Habitat heterogeneity can influence arthropod abundance, diversity, and composition through its effects on biotic and abiotic factors. Because plant biomass and diversity are often correlated with arthropod abundance and diversity, manipulating the plant community by adding nutrients or altering vegetation structure should have a cascading effect on the arthropod community. We explored how habitat heterogeneity and plant quality act together to regulate grassland arthropod communities. To do this, we manipulated both habitat heterogeneity (using three vegetation clipping treatments) and plant biomass and nutrient availability (using NPK and micronutrient fertilization). From May through August 2017, we monthly quantified how these treatments affected plant biomass, plant C:N ratios, and microclimate. We also collected arthropods using vacuum sampling and pitfall traps to measure arthropod abundance, diversity, and richness.
Results/Conclusions
We found that both clipping and fertilization treatments affected plant biomass and microclimate, including light availability, temperature, and humidity. By decreasing plant biomass, clipping simplified habitat structure and reduced arthropod abundance (P < 0.0001), diversity (P = 0.011), and richness (P < 0.0001). This reduction appeared to be mediated by fertilizer addition, which increased plant biomass and habitat volume (P < 0.0001), resulting in lower average surface temperature (P < 0.0001) and higher average humidity (P = 0.001) on plots. By itself, increasing plant biomass through fertilization increased arthropod abundance (P < 0.0001) and richness (P = 0.0001). In addition, we show the indirect effects of changing microclimate and plant biomass promoted shifts in arthropod community composition. These results demonstrate the role of habitat heterogeneity and plant quality in structuring arthropod communities, specifically by regulating microclimate and providing habitat space.