四川省洪雅县3种林分的土壤持水与入渗特性

根据2003年7月到2006年12月的实测数据,对四川洪雅县退耕还林还草工程中的3种林分(光皮桦林、苦竹林和撑绿杂交竹林,农耕地作为对照)进行研究。结果表明,3种典型林分森林土壤的非毛管持水量均大于农地;除撑绿杂交竹竹林外,各林分土壤的有效蓄水容量为农地的1.1~2.1倍;3种林分森林土壤持水量、初渗率和稳渗率的顺序为:苦竹林>光皮桦林>农地对照>撑绿杂交竹林;从土壤持水性能和入渗性能看,苦竹的水文功能好于其他林分土壤,而光皮桦林次之,撑绿杂交竹林差。     

浅析林场木材生产成本超支原因及应采取的措施

本文就林场生产的高投入，低产出，忽视资源配置与效益的关系实行机畜结合，克服林区生产领域生产成本超支的通病提出了切实可行的方法。     

Evaluation of some systems for classifying soil sensitivity to acid deposition in the South African highveld

Abstract. The Skokloster and Stockholm Environmental Institute (SEI) approaches were applied to the assessment of 145 soils of the South African highveld region in terms of sensitivity to acid deposition. The critical load class calculated by variants of these methods was compared with the acid neutralizing capacity (ANC) determined by pH measurement of soil suspended in a dilute acetate buffer solution. This rapid index of ANC correlates well both with ANC determined by an established but more laborious method which involves titration and equilibration of soil with HCl, and with a number of soil properties related to base status. The correlation between Skokloster or SEI critical load classes and ANC was weak. It was concluded that ANC determination would be a preferable basis for classifying these soils in terms of their sensitivity to acid deposition, since the method is direct and integrates the contribution of various soil properties to acid sensitivity instead of requiring the relative contribution to be calculated according to somewhat arbitrary weightings given to broadly defined classes of soil properties.     

Bacterial community structure and microbial activity in different soils amended with biogas residues and cattle slurry

Anaerobic digestion of organic materials generates residues of differing chemical composition compared to undigested animal manures, which may affect the soil microbial ecosystem differently when used as fertilizers. This study investigated the effects of two biogas residues (BR-A and BR-B) and cattle slurry (CS) applied at rates corresponding to 70 kg NH₄⁺-N ha⁻¹ on bacterial community structure and microbial activity in three soils of different texture (a sandy, a clay and an organic clay soil). 16S rRNA genes were targeted in PCR reactions and bacterial community profiles visualized using terminal restriction fragment length polymorphism. General microbial activity was measured as basal respiration (B-resp), substrate-induced respiration (SIR), specific growth rate (μ_SIR), metabolic quotient (qCO₂) and nitrogen mineralization capacity (NMC). Non-metric multidimensional scaling analysis visualized shifts in bacterial community structure related to microbial functions. There were significant differences in bacterial community structure after 120 days of incubation (+20 °C at 70% of WHC) between non-amended (control) and amended soils, especially in the sandy soil, where CS caused a more pronounced shift than biogas residues. Terminal-restriction fragment (TRF) 307, the predominant peak in CS-amended sandy soil, was identified as possibly Bacillus or Streptococcus. TRF 226, the dominant peak in organic soil amended with BR-B, was classified as Rhodopseudomonas. B-resp significantly increased and SIR decreased in all amendments to organic soil compared with the control, potentially indicating decreased efficiency of heterotrophic microorganisms to convert organic carbon into microbial biomass. This was also reflected in an elevated qCO₂ in the organic soil. The μ_SIR level was higher in the sandy soil amended with BR-A than with BR-B or CS, indicating a shift toward species capable of rapidly utilizing glucose. NMC was significantly elevated in the clay and organic soils amended with BR-A and BR-B and in the sandy soil amended with BR-B and CS. Thus, biogas residues and cattle slurry had different effects on the bacterial community structure and microbial activity in the three soils. However, the effects of biogas residues on microbial activities were comparable in magnitude to those of cattle slurry and the bacterial community structure was less affected. Therefore, we do not see any reason not to recommend using biogas residues as fertilizers based on the results presented.     

