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Ducey M.J.,University of New Hampshire | Astrup R.,431 As
Canadian Journal of Remote Sensing | Year: 2013

Nondetection of trees is a serious problem for the use of terrestrial laser scanning (TLS) in forest inventory applications. The use of multiple coregistered scans can reduce nondetection but may not eliminate it, and it carries substantial field and post-processing costs. We examined and extended previously developed theoretical approaches to modeling nondetection. The results suggested that tree size as well as multiple stand structural characteristics may be factors, but the theoretical models do not lend themselves to empirical estimation. We then used distance sampling techniques to identify detection probabilities and develop adjusted estimates for trees per hectare and basal area in nine forest stands in southern Norway. The results compared favorably with field estimates based on fixed-area plots. The estimated detection probabilities indicate that correction for nondetection is needed unless the search for trees is limited to very small distances from the scanner. Distance sampling appears promising when TLS is used in the context of temporary-plot forest inventories. © 2013 Government of Canada. Source


Dalsgaard L.,Copenhagen University | Dalsgaard L.,431 As | Mikkelsen T.N.,Technical University of Denmark | Bastrup-Birk A.,Copenhagen University
Journal of Plant Ecology | Year: 2011

Aims Beech (Fagus sylvatica L.) is an important species in natural and managed forests in Europe. This drought-sensitive species dominates even-aged stands as well more natural stands composed of a mixture of tree species, age and size classes. This study evaluates the extent that heterogeneity in spacing and tree diameter affect the seasonal availability and use of water. Methods Two stands were evaluated: (i) a heterogeneous forest remnant (NAT) with trees up to ∼300 years old, a mean top height of 28.4 m and a total of 733 stems ha-1with stem diameters averaging 18 cm and (ii) an even-aged 80-year old stand (MAN), with a height of 25 m, and a total of 283 stems ha -1 with diameters averaging 38 cm. Stem sap flow, Js (g m -2 s-1), was continuously measured in 12 (MAN) and 13 (NAT) trees using 20-mm long heat dissipation sensors. Individual tree measures of sap flow were correlated using non-linear statistical methods with air vapour pressure deficit (D, hPa) and global radiation (Rg, J m-2 day -1), along with constraints imposed by reductions in soil water content (SWC). SWC was measured as volumetric % using time domain reflectometry. Important Findings The daily integrated Js (Js-sum) for trees growing in the evenly spaced MAN stand and trees in canopy and closed forest positions in NAT stand decreased as the availability of soil moisture was reduced. In the heterogeneous NAT stand, SWC in a recently formed canopy gap remained high throughout the vegetation period. Based on regression models, the predicted relative decrease in Js-sum for dry relative to moist soil water conditions in the closed forest (at mean daily D = 10 hPa) was 7-11% for trees near the gap and 39-42% for trees in the closed forest. In MAN, the reduction in Js-sum was 29% in dry relative to moist conditions. Js-sum in the outer 20 mm of the xylem in NAT was lower than that in MAN and the rate of decline in Js with xylem depth was less in NAT than in MAN. In MAN, Js-sum in deep and outer xylem was negatively affected at low soil moisture availability; in NAT, this was the case for only the outer xylem indicating that deep roots could be important in supplying water at times of low soil moisture in the upper soil. © The Author 2011. Published by Oxford University Press on behalf of the Institute of Botany, Chinese Academy of Sciences and the Botanical Society of China. Source


Liu H.,University of Aarhus | Sorensen A.C.,University of Aarhus | Meuwissen T.H.E.,Norwegian University of Life Sciences | Berg P.,University of Aarhus | Berg P.,431 As
Genetics Selection Evolution | Year: 2014

