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Copyright of Boletín de la Sociedad Argentina de Botánica is the property of Sociedad Argentina de Botanica 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.)

Copyright of Biotropica is the property of Wiley-Blackwell 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.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing 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.)

Questions: It is well documented that invasive alien plants can reduce species richness and diversity and modify the composition of invaded communities. However, our knowledge on the impacts of invasive alien plants on the community functional structure and ecosystem properties and the mechanisms underlying these changes is more limited. We evaluated how the community functional structure and ecosystem properties change along a gradient of Ligustrum lucidum abundance. Location: Subtropical mountain forest in NW Argentina. Methods: We conducted tree vegetation sampling in 164 plots distributed along a gradient of L. lucidum abundance. For L. lucidum and for the most abundant tree species in these plots we estimated six functional traits (specific leaf area, leaf tensile strength, leaf nitrogen concentration, leaf water potential, wood density and maximum plant height), as well as their relative growth rates. Then, we calculated indices of community functional structure (community‐weighted means for each trait; richness, evenness, divergence and dispersion). We explored the extent to which the invasive success of L. lucidum and its impact may be attributed to niche differentiation or to fitness superiority. Finally, we explored how L. lucidum abundance alters ecosystem properties. Results: Some indicators of community functional structure changed linearly while others tended to saturate along the invasion gradient. L. lucidum has a higher growth rate than resident species and it lays close to the periphery, but within the limits of the functional space defined by resident trees. L. lucidum tends to displace more functionally similar resident species. Soil moisture and N content declined, while soil C:N increased with L. lucidum abundance. Conclusions: Our findings suggest that both niche differentiation and fitness superiority contribute to explain the invasion success of L. lucidum and the changes in functional structure of the community along the gradient of L. lucidum abundance with evident impacts on ecosystem properties. [ABSTRACT FROM AUTHOR]

Copyright of Montes is the property of Colegio y Asociación de Ingenieros de Montes 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.)

El vasto territorio del Chaco Seco y el Espinal se consolida como uno de los centros globales de producción de granos y carne. Tanto por distintas normas legales y limitaciones productivas, como por causas culturales, el bosque nativo se preserva en grandes porciones y numerosos pequeños fragmentos inmersos en la matriz agrícola. Estos remanentes suelen pasar desapercibidos para la comunidad científica y para los tomadores de decisiones, y quedan al margen de la planificación territorial y de acciones de conservación. En este trabajo describimos la estructura espacial de los remanentes y generamos un esquema de clasificación que permite identificar distintos tipos según sus propiedades espaciales. Por medio de una estrategia de clasificación basada en objetos, cartografiamos -22000 remanentes en ocho áreas focales (AF) dispersas en el territorio, para lo cual usamos imágenes satelitales CBERS-2B. Mediante índices espaciales, estos remanentes de tamaños, formas y niveles de aislamiento variables fueron categorizados en cinco clases, desde 'isletas' hasta 'bloques compactos'. La superficie de remanentes resultó mayor en el Chaco Seco que en el Espinal (entre 10.1% y 19.4% en la primera región, y entre 3.1% y 7.3% en la segunda). Las diferencias en el nivel de fragmentación se amplificaron entre AF, dependiendo tanto de la superficie total de remanentes como de la ocurrencia relativa de distintos tipos. Así, en el AF de San Luis, la fragmentación resultó 70 veces superior a la del AF de Anta (Salta). En este trabajo brindamos herramientas para identificar y monitorear estos remanentes; estas herramientas podrán ser consideradas tanto con fines productivos como de conservación. Finalmente, las acciones de manejo y conservación deben reconocer la existencia de estos fragmentos de bosques en paisajes muy transformados por la actividad agropecuaria. [ABSTRACT FROM AUTHOR]

