Species Composition and Standing Crop Variation in an Unfertilized Meadow and Its Relationship to Climatic Variability during Six Years

Year-to-year variability of species composition and hay yield were investigated during a six-year period (1988-1993) in a traditionally mown meadow of great species richness at Negrentino in southern Switzerland. Climatic parameters (temperature, duration of sunshine, global radiation, precipitation, evaporation, relative moisture) measured at a nearby weather station were calculated for ten-day units and compared to quantitative vegetation data. Yields of the first and second harvest were positively correlated with the mean relative moisture during the first and second growth period. Distinct variation patterns were recognized among the 48 species and interpreted as direct or indirect responses of interacting species to climatic conditions during three periods of the year. The first variation pattern including abundant graminoids reflects a strong direct effect by weather conditions in the first growth period. Species of the other variation patterns responded differently to extreme summer droughts with apparent time-lags. Some species reflect warm and humid conditions in early spring followed by dry conditions in a particular year; others combine features of different variation patterns.