Search

Abstract: In order to preserve, characterize and improve the quality of some accessions in Entre Ríos province, Argentina, a germplasm bank of aromatic and medicinal plants has been set up, including among other species, the oregano (Origanum spp.). To simplify the identification and characterization of the accession entries belonging to this genus, a chart containing 41 descriptors has been elaborated to allow the easy and quick individualization of any material being added to the collection. The first four accessions added to the collection were characterized using this chart and studied taking into account their biomass and essential oil yields and the quality of their volatile fraction. The materials analyzed are locally known as “27-09”, “Peruvian” and “native” clones and are taxonomically identified as hybrids of Origanum × majoricum Cambess; and a fourth material, known as “green Spanish” clone belonging to the species Origanum vulgare L. ssp. viridulum (Martrin-Donos) Nyman. The essential oil yield was similar for all the materials (1.7% (v/w) on dried basis). The estimated aired biomass yield was superior for the Origanum × majoricum hybrid clones (ranging from 4700 to 11,900kgha−1), whereas the “green Spanish” clone only reached a biomass of 2450kgha−1. Meanwhile, based on the quality of the essential oils, O. vulgare ssp. viridulum was more promissory, since it corresponded to a carvacrol type oregano. Finally, it will be necessary to assess the role of the agronomical and ecological variables on the latter clone, in order to increase the content of carvacrol in the essential oil and, at the same time, to improve its biomass yield. [ABSTRACT FROM AUTHOR]

Abstract: We used dendroecological techniques to date fire scars in woody species growing in a subtropical savanna of the Argentine Chaco dry forests, and to explore the temporal trends of fire with rainfall variability at different temporal scales during the 20th century. Eight sampling sites were located along an ecotone between savanna and a dry forest, and a composite chronology was developed for a savanna, based on a total of 21 fire dates. The mean fire frequency was 0.18 fires year−1 and the mean fire interval was 3.3 years. The period post 1971 (which had 22% more rainfall) experienced a fire frequency more than two times higher than the period 1925–1970 (p <0.05). Decadal fire frequency was correlated to 10-years moving average rainfall (R 2 =0.58). Superposed Epoch Analysis showed that fires occur during years of above-average rainfall, and extensive fires tend to follow two years of above-average rainfall, all these associations being statistically significant. These results indicate a climatic control of fire regime, associated to enhanced fine fuels production during years of high rainfall, and imply that regional increase in rainfall associated to global changes in atmospheric circulation are affecting local ecosystems by significantly changing their disturbance regime. [Copyright &y& Elsevier]