the National Land survey of Finland (NLSF) in 2018. A different pattern of source variation in ditch network density was observed for whole-catchment estimates and for the available drained-peatland database from Natural Resources Institute Finland (LUKE). Despite such differences, no significant differences were found using the nonparametric Mann-Whitney U test with a 0.05 significance level based on the samples of pixel-identified ditches between (1) aerial images and NLSF vector files and (2) LIDAR data and NLSF vector files.

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.

Highlights • Nutrient and SS estimations were predicted by comparing different approaches. • Peatland drainage strongly affected TN, TP, and SS loads and concentrations. • Uncertainty in estimates captured 29–90% of measured TN, TP, and SS values. • The uncertainty in export coefficients decreased with catchment size. Maintaining and improving surface water quality requires knowledge of nutrient and sediment loads due to past and future land-use practices, but historical data on land cover and its changes are often lacking. In this study, we tested whether land-use-specific export coefficients can be used together with satellite images (Landsat) and/or regional land-use statistics to estimate riverine nutrient loads and concentrations of total nitrogen (TN), total phosphorus (TP), and suspended solids (SS). The study area, Simojoki (3160 km2) in northern Finland, has been intensively drained for peatland forestry since the 1960s. We used different approaches at multiple sub-catchment scales to simulate TN, TP, and SS export in the Simojoki catchment. The uncertainty in estimates based on specific export coefficients was quantified based on historical land-use changes (derived from Landsat data), and an uncertainty boundary was established for each land-use. The uncertainty boundary captured at least 60% of measured values of TN, TP, and SS loads or concentrations. However, the uncertainty in estimates compared with measured values ranged from 7% to 20% for TN, 0% to 18% for TP, and 13% to 43% for SS for different catchments. Some discrepancy between predicted and measured loads and concentrations was expected, as the method did not account for inter-annual variability in hydrological conditions or river processes. However, combining historical land-use change estimates with simple export coefficients can be a practical approach for evaluating the influence on water quality of historical land-use changes such as peatland drainage for forest establishment.

We studied natural and forestry-drained peatlands to examine the effect of over 34 years lowered water table on the δ13C values of vegetation, bulk peat and subsoil. In the seven studied sites, δ13C in the basal peat layer was 1.1 and 1.2 ‰ lower than that of the middle-layer and surface layer, respectively. Furthermore, there was a positive correlation between the δ13C values of the basal and surface peat layers, possibly due to carbon (C) recycling within the peat column. In the same mire complex, natural fen peat δ13C values were lower than those of the nearby bog, possibly due to the dominance of vascular plants on fen and the generally larger share of recycled C in the fens than in the bogs. Furthermore, natural and 51 years previously drained fen and bog, on the opposite sides of a ditch on the same mire complex, showed no significant differences in δ13C values. Plant δ13C values were lower, while δ13C values of subsoil were higher in the drained than in the natural site of the fen. acceptedVersion

Mire ditching changes dramatically mire biodiversity. Thus, drainage network detection is an important factor when analysing the natural state of a mire. In this article, we propose a method for automated drainage network detection from raster digital terrain model created from high-resolution laser scanning data. Sparse logistic regression classifier with a large generic feature set and automated feature selection is used for classification. Broken segments are connected with polynomial modelling. The results showed that our method can accurately detect artificial drainage networks.

