Life in soil by the actinorhizal root nodule endophyte Frankia

Frankia is a genus of soil actinomycetes famous for its ability to form N2-fixing root nodule symbioses with actinorhizal plants. Although Frankia strains diplay a high diversity in terms of ecological niches in soil, current knowledge about Frankia is dominated by its life as an endophyte in root nodules. Increased use of molecular methods has refined and expanded insights into endophyte-host specificities and Frankia phylogeny. This review has focus on Frankia as a soil organism, including its part of microbial consortia, and how to study Frankia in soil. We highlight the use of nodulation tests and molecular methods to reveal population size and genetic diversity of Frankia in soil and discuss how autoregulation of nodulation and interactions with other soil microorganisms may influence the results. A comprehensive record of published interactions between Frankia and other soil microbes is summarized

Rätt mängd stallgödsel optimerar odling av baljväxtgrönfoder i norra Sverige

Gödslingsförsök med ärt/havre som samodlas till grönfoder utfördes under två säsonger på Röbäcksdalen i Umeå. År 2015 grodde havren dåligt och ärterna utgjorde 90 % av grödan. Då påverkades varken skörd eller proteinhalt av gödsling med ammoniumnitrat eller nötflytgödsel. År 2016 var mindre gynnsamt för ärten och ärterna utgjorde bara 25 % av grödan. Detta kan bero både på lågt pH i jorden och bättre uppkomst av havren 2016. Skördenivån eller proteinhalten påverkades inte av gödslingen med nötflytgödsel något av åren. År 2016 när havre dominerade blev skördenivån och proteinhalten i havren högre efter gödsling med 45-65 kg N som ammoniumnitrat än utan kvävegödsling. Kvävefixeringen per ha påverkades varken av gödsling med ammoniumnitrat eller nötflytgödsel, däremot var kvävefixeringen mycket högre 2015 (116 kg/ha) än 2016 (29 kg/ha). Proteinhalten, och stärkelsehalten var också mycket högre 2015 än 2016 tack vare den högre ärthalten. Grönfodret användes också i en inkubationsstudie tillsammans med vallfoder och kraftfoder. I en blandning av 30 % vallfoder, 30 % ärt/ havre från 2015 och 40 % korn uppmättes högre mängd användbart råprotein i tunntarmen än när vallfoder eller ärt/havrefoder från 2015 blandades med bara korn. Denna positiva interaktion mellan vallfoder och ärt/havre uppnåddes inte 2016 när havren dominerade. Ammonium- och nitrathalterna i jorden ned till 90 cm djup strax efter skörd och i slutet av oktober var inte förhöjda efter gödsling med 65 kg ammoniumnitrat eller 40 ton flytgödsel per ha jämfört med ogödslade kontroller. Vi drar slutsatserna att grödan varken behöver gödslas med mineralkväve eller stallgödselkväve, men att gödsling med stallgödsel inte heller ger större risk för utlakning av kväve.Gödslingsförsök med ärt/havre som samodlas till grönfoder utfördes under två säsonger på Röbäcksdalen i Umeå. År 2015 grodde havren dåligt och ärterna utgjorde 90 % av grödan. Då påverkades varken skörd eller proteinhalt av gödsling med ammoniumnitrat eller nötflytgödsel. År 2016 var mindre gynnsamt för ärten och ärterna utgjorde bara 25 % av grödan. Detta kan bero både på lågt pH i jorden och bättre uppkomst av havren 2016. Skördenivån eller proteinhalten påverkades inte av gödslingen med nötflytgödsel något av åren. År 2016 när havre dominerade blev skördenivån och proteinhalten i havren högre efter gödsling med 45-65 kg N som ammoniumnitrat än utan kvävegödsling. Kvävefixeringen per ha påverkades varken av gödsling med ammoniumnitrat eller nötflytgödsel, däremot var kvävefixeringen mycket högre 2015 (116 kg/ha) än 2016 (29 kg/ha). Proteinhalten, och stärkelsehalten var också mycket högre 2015 än 2016 tack vare den högre ärthalten. Grönfodret användes också i en inkubationsstudie tillsammans med vallfoder och kraftfoder. I en blandning av 30 % vallfoder, 30 % ärt/ havre från 2015 och 40 % korn uppmättes högre mängd användbart råprotein i tunntarmen än när vallfoder eller ärt/havrefoder från 2015 blandades med bara korn. Denna positiva interaktion mellan vallfoder och ärt/havre uppnåddes inte 2016 när havren dominerade. Ammonium- och nitrathalterna i jorden ned till 90 cm djup strax efter skörd och i slutet av oktober var inte förhöjda efter gödsling med 65 kg ammoniumnitrat eller 40 ton flytgödsel per ha jämfört med ogödslade kontroller. Vi drar slutsatserna att grödan varken behöver gödslas med mineralkväve eller stallgödselkväve, men att gödsling med stallgödsel inte heller ger större risk för utlakning av kväve

Ecological consequences of the expansion of N2-fixing plants in cold biomes

Research in warm-climate biomes has shown that invasion by symbiotic dinitrogen (N2)-fixing plants can transform ecosystems in ways analogous to the transformations observed as a consequence of anthropogenic, atmospheric nitrogen (N) deposition: declines in biodiversity, soil acidification, and alterations to carbon and nutrient cycling, including increased N losses through nitrate leaching and emissions of the powerful greenhouse gas nitrous oxide (N2O). Here, we used literature review and case study approaches to assess the evidence for similar transformations in cold-climate ecosystems of the boreal, subarctic and upper montane-temperate life zones. Our assessment focuses on the plant genera Lupinus and Alnus, which have become invasive largely as a consequence of deliberate introductions and/or reduced land management. These cold biomes are commonly located in remote areas with low anthropogenic N inputs, and the environmental impacts of N2-fixer invasion appear to be as severe as those from anthropogenic N deposition in highly N polluted areas. Hence, inputs of N from N2 fixation can affect ecosystems as dramatically or even more strongly than N inputs from atmospheric deposition, and biomes in cold climates represent no exception with regard to the risk of being invaded by N2-fixing species. In particular, the cold biomes studied here show both a strong potential to be transformed by N2-fixing plants and a rapid subsequent saturation in the ecosystem's capacity to retain N. Therefore, analogous to increases in N deposition, N2-fixing plant invasions must be deemed significant threats to biodiversity and to environmental quality

Nitrogen fixation in the lichen Stereocaulon paschale

The thesis is a summary and discussion of six papers. The purpose of the investigation was to study the influence of (i) environmental factors and (ii) the physiological condition of the thallus on nitrogen fixation in the lichen Stereocaulon paschale (L.) Fr. The nitrogen input to the site, a sparsely stocked pine forest in northern Sweden, was also studied. Nitrogen fixation (nitrogenase activity) was measured as acetylene reduction both in the field and in the laboratory. Usually intact lichen thalli were used, but also excised cephalodia were studied. All nitrogenase activity was located in the external cephalodia containing the blue-green alga Stigonema sp. There was always a reduction in nitrogenase activity when the cephalodia were quantitatively excised from the thallus. Moisture was found to be the most important environmental factor in the field during the snow free part of the year. At the site, with 14 % of the ground covered by S. paschale3 the yearly nitrogen fixation was estimated to c. 0.1 g nitrogen per m^. The lichen thalli could withstand several months in a very dry condition and at a low temperature without significant decrease in nitrogenase activity. A higher capacity for nitrogenase activity was found in lichen thalli collected from bare ground than in thalli collected under the snow. The light conditions before as well as during the nitrogenase activity measurements affected the nitrogenase activity. Thalli incubated with acetylene in the dark had only c. two thirds of their activities in the light. Lichen thalli pretreated in the light showed increased nitrogenase activities, probably due to raised content of carbohydrates available for nitrogenase activity. The necessary energy for nitrogenase activity is supplied by either oxidative phosphorylation or photophosphorylation. digitalisering@um

Growth of nitrogen-fixing Alnus incana and Lupinus spp. for restoration of degenerated forest soil in northern Sweden

In the interior of northern Sweden, more than 100.000 ha of previously productive forest land have degenerated soils. The presently thin humus layer and the resulting lack of mineralizable nitrogen and organic material results from strongly reduced litter production on the now almost tree-less areas. Intense forest fires in the past. as well as unfavourable forestry practices, are likely to have caused this situation. Cultivation of nitrogen-fixing plants, the native grey alder, Alnus incana ( L.) Moench. and introduced lupins. especially Lupinus nootkatensis Donn, was tried in the present study as a means of soil restoration. After 7 to 9 years. mesic sites with a temperature sum of 9800 daydegrees during the growing season gave higher survival and better growth of A. incana than did drier or cooler sites. At the northernmost, coolest site, L. nootkatensis performed very well while A. incana did not. Liming and, to some extent. soil scarification improved establishment of L. nootkatensis. Various amounts of alder leaves were repeatedly deposited every year to the soil in small experimental plots and the effects on soil properties were evaluated after 6 years. Nearly 1000 kg dry mass leaf litter per hectare was considered to be a realistic yearly production from dense A. incana stands. Such amounts gave a thicker humus layer with a comparably higher pH, a higher degree of base saturation. and a higher content of N,,,, and mineralizable N. Aspects of the biology and the handling of A, incana and L. nootkatensis are discussed. to serve as a guide in a choice between the two species for soil restoration purposes

Effects of Phosphorus and Nitrogen on Nodulation are Seen Already at the Stage of Early Cortical Cell Divisions in Alnus incana

• Background and Aims The present work aimed to study early stages of nodulation in a chronological sequence and to study phosphorus and nitrogen effects on early stages of nodulation in Alnus incana infected by Frankia. A method was developed to quantify early nodulation stages in intact root systems in the root hair-infected actinorhizal plant A. incana. Plant tissue responses were followed every 2 d until 14 d after inoculation. Cortical cell divisions were already seen 2 d after inoculation with Frankia. Cortical cell division areas, prenodules, nodule primordia and emerging nodules were quantified as host responses to infection