长江近口段沿岸刀鲚生物量的时间格局

为了解长江刀鲚Coilia nasus资源的变动状况,探讨沿岸水域对刀鲚资源的保育作用,于2002~2013年间用定制张网对长江靖江段沿岸鱼类作了每月2~3个样本的采集。分析结果显示,12a采集的369份样品中,刀鲚的出现频率达94.6%,分别占总渔获数量和重量的5.18%和5.46%。刀鲚平均CPUEN和CPUEW有16.7±19.9尾和106.6±109.5g,是沿岸鱼类群聚的优势种或次优势种。但其年资源量并不稳定,最高的2010年是最低2002年的5.4陪。平均体长123.6±37.0mm,平均体重仅7.5±8.2g。0+龄组占78.9%,1+龄组占20.7%,2+龄仅出现在4、5月份,且仅占当月个体数的3.0%,幼体是沿岸刀鲚群体的主要组成成分。从0+龄个体的月度体长分布看,当年孵化的幼鱼大多栖息在河岸水域,沿岸生境在维持刀鲚幼鱼资源上具有重要作用。分析显示,4月1日至6月30日的长江禁渔期虽可保护约42.6%的幼鱼个体,但从保护效果看,还因适当延长沿岸水域的禁渔时间。维护沿岸水域的生境完整性,也是保护长江刀鲚幼鱼资源的重要措施。     

Fuelwood assessment at the micro-watershed level:a case study in Garhwal Himalaya,India

Biomass,as fuelwood,is one of the major sources of energy in rural areas,especially in the mountainous regions of the world.As the increasing human population exerts more pressure on the forest thereby inducing an adverse effect on the sustainability of the ecosystem,which consequently causes fuelwood crisis at a local level,this crisis is spatio-temporal in nature.Thus,the major objective of this study is to assess the sustainability of fuelwood at different probable scenarios at a micro watershed level.The present study was conducted in the Phakot watershed,the Tehri Garhwal district of central Himalaya in India,during 2006-2008.Based on the vegetation composition in the study area,the net primary productivity(NPP)value of the Oak forest,and mixed oak and sal forests,was used for the quantification of fuelwood availability in evergreen and deciduous forests,respectively.The fuelwood demand was calculated on the basis of seasonal fuelwood consumption values.Nine probable permutations for availability-demand scenarios assuming the existence of high(H),low(L)and average(A)conditions were analyzed for evaluating the stress.The available annual harvestable fuelwood in the watershed is in the minimum and maximum ranges of 2283.28 to 4066.00 tons,respectively,per year whereas it has a demand of 110.76 tons as the minimum to 3659 tons as the maximum annually.This shows that in the current availabilitydemand scenario,the watershed does not have fuelwood crisis in the present situation but needs to maintain the sustainability of the system.Based on our study,it is concluded that,globally,more spatio-temporal study is required to understand the issues at the local level.     

氮素和水分对贝加尔针茅草原土壤酶活性和微生物量碳氮的影响

在内蒙古贝加尔针茅草原,分别设对照（N0）、1.5 g·m^-2（N15）、3.0 g·m^-2（N30）、5.0 g·m^-2（N50）、10.0 g·m^-2（N100）、15.0 g·m^-2（N150）、20.0 g·m^-2（N200）和30 g·m^-2（N300）（不包括大气沉降的氮量）8个氮素（NH4NO3）梯度和模拟夏季增加降水100 mm的水分添加交互试验,研究氮素和水分添加对草原土壤养分、酶活性及微生物量碳氮的影响。结果表明：氮素和水分添加对草原土壤理化性质和生物学特性有显著影响。随施氮量的增加土壤总有机碳、全氮、硝态氮、铵态氮含量呈增加的趋势,相反,土壤pH值呈降低的趋势。土壤脲酶和过氧化氢酶的活性随施氮量的增加而升高,多酚氧化酶则随施氮量的增加呈下降的趋势。氮素和水分添加对草原土壤微生物量碳氮含量有显著影响,高氮处理（N150、N200和N300）显著降低了微生物碳含量,微生物氮含量随施氮量的增加呈上升趋势。水分添加能够减缓氮素添加对微生物的抑制作用,提高微生物量碳、微生物量氮含量。草原土壤养分、土壤酶活性及土壤微生物量碳氮含量间关系密切,过氧化氢酶与全氮、总有机碳、硝态氮呈显著正相关,多酚氧化酶与铵态氮、硝态氮、全氮呈显著负相关。微生物量氮含量与土壤全氮、铵态氮、硝态氮含量以及过氧化氢酶和磷酸酶活性呈显著正相关,与多酚氧化酶呈负相关;微生物量碳与过氧化氢酶呈负相关,与多酚氧化酶活性呈正相关。     

