Field trials of nitrogen (N) and phosphorus (P) fertilization in loblolly pine plantations (Pinus taeda L.) were used to determine the effects of fertilization on within-crown leaf area distribution in a fully stocked stand, and two less than fully stocked stands. A second objective was to examine the utility of the Weibull distribution for modeling leaf area distribution in loblolly pine crowns. Results showed that leaf area increases were most evident in the mid- and lower-crown positions (2-4 m and 4-6 m crown depths), regardless of stocking level. Response patterns suggested that the Westvaco Stocking Chart, which is based on empirical relationships between stand basal area, stand density, and canopy closure, did not adequately reflect light interception in these stands because stands were ranked differently when stocking was expressed by stand leaf area index. The fully stocked stand was 50% below the theoretical optimum leaf area index value of 5. Thus, it is hypothesized that leaf area increases occurred in the mid- and lower-crown because shading in the mid- and lower-crown positions was insufficient to inhibit foliage production and survival. Fertilization-induced changes in leaf physiology may have also played an important role in leaf production and branch retention in the mid- and lower-crown. The Weibull distribution provided a good fit of within-crown leaf area distribution. For. Sci. 34(3):564-573.
Research Ecologist, USDA Forest Service, Coweeta Hydrologic Laboratory, Otto, NC, USA, 28763
Publication date: September 1, 1988
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Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.