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一、西藏亚高山暗针叶林的组成结构多为单优结构和云杉、冷杉的同型复合结构。在分布带内,阴坡下段多云杉纯林,上段多冷杉纯林;阳坡下段多云,冷杉与高山栎混交林,上段多冷杉,云杉与大圆柏混交林,最上段多方枝柏纯林。 二、云杉林和冷杉林均为复层林。圆柏纯林多为单层林。亚高山暗针叶林的林下层片较完整,并有1—2个层片发育良好而稳定。阴坡的下段多有发育极好的苔藓层,上段多亚乔木状的杜鹃下木层;阳坡下段多由箭竹组成的下木层。草木层一般不发达,层外植物发育良好。 三、亚高山暗针叶林分立木的年龄跨幅大,主林层的立木在200—300年以上,林下立木多在100年左右。暗针叶林立木的生长持续期长,200—300年以上仍继续生长,而林下立木有潜在的生长优势。 四、亚高山暗针叶林的立木径级分布幅度宽,树高差异大。在立地条件好的林分中,立木胸径多在60—100厘米以上,树高40—50米以上,最高可达70余米。林分中高大立木的比例和林分蓄积量的变化规律是:湿润区>半湿润区,阴坡>阳坡,低海拔>高海拔(分布区内),云杉林>冷杉林>方枝柏林,藓类林型>灌木林型>箭竹林型>杜鹃林型>草本林型>高山栎林型。 五、鉴于亚高山暗针叶林的结构特点,建议采伐时一律实引择伐,严禁皆伐,采伐胸径在50厘米以上,年龄在150年以上立木。
First, the composition of sub-alpine dark coniferous forests in Tibet is mostly single-superior structure and the same type of composite structure of spruce and fir. In the distribution belt, the lower part of the shady slope is pure cedar forest, the upper part of the fir forest; the lower part of the sunny slope, the fir and the alpine oak mixed forest, the upper part of the fir, spruce and dwarf the piedmont mixed forest, forest. Second, spruce forest and fir forest are multi-layered forest. Roundabout pure forest mostly monolayer. The understory of the sub-alpine dark coniferous forest is more complete and has 1-2 layers well-developed and stable. In the lower part of the shady slope there is an extremely well-developed moss layer, and the understory of the sub-arboreous cuckoo in the upper section; Grass and wood layers generally underdeveloped, well-developed plants. Third, the sub-alpine dark coniferous forest stands a large span of age, stand in the main forest of more than 200-300 years, standing more than 100 years in the forest. Dark coniferous trees grow long-lasting, growing more than 200-300 years, while standing undergrowth trees have potential growth advantages. Fourth, the sub-alpine dark coniferous forest diameter distribution range width, tree height differences. Stands in good conditions in the stand, standing more than 60-100 centimeters diameter breast diameter, 40-50 meters above the tree, up to 70 meters. The variation regularity and stand volume of stand tall and tall stands in the stand are: humid zone> semi-humid zone, shady slope> sunny slope, low altitude> high altitude (distribution area), spruce forest> fir forest> square branch Berlin, moss forest> shrub forest> bamboo forest> cuckoo forest> herb forest> alpine oak forest. V. In view of the structural characteristics of the sub-alpine dark coniferous forest, it is recommended that all cutting should be practiced at the time of harvesting, and the clear cutting should be prohibited. The cutting diameter should be above 50 centimeters and the age above 150 years.