Studies On Container Seedling Production And Afforestation Techniques Of Conifer Tree Species

In combination with the implementation of the National Land Conversion Program, the studies on container seedling production and afforestation techniques of conifer tree species were systematically conducted and have achieved the following results: 1) Study on different-dimensioned containers: through comprehensive analysis and evaluation of morphological index, biomass index and economics of seedlings from 9 different-dimensioned containers, it was found that the container of 4×14cm dimension is the most suitable size for producing Pinus tabulaeformis container seedlings. 2) Study on different-thickness containers: based on the analysis of each index of seedling production of different thickness container, it was found that root collar diameter of seedlings from 0.03mm thick container was much significantly bigger than those of seedlings from 0.015mm thick container, and was significantly bigger than those of 0.02mm thick container. It is recommended to use polythene container with 0.03mm thickness to produce container seedlings. This type of container also has advantages that soil medium is easily filled into container, thus saving labor input, and the container is more endurable during its transportation. 3) Study on different types of containers: the container bag with bottom helps root development, increase of root number and formation of root ball, and also produces better quality of seedlings. Compared with bottomless container bag, container bag with bottom has advantages that soil medium is easily filled in, and root ball stands more stable during its lifting and transportation, helping protection of seedling system from mechanical injury which may otherwise decrease seedling quality. Punched container bag helps air ventilation, water penetration, temperature regulation and increasing rooting rate of seedling root and root system development as well. Container bag should be bottom punched. 4) Study on soil medium of container: study of 8 different soil medium compositions shows the optimal soil medium composition for Pinus tabulaeformis container seedling production in Weibei Dryland Belt of Shaanxi Province is acid soil with pH=6.3, which consists of 40% of top soil, 15% of loess soil, 20% of humus soil on forest floor, 20% of decomposed manure and 5% of stove ash, with neutral loamy soil texture, bulk density of 10g/cm~3, total phosphorus of 0.8g/kg, rapidly available phosphorus of 90mg/kg, rapidly available potassium, alkaline hydrolysable nitrogen of 112 mg/kg, and organic matter content of 3.4%. 5) Study on fertilization: response-to-fertilization model was established, and it is recommended to have twice applications of fertilizer for Pinus tabulaeformis seedling production, i.e. late May and mid-July. The optimal amount of fertilizer applied is 0.16-0.22g/tree for N fertilizer and 0.01-0.04g/tree for P fertilizer. 6) Disease control techniques of conifer species nursery: the control techniques for controlling damping-off disease of Pinus tabulaeformis seedlings are summarized as follows: a) in the preparation of soil medium, organic manure should be well decomposed, grinded and screened to reduce soil bulk; b) careful selection of seeds prior to their sowing, and rotten and bad seeds should be removed; c) prepared soil medium should be completely disinfected with ferrous sulfate or formaldehyde solution; d) seeds should be disinfected with 0.5% potassium permanganate solution; e) 7 days after seedling emergence, 0.5% ferrous sulfate solution is sprayed once on seedlings; f) timely watering with water penetrating into deep soil. During high temperature weather, timely cooling down the temperature and maintaining a good aeration in the greenhouse; g) Study on afforestation of container seedlings: planting of one-year-old Platycladus orientalis seedlings and two-year-old Pinus tabulaeformis seedlings in Weibei Dryland Belt had best afforestation results. Use of container conifer seedlings in afforestation on very difficult sites could largely increase planting survival rate and preserved rate, and is an effective measure for drought-resistant afforestation in this area. Container conifer seedlings should be watered 3-4 days prior to their lifting which would have soil moisture contents of 22.1% and 20.5%, respectively and will be suitable time for outplanting.