INFLUENCE OF SOIL-TEMPERATURE ON ROOT COMPETITION IN SEEDLINGS OF ACER-RUBRUM, LIQUIDAMBAR-STYRACIFLUA AND SAPIUM-SEBIFERUM

Acer rubrum L. (red maple), Liquidambar styraciflua L. (sweetgum) and Sapium sebiferum (L.) Roxb. (Chinese tallowtree) seedlings were planted, two per pot, in pure and mixed species combinations. Pots were allocated to two soil temperature regimes: one with an average daily maximum and minimum of 31 and 21 C, and the other heated to a daily maximum and minimum of 34 and 31 C. Within pots, roots were allowed to commingle but shoots were separated to minimize competition for light. After 96 days, total mass of Liquidambar and Acer were not significantly affected by the species of competing plant or by soil heating. However, total mass of Sapium was significantly affected by an interaction of species and heat. When pots were heated: (1) growth of Sapium in interspecific competitive environments increased relative to growth in intraspecific pots; and (2) the competitive ability of Sapium in mixed species pots increased. Competitive responses were not clearly related to root surface area or root weight ratio.