Growth, nutritional status, and nonstructural carbohydrates of Armand pine (Pinus armandii) seedlings in response to fertilization regimes and levels

ABSTRACT Exponential fertilization has been regarded as an important technique for improving seedling growth and enlarging internal nutrients reserve. However, the effects of exponential fertilization under varying fertilization levels on seedlings’ growth, nutritional status, and nonstructural carbohydrates (NSC) are poorly understood. We employed Armand pine (Pinus armandii) seedlings to investigate the responses of growth, nutrients (nitrogen, phosphorus, and potassium) in seedlings, and NSC in organs to varying exponential and conventional fertilization levels. Shoot height, root collar diameter, and biomass increased and then declined with the increased fertilization levels. At high fertilization levels (≥300 mg seedling−1), the seedings accumulated more biomass in exponential fertilization than in conventional fertilization. The exponentially fertilized seedlings contained more concentrated nitrogen, starch, and NSC than the conventionally fertilized ones. Vector analysis revealed that conventional fertilization of 200 mg seedling−1 or exponential fertilization of 300 mg seedling−1 could induce luxury consumption. NSC was closely related to the nutrient states. With the increased fertilization level, regardless of the regime, soluble sugar concentrations in roots and needles trended toward declining with changes in the nutrient supply from deficiency to sufficiency and then increased with the changes from sufficiency to toxicity. Meanwhile, starch and NSC concentrations in roots and needles increased with the changes in the nutrient supply from deficiency to sufficiency; the concentrations in roots decreased with the changes from sufficiency to excess. Exponential fertilization at high levels did not only promote seedling growth but also induced seedlings to reserve more nutrients and NSC, which could improve afforestation success.