Expression of an Arabidopsis Aspartate Kinase/Homoserine Dehydrogenase Gene Is Metabolically Regulated by Photosynthesis-Related Signals but Not by Nitrogenous Compounds1

Although the control of carbon fixation and nitrogen assimilation has been studied in detail, relatively little is known about the regulation of carbon and nitrogen flow into amino acids. In this paper we report our study of the metabolic regulation of expression of an Arabidopsis aspartate kinase/homoserine dehydrogenase (AK/HSD) gene, which encodes two linked key enzymes in the biosynthetic pathway of aspartate family amino acids. Northern blot analyses, as well as expression of chimeric AK/HSD-β-glucuronidase constructs, have shown that the expression of this gene is regulated by the photosynthesis-related metabolites sucrose and phosphate but not by nitrogenous compounds. In addition, analysis of AK/HSD promoter deletions suggested that a CTTGACTCTA sequence, resembling the binding site for the yeast GCN4 transcription factor, is likely to play a functional role in the expression of this gene. Nevertheless, longer promoter fragments, lacking the GCN4-like element, were still able to confer sugar inducibility, implying that the metabolic regulation of this gene is apparently obtained by multiple and redundant promoter sequences. The present and previous studies suggest that the conversion of aspartate into either the storage amino acid asparagine or aspartate family amino acids is subject to a coordinated, reciprocal metabolic control, and this biochemical branch point is a part of a larger, coordinated regulatory mechanism of nitrogen and carbon storage and utilization.

Climate simulation for 125 kyr BP with a coupled ocean-atmosphere general circulation model

The ECHAM-1 T21/LSG coupled ocean-atmosphere general circulation model (GCM) is used to simulate climatic conditions at the last interglacial maximum (Eemian. 125 kyr BP). The results reflect thc expected surface temperature changes (with respect to the control run) due to the amplification (reduction) of the seasonal cycle of insolation in the Northern (Southern) Hemisphere. A number of simulated features agree with previous results from atmospheric GCM simulations e.g. intensified summer southwest monsoons) except in the Northern Hemisphere poleward of 30 degrees N. where dynamical feedback, in the North Atlantic and North Pacific increase zonal temperatures about 1 degrees C above what would be predicted from simple energy balance considerations. As this is the same area where most of the terrestrial geological data originate, this result suggests that previous estimates of Eemian global average temperature might have been biased by sample distribution. This conclusion is supported by the fact that the estimated global temperature increase of only 0.3 degrees C greater than the control run ha, been previously shown to be consistent a with CLIMAP sea surface temperature estimates. Although the Northern Hemisphere summer monsoon is intensified. globally averaged precipitation over land is within about 1% of the present, contravening some geological inferences bur not the deep-sea delta(13)C estimates of terrestrial carbon storage changes. Winter circulation changes in the northern Arabian Sea. driven by strong cooling on land, are as large as summer circulation changes that are the usual focus of interest, suggesting that interpreting variations in the Arabian Sea. sedimentary record solely in terms of the summer monsoon response could sometimes lead to errors. A small monsoonal response over northern South America suggests that interglacial paleotrends in this region were not just due to El Nino variations.

Planktonic foraminiferal assemblages of the Paleocene-Eocene Thermal Maximum of ODP Hole 113-690B

High-resolution study of Antarctic planktonic foraminiferal assemblages (Ocean Drilling Program Site 690, Weddell Sea) shows that these microplankton underwent a stepwise series of changes during the Paleocene-Eocene thermal maximum (PETM). Initiation of this response coincides with the onset of the carbon isotope excursion (CIE) but precedes the benthic foraminiferal mass extinction. The "top-to-bottom" succession in the biotic response indicates that the surface ocean/atmosphere was affected before the deep sea. The earliest stage of the faunal response entailed a conspicuous turnover within the shallow-dwelling genus Acarinina and a succession of stratigraphic first appearances. The genus Morozovella, large (>180 µm) biserial planktonics, and A. wilcoxensis are all restricted to the lower CIE within this PETM section. Acarininid populations crashed as the ocean/climate system ameliorated during the CIE recovery, reflecting atypical surface water conditions. This transient decline in acarininids is paralleled by a marked increase in carbonate content of sediments. It is postulated that this interval of carbonate enrichment, and its unusual microfauna, reflects enhanced carbon storage within reservoirs of the global carbon cycle other than the marine carbonate system (sensu Broecker et al., 1993, doi:10.1029/93PA00423; Ravizza et al., 2001, doi:10.1029/2000PA000541).

