PONDEROSA PINE NEEDLE LENGTH - AN EARLY INDICATOR OF RELEASE TREATMENT EFFECTIVENESS

Growth responses of ponderosa pine seedlings range from fast to slow after release and often demonstrate the effectiveness of the prescribed treatments. Although several morphological parameters have been identified as being sensitive to competition, no link to future growth and treatment effectiveness has been made. Shrubs and grasses in four 1- to 3-year-old ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa) plantations in northern California were treated by several manual and chemical release techniques that resulted in differing amounts of competition to ponderosa pine seedlings. Differing amounts of competition in tum affected pine growth and led to a wide range of stem heights, diameters, and needle lengths. Correlation coefficients indicated that 1-year-old needles, measured 2-4 years after treatment, were positively associated with pine height and diameter up to 7 years after treatment and potentially beyond. Consequently, length of 1-year-old needles may provide a useful early indication of longer term treatment effectiveness.