Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2025
Authors
Eirik Gottschalk BalloAbstract
One of the key challenges we face today is the changing climate and its environmental impacts, affecting all life on Earth. Examining historical human responses to climate crises provides insights into resilience and adaptability. Robust data is essential for studying past climate and environmental changes effectively. European climate records covering the past 2000 years reveal a prolonged cooling period, known as the Dark Ages Cooling Period (c. 300–800 CE), punctuated by a pronounced cooling in the mid-6th century. Studies show that these cold intervals are more complex and regionally varied than previously believed. In the 6th century in Norway, archaeological evidence points to crop failures, famine, farm abandonment and changes in social organization in some regions, while others experienced minimal impact during these cold periods. However, southeastern Norway lacks detailed high-resolution paleoclimate and paleoenvironmental reconstructions, limiting our ability to fully understand these events. This thesis aims to enhance understanding of climate, environmental, and societal dynamics in southeastern Norway over the past 2000 years, focusing on the Dark Ages Cold Period (c. 300–800 CE), through sediment analysis from Lake Sagtjernet and Lake Ljøgottjern in southeastern Norway. We introduce a μCT scan method for varve counting for Lake Sagtjernet, establishing the first varve chronology from a Norwegian lake, covering c. 4023 years. This chronology enables the first paleoclimate and paleoenvironmental reconstruction from Norwegian varved lake sediments. This reconstruction reveals 2000 years of temperature variability, highlighting a major cooling event—the largest in 2000 years—that aligns with the 6th century cooling event. However, sparse settlements in the first millennium complicate climate impact interpretation at Lake Sagtjernet, while the last millennium shows increased human activities during both warm and cold periods. Reconstructed temperatures between 200 and 1300 CE from Lake Ljøgottjern indicate a notably colder period from 300 to 800 CE, compared to the periods before (200–300 CE) and after (800–1300 CE), identified as the Dark Ages Cold Period. Temperature fluctuations within this cold period significantly influenced agricultural strategies at the more populated Lake Ljøgottjern. Warmer intervals favoring crop cultivation and colder intervals prompting a shift towards livestock farming, illustrating the impact of climatic conditions on societal development.
Authors
Karin Juul Hesselsøe Anne Friederike Borchert Trond Olav Pettersen Kristoffer Herland Hellton Trygve S. AamlidAbstract
Ice encasement (IE) is one of the big challenges in winter stress management on golf course putting greens in Northern Scandinavia. The turfgrass is damaged due to lack of oxygen (hypoxia or anoxia) and accumulation of toxic by‐products of anaerobic respiration. Breeding IE‐tolerant turfgrass species and varieties is the best defense against these challenges. A method to simulate ice encasement was tested to screen selected varieties of winter‐hardy bentgrass species and red fescue subspecies. Note that 32 varieties were chosen from the SCANGREEN trial seeded at NIBIO Landvik, Norway, in 2019. Samples were taken in December 2020, 2021, and 2022, vacuum sealed in plastic, and stored in darkness at 0.5°C for up to 77 days to test them for their tolerance to simulated ice encasement (SIE). Samples were incubated at different intervals; plants were potted, and tiller survival was tested after 4 weeks of regrowth. Lethal duration of ice encasement (LD 50 ) that is, the number of days under anoxia that kills 50% of the plant population for each species and variety was calculated. The results showed that the ranking of cool season turfgrass species for tolerance to SIE was velvet bentgrass > Chewings fescue > slender creeping red fescue = colonial bentgrass > creeping bentgrass. This ranking does not fully reflect the ranking found in field tests where velvet bentgrass was superior together with creeping bentgrass. SIE caused a more rapid development of anoxia than IE in the field, and we hypothesize that creeping bentgrass is less tolerant to these conditions compared to the other species tested. To make the SIE method more representative for IE in field, it should be further adapted with incubation at lower temperatures, and with acclimation conditions to be standardized prior to sampling. Within species, the best tolerance to IE was found in velvet bentgrass Nordlys, creeping bentgrass Penncross, Chewings fescue Lykke, and slender creeping red fescue Cezanne.