Fiji mapped mangrove ecosystem service rankings in GeoJSON format

Incorporating the values of the services that ecosystems provide into decision making is becoming increasingly common in nature conservation and resource management policies, both locally and globally. Yet with limited funds for conservation of threatened species and ecosystems there is a desire to identify priority areas where investment efficiently conserves multiple ecosystem services. We mapped four mangrove ecosystems services (coastal protection, fisheries, biodiversity, and carbon storage) across Fiji. Using a cost-effectiveness analysis, we prioritised mangrove areas for each service, where the effectiveness was a function of the benefits provided to the local communities, and the costs were associated with restricting specific uses of mangroves. We demonstrate that, although priority mangrove areas (top 20%) for each service can be managed at relatively low opportunity costs (ranging from 4.5 to 11.3% of overall opportunity costs), prioritising for a single service yields relatively low co-benefits due to limited geographical overlap with priority areas for other services. None-the-less, prioritisation of mangrove areas provides greater overlap of benefits than if sites were selected randomly for most ecosystem services. We discuss deficiencies in the mapping of ecosystems services in data poor regions and how this may impact upon the equity of managing mangroves for particular services across the urban-rural divide in developing countries. Finally we discuss how our maps may aid decision-makers to direct funding for mangrove management from various sources to localities that best meet funding objectives, as well as how this knowledge can aid in creating a national mangrove zoning scheme.

Ages and isotopic signatures of peat cores from a boreal landscape, Interior Alaska

To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate ~600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing season temperature record from Fairbanks. This concurrent wetland succession and reduced growth of black spruce trees indicates a step-wise ecosystem-level response to a change in regional climate. In 2001, fire was observed coincident with permafrost collapse and resulted in lateral expansion of the peatland. These observations and the peat profile suggest that future warming and/or increased fire disturbance could promote permafrost degradation, peatland expansion, and increase carbon storage across this landscape; however, the development of drought conditions could reduce the success of both black spruce and Sphagnum, and potentially decrease the long-term ecosystem carbon storage.

Changes in organic matter production and accumulation as a mechanism for isotopic evolution in the Mesoproterozoic ocean

Mesoproterozoic marine successions worldwide record a shift in average delta(13)C values from 0 to +3.5parts per thousand, with the latter value evident in successions younger than 1250 Ma. New carbon isotope data from the similar to 1300 to 1270 Ma Dismal Lakes Group, Arctic Canada, provide further insight into this fundamental transition. Data reveal that the shift to higher VC values was gradual and marked by occasional excursions to values less than 0 parts per thousand. When compared to records from older and younger marine successions, it is evident that the difference between isotopic minima and maxima increased with time, indicating that the marine system evolved to become isotopically more variable. We interpret these patterns to record an increase in the crustal inventory of organic carbon, reflecting eukaryotic diversification and a change in the locus of organic carbon burial to include anoxic deep marine sites where preservation potential was high. We speculate that the release of O-2 to Earth's surface environments associated with increased organic carbon storage induced irreversible changes in the Mesoproterozoic biosphere, presaging the more extreme environmental and evolutionary developments of the Neoproterozoic.

Negative relationships between the nutrient and carbohydrate content of the seagrass Thalassia testudinum

This study documents relationships between plant nutrient content and rhizome carbohydrate content of a widely distributed seagrass species, Thalassia testudinum, in Florida. Five distinct seagrass beds were sampled for leaf nitrogen, leaf phosphorus, and rhizome carbohydrate content from 1997 to 1999. All variables displayed marked intra- and inter- regional variation. Elemental ratios (mean N:P ± S.E.) were lowest for Charlotte Harbor (9.9 ± 0.2) and highest for Florida Bay (53.5 ± 0.9), indicating regional shifts in the nutrient content of plant material. Rhizome carbohydrate content (mean ± S.E.) was lowest for Anclote Keys (21.8 ± 1.6 mg g−1 FM), and highest for Homosassa Bay (40.7 ± 1.7 mg g−1 FM). Within each region, significant negative correlations between plant nutrient and rhizome carbohydrate content were detected; thus, nutrient-replete plants displayed low carbohydrate content, while nutrient-deplete plants displayed high carbohydrate content. Spearman's rank correlations between nutrient and carbohydrate content varied from a minimum in Tampa Bay (ρ = −0.2) to a maximum in Charlotte Harbor (ρ = −0.73). Linear regressions on log-transformed data revealed similar trends. This consistent trend across five distinct regions suggests that nutrient supply may play an important role in the regulation of carbon storage within seagrasses. Here we present a new hypothesis for studies which aim to explain the carbohydrate dynamics of benthic plants.

