Distribution of carbon and nitrogen in forest floor components in Pinus radiata plantations of different ages in South Australia

Abstract

This study was conducted to evaluate the effects of plantation age on the distribution of carbon (C) and nitrogen (N) in forest floor components in radiata pine (Pinus radiata D. Don) plantations. Forest floor samples from plantations of three age classes (13-year-old; 27-year-old; 41-year-old) with various site qualities (II-VII) were collected from the Kuitpo radiata pine plantations in the Mount Lofty forest region of South Australia. The C concentrations of the forest floor components were significantly higher in the 41-year-old plantation than in the 13-year-old plantation, whereas the N concentrations were significantly lower in the 41-year-old plantation than in the 13-year-old plantation, except for the needle component. The C and N content of needles was significantly larger in the 13-year-old plantation than in the 41-year-old plantation, whereas fine woody materials, such as branches and bark, contributed less to the total C and N contents in the 13-year-old plantation. The total C content of the forest floor did not significantly differ with age, whereas the N content was significantly affected by age in the radiata plantations. The results reflect the existence of considerable variation in the quality and quantity of the C and N in forest floor components associated with different ages of radiata pine growing in sites of various qualities.