The Effect of Competition and Nutrient Availability on the Growth and Reproduction of Ipomoea Hederacea in an Abandoned Old Field

(1) Ipomoea hederacea, a common weed in cultivated fields of eastern North America, disappears quickly following abandonment of farming. (2) The effects of competition and nitrogen addition on the growth and reproduction of I . hederacea were studied during the first year of abandonment. (3) Competition and fertilization had significant absolute effects on almost all biomass variables measured and few affects on the same variables when they were expressed as percentages of total biomass. (4) Plants in a fertilized and cleared plot were larger and produced more seed than plants from two other treatment plots and the control plot. Plants in an unfertilized and cleared plot were similar to plants in a fertilized plot which had not been cleared. Plants in a plot which was neither fertilized nor cleared were smaller and produced very few seeds compared with plants in the three treated plots. ( 5 ) The results suggest that I . hederacea is eliminated during succession because it is a poor competitor for nitrogen, and that the main result of the competition is a reduction in below-ground biomass.