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Logging, grazing, wood extraction, and anthropogenic fires are pervasive throughout the subtropical dry vegetation of South America leading to changes in woodlands structure and ultimately its degradation. The Chac ohaco biome encompasses the second-largest forest in South America and has a long history of intensive use. We sought to characterize the structure and heterogeneity of its woodlands across biogeo graphic subunits and climatic gradients, and evaluate structure controls. We quantified canopy height, cover, vertical complexity, vegetation amount above 3 m and total veg etation amount over 58 woodlands within the Argentinean Chaco by means of terres trial laser scanner. We assessed the relationship between three groups near the maximum, average and minimum values of each structural variable and precipitation, temperature and temperature of the coldest month using quantile regressions. We found large variability in structural attributes within each biogeographical subunit, showing woodland areas with similar structure across broad gradients of climate. This suggests a considerable impact of current and past land use in shaping woodland struc tures across the Chaco. Overall, structural variables were positively associated with precipitation and temperature, albeit more strongly to the former, except for canopy height, which showed a strong association with mean temperature of the coldest month. We hypothesize that land-use impact on woodland structure decreases with increasing precipitation, as the lack of water may limit the recovery of vegetation struc ture. Our results contribute to a better understanding of variation in key structural vari ables of Chaco woodlands in relation to climate and land use. Fil: Ferraina, Antonella. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Clima y Agua; Argentina Fil: Baldi, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Matemática Aplicada de San Luis. Grupo de Estudios Ambientales; Argentina. Universidad Nacional de San Luis; Argentina Fil: Abelleyra, D. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Clima y Agua; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico y Tecnológico Patagonia Norte; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Verón, S. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Clima y Agua; Argentina

Los bosques del norte de la Patagonia tienen una larga historia de uso, siendo uno de los ecosistemas forestales más estudiados de Argentina. Sin embargo, existen pocos ejemplos de bosques nativos bajo manejo sustentable. Proponemos que esto se debe principalmente a la falta de voluntad de las autoridades de aplicación, organismos de gestión, investigadores y técnicos del sector por asistir a productores forestales en la implementación de la legislación vigente. Históricamente, los productores han sido ignorados por un sistema administrativo que no ha buscado adaptarse a sus necesidades, y por un sistema científico-tecnológico que no ha utilizado sus conocimientos empíricos para generar propuestas realistas de manejo. Consideramos que, si bien el manejo sustentable de los bosques patagónicos pareciera ser técnicamente viable, su implementación dependerá de la voluntad del sector público por generar las condiciones para un diálogo intersectorial que integre distintos tipos de saberes. The native forests of Northern Patagonia have a long history of human use, being one of the most studied ecosystems of Argentina. However, there are few examples of sustainably managed native forests. We propose that this is mainly due to the lack of political will from regional authorities, forest administration agencies, technicians and researchers in assisting forest owners to implement current legislation. Historically, forest owners have been ignored by an administrative system that has not considered their needs as well as by a scientific-technologic system that not used their empirical knowledge to develop realistic management packages. We consider that, even though the sustainable management of Patagonian native forests seems to be technically feasible, its implementation will depend on the will of the public sector to generate better conditions for an intersectoral collaboration that integrates different kinds of knowledge.

