Water use by fast-growing Eucalyptus urophylla plantations in southern China

Tree growth, water use, climate and soil water conditions were monitored over 12 months in two 3-4-year-old Eucalyptus urophylla S.T. Blake plantations on the Leizhou Peninsula of southern China. The Hetou plantation was established on a sandy soil of sedimentary origin with low water storage capacity, and the Jijia plantation was established on a clay soil formed on basalt. Sapwood area was approximately 50% higher at Jijia than at Hetou because of differences in plant spacing (1994 versus 1356 stems ha(-1)). Annual water use, assessed by heat pulse measurements, was 542 mm at Hetou and 559 mm at Jijia, with mean sap flux densities of 2772 and 1839 l m(-2) day(-1), respectively. Limitations to water use, imposed by climatic and soil factors, were quantified by analysis of daily canopy conductance in relation to daytime vapor pressure deficit (VPD) and soil water content. Similar annual water use at the two sites was a result of higher VPD and soil water availability at Hetou compensating for the greater sapwood area at Jijia. Potential annual water use in the absence of soil water limitation was estimated at 916 mm at Jijia and 815 mm at Hetou. Higher water availability during the dry season and early wet season at Hetou than at Jijia was the result of deep root systems. The results imply that water use by plantations on soils with high water availability and in areas of high VPD may be reduced by establishment at wider spacing. The environmental cost of water use by plantations must be weighed against their economic and environmental values to determine an appropriate mix of forestry, agriculture and other land uses in regions where water resources are limited.     

Sustainable plantations of high-yield shape Eucalyptus trees for production of fiber: the Aracruz case

The importance of planted forests for human communities is evident today because of the increase in world population year after year. In order to supply the constantly increasing requirements for wood for fiber, energy, civil construction, resin, latex, and other needs, new forests have been established by adopting new concepts of technology. These forests, especially those with fast-growing and short-rotation species, incorporate the objectives of quality, productivity, and environmental protection.The Eucalyptus plantations established by Aracruz Celulose S. A. to produce pulpwood have strongly contributed to the evolution of forest science, especially in the fields of silviculture, propagation, improvement, genetics, biotechnology, nutrition, environment, and disease control related to eucalypt species. Significant investments in research and development were required, as well as technological adaptation to the local conditions. Results of these investments in productivity and quality defined the technical feasibility to build a pulp industry and its expansion to reach 1,025,000 t/yr of bleached pulp.As a result of these advances, the mean increment of pulp productivity has been improved significantly -- from 5.9 air-dried t/ha/yr to 10.9 t/ha/yr (Fenton and Romero 1995; Bertolucci et al. 1995). This became possible by selecting trees more adapted to each site, with high yields of high quality fiber, and with eucalypt clonal plantations with an average rotation age of 7 years. Additional studies of Aracruz have promoted advances in industrial processes, as well as definition of fiber characteristics of mother trees to be in attendance with requirements of markets, thus providing an important competitive advantage (Campinhos and Cláudio-da-Silva 1990).The care for the environment -- both forest and industrial -- has been always present and has been the key point for the good performance of the project. This fact has created a world emulation that strongly contributes to decreasing the pressures on native forests, as a result of the consequent utilization of smaller land areas to produce a desired wood volume. This total project is an example of domestication (Eldridge et al. 1994) of the forest genus Eucalyptus with exceptional qualities and represented by more than 500 species and hybrids (Campinhos et al. 1992).     

尾巨桉扦插技术

用广林尾巨桉(Eucalyptus urophylla×Eucalyptus．grandis)11号组培苗营建采穗圃,以IBA、NAA和 ABT6号生根粉进行扦插育苗试验,结果表明:以400 mg／kg的ABT6号生根粉诱导穗条生根,生根率达94％, 且根系发达,苗木生长健壮;基质红心土的扦插效果较好;春秋季有利于进行扦插繁殖。     

