The objectives of this study were to evaluate whether advanced common bean lines differ in phenological, morphological, grain yield and cooking quality characters; to study the linear correlations between these characters; and to select superior lines for these characters for use in breeding programs. For this purpose, 14 common bean lines of trial Use and Cultivation South -Brazilian Bean (VCU - SB) were growing in normal rainy 2012/2013 and in dry season 2013 in Santa Maria, Rio Grande do Sul, Brazil. Data were subjected to analysis of individual and joint variance, using the F test at 5 % probability. If the effect of line and control was significant, the stratification of averages was performed by the Scott-Knott test at 5 % probability. Interaction line x growing season significant was observed for the characters: number of days from emergence to flowering, reproductive period, cycle, lodging, stay green, number of lateral branches, number of pods per plant, number of grains per plant, number of grains per pod, weight of 100 grains, grain yield, grain length and width. The line and control evaluated differed significantly among the characters: number of days from emergence to flowering, cycle, number of nodes on main stem, width and thickness of grains, grain brightness and time of cooking, allowing you to select improved lines for these characters. Positive linear correlation of high magnitude was observed between grain yield and number of pods per plant (r = 0.632) and weight of 100 grains (r = 0.942), while the grain yield and the number of days from emergence to flowering (r = -0.857) and the cycle (r = -0.677) had high negative linear correlation. The LP 09-40 line and BRS Valente control have the lower note of lodging in the two growing seasons, allowing the use of these blocks of crosses to obtain lines with erect architecture. The CNFP 10794 and DF 06-17 lines may be used as parents in hybrid combinations for presenting high yield and reduced cooking time and high yield and early cycle, respectively. / Os objetivos deste trabalho foram avaliar se as linhagens avançadas de feijão diferem quanto aos caracteres fenológicos, morfológicos, de produção e de qualidade de cozimento; estudar as correlações lineares entre esses caracteres; e selecionar linhagens superiores para esses caracteres para uso em programas de melhoramento. Para tanto, foram avaliadas 14 linhagens de feijão do Ensaio de Valor Cultivo e Uso Sul-brasileiro de Feijão (VCU-SB) em cultivo de safra 2012/2013 e de safrinha 2013 em Santa Maria, Rio Grande do Sul, Brasil. Os dados obtidos foram submetidos à análise de variância individual e conjunta, usando o teste F a 5% de probabilidade. Sendo o efeito de linhagens significativo, a estratificação das médias obtidas foi realizada pelo teste de Scott-Knott a 5% de probabilidade. Interação linhagem x época de cultivo significativa foi observada para os caracteres: número de dias da emergência a floração, período reprodutivo, ciclo, acamamento, stay green, número de ramos laterais, número de vagens por planta, número de grãos por planta, número de grãos por vagem, massa de 100 grãos, produtividade de grãos, comprimento e largura de grãos. As linhagens e as testemunhas avaliadas diferiram significativamente para os caracteres: número de dias da emergência a floração, ciclo, número de nós no ramo principal, largura e espessura dos grãos, luminosidade dos grãos e tempo de cozimento dos grãos, possibilitando a seleção de linhagens superiores para esses caracteres. Correlação linear positiva de alta magnitude foi observada entre a produtividade de grãos e o número de vagens por planta (r = 0,632) e a massa de 100 grãos (r = 0,942), enquanto que a produtividade de grãos e o número de dias da emergência a floração (r = -0,857) e o ciclo (r = -0,677), apresentaram alta correlação linear negativa. A linhagem LP 09-40 e a testemunha BRS Valente apresentam as menores notas de acamamento nas duas épocas de cultivo, o que possibilita o uso dessas em blocos de cruzamentos para a obtenção de linhagens com porte ereto. As linhagens CNFP 10794 e DF 06-17 poderão ser utilizadas como genitores em combinações híbridas por apresentarem alta produtividade de grãos e reduzido tempo de cozimento e alta produtividade de grãos e ciclo reduzido, respectivamente.

