Dataset of plant communities treated by different herbivore dung quality, quantity and type of grazing

The dataset was derived from a 3-year mesocosm experiment designed to examine the effects of herbivore dung quantity, quality, and grazing type on plant community productivity and diversity. It includes data on five levels of dung quantity from three herbivore species (rabbit, horse, and European bison), each differing in dung quality (N:P ratio). The experiment also incorporated three grazing treatments: no grazing, bulk grazing, and selective grazing of legume plants. Measurements include plant community productivity, species diversity, light availability, and the abundance of specific plant types. The dataset captures interactions between dung type, grazing, and plant responses, providing insights into the complex roles of herbivores in shaping terrestrial ecosystems.

Methods
Dung and Soil Collection

Dung from European bison, horse, and rabbit was collected on 25 February 2020 in the National Park Zuid-Kennemerland, Netherlands, a coastal dune ecosystem with nutrient-poor sandy soils. Fresh dung was collected directly after excretion (horse and bison) or from areas with high rabbit density. Samples from at least five individuals per species were stored at 4 °C. Moisture content and concentrations of total carbon (C), nitrogen (N), and phosphorus (P) were determined. Soil from the top 10 cm layer was also collected, sieved, mixed, and used to inoculate mesocosms with soil microbes.

Mesocosm Experiment

In April 2020, 90 mesocosms (30 L) were set up in Brussels. Each mesocosm was filled with quartz sand and 1 L of collected soil. Dung from rabbit, horse, or bison was added at five levels (12.5–200 mg P per mesocosm). Grazing treatments included no grazing, bulk grazing (clipping all plants to 5 cm), or selective grazing (clipping only legumes). Treatments were replicated twice. Plant communities consisted of eight grassland species, and light penetration and plant abundance were measured annually for three years using a point-intercept method and PAR measurements.

Calculations and Statistical Analyses

Dung quantity was log-transformed, and plant abundance data were log(x+1)-transformed. Pielou’s evenness index was calculated from Shannon’s diversity index. Mixed-design ANOVA tested the effects of dung type, quantity, grazing, and time on plant abundance, light penetration, and evenness. Generalized Effect Size (GES) assessed factor impacts. Differences in dung nutrients across species were analyzed using one-way ANOVA. All analyses were performed in R.