Highlights • Linear fragments are native dry forest with potential to provide ecosystem services. • Pollination to soybean was study near and far from linear forest fragments (LFFs). • The open pollination treatment increased pods, seeds and yields by more than 30%. • The proximity to LFFs was not directly related to a larger difference in production. Abstract The delivery of ecosystem services, such as biotic pollination is a benefit that nature provides us. Pollinators increase the quantity, quality and stability of crops for food production. Previous works show that proximity to natural habitats increases crop production through the delivery of pollination services. However, similar researches in subtropical regions is largely lacking. In this study we evaluated the role of linear forest fragments (LFFs) on the provision of biotic pollination service to soybean crops (Glycine max) and explored whether this service changes with increasing distance to LFFs in subtropical dry Chaco (Argentina). In three agricultural farms and testing two soybean varieties, we covered plots of 0.75 m2 with soybean plants and compared them with equally sized open plots. Plots were placed near (60 m) and far (600 m) from LFFs. We found that plants from the open treatment produced 32% more pods, 41% more seeds and had 42% higher yield (kg/ha) than plants from the covered plots. The difference between open and covered plots in seeds and yield did not change significantly with the distance to LFFs, but the number of pods, contrary to what we expected, was higher far from LFFs. Our findings highlight the possible impact of pollinators on soybean yield in both varieties tested here; but the proximity to LFFs was not directly related to a larger difference in production. Observed patterns are explained by edge effects and competition between soybean plants and trees near LFFs, combined with an underestimation of the distance from the natural hives to which honeybees can efficiently exploit the crops. In this subtropical region, soybean expansion is the most important driver of land cover change and this study represents a first step towards a better understanding of the functioning of these remnants of natural areas within the agricultural land in the region of dry Chaco forests. [ABSTRACT FROM AUTHOR]

Copyright of Ecologia Austral is the property of Asociacion Argentina de Ecologia 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.)

Aims Ligustrum lucidum, native to China, is one of the dominant exotic and invasive tree species in secondary forests in Argentina. (1) We assessed its invasion during 20 yr in post-agricultural secondary forests dominated by native tree species, and (2) evaluated tree demographic rates of native individuals under and away from L. lucidum trees that invaded these forests. Locations Four 1-ha permanent plots of secondary forests, subtropical Andes of Tucumán, Argentina. Methods We quantified the invasion of L. lucidum individuals (≥10-cm diameter) from 1991 to 2011 within four 1-ha plots of secondary forests and analysed annual growth and mortality rates of native tree individuals (≥10-cm diameter) under and away from L. lucidum trees. For this, we compared tree demographic rates of all native individuals together (community level) under and away from individuals of L. lucidum, referred to as exotic and native neighbourhoods, respectively. Then, we described the relative growth rate of native tree species in exotic/ native neighbourhoods (species level) and related them to their demographic life histories and morpho-physiological traits. Results Both density and basal area of L. lucidum increased from 0.1% to 4% between 1991 and 2011. Native tree individuals grew 65% less in exotic neighborhoods compared to native neighborhoods. Relative growth rate showed negative values under L. lucidum individuals for the abundant species Ocotea porphyria, Parapitadenia excelsa, Juglans austalis and Allophylus edulis, indicating competition; while less abundant species Terminalia triflora, Cupania vernalis and Blepharocalix saliscifolius showed positive growth values under L. lucidum, suggesting a facilitation process. Thus, L. lucidum competes efficiently with some native tree species, particularly with those abundant species that dominate the canopy. Conclusions Ligustrum lucidum is invading post-agricultural secondary forests dominated by native tree species. While invading, L. lucidum competes with native abundant tree species that dominate the main structure of the forest canopy. As this invasive trend will likely increase in the near future, L. lucidum may alter forest structure, composition and dynamics, as well ecosystem functioning. [ABSTRACT FROM AUTHOR]

