Bjørn Kløve

Seniorforsker

(+358) 40 594 45 14
bjorn.klove@nibio.no

Sted
Ås - Bygg F20

Besøksadresse
Fredrik A. Dahls vei 20, 1430 Ås

Sammendrag

Cultivated organic soils account for ∼7% of Norway’s agricultural land area, and they are estimated to be a significant source of greenhouse gas (GHG) emissions. The project ‘Climate smart management practices on Norwegian organic soils’ (MYR), commissioned by the Research Council of Norway (decision no. 281109), aims to evaluate GHG (e.g. carbon dioxide, methane and nitrous oxide) emissions and impacts on biomass productivity from three land use types (cultivated, abandoned and restored) on organic soils. At the cultivated sites, impacts of drainage depth and management intensity will be measured. We established experimental sites in Norway covering a broad range of climate and management regimes, which will produce observational data in high spatiotemporal resolution during 2019-2021. Using state-of-the-art modelling techniques, MYR aims to predict the potential GHG mitigation under different scenarios. Four models (BASGRA, DNDC, Coup and ECOSSE) will be further developed according to the soil properties, and then used independently in simulating biogeochemical processes and biomass dynamics in the different land uses. Robust parameterization schemes for each model will be based in the observational data from the project for both soil and crop combinations. Eventually, a multi-model ensemble prediction will be carried out to provide scenario analyses by 2030 and 2050. By integrating experimental results and modelling, the project aims at generating useful information for recommendations on environment-friendly use of Norwegian peatlands.

Sammendrag

Cultivated organic soils (7-8% of Norway’s agricultural land area) are economically important sources for forage production in some regions in Norway, but they are also ‘hot spots’ for greenhouse gas (GHG) emissions. The project ‘Climate smart management practices on Norwegian organic soils’ (MYR; funded by the Research Council of Norway, decision no. 281109) will evaluate how water table management and the intensity of other management practices (i.e. tillage and fertilization intensity) affects both GHG emissions and forage’s quality & production. The overall aim of MYR is to generate useful information for recommendations on climate-friendly management of Norwegian peatlands for both policy makers and farmers. For this project, we established two experimental sites on Norwegian peatlands for grass cultivation, of which one in Northern (subarctic, continental climate) and another in Southern (temperate, coastal climate) Norway. Both sites have a water table level (WTL) gradient ranging from low to high. In order to explore the effects of management practices, controlled trials with different fertilization strategies and tillage intensity will be conducted at these sites with WTL gradients considered. Meanwhile, GHG emissions (including carbon dioxide, methane and nitrous oxide), crop-related observations (e.g. phenology, production), and hydrological conditions (e.g. soil moisture, WTL dynamics) will be monitored with high spatiotemporal resolution along the WTL gradients during 2019-2021. Besides, MYR aims at predicting potential GHG mitigation under different scenarios by using state-of-the-art modelling techniques. Four models (BASGRA, Coup, DNDC and ECOSSE), with strengths in predicting grass growth, hydrological processes, soil nitrification-denitrification and carbon decomposition, respectively, will be further developed according to the soil properties. Then these models will be used independently to simulate biogeochemical and agroecological processes in our experimental fields. Robust parameterization schemes will be based on the observational data for both soil and crop combinations. Eventually, a multi-model ensemble prediction will be carried out to provide scenario analyses by 2030 and 2050. We will couple these process-based models with optimization algorithm to explore the potential reduction in GHG emissions with consideration of production sustenance, and upscale our assessment to regional level.

