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Shrub cover in semiarid rangelands may induce changes in soil resources and ecosystem functioning. However, it is unknown the real influence that shrub vegetation has on soil quality in rangelands used for livestock purposes. We evaluated the shrub cover effect on 12 chemical and biochemical parameters of soil quality. In a semiarid Monte rangeland of Argentina, 6 paddocks were selected and 10 m transects were placed in a patch with (Sh) and without shrubs (WSh). Then, sites with grasses (Sh‐G and WSh‐G), bare ground‐litter (Sh‐BL and WSh‐BL), and under shrub cover (Sh‐S) were selected. In spring 2017 and 2018, a composite soil sample (0–10 cm in depth) was taken at each site (n = 6). Sh‐G and Sh‐S sites presented high values of soil organic matter, soil organic nitrogen, particulate organic matter (POM), and cellulase activity (CA); WSh‐BL and Sh‐BL sites were associated with the lowest contents of these variables. For the rest of the soil quality parameters, the soil sampling sites showed similar values. These results show that woody presence should not be directly linked to soil quality loss. Although we did not detect a shrub effect in all parameters studied, in the context of appropriate grazing management, the presence of plant species of different functional groups has a positive effect on organic matter and N content of soil close to them. Moreover, in these sites, high POM values represent an important reservoir of potentially available nutrients, and promote CA necessary for fresh litter decomposition improving the soil quality of semiarid rangelands. [ABSTRACT FROM AUTHOR]

Abstract: Pappophorum vaginatum is the most abundant C4, warm-season perennial grass in rangelands of northeastern, arid Patagonia, which is often exposed to continuous grazing. Eragrostis curvula is the only naturalized, C4 warm-season genotype that has successfully established from seed during moist years in the study region, that is characterized by a scarce forage availability to livestock during the spring and summer. Successful introduction of perennial forage genotypes is then critical in that region. No studies have yet been conducted to determine the greater abundance of P. vaginatum compared to that of other native C4 grass genotypes (Aristida subulata, A. spegazzinii, Sporobolus cryptandrus) in the study area. The effect of defoliation on arbuscular mycorrhizal colonization was investigated on the four native, one naturalized and five introduced, C3 perennial grass genotypes (Leymus cinereus cvs. “Magnar” and “Trailhead”, and Achnatherum hymenoides cvs. “Paloma”, “Rimrock” and “Nezpar”) growing at the field. We hypothesized that the magnitude of mycorrhizal colonization (1) is similar on defoliated than on undefoliated plants of the native and naturalized genotypes, (2) is greater in the native and naturalized than in the introduced genotypes, and (3) is greatest in P. vaginatum than in all remaining genotypes. Plants of all ten genotypes were either exposed or not to a severe defoliation twice in the growing seasons of 2007/2008 and 2008/2009. The results showed that all studied genotypes maintained arbuscular mycorrhizal colonization levels following defoliation similar to undefoliated controls. The greatest arbuscular mycorrhizal colonization was often found on both cultivars of L. cinereus among all genotypes. The greatest arbuscular mycorrhizal colonization in P. vaginatum than in the other native genotypes at the end of the study, parameter that contributes to defoliation tolerance, could help to explain its greater abundance in rangelands of central Argentina. The higher arbuscular mycorrhizal colonization in both cultivars of L. cinereus might contribute to their successful establishment and survival in rangelands of northeastern, arid Patagonia. Genotype introduction in these rangelands is likely to affect community dynamics because of variable effects of the mycorrhizal symbiosis on the various plant genotypes. [Copyright &y& Elsevier]

In this field study, the effects of water-stress, rainfed, or irrigated conditions on soil phosphorus (P) concentration under the canopy of the native grasses of semi-arid Argentina (late seral Stipa clarazii Ball., early serals S. tenuis Phil., and S. gynerioides Wild. Ex Steud) at different developmental stages and sampling dates during 1996 and 1997 were determined. Plants grew in a uniform matrix such that each plant of S. clarazii and S. tenuis was surrounded by four plants of S. gynerioides. In September 1996, Bray and Kurtz extracted soil P concentrations were greater under plants of S. clarazii if water stress was imposed during the vegetative stage than under rainfed conditions. Bray and Kurtz extracted soil P concentrations were either similar or between 8.7 to 31% greater under plants of S. clarazii than under those of the other two species. The higher nutrient concentration under S. clarazii than under S. gynerioides and S. tenuis may explain previously measured increases in density, frequency, and cover throughout a long-term span (years) in the late over the earlier seral perennial grasses under field exclosures to domestic livestock or appropriate grazing management conditions. [ABSTRACT FROM AUTHOR]

Knowledge of pre-germination seed treatments is critical for ecological restoration practices such as outplantings or direct seeding. However, in drylands, there is a lack of this kind of information about some species with high potential value for ecological restoration. This is the case of Larrea divaricata Cav., a native species that is dominant and can grow in degraded environments to the Monte region and arid ecosystems in Argentina. We evaluated the effects of the following treatments to break seed dormancy in this species: 1) alternation of soaking and drying periods; (2) periods of soaking and rinsing with running water; (3) mechanical scarification, and (4) control. Seed scarification was done using a novel mechanical method using two pieces of sandpaper: one fixed and the other spun using a 710 W hand drill. The variables evaluated were: (a) germination percentage (over time since imbibition and the final percentage), (b) mean time to germination, and (c) number of days before the start of germination. The mechanical scarification treatment improved all germination variables compared to the other treatments. In the mechanical scarification treatment, germination percentage was 60.7%; mean time to germination was 6.32 days, and the number of days before the start of germination was 2 days. Our results indicate that mechanical scarification is an appropriate technique for propagation of L. divaricata Cav. for large scale restoration, since many seeds can be treated quickly and this technique is easily replicable. • Seed pre-germination treatments may be critical for ecological restoration practices. • Mechanical scarification was the best treatment to improve all germination variables. • Seed scarification increased spreading of Larrea divaricata on restoration projects. [ABSTRACT FROM AUTHOR]

The microbiological quality of honey obtained from different processing points and the environmental quality within honey houses were assessed in the Pampas Region (Argentina). Mold and yeast (MY), culturable heterotrophic mesophilic bacteria (CHMB), the number of spore-forming bacteria as well as the presence of Shigella spp., Salmonella spp. and fecal coliforms were evaluated in 163 samples. These samples were taken from eight honey houses. Results showed that 89 samples had ≤10CFU of MY/g honey, 69 ranged from 10 to 50CFU/g and two reached 65.5CFU/g. Eighty one percent of the samples showed ≤30CFU of CHMB/g honey and only seven samples had between 50 and 54.25CFU/g. Thirty six honey samples were obtained from drums: in 25 samples (69.4%) CHMB counts were less than ≤30CFU/g of honey; in 20 samples (55.5%) the values of MY were between 10 and 50CFU/g honey and total coliforms were only detected in 20 samples. Fecal coliforms, spores of clostridia as well as Salmonella spp. and Shigella spp were not detected and less than 50 spores of Bacillus spp. per g were observed in the honey from drums. Therefore, the microbiological honey quality within the honey houses did not show any sanitary risks. Our results were reported to honey house owners to help them understand the need to reinforce proper honey handling and sanitation practices., (Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.)