| This thesis adopted the "time specific" and "fixed position" method to investigate synthetically the Eucalyptus urophylla plantation during 0.6～3.6 years old on the growth and development characteristics, the stand biomass and productivity, the nutrient accumulations and distribution, the structure and diversity of underground vegetation, the soil physical and nutrient properties as well as the soil microorganism. The research results showed: l)The mean height, DBH , the individual volume and the growing stock increased distinctly with the increasing of stand ages .The E. urophylla wood manifested the strong-growing characteristics of early stage .The total growth of the height, DBH and the growing stock of E. urophylla didn t descend with planting generation increasing. But the growth characteristics of E. urophylla plantation were affected by continuous-plating rotation, and the current increments had displayed the declining-trend. 2) The biomass of individual tree and stands exhibited the patterns of Wthe third generation (37.38kg/average tree ; 61.91t/hm2)>Wthe first generation (28.37kg/average tree ;48.38t^im2)>Wthe ^d generation) (24.51kg/average tree ;43.80t/hm2),and yet didnt change regularly with plantation generation increasing. The biomass distribution of tissues of E. urophylla in the different plantation generation was in the sequence of stem(It was ranged from 62.03% to 63.74%)>bark(from 8.92% to 9.30%)>stump (from 8.83% to 9.23%)>stout root(from 4.26% to 6.86%)>branch(from 4.22% to 5.17%)>leaf(from 2.74% to 3.49%)>dead branch(from 2.72% to 2.84%)> twig(from 1.93% to 2.22%)>absorptive root(from 1.16% to 1.26%)>fme root(from 0.88% to 0.90%).The proportions of above and undergroundbiomass were ranged from 84.48% to 84.75% and from 15.25% to 15.52%; The biomass distribution of tissues in different generation plantation exhibited identically the same law, but the structure of the crown and the ratio of branch and leaf were influenced by continuous-planting rotation so that the growth of E. urophytta stands distinctly showed the difference. 3) The productivity of the tree layer of different generation in Dongmen was in the order of the third generation (17.77t/hm2.a)> the first generation (13.82t/hm2.a) > the second generation (12.45t/hm2.a), and yet the productivity of E. urophytta stands didnt change regularly with plantation generation increasing. 4) The accumulation of underground vegetation and litter layer decreased with the plantation generation increasing. Compared with the first generation plantation, the biomass of underground vegetation of the second generation and the third generation decreased by 131.65% and 195.16% respectively, and the third generation decreased by 21.52% than the second generation; The biomass of litter layer of the second generation and the third generation which were compared with the first generation decreased by 12.89% and 95.95% respectively, and the third generation decreased by 75.48% than the second generation. The result indicated that the biomass accumulations of the underground vegetation and litter layer were negative correlative with the plantation generation increasing. 5) The average nutrient concentration of E. urophytta in different issues was in the sequence of N>K>Ca>P>Mg> Mn>Fe>Zn>Cu. The nutrient accumulations of nine elements of the tree layer was between 215.95 and 279.35kg/hm2, and showed the patterns of the third generation (279.35kg/hm2)> the first generation (231.77kg/hm2)> the second generation (215.95 kg/hm2). The nutrient utilization efficiency of E. urophylla was relatively high, and the nine nutrient necessary for dry matter production of the first ,second and third generation was 4.788kg/t, 4.927kg/t and 4.51kg/t respectively. 6) The total nutrient accumulations of the bio-system among the different planting generations exhibited: the first generation"") O(416.76kg/hm ) >the third generation (338.73 kg/hm ) >the second generation (321.04kg/hm2...
|
PDF Full Text Request