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

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0～40 cm)中的积累量分别达 176.75～228.05 t·hm^-2和 11.06～16.54 t·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2.2～3.7 a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1.9～3.4 a；N在连香树和糙皮桦林地呈超速释出态势，周转期为1.9～3.2 a，在云南松和云杉林地呈慢速释出态势，周转期为6.7～8.5 a.

Effects of nitrogen fertilization on fine root biomass and morphology of Fraxinus mandshu-rica and Larix gmelinii: A study with in-growth core approach

With the planted forest ecosystems of Cercidiphyllum japonicum, Betula utilis, Pinus yunnansinsis, and Picea asperata in subalpine area of west Sichua n as test objects, their total biomass and the C and N contents in soils and tre e organs were determined. The results showed that the allocation of C in tree or gans had less correlation with the age of the organs, while that of N and C/N ra tio had closer relationship with the age. The N content in young organs was high er 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 i n 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 pla nted forest ecosystem, including tree, litter, and 0〖KG-*2〗-〖KG-*7〗40 cm soil layer, were 17675〖KG-*2〗-〖KG-*7〗22805 t·hm-2 and 1106〖KG-*2 〗-〖KG-*7〗1654 t·hm-2, respectively, and the nutrients allocation rat io between soil-litter and tree was (19〖KG-*2〗-〖KG-*7〗33)∶〖KG-*2〗1 for C an d (156〖KG-*2〗-〖KG-*7〗415)∶〖KG-*2〗1 for N. Needle-leaved forests functioned as a stronger “C-sink” than broad-leaved forests. The decomposition rate of the l eaf litters in needle-leaved forests was larger than that in broad-leaved fore sts, with the turnover rate being 22〖KG-*2〗-〖KG-*7〗37 years and 39〖KG -*2〗-〖KG-*7〗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〖KG-*2〗-〖KG-*7〗34 years. As for N, it also released at super-speed in C. japonicum and B. utilis forest s, with the turnover rate being 19〖KG-*2〗-〖KG-*7〗32 years, but released a t low speed in P. yunnansinsis and P. asperata forests, with the turnove r rate being 67〖KG-*2〗-〖KG-*7〗85 years.