Search

The tree reproductive phenology in the seasonal neotropical forest is driven by many abiotic and biotic factors and provides information to understand the biological processes of ecosystems. The Yungas Piedmont Forest in Argentina is one of the areas with the greatest biodiversity and timber resources in the country. However, limited knowledge of the reproductive phenology of these species has resulted in inadequate management plans and protocols. In this study, we observed the reproductive phenology of eight timber tree species in the Yungas Piedmont Forest over a two-year period and evaluated the relationship between local climatic conditions (temperature, precipitation, and photoperiod) and reproductive phenology. In the Yungas Piedmont forest, the reproductive phenology of timber tree species presented intermediate intensity, and short duration. The reproductive phenology of each species was seasonal and mainly modulated by photoperiod. Concerning the timing of each phenophase, we found interspecific variation in reproductive phenological strategies. Flowering occurred mainly during the late dry season up to early wet season and fruiting had two annual intensity peaks, one per season. This study provides valuable information on the phenological patterns of economically important tree species in the Andean Forest, and it is essential for underpinning conservation and restoration actions in the Yungas forests. [ABSTRACT FROM AUTHOR]

Copyright of Investigación Agraria is the property of Investigacion Agraria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introducción y objetivos: Ligustrum sinense (ligustrina) es una reconocida especie exótica invasora. El objetivo de este trabajo fue estudiar los rasgos fisiológicos y anatómicos foliares de renovales de ligustrina que podrían otorgarle ventajas para su establecimiento en un ambiente de sotobosque de la selva de Yungas. M&M: Este estudio se realizó en el Parque Nacional Aconquija (Tucumán, Argentina). Se evaluaron los rasgos morfo-anatómicas foliares y fisiológicos en un ambiente de sotobosque durante primavera-verano e invierno. Se analizaron las características anatómicas de la lámina foliar y variables fisiológicas relacionadas al intercambio de gases. Además, se calculó el área foliar específica, densidad de hojas, contenido de nitrógeno foliar y eficiencia fotosintética en el uso del nitrógeno foliar. Resultados: Durante primavera-verano L. sinense muestra una mayor eficiencia fotosintética en el uso del nitrógeno foliar y una mayor asimilación fotosintética en condiciones saturantes. La eficiencia de carboxilación, eficiencia intrínseca del uso del agua y espesor de hoja fueron 26%, 34% y 41% mayores en invierno con relación a primavera-verano. Durante el invierno se registró un aumento en el espesor de la lámina lo que contribuiría a mejorar el intercambio de CO2 en época de condiciones subóptimas para la fotosíntesis. Conclusiones: La ligustrina fotosintetiza todo el año y su éxito para establecerse en el sotobosque de la selva de Yungas podría explicarse en parte por las estrategias morfo-anatómicas y fisiológicas desplegadas.

Se analizó la variación temporal de biomasa en un remanente del bosque atlántico del Alto Paraná en Paraguay, haciendo énfasis en la dinámica forestal y las clases diamétricas. Se estimó la biomasa total de los árboles con DAP ≥ 10 cm, en una parcela permanente de 1 ha ubicada en la Reserva Natural Tati Yupi de Itaipú Binacional, empleando datos de mediciones de los años 1995, 2002, 2005, 2008, 2011 y 2016. En 21 años hubo un aumento de biomasa de 0.82 Mg.ha-1.año-1; sin embargo, la variación no fue uniforme entre las mediciones. En los periodos 1995-2002 y 2002-2005 se presentó reducción de biomasa de 4.28 y 0.81 Mg.ha-1.año-1, principalmente debido a la elevada mortandad de los árboles. Mientras que en los lapsos de 2005-2008, 2008-2011 y 2011-2016 hubo aumento de 6.00, 2.97 y 4.53 Mg.ha-1.año-1, respectivamente. La variación fue más notable en las clases diamétricas inferiores.

The temporal variation of the tree biomass was analyzed in a remaining Upper Parana Atlantic Forest in Paraguay, focusing on forest dynamics and diameter classes. The total biomass of all individuals with DBH = 10 cm was estimated in a permanent plot of 1 ha located in the Tati Yupi Nature Reserve of Itaipu Binacional, using measurement data from 1995, 2002, 2005, 2008, 2011 and 2016. In 21 years, the biomass increased by 0.82 Mg.ha-1. year-1; however the variation was not uniform between measurements. In the period 1995 - 2002 and 2002 - 2005, there was a reduction in total biomass of 4.28 and 0.81 Mg.ha-1.year-1, mainly due to high tree mortality. While in the period 2005 - 2008, 2008 - 2011 and 2011 - 2016, there was an increase in biomass of 6.00, 2.97 and 4.53 Mg.ha-1.year-1, respectively. The variation was more visible in lower diameter classes. [ABSTRACT FROM AUTHOR]

