| Subalpine dark coniferous forest in Tibet is one of the relatively intact natural forests in China. Structure, biomass, productivity, hydrology and nutrient cycling were investigated in a P. likiangensis var. linzhiensis forest ecosystem in order to examine the mechanism of forming a high stock volume in the forest and provide the basic data of structure and functions of forest ecosystems in the high elevation area.There were 116 generas,53 families and 144 species of plants in the primary P. likiangensis var. linzhiensis forest in Tibet, in which Rosaceae and Asteraceae were dominant families. The community was composed mainly of temperate generas (76.14%), and generas and families with single species had a large proportion too. Species richness and diversity index were low, while the evenness and dominance index were high, indicating that the community was at the climax succession stage. The forest, with pitch and large diameter trees to be predominant, had a descending population growth. Analysis of the spatial point pattern showed that small diameter picea tended to have an aggregated distributed pattern in small area, and arbor was close to a random distribution pattern as growth. The gap makers of the forest based on large canopy gap with area of more than 100 m2 were mainly pitch diameter stem break. The main regeneration of the stands was middle gap, as regeneration amount and height growth of saplings of middle gap were 3.45 and 1.5 times that of the adjacent canopy respectively.Appropriately 80% of the biomass was accumulaited in the lower part of tree,86% of root biomass was concentrated in the 0～0.60 cm in the soil of standard wood of the primary P. likiangensis var. linzhiensis in Tibet. On the horizontal pattern, branch and leaf biomass in the open space was higher, but no difference in root in all directions. The total forest biomass was 367.49 t·hm-2, of which the tree layer consisted of the largest proportion (75.28%), followed by litter layer, the understory layer, dead wood, the shrub layer, interlayer plants (vines+moss), herb layer. The distribution of biomass in tree layer was ranked in the order of stem> root> bark> branches> leaves, and with the growth of trees, the proportion of stem and bark increased, while the branches and leaves the proportion decreased and the ratio of leaves and roots gradually reduced.The net primary productivity of the primary P. likiangensis var. linzhiensis forest in Tibet was 10.65 t·hm-2·a-1, in which tree layer had the most productive (46.96%), followed by understory layer, shrub layer, moss layer, herbaceous layer and the layer of plant. The law of productivity distribution of tree layer was ranked in the order of stem> branches> leaves> roots> bark. The diameter and height growth rate of the primary P. likiangensis var. linzhiensis forest was not synchronized. The whole growth process could be divided into the young, fast growing and fast-growing stable. The fast-growing period could be up to 100 years, coupled with the interference of non-toxic pest, and the accumulation of the P. likiangensis var. linzhiensis is very high.The annual precipitation in the primary P. likiangensis var. linzhiensis forest in Tibet was 716.4 mm, mainly occuring in the period from April to September. During the growing season, canopy interception was 338.6 mm, forest penetration of water was 316.3 mm, stem flow was only 0.9 mm. Litter average ply was 5.0 cm, maximum water holding capacity was 323.13%, the effective holding capacity is up to 92.26 t·hm-2, litter layer from top to bottom, water holding capacity decreased. Forest soil increased with depth, capacity increased, but the maximum water holding capacity, capillary water holding capacity and the minimum water holding capacity are gradually decreased, the same as soil capillary porosity and total porosity, it indicated that the water holding capacity of soil with depth increased gradually weakened. The nutrients in precipitation were lower. After passing through the canopy, SO42-, Zn, and Cl- concentrations in the throughfall decreased, while the other elements in the throughfall increased. After infiltration through the soil, SO42-, Zn and Fe concentrations decreased, while the other elements increased.Litter production in the P. likiangensis var. linzhiensis forest in Tibet was 3.40 t·hm-2·a-1, of which the amount of spruce branches and leaf litter consisted of 24.3%, 26.1%. Highest litter production occurred in the early and late growth of a year. When the sample bags was placed below moss, the decomposition rate was high. The initial decomposition rate and environmental temperature was linearly correlated. The leaf litter decomposed rate faster than twigs, and weight loss rate was 3 times higher after one year. The half-life of litter leaf decomposition was 1.75 years, while litter sticks were up to 8.08 years. With the decomposition time, K concentration in litter decreased fastest, after one year other nutrient elements decreased by nearly 1/2, but Ca concentration relatively increased in the middle process of decomposition. The nutrient release in the decomposition process differed significantly. For example, the release of K was 76.36%, while the release of Ca was only 24.01% one year later.The nutrient content was the lowest in stem of standard wood of the primary P. likiangensis var. linzhiensis forest in Tibet. While N, P, K elements in leaves were higher in the year. Accumulation of forest soil nutrient level was highest, but the effective utilization rate was only 1～3%. Nutrient was mainly accumulated in tree layer, in particular in dry wood, while the least was in leaves. Five nutrient element accumulation rate was 104.81 kg·hm-2·a-1, and the order was ranked as Ca> N> K> P> Mg, but the accumulation rate of each element vared in different organs of the tree layer. The total return amount of forest was up to 169.288 kg·hm-2·a-1, in which the return amount of litter was highest, followed by ground litter. The order of the return elements was ranked in the order of Ca> N> K> Mg> P.Carbon content were similar in different organs of the primary P. likiangensis var. linzhiensis. Carbon storage of ecosystem was up to 305.6 t·hm-2, which mainly came from the tree layer, accounting for 48.29% of the total, followed by the soil layer, accounting for 38.31%.Forest carbon sequestration rate was 3.58 t·hm-2·a-1,which the tree layer of the carbon sequestration rate was highest, accounting for 70.57% of the total carbon fixation rate.
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