Rainforests (RF) and transitional forests (TF) of Argentinean north Patagonia develop under such different climatic conditions that key aspects of seasonal growth may be assumed to differ among the woody plants that characterize these forests. This study was aimed at evaluating primary growth dynamics in tree species typical of RF and TF. Two common-garden essays were performed in Bariloche, Argentina, one with RF species and the other with TF species. The times of extension initiation and end, the duration of the extension period and the relative and absolute extension rates (RER and AER, respectively) were registered for each species. The relation between AER and air temperature was compared between species. In general, RF species had less variable times of extension initiation, extension end and time of maximum RER, and longer-lasting extension than TF species. Among RF species, extension duration was the longest forCaldcluvia paniculata(26.9 weeks, on average) and the shortest forLuma apiculata(18.9 weeks). Among TF species, the longest and shortest extension durations corresponded, respectively, toDiostea juncea(18.2 weeks) andMaytenus boaria(13.0 weeks). The extension rates of RF species tended to be more related to temperature than those of TF species. This study provides some evidence that endogenous control of growth dynamics would be tighter in TF than in RF species; the former would be better adapted to more severe climatic conditions during the primary-growth period., Los bosques lluviosos (RF) y los bosques de transición (TF) de Patagonia Norte argentina, se desarrollan bajo condiciones climáticas contrastantes, por lo que puede esperarse que las especies leñosas que caracterizan estos dos tipos de bosque difieran en aspectos clave del crecimiento estacional. Este estudio tuvo como objetivo evaluar la dinámica de crecimiento primario de especies arbóreas típicas de RF y de TF, mediante dos ensayos en jardín común en Bariloche, Argentina. Para cada especie se registraron las fechas del inicio y fin, y duración del alargamiento. Se calcularon las tasas de alargamiento relativas (RER) y absolutas (AER), relacionando las últimas con la temperatura. En general, las especies de RF tuvieron momentos de inicio del alargamiento, fin de alargamiento y RER menos variables y períodos de alargamiento más largos que las de TF. Entre las especies de RF,Caldcluvia paniculatatuvo el período de alargamiento más largo yLuma apiculatael más corto (26,9 y 18,9 semanas, respectivamente). Entre las especies de TF,Diostea junceatuvo el período de alargamiento más largo yMaytenus boariael más corto (18,2 y 13,0 semanas, respectivamente). Las AER de las especies de RF estuvieron más relacionadas con la temperatura que las de TF. Este estudio aporta evidencia que sugiere que la dinámica de crecimiento en especies del TF está sujeta a mayor control endógeno que en especies de RF; las especies del TF estarían mejor adaptadas a condiciones climáticas más estrictas durante el período de crecimiento primario.

Key message: Intra-individual variations of plant responses to environmental conditions are related to axis differentiation. Plastic responses include variations in primary growth, shoot allometry, leaves’ chlorophyll content and water use efficiency. Abstract: Primary growth affects plant plasticity by influencing the number, spatial arrangement and time of differentiation of the leaves. For Nothofagus obliqua, we evaluated if primary shoot growth dynamics determines short-term responses to environmental conditions, and intra-individual variations in such responses. Before bud-break, saplings were located in experimental conditions, combining two light treatments with two water supply treatments. For each individual, morphology, relative extension rate (RER), and relative leaf chlorophyll content (SPAD units) were registered for the annual shoot derived from the most distal bud of two axis categories: the main axis (trunk) and a main branch. For trunk shoots, we analysed the net photosynthetic rate at saturating photosynthetic photon flux density (Psat) of proximal and distal leaves. Shaded trees had higher RER, longer and more slender shoots, longer internodes, and higher leaf chlorophyll content than unshaded trees. The number of nodes was affected by water condition in trunk shoots, and by light condition in main branch shoots. Full sunlight stimulated the development of a branch following the length and growth direction of its parent shoot (relay branch). Shade would have promoted the development of neoformed leaves. Under shade and low water availability, water use efficiency was higher in distal than proximal leaves. Under high sunlight and water availability, leaves of relay branches presented slightly higher Psat with higher water loss than both proximal preformed leaves and distal leaves under the other tested conditions. This study highlights the need of assessing intra-individual variations in shoot acclimation in relation to axis differentiation. Fil: Torres, Cristian Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional de Río Negro; Argentina Fil: Magnin, Noel Amaru. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional de Río Negro; Argentina Fil: Varela, Santiago Agustín. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Area de Recursos Naturales; Argentina Fil: Stecconi, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional de Río Negro; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnol.conicet - Patagonia Norte. Unidad de Adm.territorial; Argentina. Universidad Nacional del Comahue; Argentina Fil: Puntieri, Javier Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnol.conicet - Patagonia Norte. Unidad de Adm.territorial; Argentina

