LONG-TERM EFFECTS OF REPEATED N FERTILIZATION AND STRAW APPLICATION IN A JACK PINE FOREST .2. CHANGES IN THE ERICACEOUS GROUND VEGETATION

The cover of the ericaceous shrub Kalmia angustifolia L. in a jack pin e (Pinus banksiana Lamb.) forest was reduced after repeated fertilizat ion with N or N-P-K, or a single application of straw. Kalmia reductio ns were greatest in plots that received the highest total N loading (1 344 kg N . ha(-1)), but were also apparent in plots that received 672 kg N . ha(-1). The reductions could not be attributed to shading, sinc e tree volume response was small in the plots that received the highes t N loading. There was an overall reduction in the amount of ground ve getation in the fertilized plots, so the decline could not be attribut ed to increased competition from invading species. There was a general negative relationship between the abundance of Kalmia and N availabil ity in the forest floor, in fertilized and straw-amended plots. The re ductions in Kalmia cover were still apparent 14 years after the last f ertilization and 24 years after the straw application, as was higher N availability. Treatments such as repeated N fertilization or organic amendments that increase N availability in the forest floor may be an option for control of Kalmia in conifer plantations.