Competition under high and low nutrient levels among three grassland species occupying different positions in a successional sequence

To clarify the role of seasonal change, competitive response and nutrient a vailability in the competitive asymmetry of grassland species a competition experiment was conducted on Holcus lanatus, Anthoxanthum odoratum and Fest uca ovina, which represent a successional sequence of decreasing nutrient a vailability. Seven harvests were taken over two growing seasons. At each ha rvest the dry weight of plant parts, dead leaves, leaf area and plant heigh t were measured. Three key traits that determine the successional status of the species were studied: specific leaf area, specific shoot height, and d ead leaf fraction. The response of these traits to competition appeared to be limited and insu fficient to change the competitive relations in the experiment. However, al l three traits showed marked seasonal changes which resulted in superior gr owth and survival in winter of the species adapted to nutrient-poor environ ments. The findings support the theory that competitive asymmetry increases at higher nutrient levels. It is postulated that the directionality of lig ht makes it possible for the dominant species to monopolize this resource m ore easily than nutrients.