Til dokument

Sammendrag

Management of peat soils is regionally important as they cover large land areas and have important but conflicting ecosystems services. A recent management trend for drained peatlands is the control of greenhouse gases (GHG) by changes in agricultural practices, peatland restoration or paludiculture. Due to complex antagonistic controls of moisture, water table management can be difficult to use as a method for controlling GHG emissions. Past studies show that there is no obvious relationship between GHG emission rates and crop type, tillage intensity or fertilization rates. For drained peat soils, the best use options can vary from rewetting with reduced emission to efficient short term use to maximize the profit per amount of greenhouse gas emitted. The GHG accounting should consider the entire life cycle of the peatland and the socio-economic benefits peatlands provide locally. Cultivating energy crops is a viable option especially for wet peat soils with poor drainage, but harvesting remains a challenge due to tractability of wet soils. Paludiculture in lowland floodplains can be a tool to mitigate regional flooding allowing water to be stored on these lands without much harm to crops. This can also increase regional biodiversity providing important habitats for birds and moisture tolerant plant species. However, on many peatlands rewetting is not possible due to their position in the landscape and the associated difficulty to maintain a high stable water table. While the goal of rewetting often is to encourage the return of peat forming plants and the ecosystem services they provide such as carbon sequestration, it is not well known if these plants will grow on peat soils that have been altered by the process of drainage and management. Therefore, it is important to consider peat quality and hydrology when choosing management options. Mapping of sites is recommended as a management tool to guide actions. The environmental status and socio-economic importance of the sites should be assessed both for continued cultivation but also for other ecosystem services such as restoration and hydrological functions (flood control). Farmers need advice, tools and training to find the best after-use option. Biofuels might provide a cost-efficient after use option for some sites. Peat extraction followed by rewetting might provide a sustainable option as rewetting is often easier if the peat is removed, starting the peat accumulation from scratch. Also this provides a way to finance the after-use. As impacts of land use are uncertain, new policies should consider multiple benefits and decisions should be based on scientific evidence and field scale observations. The need to further understand the key processes and long term effects of field scale land use manipulations is evident. The recommended actions for peatlands should be based on local condition and socio-economic needs to outline intermediate and long term plans.

Til dokument

Sammendrag

Peatland drainage results in several environmental impacts such as release of greenhouse gas to the atmosphere and leaching of nutrients to watercourses. These hazardous environmental effects can partly be controlled with soil management, and different drainage and remediation practices. Grading is a new method developed for soils with low conductivity suffering from poor drainage, water logging and ice. The soil surface is graded towards the ditch to increase surface runoff and drainage. The present study compares environmental effects of peatland grading compared to traditional intense pipe drainage. Detailed measurements of hydrology, climate, leaching and gas emissions were carried out at adjacent drainage areas with grass cultivation. Additional measurements were made at plots that were abandoned, cultivated with perennial crops, and remained as pristine peatlands. The results show that the leaching of nutrients is highest from pipe drainage. Climate gas emission was considerably higher at all managed sites than from the reference pristine site. Drainage, soil hydrology and soil nutrient status seemed to control gas emissions. The gas emissions were higher than assumed for Norwegian cold conditions. The results confirm observations made on peat soils in other climatic regions. The highest emissions of CO2 was observed when the soil temperature was high and groundwater table low. The N2O emission showed a large variation with no clear pattern. However, at some locations it peaked after a dry period when NO3-N was leached. More CH4 was emitted from the intensively drained site than the graded site, but more CO2 was emitted from the graded site. The difference in leaching and emission properties is partly due to differences in near surface hydrology. At grade sites, a faster runoff response to rainfall occur probably due to shallow throughfall or overland flow which provides better drainage. Also, the graded site was prepared recently, and this can have exposed fresh peat for decay. Therefore the drainage history must be well known in peatland studies as peat change in time due to drainage and cultivation. Abandoned peat field continue to leach greenhouse gases in a same way as cultivated sites.

Sammendrag

The Skjønhaug constructed wetland (CW) is a free surface water (FSW) wetland polishing chemically treated municipal wastewater in southeastern Norway and consists of three ponds as well as trickling, unsaturated filters with light weight aggregates (LWA). Fluxes of nitrous oxide (N2O) and methane (CH4) have been measured during the autumn, winter and summer from all three ponds as well as from the unsaturated filters. Physicochemical parameters of the water have been measured at the same localities. The large temporal and spatial variation of N2O fluxes was found to cover a range of -0.49 to 110 mg N2O-N m-2 day-1, while the fluxes of CH4 was found to cover a range of -1.2 to 1900 mg m-2 day-1. Thus, both emission and consumption occurred. Regarding fluxes of N2O there was a significant difference between the summer, winter and autumn, with the highest emissions occurring during the autumn. The fluxes of CH4 were, on the other hand, not significantly different with regard to seasons. Both the emission of N2O and CH4 was positively influenced by the amount of total organic carbon (TOC). The measured fluxes of N2O and CH4 are in the same range as those reported from other CWs treating wastewater. There was an approximately equal contribution to the global warming potential from N2O and CH4.

