COS 126-6 - The resilience and resistance of different plant communities against different concentration of fungicide and parasiticide

Abstract: Anthropogenic chemicals are commonly used to control pests in agriculture, but these chemicals can negatively affect microbial community structure and nitrogen cycling of soil. According to the diversity/stability hypothesis, high diversity communities have greater resistance and resilience to disturbance than low diversity communities, but this hypothesis has rarely been tested with chemical application as the disturbance. We tested this hypothesis in a greenhouse experiment. We planted 600 pots with three different numbers of species but the same density, including pots with no plants, pots with one species (1 richness, 0 diversity, 100% evenness), low richness pots with three species (3 richness, 0.8 diversity, 33% evenness), and high richness pots with six species (6 richness, 1 diversity, 16% evenness). We treated pots with three concentrations of chemicals (low, medium, and high) commonly used in agriculture (Captan [fungicide] and Ivermectin [parasiticide]) and sampled the pots 0, 3, and 60 days after the application of chemicals. Ammonification and nitrification changed dramatically three days after application in all pots for both chemicals in high and medium concentrations. Sixty days following treatment, ammonification recovered to pre-treatment levels for both Ivermectin and Captan in high diversity pots better than low diversity, monoculture, and soil-only pots. Nitrification, however, only recovered in monoculture pots treated with low concentration of Ivermectin and low richness pots treated with high and medium concentrations of Captan after 60 days. Moreover, the abundance of microbial communities was affected by day, dosage, and interaction of day and richness in pots treated with Ivermectin. In pots treated with Captan, day, richness, and interaction of day and richness impacted the abundance of microbial communities. Our results suggest that high diversity communities can provide resilience for some functions of soil system, but that diversity cannot completely ameliorate the influences of anthropogenic chemicals.