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.
2016
Abstract
No abstract has been registered
Authors
Belachew Gizachew Zeleke Svein Solberg Erik Næsset Terje Gobakken Ole Martin Bollandsås Johannes Breidenbach Eliakimu Zahabu Ernest William MauyaAbstract
Background: A functional forest carbon measuring, reporting and verification (MRV) system to support climate change mitigation policies, such as REDD+, requires estimates of forest biomass carbon, as an input to estimate emissions. A combination of field inventory and remote sensing is expected to provide those data. By linking Landsat 8 and forest inventory data, we (1) developed linear mixed effects models for total living biomass (TLB) estimation as a function of spectral variables, (2) developed a 30 m resolution map of the total living carbon (TLC), and (3) estimated the total TLB stock of the study area. Inventory data consisted of tree measurements from 500 plots in 63 clusters in a 15,700 km2 study area, in miombo woodlands of Tanzania. The Landsat 8 data comprised two climate data record images covering the inventory area. Results: We found a linear relationship between TLB and Landsat 8 derived spectral variables, and there was no clear evidence of spectral data saturation at higher biomass values. The root-mean-square error of the values predicted by the linear model linking the TLB and the normalized difference vegetation index (NDVI) is equal to 44 t/ha (49 % of the mean value). The estimated TLB for the study area was 140 Mt, with a mean TLB density of 81 t/ha, and a 95 % confidence interval of 74–88 t/ha. We mapped the distribution of TLC of the study area using the TLB model, where TLC was estimated at 47 % of TLB. Conclusion: The low biomass in the miombo woodlands, and the absence of a spectral data saturation problem suggested that Landsat 8 derived NDVI is suitable auxiliary information for carbon monitoring in the context of REDD+, for low-biomass, open-canopy woodlands.
Authors
Sabine Rosner Jan Světlík Kjell Andreassen Isabella Børja Lise Dalsgaard Robert Evans Saskia Luss Ole Einar Tveito Svein SolbergAbstract
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 based on anatomical data assessed by SilviScan technology and (ii) testing these proxies for their plasticity regarding climate, in order to (iii) analyze annual variations of hydraulic proxies of healthy looking trees and trees with top dieback upon their impact on tree survival. At two sites we selected 10 tree pairs, i.e., one healthy looking tree and one tree with visual signs of dieback such as dry tops, needle shortening and needle yellowing (n = 40 trees). Vulnerability to cavitation (P50) of the main trunk was assessed in a selected sample set (n = 19) and we thereafter applied SilviScan technology to measure cell dimensions (lumen (b) and cell wall thickness (t)) in these specimen and in all 40 trees in tree rings formed between 1990 and 2010. In a first analysis step, we searched for anatomical proxies for P50. The set of potential proxies included hydraulic lumen diameters and wall reinforcement parameters based on mean, radial, and tangential tracheid diameters. The conduit wall reinforcement based on tangential hydraulic lumen diameters ((t/bht)2) was the best estimate for P50. It was thus possible to relate climatic extremes to the potential vulnerability of single annual rings. Trees with top dieback had significantly lower (t/bht)2 and wider tangential (hydraulic) lumen diameters some years before a period of water deficit (2005–2006). Radial (hydraulic) lumen diameters showed however no significant differences between both tree groups. (t/bht)2 was influenced by annual climate variability; strongest correlations were found with precipitation in September of the previous growing season: high precipitation in previous September resulted in more vulnerable annual rings in the next season. The results are discussed with respect to an “opportunistic behavior” and genetic predisposition to drought sensitivity.
2015
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Authors
John W. Hanna M.V. Warwell Helen Maffei M.L. Fairweather J.T. Blodget P.J. Zambino J. Worrall K.S. Burns J.J. Jacobs Aaron Smith S.M. Ashiglar J.E. Lundquist Mee-Sook Kim A.L. Ross-Davis C. Hoffman R. Mathiasen R. Hofstetter J.D. Shaw E.W.I. Pitman E.V. Nelson G.I. McDonald M.R. Cleary S. Brar B.A. Richardson N.B. KlopfensteinAbstract
No abstract has been registered
Authors
Aaron SmithAbstract
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Authors
Ryan BrightAbstract
No abstract has been registered