Abstract
The primary benefits of turfgrass sod include rapid greenery and soil coverage, but its production causes concerns about soil losses at production sites. Soil adheres to the grass root system during harvesting and is removed from the sod farm, which in the long run might lead to soil degradation on the sod farm. In this study, we investigated sod thickness and the removal of organic and mineral matter when harvesting 24 fields representing 12 Norwegian sod farms in 2022 and 2023. On each field, 10 sod strips were randomly chosen, and five sod plugs were collected from each strip. Sod thickness was measured using a sliding gauge. Sod mineral matter (SMM: soil and thatch mineral matter) and sod organic matter (SOM: soil and thatch organic matter) contents were quantified by loss on ignition at 550°C. Management and field properties were also documented. Results showed an average amount of mineral matter in the sod strips of 36 Mg ha −1 for all fields but with significant variation among fields ( p < 0.001). The average SOM content was 10 Mg ha −1 . Mean sod thickness was 15.4 mm and had a strong correlation with SOM ( r = 0.8) but only a moderate correlation with SMM ( r = 0.6). Soil water content and surface hardness at harvest affected sod thickness and SMM only slightly. Sod harvesters with twin heads harvested significantly thicker sod strips and removed more mineral matter than harvesters with single cutting heads. Soil texture did not have a significant impact on sod thickness or mineral matter removal.
Authors
Siv Mari AurdalAbstract
This paper is a historical review of scientific progress on horticultural growing media, with particular attention to the role of peat and the recurring search for sustainable alternatives. It is well established that peat became the cornerstone of horticultural growing media because it offered a unique combination of nutrient control, pH buffering, water retention, absence of harmful microorganisms, and structural stability. Equally evident are the environmental concerns and sustainability goals that have driven the search for alternative materials since the 1980s. This historical review traces the evolution of growing media from the early 20th century to the mid-2020s, focusing on how peat came to dominate and why its substitution has proven so difficult. Drawing on a wide range of literature, including peer-reviewed experimental studies, historical sources, symposia proceedings, institutional reports, and synthesis articles, the historical development of growing media science and practice across each decade is outlined. Attention is given to various composts, coir, wood fiber, bark, and biochar and challenges with these materials related to product standardization for end-user reliability. While many alternatives show potential, particularly as partial components or as stand-alone media under certain conditions, no single material currently offers a fully viable replacement for peat. Instead, the most promising direction appears to be peat-reduced mixtures optimized for both functionality and sustainability. By understanding how growing media science has evolved and where it has struggled, this paper identifies lessons critical to navigating the ongoing transition toward more sustainable and functional systems.
Authors
Abel Gizaw Seid Dimitar Dimitrov Catherine Aloyce Masao Felly Mugizi Tusiime Tigist Woldimu Ahmed Abdikadir Abdi Desalegn Chala Galina Gusarova Virginia Mirré Mulugeta Kebede Rosalia Pineiro Mary Namaganda Pilar Catalan Manuel Pimentel Pereira Pierre Robert Michel Taberlet Hans Peter Linder Magnus Popp Gerald Eilu Pantaleo Munishi Geoffrey Mwachala Sileshi Nemomissa Christian BrochmannAbstract
Aim It has been proposed that species diversity (SD) and genetic diversity (GD) co-vary across natural communities because both are shaped by processes such as immigration and drift. However, empirical reports are contradictory, and multispecies studies are rare. Here we test the hypothesis that the two diversity measures do not correlate in systems with high levels of immigration stochasticity and little GD caused by strong genetic drift. Location Tropical alpine habitats on six of the highest mountains in eastern Africa. Taxon Vascular plants. Methods We sampled 375 taxa in 75 plots in five habitat types, recorded ecological variables, and genotyped 1793 plants representing 20 species/species complexes. Results We confirmed that intrapopulation GD was exceptionally low in this system and found that most Species-Genetic Diversity Correlations (SGDCs) were weak and insignificant. Whereas SD was correlated with several environmental variables, GD was only correlated with mountain identity (geographical location) and mountain age. Main Conclusions Our findings support the hypothesis that SGDCs are lacking in habitat island systems such as the tropical alpine region in Africa, which is characterised by frequent population size fluctuations, extinctions, and colonisations via long-distance dispersal (LDD) during the glacial cycles. The stochastic nature of LDD combined with strong genetic drift and founder effects is likely to cause low GD and lack of SGDCs, implying that SD cannot be used as a proxy for GD in conservation management of such systems.