人工长白落叶松优良单株母树选择技术

文章简述了长白落叶松优良母树选择的意义,优良母树选择、分级的标准、方法。     

尾叶桉的组织培养及植株再生

研究了以尾叶桉(Eucalyptusurophylla)优树(U6无性系)无菌苗的叶子和茎段作为外植体诱导愈伤组织、丛生芽发生以及植株再生的过程。通过多种生长调节剂不同浓度组合的对比试验,确定了U6快繁体系的最适宜培养条件:(1)愈伤组织诱导培养基:MS 1-2mg/L2,4-D;(2)芽增殖培养基:MS 0.5mg/L6-BA;(3)生根培养基:1/2MS 2.0mg/LNAA。     

从化桉树、南洋楹速生丰产林的生长表现调查

本文通过对广州市北部山区从化市2年半生的桉树、南洋楹速生丰产林的生长表现进行调查,结果表明：在两个标准样地间,桉树、南洋楹的平均胸径以及南洋楹的平均分枝数无显著差异,而平均树高差异显著,说明桉树、南洋楹的胸径生长以及南洋楹的分枝数受遗传控制的程度较高,而树高生长受环境条件影响较大;桉树与南洋楹在平均胸径与平均树高两个性状上均达到极显著差异,并且这两个性状的变异系数,桉树均比南洋楹小,说明桉树的胸径生长和树高生长均比南洋楹稳定,受环境条件的影响较小,所能适应的立地条件和环境条件较南洋楹广泛。     

尾叶桉人工林二元材积表的研制

通过收集福建省永安市不同林龄、立地、密度的尾叶桉人工林林分的样木资料,采用多模型优选法和逐步回归法研制尾叶桉人工林二元立木材积表,并用相关指数、剩余标准差、平均系统误差、平均相对误差绝对值、预估精度作为评价指标,应用灰色关联分析法建立综合评价指数,评价模型优劣。经检验,所编的材积表完全符合生产上的精度要求,且理论基础扎实,编表结果可靠,可在森林资源调查中推广应用。     

巨桉、尾叶桉及其无性系在思茅地区引种栽培适应性论证

通过对巨桉、尾叶桉生物学特性、省外栽培情况、思茅地区小面积引种情况、省外栽植地点和引种地的立地条件进行分析比较，选择气候因子进行相似优先比论证，得出思茅地区在一定范围内大面积引种巨桉、尾叶桉是可行的结论。     

巨尾桉无性系人工林不同规格木材出材比例的测定

根据短周期巨尾桉人工林标准地伐倒木调查资料,编制对应林分平均胸径的不同规格原木比例表格,以方便查对一定胸径林分对应的不同规格原木出材比例,较为准确地估算林分林木的经济价值。     

生长延缓剂对巨尾桉苗生长控制试验

本试验目的主要是探讨生长延缓剂对桉苗高生长控制作用,采用多效唑(PP333)和矮壮素(CCC)对巨尾桉苗处理,在30、60天后测定株高,结果说明即使以200μg/g浓度处理对巨尾桉苗的高生长均具明显延缓作用,延缓作用在供试浓度范围内有随浓度升高而加剧的趋势,而且浓度过高会对植物产生严重药害。药剂对苗木在种植后的生长是否有延缓作用仍需进一步研究,因此在桉树育苗时慎用上述药剂。     

Density effect and self-thinning in Eucalyptus urophylla stands

Density effects on the growth and self-thinning of Eucalyptus urophylla stands were examined for 7 years.The reciprocal equation of the competition-density(C–D)effect was used to describe the C–D effect in even-aged pure stands of E. urophylla during course of self-thinning and showed a good fit to the data. The time trajectories of mean stem volume-density nearly paralleled the y-axis during early growth stages of stands, and then began to curve left. Finally, the mean stem volume-density trajectories of the low-, middle-and high-density stands tended to follow the self-thinning lines with slopes of-2.01,-1.90 and-1.99, respectively. With increasing physical time t, the biological time s increased rapidly during early growth stages and became slow gradually during later growth stages. Realized density-initial density curves tended to become more or less flat with increasing initial density, indicating the existence of an asymptotic value for density at a given time. The coefficient e, the reciprocal of which represents the asymptotic density at a given time,increased with increasing biological time s, indicating that the asymptotic density decreased with increasing stand age.Final yield Y(t) increased gradually with increasing stand age.     

