华南土壤的粘土矿物组成

华南热带区及亚热带区的成土作用,直到现在还有许多没有解决的问题,例如,现代生物气候条件下土壤的发育方向;红壤和黄壤的关系及其基本特性的差异;红壤中校普遍存在的鐵子、鐵盤及网状斑纹的成因等,都有不少的争论^[1-8]。     

不同土壤水分对赤松光合作用与水分利用效率的影响研究

在不同土壤水分条件下研究了赤松光合特征及其水分利用效率的变化。结果表明,不同土壤水分处理对赤松幼苗净光合速率、气孔导度、蒸腾速率、水分利用效率等生理指标及其日变化均产生明显影响;中度水分胁迫时赤松幼苗的光合午休比对照提前1h且午休时间长,其净光合速率和气孔导度的下降平行进行,而且,日平均水分利用效率的下降幅度比日平均净光合速率的下降幅度小。     

Aluminium release in relation to the determination of cation exchange capacity of some podzolized New Zealand soils

In upper mineral horizons, CEC by compulsive and isotopic exchange methods, using Ba²⁺ as the saturating cation, gave higher values than the effective CEC at natural soil pH, and much higher values than CEC determined with m NH₄OAc at pH 7. Cumulative Al release during leaching was considerably higher using Mg²⁺ and Ba²⁺ chlorides than K⁺ and NH₄⁺ chlorides, and gave a different shape extraction curve. Basal spacing of the dominant dioctahedral vermiculite in the soil clays contracted from 14.5Å to 10.0–10.9 Å when saturated with NH₄⁺ and K⁺, restricting release of interlayer Al. Lower horizons, containing a large proportion of Al-chlorite in the clay fraction, which did not contract with any of the cations, showed more normal exchange behaviour. On leaching, Al release was slightly greater with K⁺ and NH₄⁺, than with Mg²⁺ and Ba²⁺, chlorides. The implication of the results for CEC measurements is discussed.     

土壤NO_x气体释放研究进展

营养元素的迁移转化是生态学及环境科学研究领域的一个重要课题,土壤微生物活动产生的NOx气体作为大气中NOx的重要排放源之一,日益受到人们的关注。NOx在大气中具有很强的化学活性,通过参与大气中光化学反应而影响到其它温室气体的浓度,且在对流层O3和OH自由基的光化学反应中起着决定性作用,同时也是酸沉降中HNO3的生成源,在平流层NOx是消耗臭氧层的痕量气体之一。本文综合分析了土壤NOx产生及排放机理;影响土壤NOx排放的主要因素;土壤NOx气体排放通量的测定及其模型估算方法。并在此基础上,提出今后应把土壤微生物系统以及土壤硝化、反硝化作用机理作为以后的研究重点,运用同位素技术和各种模型手段进行较大范围的时空尺度上的连续观测研究。     

Relationship between adipose maturity and fatty acid composition in various adipose tissues of Japanese Black,Holstein and Crossbred (F1) steers

The amount of monounsaturated fatty acid (MUFA) is intimately related to adipose softness, melting point (MP) and flavor in beef. Stearoyl‐CoA desaturase (SCD) is a main gene involved in MUFA synthesis. Mature adipose tends to be highly saturated, whereas immature or maturing adipose is highly unsaturated when chronologically based, so the degree of non‐saturation can be an index of adipose maturity. In this study, three different adipose tissues (coelomic (CL), perirenal (PR), and subcutaneous (SC)) from three beef breeds with differing slaughter ages (Japanese Black (29.5 months), Holstein (20.1 month), and F1 crossbreed (25.6 months)) were examined to: (i) determine adipose maturity level as indexed by MUFA %; and (ii) determine SCD and other lipogenic gene messenger RNA (mRNA) expression levels in relation to unsaturated fatty acid content. Fatty acid composition was significantly different between adipose tissues (P < 0.05). MUFA amount was high in the following order: SC > CL > PR. This pattern corresponded to SCD mRNA expression profile showing higher expression in SC than CL and PR. However, Japanese black cattle are an exception with CL adipose containing similar UFA % as SC adipose, yet having the lowest SCD mRNA expression level among all adipose tissues tested. Therefore, SCD mRNA expression and MUFA % appear to be directly related; however, differences in SCD mRNA expression among three adipose tissues may reflect differences in the fat development characteristics affected by chronological age of the cattle breeds.     

