The Research On Second Generation Growth And Characteristics Of Forest Plantation Of Fir In Hilly Of Central Hunan

In subtropical China,fir(Cunninghamialanceolata)is one of the fast-growing timber species,fir forest area accounts for about 24%of the total plantation area in China,that occupies an important position in the Southern forestry production.In order to understand the growth conditions,Soil characteristics,plant diversity and biomass of the second-generation Chinese fir plantations in the middle hilly region of Hunan province.This paper research experimental forest in "Zhushi Cunninghamia lanceolata Matrix" in Hunan.Exploring the technology of fast-growing fertility and growth potential of Cunninghamia lanceolata from the way of soil preparation and measure of fertilization.At the same time,investigating the Chinese fir plantations land soil characteristics,including soil nutrients,soil microbial and soil enzymes;preliminary study of plant diversity,biomass and carbon density.In soil fertility(fertilization)experiment,This paper using uni-factor and orthogonal design.It through setting temporary sample plot(Respectively is 12a,14a,16 a,18a of Chinese Fir Clone forest and21 a,22 a of Chinese Fir Seedling Stand).Then survey each timber,and select the standard wood for stem analysis,drawing the growth curve of each factor,compared the growth curves of 12a,14a,16a,18a Chinese Fir Clone stands with 22a Chinese Fir Seedling Stand.In order to research the relationship between trees growth and soil fertility,soil microbial or soil enzymes in the hilly area,In this paper,we do the experiment analysis the total number of microbes and the quantity of bacteria,fungi,actinomycetes and invertase,urease,catalase and soil nutrient of the surface soil in the different plantation age and needle mixed forest;and study the effect on forest biological diversity and fir biomass in various organs and carbon density.The results showed that:1.Different slope positions have a significant effect on the fir plantations DBH,while the effect on tree height and volume is not significant.Different land preparation methods have a significant effect on the fir plantations tree height,DBH and per unit area of the volume.The differences of tree height,DBH and per unit area of the volume are not significant with Slope position and site preparation interaction.Different slope positions and different land preparation methods have an impact on volume.Tease trench site preparation in lower slope position(11)have a maximum individual volume,soil preparation in small hole in upper slope position(33)have a minimum individual volume.land preparation methods 1(tease trench site preparation)have a maximum contribution to the volume,then the land preparation methods 2(soil preparation in large hole),minimum the land preparation methods 3(soil preparation in small hole).Interplanting also have a significant differences on the growth of DBH,The maximum DHB appears in(111)interplanting l,base fertilizer 1,top dressing 1.The minimum DHB appears in(222)interplanting 2,base fertilizer 2,top dressing2;the interplanting have a great effect on tree height and volume;the single factor of base fertilizer and top dressing have no obviously differences to the result of research;interplanting*base fertilizer*top dressing influence a lot on the growth of DHB,and also have a great impaction on tree height and volume.2.Clones fir,tree height is higher than fir seedlings,and peeling diameter at breast height,peeling volume of wood are significantly larger than fir seedlings;the annual mean increment of tree height is slightly larger than fir seedlings,the annual mean increment of diameter at breast height and individual volume are significantly larger than fir seedlings.To the clones fir,it's annual mean increment and annual mean increment of diameter at breast height are descending with age increasing,the annual mean increment of individual volume is increasing firstly and then descending with age increasing.maximum annual mean increment appears between16-18a.In four different varieties of clones firs,Cedar fir apart from tree height,it's diameter at breast height,crown width,volume are significantly higher than.Gold Cup fir grow not as good as other three kinds of clones fir in tree height,diameter at breast height,crown width and volume.The best principal felling age of Chinese fir clones was 18a,and the seedling is 21a.Clones of the best felling age than seedling 3a ahead of schedule.Using excellent clones for afforestation is feasible in production.Because it can not only shortens the best final felling age,but also improve the per unit area of a material amount and increase income.3.Chinese fir plantation soil nutrient distribution in 0-20cm higher,20-40cm followed by 40-60cm lower,Soil nutrient content descending with age increasing,Especially the macro element in the soil such as nitrogen,phosphorus,potassium and medium elements calcium,magnesium,but trace elements such as copper,iron,zinc,manganese changes a little.For the 16a seedling and clones Chinese fir,the macro element in the soil of clones descending faster than seedling,this result show that clones consumes more macro element,sexual consumes more medium elements and trace elements;From the the trend of N,P,K can be seen that the entire cycle of growth in theChinese fir,N,Pand K content were significantly lower,recommended for production increasing N,P,K fertilizer,to ensure normal growth of Chinese fir and increase production.According to relevant information,fir young forest have a higher soil fertility,from young forest to the middle-aged forest and from middle-aged forest to nearly mature forest,the soil nutrient content have a total downward trend,therefore,required to replenish the nutrients.4.12a hilly region of Chinese fir plantation was the largest number of microbes in the soil;16a Chinese fir plantation of soil microorganism quantity at least.Along with the increase of plantation age,the soil enzyme activity increase,but to a certain stage(18a),The soil enzyme activity with the plantation age and decreases.On the whole,Needle mixed forest of rich soil microorganism quantity greater than Chinese fir plantation;Needle mixed forest soils widening of the activity of an enzyme is greater than the Chinese fir plantation.5.Age of Fir plantation have a great impaction on the community biodiversity,21a 22a fir plantations have abundant plant species,but fewer plant species in 12a fir plantations,Seedling species also have influence on the community biodiversity,species diversity index of wood layer that belong to clones is high,shrub layer have high species diversity index and high species richness,herb layer belong to seedlings have a high diversity index.For the species richness,clones is higher than sexual.therefore,the development of fir plantation should according to the different age rationally adjust the population structure,and create good conditions for forest growth is conducive to the conservation of species diversity and restoration.6.The fir plantation biomass of each organ the size of the order of stem>root>leaf>branch>fruit,the total biomass of plant organs increases with stand density showed an declining trend.And,to a certain density range,as the density increases,the fir plantation biomass increased significantly.Carbon density in different organs fir varies between the 2.7569t/hm2-159.0984 t/hm2,according to the order of the level of carbon,sulfur intensity:trunk>root>branch>leaf>cone,arranged in the level of percentage content of carbon order:fruit>leaf>branch>stem>root,The following order of sulfur content i:trunk>branch>leaf>root>fruit;different age fir forest carbon density,indicating the storage of carbon has a certain periodicity,The order of the carbon density were nearly mature forest,mature forest,overmature forest,middle-aged forest,young forest;canopy density and aspect have a great effect on carbon density and slope position there was no significant impact.