基于生物质能的芒属（Miscanthus）植物碳动态和收支研究进展

生物质能（Biomass energy）是最为广泛的可再生能源，其中多年生芒属C4植物（Miscanthus）由于具有巨大碳固定能力而成为潜力巨大的生物质能植物。中国是芒属植物芒草起源中心，但相对于欧洲国家应对能源危机和温室效应而采取的芒草研究与应用来说，仍处于起步阶段。我国长期以来传统的草地利用模式，决定了在南方草地的研究显著少于北方，近年来芒草在华南地区的运用研究集中于生态修复，对草本植物群落基于生态系统水平的 CO2气体交换能力的研究仍然相当缺乏，在二氧化碳浓度持续增长及全球变暖背景下，生物质能植物及其碳汇功能的相关研究尤显重要。我国南方近6700万hm2退化丘陵草坡急待恢复或处于恢复中，草坡地芒属植物符合生物质能植物标准，施肥少，害虫少，农药输入少，能够有效地利用光、水等自然资源。考虑到C4植物具有比C3植物更强的光合作用能力，高光能利用率C4芒属植物的碳固定能力及能源潜力值得重视，但缺乏科学的碳动态和碳收支评估。综述了国内外芒草生物量特征与生物质能潜力研究现状，重点论述芒属植物生态系统水平的碳动态和收支能力研究，探讨了系统水平更客观评估芒属碳源汇（Carbon sequestration）功能的方法，基于生物量过程的研究结果及华南地区草坡研究历史和现状，为草坡地生物质能的合理开发利用提出了相关对策，强调在我国南方开发和利用芒属植物资源具有重要能源价值和经济、环境效益。     

Heavy-metal adsorption by non-living biomass

The adsorption of some heavy metals onto the walls of harvested, washed, and dried non-living biomass cells of different Pseudomonas strains was studied at optimum experimental conditions using a simplified single component system. The Langmuir adsorption model was found to be a suitable approach to describe the system via multi-step processes. Isotherms measured at 30.0°C and pH 5.5 with [M]_total = 10-100 mM for tight, reversible Cr⁶⁺(aq), Ni²⁺(aq), Cu²⁺(aq) and Cd²⁺(aq) binding by the cell walls of the investigated biomass fit the Langmuir model and give the pH-independent stoichiometric site capacities ν_i and equilibrium constants K_i for metal binding at specific biomass sites i = A, B, C, and D. Tight binding sites A, B, and D of the non-living biomass are occupied by Cr^VI, sites A and C by Ni^II, sites A and D by Cd^II, and only site B by Cu^II. It is concluded that ν_i is a stoichiometric parameter that is independent of the magnitude of K_i for binding site i and that the studied heavy metals selectively and tightly bind at different biomass sites.     

Microbial biomass yield and turnover in soil biodegradation tests: carbon substrate effects

Most of the standardized biodegradation tests used to assess the ultimate biodegradation of environmentally degradable polymers are based solely on the determination of net evolved carbon dioxide. However, under aerobic conditions, it has to be considered that heterotrophic microbial consortia metabolize carbon substrates both to carbon dioxide and in the production of new cell biomass. It is generally accepted that in the relatively short term, 50% of the carbon content of most organic substrates is converted to CO₂, with the remaining carbon being assimilated as biomass or incorporated into humus. The latter is particularly important when the metabolism of the organic matter occurs in a soil environment. A straightforward relationship between the free-energy content of a carbon substrate (expressed as the standard free-energy of combustion) and its propensity for conversion to new microbial biomass rather than mineralization to CO₂ has been established. This can potentially lead to underestimation of biodegradation levels of test compounds, especially when they consist of carbon in a fairly low formal oxidation state and relatively high free-energy content. In the present work, the metabolism of different kind of carbon substrates, especially in soil, is reviewed and compared with our own experimental results from respirometric tests. The results show that conversion of highly oxidized materials, such as the commonly used reference materials, cellulose or starch, to CO₂ may be significantly overestimated. The addition of glucosidic material to soil leads to greatly increased respiration and is accompanied by a very low conversion to biomass or humic substances. In contrast, relatively less oxidized substrates metabolize more slowly to give both CO₂ and biomass to an extent which may be significantly underestimated if glucosidic materials are used as the reference. The need for an overall carbon balance taking into account both the carbon immobilized as biomass and that volatized as CO₂ must be considered in standard respirometric procedures for assessing the biodegradability of slowly degrading macromolecules.     

