Acclimation abilities of three tropical rainforest seedlings to an increase in light intensity

Current practices in many nurseries involve the germination of tropical rainforest seedlings in shaded conditions and transferral, at a later date, to environments with greater light intensities. Determination of the ability of these seedlings to acclimate to increased light intensities will allow seedling stock to be processed with maximum efficiency within the nursery. The acclimation abilities of three species, Agyrodendron actinophyllum, Cardwellia sublimis, and Flindersia brayleyana, commonly found in north Queensland's rainforests were investigated in this study. These particular species are highly valued for their cabinet timber qualities and are being reared in nurseries for use in reforestation trials and programs in north Queensland. Seedlings were initially raised in greenhouse conditions under two layers of shade cloth (16% of full sunlight) and then transferred into full sunlight at three different ages (3 weeks, 10 weeks, 14 weeks). Upon transfer, organ ratios and the direction of dry matter distribution was determined for each species and age group. Approximately 3 months after the seedlings were transferred, the acclimation ability of each species and age group was then determined. Dry matter distribution was found to change with age, irrespective of light environment. Individuals within a species with larger root systems and thicker or more dense leaves had a greater acclimation ability than those with smaller root systems and thinner or less dense leaves. Furthermore, individuals within a species whose dry matter distribution upon transfer was directed towards developing a large root system, and a small photosynthetic area and mass, had a greater acclimation ability than those whose dry matter distribution was directed away from such morphologies. Awareness of these relationships allows a better understanding of seedling response to gap formation in natural forests, and also allows plant nursery operators to make a more informed decision about when to move seedlings to environments with a higher light intensity.     

2000-2009年新疆雷电灾情分析

对2000-2009年气象部门收集的雷灾资料进行统计分析,研究新疆雷电灾情的时空分布特征、受损财物与受伤害人员情况等。资料包括97次雷灾事件,其中30次雷灾造成了31人死亡,15人受伤。新疆雷灾发生在3~9月,夏季占78%以上,6月最高。造成人员伤亡和财产损失的雷灾主要发生在11:00~24:00时,17:00~18:00时为峰值。雷灾致人员伤亡的雷击地点,发生在户外的最多。     

玉米、小麦、水稻秸秆自然发酵的生化变化

测定玉米、小麦、水稻干秸秆在自然发酵中的生化变化.结果表明:玉米秸秆气味香甜,pH下降迅速并保持在4.2以下,挥发性发酵产物种类有13种,主要为乙醇、乙酸、乳酸及甘油等利于提高饲料品质的物质;而小麦和水稻秸秆质地生硬,生料气味,pH下降困难,挥发性发酵产物多达20种,其中乳酸和乙酸较少,而产生丁酸等影响发酵品质的物质较多;发酵物中可溶性糖含量的变化在一定程度上反映其优劣;当发酵初期可溶性糖较多时,pH下降迅速,后期可溶性糖含量平稳;而当初期可溶性糖含量较低时,pH下降缓慢,后期可溶性糖含量则一直下降.     

The effect of extended grazing time and supplementary forage on the dry matter intake and foraging behaviour of cattle kept under traditional African grazing systems

An experiment was carried out at Alemaya University in Ethiopia to investigate the effect of night kraaling on the dry matter intake (DMI), live weight gain (LWG) and foraging behaviour of Ogaden cattle. Three groups of four animals were given either 7 h access to pasture per day, simulating traditional grazing (TG) practice; extended grazing (EG) access for 11 h per day; or traditional grazing access plus a nocturnal forage supplement (TF). Live weight gain, DMI and foraging behaviour were measured during the late dry season (EP1) and the wet season (EP2). None of the treatments had any significant effect on either DMI or LWG during EP1 or EP2. Extending pasture access time from 7 h to 11 h did not significantly increase the amount time spent grazing, but grazing intensity was significantly (p < 0.05) reduced during the non-common grazing hours. Step rate was significantly lower (p < 0.01) during EP2 than during EP1 and bites per step were significantly higher (p < 0.001) during EP2 than EP1, indicating that animals had to travel a shorter distance before selecting material to eat during the wet season (EP2). Providing supplementary forage (TF) had no significant effect on any measured parameter. In this study neither of the two low-cost methods (EG and TF) of improving access to forage had any beneficial effect on cattle productivity. It is concluded that, under the prevailing conditions, the traditional grazing practices of this part of Ethiopia do provide sufficient pasture access time to achieve daily voluntary food intake.     

