Isabella Børja

Isabella Børja
Norwegian Institute of Bioeconomy Research, Ås, Norway · Biotechnolgy and Plant Health

PhD

About

82
Publications
21,616
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2,047
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Additional affiliations
January 1986 - present
Norwegian Institute of Bioeconomy Research
Position
  • Professor

Publications

Publications (82)
Article
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Drought-induced mortality is a major direct effect of climate change on tree health, but drought may also affect trees indirectly by altering their susceptibility to pathogens. Here we report how a combination of mild or severe drought and pathogen infection affected growth, pathogen resistance, and gene expression in potted 5-year-old Norway spruc...
Article
Full-text available
Introduction The ascomycete Hymenoscyphus fraxineus, originating from Asia, is currently threatening common ash (Fraxinus excelsior) in Europe, massive ascospore production from the saprotrophic phase being a key determinant of its invasiveness. Methods To consider whether fungal diversity and succession in decomposing leaf litter are affected by...
Article
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The populations of European ash and its harmless fungal associate Hymenoscyphus albidus are in decline owing to ash dieback caused by the invasive Hymenoscyphus fraxineus , a fungus that in its native range in Asia is a harmless leaf endophyte of local ash species. To clarify the behavior of H. albidus and its spatial and temporal niche overlap wit...
Article
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European ash (Fraxinus excelsior) is threatened by the invasive ascomycete Hymenoscyphus fraxineus originating from Asia. Ash leaf tissues serve as a route for shoot infection but also as a sporulation substrate for this pathogen. Knowledge of the leaf niche partitioning by indigenous fungi and H. fraxineus is needed to understand the fungal commun...
Article
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Biodiversity of ecosystems is an important driver for the supply of ecosystem services to people. Soils often have a larger biodiversity per unit surface area than what can be observed aboveground. Here, we present what is to our knowledge the most extensive literature-based key-word assessment of the existing information about the relationships be...
Article
Soil is one of the most species-rich habitats and plays a crucial role in the functioning of terrestrial ecosystems. It is acknowledged that soils and their biota deliver many ecosystem services. However, up to now, cultural ecosystem services (CES) provided by soil biodiversity remained virtually unknown. Here we present a multilingual and multisu...
Article
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Several studies have looked at how individual environmental factors influence needle morphology in conifer trees, but interacting effects between drought and canopy position have received little attention. In this study, we characterized morphological responses to experimentally induced drought stress in sun exposed and shaded current-year Norway s...
Article
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Dieback of European ash, caused by the ascomycete Hymenoscyphus fraxineus originating from Asia, has rapidly spread across Europe, and is threatening this keystone tree at a continental scale. High propagule pressure is characteristic to invasive species. Consistently, the enormous production of windborne ascospores by H. fraxineus in an ash forest...
Chapter
European ash (Fraxinus excelsior), a keystone species with wide distribution and habitat range in Europe, is threatened at a continental scale by an invasive alien ascomycete, Hymenoscyphus fraxineus. In its native range of Asia, this fungus is a leaf endophyte with weak parasitic capacity and robust saprobic competence in local ash species that ar...
Article
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The ongoing climate change may have a distinct effect on Norway spruce growth, one of the most important tree species in European forest management. Therefore, the understanding and assessment of climate-growth relationship can help to reveal relevant patterns in temporal variability that may result in lower tree vitality and decline. The main obje...
Data
Fig. S1 Monthly precipitation and mean temperature in 2011 and 2012. Fig. S2 Damage assessment of sampled ash trees in early (22 June) and late (23 August) summer 2012. Fig. S3 Hymenoscyphus fraxineus DNA amount in tissues collected from healthy and diseased ash trees throughout the summer 2012 and analyzed by a qPCR assay specific to the DNA of...
Article
Full-text available
Ash dieback, caused by the ascomycete Hymenoscyphus fraxineus, has been spreading throughout Europe since the early 1990s, threatening European ash at a continental scale. Little is known about the development of the disease in individual forest trees and in different age classes. In this study we monitored ash dieback on trees of different diamete...
Article
Full-text available
High biodiversity is regarded as a barrier against biological invasions. We hypothesized that the invasion success of the pathogenic ascomycete Hymenoscyphus fraxineus threatening common ash in Europe relates to differences in dispersal and colonization success between the invader and the diverse native competitors. Ash leaf mycobiome was monitored...
Research
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Meeting of the Austrian Society of Plant Biology (ATSPB), Berchtesgaden, Germany, May 26-28. In: Proceedings of the 21. Tagung der Austrian Society of Plant Biology (ATSPB), p. 72.
Article
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Top dieback in 40–60 years old forest stands of Norway spruce [Picea abies (L.) Karst.] in southern Norway is supposed to be associated with climatic extremes. Our intention was to learn more about the processes related to top dieback and in particular about the plasticity of possible predisposing factors. We aimed at (i) developing proxies for P50...
Data
Mean monthly temperature (A), precipitation (B) and daily water deficit during the vegetation period (May–September) of years 1989–2010. Bars represent mean values for Sande and Hoxmark.
Data
