氮输入对沼泽湿地小叶章枯落物分解过程中酶活性的影响

以三江平原沼泽湿地典型湿地植物小叶章枯落物(Calamagrostis angustifolia)为研究对象,采用分解袋法研究了不同外源氮输入(N1、N2分别为6、12g·m-·2a-1)对小叶章枯落物分解过程酶活性的影响,并设置对照区(N0,0g·m-·2a-1)进行比较.研究结果表明,在枯落物最初分解的2个月里,氮输入会抑制蔗糖酶活性,尤其是低氮输入(N1)抑制作用显著(p<0.05),2个月后,氮输入显著促进了该酶活性(p<0.05);;氮输入除在160d时抑制了淀粉酶活性,其它时期均促进了该酶活性,且高氮输入(N2)促进作用显著;;氮输入提高了枯落物分解前2个月的脲酶活性,而在分解后期,低氮输入抑制脲酶活性,高氮输入则主要表现为促进脲酶活性;;低氮输入提高了小叶章枯落物分解前2个月的酸性磷酸酶活性,随后表现为抑制,高氮输入则只在分解后期(160d)抑制酸性磷酸酶活性,其它时期均表现为促进.总体而言,氮输入促进了蔗糖酶、淀粉酶活性,而对于脲酶及酸性磷酸酶活性来说,低氮输入抑制了酶活性,而高氮输入则表现为促进酶活性.     

Some bacteriological aspects of poultry litter used as feed supplement in rabbit diets

An investigation was carried out to determine the microbial load in poultry litter used as feed supplement in rabbit diets. Before heat treatment by deep stacking the poultry litter, samples of the litter were collected to assay for microbial load at the Microbiology Laboratory of the Rivers State University of Science and Technology, Port Harcourt, Nigeria. Results obtained showed that before heat-treating the poultry litter, Escherichia coli, Salmonella, Mycobacterium, Clostridium and Staphylococcus were isolated at 41, 37, 37, 41 and 42°C, respectively. The results obtained also indicate that no pathogen was isolated after heat treatment of between 40 and 55°C for 21 days. This study justifies the suitability of using poultry litter as a feed supplement.     

Deep stacking poultry litter as feed ingredient in livestock production

The compelling need to harness the potentials of the numerous agro-industrial by-products and the so-called “wastes” as part replacement for the more expensive conventional feed ingredients have been seriously expressed. This need has arisen mainly from the increasing demand and supply deficit of conventional feed resources with a concomitant sharp rise in their cost prices. The net effect of increased unit cost of the conventional feed resources is increased cost of the compounded rations, which by extension gives rise to increased cost of meat and animal products. It then becomes highly imperative that other sources for rapid livestock output to meet the growing human demands for animal protein foods are sourced. Such other sources should be cheap and nutritionally adequate for feeding animals with the aim of lowering the cost of producing meat. One of such measure is the recycling of poultry litter as part replacement for soya bean in livestock nutrition. Poultry litter is the by-product of poultry production, which should be managed in an environmentally friendly manner. As observed in this study, poultry litter contains 20% crude protein, 621.41 ME kcal kg^?1, and substantial amounts of minerals that could be exploited in feeding livestock. This study has explored the possibility of including poultry litter in diets in view of its contents.     

四川盆地亚热带常绿阔叶林土壤动物对几种典型凋落物分解的影响

亚热带常绿阔叶林土壤动物对植物生长不同关键时期凋落物分解的贡献可能具有显著差异,但一直缺乏必要关注。以四川盆地亚热带常绿阔叶林典型人工林树种马尾松(Pinus massoniana)和柳杉(Cryptomeria fortunei),次生林树种香樟(Cinnamomum camphora)和麻栎(Quercus acutissima)凋落物为研究对象,采用凋落物分解袋试验,根据植物叶片物候规律在非生长季节(秋末落叶期、萌动期和展叶期)和生长季节(叶片成熟期、盛叶期和叶衰期)不同关键时期动态研究土壤动物对凋落物失重率的影响。土壤动物对4种典型物种凋落物分解均表现出明显贡献,其作用的凋落物失重率分别为：17.78%(麻栎)>14.23%(柳杉)>9.61%(香樟)>8.21%(马尾松)。相对于其他时期,四个树种的土壤动物贡献率均在秋末落叶期最小,除马尾松在叶衰期土壤动物贡献率最大以外,其余3个物种均在盛叶期土壤动物的贡献率最大,且土壤动物对阔叶分解的贡献率大于针叶。相关分析表明,除温度显著影响各关键时期土壤动物对凋落物的贡献外,整个第一年土壤动物作用的凋落物失重率及贡献率与纤维素含量和C/N显著相关,但在非生长季节主要与N含量、C/N和木质素/纤维素密切相关,而生长季节主要相关于木质素/N。这些结果为深入理解亚热带常绿阔叶林物质循环及其与植物生长过程的关系提供了一定的基础数据。     