nonPeerReviewed

Ihmisen toiminta aiheuttaa muutoksia yhteisöissä maailmanlaajuisesti. Ihmisvaikutteiset, eli antropogeeniset häiriöt muuttavat ekosysteemien luonnollista häiriödynamiikkaa aikaansaaden ominaisuuksiltaan uudenlaisia ympäristöjä. Tällaiset ympäristöt ovat usein suosiollisempia kasvupaikkavaatimuksiltaan generalisteille vieraslajeille kuin vaateliaammille spesialistilajeille. Tämän seurauksena generalistilajit leviävät uusille alueille ja paikallisia spesialistilajeja häviää. Useiden spesialistilajien korvautuminen muutamalla generalistilajilla voi lisätä eri yhteisöjen välistä samankaltaisuutta eli johtaa taksonomiseen homogenisaatioon ja sitä kautta luonnon monimuotoisuuden vähenemiseen ja sukupuuttojen lisääntymiseen. Ojitetut suot toimivat hyvänä esimerkkinä ihmisen vaikutuksesta muuttuneista ympäristöistä. Suokasvillisuus on suhteellisen spesialisoitunutta soiden ominaisille olosuhteille, jotka muuttuvat suon ojituksen seurauksena. Aikaisemmista tutkimuksista ilmenee, että ojitus johtaa kasviyhteisöjen väliseen homogenisaatioon eri soiden välillä ja suokasvilajien korvautumiseen alueellisesti generalisteimmilla metsälajeilla. Tämän tutkielman tarkoituksena oli tutkia ojituksen vaikutuksia suokasviyhteisön spesialisaatioon. Selvittääkseni onko soiden olosuhteisiin spesialisoituneiden kasvilajien mahdollista sopeutua ojitettujen soiden uudenlaisiin olosuhteisiin ja lisääntyykö generalistilajien määrä yhteisössä ojituksen jälkeen, käytin 118 suomalaiselta suolta kerättyä aineistoa putkilokasvien ja sammalten suhteellisesta runsaudesta. Määritin jokaiselle lajeille ja putkilokasvi- ja sammalyhteisölle spesialisaatioarvon spesialisaatioindekseillä. Näitä arvoja analysoimalla selvitin vaikuttaako ojitus eri tavalla luonnontilaisten yhteisöjen generalisti- ja spesialistilajien esiintymiseen ja muuttaako ojitus kasviyhteisön spesialistien ja generalistien määrän suhdetta. Tulokset osoittavat, että spesialistien runsaus ja yleisyys vaihtelivat generalisteja enemmän luonnontilaisten ja ojitettujen soiden välillä. Generalistilajien esiintyminen oli samanlaista sekä luonnontilaisilla että ojitetuilla soilla, kun taas spesialistilajien runsaus ja yleisyys joko lisääntyivät tai vähenivät ojitetuilla soilla verrattuna luonnontilaisiin soihin. Spesialistilajit, jotka olivat kärsineet ojituksesta olivat suo-olosuhteisiin spesialisoituneita lajeja, jotka olivat spesialisteja myös alueellisesti tarkasteltuina. Spesialistit, jotka runsastuivat ojituksen seurauksena olivat sen sijaan lajeja, jotka ovat alueellisesti tarkasteltuna generalisteja metsälajeja, jotka olivat luonnontilaisilla soilla paikallisia spesialisteja. Mahdollisesti tällaisten lajien lisääntyminen ojitetuilla soilla aikaansai sen, että kasviyhteisöjen generalisti- ja spesialistilajien määrän suhde ei näyttänyt tilastollisesti merkitsevästi eroavan luonnontilaisten ja ojitettujen soiden välillä, vaikka alueellisesti spesialistien lajien määrä väheni. Anthropogenic activities account for changes in communities globally. Anthropogenic disturbances alter the natural disturbance dynamics of ecosystems thus creating environments with novel conditions. These environments are often more favorable to nonnative generalist species than to the more niche-confined specialists, hereby leading to the assisted spreading of generalists and to the decline of specialist species. The replacement of a variety of specialists with a few generalists can result in growing similarity among different communities i.e. taxonomic homogenization, which can itself lead to the decrease of biodiversity and to the increase on extinctions. Prime examples of environments affected by anthropogenic activities are drained peatlands. The conditions characteristic of peatlands, have resulted in relatively specialized vegetation in terms of habitat requirements that are no longer completely met after draining. Previous studies support the notion that drainage leads to the homogenization of plant communities between peatlands and to the directional change of specialized peatland species to more generalist forest species. The aim of this thesis was to study the effects of draining on the specialization of peatland vegetation. To test whether the plant species specialized to the pristine conditions are able to adapt to the new conditions of drained peatlands and whether the colonization of more broad-niched generalists increases after drainage, I used vascular plant and bryophyte relative abundance data collected from 118 peatland sites from around Finland. Specialization indexes were used to determine specialization rates for each individual plants species and bryophyte and vascular plant community. These rates were analysed to find out if the occurrence of generalists and specialist plant species of natural communities was affected differently by drainage and if drainage altered the specialist-generalist ratio of a plant community. The results show that the abundances and frequencies of specialist species differed more between pristine and drained peatlands than the ones of generalist species. The occurrence of generalist species was similar in both pristine and drained sites but specialist species had either increased or decreased both in abundance and frequency when comparing pristine sites to drained ones. Closer observations revealed that the decreased specialists were species specialized to specific peatland conditions thus appearing as specialist even on landscape level. The increased specialists were, however, landscape level generalists i.e. forest species that only appeared as specialists on pristine peatlands. Possibly because of the increase of such species in drained sites, the generalistspecialist ratios of plant communities seemed to not significantly differ between pristine and drained sites, even though the number of landscape level specialist species decreased.

