猪流感的发生和防制对策

猪流感是由猪流感病毒引起的一种急性、热性、高度接触性传染病 ,当天气持续高温、闷热时 ,该病易呈地方性暴发流行。目前无特效药 ,一旦发生 ,极难控制 ,病程拖长 ,给养猪业带来巨大经济损失 ,必须引起高度重视。１病原猪流感病毒属于正粘病毒属。主要存在于病猪的鼻液、气管、支气管渗出液以及肺、肺门淋巴结等处。该病毒对干燥和低温有较强抵抗力 ,但对常用消毒剂较敏感 ,对碘制剂特别敏感。２流行病学不同年龄、品种、性别的猪都易感。病猪和康复猪是主要传染源 ,后者可带毒１．５～３个月。主要通过呼吸道飞沫传染 ,被污染的饲料和饮水…     

Alpine meadow restorations by non-dominant species increased soil nitrogen transformation rates but decreased their sensitivity to warming

Purpose

Alpine meadow soils are large carbon (C) and nitrogen (N) pools correlated significantly with global C and N cycling. Soil N transformations, including nitrification and N mineralization, are key processes controlling N availability. Alpine meadow degradations are common worldwide, and vegetation restorations have been widely implemented. However, grass species used for restorations may alter soil N transformations or their response to warming and N deposition due to divergent plant traits and their different effects on soil characteristic. To understand the effects of meadow restorations by non-historically dominant species on N transformations, we measured N transformation rates in restored soils and control soils under the context of warming and N deposition.

Materials and methods

We collected soils from plots restored by dominant (Miscanthus floridulus) and non-dominant species (including Carex chinensis and Fimbristylis dichotoma) and non-restored plots in alpine meadows of Wugong Mountain, China. We measured nitrification and N mineralization rates when soils were incubated at different temperature (15 or 25 °C) and N additions (control vs. 4 g m^?2) to examine their responses to restoration species, warming, and N.

Results and discussion

Vegetation restored soils differed substantially from non-restored bare soils. Total N, total organic C, pH, and dissolved organic C contributed the most to the separation. Restoration altered soil N transformations substantially, even though the effects varied among restoration species. Specifically, non-historically dominant species accelerated N transformations, while the originally dominant species decreased N transformations. In addition, sensitivity of nitrification to warming in restored soils was decreased by restorations. Soils restored by originally dominant species were higher in sensitivity of N transformations to warming than those restored by the other two species. Warming increased nitrification rates by 45.5 and 17.4 % in bare soils and restored soils, respectively. Meanwhile, N mineralization rates were increased by 52.8 and 21.9 %, respectively.

Conclusions

Vegetation restoration of the degraded meadows impacted N transformations and their sensitivity to warming. The effects varied with identity of the restoration species, suggesting that grass species should be considered in future restorations of degraded meadows in terms of their divergent effects on N transformations and sensitivity to warming.

     

Effects of mixing biochar on soil N2O,CO2, and CH4 emissions after prescribed fire in alpine meadows of Wugong Mountain,China

Journal of Soils and Sediments - Prescribed fires or wildfires are common in natural ecosystems. Biochar input during fires can impact soil greenhouse gas (GHG) emissions, including methane (CH4),...     

桃树高产栽培中产量构成因素的动态变化

以“白花”和“湖景蜜露”两个桃品种为试材,调查分析了桃树高产栽培中产量构成的诸因素及其动态变化。结果表明,每亩相对有效结果枝的数量是桃树产量构成中最根本的因素,亩产1,500—2,500公斤的田块,枝量应保持在18,000—22,000根左右,其中长壮枝应占20—25％;着果率同样是产量构成中的重要因素,高产田两品种的不着果枝率分别低于25％和10％,平均单枝着果系数则分别达到1.0和1.5以上;单果重对产量的影响相对较小。三项因素均随树龄、栽植密度和管理优劣等条件而变化,变异范围以每亩枝量为最大,着果率次之,单果重最小。我们认为,评价桃树单产的高低应根据多年的平均产量。     

响应面法优化制备眼树莲总三萜软膏

以眼树莲总三萜为原料,采用Box-Behnken响应面法优化制备眼树莲总三萜软膏,通过考察其理化性质、稳定性以及软膏中总三萜含量确定最优软膏基质的处方.在硬脂酸、丙二醇、月桂氮卓酮的用量及乳化温度单因素实验结果基础上,采用基质的外观形状、涂展性、稠度、离心稳定性进行综合性评分,利用响应面法优化,选取最优的制备工艺.结果表明,最优软膏基质制备处方为乳化温度70℃,硬脂酸26％,丙二醇7％,月桂氮卓酮3％.软膏的综合性评分可达到最优值,为97分,并且分析测得软膏中相应的总三萜含量较高.说明响应面法优化后的眼树莲总三萜软膏制备方法可行性高,为开发制备眼树莲软膏制剂奠定基础.