PARENT SESSION
Oral Session #43: Soil Ecology: Mycorrhizae and Roots. Presiding: W. Stock.
Wednesday, August 8, 2001. 8:00 AM to 12:15 PM. Hall of Ideas F.

Distance-dependent effects of soil pathogens on Prunus serotina seedling growth .

Packer, Alissa¹, Clay, Keith¹, ¹

ABSTRACT- Negative feedback between plant and soil communities can cause plants to experience higher mortality and decreased growth in soil cultured by conspecifics. We previously demonstrated that Prunus serotina seedlings experience distance- and density-dependent mortality near conspecific trees. Here we examined whether seedling growth is affected by distance to conspecific trees. Black cherry seedlings and saplings were followed in the field for one to three years before above and belowground biomasses were measured. Regression models including distance, density, and seedling age explained 13.2% of the variation in total biomass. Distance and age were positively correlated with total biomass and root-to-shoot ratio, while density was negatively correlated with both variables. A similar model for saplings explained 10.6% of the variation in total biomass, with distance again being positively correlated with total biomass. Seedlings were grown under greenhouse conditions at high and low density, in soil collected 0-5 m or 25-30 m from adult cherry trees. Half of the soil collected at each distance was sterilized. Sterilization affected growth of surviving seedlings (N=30, Pillai's trace=0.988, F=1450.5, p<0.001). Stem and root weights were higher in sterile soil than in unsterile soil. Pythium spp. isolated from roots of dying seedlings and used to inoculate healthy seedlings decreased biomass of survivors. These results provide evidence that native soil-borne pathogens inhibit plant growth in a distance-dependent manner, potentially decreasing an individuals' chance of survival at later stages.

KEY WORDS: soil pathogens, Prunus serotina , distance-denpendent growth