果树组织培养中褐化现象的研究进展

介绍了果树植物组织培养褐变的发生机理，发生褐变的主要果树种类，综述了近年来果树植物组织培养中参与褐变现象的酚类物质、酚氧化酶以及多种影响因素的研究进展。     

兴安落叶松过伐林枯立木分布格局特征分析

以内蒙古根河林业局潮查林场境内的在20世纪80年代初主伐利用后形成的兴安落叶松过伐林为研究对象,利用兴安落叶松林8块标准地每木定位数据,分析林木分布格局和样方(5 m×5 m)林木株数对枯立木株数影响,探讨了林分大树和更新幼树位置与枯立木位置的关系,阐明了枯立木分布格局形成机制。结果表明:1)各树种枯立木比例,随树种组成成数增加而增大。枯立木主要在更新幼树阶段形成,径级分布集中在4径阶以下,其株数占总数的比例平均达82.2%。在更新幼树(含枯立木)中,生成枯立木的比例平均达8.8%。2)枯立木分布格局为聚集分布。林木分布格局、样方林木株数和更新株数与枯立木株数有显著正相关关系,林木分布格局对枯立木分布格局无显著影响。林木聚集度越大,形成枯立木的可能性越大,数量也就越多。3)枯立木位置与更新幼树和大树位置有显著相关关系。主要表现为落叶松和白桦相互关系。枯立木出现位置主要在大树和更新幼树集聚区域。大树对枯立木形成影响较更新幼树大,而且均以落叶松较白桦明显。白桦更新幼树对落叶松枯立木的形成,无显著影响。受影响的枯立木主要是枯立木株数中所占比例和树种组成成数较高的树种。影响枯立木位置的林木主要取决于其样方内位置和林木株数。     

Observations on the rooting patterns of some agroforestry trees in an arid region of north-western India

The present study deals with root architecture of 6-year-old trees of 9 indigenous and 3 exotic species growing in arid climate of north-western India. Observations, made on excavated root systems (3 tree replicates of each species) showed large variation in horizontal and vertical spread of roots. In Morus alba, Melia azedarach and Populus deltoides, the roots were confined to 80 cm, while in Prosopis cineraria, Acacia nilotica and Eucalyptus tereticornis, roots penetrated more deeply to 233 cm. The number of total roots ranged from 103 in Acacia catechu to 1932 in Eucalyptus tereticornis, and 62 to 80% of the roots were less than 2 mm in diameter. The primary roots were more horizontal than the secondary roots. The total root biomass varied from 2.2 kg in Acacia catechu to 30.6 kg^–1 tree in Populus deltoides, and top 30 cm soil contained 42 to 78% of the total biomass. The implications of the results are discussed in the context of the ecological niche of the species, and its usefulness in agroforestry systems.     

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 issue Agroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesellschaft für Technische Zusammenarbeit), Turrialba, Costa Rica     

The dehesa: an agrosilvopastoral system of the Mediterranean region with special reference to the Sierra Morena area of Spain

A multidisciplinary team undertook a six-year investigation on the agro-ecological and socio-economic aspects of the dehesa system in the Sierra Norte area, a part of the Sierra Morena of the Sevilla Province, Western Andalusia, Spain. This paper summarizes its findings on the various agro-ecological features of the system and evaluates the system's functional aspects vis-a-vis the trends and developments in land use in the region over the past few centuries. The synergistic effects of tree cover on understorey grassland vegetation is discussed in terms of soil fertility build-up and favourable micro-climatic and hydrological features, and the potential use of this information in future research and development programmes to improve the dehesa system in the Mediterranean region is outlined.     

Characteristics and decomposition rates of pruning residues from a shaded coffee system in Southeastern Brazil

In the Zona da Mata Mineira of Southeastern Brazil the development of sustainable land requires the integration of crops with trees. The objectives of this study then were to (i) characterize prunings from the main tree species in an agroforestry system; (ii) determine the effects of the physical and chemical characteristics of the prunings on their decomposition patterns in the laboratory; (iii) assess the effect of mixing leaves of different species on decomposition rates; and (iv) propose a decomposition index for the residues studied. The study was carried out with pruning residues from Cajanus cajan, Solanum variable, Cassia ferruginea, Piptadenia gonoacantha, Croton urucurana, and Melinis multiflora. The materials were characterized for total C, N, P, Ca, Mg and K contents; lignin, cellulose, hemicellulose and soluble polyphenols contents. The pruning residues had high polyphenols and lignin contents, high C:N and C:P ratios, and low contents of Ca, Mg, and K. The low decomposition rates of the prunings were related to the P, K, hemicellulose and polyphenol contents. The rates of N mineralization from most of the residues indicate that there is a potential to supply the needs of a crop of maize. The residues of some species, if decomposed alone, would not supply sufficient nutrients, and need to be mixed with leaves of other species.This revised version was published online in November 2005 with corrections to the Cover Date.     

