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Our objective was to assess whether long-term continuous sheep grazing was associated with the bacterial community of the Patagonian Monte soils. We randomly extracted soil samples from 5 plant-covered patches (PCP) and the nearest inter-canopy areas (IC) at sites with low (L), moderate (M) and heavy (H) grazing intensity. Bacterial communities were evaluated by denaturing gradient gel electrophoresis (DGGE) and dominant bands were sequenced. Dendrograms showed a different association among grazing sites in PCP compared to IC areas. In PCP, M and H sites were clustered and DGGE revealed a high similarity in the bacterial community regardless of grazing intensity. In IC areas, analyses clustered L and M sites. Band sequencing revealed that members of these communities belonged to Sphingobacteria , Solibacteres , Gammaproteobacteria , Betaproteobacteria and Bacilli. S ome of the band sequences related to Nitrosococcus oceani and Nitrosococcus watsonii which are restricted to marine environments and salt lakes. Microcoleus vaginatus and diatom chloroplast-related sequences were mainly detected in IC areas from L and M. Heavy grazing could alter autotrophic bacteria/diatom composition in IC areas possibly due to physical disturbance of biological crusts by trampling, threatening the potential of crust re-formation. Grazing intensity affected soil bacterial communities differently in PCP and IC areas with soil crust, highlighting the importance of improving our understanding of microbial diversity responses to land use. [ABSTRACT FROM AUTHOR]

Abstract: Shrub encroachment is the advance of woody plants over grasslands. For some shrub species this process is favoured by fire and high precipitation. In northwestern Patagonia spring precipitation is related with the El Niño Southern Oscillation (ENSO). Over the past years, ENSO has shown an increase in both amplitude and frequency. Our study focuses on the population dynamics of the shrub Fabiana imbricata Ruiz & Pav. (Solanaceae) using stochastic models which involve different fire frequencies and variations in spring precipitation. Our results indicate that F. imbricata''s population grows at a wide range of fire frequencies, reaching its maximum every 6–10 years. The elasticity analysis show that, as fire frequency diminishes, population growth rate depends almost exclusively on adult survival, recruitment events are rare and the presence of seedlings or juveniles is seldom observed. In this case, the landscape would be formed by mature F. imbricata shrublands, and population persistence would depend on adult survival, seed production and their accumulation in the soil bank. However, in the case of very high fire frequencies, more recurrent recruitment pulses would be observed, with a landscape dominated by young shrublands composed of individuals of different ages and reproductive status. [Copyright &y& Elsevier]

Abstract: Wildfires can cause severe impacts on the terrestrial ecosystems depending on their frequency and behavior. We studied the environmental factors influencing the spatial and temporal distribution of fires, their size and duration in the central semiarid Argentina. We identified fires using MODIS satellite data and we analyzed their association with climate and land cover/use patterns. Spatial and temporal fire patterns varied between eastern, central and western regions according to the presence of agriculture, shrublands and water deficits, respectively. The frequency and behavior of fires also varied temporally with water conditions. Years with low effective precipitations were characterized by an important hotspot density and fire number, as well as the months preceded by two months with low effective precipitation (r 2: 0.42; p < 0.0001). We observed a spatial delay of fires in a northeast–southwest sense, related to the delay of the spring beginning (r 2: 0.7594; p < 0.0001). The mean fire sizes and duration varied significantly among vegetation types (F: 10.76, p < 0.0001 and F: 3.703, p < 0.01). Fires were bigger in shrublands and longer in shrublands or forests regarding agricultural areas or degraded areas (F: 16.0, p < 0.0001). The results obtained would be useful to prevent/control fires and to preserve natural resources and human communities. [Copyright &y& Elsevier]