| Global industrialization and the improvement of people's living result in the rapid growth of timber demand, but global forest resources decrease sharply. Therefore, Countries in the world vigorously develop industrial plantations to alleviate the contradiction between supply and demand for timber and forest products. For China's forest resources shortage and contradiction between supply and demand for timber and wooden materials, industrial plantations development is one of key measurements to solve those problems. Eucalyptus is popularly planted all over the world because of rapid growth, high yield, good quality. Eucalyptus, as well as Populusspp and Pinusspp, are regarded as world three rapid and high-yield forests. It is one of successful introduction species, and even preferred species in the rapid and high-yield forest bases of the southern region. In the present, Eucalyptus plantation in China has reached 1.7 million hm~2 and the rapid and high-yield forest bases in Guangxi have reached 533,600 hm~2 which ranks the first in the rapid and high-yield forest bases of china's Eucalyptus. In this background, it is an urgent problem about how to scientifically and reasonably manage Eucalyptus industrial plantation.In this study, by long-term positional observation, the theory and method of integrated system science such as combinations of qualitative judgment and quantification, modeling, micro-analysis and macro-synthesis, holism and reductionism, field surveys and scientific reasoning were used to study the growth and structure law, stand density effect law, soil effect, biomass, productivity and plant diversity of Eucalyptus industrial plantation. Based on the above researches, objectives, theory model and the management level model of Eucalyptus industrial plantation management were proposed, and index system of Eucalyptus industrial plantation sustainable management is constructed, which afford the theoretical basis and technological support for Eucalyptus industrial plantation sustainable management. The main results were as followed:1 , Growth law, diameter structure law, dynamic changes of soil physical and chemical properties, biomass, productivity distribution patterns and plant diversity about different continuous-planting rotations of E. urophylla × E. grandis were researched by long-term positional observation for the first time, which provide E. urophylla x E. grandis industrial plantation management for a theoretical basis.(1) For different continuous-planting rotations of E. urophylla × E. grandis industrial plantation from the first to third generation, their differences in DBH, height and volume growth were not significant and growth processes were similar. For different continuous-planting rotations of E. urophylla × E. grandis, their DBH growth reached the growth peaks in the 2nd year and the 5th year, but the latter was significantly lower than the former; All continuous-planting rotations of E. urophylla × E. grandis kept higher height growth so that the average increment of 7 years-old height was beyond 2.5m, and the height annual increment decreased obviously after growth peak at the 2nd year; the average increment stock of volume per unit area of stand in different continuous-planting rotations of E. urophylla × E. grandis reached the maximum in the 5th year, namely quantitative mature age(QMA) of E. urophylla × E. grandis industrial plantation is 5a.(2) The growing process about rotation stands of E. urophylla × E. grandis were divided into three stages by cluster analysis. In the fast growing phase from 1a to 2a, DBH and height grew quickly; In the common growing phase from 3a to 5a, DBH and height relatively grew stably and annual volume growth arrived at the maximum; In the slow growing phase from 6a to 7a, DBH and height decreased obviously and the average volume growth became slow.(3) Stand diameter distribution disciplines of E. urophylla × E. grandis and Eucalyptus urophylla were described well by β distribution function and the plot acceptance rate were 85.19% and 93.33% respectively. With the age increasing, the variant coefficient of stand diameter distribution disciplines of the two stands increased, namely differentiated level of stand diameter increased and diameter distribution range became wide; stand diameter distribution curve inclined to the right in the peak, namely large diameter timber held the majority in stand diameter distribution of E. urophylla × E. grandis and Eucalyptus urophylla.(4) Continuous planting renovation occurred negative effects of on soil physical and chemical properties of Eucalyptus industrial plantation , namely soil bulk density, soil porosity, aerating degree, the maximum water holding capacity, pH, soil organic matter, total N, total P, total K and hydrolysable nitrogen decreased with the increase of continuous planting rotations. Continuous planting rotations obviously affected soil fertility decreasing trend.