Woody Debris in the Mangrove Forests of South Florida

Woody debris is abundant in hurricane-impacted forests. With a major hurricane affecting South Florida mangroves approximately every 20 yr, carbon storage and nutrient retention may be influenced greatly by woody debris dynamics. In addition, woody debris can influence seedling regeneration in mangrove swamps by trapping propagules and enhancing seedling growth potential. Here, we report on line-intercept woody debris surveys conducted in mangrove wetlands of South Florida 9–10 yr after the passage of Hurricane Andrew. The total volume of woody debris for all sites combined was estimated at 67 m3/ha and varied from 13 to 181 m3/ha depending upon differences in forest height, proximity to the storm, and maximum estimated wind velocities. Large volumes of woody debris were found in the eyewall region of the hurricane, with a volume of 132 m3/ha and a projected woody debris biomass of approximately 36 t/ha. Approximately half of the woody debris biomass averaged across all sites was associated as small twigs and branches (fine woody debris), since coarse woody debris >7.5 cm felled during Hurricane Andrew was fairly well decomposed. Much of the small debris is likely to be associated with post-hurricane forest dynamics. Hurricanes are responsible for large amounts of damage to mangrove ecosystems, and components of associated downed wood may provide a relative index of disturbance for mangrove forests. Here, we suggest that a fine:coarse woody debris ratio ≤0.5 is suggestive of a recent disturbance in mangrove wetlands, although additional research is needed to corroborate such findings.

Allocation of Biomass and Net Primary Productivity of Mangrove Forests along Environmental Gradients in the Florida Coastal Everglades, USA

Vegetation patterns of mangroves in the Florida Coastal Everglades (FCE) result from the interaction of environmental gradients and natural disturbances (i.e., hurricanes), creating an array of distinct riverine and scrub mangroves across the landscape. We investigated how landscape patterns of biomass and total net primary productivity (NPPT), including allocation in above- and below-ground mangrove components, vary inter-annually (2001–2004) across gradients in soil properties and hydroperiod in two distinct FCE basins: Shark River Estuary and Taylor River Slough. We propose that the allocation of belowground biomass and productivity (NPPB) relative to aboveground allocation is greater in regions with P limitation and permanent flooding. Porewater sulfide was significantly higher in Taylor River (1.2 ± 0.3 mM) compared to Shark River (0.1 ± 0.03 mM) indicating the lack of a tidal signature and more permanent flooding in this basin. There was a decrease in soil P density and corresponding increase in soil N:P from the mouth (28) to upstream locations (46–105) in Shark River that was consistent with previous results in this region. Taylor River sites showed the highest P limitation (soil N:P > 60). Average NPPT was double in higher P environments (17.0 ± 1.1 Mg ha−1 yr−1) compared to lower P regions (8.3 ± 0.3 Mg ha−1 yr−1). Root biomass to aboveground wood biomass (BGB:AWB) ratio was 17 times higher in P-limited environments demonstrating the allocation strategies of mangroves under resource limitation. Riverine mangroves allocated most of the NPPT to aboveground (69%) while scrub mangroves showed the highest allocation to belowground (58%). The total production to biomass (P:B) ratios were lower in Shark River sites (0.11 yr−1); whereas in Taylor River sites P:B ratios were higher and more variable (0.13–0.24 yr−1). Our results suggest that the interaction of lower P availability in Taylor River relative to Shark River basin, along with higher sulfide and permanent flooding account for higher allocation of belowground biomass and production, at expenses of aboveground growth and wood biomass. These distinct patterns of carbon partitioning between riverine and scrub mangroves in response to environmental stress support our hypothesis that belowground allocation is a significant contribution to soil carbon storage in forested wetlands across FCE, particularly in P-limited scrub mangroves. Elucidating these biomass strategies will improve analysis of carbon budgets (storage and production) in neotropical mangroves and understanding what conditions lead to net carbon sinks in the tropical coastal zone.

