蚂蚁扰动对青海湖北岸高寒草甸草原群落结构影响

蚂蚁的筑丘活动是草地生态系统中不可忽视的生物干扰因子。本文针对青海湖北岸高 寒草甸草原,调查了不同大小的蚁丘及其周围对照草地的土壤理化性质和植被状况。结果表明： 蚂蚁筑丘活动显著地降低了土壤容重和土壤湿度,增加土壤温度,但对土壤pH 值的影响较小。 蚂蚁扰动改变了群落组成,增加了大部分禾本科和豆科物种的重要值而降低了杂类草的重要值。 以莎草科的矮嵩草（Kobresia humilis）和禾本科的异针茅（Stipa aliena Keng）、赖草（Leymus secalinus）、溚草（Koeleria cristata）等为主的群落逐步演替为以禾本科的异针茅和赖草为主的 群落。植物群落的盖度降低但其地上、地下生物量增加;植物群落丰富度指数降低但均匀度指 数增加。     

生物质发电项目碳排放计算方法应用研究

生物质发电是将废弃生物质变成可再生能源得以充分利用,这些工程将减少来自于生物质自然腐烂和无控燃烧产生的温室效应,这不仅节约了煤炭的同时也减少了二氧化碳的排放。本文中以某生物质项目发电为例,根据CDM方法学ACM0006计算了该项目的减排量。结果表明,该项目10年间共减少了二氧化碳排放量2,075,140 t,给我国带来了可观的经济效益和环境效益。     

巢湖藻类生物量季节性变化特征

在2008年对巢湖浮游藻类的生态分布进行了为期1 a的调查研究,并采用自制"藻类上浮/下沉捕集器"定量研究了水柱中藻类上浮和下沉速率的季节性变化.结果表明,蓝藻为巢湖主要的水华优势群落,但各个季节优势水华种群有所差别,春季鱼腥藻占优势,微囊藻次之;夏、秋两季微囊藻占绝对优势.5月开始,水柱中藻类生物量明显增加;8月份达到最大值,叶绿素含量全湖平均为146.37 mg.m-3.表层沉积物中藻类生物量在9.75～16.24 mg.kg-1之间,最小值出现在夏季,然后逐渐升高,最大值出现在冬季的11月.研究期间(5～10月),水柱中浮游藻类一直存在上浮和下沉现象,上浮速率在总体上呈先上升后下降的趋势,最大值出现在8月初,为0.036 8 mg.(m2.d)-1;下沉速率则呈现先缓慢上升后急剧下降的趋势,最大值出现在9月初,为0.032 1 mg.(m2.d)-1.多元逐步回归统计表明,温度是巢湖藻类生物量变化最为显著的影响因子,其次为总氮(TN)和总磷(TP).     

祁连山高山草甸土壤CO2通量的时空变化及其影响分析

采用Li-6400便携式光合作用测量系统连接Li-6400-09土壤呼吸室,在2004年生长季节对祁连山高山草甸土壤CO₂通量沿海拔梯度进行了野外定位试验,统计分析了水热因子及根系生物量对高山草甸土壤CO₂通量特征的可能影响.结果表明,土壤CO₂通量存在明显的空间变化规律, 沿海拔梯度土壤CO₂通量随着海拔梯度的增加而逐渐减小,其变异系数逐渐增加;就日变化而言,土壤CO₂通量晚间维持在较低水平,02：00～06：00最低,在07：00～08：30开始升高,11：00～16：00达到峰值,16：00～18：30开始下降,整个过程呈单峰曲线.土壤CO₂通量的日平均值介于(0.56±0.32) ～ (2.53±0.76) μmol·(m²·s)^-1.从季节变化来看,土壤CO₂通量均以夏秋季较高,春冬季排放量较低,7～8月份达到最大值［4.736 μmol·(m²·s)^-1］,6月与9月份次之,5月与10月份基本一致,整个生长过程总的变化趋势呈单峰曲线形式.高山草甸土壤CO₂通量在植物生长季与10 cm土壤温度、土壤含水量、根系生物量都存在不同程度的正相关关系,表明高山草甸土壤CO₂通量的空间变异主要受温度、水分和植物根系的综合影响.     

