Determining the "optimum" slash pine seedling size for use with four levels of vegetation management on a flatwoods site in Georgia, U.S.A.

Abstract

A slash pine (Pinus elliottii Engelm. var elliottii) study was established to determine the "optimum" seedling size for use on a flatwoods site in the Coastal Plain physiographic province of Georgia, U.S.A. The optimum seedling is defined as the ideotype that will minimize overall reforestation costs while achieving established goals for initial survival and growth. Initial survival and fourth-year performance were examined in relation to (i) method of site preparation, (ii) herbicide application, and (iii) seedling class (based on root-collar diameter) and to associated establishment costs. Seedling class greatly influenced survival with large-diameter classes (8.5-11.5 mm) exhibiting the best survival (87-99%). Seedlings with 4.5-mm diameters averaged 75% survival. A second bedding pass (double bedding) reduced grasses and woody shrubs, and the herbicide imazapyr reduced grasses and herbaceous broadleaf weeds. Neither treatment improved pine survival. Use of 9.5 to 11.5-mm seedlings (without double bedding) produced larger trees 4 years after planting than 4.5-mm seedlings with double bedding. A simple cost analysis indicated the optimum seedling would be considerably larger (9.5-11.5 mm) in diameter than the "target" seedling (4.5 mm) typically produced at slash pine nurseries. For each dollar invested in establishment, planting the optimum pine seedling on this site resulted in greater gains in early survival and growth than either double bedding or use of imazapyr.