Sammendrag

Myrjord dekker 2-3 % av verdens landareal og inneholder ca en tredel av jordas lager av organisk karbon og omtrent like mye carbon som i atmosfæren. Drenering og dyrking av myr fører til en mineralisering av organisk materiale. Denne artikkelen omhandler emisjon av drivhusgasser fra dyrket myr i Nord-Norge. CO2-emisjonen økte med temperaturen, mens tilsvarende effekt ikke kunne påvises for N2O- og CH4-emisjonen. Estimert netto emisjon av drivhusgasser fra rør-grøftet myr var ca 2,2 kg for CO2, 0,03 kg for CH4 og 0,13 kg for N2O, uttrykt i CO2-ekvivalenter. Netto C-tap var ca 0,6 kg C per m2 og år. Karbontap kan derfor betraktes som jordforringelse når en tar hensyn til klimagassemisjonen. Resultatene viste betydningen av CO2-emisjonen fra dyrket myr i nord, som var ca 17 ganger høyere enn N2O-emisjonen som CO2-ekvivalenter.

Sammendrag

The potential atmospheric impact of constructed wetlands (CWs) should be examined as there is a worldwide increase in the development of these systems. Fluxes of N2O, CH4, and CO2 have been measured from CWs in Estonia, Finland, Norway, and Poland during winter and summer in horizontal and vertical subsurface flow (HSSF and VSSF), free surface water (FSW), and overland and groundwater flow (OGF) wetlands. The fluxes of N2O-N, CH4-C, and CO2-C ranged from "2.1 to 1000, "32 to 38 000, and "840 to 93 000 mg m"2 d"1, respectively. Emissions of N2O and CH4 were significantly higher during summer than during winter. The VSSF wetlands had the highest fluxes of N2O during both summer and winter. Methane emissions were highest from the FSW wetlands during wintertime. In the HSSF wetlands, the emissions of N2O and CH4 were in general highest in the inlet section. The vegetated ponds in the FSW wetlands released more N2O than the non-vegetated ponds. The global warming potential (GWP), summarizing the mean N2O and CH4 emissions, ranged from 5700 to 26000 and 830 to 5100 mg CO2-equivalents m"2 d"1 for the four CW types in summer and winter, respectively. The wintertime GWP was 8.5-89.5% of the corresponding summertime GWP, which highlights the importance of the cold season in the annual greenhouse gas release from north temperate and boreal CWs. However, due to their generally small area North European CWs were suggested to represent only a minor source for atmospheric N2O and CH4.

Sammendrag

Content of 18O, 2H, 3H and geochemical components in rainfall, stream water, peat water and bedrock groundwater in four headwater catchments were compared to reveal differences in sources of runoff and hydrological vulnerability to tunnel drainage during summer. Water previously stored within the catchments was the predominant component of streamflow during small and moderate events. The proportion of event water increased at high discharge in autumn. Neither the isotopic nor the hydrochemical composition of stream water indicated any considerable contribution from old bedrock groundwater. Stream water hydrochemistry revealed clear influence of soil water pathways. The differences in land cover could be seen in water quality and runoff generation. Water storage and mixing in lakes and lowland wetlands reduced fluctuations in runoff and water quality. Runoff retention and the solute trapping effect in peatlands were most efficient in flat areas near the catchment outlet. In lowflow periods fluxes from hillslopes were of minor importance compared to discharges from wetland water storage. Water delivery from hillslopes with thin till cover (

Sammendrag

Hydraulics of subsurface flow filters (SSF) was studied by measurement of soil hydraulic conductivity (K) variation and performing tracer tests in two SSF filters consisting of 1-4 mm Ca rich sand (shell sand). Soil samples were carefully taken at several locations in Filter I. A tracer experiment was conducted in the undisturbed Filter II using KI. The measured K variability in Filter I was used to analyze the variations in tracer breakthrough. The spatial distribution of K was obtained by fitting a variogram to observed data and interpolation using Kriging. The tracer residence probability density function (PDF) was determined by modelling the tracer movement with a 3-D groundwater model. The observed and simulated tracer arrival was compared for cases with constant K, constant K and dispersion (D), and for spatially variable K and dispersion. The results show that groundwater models were well suited to simulate solute movement in the SSF system studied. An almost perfect fit to observed tracer PDF was obtained when variable K and dispersion was included in the model. This indicates that information on K variability and dispersion is important for studying solute movement in SSF constructed wetlands.