Le biome boréal, emmagasinant d’importantes quantités de carbone en son sol et recouvrant une majorité du territoire alaskien, fennoscandien et russe, contribue grandement au système climatique. Toutefois, les variabilités climatiques et les propriétés de l’écosystème, notamment en ce qui a trait à la présence ou l’absence de pergélisol, complexifient la quantification de la variabilité des bilans de carbone du biome boréal, au sein duquel se retrouvent des écosystèmes forestiers, lentiques et de zones humides. Ces bilans de carbone sont grandement influencés par le début et la fin de la saison de croissance photosynthétique, étant à leur tour dépendants de plusieurs variables environnementales telles que la température de l’air et du sol, le contenu du sol en eau, les stades de développement de la végétation, etc. Cette recherche vise à quantifier l’impact de ces variabilités environnementales sur la variabilité des moments où se produisent le début et la fin de la saison de croissance photosynthétique, en distinguant les forêts boréales avec et sans pergélisol. La saison de croissance photosynthétique est caractérisée à partir de la productivité primaire brute dérivée de mesures covariance des turbulences provenant de 40 sites-années d’observation à travers la forêt boréale nord-américaine où l’épinette noire est l’espèce d’arbre dominante. Les variables environnementales considérées étaient les températures de l’air et du sol, les stades de développement de la végétation, le couvert nival, le rayonnement photosynthétiquement actif et le contenu du sol en eau. Le cadre statistique choisi incluait le calcul des coefficients de corrélations de Pearson, l’analyse des points communs et la modélisation par équations structurelles. Les résultats de cette étude montrent que la variabilité du début de la saison de croissance dans les sites sans pergélisol est contrôlée directement par la variabilité annuelle des stades de développement de la végétation ainsi que par le moment où survient le dégel du sol. Ce résultat souligne ainsi l’importance de l’accès à l’eau liquide du sol afin que la végétation initie la photosynthèse. Aucune variable environnementale ne pouvait significativement expliquer le contrôle du début de la photosynthèse au sein des sites avec pergélisol. À l’automne, le contenu du sol en eau ainsi que le début du couvert nival influencent directement la variabilité de la fin de la saison de croissance photosynthétique. Il est alors montré que la disponibilité de l’eau peut mener à une cessation plus hâtive de la photosynthèse à l’automne. L’effet de l’apparition du couvert nival est quant à lui opposé dans les sites avec et sans pergélisol. Son retard dans les sites sans pergélisol témoigne d’une température de l’air suffisamment élevée pour que les précipitations tombent sous forme liquide, prolongeant ainsi les activités photosynthétiques. Son retard dans les sites avec pergélisol signifie plutôt des précipitations neigeuses moindres, retardant ainsi l’apparition d’une couche isolante pour le sol, qui aurait pu allonger la saison de croissance photosynthétique. Cette étude contribue à clarifier les processus contrôlant le début et la fin de la saison de croissance photosynthétique et aidera à améliorer la compréhension des effets des changements climatiques sur la force du puits de carbone de la forêt boréale nord-américaine. / The boreal forest, storing large amounts of carbon in its soil and covering a majority of the Alaskan, Canadian, Fennoscandian and Russian territory, is an integral part of the climate system. However, climatic variability and ecosystem properties, particularly with regards to the presence or absence of permafrost, limits our understanding of the carbon balance variability in the boreal biome, which comprises forest, lake and wetland ecosystems. The boreal carbon sink-source strength is greatly influenced by phenological events, including the start and end of the photosynthetic growing season, which are themselves dependent on several environmental variables such as air and soil temperature, soil water content, vegetation development stages, etc. This research aims to provide new insights on the influence of environmental variability on the variability in the timing of the photosynthetic growing season, by broadly distinguishing between boreal forests with and without permafrost. The photosynthetic growing season is characterized using gross primary productivity derived from eddy covariance measurements of net ecosystem carbon dioxide exchange. Data from 40 black spruce- dominated site-years of observation across the North American boreal forest are used. The considered environmental predictors were