A close examination of axis differentiation is key to the understanding of plant architecture and its ecological consequences. The present study was aimed at evaluating the relationship between shoot size/structure and shoot growth dynamics in Luma apiculata (Myrtaceae), a widely distributed and cultivated but little investigated Andean-Patagonian woody species. We assessed (a) organ preformation in apical buds, (b) shoot growth through repeated observations of labeled axes, (c) axillary production, leaf area, stem volume, dry mass of leaves, stem and reproductive structures, and allometric relationships for annual shoots of different sizes. The number of preformed organs in apical buds of L. apiculata averages seven nodes and exhibits little variability, in contrast with the highly variable growth period (from few weeks up to more than six months) and the size reached by annual shoots. The leaf area/stem volume ratio increased more sharply during shoot extension in short than in long shoots. Stem thickness was proportionally higher than other shoot-size measures in short shoots and long shoots as compared to intermediate-size shoots. Both the presence and the position of branches along shoots varied notably with shoot size. Proportional mass and meristem allocation to fruit production decreased with shoot size. Unlike many other broadleaved temperate and temperate-cold tree species so far studied, the size reached by L. apiculata shoots developed in the same year varies notably among axes in the same topological position, and seems to depend largely on the expansion of non-preformed organs. A low dependency of shoot growth on organ preformation may increase plasticity in axis structure, at the cost of a less hierarchical (more shrubby) architecture. Simultaneous organ differentiation and expansion may allow plants to fine-tune shoot structure to the prevailing conditions during the growing season, and represent an advantage whenever conditions favourable for growth exhibit high between-year variations. Fil: Puntieri, Javier Guido. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Negro; Argentina Fil: Torres, Cristian Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Magnin, Noel Amaru. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Stecconi, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Desarrollamos un modelo de estados y transiciones (MEyT) para el bosque de ñire (Nothofagus antarctica) en el norte de la Patagonia, con el fin de sintetizar el conocimiento disperso sobre las repuestas de este sistema al manejo silvopastoril. En base a una recopilación bibliográfica, a un taller de expertos seguido por sesiones de consulta y a relevamientos de campo propusimos los estados alternativos e identificamos los disturbios naturales y las prácticas de manejo más comunes que disparan cambios entre estados. Definimos siete estados, 13 transiciones de degradación y cuatro de restauración. Los bosques más íntegros están dominados por ñire y caña (Chusquea culeou) y el estado más degradado lo componen estepas sub-arbustivas de cadillo (Acaena splendens). Los estados intermedios serían los más aptos para el uso silvopastoril (bosque abierto de ñire con caña y pastizal, y bosque de ñire con pastizal), pero tienen una alta inestabilidad con las prácticas de manejo actuales, ya que, a causa de dicho manejo, con el paso del tiempo perderían el componente arbóreo y la cobertura de caña. El pastoreo, la extracción forestal, los incendios y las especies invasoras son los principales factores que disparan las transiciones de degradación. Estos efectos están agravados por la competencia del componente herbáceo con la vegetación arbórea, la mortandad de árboles y de caña, y por la erosión del suelo. La reversión de las transiciones de degradación no se produce de forma natural en el horizonte productivo del predio (~40 años) y requiere del uso de tecnologías como plantación, protección de los plantines de árboles y desarbustado. La identificación de las fases de riesgo en cada estado permite contar con alertas tempranas de deterioro, visualizar los efectos del manejo y orientar las prácticas para mantener la composición y estructura del bosque dentro de los límites que contemplan los aspectos productivo y ambiental. We built a state-and-transition model (S&TM) for the ñire forest system under silvopastoral use in north-western Patagonia, with the aim to identify management effects on the vegetation. The model can help design practices that maintain the system within ‘desired' conditions in the long term. Based on a review of published and unpublished literature, an expert workshop and consultation, and field surveys we proposed alternative states and their response to natural disturbances and current management practices. We defined seven states, 13 degradation and four restoration transitions, and the factors and levels that trigger the transitions (i.e., grazing, frewood extraction, fire and/or dispersal of invasive plants). The best-conserved forest is dominated by ñire (Nothofagus antarctica) and cane (Chusquea couleou), while the most degraded state corresponds to sub-shrubby steppes dominated by Acaena splendens (cadillo). The intermediate states are likely to be the most suitable for silvopastoral use (open ñire and cane forest, and ñire forest with grassland) but are highly unstable. Therefore, with the common current practices, the tree component and cane cover are lost with time. Invasion of exotic species, competition with the herbaceous vegetation, mortality of trees and cane, and soil erosion are the processes that trigger transitions. Most degradation transitions are difficult to revert because they require high-cost practices and/or have a long recovery time. Building the S & TM brought together scattered information about long-term changes in the vegetation. The identification of risk phases enables early warning of degradation. Fil: Rusch, Verónica. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina Fil: López, Dardo Rubén. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuaria Manfredi. Estación Forestal Villa Dolores; Argentina Fil: Cavallero, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Rusch, Graciela M.. Norwegian Institute for Nature Research; Noruega Fil: Garibaldi, Lucas Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Rio Negro. Sede Andina; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Peri, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad Nacional de la Patagonia Austral; Argentina