Effect of land management on soil microbial N supply to crop N uptake in a dry tropical cropland in Tanzania

In Sub-Saharan Africa, conservation of available soil N during early crop growth, when N loss by leaching generally occurs, is important to improve crop productivity. In a dry tropical cropland in Tanzania, we assessed the potential role of soil microbes as a temporal N sink-source to conserve the available soil N until later crop growth, which generally requires substantial crop N uptake. We evaluated the effect of land management [i.e., no input, plant residue application before planting (P plot) with or without fertilizer application, fertilizer application alone, and non-cultivated plots] on the relationship between soil N pool [microbial biomass N (MBN) and inorganic N] and crop N uptake throughout the ∼120-d crop growth period in two consecutive years. In the P plot, MBN clearly increased (∼14.6-29.6 kg N ha⁻¹) early in the crop growth period in both years because of immobilization of potentially leachable N, and it conserved a larger soil N pool (∼10.5-21.2 kg N ha⁻¹) than in the control plot. Especially in one year in which N leaching was critical, increased MBN maintained a larger soil N pool in the P plot throughout the experimental period, and a delay of increased MB C:N ratio and a substantial decrease in MBN was observed, indicating better soil microbial N supply for crop N uptake during later crop growth. Therefore, plant residue application before planting should enhance the role of soil microbes as a temporal N sink-source, leading to the conservation of potentially leachable N until later phase of crop growth, especially in years in which N leaching is relatively severe. Although further studies are necessary, our results suggest that plant residue application before planting is a promising option to achieve better N synchronization.     

Differences in nitrous oxide fluxes from red soil under different land uses in mid-subtropical China

Red soil may play an important role in nitrous oxide (N₂O) emissions due to its recent land use change pattern. To predict the land use change effect on N₂O emissions, we examined the relationship between soil N₂O flux and environmental determinants in four different types of land uses in subtropical red soil. During two years of study (January 2005-January 2007), biweekly N₂O fluxes were measured from 09:00 to 11:00 a.m. using static closed chamber method. Objectives were to estimate the seasonal and annual N₂O flux differences from land use change and, reveal the controlling factors of soil N₂O emission by studying the relationship of dissolved organic carbon (DOC), microbial biomass carbon (MBC), water filled pore space (WFPS) and soil temperature with soil N₂O flux. Nitrous oxide fluxes were significantly higher in hot-humid season than in the cool-dry season. Significant differences in soil N₂O fluxes were observed among four land uses; 2.9, 1.9 and 1.7 times increased N₂O emissions were observed after conventional land use conversion from woodland to paddy, orchard and upland, respectively. The mean annual budgets of N₂O emission were 0.71-2.21 kg N₂O-N ha⁻¹ year⁻¹ from four land use types. The differences were partly attributed to increased fertilizer use in agriculture land uses. In all land uses, N₂O fluxes were positively related to soil temperature and DOC accounting for 22-48% and 30-46% of the seasonal N₂O flux variability, respectively. Nitrous oxide fluxes did significantly correlate with WFPS in orchard and upland only. Nitrous oxide fluxes responded positively to MBC in all land use types except orchard which had the lowest WFPS. We conclude that (1) land use conversion from woodland to agriculture land uses leads to increased soil N₂O fluxes, partly due increased fertilizer use, and (2) irrespective of land use, soil N₂O fluxes are under environmental controls, the main variables being soil temperature and DOC, both of which control the supply of nitrification and denitrification substrates.     

Glucose production from hydrolysis of cellulose over a novel silica catalyst under hydrothermal conditions

A novel silica catalyst was synthesized by evaporation-induced self-assembly (EISA) method and tested for the catalytic selective hydrolysis of cellulose to glucose. This silica catalyst exhibited a higher catalytic activity than other oxides prepared by the same method, such as ZrO₂, TiO₂, and Al₂O₃. Using silica as a catalyst, cellulose was selectively hydrolyzed into glucose with a glucose yield as high as 50% under hydrothermal conditions without hydrogen gas. The silica catalyst was characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results of temperature-programmed desorption of ammonia (NH₃-TPD) and textural properties indicated that the synergistic effect between strong acidity and a suitable pore diameter of the silica catalyst may be responsible for its high activity. In addition, the catalyst was recyclable and showed excellent stability during the recycle catalytic runs.     

Responses of protists with different feeding habits to the changes of activated sludge conditions: A study based on biomass data

Changes of protists, which were categorized into different functional groups primarily according to their feeding habits, in two full-scale municipal wastewater treatment systems experiencing sludge bulking were investigated over a period of 14 months. Protist biomass represented 3.7% to 5.2% of total biomass on average under normal sludge conditions, and the percentage increased significantly (p < 0.05) under sludge bulking conditions. The biomass of Chilodonella spp., capable of eating filamentous bacteria, tended to decrease in both systems when sludge bulking occurred, showing that the abnormal growth of filamentous bacteria did not lead to a biomass bloom of this group of protists. On the other hand, the bactivorous protists represented more than 96% of total protist biomass, and the biomass of this group, particularly the attached ciliates, increased significantly (p < 0.05) when sludge bulking occurred. The significant increase of the attached ciliates may have possibly facilitated the growth of filamentous bacteria through selectively preying on non-filamentous bacteria and further exacerbated sludge bulking. The redundancy analysis and correlation analysis results showed that the biomass changes of the attached ciliates were primarily related to the sludge volume index and to some extent related to five-day biochemical oxygen demand loading and hydraulic retention time.