【作者】 温远光；

【导师】 陈放；

【作者基本信息】 四川大学 ， 植物学， 2006， 博士

【摘要】 桉树是桃金娘科(Myrtaceae)桉属(Eucalyptus)树种总称，有795种(其中变种和亚种114种)，它具有种类多、干形好、生长快、产量高、耐瘠薄、抗性强、适应性广、用途多、经济价值高等优良特性，至今有96个国家引种桉树，桉树人工林面积已突破2000万hm~2，成为热带亚热带地区极为重要的速生造林树种。中国引种桉树有110多年的历史，全国种植桉树的省(区)有17个，涉及600多个县，成为我国南方最重要的速生造林树种之一。全国桉树人工林面积在200万hm~2以上，在华南地区，有60-70％的桉树人工林属于短周期人工林，其中50-60％的林地采取连栽方式。随着桉树人工林的大发展和连栽制度的全面推行，桉树人工林的生态脆弱性进一步凸现，“桉树争论”愈演愈烈，桉树发展已成为社会广泛关注的焦点。要做到人工林既有高生产力，又维持生物多样性，是当代生态学所要解决的迫切任务，也是一个重大的科学难题。生物多样性与生态系统功能是国际生态学界关注的重大科学问题，也是桉树人工林发展过程中出现的突出问题中的核心和关键，至关桉树人工林的可持续经营和生态环境的可持续发展。国际国内林学和生态学界对此开展了大量的研究，然而，对于桉树人工林生态系统中生物多样性与生态系统功能关系尚缺乏长期实验研究。本项目从1998年开始立项研究，旨在通过对尾巨桉不同连栽代数的林地上开展生物多样性与生态系统功能的长期实验研究，揭示桉树人工林植物物种多样性与生态系统中林木生长、生产力、养分循环、养分利用效率、地力保持、群落稳定性和可持续性之间的关系，为解决桉树人工林高生产力与高多样性维持之间的矛盾提供科学理论依据，为桉树人工林持续经营提供指导。毫无疑问，本项目的开展对推动我国生物多样性与生态系统功能关系研究的发展以及桉树人工林基地的生产经营从理论和生产实践上均有重要的指导作用；对生态环境建设和区域经济发展亦有重要的意义。在1998至2005的长期实验研究的基础上，本研究的主要结果和结论如下：采用长期定位研究方法，对不同连栽代数尾巨桉人工林的生长发育规律和结构特点进行了8年的研究，结果表明：在一个经营周期内(1-7年)，尾巨桉林木胸径生长和材积生长具有两次生长高峰，第1次高峰出现在第2年，第2次高峰出现在第5年，胸径生长以第1峰为主，而材积却以第2峰为主，胸径生长和材积生长存在明显的“峰一峪”变化；树高生长仅表现出一次生长高峰(在第2年)；材积的平均生长量与连年生长量曲线相交于第5年。提出了将尾巨桉人工林分为幼树阶段、幼龄林阶段、中龄林阶段和成熟林阶段共四个发育阶段的理论和标准。尾巨桉人工林的直径和树高结构随年龄的变化遵循人工纯林的一般规律，但其幼龄林的直径和树高分布曲线的偏度存在明显的右偏，表明尾巨桉具有显著的早期速生特性；尾巨桉人工林冠层结构单一，叶面积指数低，1代林低于2代林。经对实验结果的差异显著性分析，得出1代林和2代林的直径生长、树高生长和材积生长均无显著差异而树冠结构存在显著差异的结论。连栽对尾巨桉2代林生长无显著影响。长期定位实验研究表明，尾巨桉成熟林分(7.3年)的蓄积生产力水平为20-21m~3/hm~2·a，生物生产力水平约为19t/hm~2·a。对1代林和2代林的生物量和生产力进行差异显著性检验表明，连栽对2代林的生物量和生产力没有显著影响。树干、树皮、树枝和根系的生物量和生产力均随着林分年龄的增长而增加，只有树叶的生物量和生产力表现为先增加后减少的规律。林分生长后期，根系和树叶生物量增长缓慢甚至出现负增长影响了林分后期生产力的持续性。连栽具有增加树皮、树枝和树叶生物量比例的趋势。连栽导致林下植被生物量和生产力的显著下降，2代成熟林下植被生物量和生产力比1代林下降70％；从幼龄林(2-3年)到成熟林(6-7年)，1代林下植被的生物量和生产力表现为缓慢的持续增长趋势，而2代林却表现为逐渐递减趋势。采用长期定位实验研究方法，对不同连栽代数桉树人工林的物种多样性、土壤种子库及物种多样性维持机制进行了研究。结果表明，桉树连栽导致人工林植物多样性减少，2代林的物种丰富度和Shannon-Wiener指数分别比1代林减少39.39％和17.76％。群落的β多样性中，1代林的Jaccard系数和Cody指数均显著高于2代林；代内群落的相似性系数高，为60％左右，而代间群落的相似性系数低，为30％左右，表明连栽引起大量物种丢失。桉树人工林连栽不仅导致群落物种多样性降低，而且改变了群落的物种组成及特征。对成熟林比较，不同连栽代数群落的生活型谱存在明显差异，第1代林以藤本高位芽和矮高位芽植物为主，2代林则以地上芽植物和矮高位芽植物为多；1代林的k-对策种和r-对策种分别为64.79％和35.21％，2代林则分别是51.02％和49.98％，连栽使草本植物、地上芽植物和r-对策种的数量增加，木本植物和k-对策种的数量减少。对土壤种子库的研究表明，不同连栽代数土壤种子库储量及多样性变化与地上植物多样性的变化规律基本一致。土壤中种子库和营养体对物种多样性维持有重要作用，提出了桉树人工林群落物种多样性维持机制的初始植物繁殖体组成假说。在一个经营周期内(6-7年)，桉树人工林维持的植物多样性的高低取决于初始植物繁殖体组成的丰富程度，高强度干扰(如炼山和机耕全垦整地)的连栽制度使某些高竞争力的物种或仅以种子(果实)传播的物种丧失，造成下一代林地初始植物繁殖体组成多样性的降低，从而使连栽林地的物种多样性逐代减少。土壤种子库的研究结果支持了这一假说：采用长期实验和常规养分分析相结合的研究方法，对不同连栽代数尾巨桉人工林的植物养分元素含量、积累、分配、养分循环及地力效应进行了研究。结果表明，尾巨桉属于Ca>N>K>Mg>P型树种，有强烈的聚集Ca的作用。尾巨桉林分具有养分累积快速、养分循环存留率高(约占94％)、归还率低(约占6％)的特点，5种营养元素(N、P、K、Ca、Mg)的总循环率为40.40-41.81％；在元素的生物循环中，以N和P的生物循环率最高，其次是K和Mg，Ca的生物循环率最低。尾巨桉具有极低的养分消耗率，平均每生产1t干物质所需5种养分的数量为5kg左右，生产1t干材只需要2kg养分，可是，由于它的高产性使得它对林地土壤养分的利用和消耗又是巨大的。连栽对2代林乔木层养分的吸收和积累没有构成明显影响。但是，连栽对林下植物的养分积累构成显著影响，使2代林下灌木层和草本层植物的养分积累量减少115％和85％，造成乔木层与林下植物的养分积累比例严重失衡。连栽具有降低土壤容重，提高土壤孔隙度和通气度，增强土壤持水能力的作用，但这种作用并不能持续，一般只能维持3-4年；连栽对土壤养分存在着正效应和负效应，以负效应为主；连栽导致0-20cm土层的土壤养分全面下降，其中Ca和Mg的下降最为明显；连栽还使土壤的pH值减少，导致土壤酸化。在对36块100m~2实验样地中植物组成、生物量、养分等进行全面调查研究的基础上，采用3种多样性指标和4种生态系统功能指标，对植物多样性与生态系统功能关系进行了研究。结果表明，物种多样性与林木器官生物量关系较弱，只有吸收根特别例外，它与3种多样性指标均存在显著或极显著的负相关，表明随着林下植物多样性的增加林木吸收根生物量显著降低。和乔木层不同，植物多样性有利于增加林下植物的生物量和生产力。植物多样性对乔木层、灌木层和草本层植物的5种养分元素(N、P、K、Ca和Mg)的利用效率具有显著作用，3种多样性指数与乔木层N、P、K和Ca的养分利用效率呈紧密或极紧密的正相关，而与Mg元素为显著的负相关；多样性有利于提高乔木层N、P、K和Ca的养分利用效率，而降低Mg的利用效率。物种丰富度与灌木层植物的养分利用效率存在极显著的正相关，但在草本层只与K元素的养分利用效率相关紧密，与其它元素相关不紧密。物种丰富度增加养分利用效率。物种多样性高的群落，林下物种恢复力、植被盖度恢复力、植被生物量恢复力和土壤养分恢复力均较高，物种多样性有利于提高群落的抵抗力和恢复力，增强稳定性。由于连栽制度采取的强度干扰方式对群落的稳定性构成显著影响，直接威胁桉树人工林生态系统的物种多样性和土壤肥力的可持续性。在全面分析物种多样性与生态系统功能关系的基础上，提出了短周期工业人工林培育的一种新理论——资源空间分类经营理论，这将在理论上有效地解决人工林高生产力与高多样性的矛盾，实现人工林高生产力与高多样性的统一。更多还原