Geochemical data and radiocarbon ages of organic matter fractions and bacteriohopanepolyol data of sediment core GeoB6518-1 from the Congo River basin

The age of organic material discharged by rivers provides information about its sources and carbon cycling processes within watersheds. While elevated ages in fluvially-transported organic matter are usually explained by erosion of soils and sediments, it is commonly assumed that mainly young organic material is discharged from flat tropical watersheds due to their extensive plant cover and high carbon turnover. Here we present compound-specific radiocarbon data of terrigenous organic fractions from a sedimentary archive offshore the Congo River in conjunction with molecular markers for methane-producing land cover reflecting wetland extent in the watershed. We find that the Congo River has been discharging aged organic matter for several thousand years with increasing ages from the mid- to the Late Holocene. This suggests that aged organic matter in modern samples is concealed by radiocarbon from nuclear weapons testing. By comparison to indicators for past rainfall changes we detect a systematic control of organic matter sequestration and release by continental hydrology mediating temporary carbon storage in wetlands. As aridification also leads to exposure and rapid remineralization of large amounts of previously stored labile organic matter we infer that this process may cause a profound direct climate feedback currently underestimated in carbon cycle assessments.

Peatland depths and radiocarbon dates, recent decades, North America

Peatland ecosystems store about 500-600 Pg of organic carbon, largely accumulated since the last glaciation. Whether they continue to sequester carbon or release it as greenhouse gases, perhaps in large amounts, is important in Earth's temperature dynamics. Given both ages and depths of numerous dated sample peatlands, their rate of carbon sequestration can be estimated throughout the Holocene. Here we use average values for carbon content per unit volume, the geographical extent of peatlands, and ecological models of peatland establishment and growth, to reconstruct the time-trajectory of peatland carbon sequestration in North America and project it into the future. Peatlands there contain ~163 Pg of carbon. Ignoring effects of climate change and other major anthropogenic disturbances, the rate of carbon accumulation is projected to decline slowly over millennia as reduced net carbon accumulation in existing peatlands is largely balanced by new peatland establishment. Peatlands are one of few long-term terrestrial carbon sinks, probably important for global carbon regulation in future generations. This study contributes to a better understanding of these ecosystems that will assist their inclusion in earth-system models, and therefore their management to maintain carbon storage during climate change.

Radiocarbon dates of peatland initiation across the northern high latitudes

A compilation of basal dates of peatland initiation across the northern high latitudes, associated metadata including location, age, raw and calibrated radiocarbon ages, and associated references. Includes previously published datasets from sources below as well as 365 new data points.

CO2 concentration and stable isotope ratios of three Antarctic ice cores covering the period from 149.4 - 1.5 kyr before 1950

We present new d13C measurements of atmospheric CO2 covering the last glacial/interglacial cycle, complementing previous records covering Terminations I and II. Most prominent in the new record is a significant depletion in d13C(atm) of 0.5 permil occurring during marine isotope stage (MIS) 4, followed by an enrichment of the same magnitude at the beginning of MIS 3. Such a significant excursion in the record is otherwise only observed at glacial terminations, suggesting that similar processes were at play, such as changing sea surface temperatures, changes in marine biological export in the Southern Ocean (SO) due to variations in aeolian iron fluxes, changes in the Atlantic meridional overturning circulation, upwelling of deep water in the SO, and long-term trends in terrestrial carbon storage. Based on previous modeling studies, we propose constraints on some of these processes during specific time intervals. The decrease in d13C(atm) at the end of MIS 4 starting approximately 64 kyr B.P. was accompanied by increasing [CO2]. This period is also marked by a decrease in aeolian iron flux to the SO, followed by an increase in SO upwelling during Heinrich event 6, indicating that it is likely that a large amount of d13C-depleted carbon was transferred to the deep oceans previously, i.e., at the onset of MIS 4. Apart from the upwelling event at the end of MIS 4 (and potentially smaller events during Heinrich events in MIS 3), upwelling of deep water in the SO remained reduced until the last glacial termination, whereupon a second pulse of isotopically light carbon was released into the atmosphere.