(5) The continuous copping had obvious effects on reducing the diversity index, evenness index, richness index in continuous-planting rotations of E. urophylla x E. grandis industrial plantation, namely the plant diversity under forest decreased with the increase of continuous planting rotations, but ecological dominance increased.(6) The biomass and productivity of stand and community were alike in continuous planting rotations of regeneration E. urophylla × E. grandis from the 1st generation to 3rd generation, but understory vegetation and litter biomass in E. urophylla × E. grandis decreased with the increase of continuous planting rotations. Stand organs biomass distributions were not obvious in different rotations, the sequences were as follows: stock > root>bark>branch>leaf.2, Differences in stand growth, biomass, productivity, soil physical and chemical properties and plant diversity were revealed about E. urophylla × E. grandis in planting regeneration and in sprout regeneration of different densities. In addition, the regeneration and management patterns were put forward to benefit effectively plant diversity, vegetation biomass, productivity and soil nutrients.(1) In the same density, BHD, height and volume of E. urophylla × E. grandis in planting regeneration were better than those of E. urophylla × E. grandis in sprout regeneration. In the sprout regeneration stand, the BHD decreased with the increase of reserved density, but differences in stand height were not obvious; volume per unit was raised effectively in stand reserved density of 2100 per hm~2.(2) In sprout regeneration stand, soil bulk density, soil porosity, aerating degree, the maximum water holding capacity increased with the increase of reserved density, which appeared positive effects. At the same density, soil bulk density, soil porosity, aerating degree, the maximum water holding capacity in planting regeneration stand were more than those in sprout regeneration stand. With the reserved density increasing in sprout regeneration stand, soil organic matter, total N, total P, total K increased, which appeared positive effects; while soil available nutrients, exchangeable Ca and Mg decreased, which appeared negative effects.(3) Diversity index, evenness index and richness index of E. urophylla × E. grandis stand in planting regeneration with full reclamation were lower than those in sprout regeneration. In sprout regeneration, diversity index, evenness index and richness index of E. urophylla × E. grandis stand increased with the increase of reserved density.(4) Biomass and productivity of E. urophylla × E. grandis industrial plantation in planting regeneration were higher than those in sprout regeneration. And stand biomass, community biomass and productivity of E. urophylla × E. grandis industrial plantation in sprout regeneration increased with the increase of reserved density, and productivity per unit was raised in reserved density of 2100 per hm~23 , Differences in stand growth, biomass, productivity, soil physical and chemical properties and plant diversity were revealed about the pure forests of Eucalyptus urophylla and the mixed forests of Eucalyptus urophylla and Acacia mangium in different ratios. It showed that reasonable mixed forest of Eucalyptus urophylla and Acacia mangium can effectively improve soil physical and chemical properties, soil nutrients and plant diversity.(1) In the same density, for he pure forests of Eucalyptus urophylla and mixed forests of Eucalyptus urophylla and Acacia mangium, the latter's DBH, height, volume were better the former's; For the above indexes and diameter-height ratio, the significant differences lied in different treatments in mixed forests. In this study, the mixed ratio 1:1.6 of Eucalyptus urophylla and Acacia mangium showed the best mixed model when 676 plnats/hm~2 in Eucalyptus urophylla and 1051 plnats/hm~2 in Acacia mangium.(2) Soil bulk density in the mixed forests of Eucalyptus urophylla and Acacia mangium was lower than that of Eucalyptus urophylla, but aerating degree, capillary porosity, non-capillary porosity and the maximum water holding capacity of mixed forests was higher in the mixed forest than those of Eucalyptus urophylla; soil organic matter, total N, total P, total K, exchangeable Ca and Mg of mixed forests were higher than those of Eucalyptus urophylla, which proved the mixed forests can effectively raise soil nutrients(3) For Eucalyptus urophylla and mixed forests of Eucalyptus urophylla and Acacia mangium in the mixed ratio of 2:1, the latter's diversity index, evenness index and richness index were higher than the former's. However, when the ratio of Eucalyptus urophylla: Acacia mangium was 1:1.6, the mixed forest's diversity index, evenness index and richness index were higher than the pure forest's. Not all mixed forests in different mixed ratios can effectively improve plant diversity. To form suitable illumination factors for promoting plant growth and development under forests, suitable mixed ratio was the key to maintain normal plant growth and plant diversity.