Plant architecture and phenotypic plasticity under natural conditions remain little known for many rhizomatous species. This study evaluates, in situ, the plastic responses of Alstroemeria aurea plants from three Patagonian populations to flower or flowering-shoot removal. The size and architecture of treated and untreated plants were assessed. Nutrient contents (N, P and K) were evaluated for rhizomes and roots developed in two successive years. Those plants that were deprived of their inflorescences developed, on average, a heavier rhizome than both control plants and plants from which flowering shoots had been removed. Neither of the two treatments applied altered the number of metamers or the branching pattern of the rhizomes. The contents of N, P and K were higher in rhizomes than in roots. In summer, nutrients were more concentrated in inflorescences and the new rhizome segment than in the rhizome segment developed in the previous year. The idea that fruiting failure in A. aurea promotes resource re-assignment from aerial shoots to rhizomes without altering the architecture of plants is supported. The development of the underground portion of aerial shoots in late summer-autumn allows A. aurea plants to take full advantage of short growth periods, but would impose a limit to plasticity. Fil: Puntieri, Javier Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional de Rio Negro. Sede Andina; Argentina. Universidad Nacional del Comahue; Argentina Fil: Gatica, Nuria. Universidad Nacional del Comahue; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina

Previous studies on mature forests of NW Argentinean Patagonia indicated that N is the main growth-limiting nutrient in most dominant tree species, while P limitation is uncommon, despite the soils’ volcanic origin. This pattern was inferred from leaf N/P ratios and resorption proficiencies, but has not been experimentally tested. We conducted a greenhouse trial with seedlings of two deciduous species of high timber quality, Nothofagus nervosa and N. obliqua, and soils characteristic of each species. Seedlings were fertilized with three levels of N (100, 200 and 400 mg kg−1 soil) with or without the concurrent application of a single P dose (60 mg kg−1 soil) during their second growing season. Response variables were morphological descriptors of shoot and root growth, N and P concentrations in green and senescent leaves and ectomycorrhizal infection. Both species were primarily limited by N: the addition of N resulted in higher shoot and root masses, an increased number of nodes, taller stems and greater basal and root diameters, while no effect of P was found. N/P ratios in green leaves and N and P resorption proficiencies indicate that with increased N availability P can become a secondary-limiting nutrient for N. nervosa. This was accompanied by the maintenance of ectomycorrhizal infection and mass allocation to roots in this species. The steep growth response of N. obliqua to N addition may signal a strong competitive capacity of this species when growing in soils of high N availability. Fil: Agüero, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Puntieri, Javier Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Mazzarino, Maria Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Barroetaveña, Carolina. Centro de Investigación y Extensión Forestal Andino Patagónico; Argentina. Universidad Nacional de la Patagonia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Simple morphological traits are used to describe the architecture of a tree: the growth and branching process, the morphological differentiation of the axes and the position of reproductive structures. The main purpose of this contribution is to describe the growth architecture of the Jurassic conifer trees present at the most basal part of the La Matilde Formation in the locality of Monumento Natural Bosques Petrificados, Patagonia, Santa Cruz province, Argentina, and to compare it with that of extant and fossil conifers. This study is based on a large number of in situ petrified trunks, impressions and external molds of leafy branches and female cones in intimate association or organic connection with the trunks. The cones were assigned to Araucaria cf. A. mirabilis (Speg.) Windhausen emend. Calder (Araucariaceae) based on morphological and anatomical characters. The "Araucaria mirabilis" trees had 3 branching categories, corresponding to the typical pattern in extant Araucariaceae, although 4 branching categories cannot be completely discarded. The main, orthotropic stem (TA1) had rhythmic growth and branching, bearing 3-4, probably up to 6-7 plagiotropic branches in pseudowhorls. The lower part of the trees shows no branch-scars; therefore, self-pruning would have been present. Lateral branches (A2) had rhythmic branching: the branchlets (A3) were distributed regularly on the leading branch, with an alternate arrangement, conforming two orthostichies on the same horizontal plane. The female cones were borne terminal at the tip of peduncles, but lateral in position with respect to A2 branches. Reiteration patterns are present: total reiterations (bifurcated trunks and big, orthotropic branches in trunks with normal plagiotropic branches) and partial reiterations (epicormic branching) were observed. The root system consisted of 6 horizontal roots, no tap root was observed. Two architectural patterns or "morphotypes" were recognized at one of the forest levels studied, in keeping with other pieces of evidence (type of wood, foliage, and cones). The "Araucarioid morphotype or morphotype A" includes most of the studied specimens (i.e. "Araucaria mirabilis" trees); showing pseudowhorls of plagiotropic branches. These characters correspond to Massart's model, with certain modifications in the adult trees due to reiteration processes. Morphotype B was observed in bigger trunks with a distinctive costulated surface, which bear only orthotropic branches irregularly arranged, and without reiteration evidences; they could be assigned to Attim's model and possibly represent a different conifer taxon, though subrepresented. Partial and total reiteration patterns are described for the first time for Jurassic, Gondwanic conifers. Moreover, Massart's model can be followed from Upper Palaeozoic Walchiaceae to Mesozoic Araucariaceae. Fil: Falaschi, Paula. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Zamuner, Alba Berta. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Área Paleobotánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Foix, Nicolas. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Rivera, Stella M.. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina

Se estudió el desarrollo arquitectural en tres años de plántulas de Nothofagus obliqua bajo condiciones de vivero. Las plántulas derivaron de semillas de cinco procedencias dentro del área de distribución natural de esta especie en Argentina. En no menos de 40 plantas por procedencia se registraron: longitud, número de nudos y diámetro basal de los brotes anuales del eje vertical principal. El brote del primer año de todas las plántulas consistió en una sola unidad de alargamiento (UA), el del segundo año en una o dos UA y el del tercero en una, dos o tres UA. El desarrollo de dos o tres UA resultó invariablemente de la muerte del meristema apical luego de la primera UA. Las consecuencias más evidentes de la existencia de más de un evento de alargamiento en un año fueron: (a) mayores longitud y número de nudos en ese año, (b) mayor engrosamiento del tronco al nivel del suelo y (c) un período de alargamiento más largo. Plantas de diferente procedencia difirieron en la longitud del brote del primer año y en las proporciones de brotes de los años siguientes con una o varias UA.

International audience; The present study shows experimentally that primary growth of the native Patagonian Cupressaceae Austrocedrus chilensis (D. Don) Pic.-Serm et Bizz., Fitzroya cupressoides (Molina) I. M. Johnst. and Pilgerodendron uviferum (D. Don) Florin is potentially continuous. External morphological markers of interannual growth limits have been identified for the main axes of these species after several years of observation. Such limits correspond with axis portions in which internodes are relatively short and leaves have a small distal free end forming an acute angle with the axis. The causality of these results and their utility for studying the productivity, adaptation to different environments, population management and conservation of these threatened species are discussed.

There is evidence that Nothofagus nervosa (= N. alpina) is suitable for timber production in temperate regions due to its wood quality and fast growth. However, high intra-specific variability in the architectural traits of this species limits its usefulness. & Aims This study was aimed at evaluating intra-specific variability in the architecture of N. nervosa trees at the population level, with emphasis on traits related to the suitability of trees for timber production. & Methods The size of 13-year-old trees installed in an experimental field population and the extent of differentiation between trunk and branches were compared among families (trees derived from different mother trees). & Results The large majority of trees exhibited architectural features indicative of high suitability for timber production: clear differentiation between trunk and main branches and few occurrences of permanent trunk forks, apex deaths, and sylleptic branching. Trees belonging to different families differed in height and trunk diameter. Micro-environmental conditions had a very significant effect on most architectural traits, including the trunk differentiation. & Conclusions N. nervosa emerges as a suitable option for timber production in temperate regions. Trunk growth seems to be under both environmental and genetic control in this species. Fil: Puntieri, Javier Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional de Rio Negro; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina Fil: Tejera, Luis. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina Fil: Mondino, Víctor. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina Fil: Gallo, Leonardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina

The capacity of preformation and neoformation and the structure of winter buds are vegetative attributes that may vary between plant species and according to ontogenetic stages of the same species. The present study describes and evaluates these features for the four tree species of Proteaceae occurring in Patagonia. In particular, it analyzes the structure and development of the distal buds of the trunk and the preformed or neoformed nature of the organs involved. Two of the species, Embothrium coccineum and Lomatia hirsuta, have scaly buds, in which primordia of green leaves are covered by cataphylls. The shoots of both species may include neoformed organs, more frequently so in juvenile trees. Lomatia ferruginea and Gevuina avellana have naked buds with a low number of primordia; in juvenile and adult trees of both species trunk shoots are entirely preformed. The structure of buds and shoots suggests two different growth modalities of the axes, which would be related to ecological breadth (narrower in the species with naked buds than in those with scaly buds) and distribution area of these species. The considerable morphological differences between the two Lomatia species studied raise the question whether they ought to be included in the same genus. Fil: Magnin, Noel Amaru. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Grosfeld, Javier Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Barthélémy, Daniel. Institut National de la Recherche Agronomique; Francia Fil: Puntieri, Javier Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

