Pinus radiata forest floors: Factors affecting organic matter and nutrient dynamics

Abstract

Forest floor organic matter and nutrient contents were quantified in 41 first-rotation and seven second-rotation stands of Pinus radiata D. Don (radiata pine) growing in the North Island. Most of the stands were between 18 and 21 years of age. The forest floors contained an average 20.7 tonnes of organic matter/ha and 258, 18, 32, and 33 kg/ha of nitrogen, phosphorus, potassium, and magnesium, respectively, but there was considerable variation both between and within forests. Ridge and stepwise multiple regression techniques were used to construct models which explained 70, 58, 62, 79, and 82 % of this variation. Stocking levels, rainfall, minimum temperature, and foliage calcium levels were the most important variables. The second-rotation sites contained on average twice as much organic matter and nutrients as the first-rotation sites. This was attributed to the fact that no slash burning or clearance had been carried out at the end of the previous rotation. The forest manager can thus make significant changes to forest floor dynamics through policies on thinning and slash treatment.