【Abstract】 Eucalypts belongs to the Myrtaceae family, Eucalyptus genus, with 795 species (including 114 subspecies and varieties). Eucalyptus is the genus of trees is most planted around the world because of its large number of species, fast-growing, high-yield, the ability to adapt to many different sites, and the possibilities of producing wood for many different uses. Up to now, there are 96 countries planted eucalypt, and there are at least 20 million ha of areas of planted eucalypt. Remarkably, eucalypts have become the most widely planted hardwood species in the world.Eucalypts were introduced into China in 1890. Up to now, more than 300 species have been introduced in more than 600 counties of 17 provinces, among the species introduced, 200 species have been tried in afforestation, but only about 10 species were widely planted. Over 2 million of Eucalypts plantations have been established in China. Eucalypts plantation of 60-70% in Southern China belonged to short-rotation forest plantation, in which 50-60% of stand sites had been carried out continuous planting system. With the increasing areas of Eucalypts plantations established and carrying out on continuous planting throughout the country, the environmental problems of eucalypt plantations (include impacts on soil water, soil nutrients, soil erosion and biodiversity) are more and more serious, the "Eucalyptus controversy" has become an important issue in the tropics and subtropics. The developing eucalypt plantation has been a focus of the society’s attention. To make high-yield and high-diversity of eucalypt plantations, it is an important task of ecology and a major scientific issue too.The relationship between biodiversity and ecosystem functioning has emerged as a major scientific issue today, a key problem for the sustainable management of eucalypt plantation and sustainable development of the ecological environment. Although the relationship between biodiversity and ecosystem function have been widely studied in recent decades in the world, the multi-rotation continuous planting eucalypt plantations ecosystem have not been studied. This study began at 1998, the . objectives of this study are to examine the relationship between plant species diversity with eucalypt tree growth, productivity, nutrient cycling, nutrient use efficiency, site productivity maintenance, community stability and sustainability in eucalypt plantations, by carrying out a long-term experiment in the different rotations of eucalypt plantations, and at the same time, provide a theory and guidance for high yield and high species diversity maintenance and sustainable management in eucalypt plantations. This study, without a doubt, plays an important role in the sustainable development of eucalypt plantations.Based on the long-term experiment research from 1998 to 2005, the study has main results and conclusions are as follows:By the methods of long-term experiment research, this paper studied the law of growth and development, characteristics of forest structure in Eucalyptus grandis×Eucalyptus urophylla (EGEU) plantations in different rotation stands from 1998 to 2005. The results indicated that the diameter breast height (DBH) and volume increment of eucalypt plantations have 2 growing-peak periods during a period of 1998-2005, the first is after planted 2 years, the second is after planted 5 years, the highest growing period of tree diameter and volume of the plantation was 2 years old and 5 years old, respectively. Both