Background: Genomic selection makes it possible to reduce pedigree-based inbreeding over best linear unbiased prediction (BLUP) by increasing emphasis on own rather than family information. However, pedigree inbreeding might not accurately reflect loss of genetic variation and the true level of inbreeding due to changes in allele frequencies and hitch-hiking. This study aimed at understanding the impact of using long-term genomic selection on changes in allele frequencies, genetic variation and level of inbreeding. Methods. Selection was performed in simulated scenarios with a population of 400 animals for 25 consecutive generations. Six genetic models were considered with different heritabilities and numbers of QTL (quantitative trait loci) affecting the trait. Four selection criteria were used, including selection on own phenotype and on estimated breeding values (EBV) derived using phenotype-BLUP, genomic BLUP and Bayesian Lasso. Changes in allele frequencies at QTL, markers and linked neutral loci were investigated for the different selection criteria and different scenarios, along with the loss of favourable alleles and the rate of inbreeding measured by pedigree and runs of homozygosity. Results: For each selection criterion, hitch-hiking in the vicinity of the QTL appeared more extensive when accuracy of selection was higher and the number of QTL was lower. When inbreeding was measured by pedigree information, selection on genomic BLUP EBV resulted in lower levels of inbreeding than selection on phenotype BLUP EBV, but this did not always apply when inbreeding was measured by runs of homozygosity. Compared to genomic BLUP, selection on EBV from Bayesian Lasso led to less genetic drift, reduced loss of favourable alleles and more effectively controlled the rate of both pedigree and genomic inbreeding in all simulated scenarios. In addition, selection on EBV from Bayesian Lasso showed a higher selection differential for mendelian sampling terms than selection on genomic BLUP EBV. Conclusions: Neutral variation can be shaped to a great extent by the hitch-hiking effects associated with selection, rather than just by genetic drift. When implementing long-term genomic selection, strategies for genomic control of inbreeding are essential, due to a considerable hitch-hiking effect, regardless of the method that is used for prediction of EBV. © 2014 Liu et al.; licensee BioMed Central Ltd. Source


Cavicchi B.,431 As | Cavicchi B.,University of Oslo
Environmental Innovation and Societal Transitions | Year: 2016

The development of a low carbon society does not always deliver sustainable outcomes at local level, as in the case of bioenergy. This paper analyses the impacts of biogas development in Emilia Romagna (Italy) from a social, economic and environmental perspective (triple bottom line). Since 2009, the number of biogas plants has exponentially increased here, following the introduction of the feed-in tariff. Social opposition has been rising since. Therefore, the goal of the study is to investigate the causal processes of biogas development in order to understand what endangered its triple bottom line sustainability. The study does so by employing qualitative system dynamics (i.e. causal loop diagram). Results show that sustainability is threatened by weak local synergies, plants management and equipment deficiencies and agriculture related issues. The analysis suggests that policy interventions should focus on biomass supply and outputs diversification, governance, and social participation. © 2016 Elsevier B.V. Source


Robinson N.,431 As | Robinson N.,Flinders University | Winberg P.,University of Wollongong | Kirkendale L.,University of Wollongong
Journal of Applied Phycology | Year: 2013

Marine macroalgae (seaweeds) consist of a diverse range of species with diverse morphology and bioactive properties. The potential for genetic improvement to increase the value of the production of such molecules and other economically important traits is likely to be high as procedures for cultivation of many species are well established, genetic diversity is often high, sexual propagation is often possible and seaweeds generally have a short generation time that allows rapid transition from one selected generation to the next. The need for genetic improvement has been voiced by industry for many years. Despite this, there is little published research describing seaweed genetic improvement methodology, results or impact. This review draws on knowledge from other groups of species and describes options, benefits and knowledge needed for the genetic improvement of macroalgae. In conclusion, the review highlights how a well-designed genetic improvement program, which targets one or a few select economically valuable traits whilst limiting inbreeding, could provide potentially large benefits for industries reliant on the culture of seaweeds. Progress will, to a large extent, rely on the magnitude of genetic variation for the trait in question. © 2012 Springer Science+Business Media Dordrecht. Source

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