Challenges on the conservation of traditional orchards: Tree damage as an indicator of sustainable grazing.

Traditional orchard meadows are among the most valuable cultural and agricultural systems for nature conservation in Europe. They comprise scattered fruit trees over a highly diverse herbaceous layer and provide a wide range of ecosystem services. However, they are strongly endangered due to farmland intensification and abandonment. Livestock grazing is known to promote grassland diversity but it may also cause tree damage through debarking. In this study, we evaluated the effect of different grazers (cattle, horse and sheep) on fruit trees in 42 traditional orchards of the Rhenish uplands (Germany). Overall, we found that 70% of the study trees showed debarking damage, although most of them (40%) were slightly damaged (1-10% of the trunk debarked). Most debarked trees showed accumulated damage over time, and only 8% of the study trees were damaged during the last year. The probability of strong debarking (>50% of the trunk damaged) was higher in orchards grazed by cattle and horses than on those grazed by sheep (5.3 and 3.7-fold difference, respectively). Importantly, unsustainable levels of cumulative debarking caused a decay of crown development, which may strongly affect fruit production. Additionally, lower tree densities favored higher levels of debarking intensity but did not affect the probability of occurrence. Individual tree-protection was an effective practice in decreasing trunk debarking (95% reduction in tree damage occurrence). The impact of grazing animals on trees might represent a useful indicator to assess the sustainability of each grazing system and should be taken into account in future agriculture and conservation policies.

Effects of cattle management on oak regeneration in northern Californian Mediterranean oak woodlands.

Oak woodlands of Mediterranean ecosystems, a major component of biodiversity hotspots in Europe and North America, have undergone significant land-use change in recent centuries, including an increase in grazing intensity due to the widespread presence of cattle. Simultaneously, a decrease in oak regeneration has been observed, suggesting a link between cattle grazing intensity and limited oak regeneration. In this study we examined the effect of cattle grazing on coast live oak (Quercus agrifolia Née) regeneration in San Francisco Bay Area, California. We studied seedling, sapling and adult density of coast live oak as well as vertebrate herbivory at 8 independent sites under two grazing conditions: with cattle and wildlife presence (n = 4) and only with wildlife (n = 4). The specific questions we addressed are: i) to what extent cattle management practices affect oak density, and ii) what is the effect of rangeland management on herbivory and size of young oak plants. In areas with cattle present, we found a 50% reduction in young oak density, and plant size was smaller, suggesting that survival and growth young plants in those areas are significantly limited. In addition, the presence of cattle raised the probability and intensity of herbivory (a 1.5 and 1.8-fold difference, respectively). These results strongly suggest that the presence of cattle significantly reduced the success of young Q. agrifolia through elevated herbivory. Given the potential impact of reduced recruitment on adult populations, modifying rangeland management practices to reduce cattle grazing pressure seems to be an important intervention to maintain Mediterranean oak woodlands.

A new bioassay method for quantitative analysis of tetracyclines.

A new method is described for quantitative analysis of tetracycline, based on the decrease in external pH of bacterial suspensions after the addition of a glucose pulse. The decrease in external pH of these suspensions was inversely proportional to the concentration of tetracycline. The correlation coefficient of standard response lines derived from the bioassay was 0.99. Tetracycline potency was determined in six tetracycline HCl samples by the sugar pulse bioassay and a turbidimetric method. The turbidimetric assay result varied from the glucose-pulse data by no more than 7 and 3% at 3 and 7 min, respectively. The procedure is rapid, precise and quantitative, and requires minimal preparation and use of media, with savings in laboratory resources and time.