Grazing by semi-feral cattle and horses supports plant species richness and uniqueness in grasslands

Abstract

Question: How do naturalistic grazing in contrast to mowing and free succession affect plant community composition and species richness in a temperate grassland grazed by semi-feral cattle and horses? Location: Mols Laboratory, DenmarkMethods: We investigated grazing exclosures in the rewilding area of the Mols Laboratory, four years after its establishment. We focused on moist to dry grassland vegetation, i.e. excluding scrub and woodland. Each experimental block consisted of five 5 × 9 m plots, representing four fenced treatments, i.e. summer-only grazing, winter-only grazing, full exclosure with annual autumn mowing and full exclosure with passive succession. The matrix was grazed by large herbivores at close-tonatural densities, i.e. regulated bottom-up by the carrying capacity of the area. Hence, the seasonal grazing treatments were grazed at close-to-natural animal density. Quantitative plant community composition was assessed using the point-intercept method in 25 × 25 cm quadrats, supplemented with biomass calibration models based on additional quadrats, in which above-ground plant biomass was harvested after recording and the material sorted to species and weighed. Uniqueness was assessed as the sum of inverse range sizes for constituent species.

Contrasting seasonal patterns in diet and dung‐associated invertebrates of feral cattle and horses in a rewilding area

“…Multiple studies have shown positive effects of year-round grazing with these species on plant diversity and vegetation structure (e.g., Gilhaus et al, 2014;Köhler et al, 2016). In the Mols Laboratory in Denmark, where our study was conducted, exclosure experiments have shown higher plant species richness, indications of higher floristic uniqueness, and higher forbs-to-graminoids ratios in plots with year-round or winter grazing compared to mowing or summer grazing (Bonavent et al, 2022). These studies highlight the importance of natural grazing regimes for plant species diversity.…”