9 research outputs found
The composition of the protosolar disk and the formation conditions for comets
Conditions in the protosolar nebula have left their mark in the composition
of cometary volatiles, thought to be some of the most pristine material in the
solar system. Cometary compositions represent the end point of processing that
began in the parent molecular cloud core and continued through the collapse of
that core to form the protosun and the solar nebula, and finally during the
evolution of the solar nebula itself as the cometary bodies were accreting.
Disentangling the effects of the various epochs on the final composition of a
comet is complicated. But comets are not the only source of information about
the solar nebula. Protostellar disks around young stars similar to the protosun
provide a way of investigating the evolution of disks similar to the solar
nebula while they are in the process of evolving to form their own solar
systems. In this way we can learn about the physical and chemical conditions
under which comets formed, and about the types of dynamical processing that
shaped the solar system we see today.
This paper summarizes some recent contributions to our understanding of both
cometary volatiles and the composition, structure and evolution of protostellar
disks.Comment: To appear in Space Science Reviews. The final publication is
available at Springer via http://dx.doi.org/10.1007/s11214-015-0167-
Interversion de rangs dans la croissance des arbres en relation avec la taille de lâarbre, la compĂ©tition et les gradients climatiques pour quatre espĂšces forestiĂšres dominantes dans la canopĂ©e
SYNTHESIS OF PSEUDO-DISACCHARIDE ANALOGUES OF LIPID A: HAPTENS FOR THE GENERATION OF ANTIBODIES WITH GLYCOSIDASE ACTIVITY TOWARDS LIPID A
Rank severals in tree growth along tree size, competition and climatic gradients for four forest canopy dominant species in Central Spain
15 pages, 3 figures, 2 tables, 58 references. We thank Paloma Ruiz for her qualified help
with the SFI database management and Silvia Matesanz for help
with the analyses.[EN]: âą Interspecific differences in tree growth patterns with respect to biotic and abiotic factors are key for understanding forest structure and dynamics, and
predicting potential changes under climate change.
âą Repeated observations from the Spanish Forest Inventory (SFI) were used to parameterize maximum likelihood estimators of tree growth as a function
of tree size, competition indices and climate for Pinus pinaster, P. sylvestris, Quercus ilex and Q. pyrenaica.
âą Significant responses to both biotic and abiotic factors were found, with interspecific differences in species performance along competition, temperature
and precipitation gradients. Q. ilex was the species most tolerant to competition while P. pinaster was the species most sensitive to climatic
variation. Species relative positions shifted along gradients of these factors with rank reversals in species performance along size, competition and
climatic gradients.
âą The results based on average growth matched previous forestry classifications and experimental studies on relative growth rate (RGR).
âą When examining growth along studied abiotic and biotic gradients, a mismatch was found between species performance ranks as predicted by our
models and information derived from previous knowledge. Those discrepancies highlight the relevance of ontogeny and environmental heterogeneity
in defining species performance along competition gradients.[FR]: Interversion de rangs dans la croissance des arbres en relation avec la taille de lâarbre, la compĂ©tition et les gradients climatiques
pour quatre espÚces forestiÚres dominantes dans la canopée.
⹠Les différences interspécifiques dans les modÚles de croissance des arbres, pour ce qui concerne les facteurs biotiques et abiotiques, sont des clés pour
la compréhension des structures et des dynamiques forestiÚres, et pour prédire les changement potentiels avec le changement climatique.
âą Des observations rĂ©pĂ©tĂ©es de lâInventaire Forestier Espagnol (SFI) ont Ă©tĂ© utilisĂ©es pour paramĂ©trer les estimateurs de probabilitĂ© maximum de
croissance des arbres comme une fonction de la taille de lâarbre, des indices de compĂ©tition et du climat pour Pinus pinaster, Pinus sylvestris, Quercus
ilex et Quercus pyrenaica.
⹠Des réponses significatives aux facteurs biotiques et abiotiques ont été trouvées, avec des différences interspécifiques pour les performances des
espĂšces en relation avec la compĂ©tition, les gradients de tempĂ©rature et de prĂ©cipitations. Quercus ilex a Ă©tĂ© lâespĂšce la plus tolĂ©rante Ă la compĂ©tition
tandis que Pinus pinaster a Ă©tĂ© lâespĂšce la plus sensible aux variations climatiques. Les positions relatives des espĂšces ont changĂ© en relation avec les
gradients de ces facteurs avec des interversions de rang pour les performances des espÚces en relation avec la taille, la compétition et les gradients
climatiques.
⹠Les résultats basés sur la moyenne de croissance sont en adéquation avec la classification forestiÚre antérieure et les études expérimentales sur le taux
relatif de croissance (RGR).
⹠En examinant la croissance en relations avec les gradients biotiques et abiotiques étudiés, il a été trouvé une disparité entre les rangs de performance
des espĂšces prĂ©dits par nos modĂšles et les informations provenant des connaissances antĂ©rieures. Ces divergences soulignent lâimportance de lâontogĂ©nie
et de lâhĂ©tĂ©rogĂ©nĂ©itĂ© environnementale pour la dĂ©termination des performances des espĂšces en relation avec les gradients de compĂ©tition.DSG was supported by a grant from Comunidad
de Madrid through the network REMEDINAL (S-0505/AMB/0335).
IRU was supported by a FPI-MEC grant. MAZ acknowledges support
from grants CAM-UAH2005/2004, REN2000-745 (CICYT)
and CGL2005-05830-C03-01/BOS (CICYT). Interactions among
scientists from CSIC and Universidad de AlcalĂĄ were facilitated by
the forest research networks GLOBIMED (www.globimed.net) and
REDBOME (www.redbome.org). DvS was facilitated by an Erasmus
exchange grant.Peer reviewe