密云水库流域油松水源保护林主要养分元素的生物循环

该文对密云水库北京集水区油松水源保护林主要养分元素循环的研究结果表明:29年生油松水源保护林的生物量为92.627 kg/hm2，油松林5种养分元素N、P、K、Ca和Mg的储存量为695.17 kg/hm2，各器官中5种养分元素储存量排序是针叶＞枝＞干＞根。油松林每年从土壤中吸收的5种养分元素量为85.37 kg/hm2，吸收量占0～30 cm土层中5种养分元素总量的0.34%、有效养分量的3.30%；年吸收量中存留量为35.91 kg/hm2，凋落物归还量为49.46 kg/hm2，降水输入的养分元素量为26.04 kg/hm2。5种养分元素的吸收系数排序为N＞P＞K＞Ca＞Mg，利用系数排序为Mg＞K＞P＞N＞Ca，循环系数排序为Ca＞N＞P＞K＞Mg，周转期排序是Mg＞K＞P＞N＞Ca。 

Nutrient cycle of water resource protection forest of Pinus tabuleaformis in the Miyun Reservoir watershed of Beijing

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/hm~(2),the total nutrition storage of the nitrogen(N),phosphorus(P),kalium(K),calium(Ca) and magnesium(Mg) is 695.17 kg/hm~(2).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/hm~(2),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/hm~(2),annual returning is 49.46 kg/hm~(2) and element from rain input is 26.04 kg/hm~(2).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.