Sammendrag

Controlled experiments were carried out in a meso-scale sub-surface flow constructed sand filter treating municipal wastewater from a single household. The system consisted of a 50 cm high vertical flow column (pre-filter) with unsaturated flow and a 3 m long horizontal sub-surface flow unit (main filter) with saturated flow. Fluxes of nitrogen and carbon were analysed in four different operating conditions (low and high loading, with and without the pre-filter unit). Water samples were taken from the inlet, the outlet and within the sand filter at different depths and locations and analysed for water quality (Tot N, NO3-N, NH4-N, TOC, DOC, CODcr, BOD5, SS, pH and EC) and dissolved gas content (N2O, CH4 and CO2). Emissions of N2O, CH4 and CO2 were measured with the closed-chamber technique adjacent to water quality sampling points. The results show that pre-filtering in a vertical, unsaturated flow column changed the incoming ammonium to nitrate during low loading. During high loading part of the ammonium nitrified in the pre-filter was lost by denitrification. Within the horizontal main filter there were two pathways for the incoming nitrate: denitrification and dissimilatory nitrate reduction to ammonium (DNRA).

Sammendrag

The suitability of shell sand as a P sorbent has been tested both with laboratory batch experiments as well as in a sub-surface flow (SSF) meso-scale constructed sand filter treating municipal wastewater from a single household. The batch experiments suggest that retention of P in shell sand occurs both as sorption and precipitation. The soil-water ratio was found to be a crucial parameter when performing laboratory batch experiments. The maximum retention capacity was about 8000 and 800 mg P kg-1 sand, and the Kd was 33.7 and 82.9 L kg-1 for soil-water ratios of 5 g "75 mL and 50 g " 50 mL, re-spectively. The average total accumulated P concentration in samples from the SSF sand filter was 335 mg P kg-1. The Kd value based on [PO43-] and accumulated concentration of inorganic P in the SSF filter was 89.8 L kg-1. Thus the batch experiments overestimated the retention capacity of shell sand in real sand filter systems, however, a ratio of 50-50 gave a more reasonable estimate than a ratio of 5-75. The Kd value from batch samples with a ratio of 50-50 also gave a good estimate of the Kd value in the constructed sand filter. Ca-P was found to be the predominant form of P mineral in samples col-lected from the SSF sand filter. Some Al-P, loosely bounded P and occluded P were also present in the sand.

Sammendrag

Laboratory incubations with varying O2 and NO3 concentrations were performed with a range of filter materials used in constructed wetlands (CWs). The study included material sampled from functioning CWs as well as raw materials subjected to laboratory pre-incubation. 15N-tracer techniques were used to assess the rates of denitrification versus dissimilatory nitrate reduction to ammonium (DNRA), and the relative role of nitrification versus denitrification in producing N2O. The N2O/(N2+N2O) product ratio was assessed for the different materials. Sand, shell sand, and peat sustained high rates of denitrification. Raw light weight aggregates (LWA) had a very low rate, while in LWA sampled from a functioning CW, the rate was similar to the one found in the other materials. The N2O/(N2+N2O) ratio was very low for sand, shell sand and LWA from functioning CWs, but very high for raw LWA. The ratio was intermediate but variable for peat. The N2O produced by nitrification accounted for a significant percentage of the N2O accumulated during the incubation, but was dependent on the initial oxygen concentration. DNRA was significant only for shell sand taken from a functioning CW, suggesting that the establishment of active DNRA is a slower process than the establishment of a denitrifying flora.

