Crecimiento de renuevos y expansión de copas en claros del dosel de bosques de Nothofagus pumilio (lenga) en Chubut, Patagonia, Argentina

In the province of Chubut in Patagonia, Argentina, Nothofagus pumilio forests (locally known as lenga), are managed through selective cuts, which imply the opening of canopy gaps. This management scheme is carried out without taking into consideration the sapling requirements changes through neither a cutting cycle nor the precipitation gradient in which these forests thrive. To analyze these changes, we inferred the facilitation-competition balance between the canopy and regeneration studying the effects of precipitation levels, gap size and gap age on saplings growth in height on 45 canopy gaps artificially created between 1960 and 1993. Results shown that during the first 20 years since the gap opening, the regeneration growth is determined by light availability in mesic sites and by water availability in dry sites. However, the difference due to the precipitation levels gradually decreases over time. Moreover, in the period between 20 and 35 years after gap opening, in both mesic and xeric sites, light is the limiting factor to growth. This means that in xeric sites, saplings shift from a water-dependent to a light-dependent growth. The average closing rate of gaps due to lateral growth of trees bordering the gap is high enough so that within the proposed gap size range, the gap healing can occur before regeneration reaches the upper stratum. Consequently, in mesic sites the gap opening can be done by a single operation that generates gaps with diameters of approximately twice the average height of the canopy (D/H). While in xeric environments, lenga seedling establishment and initial growth require the cover of small gaps, but advanced regeneration requires bigger gaps to reach the canopy. For this reason, gaps should be opened in two stages: the first gaps should be opened with a D/H between 0.8 and 1, and after a cutting cycle of 35 years, these openings should be enlarged to a D/H between 1.5 and 2. The close relationship is maintained between the new cohort and the upper strata require special considerations regarding the evolution of the balance between positive and negative interactions during development. Our work highlights the need to adjust management practices to these spatial and temporal variations so as to achieve an optimal growth along the entire production cycle.En la provincia del Chubut, Patagonia Argentina, los bosques de Nothofagus pumilio (lenga) son manejados mediante cortas de selección, que implican la apertura de claros en el dosel. Este esquema de manejo es implementado sin tener en cuenta los requerimientos de los renuevos a lo largo de todo el ciclo de cortas ni el gradiente de precipitaciones presente en su distribución. Para analizar estos aspectos estimamos el balance facilitación-competencia entre el dosel y la regeneración, considerando los efectos de los niveles de precipitación, el tamaño de los claros y la antigüedad de los mismos, en 45 claros creados artificialmente entre los años 1960 y 1993. Los resultados muestran que durante los primeros 20 años desde la apertura del claro, el crecimiento de la regeneración está determinado por la disponibilidad de luz en los sitios mésicos y por la disponibilidad de agua en los sitios xéricos. Sin embargo, la diferencias entre los distintos niveles de precipitación decrece gradualmente a lo largo del tiempo y entre los 20 a 35 años luego de la apertura de los claros, tanto en los sitios mésicos como xéricos el factor limitante es la luz. Esto implica que en los sitios xéricos el crecimiento de los renuevos pasa de ser dependiente del agua a dependiente de la luz. Por otro lado, la tasa de cierre de los claros debida al crecimiento lateral de la copa de los árboles límite es lo suficientemente grande como para que pueda ocurrir el cierre antes de que los renuevos alcancen el estrato superior. Por lo tanto, en los sitios mésicos la apertura de los claros puede realizarse en una única operación que genere claros con un diámetro de aproximadamente el doble de la altura dominante del bosque (D/H ≈ 2). Por el contrario, en los sitios xéricos, el establecimiento y crecimiento inicial de los renuevos requiere la apertura de claros pequeños (D/H entre 0,8 y 1) que luego deberán ser ampliados para maximizar el crecimiento avanzado (D/H entre 1,5 y 2). La estrecha relación entre la regeneración y el dosel del bosque requiere la consideración de los posibles cambios en el balance entre los apsectos positivos y negativos de la misma a lo largo de todo su desarrollo. Nuestro trabajo resalta la necesidad de ajustar las prácticas de manejo a estas variaciones espaciales y temporales para alcanzar un desarrollo óptimo a lo largo del todo el ciclo productivo