Explaining growth of individual trees: Light interception and efficiency of light use by Eucalyptus at four sites in Brazil

The growth of wood in trees and forests depends on the acquisition of resources (light, water, and nutrients), the efficiency of using resources for photosynthesis, and subsequent partitioning to woody tissues. Patterns of efficiency over time for individual trees, or between trees at one time, result from changes in rates photosynthesis and shifts in the relative partitioning to wood. We measured the production ecology (stem growth, light interception, and light use efficiency) to explain patterns of growth among trees within plots through stand development, and tested three hypotheses: (1) dominant trees have higher light use efficiency than subordinate trees; (2) lower variation in the size distribution of trees within plots allows higher light use efficiency; and (3) uniform stand structure and high light use efficiency reduce the age-related decline in tree growth. The experiment used clonal plantations of Eucalyptus at four locations in eastern Brazil. Irrigation and fertilization treatments ensured the major resource limitation for tree growth would be light supply. The influence of variation in the sizes of trees within plots was tested by comparing plots with all trees planted in a single day (uniform treatment) with plots where planting was spread over 80 days (heterogeneous treatment). Light interception per tree was simulated with the MAESTRA model. Across sites, treatments and whole-rotation stand development, dominant trees showed higher rates of stem growth, light interception, and light use efficiency than subordinate trees (supporting the first hypothesis). For example, dominant trees (80th percentile rank) at the end of the rotation grew four-times faster than suppressed trees (20th percentile rank), as a result of 2.1-fold greater light interception, and 1.8-fold greater stem growth per unit of light interception. In some cases, greater variation among tree sizes within plots led to lower efficiency of light use by average-size trees, providing mixed evidence for the second hypothesis. Greater uniformity of sizes of trees within plots did not substantially mitigate the decline in stem growth from mid-rotation to the end of the rotation, refuting the third hypothesis. The high efficiency of dominant trees underscores the marginal contribution of subordinate trees to total stand growth, and should spur further work on thinning to increase growth and lengthen rotations for dominant trees.     

EST—CAPS标记在尾叶枝和细叶枝遗传图谱构建中的应用

以已构建的尾叶桉和细叶桉RAPD连锁图谱为基础，利用CAPS技术对54个细叶桉EST序列在尾叶桉和细叶桉遗传图谱上的定位研究表明：7个EST序列在作图群体中呈等位片段多态性，包括母本尾叶桉特有的3个（其中1个偏分离）、父本细叶桉特有的2个和父母本共有的2个；共有4个EST—CAPS标记整合到尾叶桉RAPD连锁图谱，分散于不同的连锁群，各连锁群大小均有小幅增加；细叶桉RAPD连锁图谱上也整合了4个EST—CAPS标记，分散于不同的连锁群，各连锁群大小均有不同程度的增加；另外，尾叶桉上的1个偏分离标记未整合到任何连锁群。EST—CAPS可以有效用于桉属树种遗传图谱构建。     

广西巨尾桉2年生人工幼林生物量及生产力研究

在对广西沙塘林场巨尾桉2年生人工林调查基础上，按标准木法测定巨尾桉人工幼林生物量，建立其估算模型，计算出巨尾桉人工林分的生物量和生产力，分析各器官生物量分配规律及林分生产力水平。结果表明，2年生巨尾桉人工林年生物量为16.57 t/hm^2，其中，干、根、叶、枝、皮各器官生物量所占比例依次为46.67％、16.85％、14.62％、12.16％、9.62％。应用建立的估算模型估测巨尾桉人工幼林生物量，其相关程度达显著水平。     

尾叶桉丛生芽和生根的诱导

为了建立优良尾叶桉无性系组织培养与再生体系．培育速生耐寒转基因桉树新品种，研究了以广西林业科学研究院提供的尾叶桉（Eucalyptus urophylla）无菌苗为材料，选取带腋芽茎段作为外植体．诱导丛生芽的发生以及植株再生的过程。通过多种生长调节剂不同浓度组合的对比试验，筛选出尾叶桉茎芽分化的最佳培养基为MS＋ZT0．5mg／L＋NAA0．4mg／L；芽继代增殖最佳培养基为MS＋ZT0．5mg／L＋NAA0．2mg／L；适合生根的培养基为1／2MS＋NAA2．0mg／L＋IBA0．3mg／L。     

