The Study On Growth Rule And Productivity Of Eucalyptus Castanopsis Hystrix And Castanopsis Fissa Mixed Forest

With the development of society,people's demand for forest products resources has been increasing.Eucalyptus as the main species of fast-growing and High-yielding timber forests has been vigorously developed in southern China.The rapid development in Guangxi has played a positive role in promoting the local economic development.Therefore,the study on the growth and productivity of pure and mixed eucalyptus forests will provide an important theoretical basis for the afforestation model of southern eucalyptus.In this paper,16-year-old pure Eucalyptus forest,mixed Eucalyptus and Castanopsis fissa forests,mixed Eucalyptus and Castanopsis hystrix forests were taken as research objects.The main contents of the study include the growth rhythm of single tree's diameter at breast height,tree height and volume,biomass and productivity of pure eucalyptus forest and its mixed forest.The main conclusions are as follows:(1)The total increments of diameter at breast height,tree height and volume of standard trees in 16-year-old pure eucalyptus forests were 19.9cm,28.2m and 0.347m3,respectively.The total increments of diameter at breast height,height and volume of standard trees in 16-year-old mixed Eucalyptus and Castanopsis fissa mixed forests were 20.9 cm,28.8 m and 0.3616m3 respectively.The total growth of standard tree's diameter at breast height,tree height and volume of 16-year-old Eucalyptus and Castanopsis hystrix mixed forest reached 23.1 cm,29.9 m and 0.375111m3,respectively.The total increment of diameter at breast height,tree height and volume of Eucalyptus increased with the increase of forest age.The diameter at breast height,tree height and total volume in Eucalyptus and Castanopsis hystrix mixed forests were the largest,which was 1.16 times,1.06 times,1.08 times of that of Eucalyptus pure forest.(2)The biomass of standard trees of 16-year-old eucalyptus pure forests was 224.09 kg.The order of biomass allocation proportion of each organ was as follows:runk>branches>skin>leaf,root shoot>taproot>middle root>fibrous root.The biomass of standard trees of 16-year-old Eucalyptus and Castanopsis fissa mixed forests was 237.23kg.The order of biomass allocation proportion of each organ was as follows:trunk>skin>branch>leaf,root shoot>taproot>middle root>fibrous root.The biomass of standard trees of 16-year-old Eucalyptus and Castanopsis hystrix mixed forests was 252.3 3kg.The order of biomass allocation proportion of each organ was as follows:trunk>skin>branch>leaf,root shoot>taproot>middle root>fibrous root.The biomass of Eucalyptus and Castanopsis hystrix mixed forests was significantly higher than that in pure forests.(3)The plantation biomass of 16-year-old pure forests was 250.77 t-hm'2,of which the total biomass of arbor layer reached 248.74 t-hm-2 accounting for 99.2%of total plantation biomass.The plantation biomass of 16-year-old Eucalyptus and Castanopsis fissa mixed forests was 298.46 t-hm-2,of which the total biomass of arbor layer reached 293.61 t hm-2 accounting for 98.37%of total plantation biomass.The plantation biomass of 16-year-old Eucalyptus and Castanopsis hystrix mixed forests was 296.39 t hm-2,of which the total biomass of arbor layer reached 290.47 t·hm-2 accounting for 97.71%of total plantation biomass.The biomass of Eucalyptus-Castanopsis fissa mixed forests was 0.7%and 19.02%higher than that of Eucalyptus-Castanopsis hystrix mixed forests and pure Eucalyptus forest,respectively.(4)The productivity of different forest types is different.The productivity of 16-year-old eucalyptus pure forests were 15.56 t·hm-2·a-l,and the productivity of eucalyptus and Castanopsis fissa mixed forests were 18.36t hm-2·a-1.The productivity of eucalyptus and Castanopsis hystrix mixed forests were 18.18 t hm-2·a-1.(5)The soil bulk density of eucalyptus pure forest,eucalyptus and Castanopsis fissa mixed forests,eucalyptus and Castanopsis hystrix mixed forest showed the following rules:with the deepening of soil depth,the bulk density of Eucalyptus pure forest was larger than that of the two mixed forests.The maximum water holding capacity,capillary porosity,non-capillary porosity and total porosity of two kinds of mixed forests were higher than that of pure forests.Soil organic matter content,such as total nitrogen content,total phosphorus,total potassium and available phosphorus content decreased with the deepening of soil depth.The contents of soil organic matter in mixed forests were higher than those in pure forests.