The occurrence and consequences of grasshopper herbivory in an alpine grassland, Swiss Central Alps

Biomass removal by grasshoppers was determined nondestructively in two alpine grassland communities in the Central Alps at 2470 m a.s.l. During the 1993 growth period, grasshoppers removed between 19 and 30% of the aboveground phanerogam biomass. Herbivory impact was therefore found to be higher in alpine environments than that given in published estimates of low elevation grasslands. Data on biomass as well as carbon and nitrogen contents of herbage, grasshoppers, and feces were used to model the effects of herbivory on the Carer curvula community. Thirty-six percent of the removed biomass was actually ingested by the grasshoppers of which merely 3% was invested in body tissues. Since herbivores did not emigrate from the site and predation was negligible, nitrogen consumed by grasshoppers remained in communities, while appreciable amounts of carbon were respired. Herbivory tends to accelerate nutrient turnover via concentration of nitrogen in rapidly decomposable body tissues and feces, as well as the production of ''green'' plant litter originating from dropped plant material.