Jan Gaisler

Effect of rotational and continuous grazing on vegetation of an upland grassland in the Jizerské hory Mts., Czech Republic

The effect of different grazing regimes on pasture vegetation was studied during the intensive grazing of heifers in the Jizerské hory mountains during 1993–1997. The vegetation was monitored in 3 pairs of permanent 1×1 m plots using a continuous grid of nine 0.33 × 0.33 m subplots. We applied continuous stocking and rotational grazing. Vegetation varied as a result of time and differences between treatments. Several prostrate dicotyledonous species (Trifolium repens, Taraxacum sp.,Bellis perennis andLeontodon autumnalis) increased under continuous stocking. This treatment also promoted the growth of the perennial grassLolium perenne, which was able to cope with frequent defoliation. Tall grasses sensitive to frequent defoliation (Poa trivialis, Holcus mollis, Alopecurus pratensis, Dactylis glomerata andElytrigia repens) were more abundant in rotationally grazed paddocks. Species diversity was not significantly influenced by the different grazing systems. The decrease in the potential sward height under continuous stocking revealed the replacing of tall dominants by lower species. Our results indicate that different grazing systems alter the composition and structure of grassland vegetation. Defining the intensity of grazing under continuous stocking or rotational grazing is complex due to the different stocking rates and the heights of sward during a grazing season. Information about pasture management should therefore involve not only grazing intensity but also the grazing system used.

Sward-height patches under intensive and extensive grazing density in an Agrostis capillaris grassland

Patchiness is one of the important features of grazed temperate grasslands, but little is known about the structure of sward height patches under different grazing intensities. The present study examined the effect of continuous intensive and extensive stocking of heifers on the proportions of sward-height patch categories (short ≤ 5cm, moderate 5.5–10 cm, tall ≥ 10.5 cm) and their plant species composition in an Agrostis capillaris grassland. A four-year study was performed on an upland grassland maintained under a long-term grazing experiment in the Jizerské hory Mts (Jizera Mountains), Czech Republic. The contrasting stocking densities form the differences in the proportion of sward-patch categories and generated a similar level of patch heterogeneity, which was mainly affected by the proportion of tall- and short-sward patches. The floristic composition of patches within the same sward height category depended upon stocking density. Moderate and tall patches under a given stocking density had similar botanical composition. Vegetation within short patches differed considerably from that of other patches under extensive grazing whereas under intensive grazing the differences between short, moderate and tall sward-height patches were small. The findings show that grazing intensity is a key driver of the proportion as well as the floristic composition of sward-height patches in grasslands dominated by A. capillaris. These findings have implications for nature conservation, as they support the recommendation for extensive management of upland grasslands.