increment change obviously in peak and low during the period of 1998-2005. Eucalypt tree height growth has only one peak during the period of 1998-2005, at after planted 2-year. The curve of volume average increment and current increment was across at after planted 5-year. Based on the study, the growth and development of eucalypt plantation were classified a sapling stage, young stand stage, half-mature stand stage and mature stand stage. The change of diameter and tree height structure of eucalypt plantations with stands age follow the general law of pure forest, but the shewnees of curve of stand diameter distribution and tree height distribution in young stand stage were obviously to right side due to early fast growth of EGEU. The canopy structure of EGEU plantations was simple, LAI also wais low, and the first rotation stand was lower than that of second rotation stand. T-test results showed that there was significant difference in canopy structure (LAI: t=-4.348,α=0.0001; MFIA: t=-2.603,α=0.019) between first rotation and second rotation forest, but DBH increment (t=0.044,α=0.965), height increment (t=-0.280,α=0.781) and volume increment (t=-0.262,α=0.795) was not significant. It is indicated that continuous planting system was not significant effect on growth of the second rotation of eucalypt plantation.The study showed that EGEU is a tree of high-productivity, its average volume productivity and productivity in mature stands (7.3 years) is 20-21m~3/ha·a and 19t/ha·a, respectively. T-test results showed that there was not significant difference in biomass (t=-0.011,α=0.991) and productivity (t=0.077,α=0.940). It is indicated that continuous planting system was not significant effect on biomass and productivity of the second rotation of eucalypt plantation. Biomass and productivity of bole stem, bole bark, branch and root in eucalypt plantations increased with the increasing of stand ages, but leaf increased in the young stand stage and decreased in half-mature stand stage and mature stand stage. At the mature stand stage, the biomass of root and leaf increased slowly even though appeared negative growth that influenced the sustainability of productivity of eucalypt plantation. The biomass ratio of bole bark, branch and leaf increased tendency by influenced continuous planting. Continuous planting of Eucalyptus plantations resulted in a significant reduction in biomass and productivity of understory vegetation. The biomass and productivity of understory vegetation in second rotation stand was less 70% than that in first rotation stand. The biomass and productivity of understory vegetation in first rotation stand appeared an increasing tendency, but decreasing tendency in second rotation stand from voung stand stage (2-3 ages) to mature stand stage (6-7 ages). Continuous planting of Eucalyptus plantations resulted in a significant reduction in plant species diversity, species richness and Shannon-Wiener index in second rotation stand was less 39.39% and 17.76% than that of first rotation stand. Jaccard index and Cody index of first rotation stand significantly was higher than the second rotation inβ-diversity measures of the community. Coefficient of similarity in community was higher within-rotation (60%) and lower inter-rotation (30%) in eucalypt plantations. It is indicated that the continuous planting of eucalypt plantation resulted in many species loss. Continuous planting not only decreased the species diversity but also changed the composition of