THE OCCURRENCE AND CONSEQUENCES OF GRASSHOPPER HERBIVORY IN AN ALPINEGRASSLAND, 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. Dur ing the 1993 growth period, grasshoppers removed between 19 and 30% of the aboveground phanerogam biomass. Herbivory impact was therefore fo und to be higher in alpine environments than that given in published e stimates of low elevation grasslands. Data on biomass as well as carbo n and nitrogen contents of herbage, grasshoppers, and feces were used to model the effects of herbivory on the Carer curvula community. Thir ty-six percent of the removed biomass was actually ingested by the gra sshoppers of which merely 3% was invested in body tissues. Since herbi vores did not emigrate from the site and predation was negligible, nit rogen consumed by grasshoppers remained in communities, while apprecia ble amounts of carbon were respired. Herbivory tends to accelerate nut rient turnover via concentration of nitrogen in rapidly decomposable b ody tissues and feces, as well as the production of ''green'' plant li tter originating from dropped plant material.