川西亚高山人工林碳氮分配格局及其随凋落叶分解的释放规律

C and N allocation patterns in planted forests and their release patterns during leaf litter decomposition in subalpine area of west Sichuan

对四川西部亚高山地区连香树、糙皮桦、云南松和云杉4种主要人工林生态系统的生物量、土壤及林木器官C、N含量进行了测定.结果表明:林木体内C的分布与器官年龄的关系不明显,而N和C/N的分布与年龄的关系较为密切.幼嫩器官中的N含量大于老化器官,老化器官中的C/N比值大于幼嫩器官,且针叶林地枯落叶中的C/N比值大于阔叶林地.C、N在土壤表层具有明显的富集作用,在整个人工林生态系统(包括林木、枯落物和土壤0～40cm)中的积累量分别达176.75～228.05t·hm-2和11.06～16.54t·hm-2,在土壤-枯落物分室和林木分室中的分配比例为C(1.9～3.3)∶1,N(15.6～41.5)∶1,且针叶林的"C汇"功能大于阔叶林.阔叶林地的凋落叶分解速率一般大于针叶林地,周转期分别为2.2～3.7a和3.9～4.2a;在凋落叶分解过程中,C在所有林地均呈超速释出态势,周转期为1.9～3.4a;N在连香树和糙皮桦林地呈超速释出态势,周转期为1.9～3.2a,在云南松和云杉林地呈慢速释出态势,周转期为6.7～8.5a.

With the planted forest ecosystems of Cercidiphyllum japonicum, Betula utilis, Pinus yunnansinsis, and Picea asperata in subalpine area of west Sichuan as test objects, their total biomass and the C and N contents in soils and tree organs were determined. The results showed that the allocation of C in tree organs had less correlation with the age of the organs, while that of N and C/N ratio had closer relationship with the age. The N content in young organs was higher than that in aged ones, whereas the C/N ratio was higher in aged organs than in young organs, and higher in the leaf litters of needle-leaved forests than in those of broad-leaved forests. There was an obvious enrichment of C and N in the topsoil of test forests. The accumulated amounts of C and N in the whole planted forest ecosystem, including tree, litter, and 0-40 cm soil layer, were 176.75- 228.05 t · hm^-2 and 11.06-16.54 t · hm^-2, respectively, and the nutrients allocation ratio between soil-litter and tree was （ 1.9-3.3 ） ： 1 for C and （ 15.6-41.5 ） ： 1 for N. Needle-leaved forests functioned as a stronger “C-sink” than broad-leaved forests. The decomposition rate of the leaf litters in needle-leaved forests was larger than that in broad-leaved forests, with the turnover rate be- ing 2.2-3.7 years and 3.9-4.2 years, respectively. During the decomposition of leaf litter, the C in all of the four forests released at super-speed, with the turnover rate being 1.9-3.4 years. As for N, it also released at super-speed in C. japonicum and B. utilis forests, with the turnover rate being 1.9-3.2 years, hut released at low speed in P. yunnansinsis and P. asperata forests, with the turnover rate being 6.7-8.5 years.