前推土后挖掘(凿岩)装置的总体设计

介绍了四轮驱动拖拉机的前推土后挖掘(凿岩)装置的总体设计过程,它的开发和研制,拓展了拖拉机的使用性能,弥补了产品季节性较强的不足。     

地基极限承载力的无网格分析

在无网格伽辽金法的基础上,利用应力应变增量形式表征了基于Drucker-Prager屈服准则的土体弹塑性本构关系;在小变形假设的前提下,实现了基于增量本构关系的弹塑性分析的无网格伽辽金法;采用罚参数修正了能量变分方程式,方便地实现了无网格伽辽金法的本质边界条件;并采用Newton-Raphson增量迭代法计算地基土体的极限荷载,其分析结果与静载试验结果吻合较好,验证了本文方法的合理性,进一步拓展了无网格伽辽金法的应用范围.同时与有限元计算结果作了对比研究,体现了无网格法的优越性.     

我国畜牧业发展战略刍议

我国正处在人增地减、经济持续增长、改革开放超长发展的形势下，畜牧业正面临着需求持续增长、限制因素增加、生产经营系统不断变革的压力之下。畜牧业的持续稳定发展，必须解决：正确认识畜牧业在国民经济中的地位和作用；畜牧业产业化道路；科学技术是畜牧业发展的动力；保持生态平衡使畜牧业可持续发展等战略问题。     

前置导叶对畜禽舍轴流风机性能的影响

畜禽养殖过滤除臭装置对传统轴流风机负压抽吸能力提出了更高的要求。为提高传统轴流风机的气动性能，扩大其有效工作区间，该研究以550型农用轴流风机为对象，结合试验和数值模拟研究了前置导叶对轴流风机性能的影响。通过单因素和响应面分析方法，对前置导叶的导叶安装角（α）、轴向间距（L）、导叶个数（n）对风机性能和流场的影响进行研究，分析各因素对风机性能的影响，求解出最佳参数组合。通过3D打印制作前置导叶并进行样机试验。结果表明，增设前置导叶后，风机内部区域涡流得到削弱，降低了流动损失，静压效率提高，流动剧烈程度降低，流场更稳定，叶片静压差增大，风机叶片的做功能力增强，与传统结构相比，增设前置导叶后风机通风量和能效比均明显提升，通风量提升幅度在5.7%～10.39%，能效比提升幅度在6.62%～10.89%；在静压50 Pa下，通风量提升6.76%，能效比提升7.75%。研究结果证明了增设前置导叶提升轴流风机负压抽吸能力的可行性。     

广华枝的取食量及其防治研究

本文研究了广华枝ＳｉｎｏｐｈａｓｍａｌａｒｇｕｍＣｈｅｎｅｔＣｈｅｎ的食叶量。其一生食叶量为２０．８０２ｇ，其中１～４龄低龄若虫期的食量占其一生食量的３．１３％，５～６（７）龄老龄若虫期的食量占２１．９５％，成虫期的食量占７４．９２％，老龄若虫期和成虫期是主要的危害期，占其一生食量的９６．８７％；并建立了个体食叶量模型、个体日均食量模型及其活动量指数增长模型，分别为Ｘ１＝０．０３９４ｅ０．５９７９Ｘ０，校正Ｒ２＊＊＝０．８９３１；Ｘ２＝２６．５１７６ｅ０．２２３３Ｘ０，校正Ｒ２＊＊＝０．７６７３；Ｘ３＝１．３０９３ｅ０．５００１Ｘ０，校正Ｒ２＊＊０．９４４０，复相关系数平方显著或极显著；胸径为８～１２ｃｍ的寄主，其防治指标为９３．１头，并提出了防治意见。     

Effects of different land use types on infiltration capacity in a catchment in the highlands of Ethiopia

Infiltration capacity is an important variable for understanding and predicting a range of soil processes. This study investigated for different slope positions the effects of forest conversion to cultivation and grazing on soil infiltration capacity. Infiltration capacity was measured in the field in each land use type using a double‐ring infiltrometer. A total of 108 soil samples (3 slope positions × 3 land use types × 4 soil profiles × 3 soil depths) were collected to determine the variables that affect infiltration capacity viz. particle size distribution, organic carbon content, dry bulk density and soil moisture content. The results showed that in the cultivated and grazed land compared with forest, infiltration capacity and soil moisture content were 70 and 45% smaller respectively, and dry bulk density was 13–20% larger. Changes in soil structure caused by surface soil compaction because of tillage and animal trampling coupled with a smaller soil organic carbon content, are likely to be the principal factors causing the decline in infiltration capacity and soil moisture content after conversion of forest to cultivation and grazing.