Modelling agroforestry systems of cacao (Theobroma cacao) with laurel (Cordia alliodora) and poro (Erythrina poeppigiana) in Costa Rica III. Cycles of organic matter and nutrients

Models for cycles for organic matter and nutrients element (N, P, K, Ca and Mg) are presented for the agroforestry systems of cacao (Theobroma cacao) withCordia alliodora orErythrina poeppigiana in Turrialba, Costa Rica.For the models, system reserves (soil, humus, vegetation divided into leaves, branches, stems, fine roots, fruits) and transference between compartments (production and decomposition of litter residues) inputs (fertilizer, rainfall) and outputs (harvests) of the system are considered.The implications of the models are discussed in detail.Aspects of net primary production in the systems studied are considered.N fixation is calculated on the basis of balances. Analysis of soil water showed high variations that coincided with rainfall patterns and pruning of theE. poeppigiana.For part I see Vol. 4, No. 3, 1986 For part II see this issueAgroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesellschaft für Technische Zusammenarbeit), Turrialba, Costa Rica     

木聚糖酶解反应与膜分离技术研究

过程耦合是应用技术领域研究的热点之一 ,膜及膜分离技术的开发促进了过程耦合技术的发展。如膜超滤、膜萃取、膜蒸馏、渗透蒸发。在超滤膜反应器中木聚糖酶解制备低聚木糖的条件 :酶体积用量1 0 % ,木聚糖质量浓度 3 0 .0 g/L ,稀释率 1h-1,pH值 5 .0 ,反应温度 48℃ ,酶解时间 1 3 5min。在该条件下 ,低聚木糖得率、木糖得率、低聚木糖生产能力及低聚木糖与总糖之比分别为 2 8.5 % ,4.1 % ,3 .80g/ (L·h)和0 .87,并比较了分批加料、浓缩酶、常规反应器中酶解反应效果 ,浓缩木聚糖酶酶解结果表明 :木糖得率很低(0 .2 % ) ,低聚木糖得率为 3 5 .9%。     

关于货位可移动式货架立体仓库的探讨

在现有自动化立体仓库设备的基础上提出了一种新型的以货位可移动式货架为核心的自动化仓库作业方案,阐述了该模式下实现货物自动入库、出库的工作原理以及相关的拣货方法和机械设备的选择.并通过与几种不同设备的比较得出该方案的优势,为现代物流自动化仓库的发展提出了新的思想理念.     

Spatial pattern of the density of Armillaria epiphytic rhizomorphs on tree collar in an oak stand

The density of Armillaria gallica epiphytic rhizomorphs on tree collar was mapped in a young stand of pedunculate oaks (Quercus robur). A quick method to estimate the rhizomorph density was developed, investigating 19 trees, and was used in the subsequent study. The method consists of measuring the frequency of rhizomorphs present on a grid applied to an exposed small area of the tree collar. The pattern in tree collar rhizomorph density was closely related to the pattern of stump colonization by Armillaria and stumps were therefore important as inoculum sources. Rhizomorph density on tree collar showed a strong aggregated spatial pattern which could not be explained by variability in the soil characteristics, in particular waterlogging, or by a spatial pattern in tree vigour. Moreover, rhizomorph density on tree collar did not depend on their dominance status.     

Expression of a scorpion toxin gene <Emphasis Type="Italic">BmKit</Emphasis> enhances the virulence of <Emphasis Type="Italic">Lecanicillium lecanii</Emphasis> against aphids

Lecanicillium lecanii has been developed as biopesticides and widely used in the biological control of several insects in agricultural practice. However, the poor efficacy has blocked its application. The genetic manipulation has been proved as a useful tool to improve the virulence of entomopathogenic fungus. In this study, a scorpion toxin gene (BmKit) from Buthus martensi was cloned and transferred into L. lecanii and then its resulting activity against cotton aphids (Aphis gossypii) was assessed. The results showed that the engineered strain BmKit-12 grew significantly quicker than WT in host insects. The median lethal concentration (LC₅₀) for BmKit-12 was 7.1-fold lower than that for WT, and the median survival time (LT₅₀) for BmKit-12 was reduced by 26.5 % compared with that for WT. Although the conidial yield was reduced by 31.4 % on insect cadavers, the mycelia growth, sporulation, and conidia germination of BmKit-12 on plates were not significantly different from WT. Considering the lower amount of mycelia for BmKit-12 in host insects in late growth stage (fungal sporulation stage), we think the expression of BmKit may not affect the capability of sporulation. In conclusion, the expression of BmKit gene can significantly enhance the pathogenicity of L. lecanii against cotton aphids in a relatively cost-effective way.     

Delignification of cell walls of <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis> during alkaline nitrobenzene oxidation

To clarify the behavior of whole lignins in wood cell walls during alkaline nitrobenzene oxidation, the delignification process from cell walls in normal and compression woods of Chamaecyparis obtusa Endl. (Cupressaceae) was observed using ultraviolet and transmission electron microscopies. The lignin content conspicuously decreased to around 10% after 35min in normal wood. The lignin content in compression wood finally leveled off at aroumd 10% after 50min. In gel filtration of oxidation products in ethyl acetate, a high molecular weight fraction was prominent in extracts from the early stage of the reaction. As the oxidation progressed, the high molecular weight fraction became less prominent in both normal and compression wood. Changes in the weights of cell wall residues during reaction indicated that approximately half of the components other than lignin were also removed from the cell walls. This shows that the majority of lignin with relatively high molecular weight is removed from the cell walls together with polysaccharides in the early stage of the reaction and that further oxidative degradation occurs in solution in later stages. Only a small amount of the lignin with low molecular weight could be analyzed by gas chromatography.Parts of this report were presented at the 47th (Kochi, April 1997) and 48th (Shizuoka, April 1998) Annual Meetings of the Japan Wood Research Society, and at the Lignin Symposium, Sapporo, October 1997     