Sammendrag

Fosforbindingsegenskapene til de to filtermaterialene Filtralite-PTM og Fosen skjellsand er blitt sammenlignet i et pilotskala-anlegg. Anlegget bestod av to kar i plexiglass (3m x 0,8m x 0,29m), ett for hvert materiale. De to karene ble tilført en kunstig P-løsning (6 mg P l-1) i 18 måneder. Fosforkonsentrasjonen i innløp, utløp og i grunnvannsrør jevnt fordelt i karene ble målt igjennom hele forsøksperioden. Mengden akkumulert total P (TP) ble målt i prøver fra filtermaterialet ved forsøkets slutt. Resultatene viser at TP i første del av karet var mye høyere for Filtralite-PTM enn for Fosen skjellsand, henholdsvis 4000 og 330 mg P kg-1. Dette tilsvarer 2000 og 330 g P m-3 filtermateriale. I begge karene sank konsentrasjonen av TP mot utløpet. De første 0,9 m av karet med Fosen skjellsand var mettet med P, mens bare 0,3 m av karet med Filtralite-PTM var mettet. Resultatene viser også at for å beregne en realistisk levetid for et filteranlegg, må en gjennomsnittelig bindingskapasitet (basert på målinger av TP i materi-alprøver fra hele anlegget) brukes. Dette fordi bare materialet i de fremre deler av et anlegg vil ha oppnådd maksimal bindingskapasitet når utløpskonsentrasjonen er høyere enn kravet (ofte satt til 1 mg P l-1). En slik gjennomsnittlig bindingskapasitet bør baseres på målinger av TP i materiale fra et anlegg der utløpskonsentrasjonen nettopp har nådd 1 mg P l-

Sammendrag

Constructed wetlands remove pollutants by physical, chemical, and biological processes. The pollutant removal efficiency is strongly dependent on the hydraulic characteristics of the wetlands. Hydrology highly affects the hydraulic flow regime and thus has a huge effect on the treatment processes. The current design criteria based on the simplifying assumptions of plug flow and first order decay of pollutants do not accurately predict wetland performance. The lifetime of a filter material may also be strongly affected by a non-uniform flow pattern. In this paper, the effects of different hydrological factors on the transport and removal of pollutants in subsurface-flow (SSF) constructed wetland are reviewed from the research literature, and is examined by experiments and numerical simulations. Results from tracer experiments (Br-) in small-scale subsurface-flow wetlands, with and without vegetation, are presented. Analytical and numerical solutions were used to describe the experimental observations. A three-dimensional finite-difference flow model (MODFLOW) coupled to the transport model (MT3DMS) was used to obtain the numerical solutions. In a series of transport simulations, hydraulic parameters, hydraulic conductivity, effective porosity, and longitudinal dispersivity, were estimated. Results showed that the estimated hydraulic conductivity values were reasonably close to the laboratory-measured values. Although the simulations gave a good representation of the effluent breakthrough curve in the experimental containers, it did not describe the flow pattern within the volume very well. Non-isotropic effects or heterogeneities in the Ks values and/or Kd values could be the cause of inconsistencies in local observations. The field scale experiment showed a large variability in soil physical properties, which gave, rise to unexpected breakthrough curves at the observation wells and at the outlet. Thus, at a field scale it was even more difficult to capture the observed phenomena in Visual modflow, heterogeneities might have given rise to preferential flow paths, data from this experiment have not yet been fully analysed, and further simulations are planned to include heterogeneity. Although we have not yet been able to describe sufficiently the factors, which give rise to the heterogeneous flow pattern, simulations in Modflow are very useful to improve understanding and design of constructed wetlands. To be able to solve the transport equations analytically the system has to be simplified to a larger degree than in a numerical model, but the analytical solutions are still useful to get a rough idea of the flow and transport processes.