Information on the origin of the wood beam sample set for calculation of P50 and anatomical proxies from the SilviScan data set (n = 19) of 12 trees, where six trees were healthy looking and six trees showed signs of top dieback.
Data
Mean monthly precipitation and daily water deficit from 1957 to 2015 of Sande and Hoxmark sites (gray areas or bars). Red lines indicate the year 1992, where early summer was extremely dry, blue lines indicate the extremely wet year 2007.
Article
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p style="text-align: justify;">There is evidence that recently occurring top dieback of Norway spruce ( Piceaabies (L.) Karst.) treesin southern Norway is associated with drought stress. We comparedfunctional wood traits of20 healthy looking trees and 20 trees with visual signs of top dieback. SilviScan technology was applied to measure cell dimens...
Technical Report
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Our recommendation for SE Norway include: species composition changes, optimization of regeneration, integrated forest protection and changing of tending, thinning and harvesting, especially in Norway spruce stands.
Article
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Top dieback of Norway spruce (Picea abies), triggered by drought in 2004–2006, has been observed in Southeast Norway and trees died within four years after appearance of the first symptoms. The aim of our study was to use sap flux measurements as a diagnostic method for assessment of tree vitality. We used the heat field deformation method to monit...
Article
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Predicted increases in the frequency and duration of drought are expected to negatively affect tree vitality, but we know little about how water shortage will influence needle anatomy and thereby the trees’ photosynthetic and hydraulic capacity. In this study, we evaluated anatomical changes in sun and shade needles of 20-year-old Norway spruce tre...
Article
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The demand for bioenergy caused an increased use of logging residues, branches and treetops that were previously left on the ground after harvesting. Residues are stored outdoors in piles and it is unclear to what extent fungi transform this material. Our objective was to quantify the amount of wood degrading fungi during storage using quantitative...
Article
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Pythium species are fungal-like organisms distributed all over the world. Most Pythium spp. live as saprophytes, but some of them are pathogenic. Here we report on disease incidence in Norway spruce (Picea abies) seedlings caused by Pythium undulatum, and pathogenicity in vitro of Norwegian isolates of P. undulatum and P. anandrum.
Conference Paper
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In 2012, conspicuous dark, bleeding cankers were observed on trunks of dying trees in natural stands of grey alder (Alnus incana) along the shore of lake Årungen in Akershus county in Norway. Phytophthora alni, which has been killing alder in Europe during the past two decades, was suspected to cause the disease. Work was initiated to identify the...
Article
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We linked hydraulic vulnerability in Norway spruce (Picea abies (L.) Karst.) trunkwood with different cambial age to wood density and applied the findings on annual density variations in healthy and declining trees from southern Norway during 1990 to 2010. We hypothesized that drought stress due to the 2003 or 2006 European heat waves were the trig...
Article
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Trees must respond to many environmental factors during their development, and light is one of the main stimuli regulating tree growth. Thinning of forest stands by selective tree removal is a common tool in forest management that increases light intensity. However, morphological and anatomical adaptations of individual shoots to the new environmen...
Article
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Estimates of root absorption magnitude are needed for the balanced management of forest ecosystems, but no methods able to work on the whole tree and stand level were available. Modified earth impedance method was developed recently and here it was tested, by comparing the results with those obtained by combination of several classical methods. We...
Article
Shoot dieback disease of European ash caused by the ascomycete Hymenoscyphus pseudoalbidus threatens ash on a continental scale. A spore sampler placed in a diseased ash forest in Southern Norway, coupled with microscopy and DNA-based fungal species-specific real-time PCR assays, was employed to profile diurnal and within-season variation in infect...
Article
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Top-dieback of Norway spruce (Picea abies) trees has been observed in SE Norway. Trees usually die within 1-4 years after the first symptoms become visible and the dieback cause is unknown. The aim of our study was to establish when the irreversible spiral to tree death occurs. We assumed that hydraulic dysfunction, exemplified here by the sap flow...
Article
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In cases where sap flow is measured in trees and cross-sectional sapwood is not uniformly distributed, as in stems of diseased trees, an additional method may refine the sap flow measurements. If the studied trees are felled, the modified differential translucence method (MDT) for quantifying sapwood distribution in cross-sectional area may be comp...
Conference Paper
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Within the framework of the COST Action FP0803 'Belowground carbon turnover in European forests' several conferences, workshops and Training Schools were held during the period of 2009 and 2013. The first conference was held at our Institute, WSL, in Birmensdorf (Switzerland), as the first event of the COST Action following the kick-off meeting in...
Article
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All plant-bearing soils are interwoven with fungal hyphae. Their structure and function are affected by environmental factors like drought, which might be a stress factor of increasing importance in many world regions due to climate change. The fungal mycelium in soil is important both for mycorrhizal symbiosis with plant roots and for litter decom...
Article