La fenología foliar responde de manera sensible a distintas señales ambientales. La coordinación entre las fases fenológicas y estas señales le permite a las especies ajustar el momento óptimo para expandir sus hojas y crecer, así como para evitar los posibles daños que causan las condiciones ambientales desfavorables. Por otro lado, en las especies deciduas, la altura de los árboles es otro factor clave, ya que los eventos de expansión y caída de las hojas de los individuos del dosel determinan la disponibilidad de luz para los de menor altura. El objetivo de nuestro trabajo fue conocer de qué manera los factores ambientales interactúan con la fenología foliar en especies arbóreas de diferente hábito foliar que coexisten en el extremo sur del Bosque Atlántico semideciduo. Para esto se monitoreó la fenología foliar de 10 especies arbóreas típicas del dosel del Bosque Atlántico semideciduo en la provincia de Misiones. En las especies deciduas y brevideciduas se identificaron patrones estacionales en las fases de expansión y caída de hojas, vinculados con las variaciones en las temperaturas y el fotoperíodo. En las siempreverdes, en cambio, no se encontró una asociación clara. Los árboles deciduos no dominantes adelantaron la expansión de hojas en comparación con los dominantes. Esto implicaría una estrategia para optimizar la captura de luz y la ganancia de carbono al inicio de la primavera extendiendo la estación de crecimiento. La fenología de las especies deciduas se acopló de forma estrecha a las variables ambientales, lo cual podría generar, en estas especies, mayor vulnerabilidad ante eventos extremos de estrés ambiental, como las bajas temperaturas y el déficit hídrico.

Leaf phenology responds sensitively to different environmental signals. Coordination between phenological phases and these signals allow species to adjust the optimal time for leaf expansion and growth, and to avoid possible damage caused by unfavorable environmental conditions. On the other hand, in deciduous species, tree height is another important factor, since the expansion and leafless events of canopy individuals determine the availability of light in lower heights. The objective of our work was to assess how environmental factors interact with leaf phenology in tree species of different leaf habits that coexist in the southern end of the semi-deciduous Atlantic Forest. For this purpose, the leaf phenology of 10 typical tree species of the canopy of the semi-deciduous Atlantic Forest in the province of Misiones was monitored. In deciduous and brevideciduous species, seasonal patterns were identified in the expansion and leafless phases linked to variations in temperature and photoperiod. In the evergreens, on the other hand, no clear association was found. The non-dominant deciduous trees advanced the expansion of leaves in comparison with the dominant ones. This would imply a strategy to optimize the capture of light and the gain of carbon at the beginning of the spring extending the season of growth. The phenology of deciduous species was closely coupled to environmental variables, which could generate, in these species, greater vulnerability to extreme events of environmental stress, such as low temperatures and water deficit. [ABSTRACT FROM AUTHOR]

En todo el mundo, las invasiones de especies leñosas exóticas están amenazando las funciones ecosistémicas. La dispersión y el subsecuente reemplazo de bosques de especies nativas por comunidades dominadas por exóticas es evidente, particularmente, en proximidad a centros urbanos donde la presión de propágulos de especies exóticas es alta. Sin embargo, existe una falta de información sobre los factores ambientales que subyacen este reemplazo. En este estudio nos propusimos responder las siguientes preguntas: (1) ¿se observa una segregación espacial a escala local entre especies leñosas exóticas y/o nativas dominantes?, y (2) si existe esa segregación, ¿está asociada a variables ambientales? En el 2010 se establecieron 31 parcelas distribuidas en 16 laderas en los bosques Chaqueños de las Sierras de Córdoba, en Argentina central. En cada uno de los sitios de muestreo se relevó la composición y abundancia de todas las especies leñosas con un diámetro a la altura de la base superior a 5cm. Para caracterizar el ambiente en cada una de las parcelas medimos la posición topográfica (pendiente y orientación) y algunas propiedades asociadas con la física (densidad aparente y compactación), estructura (profundidad y textura) y con la química (pH y el contenido de nutrientes y agua) del suelo. A través, de un análisis jerárquico de agrupamiento, se identificaron cinco comunidades de leñosas coexistiendo: (1) Bosques dominados por Ligustrum lucidum, (2) Bosques mixtos dominados por Lithraea molleoides y Celtis australis, (3) Matorrales de Condalia buxifolia, (4) Matorrales de Cotoneaster glaucophyllus, y (5) Pajonales con emergentes de Pyracantha angustifolia. Estas comunidades se asociaron diferencialmente a las variables topográficas y edáficas locales. La segregación ambiental observada sugiere que las especies invasoras tienen una capacidad potencial para colonizar casi todos los ambientes en el área de estudio (variando la identidad de la invasora). En conjunto, los patrones descritos, aunque circunscriptos a un área de Chaco Serrano con un avanzado grado de invasión, plantearían un escenario de posible expansión de las leñosas exóticas sobre las comunidades nativas.

