Dynamics For Different Planting Densities Of Hybrid Larch Plantation

This research is part of the "Study on the improved variety and directed breeding technology of the high quality wood construction material forest" of the significant research project of Heilongjiang Province science and technology (GA09B202-02).Hybrid larch is a new species for forestry research institute of Heilongjiang province to study after30years, whose growth rate, disease and pest resistance ability and hardiness were more excellent than Larix Olgensis. A corresponding, more perfect cultivation pattern will be established for Hybrid Larch was extended in Heilongjiang province large area at present, and the important part of the pattern is the study on the planting density. The experimental field was established in the biggest area of Hybrid Larch in our country, which is14years old and the area is20hm3.48fixed standards were observed continuously that were setted in four afforestation densities(2500N/hm2,3300N/hm2,4400N/hm2,6600N/hm2) in2004.The first-hand material of the study on afforestation density were accumulated from the data of the biomass, litterfall, litter decomposition and soil conditions of Hybrid Larch in different afforestation density were investigated, so the results has strong persuasion and can provide very good supplement for Larch hybrids cultivation pattern.The growth law, biomass and carbon storage, litter and its decomposition, soil physical and chemical properties and microorganisms were studied with variance analysis, multiple comparison, mathematical models and other methods, the main result are:The effect of afforestation density on plant growth index of Hybrid Larch were remarkable. The afforestation density bigger, the diameter, singleplant volumn and crown width of Hybrid Larch smaller.3300N/hm2is the best afforestation density for the better growth, stem form relatively full, large yield.The effect of afforestation density on the singleplant biomass and stand biomass of Hybrid Larch were significant. The singleplant biomass in3300N/hm2was biggest (23.65kg) and the proportion of branch and leaves were larger(35.43%). The singleplant biomass in4400N/hm2was lowest(21.78kg) and the proportion of trunk and bark were larger(69.28%). The fitting precision of individual biomass regression model in different density which can provide more accurate scientific basis for biomass and carbon storage of Hybrid Larch were higher.The decomposition rate of Hybrid Larch litter was effected by afforestation density, the density bigger, the decomposition cycle longer, the longest time was more than17years(2500N/hm2) and the shortest was only a little more than13years (6600N/hm2). The decomposition cycle was only less than4years in2500N/hm2after the microhabitat altered. The content of nutrient elements of litter in3300N/hm2and4400N/hm2decreased faster and it showed that the nutrient elements in these two afforestation densities returned faster.3300N/hm2and4400N/hm2were the more suitable afforestation density for better soil structure, nutrient adequacy and microbe propagate according by the effect of the content of hydrolyzable nitrogen, available phosphorus, available potassium, total nitrogen, total phosp N horus, total potassium, calcium, magnesium and the quantity of soil microbes3300N/hm2and4400N/hm2were the the better afforestation density for Hybrid Larch on growth, stem form and nutrient cycle from the analysis and evaluation of the above research. Thinning was not needed to cultivate middle diameter timber and small diameter timber in the stand the afforestation density was3300N/hm2, and1or2times thinning in the stand the afforestation density was4400N/hm2to cultivate middle diameter timber and large diameter timber.This research was an important supplement for the optimization management of Hybrid Larch, and it can provide scientific guidance and basis for Hybrid Larch to extension in Heilongjiang Province.