The paper studies the nutrient cycle of water resource protection forest of Pinus tabulaeformis in the Miyun Reservoir watershed. Results show that the total biomass of P. tabulaeformis stands at age 29 in the experimental area is 92 627 kg/hm2, the total nutrition storage of the nitrogen (N), phosphorus (P) , kalium (K), caliura (Ca) and magnesium (Mg) is 695.17 kg/hm2. The sequence of their contents in the different organs is as follows: needle > branch > trunk > root. Annual nutrient assimilation of five nutrient elements is 85.37 kg/hm2, is about 0.34% of the total storage, and is 3.30% of the available nutrient storage in the soil depth from 0 to 30 cm. The annual nutrient retention is 35.91 kg/hm2 , annual returning is 49.46 kg/hm2 and element from rain input is 26.04 kg/hm2. The absorption coefficient's sequence of five nutrient elements is as follows: N>P>K>Ca> Mg. Utilization coefficient's sequence of five nutrient elements is as follows: Mg >K>P>N>Ca. Cycle coefficient's sequence of the different nutrient elements is as follows :Ca> N>P>K>Mg. Turnover period of the different nutrient elements is as follows: Mg > K > P > N > Ca.
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