营造速生丰产林的关键技术

为建设高档次速生丰产林,作者借鉴国外经验,提出6项关键技术措施,即:建立树木栽培种、选育优良无性系、突破繁殖技术、改革育苗方法、严格立地选择和配套栽培措施。     

美国国有林的发展与对策

文章回顾了美国国有林的发展历程,并介绍了一些重大历史事件。作者着重阐明了美国国有林的管理体制和技术经济政策。     

奥地利经营国有林的成功经验

我国国有林经营现在已陷入严重的资源与经济危困之中.奥地利国有林独立经营65年,1923年林木蓄积量为7 600万立方米,1987年已是13 900万立方米.每公顷可利用林蓄积量1923年平均为250m3,1987年已是324m3.国有林80%分布在阿尔卑斯山区,条件并不优越,但每公顷森林的产材量还在逐年增长,现在已达4.5m3左右.近百年来,奥地利对国有林坚持有计划采伐,对山地森林实行长伐期经营毫不动摇,把木材生产与改善森林状况密切结合了起来.1925年和1977年的《奥地利国有林法》明确要求,在保持森林公益机能的条件下,实行按商业原则经营,国有林局是经济实体,应做到自负盈亏.战后40余年,国有林局的林区道路密度每公顷已近24m,并拥有大量机械装备,仍是财政有盈余的企业.     

Identification of the variant C of β-lactoglobulin in sheep using a polymerase chain reaction-restriction fragment length polymorphism method

β-Lactoglobulin (β-LG) is the major whey protein in the milk of ruminants and is able to bind and transport small hydrophobic molecules. However, its biological role is mainly unknown (G odovac -Z immermann 1988). Previously three genetic variants have been found in sheep: A, B and C. The genetic variants A and B differ at amino acid position 20, where variant A has a His and variant B has a Thr (K olde and B raunitzer 1983). The variant C is a subtype of variant A with a single amino acid exchange of Arg→Glu at position 148 (E rhardt et al. 1989). The genotype β-LG BB was found to be associated with higher milk yield, whereas genotypes AA and AB had a higher milk protein and casein content as well as yielding more curd (G arzon and M artinez 1992). No data is available concerning the relationship between the β-LG C allele and production traits or milk properties. Since DNA-based genotyping has already been performed for alleles A and B (S chlee et al. 1993), the aim of the present study was to develop a DNA-based method for identifying the β-LG C variant. However polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) typing has been established (P rinzenberg and E rhardt 1999) recently, and this study shows an alternative method to detect β-LG C.     

Identification of the N-methylated analogs of the hallucinogenic amphetamines and some isomers.

The drugs 2-, 3-, and 4-methoxy-N-methylamphetamine, 3-methoxy-4,5-methylenedioxy-N-methylamphetamine, and 3,4-methylenedioxy-N-methylamphetamine are identified by spectroscopic techniques. The ultraviolet and mass spectra of isomers are similar, but proton magnetic resonance and infrared spectra are distinctly different, and reference spectra and data are provided. Gas-liquid and thin layer chromatographic systems for the analysis are discussed.     

Effect of conjugated linoleic acid on energy metabolism in growing-finishing pigs

The effect of conjugated linoleic acid (CLA) on energy metabolism was studied in a respiration experiment with 20 growing pigs. From 70 kg liveweight onwards the animals received isoenergetic rations containing 0 or 3% CLA on the basis of metabolic bodyweight. Between 95 and 100 kg liveweight the gas exchange of each animal was measured over 48 h in a respiration chamber. This was preceded by a 5‐day quantitative determination of faeces and urine. The heat production and energy retention of the animals were determined by the carbon–nitrogen balance technique and the RQ method. Additionally several parameters of blood serum were determined. CLA had no effect on digestibility and metabolizability of energy, nor were gas exchange and heat production (HP) of the animals affected by the treatment. Average heat production across all measurements was 628 kJ/kg W^0.75 in the control group and 636 kJ/kg W^0.75 in the CLA group. No difference in fat deposition was observed (control 386, CLA group 379 kJ/kgW^0.75). The N balance on the other hand was 2.2 g/day higher in the CLA‐supplemented animals. This caused retained protein energy, as a proportion of total energy retention, to increase from 24.2 to 25.8%. The ratio of retained protein energy to fat energy was 10% higher in the CLA‐treated animals than in the controls. Body mass increase over the trial as a whole was unaffected (control 27.6, CLA group 28.1 kg, equivalent to daily gains of 931 and 946 g, respectively). Blood serum lipoproteins exhibited few CLA‐induced changes. The greatest effects were observed in triacylglycerols, which were raised in the CLA animals compared with the controls. The ratio of cholesterol‐low‐density lipoprotein to cholesterol‐high‐density lipoprotein rose by 17% as a result of CLA treatment. Serum concentrations of albumin, creatinine, urea and glucose were unchanged. In conclusion, the study showed that supplementation with CLA under isoenergetic feeding conditions with a strongly positive energy balance has no marked effect on total metabolism, although a slightly enhanced deposition of protein was evident.     

Variance of actual inbreeding derived from the number and variance of chromosome segment

The inbreeding coefficient (F) is used as a central parameter inferring a proportion of alleles identical by descent within an individual and by genetic variability within a population. The actual inbreeding coefficient varies around a central value, the inbreeding coefficient. C ockerham and W eir (1983) derived the method for computing the variance of inbreeding while reviewing several other methods. The variance of inbreeding in their report was considered to be of two components: one within population and the other between population of varied pedigrees. If pedigree is fixed, F is easily computed for an individual by the standard method (F alconer 1989). For domestic animals, pedigree information is usually available because it is requisite for a programme of genetic improvement. In this study, the variance of inbreeding coefficient was derived for an individual with a pedigree having a single path to a foundation animal.     

国外私有林的合作化趋势

私有林合作化是国外对私有林进行管理和提高私有林生产能力的一项重要政策措施.文中论述了私有林合作化运动的背景、缘由,以及发达国家和发展中国家为实现私有林合作化所采取的各种措施.