Shift in tree species changes the belowground biota of boreal forests

The replacement of native birch with Norway spruce has been initiated in Norway to increase long-term carbon storage in forests. However, there is limited knowledge on the impacts that aboveground changes will have on the belowground microbiota. We examined which effects a tree species shift from birch to spruce stands has on belowground microbial communities, soil fungal biomass and relationships with vegetation biomass and soil organic carbon (SOC). Replacement of birch with spruce negatively influenced soil bacterial and fungal richness and strongly altered microbial community composition in the forest floor layer, most strikingly for fungi. Tree species-mediated variation in soil properties was a major factor explaining variation in bacterial communities. For fungi, both soil chemistry and understorey vegetation were important community structuring factors, particularly for ectomycorrhizal fungi. The relative abundance of ectomycorrhizal fungi and the ectomycorrhizal : saprotrophic fungal ratio were higher in spruce compared to birch stands, particularly in the deeper mineral soil layers, and vice versa for saprotrophs. The positive relationship between ergosterol (fungal biomass) and SOC stock in the forest floor layer suggests higher carbon sequestration potential in spruce forest soil, alternatively, that the larger carbon stock leads to an increase in soil fungal biomass.publishedVersio

Oppdatering av kunnskapsgrunnlag for klimatiltak i skog: Gjennomgang av 11 utvalgte tiltak i bestandsskogbruket

På oppdrag fra Miljødirektoratet og Landbruksdirektoratet har vi gått gjennom kunnskapsstatus på 11 ulike tiltak utvalgt av direktoratene. Alle tiltakene ligger innenfor det tradisjonelle bestandsskogbruket. Tiltakene er vurdert ut fra hvordan de kan øke skogens netto CO2-opptak (karbonlagring), men for noen tiltak også betydning for andre klimagasser og for biogeofysiske effekter som albedo. Utvalget er ikke uttømmende, og også andre tiltak gjennom omløpet vil ha effekt på skogens CO2-opptak. Potensielle substitusjonseffekter gjennom tilgang på mer tømmer eller tømmer med høyere kvalitet er ikke inkludert. Klimatilpasning har vært med i vurderingen av alle tiltak. Det er korte omtaler av tiltakenes effekter på naturmangfold.Oppdatering av kunnskapsgrunnlag for klimatiltak i skog: Gjennomgang av 11 utvalgte tiltak i bestandsskogbruketpublishedVersio

Økologiske effekter av skogbrann

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Jordsmonnet er det største karbonlageret på landjorda

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Boreal tree species change as a climate mitigation strategy: impact on ecosystem C and N stocks and soil nutrient levels

To increase the annual uptake of CO2 as well as the long-term storage of carbon (C) in forests, the Norwegian government consider large-scale replacements of native, deciduous forests with faster-growing species like Norway spruce. To assess the effects of tree species change on ecosystem C and nitrogen (N) stocks and soil chemistry, we used a paired plot approach including stands of native downy birch and planted 45 – 60-year-old Norway spruce. The birch stands were used as reference for the assessment of differences following the tree species change. We found significantly higher C and N stocks in living tree biomass in the spruce stands, whereas no significant differences were found for dead wood. The cover of understory species groups, and the C and N stocks of the aboveground understory vegetation was significantly higher in the birch stands. The tree species change did not affect the soil organic carbon (SOC) stock down to 1 m soil depth; however, the significantly higher stock in the forest floor of the spruce stands suggested a re-distribution of SOC within the profile. There was a significant positive correlation between the SOC stock down to 30 cm soil depth and the total ecosystem C stock for the birch stands, and a negative correlation for the spruce stands. Significant effects of tree species change were found for C and N concentrations, C/N, exchangeable acidity, base saturation, and exchangeable Ca, K, Mg, Na, S, and Fe in the organic horizon or the upper mineral soil layer. The total ecosystem C stock ranged between 197 and 277 Mg ha-1 for the birch stands, and 297 and 387 Mg ha-1 for the spruce stands. The ecosystem C accumulation varied between 32 and 142 Mg ha-1 over the past 45-60 years, whereas the net ecosystem C capture was considerably lower and potentially negative. Our results suggest that the potential to meet the governments’ targets to increase C sequestration depend on the C debt incurred from the removed birch stands, the rotation length, and potentially also the susceptibility of the different stand types to future risk factors related to climate change.publishedVersio

Akkumulering av nitrogen- variasjoner avhengig av bestandsutvikling, nitrogentilførsel og simulert snødekke