尾叶桉二代测定林家系的综合评选

对49个家系的尾叶桉测定林各年度生长性状进行分析与遗传评估,结果表明：各年度树高、胸径和材积生长量在家系间存在极显著差异;分枝、干形和保存率在家系间存在显著差异;树高、胸径、单株材积、保存率的累积贡献率达95．45％,此4因子是综合评定家系时采用的;以家系群体平均选择指数I0为基准,两种选择标准下的家系材积增益,3年生时为7．63％～15．80％,4年生时为3．92％～10．39％,5年生时为6．08％～23．53％;以选择指数为指标,5年生时人选的5个优良家系是：109,113,66,81和100号。     

蒸汽爆破尾叶桉木材的化学组分及纤维素酶水解工艺

采用蒸汽爆破技术处理尾叶桉木材，研究蒸汽爆破对其主化学成分的影响，以及爆破材料用纤维素酶水解的工艺，确定了水解糖化条件：温度50qC，pH值4．8，酶用量25FPIU／g底物，底物浓度2％。结果表明，蒸汽爆破过程溶解出一定量的半纤维素和木质素，而纤维素基本不受损失，有利于提高酶解率；爆破前用硫酸预处理，木质素脱除率和木聚糖分解率在同样的爆破压力下比未用硫酸预处理的高。在最优的水解条件下，硫酸预处理，2．2MPa爆破的尾叶按木材多糖水解率达到82．43％，比未用硫酸预处理的提高36．86％。     

尾叶桉家系自由授粉子代性状的分析

对尾叶桉39个子代生长性状、形质性状进行差异分析和遗传分析,结果表明:各性状历年观测数据在家系子代间差异均极显著,家系遗传力大于单株遗传力,生长性状间表型、遗传和环境相关紧密,分枝与各生长性状呈紧密的正相关.4.5年生时生长最好的No.33号家系子代的单株材积达0.048 17 m3,是最差子代No.36号的179.53%,是群体均值的127.40%.共有31个家系子代生长表现优于两个对照.运用指数选择法对家系进行多性状综合选择,选出4个优良家系和6个生长慢、形质差的家系.     

Does reverse growth dominance develop in old plantations of Eucalyptus saligna?

Patterns of stand growth and dominance among individual trees change through stand development. We tested a prediction that large, old plantations of Eucalyptus saligna (Sm.) in Hawaii and Brazil would show a pattern of “reverse” growth dominance, with the largest trees contributing more to stand biomass than to current stand increment. This pattern might develop if the largest trees accounted for a large portion of the total resource use of the stand, but were less efficient at utilizing resources to produce stemwood. The 70-year-old plantation in Hawaii had a stem mass of 610 Mg/ha, compared with 325 Mg/ha in the 66-year-old Brazil plantation. Cumulative frequency plots for both sites showed that dominant trees comprised a very large proportion of total stand mass; the largest 20% of the trees accounted for 50% and 30% of the total stand mass in Hawaii and Brazil, respectively. Contrary to expectations, the largest trees continued to produce a disproportionately large amount of total stand growth, with the largest 20% of trees accounting for 60% (Hawaii) and 40% (Brazil) of stand growth. The frequency distributions resulted in positive growth dominance coefficients (similar to Gini coefficients) of 0.14 for Hawaii and 0.09 for Brazil, rather than negative values that would indicate that reverse growth dominance. The failure of these monoculture Eucalyptus stands to develop reverse growth dominance contrasts starkly with a variety of studies with pine species, which tend to show neutral-to-reverse growth dominance. Indeed, continued dominance of large trees suggests the trees might respond well to silvicultural treatments such as thinning or fertilization. Future work that contrasts patterns of growth dominance among species will be important as a foundation for developing generalizations about trends in growth dominance with stand development.