Distance to flood meadows as a predictor of use of Nothofagus pumilio forest by livestock and resulting impact, in Patagonia, Argentina

Seedling browsing by livestock has been indicated as major threat for forest sustainability use. Nothofagus pumilio forests are part of the livestock raising system in Patagonia, but because of the sparse understory cover, livestock graze mainly on flood meadows within the forest matrix. The complexity of the environment under study (forests and flood meadows) means that an adaptive predictor is needed to evaluate the intensity of resource use by livestock in order to assess its effect on the forest. Distance to flood meadows was evaluated as a predictor of the use intensity of the forest by livestock and its effect on the understory. The study was conducted at three sites in Chubut Province, Patagonia-Argentina. We established transects in the forest 320 m long, starting at the edge flood meadow-forest. In these transects, the livestock presence indicators (soil compaction, density of feces and trails) and composition of the understory were evaluated. Generalized Linear Model for repeated measures for longitudinal data were used. The indicators showed that distance is efficient for estimating forest use intensity by livestock. The understory varied with distance, the cover of exotic herbaceous was higher near the flood meadow. Far from the flood meadow, the cover was entirely composited of native species. The results support the use of distance to flood meadows as a tool for decision making in livestock and forest management in N. pumilio forests, and for further research on livestock effect on the forest.Fil: Quinteros, Claudia Pamela. Centro de Investigación y Extensión Forestal Andino Patagónico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lopez Bernal, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Centro de Investigación y Extensión Forestal Andino Patagónico; ArgentinaFil: Gobbi, Miriam E.. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bava, Jose Omar. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Centro de Investigación y Extensión Forestal Andino Patagónico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

A radio continuum survey of the southern sky at 1420 MHz. Observations and data reduction

We describe the equipment, observational method and reduction procedure of an absolutely calibrated radio continuum survey of the South Celestial Hemisphere at a frequency of 1420 MHz. These observations cover the area 0h < R.A. < 24h for declinations less than -10 degree. The sensitivity is about 50 mK T_B (full beam brightness) and the angular resolution (HPBW) is 35.4', which matches the existing northern sky survey at the same frequency.Comment: 9 pages with 9 figures, A&A, in pres

Polarímetro para observaciones en el continuo en 1420 MHz

Se describe el cabezal de un nuevo receptor capaz de detectar señales polarizadas, cuya construcción se está llevando a cabo en el Instituto Argentino de Radioastronomía. Se mencionan los criterios de diseño aplicados en las siguientes etapas del sistema como así también el estado actual de los trabajos.Asociación Argentina de Astronomí

Cabezal del receptor del continuo con dos polarizaciones

Se describe el cabezal del nuevo receptor del IAR para observaciones del continuo con dos polarizaciones. El proyecto incluye el diseño de un alimentador de tipo escalar, sistemas para la obtención de las dos polarizaciones, osciladores de alta frecuencia, amplificadores de bajo ruido y etapas de frecuencia intermedia.Asociación Argentina de Astronomí

Tecnologia social: uma estratégia para o desenvolvimento

Esta publicação apresenta reflexões de diversos representantes de instituições governamentais, do terceiro setor, da sociedade civil e de universidades sobre o tema da Tecnologia Social

Effects of feed delivery frequency in different environmental conditions on time budget of lactating dairy cows

