< Terug naar vorige pagina
Publicatie
Impact of herbivore dung quantity, quality, and grazing activities on plant growth and competition
Boek - Dissertatie
Korte inhoud:Mammalian herbivores play a pivotal role in terrestrial ecosystems, influencing nutrient cycling and plant community composition through plant consumption and dung and urine excretion. Herbivore species differ in these ecosystem effects because they vary in the plants they consume (selective or non-selective) and in the quality of the urine and dung (for instance in the concentrations and ratios of carbon, nitrogen, and phosphorus, and probably also in the microbial composition although this is largely unknown for wild herbivores). Also, the impact of herbivore dung quality (nutrients and microbes) on plant growth and competition is only poorly understood.
The objectives of this PhD study were to (i) determine and compare the dung microbial composition among some common European herbivore species (European bison, cow, horse, fallow deer, and rabbit), (ii) to investigate if the microbial activity in herbivore dung influences plant-symbiotic associations, plant growth, and plant species competition, and (iii) to investigate interactive effects of dung quantity, quality, and grazing activities of different herbivores on plant community composition.
Thereto we collected herbivore dung samples in a coastal dune ecosystem in The Netherlands (Kennemerduinen) and determined the nutrients and microbiome composition in it. We performed two mesocosm experiments in the greenhouse of the VUB: One investigating the effects of sterilized and unsterilized cow dung on symbiotic associations and growth of Trifolium pratense, and a second one investigating the effects of sterilized and unsterilized dung of European bison on growth and competition of 10 European grassland species. Finally, we set up and monitored a long-term mesocosm experiment in the VUB campus garden, investigating the interactive effects of the dung quantity and quality of rabbit, horse, and European bison as well as grazing activities (no grazing, selective grazing of legumes, bulk grazing) on the productivity and diversity of an experimental plant community (8 grassland species).
We identified differences in the nutrient composition and microbial communities in the dung of the five herbivore species and correlated these to differences in their diets and digestive systems. Sterilization of the cow and bison dung negatively affected nodulation (i.e., the activity of symbiotic N2-fixing bacteria) and growth of Trifolium pratense, and bison dung sterilization had species-specific effects on the competition between several legume species, including Trifolium pratense, and a few non-legumes, including Leucanthemum vulgare, with the grass species Anthoxanthum odoratum. Additionally, our outdoor mesocosm experiment, combined with various grazing treatments, revealed that dung quantity and bulk grazing did not influence plant community diversity, though both strongly affected productivity and light availability. Horse dung promoted higher diversity compared to that of European bison or rabbits. Additionally, the effect of selective grazing on community diversity depended on the type of herbivore dung, whether that dung type promoted the dominance of certain plant species, and whether these species were selectively consumed or not. The main effect of herbivores in our experiment on the biodiversity of the plant community could be primarily ascribed to the herbivore species.
Our results shed new light on plant-herbivore interaction in terrestrial plant communities: They show that the dung of herbivore species varies not only in nutrient composition but also in microbial composition and that the activity of these microbes can influence plant-symbiotic associations, plant growth, and competition among plant species. The study also showed that dung quality differences among herbivore species may be just as important for plant community composition as the impact of herbivores through dung quantity or grazing activity. Hence, the maintenance and/or restoration of the diversity of herbivore species in natural ecosystems is of crucial importance for the maintenance of plant diversity and for the functioning of the ecosystem.
The objectives of this PhD study were to (i) determine and compare the dung microbial composition among some common European herbivore species (European bison, cow, horse, fallow deer, and rabbit), (ii) to investigate if the microbial activity in herbivore dung influences plant-symbiotic associations, plant growth, and plant species competition, and (iii) to investigate interactive effects of dung quantity, quality, and grazing activities of different herbivores on plant community composition.
Thereto we collected herbivore dung samples in a coastal dune ecosystem in The Netherlands (Kennemerduinen) and determined the nutrients and microbiome composition in it. We performed two mesocosm experiments in the greenhouse of the VUB: One investigating the effects of sterilized and unsterilized cow dung on symbiotic associations and growth of Trifolium pratense, and a second one investigating the effects of sterilized and unsterilized dung of European bison on growth and competition of 10 European grassland species. Finally, we set up and monitored a long-term mesocosm experiment in the VUB campus garden, investigating the interactive effects of the dung quantity and quality of rabbit, horse, and European bison as well as grazing activities (no grazing, selective grazing of legumes, bulk grazing) on the productivity and diversity of an experimental plant community (8 grassland species).
We identified differences in the nutrient composition and microbial communities in the dung of the five herbivore species and correlated these to differences in their diets and digestive systems. Sterilization of the cow and bison dung negatively affected nodulation (i.e., the activity of symbiotic N2-fixing bacteria) and growth of Trifolium pratense, and bison dung sterilization had species-specific effects on the competition between several legume species, including Trifolium pratense, and a few non-legumes, including Leucanthemum vulgare, with the grass species Anthoxanthum odoratum. Additionally, our outdoor mesocosm experiment, combined with various grazing treatments, revealed that dung quantity and bulk grazing did not influence plant community diversity, though both strongly affected productivity and light availability. Horse dung promoted higher diversity compared to that of European bison or rabbits. Additionally, the effect of selective grazing on community diversity depended on the type of herbivore dung, whether that dung type promoted the dominance of certain plant species, and whether these species were selectively consumed or not. The main effect of herbivores in our experiment on the biodiversity of the plant community could be primarily ascribed to the herbivore species.
Our results shed new light on plant-herbivore interaction in terrestrial plant communities: They show that the dung of herbivore species varies not only in nutrient composition but also in microbial composition and that the activity of these microbes can influence plant-symbiotic associations, plant growth, and competition among plant species. The study also showed that dung quality differences among herbivore species may be just as important for plant community composition as the impact of herbivores through dung quantity or grazing activity. Hence, the maintenance and/or restoration of the diversity of herbivore species in natural ecosystems is of crucial importance for the maintenance of plant diversity and for the functioning of the ecosystem.
Aantal pagina's: 194
Jaar van publicatie:2024
Toegankelijkheid:Embargoed