Ecological interactions,management lessons and design tools in tropical agroforestry systems

During the 1980s, land- and labor-intensive simultaneous agroforestry systems (SAFS) were promoted in the tropics, based on the optimism on tree-crop niche differentiation and its potential for designing tree-crop mixtures using high tree-densities. In the 1990s it became clearer that although trees would yield crucial products and facilitate simultaneous growing of crops, they would also exert strong competitive effects on crops. In the meanwhile, a number of instruments for measuring the use of growth resources, exploratory and predictive models, and production assessment tools were developed to aid in understanding the opportunities and biophysical limits of SAFS. Following a review of the basic concepts of interspecific competition and facilitation between plants in general, this chapter synthesizes positive and negative effects of trees on crops, and discusses how these effects interact under different environmental resource conditions and how this imposes tradeoffs, biophysical limitations and management requirements in SAFS. The scope and limits of some of the research methods and tools, such as analytical and simulation models, that are available for assessing and predicting to a certain extent the productive outcome of SAFS are also discussed. The review brings out clearly the need for looking beyond yield performance in order to secure long-term management of farms and landscapes, by considering the environmental impacts and functions of SAFS.

     

Forest resources and environment in China

Covering a vast territory, China is rich in forest resources and diversified environments. The changes in forest resources have a direct bearing on environmental quality. This paper gives a detailed account of the dynamic change in forest resources in China, including the overall process of forest evolution, the status quo, and features of the existing forest resources and the development and use of major forest resources. In addition, it analyses the current situation of China’s environment and explores the main contributing factors based on the overall environmental situation. To achieve sustainable management of forest resources and improve the environment in China, the Chinese Government attaches great importance to the protection and development of forest resources as well as to environmental development and improvement. The paper gives an overview of current thinking for sustainable forest resource and environmental development in the future and highlights the current focus of efforts toward this objective.     

Growth performance and management of a mixed rainforest tree plantation

Monoculture plantations of Pinus, Eucalyptus and Acacia have beenestablished on rainforest lands throughout the world. However, this type of reforestation generally supplies low quality timber and contributes to landscape simplification. Alternatives to exotic monoculture plantations are now beginning to gain momentum with farmers and landholders attempting to establish a variety of rainforest trees in small plantations. When compared to the well studied commercial species, knowledge concerning the growth and management of many of these rainforest species is in its infancy. To help expand this limited knowledge base an experimental plantation of 16 rainforest tree species in a randomised design was established near Mt. Mee, in south-eastern Queensland, Australia. Changes in growth, form (based on stem straightness, branch size and branchiness), crown diameters and leaf area of each species were examined over 5 years. Patterns of height growth were also measured monthly for 31 months. Species in this trial could be separated into three groups based on their overall growth after 5 years and their growth patterns. Early successional status, low timber density, high maximum photosynthetic rates and large total leaf areas were generally correlated to rapid height growth. Several species (including Araucaria cunninghamii, Elaeocarpus grandis, Flindersia brayleyana, Grevillea robusta and Khaya nyasica) had above average form and growth, while all species in the trial had considerable potential to have increased productivity through tree selection. As canopy closure occurred at the site between years four and five, growth increments declined. To reduce stand competition a number of different thinning techniques could be employed. However, simple geometric or productivity based thinnings appear to be inappropriate management techniques for this mixed species stand as they would either remove many of the best performing trees or nearly half the species in the trial. Alternatively, a form based thinning would maintain the sites diversity, increase the average form of the plantation and provide some productivity benefits.     

Organogenic responses of Pinus pinea cotyledons to hormonal treatments: BA metabolism and cytokinin content

Isolated cotyledons from mature Pinus pinea L. embryos were cultured in vitro in a factorial combination of 4.4, 10 and 44.4 microM N6-benzyladenine (BA) for 2, 4, 8, 16 and 35 days to optimize shoot regeneration. Incubation of explants in 44.4 microM BA for 4 days, in place of the standard incubation in 4.4 microM BA for 35 days, reduced the entire culture period to 4 weeks. Shortening the culture period had no significant effect on the caulogenic response or the number of buds formed per cotyledon. To establish the relationship between key moments in the caulogenic process induced by 4.4 microM BA and the endogenous concentrations of the active forms of BA and other isoprenoid-type cytokinins (CKs), we examined uptake, metabolism and amount of BA, as well as the amounts of zeatin, dihydrozeatin and their ribosides in P. pinea cotyledons after 1, 2, 6, 12 and 24 h, and 2, 4, 8, 16 and 35 days of exposure to 8-[14C]BA. Uptake and release of BA were associated with water movement between explants and the medium during the first 8 days of culture. The interconvertible forms of BA were the main metabolites formed in the tissues. Inactivation of BA as a result of conjugation or oxidation was insignificant. The endogenous concentration of BA + N6-benzyladenosine was 20-fold higher than the exogenously applied BA during the competence acquisition phase (Days 0-3). The concentration of isoprenoid-type CKs also increased 16-fold and then decreased during this time. Induction of shoot buds (Days 4-8) was characterized by a second peak of BA uptake by explants that triggered the synthesis of N6-benzyladenosine-5 -monophosphate and by the maintenance of isoprenoid-type CKs. Reestablishment of CK homeostasis marked the shift from the induction phase to the shoot development phase in this organogenic process (Days 8-12).