| Presently in China, cultivation of artificial forests has become an important content in forestry development. Artificial forest cultivation is not only a necessary measure for protecting natural forests, but also an effective way to produce timber. What are the impacts the scaled artificial forests imposed on ecological environment? Detailed studies were urgently needed.This study choosing Puwen experimental forest farm located at north part of Xishuangbanna as study site, which is the transition from typical tropical seasonal rain forest to montane monsoon evergreen broad-leaved forest, the artificial community of 13 years old Betula alnoides was selected as the study target, taking zonal vegetation type montane rain forest and Betula alnoides natural secondary forest as the control, adopting the methodology including field plot sampling, laboratory experiments and statistical analysis, comparative study was conducted from community characteristics, soil physical and chemical properties, community biomass, net primary productivity and carbon storage. The main results and conclusions are as follows.1) Species composition and physical characteristics of Betula alnoides plantation were closely related with the site status before planting. The Betula alnoides plantation coded I (BAP1) established on the cutting blank of montane rain forest had abundant diversity of the species and fast succession progresses). Totally 109 species (belong to 59 families and 92 genera) of vascular plant were recorded, which significantly exceeded those of Betula alnoides plantation codedⅡ(BAP2) (60 vascular bundle species,33 families, and 56 genera) and Betula alnoides natural forest (BANP) (55 vascular bundle species,30 families, and 52 genera) established on secondary forest cutting blank. Moreover, very abundant species composition (61 species) of shrub layer of was recorded in BAP1. The plant species'Jaccard similarity coefficient of BAP1 and tropical montane rain forest (TMRF) was 24.68%, characterized similar morphology and convergent character to a certainty.2) In Betula alnoides community in Puwen of Xishuangbanna, the tropical elements were dominant, characterized by the transition from tropical Asia to east Asia. With the succession progress, the tropical distribution elements present increasing trend. Dominated by areal types 2-5, it was obvious that the flora of Betula alnoides plantation in Puwen is of tropical in nature, characterized by absence of representative tropical distributed families. With the succession progress, the tropical distribution elements present increasing trend while temperate distribution elements decreasing. 3) Choosing pioneer tree species such as Betula alnoides, is helpful for the quick restoration of both structure and function, and speeding up of succession to zonal vegetation type. Comparing with TMRF,13 years old Betula alnoides plantation did not show obvious layer differentiation, with only one tree layer of the species of Betula alnoides. However, the components of shrub layer, grass layer and lianas were all well developed, the species richness, diversity index and evenness index of BAP1 were higher than TMRF. As the succession progresses, the tree species presently in shrub layer such as Phoebe lanceolata, Machilus rufipes, Castanopsis echidnicarpa, Castanopsis hystrix, Castanopsis calathiformis, Dysoxylum binectariferum, Manglietia forrestii, Garcinia cowa, Altingia excels, Memecylom polyanthum, Choerospondias axillaries, Syzygium szemaoense, will further differentiate, promote the complication of structure and finally form multi-layer trees. Simultaneously, with the development of shrub, grass layer litter, the speed of matter cycle and energy flow in Betula alnoides plantation will further be increased, the function of community will be improved from both plant abundance and productivity, which is necessary for further community succession.4) Restoration of soil fertility was synchronous with the succession of plant community, the physical and chemical characteristics of soil in Betula alnoides communities established from different sites varied significantly. The basic indexes of Betula alnoides plantation coded I, namely organic matter, total N, valid N, total P, valid P, available K, were 22.62 g.kg-1,1.40 g.kg-1,243.87 g.kg-1,36.30 g.kg-1,0.56 g.kg-1,159.89 g.kg-1, these values were significantly higher than Betula alnoides II and natural Betula alnoides forest. The bulk density and general porosity of surface soil in Betula alnoides coded I plantation were 1.235 g.cm-3 and 52.381% respectively, which was better than BAP2 and BANF. In surface soil of Betula alnoides plantation coded I, the contents of sand, silt and clay were 17.526%,22.136% and 13.921% respectively, which were close to those of montane rain forest,25.704%,31.067% and 24.948% respectively.5) As the succession progressing and the improvement of community structure, the correlation between different soil nutrients became closer, and the soil fertility gained gradual recovery. Among all the three plant communities studied, BAP1 showed the best performance in nutrient correlation, except for the correlation between available P and other nutrients with the correlation coefficients ranged from 0.285 to 0.581. the correlation coefficients of other nutrients were higher than 0.5. As far as BAP2 was concerned, only organic matter and total N had significant correlation with other nutrients. The nutrient correlation of BANF was the poorest, only organic matter showed the significant correlation with other nutrients. 6) Insufficient available Phosphorous and too acid soil were two restriction factors to the soil fertility of Betula alnoides plantation. P application and soil pH improvement were propitious for quick development of community. The contents of available P of three studies Betula alnoides communities ranged from 0.42mg-kg-1—1.07mg·kg-1 only, while soil pH values were 3.92—4.78. Available Phosphorous was easily fixed by soil. P application and soil pH improvement were necessary to health development of Betula alnoides plantation.7) In the early stage, as the progress of succession, the biomass of tree layer, shrub layer and litter showed the tendency of rapid growth, while that of grass layer showed the tendency of decrease. With development of tree layer and shrub layer, the biomass of grass layer was decreased due to the enhancement of canopy density.8) Betula alnoides plantation had promising biomass, net primary productivity and carbon fixation capability, timely tending and thinning were benefit for sustained increase of volume, so as to increase the ecological benefit of Betula alnoides plantation. The biomass of BAP1 and BAP2 were 108.31t/hm2 and 83.62t/hm2 while the net primary productivity were 19.99 t/hm2·a and 11.1 t/hm2·a, and the annual carbon fixation were 3.87t/hm2 and 3.07 hm2 respectively. With the development of Betula alnoides plantation, competition among water, light, and fertilizer will be stronger. Tending and thinning were necessary to volume increasement and structure optimization.9) In the early stage of succession, the physical properties in surface soil layer showed the tendency of degradation first and then recovery, tending was a very critical measure in management of young Betula alnoides plantation.
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