DECOMPOSITION AND NUTRIENT RELEASE FROM MIXTURES OF GAMBEL OAK AND PONDEROSA PINE LEAF LITTER

Studies were carried out to test the hypothesis that decay and release of nutrients of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) is accelerated in litter mixtures with Gambel oak (Quercus gambilii Nutt.). Litterbags containing different proportions of pine needles and oak leaves were placed in pine stands and collected over a 2-year period. At the end of the experiment mass losses from pure oak were 60% higher than those from pure pine with no evidence that the intrinsic rate of dry matter loss was affected in mixtures of litter. Litter type significantly influenced the concentration of all nutrients studied and amount of nutrients remaining for all nutrients except N and Ca. Increasing amounts of oak caused N, S, Ca and Mg to be retained more so than in 100% pine litter. Relative mobility of K and P were unaffected by litter composition. Nutrient release patterns were similar for N, S and Ca with little or no loss over the study period. Nutrient release patterns for P, Mg and K were similar with marked release (56 to 82% loss) over the two-year period. Possible reasons for lack of a synergistic effect between pine and oak are discussed.