Growth and nutrient stoichiometry responses to N and P fertilization of 8-year old Masson pines ( Pinus massoniana ) in subtropical China

Background Masson pine ( Pinus massoniana) plantations are one of the most common forestry plantations in southern China. A high proportion of these plantations is managed as monoculture forests. Productivity in these plantations often declines as they age due to stand retrogression. In these plantations, fertilization is a key practice to prevent stand retrogression. Understanding how plants respond to nutrient fertilization at the tree and stand-level is crucial for evaluating the effects of fertilization and devising nutrient management strategies to prevent stand retrogression and to maintain plantation productivity. Methods To determine the effects of nutrient fertilization on plant growth and nutrient stoichiometry, we conducted a nitrogen and phosphorus fertilization experiment in an 8-year old Masson pine plantation in subtropical Hubei Province, China. Plant growth and nutrient stoichiometry responses to fertilization were determined over 12 months. Results Tree growth in height and trunk diameter and resorption efficiency of both N and P responded positively to N and/or P fertilization. Soil total P concentration was low (0.32 mg/g). Leaf N:P ratio was high and increased (>20) in N fertilization but decreased (<9) in P fertilization. Conclusions Our results show that Masson pine plantations of the study area are severely P limited, with low soil P concentration, high leaf N:P ratio, and positive growth responses to P fertilization. As the most common forestry plantations in subtropical and tropical China, P limitation is likely to be a widespread problem facing the Masson pine plantation industry. Thus nutrient fertilization of Masson pine plantations in comparable contexts should focus on P management.