Rumen microbial response in production of CLA and methane to safflower oil in association with fish oil or/and fumarate

Supplementation effect of fish oil and/or fumarate on production of conjugated linoleic acid (CLA) and methane by rumen microbes was examined when incubated with safflower oil. One hundred and twenty milligrams of safflower oil (SO), safflower oil with 24 mg fish oil (SOFO), safflower oil with 24 mmol/L fumarate (SOFA), or safflower oil with 24 mg fish oil and 24 mmol/L fumarate (SOFOFA) were added to the 90 mL culture solution. The culture solution was also made without any supplements (control). The SOFA and SOFOFA increased pH and propionate (C3) compared to other treatments from 3 h incubation time. An accumulated amount of total methane (CH₄) for 12 h incubation was decreased by all the supplements compared to control. The concentrations of c9,t11CLA for all the incubation times were increased in the treatments of SOFO, SOFA and SOFOFA compared to SO. The highest concentration of c9,t11CLA was observed from SOFOFA among all the treatments at all incubation times. Overall data indicate that supplementation of combined fumarate and/or fish oil when incubated with safflower oil could depress CH₄ generation and increase production of C₃ and CLA under the condition of current in vitro study.     

Effects of corn dried distiller's grains with solubles and enzyme premix supplements on growth performance,carcass characteristics and meat quality parameters in finishing pigs

The objective of the present study was to investigate the effects of corn dried distiller's grains with solubles (DDGS) and enzyme premix (mannanase + phytase) supplementation on the growth performance, carcass and meat quality parameters in finishing pigs. Sixty hybrid pigs (L × LW × D) with initial weight of 63.92 ± 1.50 kg were used in a 3 × 2 factorial design with main effects of DDGS levels (0, 10 and 20%) and enzyme premix levels (0% vs. 0.14%). Average daily gain (ADG, P < 0.01) and average daily feed intake (ADFI, P < 0.05) were decreased due to an increased level of DDGS additive while the feed conversion ratio was improved (P < 0.05) by adding enzyme premix. The diet cost/gain (won/kg) was saved (P < 0.01) due to an increased level of DDGS additive. There were no significant differences in carcass characteristics and meat quality parameters of Longissimus dorsi muscle by DDGS level and enzyme premix. Palmitoleic acid, oleic acid and monounsaturated fatty acid (MUFA) decreased (P < 0.05) according to DDGS level. The results indicate that DDGS may be used in feeds for finishing pig as a replacement of corn and soybean meal without affecting their carcass characteristics and meat quality.     

Physicochemical methods for pharmacokinetic and residue analysis of chloramphenicol and degradation products in dairy cows

The disposition of chloramphenicol after intramammary and intravenous administration was followed through determinations of chloramphenicol in blood and milk by means of high-performance differential pulse polarography. The concentration-time curves obtained reflected the different modes of administration, and allowed calculation of some pharmacokinetic parameters. The results of the polarographic determination in blood agreed fairly well with those of the microbiological assay in serum. Several body fluids and tissues of the cows were examined for residues of chloramphenicol and degradation products, both by the microbiological method and by high-performance liquid chromatography with ultraviolet detection. In urine, chloramphenicol and chloramphenicol glucuronide were found; in the other fluids and tissues only now and then a trace of chloramphenicol or a degradation product was detected. From these results it appears that chloramphenicol and degradation products are eliminated rapidly and completely after intravenous or intrammary application. No accumulation of degradation products occurred.     

Techniques for Reconstructing Circular Skin Defects in Dogs

The development of dog-ears of redundant skin or removal of large areas of additional skin are problems often encountered when closing circular skin defects. Defects 3 cm in diameter were created along the backs of dogs. Eight techniques of reconstruction were evaluated by measuring the area of additional skin removed and length of final suture line and by counting the number of dog-ears produced. The eight techniques were linear, fusiform, double S, three point, four point, pin wheel, bow tie, and combined V closures. Based on the results of this study, the linear, combined V, and bow tie techniques provide the best closure. In general, the linear technique should be used when skin edges can be apposed without the formation of dog-ears (e.g., smaller defects). When skin edge apposition results in dog-ear formation and when there is limited skin for reconstruction surrounding the defect, the combined V technique should be used. When larger dog-ears form as the skin edges are apposed and when there is an abundance of skin surrounding the defect, the bow tie technique could be considered for closure. One-half of the bow tie technique can be used to approximate wound edges where one edge is long and curved.     

Global scale forest function and distribution

A model is described for predicting the dynamic changes in theproportion of tree, shrub and grass life forms at the globalscale. This model is driven by the impacts of climate, soilsand CO₂ on global vegetation leaf area index and net primaryproductivity. The life-form model has been used to explore theinfluences of global warming and continued CO₂ increase on treecover This reflects a realization from other modelling workthat forested vegetation, at the global scale, exerts significantinfluences on climate, and so it is important to assess thepotential for this feedback under climatic change. An increase in CO₂ from 350 to 560 p.p.m. is modelled to haveonly a small impact on tree cover, under current climate. Aregionally-consistent and global increase in temperature ofc.2^{ring}C and a 10 per cent increase in precipitation, butwith no increase in CO₂, indicates a significant potential fortrees to spread into current shrub tundra, over a period of50 years This could lead to regional warming, through changesin winter albedo. The effect of the CO₂ increase is most noticeablein interaction with increases in temperature (2^{ring}C) andprecipitation (10 per cent). In this case the life-form modelprojects further increases in tree cover, particularly in areaswith seasonally low periods of precipitation.