Evangelina Natale

Presence—Absence versus Invasive Status Data for Modelling Potential Distribution of Invasive Plants: Saltcedar in Argentina

Abstract: Spontaneous populations of saltcedars are widely distributed in Argentina. The invasive behaviour of the genus has been documented in the USA, Mexico, and Australia, where its presence is associated with significant changes in ecosystem functioning and the structure of natural communities. Previous to this work there were no studies assessing the potential of saltcedars as drivers of ecological change in Argentina. The aim of this work was to assess the potential distribution of saltcedars in the country in order to provide useful information for designing management strategies to reduce the impacts associated with their invasion. Known occurrences of the genus in Argentina were used to predict its potential distribution by applying different distribution models using both presence/absence and presence-only data. The DOMAIN model was the model that performed best once sensitivity and omission errors were taken into account. Our results indicate the severity of the problem of saltcedar in Argentina, with more than three quarters of the total arid and semiarid area vulnerable to invasion. Our results also highlight the need to include information about the status of populations when selecting training points for the development of distribution models.

Saltcedar (Tamarix ramosissima) Invasion Alters Decomposer Fauna and Plant Litter Decomposition in a Temperate Xerophytic Deciduous Forest

Plant invasions may alter the soil system by changing litter quality and quantity, thereby affecting soil community and ecosystem processes. We investigated the effect of Tamarix ramosissima invasion on the decomposer fauna and litter decomposition process, as well as the importance of litter quality in decomposition. Litter decomposition and decomposer communities were evaluated in two monospecific saltcedar forests and two native forests in Argentina, in litterbags containing either local litter (saltcedar or dominant native species) or a control litter. Saltcedar invasion produced an increase in Collembola, Acari, and total mesofauna abundance, regardless of the litter type. Control litter decomposition was higher in the native forest than in the saltcedar forest, showing that increased abundance of decomposer fauna does not necessarily accelerate decomposition processes. Local litter decomposition was not different between forests, suggesting that decomposer fauna of both ecosystems is adapted to efficiently decompose the autochthonous litter. Our results suggest that the introduction of a resource with higher quality than the local one has a negative effect on decomposition in both ecosystems, which is more pronounced in the invaded forest than in the native forest. This finding stresses the low plasticity of saltcedar decomposer community to adapt to short-term environmental changes.

Susceptibilidad del Olmo (Ulmus pumila), y de cinco especies arbóreas nativas del centro-sur de la Provincia de Córdoba (Argentina), a la infección por Pleurotus ostreatus (Agaricales: Pleurotaceae).

Susceptibility of Elm (Ulmus pumila), and of five tree species native to the center-south of the Province of Cordoba (Argentina), to infection by Pleurotus ostreatus (Agaricales: Pleurotaceae). Biological invasions advance on ecosystems causing major changes in their structure and ecological processes. Ulmus pumila L., is an exotic species that develops processes of invasion in Argentina and mechanical and chemical techniques have been used for its control in the affected sites. Biological control is now considerated as a new alternative. In the present work, the infection capacity of Pleurotus ostreatus on U. pumila plants was evaluated in order to collect and provide basic information to generate new options for biological control of U. pumila. Laboratory tests were carried out to determine the success of establishment of Pleurotus on cuttings of native tree species from the biogeographic district of Espinal and U. pumila. It was found that P. ostreatus had the ability to externally colonize all evaluated species although only in stakes of U. pumila could complete the life cycle. Finally, the anatomical study of the wood indicated that U. pumila is the species, among the studied ones, with greater proliferation of mycelium and even with formation of chlamydospores. In this way, it can be said that this exotic species is more susceptible to fungal infection than the native species studied.