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.
2019
Authors
Rene Friedland Gerald Schernewski Ulf Gräwe Inga Greipsland Dalila Palazzo Marianna PastuszakAbstract
No abstract has been registered
Abstract
Knowledge about spatiotemporal variability of climate change effect on tree-ring width (TRW) and crown condition is essential to optimize the modelling of future forest ecosystem responses to the changing climate. Geographical differences in the climate–growth relationship are a reflection of the regional climatic conditions mainly. In this study, 175 Picea abies trees from the north-western edge of its geographical distribution in Central Norway were evaluated with respect to geographical and age-dependent differences during the common period of 1950–2015. The results showed that the most significant positive correlations between TRW and the current June temperature were unstable although the temperature increased. The correlations suddenly started to decrease (regardless of the site placement and tree age) at the beginning of the 1990s, but subsequently unexpectedly increased in the 2010s. The superposed epoch analysis revealed longer TRW regeneration of the southern plots (except over-mature trees) after negative pointer years compared to the northern plots. Previous summer temperature and related physiological processes (cone crops, storage of nutrients, etc.) significantly negatively affected P. abies growth in the current year. Additionally, our results showed that the selection of the chronology version (standard or residual) significantly affects the resulting correlations and thus must be carefully considered in dendroclimatological studies. Our main outputs can contribute to better understanding of the climate–growth relationship variability and general prediction of the radial growth.
Authors
Shahid Nadeem Håvard Steinshamn Elin Halvorsen Sikkeland Anne-Maj Gustavsson Anne Kjersti BakkenAbstract
No abstract has been registered
Authors
Mohamed Neji Anais Gorel Dario Isidro Ojeda Alayon Jerome Duminil Chedly Kastally Kathy Steppe Adeline Fayolle Olivier J. HardyAbstract
With the ongoing climate change, African rainforests are expected to experience severe drought events in the future. In Africa, the tropical genus Erythrophleum (Fabaceae) includes two forest sister timber tree species displaying contrasting geographical distributions. Erythrophleum ivorense is adapted to wet evergreen Guineo-Congolian forests, whereas E. suaveolens occurs in a wider range of climates, being found in moist dense forests but also in gallery forests under a relatively drier climate. This geographical distribution pattern suggests that the two species might cope differently to drought at the genomic level. Yet, the genetic basis of tolerance response to drought stress in both species is still uncharacterized. To bridge this gap, we performed an RNA-seq approach on seedlings from each species to monitor their transcriptional responses at different levels of drought stress (0, 2 and 6 weeks after stopping watering seedlings). Monitoring of wilting symptoms revealed that E. suaveolens displayed an earlier phenotypic response to drought stress than E. ivorense. At the transcriptomic level, results revealed 2020 (1204 down-regulated/816 up-regulated) and 1495 differentially expressed genes (DEGs) in response to drought stress from a total of 67,432 and 66,605 contigs assembled in E. ivorense and E. suaveolens, respectively. After identifying 30,374 orthologs between species, we found that only 7 of them were DEGs shared between species, while 587 and 458 were differentially expressed only in E. ivorense or E. suaveolens, respectively. GO and KEGG enrichment analysis revealed that the two species differ in terms of significantly regulated pathways as well as the number and expression profile of DEGs (Up/Down) associated with each pathway in the two stress stages. Our results suggested that the two studied species react differently to drought. E. suaveolens seems displaying a prompt response to drought at its early stage strengthened by the down-regulation of many DEGs encoding for signaling and metabolism-related pathways. A considerable up-regulation of these pathways was also found in E. ivorense at the late stage of drought, suggesting this species may be a late responder. Overall, our data may serve as basis for further understanding the genetic control of drought tolerance in tropical trees and favor the selection of crucial genes for genetically enhancing drought resistance.
Abstract
No abstract has been registered
Abstract
A novel method for age-independent site index estimation is demonstrated using repeated single-tree airborne laser scanning (ALS) data. A spruce-dominated study area of 114 km2 in southern Norway was covered by single-tree ALS twice, i.e. in 2008 and 2014. We identified top height trees wall-to-wall, and for each of them we derived based on the two heights and the 6-year period length. We reconstructed past, annual height growth in a field campaign on 31 sample trees, and this showed good correspondence with ALS based heights. We found a considerable increase in site index, i.e. about 5 m in the H40 system, from the old site index values. This increase corresponded to a productivity increase of 62%. This increase appeared to mainly represent a real temporal trend caused by changing growing conditions. In addition, the increase could partly result from underestimation in old site index values. The method has the advantages of not requiring tree-age data, of representing current growing conditions, and as well that it is a cost-effective method with wall-towall coverage. In slow-growing forests and short time periods, the method is least reliable due to possible systematic differences in canopy penetration between repeated ALS scans.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered