The relationship between foliage color and foliar nutrient levels in loblolly pine

Several loblolly pine plantations in which a wide range of color grades existed between yellow and green were selected to code the range of colors found in loblolly pine foliage and to test for a relationship between foliage color, as coded by the Munsell classification system, and foliar nutrient levels. Plantations sampled were north of the native range of loblolly pine, largely those planted on severely disturbed sites, e.g., surface mine spoil, eroded old fields, and highway cuts and fills. Foliage samples were coded into six discrete Munsell colors. Seventy-five percent of all samples were from the "yellow" end of the spectrum, hue 2.5 GY. On the "green" end of the spectrum, color shifts were largely the result of changes in hue with little change in value and none in chroma. In general, nutrient means were positively correlated with Munsell color and hue, and negatively correlated with value and chroma. Munsell color.codes might be useful in determining foliar N and P since statistically significant grouping of means were identified for these two nutrients. Small positive R-squares between both foliar N and P and hue, as compared to larger R-squares for value and chroma, suggest that increasing blackness and grayness are more strongly associated with high levels of N and P than is absolute color.