Tutkielmassa selvitettiin turve- ja metsätalouden vaikutuksia Martinjärven ja Iso Kivijärven surviaissääskiyhteisöihin paleolimnologisen menetelmän avulla. Järvien sedimenttiprofiileita tarkasteltiin viimeisen 400 vuoden ajalta. Järvet ovat pieniä, matalia humusjärviä ja sijaitsevat Keski-Suomessa Keuruulla vierekkäisillä valuma-alueilla. Surviaissääskiyhteisöjen muutosten perusteella tutkittiin järvien rehevyystason ja humoosisuuden muutoksia ennen ja jälkeen metsätalouden ja turvetuotannon aloittamista. Soiden laajamittainen ojitus metsätalouden käyttöön alkoi 1960-luvulla molempien järvien valuma-alueilla. Martinjärven valuma-alueella aloitettiin lisäksi turpeen kaivu 1970- ja 1980-lukujen vaihteessa. Turvetuotantoalueiden jätevedet laskevat Martinjärven yläpuolisiin vesistöihin. Iso Kivijärveä käytettiin Martinjärven vertailujärvenä turvetuotannon osalta. Molempien järvien valuma-alueilla harjoitetaan myös peltoviljelyä. Surviaissääskiyhteisöjen muutoksia tarkasteltiin pääkomponenttianalyysin (PCA), syvännepohjaeläinindeksin (Profundal Invertebrate Community Metrics) ja surviaissäskiyhteisöjen monimuotoisuuden perusteella. Sedimenttiprofiilien alkuaineanalyysin perusteella havaittiin mineraalimaa-ainesten eroosion voimakas kasvu 1960-luvulta lähtien molempien järvien valuma-alueilla. Luonnontilassa molempien järvien surviaissääskilajisto oli meso-eutrofisille järville tyypillistä. 1960- ja 1970-lukujen ojitusten aikaan rehevyyttä ilmentävien taksonien osuus kasvoi ja karumpien vesien taksonien osuus väheni molemmissa järvissä. Surviaissääskijäänteiden perusteella järvien lievä rehevöityminen jatkui näihin päiviin saakka. Surviaissääskiyhteisöjen muutos rehevämmän elinympäristön lajistoksi oli Iso Kivijärvessä hieman voimakkaampaa kuin Martinjärvessä, mikä voi osittain selittyä järvien erilaisilla hydrologis-morfologisilla ominaisuuksilla. Turvetuotannon alkuvaihetta lukuun ottamatta Martinjärven surviaissääskiyhteisöissä ei havaittu pelkästään turvetuotantoon yhdistettävissä olevia muutoksia. Martinjärven lähivaluma-alueen metsätaloustoimenpiteiden vaikutuksen järven surviaissäskiyhteisöihin arvioitiin olleen kauempana sijaitsevien turvetuotantoalueiden ja peltojen vaikutusta merkittävämpää. Sedimentary chironomid remains of Lake Martinjärvi and Lake Iso Kivijärvi in Central Finland were studied from sediment cores covering the last 400 years. Both lakes are small, shallow and highly dystrophic forest lakes. The major aim of the study was to assess the effects of intensive forestry activities and peat mining on ecosystems of the lakes. The changes in the lakes' trophic status and degree of humosity were studied by using sedimentary chironomid remains. Extensive ditching of bogs for forestry within the catchments of both lakes was started in the 1960s. Peat mining in the catchment of Martinjärvi was started in the 1980s. Run off water from peat mining sites drains first to lakes situated above Martinjärvi. Iso Kivijärvi was used as a reference lake to assess the effects of peat mining on chironomid assemblages of Martinjärvi. There are also agricultural lands in the catchment areas of both lakes. The changes in chironomid communities were analyzed using Principal Component Analysis (PCA), Profundal Invertebrate Community Metrics (PICM) and diversity indices. Increased erosion of mineral soil starting from the 1960s was detected in chemical stratigraphies of 33 elements analyzed from the sediment cores. In the natural state the chironomid communities of both lakes consisted of taxa typical of meso-eutrophic waters. Since the 1960s their communities indicated slight eutrophication which continued until recent. The change in the chironomid assemblages was greater in Iso Kivijärvi. Differences in hydromorphological properties of study lakes were partly responsible for the fact that environmental changes and effects of eutrophication remained smaller in Martinjärvi than in the reference lake. Change in chironomid communities of Martinjärvi in early 1980s could be partly related to peat mining. Otherwise the effects of peat mining on the chironomid communities could not be separated from the effects of forestry. As the land use adjacent to the shoreline of Martinjärvi consists almost exclusively of forestry, the effects of forestry practices on chironomid communities of Martinjärvi were assumed to be greater than the effects of peat mining sites and fields situated further away.

