Traits associated with competitive abilities of 12 wetland species along successional and nutritional gradients.

摘要

Long-lived leaves are generally considered to be an adaptation to unproductive habitats as they minimize resource losses. Based on some evidence in the literature, however, I hypothesize that in the absence of disturbance, long-lived leaves pose an advantage for a species also in productive environments. I also hypothesize that plant height is an important trait for competitive ability especially in productive environments. Previously, height of an individual plant has been described to be important for its competitive ability, but height has been neglected as an adaptive trait in comparative ecology. Using 12 herbaceous perennial wetland species, I conducted a garden experiment to investigate the association between interspecific variations competitive ability and in leaf longevity and plant height at high and low nutrient supply (10-fold difference) along a short successional gradient (2 years). Tillers were planted in 18-liter pots in summer 2004. Species abundance in mixtures and monocultures was assessed monthly during the growing seasons of 2005 and 2006. The competitive ability of the species, characterized by the ratio of mixture to monoculture abundances, assessed using a pin-frame, was related to plant height in monocultures at both nutrient levels but there is some indication that this relationship is more pronounced at high nutrient availability. Leaf longevity was associated with an increase in the species' competitive ability along the successional gradient at both nutrient levels. I conclude that interspecific variation in leaf longevity should primarily be seen as an adaptation to variation in habitat disturbance, not in productivity as usually assumed. The adaptive nature of interspecific variation in height should be emphasized more than currently is the case in ecological theory.