3个树种凋落叶水浸提液对三叶鬼针草生长及抗性生理的影响

入侵植物三叶鬼针草(Bidens pilosa)对农业生产、生物多样性和生态系统安全有极大的威胁,利用植物间的化感作用抑制有害植物生长或开发植物源除草剂,是减少化学除草剂对环境负面影响的良好措施。常见树种巨桉(Eucalyptus grandis)、香樟(Cinnamomum camphora)和核桃(Juglans regia)叶片所含次生代谢物质对植物和微生物具有较强的化感潜力,可能会在入侵草本植物的防治上起到重要作用。选用巨桉、香樟和核桃凋落叶,分别制成不同浓度水浸提液,结合培养皿萌发试验和盆栽试验,通过测定三叶鬼针草发芽率、发芽速度、幼苗植株鲜质量、抗氧化酶活性以及渗透调节物质含量,综合评价3个树种凋落叶浸提液的作用效果。巨桉和香樟凋落叶浸提液可显著抑制三叶鬼针草的发芽。三叶鬼针草地上部分鲜质量明显受到高浓度巨桉凋落叶浸提液的抑制,而香樟和核桃凋落叶浸提液的抑制作用微弱;3个树种凋落叶浸提液对三叶鬼针草过氧化物酶(POD)和超氧化物歧化酶(SOD)活性具有促进作用,而对其过氧化氢酶(CAT)活性具有抑制作用;巨桉凋落叶浸提液处理三叶鬼针草抗氧化酶系统表现出"钝化"响应,而其体内丙二醛(MDA)含量则显著增加;对巨桉和香樟凋落叶浸提液而言,三叶鬼针草可溶性蛋白和可溶性糖含量均随浸提液剂量的增加而升高,而在核桃凋落叶浸提液处理下则表现出低促高抑的效应。总体来看,3个树种凋落叶含有干扰三叶鬼针草生长的物质,但效应因树种和浸提液浓度而异。相比较而言,巨桉凋落叶浸提液的综合抑制作用最强,香樟次之,核桃最弱。     

Litter decomposition and nitrogen mineralization from an annual to a monthly model

The forest litter decomposition model (FLDM) described in this paper provides an important basis for assessing the impacts of forest management on seasonal stream water quality and export of dissolved organic carbon (DOC). By definition, models with annual time steps are unable to capture seasonal, within-year variation. In order to simulate seasonal variation in litter decomposition and DOC production and export, we have modified an existing annual FLDM to account for monthly dynamics of decomposition and residual mass in experimental litterbags placed in 21 different forests across Canada.The original annual FLDM was formulated with three main litter pools (fast, slow, and very slow decomposing litter) to address the fact that forest litter is naturally composed of a mixture of organic compounds that decompose at different rates. The annual FLDM was shown to provide better simulations than more complex models like CENTURY and SOMM.The revised monthly model retains the original structure of the annual FLDM, but separates litter decomposition from nitrogen (N) mineralization. In the model, monthly soil temperature, soil moisture, and mean January soil temperature are shown to be the most important controlling variables of within-year variation in decomposition. Use of the three variables in a process-based definition of litter decomposition is a significant departure from the empirical definition in the annual model. The revised model is shown to give similar calculations of residual mass and N concentration as the annual model (r² = 0.91, 0.78), despite producing very different timeseries of decomposition over six years. It is shown from a modelling perspective that (i) forest litter decomposition is independent of N mineralization, whereas N mineralization is dependent on litter decomposition, and (ii) mean January soil temperature defines litter decomposition in the summer because of winter-temperatures’ role in modifying forest-floor microorganism community composition and functioning in the following summer.     

Utilization Characteristics and Importance of Woody Biomass Resources on the Rural-Urban Fringe in Botswana

This article examines the utilization characteristics and importance of woody biomass resources in the rural-urban fringe zones of Botswana. In the literature for Africa, attention has been given to the availability and utilization of biomass in either urban or rural environments, but the rural-urban fringe has been neglected. Within southern Africa, this neglect is not justified; the rural-urban fringe, not getting the full benefits available in urban environments in Botswana, has developed problems in woody biomass availability and utilization that require close attention. In this article, socioeconomic data on the importance of woody biomass in the Batlokwa Tribal Territory, on the rural-urban fringe of Gaborone, Botswana, were collected together with ecologic data that reveal the utilization characteristics and potential for regrowth of woody biomass. The analysis of these results show that local woody biomass is very important in the daily lives of communities in the rural-urban fringe zones and that there is a high level of harvesting. However, there is no effort in planning land use in the tribal territory to either conserve this resource or provide alternatives to its utilization. The future of woody biomass resources in Botswana’s rural-urban fringe is uncertain. The investigators recommend that a comprehensive policy for the development of the rural-urban fringe consider the importance of this resource. The neglect of this resource will have far-reaching implications on the livelihoods of residents as well as the environment in this zone.