A-07-19; International audience; In temperate trees, axis length growth generally results from the differentiation of organs at the end of a growing season and the extension of such "preformed organs" in the next growing season. Neoformation, i.e., the simultaneous differentiation and extension of organs, has been studied for only a few species. Here we evaluated bud composition and growth unit (GU) size for seedlings and saplings of Nothofagus alpina, a valuable South American forest tree. Trunk GUs of seedlings and saplings included preformed and neoformed organs, whereas main-branch GUs of saplings were entirely preformed. The size of a GU was more closely related to the number of preformed green leaves than to the number of cataphylls of its preceding bud. Proximal buds of a trunk GU had more cataphylls and less green-leaf primordia than distal buds. Individual leaf area increased from proximal to distal positions on trunk GUs. For trunk and main-branch GUs, the length/width ratio was maximum for leaves in intermediate positions. The development of large neoformed leaves at the end of the growing season could increase the photosynthetic capacity of this species in late summer, when the activity of preformed organs is likely to be decreasing.

International audience; Species distributed along wide environmental ranges are expected to be either plastic or adapted to local optima. The elucidation of which of these alternatives prevails, is crucial in planning breeding and conservation strategies for not yet domesticated species. Austrocedrus chilensis (Cupressaceae) is the most commercially important conifer of the temperate forests of Argentina and the target of a domestication program. A steep precipitation gradient characterizes its Argentinean range.* Variation within and differentiation among four natural populations of this Patagonian cypress representative of two contrasting precipitation regimes (>1300 and 330 mm per y) were assessed by analyzing several morpho/architectural traits in one-year-old seedlings grown in a greenhouse. * Progenies from one of the two xeric populations did not differ from those corresponding to both humid-site populations. The two most variable populations in terms of additive genetic variance belonged to contrasting precipitation regimes. Differentiation among populations was low as measured by each and every variable (average Qst = 0.088). Morphological traits related to the main axis size would have a dubious adaptive meaning.* The results suggest that the Patagonian cypress would have not evolved genetic pools adapted to local optima, and thus it appears to be a phenotypically plastic species, at least regarding growth at juvenile age.; Les espèces presentant de vastes aires de répartition avec des fortes variations de l'environnement sont soit plastiques, soit adaptées à des optima locaux. Identifier laquelle de ces deux alternatives est celle qui prévaut est une étape cruciale pour planifier des stratégies d'amélioration génétique ou de conservation d'espèces non encore domestiquées. Austrocedrus chilensis (Cupressaceae) est le conifère le plus important du point de vue commercial dans les forêts tempérées d'Argentine et fait l'object d'un programme de domestication. Un fort gradient de précipitations caractérise son aire de répartition en Argentine.* Les variations intra-population et la différenciation entre quatre populations naturelles représentatives de deux régimes contrastés de précipitations (>1300 mm et 330 mm par an) ont été évaluées en analysant plusieurs traits d'architecture et de morphologie sur des plants âgés de un an cultivés sous serre.* Les descendants de l'une des deux populations xériques ne différaient pas de ceux des deux populations de sites humides. Les deux populations avec la plus forte variance génétique additive provenaient de régimes contrastés de précipitation. La différenciation entre populations était faible tant pour chaque trait que pour l'ensemble des traits (Qst = 0.088). Les caractéristiques morphologiques liées à la taille de l'axe principal n'auraient donc que peu signification en termes d'adaptation.* Les résultats suggèrent que le cyprès de Patagonie n'aurait pas développé de pools génétiques adaptés aux optima locaux. Il semble être une espèce phénotypiquement plastique, au moins en ce qui concerne la croissance au stade juvénile.

