The effects of nutrients and physical land decimation on plant-herbivore interactions and food web dynamics in grasslands

Abstract

Plant damage through plant-herbivore interactions and the presence of phytopathogenic fungi is responsible for shaping community dynamics across numerous ecosystems. Interactions between plants, herbivores, and fungi encompass a fundamental relationship in generating animal biomass from light energy. Modern agricultural practices and the prevalence of fertilizer usage can modify these relationships through plant trait tradeoffs, where there has been an increase in growth-oriented traits at the expense of defense-oriented traits. To further complicate these interactions, avian predators, such as birds, can also modify these relationships through the regulation of insect herbivory. In this study, there are two experiments to examine these relationships. In the first, plant damage from herbivores and phytopathogenic fungi was recorded to observe if nutrient treatments had an impact on damage in two focal species, Rumex acetosella L. (Red sorrel) and Asclepias syriaca L. (Common milkweed). Treatments influenced damage from herbivory in both focal species but showed little evidence of their influence on fungi. In the second experiment, artificial caterpillars were employed to observe if avian predation was influenced by physical land disturbance and different types of artificial larvae. Both disturbance and the type of larvae influenced levels of predation. This study suggests an important linkage within the tripartite relationships between nutrients, plant-herbivore interactions, and predation. The importance of these interactions highlights the necessity of incorporating multi-factor approaches to make more effective predictions about the future.