Objective To study the nutrient resorption characteristics of Pinus thunbergii under different densities (high density: 1150 plants·hm⁻², medium density: 535 plants·hm⁻², low density: 285 plants·hm⁻²)and the effects of leaves and soil nutrient contents and stoichiometric characteristics on the resorption efficiency, in order to provide a scientific basis for the rational management of Pinus thunbergii.

Method Taking Pinus thunbergii in the shelter forest of Muping coastal zone in Yantai as the research object, by collecting mature leaves, senescing leaves and soil samples of 0-20 cm under forest of Pinus thunbergii with different stand densities, the carbon (C), nitrogen (N), phosphorus (P) of leaves and soil, nitrate nitrogen (NO₃ ⁻-N), ammonium nitrogen (NH₄ ⁺-N), available phosphorus (AP) contents were determined, and researched the nutrient resorption characteristics of Pinus thunbergii at different densities, and analyzed the resorption of Pinus thunbergii leaves under different densities characteristics, leaves and soil nutrient contents, stoichiometric characteristics and their correlations.

Result （1）The average nitrogen resorption rate (NRE) and phosphorus resorption rate (PRE) were 52.44% and 48.53% in Muping coastal shelter forest. The NRE was similar as the average level of global coniferous forests, and the PRE was lower than the average level of global coniferous forests. Under the three densities, the growth and development of Pinus thunbergii were more restricted by N, which was consistent with the “relative resorption hypothesis”. （2）In the medium density area, the nutrient contents and resorption rates of mature leaves were the highest, and the NRE was significantly higher than high stand densities. The contents of C, N and P in mature leaves of Pinus thunbergii increased with the increase of density and then decreased, and the contents of senescing leaves were not significantly different among different densities. At medium density, C:N of mature leaves was significantly higher than that of low and high density; C:P of senescing leaves was significantly lower at low density. (3) Soil AP content was significantly higher in low-density forests; soil TN was significantly higher in medium-density forests; soil TP in high density stands was significantly lower than that in medium and low density stands. Soil C:N and C:P were significantly higher at high density, and at medium density, N:P was significantly higher than low and high density. (4) Nutrients and stoichiometric indicators of senescing leaves had more significant effects on nutrient resorption, and the responses of NRE and PRE to leaf and soil nutrients and their stoichiometric characteristics were different under different densities.

Conclusion In our experimental condition, Pinus thunbergii with medium density can relatively improve the nutrient utilization efficiency, which is more conducive to adapting to the N limitation in this area.