Fra Institutt for jord- og vannfag. Rapport nr. 10/97 (60). Prosjektnummer NATI 17/96. Miljøverndepartementet fagrapport nr. 90. Oppdragsgiver: Direktoratet for Naturforvaltning.Kunnskap om hvor mye N som kan akkumuleres i jordsmonnet er av stor betydning for beregning av tålegrenser for N i skogøkosystemet. Formålet med denne undersøkelsen var å fremskaffe bedre estimater for netto N-immobiliseringshastighet i skogsjord og spesielt hvordan den påvirkes av bestandsalder, N-tilførsel og isolerende snødekke

Soil depth matters: shift in composition and inter-kingdom co-occurrence patterns of microorganisms in forest soils

Soil depth represents a strong physiochemical gradient that greatly affects soil-dwelling microorganisms. Fungal communities are typically structured by soil depth, but how other microorganisms are structured is less known. Here, we tested whether depth-dependent variation in soil chemistry affects the distribution and co-occurrence patterns of soil microbial communities. This was investigated by DNA metabarcoding in conjunction with network analyses of bacteria, fungi, as well as other micro-eukaryotes, sampled in four different soil depths in Norwegian birch forests. Strong compositional turnover in microbial assemblages with soil depth was detected for all organismal groups. Significantly greater microbial diversity and fungal biomass appeared in the nutrient-rich organic layer, with sharp decrease towards the less nutrient-rich mineral zones. The proportions of copiotrophic bacteria, Arthropoda and Apicomplexa were markedly higher in the organic layer, while patterns were opposite for oligotrophic bacteria, Cercozoa, Ascomycota and ectomycorrhizal fungi. Network analyses indicated more intensive inter-kingdom co-occurrence patterns in the upper mineral layer (0–5 cm) compared to the above organic and the lower mineral soil, signifying substantial influence of soil depth on biotic interactions. This study supports the view that different microbial groups are adapted to different forest soil strata, with varying level of interactions along the depth gradient.publishedVersio

Boreal tree species change as a climate mitigation strategy: impact on ecosystem C and N stocks and soil nutrient levels

To increase the annual uptake of CO2 as well as the long-term storage of carbon (C) in forests, the Norwegian government consider large-scale replacements of native, deciduous forests with faster-growing species like Norway spruce. To assess the effects of tree species change on ecosystem C and nitrogen (N) stocks and soil chemistry, we used a paired plot approach including stands of native downy birch and planted 45 – 60-year-old Norway spruce. The birch stands were used as reference for the assessment of differences following the tree species change. We found significantly higher C and N stocks in living tree biomass in the spruce stands, whereas no significant differences were found for dead wood. The cover of understory species groups, and the C and N stocks of the aboveground understory vegetation was significantly higher in the birch stands. The tree species change did not affect the soil organic carbon (SOC) stock down to 1 m soil depth; however, the significantly higher stock in the forest floor of the spruce stands suggested a re-distribution of SOC within the profile. There was a significant positive correlation between the SOC stock down to 30 cm soil depth and the total ecosystem C stock for the birch stands, and a negative correlation for the spruce stands. Significant effects of tree species change were found for C and N concentrations, C/N, exchangeable acidity, base saturation, and exchangeable Ca, K, Mg, Na, S, and Fe in the organic horizon or the upper mineral soil layer. The total ecosystem C stock ranged between 197 and 277 Mg ha-1 for the birch stands, and 297 and 387 Mg ha-1 for the spruce stands. The ecosystem C accumulation varied between 32 and 142 Mg ha-1 over the past 45-60 years, whereas the net ecosystem C capture was considerably lower and potentially negative. Our results suggest that the potential to meet the governments’ targets to increase C sequestration depend on the C debt incurred from the removed birch stands, the rotation length, and potentially also the susceptibility of the different stand types to future risk factors related to climate change

Shift in tree species changes the belowground biota of boreal forests

The replacement of native birch with Norway spruce has been initiated in Norway to increase long-term carbon storage in forests. However, there is limited knowledge on the impacts that aboveground changes will have on the belowground microbiota. We examined which effects a tree species shift from birch to spruce stands has on belowground microbial communities, soil fungal biomass and relationships with vegetation biomass and soil organic carbon (SOC). Replacement of birch with spruce negatively influenced soil bacterial and fungal richness and strongly altered microbial community composition in the forest floor layer, most strikingly for fungi. Tree species-mediated variation in soil properties was a major factor explaining variation in bacterial communities. For fungi, both soil chemistry and understorey vegetation were important community structuring factors, particularly for ectomycorrhizal fungi. The relative abundance of ectomycorrhizal fungi and the ectomycorrhizal : saprotrophic fungal ratio were higher in spruce compared to birch stands, particularly in the deeper mineral soil layers, and vice versa for saprotrophs. The positive relationship between ergosterol (fungal biomass) and SOC stock in the forest floor layer suggests higher carbon sequestration potential in spruce forest soil, alternatively, that the larger carbon stock leads to an increase in soil fungal biomass