秦岭南坡东段油松人工林生态系统碳、氮储量及其分配格局

Storage and allocation of carbon and nitrogen in Pinus tabuliformis plantations on the south slope of the East Qinling Mountains, China

研究秦岭南坡东段8、25、35、42和61年生油松人工林碳、氮储量和分配格局.结果表明：油松人工林不同林龄乔木层碳、氮含量为441.40-526.21和3.13-3.99 g·kg^-1,灌木层为426.06-447.25和10.62-12.45 g·kg^-1,草本层为301.37-401.52和10.35-13.33 g·kg^-1,枯落物层为382.83-424.71和8.69-11.90 g·kg^-1,土壤层（0-100 cm）为1.51-18.17和0.29-1.45 g·kg^-1.树干和树枝分别是乔木层的主要碳库和氮库,占乔木层碳储量的48.5%-62.7%和氮储量的39.2%-48.4%.林龄对生态系统碳、氮储量均有显著影响.生态系统碳储量随林龄增加而增加,35年时达最大值146.06 t·hm^-2,成熟后碳储量有所下降.5个林龄段油松林生态系统氮储量的最大值为25年时的10.99 t·hm^-2.植被层平均碳、氮储量分别为45.33t·hm^-2和568.55 kg·hm^-2,土壤层平均碳、氮储量分别为73.12和8.57 t·hm^-2,且土壤层中碳、氮的积累具有明显的表层富集现象.研究区油松人工林生态系统碳、氮储量主要分布在土壤层,其次为乔木层.生态系统碳储量空间分配格局为：土壤层（64.1%）〉乔木层（30.0%）〉灌草层和枯落物层（5.9%）,氮储量为土壤层（93.2%）〉乔木层（5.3%）〉灌草层和枯落物层（1.5%）.

The objective of this study was to study carbon and nitrogen storages and distributions in Pinus tabuliformis plantations along an age chronosequence of 8-,25-,35-,42- and 61-year-old on the south slope of the East Qinling Mountains,China. Results showed that the carbon content and nitrogen contents ranged from 441. 40 to 526. 21 g · kg^-1and from 3. 13 to 3. 99 g · kg^-1in arbor layer,from 426.06 to 447.25 g·kg^-1and from 10.62 to 12.45 g·kg^-1in shrub layer,from 301.37 to 401.52 g·kg^-1and from 10.35 to 13.33 g·kg^-1in herb layer,from 382.83 to 424.71 g·kg^-1,and from 8.69 to 11.90 g·kg^-1in litter layer,and from 1.51 to 18. 17 g·kg^-1and from 0. 29 to1.45 g·kg^-1in soil layer（ 0- 100 cm）,respectively. The largest carbon and nitrogen storages in arbor layer were trunks and branches,which made up 48.5% to 62.7% and 39.2% to 48.4% of the total storage,respectively. Carbon and nitrogen storages of P. tabuliformis plantations were obviously age-dependent. Carbon storage at first increased with stand age before the stand was ripe. It was the highest（ 146. 06 t · hm^-2） when the stand was 35 year-old,after which the carbon storage decreased. The nitrogen storage reached the peak value of 10.99 t·hm^-2at 25 year-old. The average carbon and nitrogen storages were 45. 33 t · hm^-2and 568. 55 kg · hm^-2in the plant layer and,73.12 and 8.57 t·hm^-2in soil layer,respectively. Moreover,carbon and nitrogen were accumulated at higher levels in the surface soil layer. In addition,the storages of carbon and nitrogen were mainly distributed in soil layer and arbor layer in this region. The average carbon storage in different components followed an order as soil layer（ 64.1%） arbor layer（ 30.0%） shrub-herb and litter layers（ 5.9%）,while the nitrogen storage followed as： soil layer（ 93.2%） arbor layer（ 5.3%） shrub-herb and litter layers（ 1.5%）.