species, life-form, growth-form in community and plant life-history strategy. The multi-rotation continuous planting of Eucalyptus plantations is advantageous to herbaceous and r-strategy species and disadvantageous to woody plants and k-strategy species, and thus understory vegetation tends to be dominated by light-demanding grasses. With the increased stand age, woody plant cover, herbaceous cover, plant richness (S), Shannon-Wiener index (H’), Simpson index (D) in both rotations increased or recovered, but their recovering rate was obviously different. The woody plant cover, herbaceous cover, S, FT and D in first rotation stand restored more quickly than those of second rotation stand, and the early stage of stand restored faster than the late stage. Although such differences between 1st rotation and 2nd rotation stand become smaller over the stand age, the understory diversity in Eucalyptus plantations may not be sustainable because the understory vegetation in plantations can not be restored the same level of understory vegetation in the pre-rotation. The change regulation of soil seed bank in different rotations was a similar with understory vegetation. Continuous planting resulted in reduction of soil seed bank reserves and density. Soil seed bank and vegetative propagation in the soil is a basis of species diversity maintaining in industrial Eucalyptus plantation. Therefore, a new hypothesis, initial plant diaspora, on the maintaining mechanism of species diversity in eucalypt plantation was put forward. In a rotation of management, species richness in industrial plantation is determined by initial plant diaspora in the soil due to few seeds are introduced to the soil seed-bank in a rotation. The species with high-competed or only with seed (fruit) dispersal was lost by strong disturbance (e.g., the clearing site by burning, the soil preparation by mechanically ploughed) that resulted in reduction of initial plant diaspora in the next rotation stand (land). Therefore, the species richness of the continuous planting forest floor decreased in rotation by rotation.This study indicated that nutrient structure of EGEU belongs to a tree species of Ca>N>K>Mg>P, with strong concentrated Ca in mature individual. The order of tree parts for N, P, K, Mg concentration was the same, leaf>bole bark>branch> root > bole stem, Ca-concentration was very different, followed bole bark > leaf> branch >root >bole stem. Five nutrient elements concentrations, generally, increased with increasing continuous planting rotation, and decreased with increasing with tree age in N, P, K concentration, and increased with increasing tree age in Ca and Mg concentration. EGEU plantation was characterized as a fast of nutrient accumulation, high of nutrient retention ratio (account for 94%) and low of nutrient return ratio (account for 6%). Five nutrient elements (N, P, K, Ca and Mg) bio-cycle ratio of EGEU plantation was 40.40-41.81%. The bio-cycle ratio of N and P was the highest in the nutrient cycle of EGEU plantation, K and Mg was the middle, and Ca was the lowest. The nutrient utilized per biomass of EGEU plantation was lower, to produce per 1t biomass needed to utilize nutrient 5kg including N, P, K, Ca and Mg, and to produce per 1t bole wood only needed to utilize nutrient 2kg above nutrient. Although nutrient utilized per biomass of EGEU plantation was lower, the total biomass of EGEU plantation was higher and hence, the nutrient consumption of eucalypt plantation was higher too. The study results