air and soil temperatures, vegetation development stages, snow cover, photosynthetically active radiation and soil water content. The statistical framework included the calculation of Pearson correlation coefficients, commonality analyses and structural equation modeling. This study shows that the variability in the start of the growing season in permafrost-free sites is directly controlled by the variability in vegetation development stage as well as by the thawing of seasonally frozen ground. This result thus emphasizes the importance of access to liquid soil water for the vegetation to initiate photosynthesis. No environmental variable could significantly explain photosynthesis recovery in sites with permafrost. In fall, the soil water content as well as the start of snow cover directly influence the variability in the end of the photosynthetic growing season. These results suggest that the availability of water can limit photosynthesis in the fall. The effect of snow cover is opposite in sites with and without permafrost. A delay in the appearance of continuous snow cover in sites without permafrost indicates that the air temperature is high enough for precipitation to fall in liquid form and for photosynthesis to continue. In contrast, its delay in sites with permafrost indicates less snowfall, thus delaying the appearance of an insulating layer for the soil, which could have lengthened the photosynthetic growing season. This study sheds light on the controls of the annual variation of the timing of the photosynthetic growing season and will help understanding of the effects of climate change on the strength of the North American boreal forest carbon sink.

Les changements climatiques sont susceptibles d’affecter la croissance, le développement et la régénération des pessières noires de la forêt boréale. Les échecs de régénération dans les pessières à mousses (PM) de l’ouest du Québec causent des trouées dans la mosaïque forestière dense et augmentent la proportion de pessières à lichens (PL) dans le paysage. Les objectifs de l’étude sont de déterminer si les caractéristiques contrastantes des PM et des PL engendrent différents taux de photosynthèse maximale (Amax) chez les épinettes noires sur un gradient latitudinal ou saisonnier. Ensuite, l’étude tentera de déterminer si le Amax des individus reflète leurs capacités physiologiques par leur taux de carboxylation maximal (Vcmax) et de transport des électrons maximal (Jmax) extraits de courbes de réponse au CO2. Les taux de Vcmax et Jmax sont différents entre les PM et les PL car l’acquisition de ces nutriments semble différente. La latitude influence les valeurs de Vcmax et Jmax, mais l’effet serait causé par les caractéristiques floristiques et la composition du sol des placettes plutôt que par la latitude. Les capacités physiologiques ne se reflètent pas dans les valeurs de Amax, autant pour le type de peuplement que la latitude, car Amax serait limité par la concentration en CO2 qui ne permet pas la saturation de l’enzyme rubisco. Malgré l’absence de différence entre le Amax des PM et des PL, l’augmentation de la concentration en CO2 et de la température risque de créer un écart de Amax entre les types de peuplement, considérant leurs capacités physiologiques différentes. / Climate change is likely to affect the growth, development and regeneration of black spruce stands across the boreal forest. Regeneration failures cause gaps in the dense black spruce-feathermoss (BSFM) mosaic increasing the landscape proportion of open lichen-woodland (LW). The aims of the study are to determine whether the contrasting characteristics of BSFM and LW induce different light-saturated maximum photosynthesis (Amax) in black spruce trees across a latitudinal or seasonal gradient. Then the study will attempt to determine if Amax is likely to reflect their physiological capacities based on their maximum carboxylation rate (Vcmax) and maximum electron transport rate (Jmax) derived from CO2 response curves. Vcmax and Jmax are different between BSFM and LW mainly because nutrient acquisition seems different between stand types. Latitude affects values of Vcmax and Jmax, but the effect could be explained by soil and vegetation composition between experimental plots rather than by latitude. Physiological capacities do not match Amax values for stand type and latitude because Amax would be limited by CO2 concentration which does not allow saturation of rubisco. Despite the lack of difference between the Amax of BSFM and LW stands, future increase in CO2 concentration and temperature could induce a gap between their respective photosynthesis rates because of their different physiological capacities.