Gleditsia triacanthos L. is a woody species native to North America that has invaded Uruguay, Spain, Australia, South Africa and several countries of Central and Eastern Europe. In Argentina, it has become one of the most important invasive woody species and has a high potential to continue spreading. In this study, we review different aspects of G. triacanthos invasion in Argentina that include descriptions of invaded ecoregions and environments, intrinsic characteristics of the species, invasion dynamics and impacts. In addition, we discuss mechanisms that potentially explain its success, control strategies and natural barriers to its invasion. We reviewed a total of 91 articles and book chapters, of which 62 were developed in Argentina. Studies reported that the invasion of G. triacanthos in different ecoregions was favoured by intrinsic characteristics of the species, together with the interaction with cattle and disturbances, which cause negative impacts on flora, fauna and ecosystem processes. Disturbances were proposed as the main mechanism to explain this species' invasion, but other hypotheses such as the release of natural enemies and/or propagule pressure might also be important. Further studies are required, mainly on the impacts on ecosystem processes and on the control, production of organic compounds and mutualistic interactions (with nitrogen-fixing bacteria and mycorrhizal fungi). [ABSTRACT FROM AUTHOR]

Invasive plant species may benefit from a reduction in herbivory in their introduced range. The reduced herbivory may cause a reallocation of resources from defence to fitness. Here, we evaluated leaf herbivory of an invasive tree species (Ligustrum lucidum Aiton) in its native and novel ranges, and determined the potential changes in leaf traits that may be associated with the patterns of herbivory. We measured forest structure, damage by herbivores and leaf traits in novel and native ranges, and on the basis of the literature, we identified the common natural herbivores of L. lucidum. We also performed an experiment offering leaves from both ranges to a generalist herbivore (Spodoptera frugiperda). L. lucidum was more abundant and experienced significantly less foliar damage in the novel than in the native range, in spite of the occurrence of several natural herbivores. The reduced lignin content and lower lignin: N ratio in novel leaves, together with the higher herbivore preference for leaves of this origin in the laboratory experiment, indicated lower herbivore resistance in novel than in native populations. The reduced damage by herbivores is not the only factor explaining invasion success, but it may be an important cause that enhances the invasiveness of L. lucidum. [ABSTRACT FROM AUTHOR]

Exotic species may influence the process of decomposition, either directly (through differences in the quality and/or quantity of leaf-litter) or indirectly (by altering microclimatic conditions and the abundance and/or activity of decomposers). The aims of our study were: I) to compare the decomposability of the most abundant exotic and native species in secondary forests of the Sierra de San Javier, Tucumán, II) to assess the effect of microenvironemtal conditions on the rate of decomposition of an homogeneous substrate and III) to evaluate the effect of the litterbags mesh size on the decomposition process. To do this, we incubated leaf-litter of 7 native and 7 exotic species under standard conditions for one year and also leaf-litter of Populus deltoides (homogeneous substrate) in native and invaded by Ligustrum lucidum secondary forest patches in bags with two mesh sizes. Native and exotic species did not differ in their weight loss rates, but there were interspecific differences. The decay constant of the homogeneous substrate was lower in invaded patches so it is possible that L. lucidum modify the composition and /or activity of decomposing organisms and generate changes in micro-environmental conditions. In addition, decomposition was higher in bags with larger mesh size. This pattern may be explained by the differential access of macro invertebrates. Our results suggest the absence of a pattern of decay in native and exotic species as groups, and the potential influence that L. lucidum would have over the factors controlling littler decomposition. [ABSTRACT FROM AUTHOR]

Abstract: Invasions of exotic tree species can cause profound changes in community composition and structure, and may even cause legacy effect on nutrient cycling via litter production. In this study, we compared leaf litter decomposition of two invasive exotic trees (Ligustrum lucidum and Morus sp.) and two dominant native trees (Cinnamomum porphyria and Cupania vernalis) in native and invaded (Ligustrum-dominated) forest stands in NW Argentina. We measured leaf attributes and environmental characteristics in invaded and native stands to isolate the effects of litter quality and habitat characteristics. Species differed in their decomposition rates and, as predicted by the different species colonization status (pioneer vs. late successional), exotic species decayed more rapidly than native ones. Invasion by L. lucidum modified environmental attributes by reducing soil humidity. Decomposition constants (k) tended to be slightly lower (−5%) for all species in invaded stands. High SLA, low tensile strength, and low C:N of Morus sp. distinguish this species from the native ones and explain its higher decomposition rate. Contrary to our expectations, L. lucidum leaf attributes were similar to those of native species. Decomposition rates also differed between the two exotic species (35% higher in Morus sp.), presumably due to leaf attributes and colonization status. Given the high decomposition rate of L. lucidum litter (more than 6 times that of natives) we expect an acceleration of nutrient circulation at ecosystem level in Ligustrum-dominated stands. This may occur in spite of the modified environmental conditions that are associated with L. lucidum invasion. [Copyright &y& Elsevier]