Sammendrag

Jordforsk utfører hydrologisk overvåking over tunneltraseen Grualia - Bruvoll. Avrenning i sommerperioden overvåkes i fem mindre nedbørfelt. Nedbør og jordfuktighet registreres i utvalgte felt. Vannstandmålinger utføres i fem tjern og vann, fjorten myrbrønner og fire fjellbrønner. Kvantifisering av tunneldreneringseffekter på tilsig og avrenning fra overvåkingsfeltene vil kreve omfattende hydrologisk analysearbeid og tilstrekkelig datamateriale. Avrenningsmålinger foreligger bare for en kort periode etter gjennomført tunneldriving. Målingene i juni og juli 2002 viste lignende vannstand i myrbrønnene som i 2001. Vannivåene i myrbrønnene er vurdert å ligge innenfor det naturlige variasjonsområdet for slike naturtyper. Vannstands-senking i myr etter tunneldrenering slår særlig ut etter lengre tørrværsperioder. Målinger er ikke utført under slike forhold. Det har vært høy grunnvannstand og små vannstands-svingninger i fjellbrønnene ved Munkerudstjerna. Fjellbrønnene i svakhetssonen i berggrunnen på vestsida av Langvatnet viste markante tunneldreneringseffekter. Etter å ha ligget på om lag 40 meters dyp fra høsten 2000 til våren 2002, sank grunnvannsnivået etter tunneldriving i undergrunnen. Under de rådende tilsigsforhold utover høsten 2002 har vannspeilet i brønnene ligget rundt 50 meters dyp. Grunnvanns-situasjonen er endret fra en tilstand med grunnvannsoverflaten flere meter over Langvatnet og Hesthagatjern til en situasjon med grunnvannsoverflaten flere meter under overflaten av vannene. En slik endring vil forandre det geohydrologiske strømningsmønsteret. Nord for tunneltraseen finnes i og nedstrøms svakhetssonen kilder og rike og intermeditære myrer. De økologiske betingelsene for kildene og myrene vil kunne forandres hvis det lokale geohydrologiske strømningsmønsteret endres. En viss påvirkning av utløpsbekken fra Langvatnet under langvarige tørrværsperioder kan ikke utelukkes dersom lekkasjene til tunnelen er store.

Sammendrag

List of posters: * Virtanen, J. Reponen, I. and Peltomaa, R.: The Finnish sub surface drainage target program * Fausey, N. R. Recycling of Runoff and Subsurface Drainage Water in the Midwest U.S. (Wetland Reservoir Subirrigation Systems - WRSIS) * Haataja, K. Viability of alternative subsurface drainage and irrigation systems * Øygarden, L. JOVÅ - the Norwegian soil and water monitoring program * Mikkonen, A.K. and Kløve, B. Measurement of peat hydraulic properties

Sammendrag

Erosjon og næringsstofftap overvåkes i en rekke mindre nedbørfelter som representerer ulik jordbruksdrift, klima og jordsmonn i Norge. Overvåkingsprogammet ble satt i gang 1992, men en del av nedbørfeltene har målinger fra midten av 80-tallet. Erosjon og næringsstofftap er beregnet for agrohydrologiske år, 1. mai 1999– 30. april 2000. Året 1999/2000 var preget av generelt høye nitrogentap i Grimestadbekken, Vasshaglona og Hotrankanalen (10-12 kg N/dekar), mens det for de øvrige feltene var mindre enn 5 kg N/dekar. I kornfeltene på Østlandet var nitrogentapet 2-5 kg/dekar, som er på nivå med middeltapene for hele måleperioden. I nedbørfelt med overveiende grasdyrking varierte nitrogentapene fra 1-5 kg/dekar, størst i nedbørfelt med størst husdyrtetthet. Svært store fosfortap ble registrert i Grimestadbekken (1220 g/dekar) og Vasshaglona (720 g/dekar) i 1999/00. I Hotrankanalen var fosfortapet 430 g/dekar. I kornfeltene i Akershus varierte fosfortapet 120-340 g/dekar, mens det på Hedmarken var 40 g/dekar. I nedbørfelter med overveiende grasdyrking ble det registret fosfortap på 30-500 g/dekar i 1999/00. Nedbørfeltet med myrjord ga de største tapene. I 1999/00 er det også målt svært høye jordtap i Grimestadbekken (730 kg/dekar) og Vasshaglona (140 kg/dekar). I Skuterud-, Mørdrebekken og Hotrankanalen var jordtapet ca 260 kg/dekar, mens det i Naurstadbekken og Vasshaglona lå jordtapene på ca 130 kg/dekar. Jordtapene fra Rømua var meget lave (60 kg/dekar) i 1999/00, sammenlignet med andre felt i tilsvarende områder. Kolstad-, Time- og Volbubekken hadde jordtap på ca 10 kg/dekar. Vannkvaliteten i jordbrukspåvirkede innsjøer er klassifisert i intervallet mindre god til meget dårlig.