Nitrate metabolism in the dinoflagellate Lingulodinium polyedrum

Les dinoflagellés sont des eucaryotes unicellulaires retrouvés dans la plupart des écosystèmes aquatiques du globe. Ces organismes amènent une contribution substantielle à la production primaire des océans, soit en tant que membre du phytoplancton, soit en tant que symbiontes des anthozoaires formant les récifs coralliens. Malheureusement, ce rôle écologique majeur est souvent négligé face à la capacité de certaines espèces de dinoflagellés à former des fleurs d'eau, parfois d'étendue et de durée spectaculaires. Ces floraisons d'algues, communément appelées "marées rouges", peuvent avoir de graves conséquences sur les écosystèmes côtiers, sur les industries de la pêche et du tourisme, ainsi que sur la santé humaine. Un des facteurs souvent corrélé avec la formation des fleurs d'eau est une augmentation dans la concentration de nutriments, notamment l’azote et le phosphore. Le nitrate est un des composants principaux retrouvés dans les eaux de ruissellement agricoles, mais également la forme d'azote bioaccessible la plus abondante dans les écosystèmes marins. Ainsi, l'agriculture humaine a contribué à magnifier significativement les problèmes associés aux marées rouges au niveau mondial. Cependant, la pollution ne peut pas expliquer à elle seule la formation et la persistance des fleurs d'eau, qui impliquent plusieurs facteurs biotiques et abiotiques. Il est particulièrement difficile d'évaluer l'importance relative qu'ont les ajouts de nitrate par rapport à ces autres facteurs, parce que le métabolisme du nitrate chez les dinoflagellés est largement méconnu. Le but principal de cette thèse vise à remédier à cette lacune. J'ai choisi Lingulodinium polyedrum comme modèle pour l'étude du métabolisme du nitrate, parce que ce dinoflagellé est facilement cultivable en laboratoire et qu'une étude transcriptomique a récemment fourni une liste de gènes pratiquement complète pour cette espèce. Il est également intéressant que certaines composantes moléculaires de la voie du nitrate chez cet organisme soient sous contrôle circadien. Ainsi, dans ce projet, j'ai utilisé des analyses physiologiques, biochimiques, transcriptomiques et bioinformatiques pour enrichir nos connaissances sur le métabolisme du nitrate des dinoflagellés et nous permettre de mieux apprécier le rôle de l'horloge circadienne dans la régulation de cette importante voie métabolique primaire. Je me suis tout d'abord penché sur les cas particuliers où des floraisons de dinoflagellés sont observées dans des conditions de carence en azote. Cette idée peut sembler contreintuitive, parce que l'ajout de nitrate plutôt que son épuisement dans le milieu est généralement associé aux floraisons d'algues. Cependant, j’ai découvert que lorsque du nitrate était ajouté à des cultures initialement carencées ou enrichies en azote, celles qui s'étaient acclimatées au stress d'azote arrivaient à survivre près de deux mois à haute densité cellulaire, alors que les cellules qui n'étaient pas acclimatées mourraient après deux semaines. En condition de carence d'azote sévère, les cellules arrivaient à survivre un peu plus de deux semaines et ce, en arrêtant leur cycle cellulaire et en diminuant leur activité photosynthétique. L’incapacité pour ces cellules carencées à synthétiser de nouveaux acides aminés dans un contexte où la photosynthèse était toujours active a mené à l’accumulation de carbone réduit sous forme de granules d’amidon et corps lipidiques. Curieusement, ces deux réserves de carbone se trouvaient à des pôles opposés de la cellule, suggérant un rôle fonctionnel à cette polarisation. La deuxième contribution de ma thèse fut d’identifier et de caractériser les premiers transporteurs de nitrate chez les dinoflagellés. J'ai découvert que Lingulodinium ne possédait que très peu de transporteurs comparativement à ce qui est observé chez les plantes et j'ai suggéré que seuls les membres de la famille des transporteurs de nitrate de haute affinité 2 (NRT2) étaient réellement impliqués dans le transport du nitrate. Le principal transporteur chez Lingulodinium était exprimé constitutivement, suggérant que l’acquisition du nitrate chez ce dinoflagellé se fondait majoritairement sur un système constitutif plutôt qu’inductible. Enfin, j'ai démontré que l'acquisition du nitrate chez Lingulodinium était régulée par la lumière et non par l'horloge circadienne, tel qu'il avait été proposé dans une étude antérieure. Finalement, j’ai utilisé une approche RNA-seq pour vérifier si certains transcrits de composantes impliquées dans le métabolisme du nitrate de Lingulodinium étaient sous contrôle circadien. Non seulement ai-je découvert qu’il n’y avait aucune variation journalière dans les niveaux des transcrits impliqués dans le métabolisme du nitrate, j’ai aussi constaté qu’il n’y avait aucune variation journalière pour n’importe quel ARN du transcriptome de Lingulodinium. Cette découverte a démontré que l’horloge de ce dinoflagellé n'avait pas besoin de transcription rythmique pour générer des rythmes physiologiques comme observé chez les autres eukaryotes.