Abstract: Grazing and fire have been the most common disturbances in many grasslands ecosystems for many centuries. However, some mountain regions are currently experiencing a decrease in land use, and therefore in frequency or intensity of these disturbances. In this study, we evaluated how fire and grazing affect vegetation structure in mountain grasslands of NW Argentina. We hypothesized that they would have differential effects on plant species richness, vegetation composition and aerial biomass dynamics, predicting that fire would have a stronger effect on these variables than grazing. We tested this hypothesis by performing a controlled field experiment in which we manipulated fire and compared grazed plots with ungrazed exclosures, simulating current (high frequent fires and low livestock load) and future (fire suppression and grazing exclosure) scenarios. We recorded total of 90 species with 40 shared among all treatments. Tussock grasses (Elionurus muticus), followed by three shrubs represented the main contribution to live biomass in all treatments. Species richness, equitativity and diversity were higher in burned plots. Multivariate ordination indicated that burning is more important than grazing in determining plot to plot similarity in species composition. Burning reduced total aerial biomass, standing dead biomass and litter, as well as live biomass, that was also reduced by grazing. Burning also reduced standing dead biomass and litter proportions, but increased live biomass contribution, showing a more evident effect within the grazed plots. Burning, seasonality and growing season had significant effects on the relative contribution of all biomass categories. Biomass consumption showed a strong seasonality, being significantly higher in January of both growing seasons, and it was not affected by burning. We conclude that under the current fire and grazing scenario, fire plays a more important role than grazing in shaping these grasslands dynamics. [Copyright &y& Elsevier]

In the last decades, South American ecosystems underwent important functional modifications due to climate alterations and direct human intervention on land use and land cover. Among remotely sensed data sets, NOAA-AVHRR "Normalized Difference Vegetation Index" (NDVI) represents one of the most powerful tools to evaluate these changes thanks to their extended temporal coverage. In this paper we explored the possibilities and limitations of three commonly used NOAA-AVHRR NDVI series (PAL, GIMMS and FASIR) to detect ecosystem functional changes in the South American continent. We performed pixel-based linear regressions for four NDVI variables (average annual, maximum annual, minimum annual and intra-annual coefficient of variation) for the 1982-1999 period and (1) analyzed the convergences and divergences of significant multi-annual trends identified across all series, (2) explored the degree of aggregation of the trends using the O-ring statistic, and (3) evaluated observed trends using independent information on ecosystem functional changes in five focal regions. Several differences arose in terms of the patterns of change (the sign, localization and total number of pixels with changes). FASIR presented the highest proportion of changing pixels (32.7%) and GIMMS the lowest (16.2%). PAL and FASIR data sets showed the highest agreement, with a convergence of detected trends on 71.2% of the pixels. Even though positive and negative changes showed substantial spatial aggregation, important differences in the scale of aggregation emerged among the series, with GIMMS showing the smaller scale (≤11 pixels). The independent evaluations suggest higher accuracy in the detection of ecosystem changes among PAL and FASIR series than with GIMMS, as they detected trends that match expected shifts. In fact, this last series eliminated most of the long term patterns over the continent. For example, in the "Eastern Paraguay" and "Uruguay River margins" focal regions, the extensive changes due to land use and land cover change expansion were detected by PAL and FASIR, but completely ignored by GIMMS. Although the technical explanation of the differences remains unclear and needs further exploration, we found that the evaluation of this type of remote sensing tools should not only be focused at the level of assumptions (i.e. physical or mathematical aspects of image processing), but also at the level of results (i.e. contrasting observed patterns with independent proofs of change). We finally present the online collaborative initiative "Land ecosystem change utility for South America", which facilitates this type of evaluations and helps to identify the most important functional changes of the continent.