† Background and Aims The distribution and differentiation times of flowers in monoecious wind-pollinated plants are fundamental for the understanding of their mating patterns and evolution. Two closely related South American Nothofagus species were compared with regard to the differentiation times and positions of sta- minate and pistillate flowers along their parent growth units (GUs) by quantitative means. † Methods Two samples of GUs that had extended in the 2004-2005 growing season were taken in 2005 and 2006 from trees in the Lanin National Park, Patagonia, Argentina. For the first sample, axillary buds of the parent GUs were dissected and the leaf, bud and flower primordia of these buds were identified. The second sample included all branches derived from the parent GUs in the 2005-2006 growing season. † Key Results Both species developed flowering GUs with staminate and/or pistillate flowers; GUs with both flower types were the most common. The position of staminate flowers along GUs was similar between species and close to the proximal end of the GUs. Pistillate flowers were developed more distally along the GUs in N. alpina than in N. obliqua .I nN. alpina, the nodes bearing staminate and pistillate flowers were sep- arated by one to several nodes with axillary buds, something not observed in N. obliqua. Markovian models sup- ported this between-species difference. Flowering GUs, including all of their leaves and flowers were entirely preformed in the winter buds. † Conclusions Staminate and pistillate flowers of N. alpina and N. obliqua are differentiated at precise locations on GUs in the growing season preceding that of their antheses. The differences between N. alpina and N. obliqua (and other South American Nothofagus species) regarding flower distribution might relate to the time of anthesis of each flower type and, in turn, to the probabilities of self-pollination at the GU level.

International audience; Shoot growth and dieback were compared among progenies of nursery-grown seedlings of Nothofagus obliqua belonging to seven progenies of the same provenance (Quila-Quina, Argentina). First-year shoots consisted of one growth unit (GU) and second-year shoots of one or two GUs. The probability of development of two GU was similar for all progenies. Progenies were different in terms of shoot size, terminal bud abscission, the extent of shoot dieback after shoot extension and the node of origin of the relay shoot on the first shoot. Plants with a second-year shoot consisting of two GUs had a thicker stem and more nodes than those with single-GU shoots. The selection of N. obliqua seed trees based on architectural traits suitable for forestry development at specific sites must contemplate variability among progenies and their probabilities of successful development under different conditions.

The effects of artificial damage on the branching pattern were studied for a natural population of Nothofagus dombeyi trees. In four independent experiments, leaves, buds, distal internodes and/or nodes were clipped from main-branch shoots. The sizes of shoots close to the site of damage were compared with those of control shoots. None of the treatments induced the outbreak of dormant proventitious buds or adventitious buds. Organ clipping from shoots in winter or early spring resulted in moderate increases in the growth of shoots close to the site of damage. The removal of a distal shoot in late spring caused an increase in the growth of a neighbour shoot. The size of the largest shoot relative to that of the other shoots developed on the same parent shoot seems to depend on the tree concerned., Effets de facteurs traumatiques sur le mode de ramification de Nothofagus dombeyi (Nothofagaceae). Les effets de traumatismes artificiels sur le processus de ramification ont été étudiés sur une population naturelle d'arbres de Nothofagus dombeyi. Dans quatre experimentations indépendantes, l'apex de l'axe, les feuilles et/ou les bourgeons axillaires de pousses annuelles sur des rameaux principaux ont été coupés et la modalité de ramification des pousses traitées comparée avec celle de pousses témoins. Aucun des traitements appliqués n'a induit le débourrement de bourgeons proventifs dormants ou adventifs. Le prélèvement d'organes pendant l'hiver ou le débourrement printanier n'a stimulé qu'une augmentation modérée de la taille des pousses les plus proches du site de traumatisme. Le sectionnement de l'apex d'une pousse à la fin du printemps induit l'augmentation de la taille d'une pousse voisine. Un effet " arbre " est mis en évidence dans la taille de la pousse la plus grande relativement à la taille des autres pousses développées sur la même pousse d'origine.

En regard des controverses bibliographiques au sujet de l'état dioïque ou monoïque de #Fitzroya cupressoides# et #Pilgerodendron uviferum#, l'objectif de ce travail est de déterminer la distribution des organes reproducteurs chez ces deux espèces. L'étude se situe à l'ouest du parc national nahuel Huapi au nord-ouest de la Patagonie (Argentine). Pendant trois années et pour chaque espèce, cent individus ont été suivis en notant la nature et la position des organes reproducteurs dans la cime des arbres. Les résultats de cette étude montrent que ces deux espèces sont dioïques. Cette caractéristique a été confirmée sur de nombreux individus en Argentine et au Chili.