Effects of nutrient enrichment on the Auchenorrhyncha (Homoptera) in contrasting grassland communities.
Auchenorrhyncha were sampled from control, fertilizer- and sewage sludge-treated plots within an agricultural field (annual wheat field) and a field which had been left undisturbed for 4 years (perennial grassland meadow) in Ohio in 1978. Nutrient enrichment significantly increased net primary productivity in both plant communities. Functional plant community properties (e.g., net primary production) were more robust indicators of nutrient enrichment than were structural properties (e.g., plant species diversity). Nutrient-enriched plots generally exhibited higher Auchenorrhyncha population densities than control plots in both community types; differences were more frequent in the more mature old-field community. Changes in Auchenorrhyncha density and diversity were attributed to changes in plant composition, productivity and probably plant quality and vegetational architecture. Auchenorrhyncha within the more mature old-field community exhibited a greater response to nutrient subsidy than within the agricultural community; these differences were attributed to plant-insect life-history characteristics.