Tolerance to mechanical damage in ten herbaceous grassland plant species

The establishment of plants with high damage tolerance may provide a means for soil protection on sites exposed to strong disturbance. In a pot experiment, we investigated the tolerance to mechanical strain of ten grassland plant species representing three growth form groups (cespitose: Festuca arundinacea, Lolium perenne, Taraxacum officinale; rhizomatous: Achillea millefolium, Elymus repens, Poa pratensis; stoloniferous: Agrostis stolonifera, Festuca rubra rubra, Poa supina, Trifolium repens). We hypothesised that growth form and pre-disturbance biomass allocation to the root serve as predictors of damage tolerance. With a tool imitating the action of cleated football boots or scratching chicken, we applied three standardized levels (moderate, medium, strong) of a torsional force which exceeded the shear strength of the sward and impacted on shoots and roots. Post-treatment shoot biomass in relation to shoot biomass of the non-treated control plants served as a measure of damage tolerance. Species, but not growth form groups, differed significantly in damage tolerance, with F. arundinacea and P. pratensis showing the best performance. Shoot re-growth was strongly correlated with relative post-treatment root biomass across all species and treatment levels (R2 = 0.25, P < 0.001), but not with pre-treatment root biomass. We conclude that root resistance to mechanical damage is the prevalent determinant of tolerance to disturbance

Performance of extensive cattle stocking on a reclaimed minerotrophic wet grassland

Extensive stocking with cattle is a common type of grassland management in reclaimed fen sites. However, due to the high productivity of grassland on organic soil with a history of intensive management, stocking at low rates may not allow an adequate balance of herbage production and utilisation. In the present study we examined the agronomic performance of an established (6-year) extensive cattle grazing system on a reclaimed fen grassland site in north-western Germany during the course of the grazing season. We regularly quantified the amount and energy content of herbage on offer based on compressed sward height (CSH), the spatial extent of patches of various degrees of grazing intensity (heavily or moderately grazed, non-grazed), and the chemical composition of the herbage, and assessed energy uptake and livestock performance in terms of live weight gain of the cattle. We deduced herbage utilisation from these data and quantified functional relationships between cattle grazing and the properties of the sward. Our data show that there was an inadequate balance between quantity and quality of forage on offer on the one hand, and demand and forage consumption by livestock on the other. As a result, live weight gains showed a seasonal pattern with a minimum in summer. The amount of energy on offer per animal unit had a significant effect on the sward structure, i.e. on both the area proportion of heavily grazed patches and the heterogeneity of CSH. These findings may be of interest in the context of conservation management of reclaimed fen grasslands, as they may contribute to the design of grazing regimes aiming to create particular sward structures, e.g., to provide habitat for individual target species