密云水库水源保护区板栗林主要养分元素生物循环研究

对密云水库北京集水区板栗林主要养分元素循环进行了研究。结果表明，22年生板栗林的生物量为38638kg·hm^-2；板栗林5种主要养分元素N、P、K、Ca、Mg贮存量为315．38kg·hm^-2，各器官中5种元素贮存量大小排序是干>枝>根>叶>花>果苞>果。板栗林生态系统乔木层每年从土壤中吸收的5种养分元素量为79．17kg·hm^-2，吸收量占0～30cm土层5种养分元素总量的0．15％,占0～30cm土层中5种元素有效养分量的1．95％。年吸收量中存留量为11．25kg·hm^-2，枯落物归还量为58．08kg·hm^-2。雨水及雨水淋溶输入到板栗林生态系统的养分元素量为38．63kg·hm^-2，果实输出量为9．84kg·hm^-2。雨水和雨水淋溶量与枯落物归还量之和大于吸收量，表明研究期间板栗林生态系统养分元素的收入略大于支出，5种元素的吸收系数排序为N>P>K>Ca>Mg，利用系数排序为K>N>Mg>P>Ca。循环系数排序为K>N>P>Mg>Ca。周转期排序是Ca>P>Mg>N>K。

Nutrient cycling in Castanea mollissima B1 forest at the Miyun Reservoir Watershed, Beijing

Studies on the nutrient cycling in Castanea mollissima B1 forest at the Miyun reservoir watershed, Beijing, showed that the total biomass of the Castanea mollissima B1 stands at age 22 was 38,638 kg.hm-2, and the biomass of their stem, branch, leaf, blossom, chestnut, seed capsule and root was 20,160, 8,430, 1429, 873, 1024, 800 and 5,922 kg.hm-2, occupying 52.18%, 21.82%, 3.70%, 2.26%, 2.65%, 2.07%, 15.33% of the total biomass, respectively. The annual average growth amount of stem, branch, and root was 916, 383, and 269 kg.hm-2, respectively, and the total annual average growth amount was 5,694 kg.hm-2. The nutrient contents in different organs of Castanea mollissima B1 stands showed that the N content sequence was leaf > blossom > chestnut > seed capsule > branch > stem, P content sequence was leaf > blossom > branch > stem > seed capsule > chestnut, K content sequence was chestnut > blossom > leaf > chestnut > branch > stem, Ca content sequence leaf > seed capsule > branch > stem > blossom > chestnut, and Mg content sequence was leaf > blossom > branch > chestnut > seed capsule > stem. The storage of N, P, K, Ca and Mg in Castanea mollissima B1 forest was 89.47, 17.34, 74.68, 105.49 and 28.40 kg.hm-2, respectively. The nutrient annual assimilation was 79.17 kg.hm-2, the total annual returning amount 106.55 kg.hm-2, and the annual retention amount was 11.25 kg.hm-2. Among of the total returning, atmospheric dry and wet deposition was 38.36 kg.hm-2, and the litter returning was 58.08 kg.hm-2. The nutrient input was a little more than the output. The storage of the five nutrient elements in 0(-)-30 cm soil layer was 206,427.59 kg.hm-2, and their storage amount in stands only occupied about 0.15% of the total storage in soil. The absorption coefficient of the stands was N > P > K > Ca > Mg, the utilization coefficient was K > N > Mg > P > Ca, and the cycling coefficient was K > N > P > Mg > Ca. The turnover period of the N, P, K, Ca and Mg was 4.34, 7.51, 3.31, 12.90 and 6.45 yr, respectively.