PARENT SESSION
Oral Session #19: Plant Competition. Presiding: N. Slade.
Monday, August 6, 2001. 1:00 PM to 5:15 PM. Hall of Ideas J.

Linking plant traits to interspecific interactions using path analysis.

Peltzer, Duane¹, Wardle, David¹, ¹

ABSTRACT- An unresolved issue in ecology is what characteristics or traits of plant species can be used to predict their competitive or facilitative abilities. Several authors have predicted which plant traits should be linked to success in interspecific interactions, but few studies to date have explicitly tested the predicted linkages between plant traits and success in interspecific interactions. Here, we use a path analytic approach on a species x trait matrix of 20 herbaceous species x 14 plant traits (Wardle et al. 1998) to test various predictions about which traits should confer competitive or facilitative abilities of plants. Data used for this project are drawn from a study quantifying ecophysiological characteristics of 20 herbaceous dicotyledonous plants from New Zealand grasslands. Responses of the 20 plant species to the presence of a common species of grass, Lolium perenne, were generally improved by increased time to reproduction and were negatively related to root length to weight ratios, suggesting that plants having fine roots were more strongly suppressed by Lolium. In a second experiment in which the effects of the 20 species on Lolium performance were examined, suppression of Lolium was driven by high tissue N concentrations in rosette plants, high root length to weight ratios for flowering plants, and shoot morphology for senescing plants. Allocation of nutrients to reproductive structures reduced the suppressive effects of plants on Lolium during flowering, but increased their effects after senescence, suggesting that different plant traits may be important in interspecific interactions throughout a plant's life history. Taken together, these results support the idea that traits related to resource capture confer the ability to suppress neighbours whereas traits relating to the persistence or longevity of plant tissues allow plants to avoid suppression by neighbours.

KEY WORDS: plant traits, interspecific interactions, path analysis, comparative approach