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Background and Aims Forest trees directly contribute to carbon cycling in forest soils through the turnover of their fine roots. In this study we aimed to calculate root turnover rates of common European forest tree species and to compare them with most frequently published values. Methods We compiled available European data and applied various tur...
Research
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Tidlig på våren i 2012 ble det observert døde og døende traer av gråor i vannkanten langs Årungen i Ås kommune (Akershus). På stammene var det tjaerefargede flekker, et symptom som gjerne forbindes med angrep av plantepa-togene arter innen slekten Phytophthora. Fram til 1990-tallet var det ikke kjent at Phytophthora kunne angripe or, men i 1993 ble...
Technical Report
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Dette er en utredning som er gjort på oppdrag for Nasjonalt program for kartlegging og overvåkning av biologisk mangfold. Datagrunnlag er innhentet fra Statistisk sentralbyrå. Vi takker medarbeidere ved Statistisk sentralbyrå, Toll- og avgiftsdirektoratet, Direktoratet for naturforvaltning, Mattilsynet og alle øvrige som har bidratt med informasjon...
Article
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Conifer needles are extraordinarily variable and much of this diversity is linked to the water transport capacity of the xylem and to xylem conduit properties. However, we still know little about how anatomical characteristics influence the hydraulic efficiency of needle xylem in different parts of the crown. In this study we evaluated needle funct...
Article
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Purpose Drought-induced tree susceptibility is a major risk associated with climate change. Here we report how an 11-week drought affected tracheid structure, gene expression, and above- and belowground growth in 5-year-old Norway spruce trees (Picea abies) under controlled conditions. Results The canopy of trees subjected to severe drought had si...
Article
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Molecular methods are emerging also as useful tools for wood protection studies. The aim of the present study was to evaluate quantitative real-time polymerase chain reaction (qPCR) as a tool for investigating details of the colonization pattern of basidiomycete decay fungi in wood samples after 6 years of soil exposure. Samples of Pinus sylvestris...
Article
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Conifers and other trees are constantly adapting to changes in light conditions, water/nutrient supply and temperatures by physiological and morphological modifications of their foliage. However, the relationship between physiological processes and anatomical characteristics of foliage has been little explored in trees. In this study we evaluated n...
Article
Full-text available
Dieback of European ash (Fraxinus excelsior), caused by the ascomycete Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea), started around 1992 in Poland and has since then spread over large geographical areas. By November 2010, the disease had been recorded in 22 European countries. The gradual expansion and high intensity of the ash dieback e...
Article
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Conclusion The functionally critical role of mycorrhizal fungi in forest ecosystems, and the imminent threat of climate change that may act to alter mycorrhizal functional biodiversity, means there is an urgent need for a regional to continental-scale assessment of mycorrhizal distributions. Until recently, it had not been possible to cost-effectiv...
Article
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Minirhizotrons, transparent acrylic tubes inserted in the soil, are well suited for long term, non destructive, in situ observations of fine roots. In minirhizotrons, the fine roots are regularly photographed and the root images are visually evaluated according to their status as living, dead or disappeared. This evaluation gives the background for...
Article
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Increased removal of biomass from forested ecosystems for use as an alternative source of energy is an option in several countries. E.g., it is planned to double the use of bioenergy from all sources until 2020 in Norway. A large fraction of this increase is coming from forest resources, e.g. by removing harvest residues like branches and tops. Thi...
Article
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In this study, we surveyed the long term effects of liming and fertilizing in old Scots pine stands on the ectomycorrhiza (ECM) colonization, tree growth and needle nutrient concentration 35years later. Four mature stands of Scots pine on low productive mineral soil were limed in 1959 and 1964 with total doses of limestone ranging from 3 to 15Mg ha...
Article
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We assessed the influence of stand age on fine root biomass and morphology of trees and understory vegetation in 10-, 30-, 60- and 120-year-old Norway spruce stands growing in sandy soil in southeast Norway. Fine root (< 1, 1-2 and 2-5 mm in diameter) biomass of trees and understory vegetation (< 2 mm in diameter) was sampled by soil coring to a de...
Article
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Fine roots (<2 mm) are very dynamic and play a key role in forest ecosystem carbon and nutrient cycling and accumulation. We reviewed root biomass data of three main European tree species European beech, (Fagus sylvatica L.), Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.), in order to identify the differences between spe...
Article
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Human-induced and natural stress factors can affect fine roots and ectomycorrhizas. Therefore they have potential utility as indicators of environmental change. We evaluated, through meta-analysis, the magnitude of the effects of acidic deposition, nitrogen deposition, increased ozone levels, elevated atmospheric carbon dioxide, and drought on fine...
Article
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ABSTRACT In spring 2002, an unusual disease outburst was recorded on Norway spruce seedlings in southeast Norway. Extensive damage was recorded on 1- and 2-year-old Norway spruce seedlings that either had wintered in nursery cold storage or had been planted out in autumn 2001. The damage was characterized by leader shoot dieback and stem necroses o...