The biology, ecology and agroforestry potential of the raintree, Samanea saman (Jacq.) Merr.

Samanea saman (Jacq.) Merr. (syn. Albizia saman (Jacq.) F. v. Muell.) is a large tree, native to tropical America, which has now become widespread throughout the humid and subhumid tropics. Although noted as a promising agroforestry species, there is little specific research that substantiates this potential. On the basis of a review of its biology, ecology and recorded uses, it is concluded that the most appropriate use for S. saman would be in an extensive silvopastoral system for cattle production. The tree provides excellent protective shade, and produces highly palatable pods that are suitable as a dry season feed supplement. Additionally, there are reports of enhanced grass production beneath its canopy indicating a potential role in maintaining or improving the productivity of tropical grasslands. It is concluded that the tree should receive more research attention, focusing particularly on its interaction with the herbaceous understorey and the identification of provenances adapted to a variety of environmental conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genetic evaluation of Prosopis alba (algarrobo) in Argentina for cloning elite trees

Algarrobo (Prosopis alba) is an important nitrogen-fixing tree adapted to the semiarid regions of northwestern Argentina. The tree provides fuelwood and dimensionally stable lumber for flooring and furniture; its pods that have a high sugar content are consumed by livestock and humans. P. alba has been one of the most heavily harvested species. This paper reports on the evaluation of a nine-year-old Prosopis alba progeny trial containing 57 half-sibling families of eight provenances in northwestern Argentina (of the 1,596 trees planted, 1,289 survived in 1999). Considering the multiple uses of P. alba, the selection criteria included: total biomass production (from basal diameter using regression equations), height, rate of pod production, and pod sensory characteristics. The family-narrow-sense-heritability was 0.487 for height. 0.548 for biomass production, and 0.244 for pod production. In 1998, 12 of the 1,289 trees were more than 4 m tall and had more than 1.75 kg pods per tree; and their pods had a sweet or very sweet non-astringent taste. Scions from these 12 trees were successfully grafted onto unselected P. alba rootstock. These are currently being used to produce rooted cuttings. The pod production, biomass, and height of the 12 clones ranged from 6.55 to 14.4, 1.57 to 13.5, and 1.29 to 1.70 times the respective population means. The genetic gains of 13.5%, 77%, and 147% for height, biomass, and pod production respectively are greater than genetic gains for other tree species and are probably due to the great genetic variability in the local population and the lack of any prior genetic improvement program.This revised version was published online in November 2005 with corrections to the Cover Date.     

林木遗传工程及木质素的生物合成调节(英文)

林木遗传工程有利于保存林木遗传资源，改善全球气候，减轻自然林的过度采伐和满足人类日益增长的林木产品需求。控制林木真菌、病毒病、虫害和杂草的遗传工程方法正被广泛地研究和应用。尽管转基因林木的历史不长，种类不多，但它有广泛的应用前景。目前，抗除草剂基因、抗虫基因以及和木材质量相关的基因已被分离并应用于林木遗传工程。植物分子生物学和基因组学中的新技术使得高效林木遗传改良成为可能并将促进这些技术的商业化应用。木质素的应用已有一百年的历史，但木质素生物合成的全过程并不完全清楚。有关松树自然突变体和转基因林木的最新研究结果表明，木质素的生物合成是一个可以调节的过程。这些发现对完善木质素的生物合成途径、加深对木质素前体生物合成途径的理解和通过遗传工程改善木材质量有促进作用。本文综述了林木遗传工程在这些领域中取得的一些进展。     

Micronutrient, magnesium and phosphorus effects on biomass and leaf tissue nutrient concentrations of field grown Leucaena leucocephala

To optimize biomass and crude protein (CP) production for leucaena (Leucaena leucocephala) in southern Texas, field trials were conducted with treatment combinations of three levels of phosphorus (P) , two levels of Mg and two levels of soluble trace element mixture (STEM). The P was banded in the soil while the Mg and micronutrient blend were applied to the foliage. A combination of P (22 kg ha^-1), Mg and STEM fertilizers significantly increased biomass from 2555 kg ha^-1 to 3028 kg ha^-1. This treatment was associated with an increase in leaf CP from 27.9% to 31.0%. P fertilizer had no significant effect on leaf P, but significantly increased leaf nitrogen (N) and leaf copper (Cu). A foliar spray of Mg significantly increased leaf N, P, and Cu. A foliar spray of a complete micronutrient blend increased leaf Cu. Biomass production was correlated positively (decreasing order) with leaf Cu, N, and Mg and negatively with Zn. Leaf N was positively correlated with leaf P and calcium. The critical tissue concentrations (CTC) (where 90% of predicted maximum leaf protein was obtained) were 0.18% and 4.49 mg kg^-1 for leaf P and Cu, respectively. This revised version was published online in June 2006 with corrections to the Cover Date.