(4) In the same density, stand biomass of Eucalyptus urophylla was lower than that of mixed forests of Eucalyptus urophylla and Acacia mangium. It showed that the mixed forests with niche difference can fully utilize forest land and improve productivity.4, The relationships plant diversity of Eucalyptus industrial plantation between soil physical and chemical properties, as well as biomass, were revealed by grey incidence analysis and trend surface analysis for the first time.(1) By grey incidence analysis, diversity index, evenness index, richness index of Eucalyptus industrial plantation in different regenerations had the same relativity to soil physical properties, namely the most relationship lay in between diversity index or richness index and aerating degree, and the least relationship lay in between those and soil bulk density, but the most relationship lay in between those and evenness index. The most relationship lay in between richness index, Shannon-wiener index, evenness index and soil trace elements, followed by soil available nutrients, organic matter and pH, but the least relationship lay in between richness index, shannon-wiener index, evenness index and exchangeable Ca and Mg.(2) The results of trend-surface analysis showed that improvement of plant diversity in different continuous planting rotations of E. urophylla × E. grandis was improved had significant effects on root system biomass in forest land and vegetation biomass under forests, but insignificant effects on stand biomass, stock biomass, bark biomass, branch biomass and leaf biomass.5, Density effect law of Eucalyptus urophylla industrial plantation was revealed and that model was proposed. Suitable planting densities in different site index were proposed by productive elasticity analysis and marginal analysis.(1) In the same density, short-rotation E. urophylla × E. grandis industrial plantations, the different row spacing had no significant effects on DBH, height, individual volume and volume per unit. In different densities, the stand average DBH increased with the decreasing density, which appeared negative effects. Within certain density ranges, volume per hectare increased with the increasing density, which appeared positive effects. As the density increased to a certain degree, the density had negative effects on volume per hectare.(2) The average DBH of large-diameter E. urophylla × E. grandis decreased with the increasing stand density, which appeared negative effects, but density had no similar effects on height, height-diameter ratio and individual volume.(3) The parabola improved model of the density effect of short-rotation E. urophylla × E. grandis industrial plantations was raised. By productive elasticity analysis, the density effect of E. urophylla × E. grandis was in negative stage. When the density decreased by 1%, the average individual volume increased by 0.4520%; When the other conditions are the same, by marginal analysis, one tree per hectare increased and the average individual volume decreased by 0.000032m~3; when dominant trees height increased by 1.0m, the average individual volume increased by 0.001 m~3; when stand age amounted to the baseline age(6a)calculated by site index, optimum densities per hectare of E. urophylla × E. grandis industrial plantations in 15-20 site index was 1237, 1492, 1779, 2100, 2458 and 2853 respectively.6, By analysis of limitations of mature types of traditional forest, volume largest harvest period, technology best harvest period and economic benefits as new concepts were proposed for Eucalyptus industrial plantation management time decision. Three kinds of harvest periods were used as a whole to be proposed for the concept of comprehensive harvesting period, which afforded traditional forest mature to a new meaning, enriched and developed the relative concepts and basic theories of forest management time decision.7, It was the first time for sustainable management evaluation index system of E. urophylla ×E. grandis industrial plantations at stand level to be raised to constructed the theory, practice, guidance ideology and principles of sustainable management evaluation index system. A set of sustainable management evaluation index system at stand level, including five layers and 23 indexes, such as resources, economy, ecology, productivity and comprehensive growth potential, was constructed in order to provide theory and method references for future researches.8, Two classes management aim system including economic and ecology were raised about E. urophylla × E. grandis industrial plantations at stand level for the first time. The industrialized forest management theory included management conditions and rules, adjustment theories, evaluation theories and so on. The above achievements enriched and developed the basic theories on forest management.9, The forest management models and technology in E. urophylla × E. grandis industrial plantations at stand level were raised for the first time, including continuous cropping model, sprouting refreshment model, mixing model and big-diameter timber cultivating model.
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