| Popis: |
Seasonal alpine and subalpine pastures are a source for many ecosystem services. These span from ecological services like biodiversity and soil stability to economic services like food production or even income from tourism. Land use change, induced through advances in agriculture, many of which are not applicable in these areas, led to widespread land abandonment and the spread of shrubs. The goal of this doctoral thesis was to evaluate in a whole system approach consequences of shrub encroachment on seasonal pastures and assess management options and their impacts on use of this land for meat production. First, a vegetation survey of randomly sampled pasture-shrub gradients showed that the dominant shrub species predicts the shape of species richness response best. Environmental factors believed to be the main predictors until now were gradually eliminated in the process of the analysis. It was established that Alnus viridis (green alder) shrub forests elicit a linear decline in species richness with increasing cover, while Pinus mugo and other shrub species showed a hump-shaped response with the highest species richness at 19% and 42% shrub cover, respectively. It can be assumed that the linear decline is driven by nitrogen leaching into pastures and nutrient rich litter deposition from the A. viridis shrubs. Further, in a grazing experiment with high and low stocking rates, Dexter cattle, Engadine sheep and Pfauen goats equipped with GPS trackers on pastures encroached with A. viridis demonstrated that Engadine sheep were best suited for halting or decreasing shrub cover. Dexter cattle were only doing minor damage to shrubs through trampling and did not penetrate the shrubs as deep as the goats or sheep. Pfauen goats while using the pasture the most even of all species and thus spending more time in the encroached parts of the pasture, mostly browsed and debarked Sorbus aucuparia. This is unfortunate because A. viridis stands tend to inhibit the succession towards forest and S. aucuparia is one of the few tree species being able to establish itself. Thus, while debarking by goats was generally more intense than that by Engadine sheep, browsing preferences of goats are less suited to combat encroachment with A viridis than that of Engadine sheep. Finally, a grazing experiment with Dexter cattle and Engadine sheep but with different levels of A. viridis cover allowed for a detailed study of effects on meat and carcass quality of the two species. There were no negative impacts of high shrub cover on any of the growth, carcass or meat quality measures, showing that meat production is viable even with A. viridis covers above 60%. Again, Engadine sheep turned out to be better suited as conformation scores increased with shrub cover. High yields and crude protein content obtained from exclusion cages showed that the forage of the A. viridis understory seems to be undervalued. Fatty acid profiles found in meat and fat of both species were beneficial to human health with large proportions of mono- and polyunsaturated fatty acids. The assumption to find higher amounts of unsaturated fatty acids in meat and fat due to higher intake of 14 tannins with higher shrub cover could not be confirmed. One reason could be the higher biohydrogenation of fatty acids due to the high crude protein content of shrub understory. In conclusion, the thesis showed the need for intervention on pastures encroached with green alder, the suitability of Engadine sheep in counteracting the encroachment and the ability of Dexter cattle and Engadine sheep to utilise enough of the available resources to successfully implement meat production systems. |