Stratégie d'amélioration de la résistance mécanique des zones de connecteurs

Le bois subit une demande croissante comme matériau de construction dans les bâtiments de grandes dimensions. Ses qualités de matériau renouvelable et esthétique le rendent attrayant pour les architectes. Lorsque comparé à des produits fonctionnellement équivalents, il apparait que le bois permet de réduire la consommation d’énergie non-renouvelable. Sa transformation nécessite une quantité d’énergie inférieure que l’acier et le béton. Par ailleurs, par son origine biologique, une structure en bois permet de stocker du carbone biogénique pour la durée de vie du bâtiment. Maintenant permis jusqu’à six étages de hauteur au Canada, les bâtiments de grande taille en bois relèvent des défis de conception. Lors du dimensionnement des structures, les zones des connecteurs sont souvent les points critiques. Effectivement, les contraintes y sont maximales. Les structures peuvent alors apparaitre massives et diminuer l’innovation architecturale. De nouvelles stratégies doivent donc être développées afin d’améliorer la résistance mécanique dans les zones de connecteurs. Différents travaux ont récemment porté sur la création ou l’amélioration de types d’assemblage. Dans cette étude, l’accent est mis sur le renforcement du bois utilisé dans la région de connexion. L’imprégnation a été choisie comme solution de renfort puisque la littérature démontre qu’il est possible d’augmenter la dureté du bois avec cette technique. L’utilisation de cette stratégie de renfort sur l’épinette noire (Picea Mariana (Mill.) BSP) pour une application structurale est l’élément de nouveauté dans cette recherche. À défaut d’effectuer une imprégnation jusqu’au coeur des pièces, l’essence peu perméable de bois employée favorise la création d’une mince couche en surface traitée sans avoir à utiliser une quantité importante de produits chimiques. L’agent d’imprégnation est composé de 1,6 hexanediol diacrylate, de triméthylopropane tricacrylate et d’un oligomère de polyester acrylate. Une deuxième formulation contenant des nanoparticules de SiO2 a permis de vérifier l’effet des nanoparticules sur l’augmentation de la résistance mécanique du bois. Ainsi, dans ce projet, un procédé d’imprégnation vide-pression a servi à modifier un nouveau matériau à base de bois permettant des assemblages plus résistants mécaniquement. Le test de portance locale à l’enfoncement parallèle au fil d’un connecteur de type tige a été réalisé afin de déterminer l’apport du traitement sur le bois utilisé comme élément de connexion. L’effet d’échelle a été observé par la réalisation du test avec trois diamètres de boulons différents (9,525 mm, 12,700 mm et 15,875 mm). En outre, le test a été effectué selon un chargement perpendiculaire au fil pour le boulon de moyen diamètre (12,700 mm). La corrélation d’images numériques a été utilisée comme outil d’analyse de la répartition des contraintes dans le bois. Les résultats ont démontré une portance du bois plus élevée suite au traitement. Par ailleurs, l’efficacité est croissante lorsque le diamètre du boulon diminue. C’est un produit avec une valeur caractéristique de la portance locale parallèle au fil de 79% supérieure qui a été créé dans le cas du test avec le boulon de 9,525 mm. La raideur du bois a subi une augmentation avoisinant les 30%. Suite au traitement, la présence d’une rupture par fissuration est moins fréquente. Les contraintes se distribuent plus largement autour de la région de connexion. Le traitement n’a pas produit d’effet significatif sur la résistance mécanique de l’assemblage dans le cas d’un enfoncement du boulon perpendiculairement au fil du bois. De même, l’effet des nanoparticules en solution n’est pas ressorti significatif. Malgré une pénétration très faible du liquide à l’intérieur du bois, la couche densifiée en surface créée suite au traitement est suffisante pour produire un nouveau matériau plus résistant dans les zones de connexion. Le renfort du bois dans la région des connecteurs doit influencer le dimensionnement des structures de grande taille. Avec des éléments de connexion renforcés, il sera possible d’allonger les portées des poutres, multipliant ainsi les possibilités architecturales. Le renfort pourra aussi permettre de réduire les sections des poutres et d’utiliser une quantité moindre de bois dans un bâtiment. Cela engendrera des coûts de transport et des coûts reliés au temps d’assemblage réduits. De plus, un connecteur plus résistant permettra d’être utilisé en moins grande quantité dans un assemblage. Les coûts d’approvisionnement en éléments métalliques et le temps de pose sur le site pourront être revus à la baisse. Les avantages d’un nouveau matériau à base de bois plus performant utilisé dans les connexions permettront de promouvoir le bois dans les constructions de grande taille et de réduire l’impact environnemental des bâtiments.