Metsänhoitajien jatkokurssit 1938. 4.

Metsänhoitajien jatkokurssit 1937. 3.

Mitä näkökohtia on otettava huomioon ojitettaessa vesiperäisiä maita metsänkasvua varten.

Metsänhoitajien jatkokurssit 1935.

Metsänhoitajien jatkokurssit 1935.

Suoluonto on hyvin vaihtelevaa, koska suolla vaihtelevat märkyys ja ravinteisuus ja niiden seurauksena myös puustoisuus. Suoluonnon tärkein säätelijä on märkyys – lähellä maanpintaa oleva vedenpinta. Vaikka kaikki suot ovat märkiä, suon märkyys myös vaihtelee paljon. Kuivimmillaan suo muistuttaa kivennäismaan metsää, ja usein suo vaihettuukin saumattomasti ympäröiväksi metsäksi. Märimmillään suo muistuttaa jo matalaa vesistöä ja vaihettuu rantakosteikoihin ja vesistöihin. Suo voi olla ravinteisuudeltaan rehevä tai karu. Rehevässä ääripäässä suolle valuu ravinteikasta vettä ympäristöstä tai kasvillisuus saa ohuen turvekerroksen läpi ravinteita ravinteikkaasta kivennäismaasta. Karussa ääripäässä turvetta on kertynyt niin paksu kerros, että kasvien juuret eivät yllä ottamaan ravinteita alla olevasta kivennäismaasta. Myöskään ympäristöstä ei valu ravinteikasta vettä suon reunaa korkeammaksi kohonneelle suon keskiosalle, ja kasvillisuus on sadeveden mukana tulevien ravinteiden varassa. Lisäksi turpeen kertyminen ja suon läpi virtaavan veden väheneminen happamoittavat turvetta, mikä vaikeuttaa kasvien ravinteiden ottoa. Ravinteisuuden ja märkyyden lisäksi aluskasvillisuuden kasvuoloihin vaikuttaa valon määrä, jota säätelee puuston varjostus. Runsaspuustoisimmat suot ovat varjoisia ja reheviä kuusi- ja lehtipuuvaltaisia korpia tai karumpia mäntyvaltaisia rämeitä. Mitä märempi ja karumpi suo on, sitä vähäisempää puusto on. Märimmät suot ovat ravinteisuudesta riippumatta puuttomia lettoja ja nevoja. Karuimmilla puustoisilla soilla kasvaa niin kitukasvuinen ja harva männikkö, ettei se käytännössä varjosta aluskasvillisuutta. Ojitus vähentää suoluonnon vaihtelua. Kun suo ojitetaan metsätaloutta varten, märkyyden vaihtelu vähenee ja jäljelle jää ravinteisuuden vaihtelu. Tällöin suo alkaa kehittyä aluskasvillisuudeltaan kivennäismaan metsää muistuttavaksi turvekankaaksi. Myös metsänhoito ja hakkuut muuttavat kasvillisuutta. Jos suo raivataan maataloutta varten, kuivatuksen lisäksi suo muokataan viljelyyn sopivaksi kalkituksin ja lannoituksin ja suokasvillisuus raivataan viljelykasvien tieltä. Turpeennostoa varten suo raivataan kasvittomaksi turvekentäksi.