Genetic variations and correlation analysis of N and P traits in Pinus massoniana under combined conditions of N deposition and P deficiency

Significant genetic variations in N and P nutritional traits exist under combined conditions of soil P deficiency and N deposition and interactively contribute to growth benefits. Forest ecosystems encounter combined conditions of soil phosphorus (P) deficiency and atmospheric nitrogen (N) deposition. As such, determining genetic variations and interactions of N and P nutritional traits is important for silviculture. Low N (LN) and high N (HN) were combined with three P treatments in a pot experiment with five full-sib families of Masson pine (Pinus massoniana). The three P treatments are: low P in soil profile (low-P condition, LP), enriched P in topsoil and poor P in subsoil (medium–low-P condition, MLP), and high P in soil profile (high-P condition, HP). P acquisition was more significant for growth benefits than P utilization under LP. Growth response to N was higher under MLP and HP than that under LP because of more balanced plant N:P ratios in the two former conditions. Under HN, there were significant correlation between nitrogen acquisition efficiency (NAE) and phosphorus use efficiency (PUE) and they interactively contributed to growth promotion under N deposition. Significant genetic variations, as well as large heritability of growth and N and P nutritional traits, were detected under all N–P conditions. This finding indicated the feasibility of breeding families with improved nutrient efficiency under N–P conditions.