This study aimed to examine the influence of feed delivery frequency and environmental conditions on daily time budget of lactating dairy cows. The study was carried out in two commercial dairy farms with Holstein herds. Fifty lactating dairy cows milked in automatic milking units (AMS farm) and 96 primiparous lactating dairy cows milked in a conventional milking parlour (conventional farm) were exposed to different frequencies of feed delivery replicated in different periods of the year (warm and mild) that were characterized by different temperature-humidity indices (THI). On each farm, feeding treatments consisted of two different feed delivery frequencies (1 7 and 2 7 on the AMS farm; 2 7 and 3 7 on the conventional farm). All behaviours of the cows were monitored for the last 8 d of each treatment period using continuous video recording. The two data sets from different farm systems were considered separately for analysis. On both farms, environmental conditions expressed as THI affected time budgets and the pattern of the behavioural indices throughout the day. The variation in the frequency of feed delivery seems to affect the cow's time budget only in a limited way. Standing time of cows on the conventional farm and the time spent by cows in the milking waiting area on the AMS farm both increased in response to increased feeding frequency. Although feed delivery frequency showed limited influence on cow's time budget, the effect on standing time could be carefully considered, especially on farms equipped with AMS where the type of cow traffic system (e.g., milking first) might amplify the negative consequences of more frequent feed delivery. Further investigations are required to evaluate the effect of THI and feed delivery frequency on other aspects of behavioural activity

Variazioni stagionali di indicatori di benessere in allevamenti lombardi di bovine da latte in aree di pianura, collinari e pedemontane

One of the main priorities of the agricultural EU policies is to set up valid, reliable and feasible indicators for on-farm welfare assessment. The EU Welfare Quality\uae project has developed a set of valid and feasible indicators, that have also been tested for inter-observer repeatability. For those indicators, repeatability between different times of survey has already been tested, but always within limited time spans; therefore, we have no information about their long-term repeatability, e.g. in extremely different seasonal conditions. We can hypothesize that more or less marked seasonal variations can occur, depending on farms\u2019 geographical location. In order to verify this hypothesis, we collected some welfare indicators, derived from the Welfare Quality\uae protocol, in 22 dairy farms located in plain, hilly and piedmont areas in Lumbardy, both in summer and in winter. No differences between seasons were found for presence of hairless patch areas, lameness, avoidance distance at the feeding rack (used to evaluate human-animal relationship) and for the other behavioural indicators. The percentage of cow that are too lean was higher in winter, especially in piedmont farms, where the climate is more severe. In fact, a long cold period, with rain, snow and wind, may cause an increase of energy consumption that, in turn, can make cows loose weight. The percentage of cows with diarrhoea was higher in winter, probably due to a reduction of digestion efficiency, induced by low environmental temperatures, that increased the sensibility of cows to enteric pathologies. We may conclude that the geographic location of the farms affected the repeatability of some welfare indicators in different seasons. The present study was carried out in the frame of the EULAT project, supported by Lumbardy Region, and that aims at the valorization of an excellent production chain \u2013 in terms of environmental sustainability, animal welfare and nutritional quality for the production of milk and dairy products

Effects of feeding frequency and environmental conditions on dry matter intake, milk yield and behaviour of dairy cows milked in conventional or automatic milking systems

The aim of the study was to investigate the effect of feeding frequency on milk production, dry matter intake (DMI) and cow behaviour on two dairy farms with conventional and automatic milking systems (AMS) in different environmental conditions. Cows on two farms were monitored. On the first farm, 96 primiparous cows were milked in a herringbone parlor while on the second a group of nearly 50 cows were milked in two AMS with a forced traffic. On each farm, treatments consisted of two different frequencies of total mixed ration (TMR) delivery (2 vs 3 on the conventional farm; 1 vs 2 on the AMS farm) replicated in two different periods of the year with THI of 72.6 and 60.7, respectively. The behaviour of the cows was monitored by continuous video recording. Statistical analysis was performed separately for the two farms. Increasing the frequency of TMR deliveries did not result in any variation in DMI but significantly improved milk yield on both farms. The increase in feeding frequency at the bunk in the AMS farm mitigated the negative effect of hot conditions on production with a 7.6% increase in milk yield. Feeding frequency did not influence cow behaviour on either farm. Hot conditions showed a depressive effect on DMI (nearly 8% on both farms) compared with thermoneutral conditions but caused a reduction in milk yield (an average 17%) only on the farm with multiparous high-producing cows milked automatically. In the hot period, cows on both farms showed a reduction in daily lying time and an increase in daily standing time