Non-structural carbon, nitrogen, and phosphorus between black locust and chinese pine plantations along a precipitation gradient on the Loess Plateau, China

Abstract

No soil nutrient differences between two plantations. In contrast to NSC, N and P concentrations were greater in black locust than in Chinese pine. NSC negatively, N and P positively related to precipitation for both plantations. Precipitation is a key environmental factor affecting carbon (C), nitrogen (N), and phosphorus (P) status of plants and soils, especially in water-limited regions. However, there are potential differences among species in their sensitivity to C, N, and P in relation to variation in precipitation. We presented paired measurements of non-structural carbon (NSC), N, and P concentrations in plantations of N-fixing black locust (Robinia pseudoacacia L.) and coniferous Chinese pine (Pinus tabulaeformis Carriere) along a mean annual precipitation gradient on the Loess Plateau, China. The results showed that soil nutrients positively related to precipitation, but their differences between two plantations were not clearly visible. NSC concentrations of tree tissues were significantly greater in Chinese pine than in black locust. In contrast, the N and P concentrations and the N:P ratios were significantly greater in black locust than in Chinese pine. Leaves contained the highest N and P concentrations, whereas coarse roots contained the highest NSC concentrations. The lowest concentrations of NSC were in the stem wood. NSC concentrations were negatively related to precipitation, while N and P concentrations were positively related to precipitation for both tree plantations. The constant leaf N:P ratios indicated that the growth of Chinese pine was limited by the soil N supply, whereas black locust was limited by P. These results indicate that inherent physiological and biological processes differ with tree species, and when coupled with environmental conditions, influence the variations of C, N, and P in plant tissues to adaptation and resilience under drought stress.