Result summary
- Cattle behaviour and habitat preference was affected by vegetation characteristics and environmental factors.
- No difference in habitat utilisation between grazing and resting cattle could be observed
- Habitat utilisation changed for resting cattle due to changes in weather factors
- The most common ecological implications of grazing in grasslands could be observed
- The vegetation height decreased throughout the study period
- Areas of high grazing activity are of high species richness
- Nutrient transfer could be observed and is positivly correlated with species richness
Habitat utilisation
Grazing cattle prefer open, species-rich grassland areas with medium vegetation height, presumably due to the higher nutrient content of the grassland found in this area. Accordingly, the avoided areas had high tree and shrub cover, low vegetation height and low species richness. This supports many previous studies suggesting that cattle generally prefer gentle terrain and medium vegetation height for both grazing and resting, as they have a better balance between work and yield when grazing and greater comfort when resting. These observations illustrate the complexity of the relationship between cattle habitat utilisation and environmental factors, as almost all factors affect cattle habitat preference, making it difficult to determine the driving factors, especially due to the linkages between environmental factors. Since species richness is highest in the favoured areas and lowest in the areas that are clearly avoided, one could conclude that species richness is one of the driving factors for habitat preference. This is supported by the fact that high tree cover and high elevation are generally negatively correlated with species richness.
The observation that there are no differences in habitat utilisation between both behaviour groups is contrary to the observations made in other studies. Several studies showed a difference in prefered areas for different behaviours. The contrasting observation of this study could be due to the method used to determine between the behaviours.
Impact of weather factors
Changes in hourly temperature or precipitation levels led to no highly significant changes in habitat utilisation for grazing cattle. This is contrary to most story but has been observed during a similar study in Norway as well, and was presumingly due to the minimal changes in temperature.
For resting cattle however, significant changes could be observed. Higher temperture led to an avoidance of areas with higher soil mositure and a preference for areas with high shrub cover, higher temperture led to an avoidance of soil moisture and an increased preference for tree cover. The avoidance of soil moisture might be due to the stronger preference for cover during this events as the areas of higher soil moisture correspond to open areas with minimal to no cover. Canopy cover was utilisied for different reason during the different weather factor changes. Tree cover was utilisied for shade to protect the cattle from heat stress, while the shrub cover was utilisied for shelter against the rain.
Ecological implications
Nutrient transfer
The results indicate that there was a nutrient transfer from areas of higher grazing intensity to areas of higher cow dung density in both pastures. This is a controversy topic in literature which several studies claiming similar observation to this study, while several other could not share this observation. One study concluded that stable grazing and movement patters led to distinct nutrient depletion and accumulation zones that differ in their plant species richness and plant species composition. As the plant species richness is positivly related to both grazing and higher dung density it could be assumed that plant species richness is influenced by grazing as well as fouling.
Plant species richness
Many studies stated that grazing promotes species diversity and richness. Additionally, grazing creates more heterogeneity at smaller scales, further enhancing not only flora but also faunal biodiversity by creating changes in food plant abundance and breeding grounds. While grazing in general showed a positive response to species rich areas in this study, grid-cells with the highest species richness are grid-cells with moderate grazing density, indicating that grazing intensity plays and important role for the impact on species richness. The effect of grazing on plant diversity is more complex and related to other factors, e.g. overall grassland moisture and grazing history. Similar to the conditions in our study, where areas with higher species richness correspond to areas with higher soil moisture and lower canopy cover as well as areas with higher grazing density and areas with higher cow dung density than grazing density, illustrating the complexity of the relationships between species richness and other factors in grassland.
Reduction of biomass
The study found a notable decrease in vegetation height throughout the grazing season, resulting in reduced biomass and litter accumulation by the season’s end, crucial for maintaining species diversity. The research highlights the benefits of grazing in decreasing litter and potentially enhancing plant diversity in subsequent seasons. The variation in vegetation height during mid-season (June-August) plays a key role in insect diversity, with previous studies indicating that vegetation height and variation affect insect diversity alongside nectar flower abundance. Grazing activities contribute to faunal diversity by generating small-scale heterogeneity in grasslands.
Grazing livestock play a crucial role in the conservation of semi-natural grasslands, preventing them from turning into scrubland or forest. Intensive management practices such as annual mowing or grazing are vital for maintaining species-rich grasslands. In heterogeneous grassland areas, grazing is preferred over mechanical mowing due to practical challenges. This study stresses the effectiveness of grazing, evident in the significant decrease in vegetation height and the strong correlation between grazing livestock density and vegetation height distribution. Continuous management practices are essential in Swedish grasslands to uphold their conservation value.