Authors
Juan Manuel Gorospe Eliska Zaveska Desalegn Chala Abel Gizaw Seid Felly Mugizi Tusiime A Lovisa S Gustafsson Lubomir Pialek Filip Kolář Christian Brochmann Roswitha SchmicklAbstract
Mountains have highly heterogeneous environments that generate ample opportunities for lineage differentiation through ecological adaptation, geographic isolation and secondary contact. The geographic and ecological isolation of the afroalpine vegetation fragments on the East African mountain tops makes them an excellent system to study speciation. The initial diversification within the afroalpine endemic genus Dendrosenecio was shown to occur via allopatric divergence among four isolated mountain groups, but the potential role of ecological speciation within these groups and the role of gene flow in speciation remained uncertain. Here we extend the sampling of Dendrosenecio and use phylogenomics to assess the importance of gene flow in the diversification of the genus. Then, population genomics, demographic modelling and habitat differentiation analyses are used to study ecological speciation in two sister species occurring on Mount Kenya. We found that two sympatric sister species on Mt Kenya occupy distinct microhabitats, and our analyses support that they originated in situ via ecological speciation with gene flow. In addition, we obtained signals of admixture history between mountain groups. Taken together, these results suggest that geographic isolation shaped main lineages, while ecologically mediated speciation occurred within a single mountain.
Authors
Lucía D. Moreyra Cristina Roquet Alfonso Susanna Siri Birkeland Carme Blanco‐Gavaldà Christian Brochmann Desalegn Chala Mercè Galbany‐Casals Abel Gizaw Seid Juan Antonio CallejaAbstract
Aim We investigated the biogeographic history and diversification dynamics of Afrocarduus, an Afromontane–Afroalpine genus endemic to eastern Africa. We aimed to assess the roles of geographic isolation, habitat transitions, and ecological speciation in shaping current diversity. Location The Afromontane and Afroalpine regions of East Africa and Ethiopia are situated along the Great Rift Valley system. Taxon Afrocarduus (Compositae: Carduinae), a genus comprising 18 endemic species. Methods We conducted a comprehensive taxonomic and geographic sampling of Afrocarduus, generating data from 489 nuclear loci. Phylogenomic and biogeographic ancestral estimation analyses were performed to infer the evolutionary history and historical biogeography of the genus. Results Afrocarduus originated in the Afromontane zone of eastern Africa during the Late Miocene (~10.7 Ma), with major diversification events occurring in the Early Pleistocene (~2.3 Ma). Most dispersal events occurred between neighbouring massifs, though occasional long-distance dispersal between disjunct mountain systems was detected. The Turkana Depression and the Great Rift Valley have acted as major biogeographic barriers. Phylogenetic structure shows distinct clades occupying different regions. Ecological divergence between Afromontane and Afroalpine environments contributed to speciation, with at least six independent adaptations to Afroalpine conditions and multiple cases of ecological reversal. Stem loss, a trait associated with alpine habitats, evolved convergently in two clades. Closely related species often segregate by elevation or microhabitat within the same massif. Main Conclusions The diversification of Afrocarduus has been shaped by a combination of historical climate change, geographic isolation, and ecological adaptation. Our results emphasise the importance of ecological speciation and habitat transitions in Afrotemperate plant evolution and highlight the need for further research on understudied Afromontane taxa, especially under the threat of ongoing climate change.
