Nutrient Variations and Their Use Efficiency of Pinus massoniana Seedling Tissues in Response to Low Phosphorus Conditions

Investigating the mechanisms by which plants adapt to low phosphorus content in ecosystems is crucial for nutrient dynamics division. Our study investigated the growth adaptation strategies of Pinus massoniana seedlings to low phosphorus conditions, including nutrient and non-structural carbohydrate (NSC) allocation, nutrient stoichiometry, and changes in nutrient resorption efficiency along a fact-based gradient. Our results showed that the total biomass and aboveground biomass proportion increased with substrate phosphorus content, reaching maximum biomass in the one-time phosphorus treatment. The nutrient concentration of components remained relatively stable, with the allocating preference to roots and needles under low phosphorus conditions. NSC was allocated as starch in fine roots and as soluble sugar in needles. Seedlings did not show signs of phosphorus limitation, even in the non-phosphorus group. The nitrogen resorption efficiency to phosphorus resorption efficiency ratio (NRE: PRE) of needles significantly varied between the high and low phosphorus treatments. In response to phosphorus deficiency, seedlings demonstrated homeostatic adjustments to maintain the relative stability of nutrient concentration. Fine roots and needles were prioritized to ensure nutrient uptake and photosynthetic product production. Additionally, it was necessary to differentiate the indicative function of nitrogen/phosphorus for various species and components, and NRE: PRE potentially provides a sensitive indicator of nutrient limitation status.