西汉时期西北地区农业开发的自然灾害背景

西汉时期是中国历史上西北开发的关键时期,尤其是汉武帝一朝,西北开发功勋卓著。在西汉时期大规模开发西北的决策过程中,政治、经济、军事等方面的因素发挥了重要的影响作用,但是自然灾害对西北开发的影响作用也不容忽视。西汉时期严峻的灾害形势对关中和山东农区造成了重大破坏作用,国家粮食安全岌岌可危。出于化解灾害风险的现实需要,西汉王朝不得不以战争的手段解决北部匈奴问题,依靠农业生产扩大西北地区耕地面积,移民实边。经过两百年的刻苦经营,西汉时期终于奠定了西北农业生产的基本格局,关中、河套、河西、河湟主要农业生产区全面形成,中国传统农业阶段第一个人口高峰出现并维持了一千多年之久。     

涝害对甜叶菊光合及单株干叶产量的影响

利用温室盆栽法研究不同持续时间涝害对甜叶菊种质材料IS-1、QF-1、青甜杂4、JD-1、AL-4光合作用及干叶产量的影响。结果表明：随着涝害时间的持续,5份甜叶菊种质材料的叶绿素SPAD值、净光合速率（Pn）、气孔导度（Gs）、胞间CO2浓度（Ci）、蒸腾速率（Tr）及单株干叶产量均表现出不同程度的变化。短时间涝害处理（Ta：5d）对SPAD值、Pn、Gs、Ci、Tr及单株干叶产量影响均不显著;但随着渍水时间的持续叶片SPAD值、Pn表现出下降趋势：在Tb（涝害处理10d）中IS-1、QF-1、青甜杂4、JD-1、AL-4的SPAD值较正常水分处理分别下降21.29%、34.57%、27.84%、23.01%、17.59%,QF-1下降最快,AL-4下降最慢;Pn较正常水分处理分别下降65.88%、78.51%、74.44%、71.68%、59.58%,QF-1下降最快,AL-4下降最慢;Gs与Tr变化趋势与Pn相似,而Ci与Pn变化趋势相反;随着涝害持续时间的持续,甜叶菊单株干叶产量出现下降趋势,不同材料相同时间涝害胁迫单株干叶产量下降幅度不同,表明不同材料对涝害的耐受力不同。     

黑木耳简单快速组织分离新法

利用酒精、镊子对黑木耳耳片进行组织分离,方法方便、快捷,分离成功率100%。     

新疆亚洲玉米螟暴发成灾驱动机制分析及其治理对策

亚洲玉米螟Ostrinia furnacalis (Guenée)为新疆玉米生产中的主要害虫, 2010年以来呈整体暴发态势, 并造成了极为严重的产量损失, 已成为制约当前新疆玉米高产稳产和粮食产能提升最重要的害虫, 然而有关其暴发成灾的驱动机制尚不清楚。为此, 本文通过分别概述近年来新疆气候、作物种植结构、栽培耕作措施以及亚洲玉米螟田间发生世代的变化情况, 综合分析了上述变化对亚洲玉米螟越冬幼虫存活、个体生长发育、取食偏好和种群增殖扩张等方面造成的具体影响。在此基础上, 结合已有大量研究成果, 系统解析了新疆绿洲生态区亚洲玉米螟种群暴发成灾的驱动机制。此外, 本文还介绍了新疆植保科技工作者在亚洲玉米螟综合治理技术研究与应用方面取得的相关成果, 简述了田间治理采取的措施和取得的防治成效, 最终为亚洲玉米螟的持续有效治理提供一定参考。     

蔬菜一年三熟高效种植模式分析

绿色有机旱作农业是山西农业的传统特色。长治市属于典型的雨养农业、旱作农业区,长治市潞州区抓住绿色有机旱作农业的发展机遇,积极探索适宜该地区、具有区域特色的绿色有机旱作农业技术模式。该技术模式是通过合理的茬口安排,实行一年多茬栽培,“春白菜-甘蓝-秋白菜”是典型的一年三熟种植模式,通过对这种三收高效种植模式的种植方式、田间管理、病虫害防治等方面的分析,提出了实现高效种植的基本措施;按照绿色有机旱作标准制定种植方案,实现提质增效,通过提高复种指数,增加经济效益,为干旱地区绿色有机旱作农业发展提供技术参考。     

国内外蝗虫研究发展动向初探

蝗虫是广泛分布于世界各地尤其是中低纬度地区的一种昆虫，其分布广泛性和危害严重性使之成为多门学科重要的研究对象之一。本文比较系统地总结了当前国内外蝗虫研究状况和近新进展，初步探讨了蝗虫研究中的若干新领域与新技术，对开展相关研究有一定的借鉴意义。