Authors
Lucía D. Moreyra Juan Antonio Calleja Cristina Roquet Siri Birkeland Carme Blanco‐Gavaldà Mercè Galbany‐Casals Abel Gizaw Seid Frederik Leliaert Christian Brochmann Alfonso SusannaAbstract
Accurate species delimitation is crucial for biodiversity research, as it significantly impacts taxonomy, ecology, and conservation. Recent advances in molecular phylogenetics and integrative taxonomy have improved classifications and resolved long‐standing taxonomic uncertainties. Here, we use Hyb‐Seq (489 nuclear loci) and phylogenomic approaches to investigate Afrocarduus , a genus endemic to tropical Afromontane and Afroalpine regions. Our analyses reveal 16 evolutionary lineages within this relatively young genus (crown age 2.3 Mya), with new morphological data strongly supporting the recognition of each lineage as a distinct species. We demonstrate that the stemless habit evolved independently in species from the Ethiopian Highlands and the East African Rift System (EARS). Notably, we show that the concept of the stemless Afrocarduus schimperi adopted by the Flora of Tropical East Africa, in fact, comprises seven clearly recognizable species, which we formally reinstate. Unexpectedly, the stemmed Afrocarduus nyassanus was recovered as paraphyletic with Afrocarduus ruwenzoriensis nested within it, probably due to incomplete lineage sorting or hybridization. Additionally, the stemmed Afrocarduus keniensis may represent a complex of cryptic species, and we describe a new stemmed species from southern Ethiopia, Afrocarduus kazmi sp. nov. We expand the number of accepted species in Afrocarduus from eight, as recognized in the Flora of Tropical East Africa, to 18 (including two species for which we were not able to obtain molecular data). Our study thus highlights a substantial prior underestimation of the diversity of Afrocarduus in Afromontane and Afroalpine habitats.
Abstract
This study evaluates the effectiveness of various peat-free and peat-reduced growing media on the growth and yield of tomatoes and carrots, with the aim to develop sustainable alternatives to traditional peat-based substrates in horticulture. Thirty different growing media mixtures were tested, incorporating materials such as wood fiber, compost, biochar, bio-ash, and struvite, with the goal of identifying viable alternatives to peat. The experiments were conducted in greenhouse conditions, and the performance of these mixtures was assessed based on yield and overall vitality of tomato and carrot plants. The results revealed that fully peat-free mixtures generally underperformed compared to peat-based references. However, some peat-reduced mixtures with 30% peat in combination with wood fiber, compost, struvite or bio-ash demonstrated promising results. Bio-ash and struvite were evaluated as phosphorus sources, with findings suggesting that both materials can enhance substrate fertility when combined with appropriate nitrogen fertilizers. The effect of biochar was not very pronounced in general. Moreover, the addition of biochar was associated with a disappearance of plant-available nitrogen from the growing media, which likely contributed to its limited effectiveness in improving crop performance. The study underscores the continual challenge of completely phasing out peat in growing media for horticulture but highlights the potential of reducing it greatly and integrating more sustainable materials such as wood fiber and recycled materials such as compost, bio-ash and struvite. The results suggest that with further refinement, specific combinations of these materials could be developed into optimized substrate mixtures for sustainable horticultural practices without compromising productivity.
Abstract
Jordens fysiske egenskaper ble studert på to golfbaner der enten små, lette robotklippere eller store, tunge tradisjonelle gressklippere hadde vært brukt i fire til fem år. På begge banene var jorda mindre komprimert der det var brukt robotklippere sammenlignet med der de store maskinene var brukt, men fordi innledende målinger manglet, kan det ikke konkluderes definitivt om forskjellene skyldtes bruk av robotklippere eller tradisjonelle gressklippere.