also showed that continuous planting system was not significant effect on nutrient accumulation of the second rotation of eucalypt plantation. On the contrary, continuous planting system was significant effect on nutrient accumulation of shrub layer and herbaceous layer. The nutrient accumulation of shrub layer and herbaceous layer in the second rotation eucalypt plantation was less 115% and 85% than that in first rotation eucalypt plantation. Continuous planting has the effects of decreasing soil bulk density, increasing soil porosity and aeration and retained water in eucalypt plantation, but these effects was not sustainable and generally maintenance 3-4 years after planted. Continuous planting has a positive effect and negative effect, but negative effect was more obviously. Continuous planting resulted in a significant reduction of soil nutrient of 0-20cm soil layers, in which Ca and Mg decreased the most obviously. Continuous planting of eucalypt plantation also decreased soil pH and resulted in soil acidification.Based on measuring the species composition, biomass and nutrient etc. in the 36 plots (each 100m2), the relationship between plant species diversity and ecosystem function has been researched using three measures of species diversity, and four measures of ecosystem function. The results showed that a relationship between species diversity indices and biomass of tree parts of eucalypt plantation was not close, but species diversity indices with biomass of absorbing root (diameter is less 0.6cm) were closely and extreme closely negative relation. It is indicated that the biomass of absorbing root decreased significantly with increasing of species diversity of understory vegetation. Plant species diversity effected significantly on the biomass of shrub layer and herbaceous layer, and species diversity increased a biomass and productivity of understory vegetation. Plant species diversity effected significantly on the nutrient use efficiency (NUE) of tree layer, shrub layer and herbaceous layer. However, different layer of community and nutrient element were different in relationship between species diversity and NUE. Species richness, Shannon-Wiener index and evenness index with NUE of N, P, K and Ca of tree layer were a positive relation of significance and extremely significance, but Mg was a significant negative relation. The result showed that species diversity improved the NUE of N, P, K and Ca of the tree layer, and decreased the NUE of Mg of the tree layer. The study also found that species richness with NUE of plant species of shrub layer were a positive relation of extremely significance. Except for species richness with K element was a closely relation in the herbaceous layer, another were not closely relation. Species richness increased the NUE of plants. The species richness of the community was higher, the species resilience, vegetation covering resilience, biomass resilience and soil nutrient resilience was higher. Species diversity was advantageous to improve a resistance and resilience of community and strengthen community stability. Due to strong disturbance with continuous planting of eucalypt plantation effected obviously on the community stability that threaten a sustainability of species diversity and soil fertility in eucalypt plantation ecosystem. Therefore, a new hypothesis, resource and space classifying management, on the maintaining mechanism of high species diversity and high productivity in eucalypt plantation were put forward.更多还原