We describe a new species of climbing rat of the genusRhipidomysbased on cranial and external morphology, morphometrics, and phylogenetic analyses of cytochromebgene. This taxon was compared with species ofRhipidomyspresent in Ecuador, principallyR. latimanus, which is a closely related species based on molecular analysis, and with several species from Colombia and Peru. The new species is easily distinguished from congeneric species by the relatively small size of its body (average head–body length 123 mm) and its distinctive cranial morphology including: Interorbital region constricted; postorbital crest almost imperceptible in females and evident only slightly in males; braincase wide and round; nasals narrow in their posterior and gradually expand forward; anteromedian flexus is well defined and deep; m3 with hypoflexid large and deep; mesopterygoid fossa extends beyond the third molar and capsular process on mandible well developed, forming an evident projection. The new species is only known from the southeastern portion of Sangay National Park in Ecuador and is therefore likely endemic to the Cordillera Oriental of Ecuador. We also provide natural history and reproductive observations, vocalization analysis, habitat preference, and phylogenetic placement of this species. [ABSTRACT FROM AUTHOR]

Many forest bird species require tree cavities for nesting, and share this resource with a diverse community of animals. When cavities are limited, niche overlap can result in interspecific competition, with negative consequences for threatened populations. Vinaceous-breasted Parrots {Amazona vinacea) are endangered cavity nesters endemic to the subtropical Atlantic Forest, where cavities are scarce. We examined nest niche overlap among Vinaceous-breasted Parrots and 9 potential competitors (birds and mammals >140 g, and social insects) in Argentina, considering (1) timing of breeding, (2) characteristics of cavities (depth, entrance diameter, height), trees (diameter at breast height [DBH], species, condition), and habitat (surrounding land use, distance to edge), and (3) interspecific cavity reuse. During 10 breeding seasons we studied nests and roosts, measured their characteristics, and monitored cavities to detect reuse. We used multinomial logistic regression to determine whether the 6 most abundant taxa differed in nest and roost site characteristics. Timing of breeding overlapped for all bird species except the White-eyed Parakeet (Psittacara leucophthalmus). No combination of cavity, tree, and habitat characteristics predicted the taxa that utilized cavities. Moreover, 8 of the 10 taxa reused cavities interspecifically. The high level of overlap in realized nest niche, combined with previous evidence that cavities could limit bird density in our study area, suggest the possibility of interspecific competition for cavities among multiple taxa. Although models did not perform well at classifying cavities by taxon, some characteristics of cavities, trees, and habitat were selected more by Vinaceous-breasted Parrots than by other taxa, and we recommend targeting conservation efforts toward cavities and trees with these characteristics (7-40 cm entrance diameter, >10 m high, DBH >55 cm). We found 62% of Vinaceous-breasted Parrot nests on farms (vs. <50% for other taxa), highlighting the importance of working with local farmers to conserve cavities in anthropogenic habitats as well as in protected areas. [ABSTRACT FROM AUTHOR]

Invasions by exotic woody species are threatening ecosystem functions worldwide. The spread and subsequent replacement of native forest by exotic dominated stands is particularly evident nearby urban centers were exotic propagule pressure is highest. Yet, there is a lack of information on the environmental factors that underlie these replacements. In this study we addressed the following questions: (1) is there a local spatial segregation between the dominant native and exotic woody species? and (2) if this local segregation does exist, is it driven by environmental features?. For this, in 2010 we established 31 plots distributed along 16 sampling sites where we surveyed the composition and abundance of all woody species with a basal diameter ≥ 5cm. To characterize the environment of each plot, we measured the topographic position (slope, exposure) and different properties such as soil physics (bulk density, soil impedance), structure (soil deep, texture) and chemical characteristics (pH, nutrient and water content). Through a cluster analysis we were able to identify five different woody communities in coexistence: (1) Woodlands dominated by the exotic Ligustrum lucidum; (2) Mixed woodlands dominated by the native Lithraea molleoides and the exotic Celtis australis; (3) Scrublands dominated by the native Condalia buxifolia; (4) Scrublands dominated by the exotic Cotoneaster glaucophyllus, and (5) Scrubby grasslands with the exotic Pyracantha angustifolia. These communities were all associated with different local topographic and edaphic features. The environmental segregation among the identified communities suggests that woody invaders have the potential to colonize almost all the environments of the study site (though varying in the identity of the dominant exotic species). The observed patterns, even being restricted to a single well invaded area of mountain Chaco, may posit the spread of woody invaders towards native communities in the region. [ABSTRACT FROM AUTHOR]