Emissions of SO2, NO and N2O in a circulating fluidized bed combustor during co-firing coal and biomass

This paper presents the experimental investigations of the emissions of SO2, NO and N2O in a bench scale circulating fluidized bed combustor for coal combustion and co-firing coal and biomass. The thermal capacity of the combustor is 30 kW. The setup is electrically heated during startup. The influence of the excess air, the degree of the air staging, the biomass share and the feeding position of the fuels on the emissions of SO2, NO and N2O were studied. The results showed that an increase in the biomass shares resulted in an increase of the CO concentration in the flue gas, probably due to the high volatile content of the biomass. In co-firing, the emission of SO2 increased with increasing biomass share slightly, however, non-linear increase relationship between SO2 emission and fuel sulfur content was observed. Air staging significantly decreased the NO emission without raising the SO2 level. Although the change of the fuel feeding position from riser to downer resulted in a decrease in the NO emission level, no obvious change was observed for the SO2 level. Taking the coal feeding position R as a reference, the relative NO emission could significantly decrease during co-firing coal and biomass when feeding fuel at position D and keeping the first stage stoichiometry greater than 0.95. The possible mechanisms of the sulfur and nitrogen chemistry at these conditions were discussed and the ways of simultaneous reduction of SO2, NO and N2O were proposed.     

Elevated CO2 changes the moderate shade tolerance of yellow birch seedlings

To demonstrate the existence of light thresholds in plant growth and to examine the effects of elevated CO2 on the shade tolerance of a tree species, an experiment consisting of a completely randomized design for a total of 96 yellow birch (Betula alleghaniensis Britton) seedlings was conducted with 3 light levels (2.9%, 7.7%, 26.1% of full sunlight)×2 CO2 levels (350 and 700±10 ppm) with 4 replications in a phytotron. The study proved that thresholds exist and they vary in different plant organs. In ambient CO2, the thresholds were 13.3%, 18.7%, 15.0%, 15.2%, and 15.6% of full sunlight for stem, leaf, root, total plant biomass, and the averaged value, respectively. In 700 ppm CO2, the corresponding thresholds were 16.7%, 21.3%, 18.1%, 21.7% and 19.5% for stem, leaf, root, total plant biomass, and the averaged value, respectively. The lowest threshold in the stem is an indicator of the minimal light intensity for regular growth for seedlings of this species. Below this threshold, light-stressful growth occurs. The result of a paired t-test indicated that the thresholds in elevated CO2 were significantly higher than in ambient CO2. This suggests that yellow birch will lose its moderate shade tolerance, evolutionally becoming a shade-intolerant species, and that it may become more difficult to naturally regenerate in the future.     

Effect of sulfate on the methanogenic activity of a bacterial culture from a brewery wastewater during glucose degradation

The maximum specific methanogenic activity （SMA） of a sludge originating from a brewery wastewater treatment plant on the degradation of glucose was investigated at various levels of sulfate on a specific loading basis. Batch experiments were conducted in serum bottles at pH 7 and 35℃. A comparison of the values indicates that the SMA of this mixed culture was increased and reached its highest level of 0.128 g CH4 gas COD/（g VSS.d） when biomass was in contact with sulfate at a ratio of 1：0.114 by weight.     

上吸式生物质气化炉焦油成分的分析

文章在10 KWth上吸式生物质气化炉上进行木屑的气化实验,通过改变床层高度和气化剂空气的量,将产生的生物质焦油进行取样。经GC-MS分析得出上吸式气化炉焦油的主要成分为初级和二级焦油,其中以酚类焦油所占比重最多,大约为总量的38%~60%;在同样床高的条件下,随着空气量的增加,酚类焦油含量有所降低,但仍然是焦油中比重较大的。     

生物炭对塿土土壤温室气体及土壤理化性质的影响

通过田间小区试验,分别向塿土土壤中添加0、20、40、60、80 t·hm~(-2)的苹果果树枝条生物炭后,分析了生物炭对土壤温度、土壤团聚体、NO_3~--N、NH_4~+-N、微生物量碳以及土壤温室气体排放的影响.结果表明,生物炭可以缓解土壤温度的变化,增加土壤大团聚体的数量,尤其是5 mm、5~2 mm和1~0.5 mm的团聚体数量.与对照相比,随着生物炭施用量的增加,土壤NO_3~--N、NH_4~+-N、微生物量碳分别增加了4.9%~33.9%、9.1%~41.1%和11.8%~38.5%.本研究中生物炭对土壤温室气排放的影响主要表现为:添加生物炭后,土壤CO_2的排放量以及CH_4的吸收汇分别增加了6.73%~23.35%和3.62%~14.17%;施用20 t·hm~(-2)和40 t·hm~(-2)的生物炭降低了土壤N_2O的排放和综合增温潜势(GWP),而当生物炭施用量大于等于60 t·hm~(-2)时反而增加了土壤N_2O的排放和综合增温潜势(GWP).说明生物炭作为一种土壤改良剂和碳减排剂,能够改善土壤质量,提高土壤肥力,提高农田土壤增汇减排的作用,此外,选择合适的生物炭施用量至关重要.     

水稻光合同化碳在土壤中的矿化和转化动态

作物光合碳是"大气-植物-土壤"碳循环的重要组成部分,是农田土壤有机碳的重要来源,然而其在土壤碳库中的矿化和转化动态尚不清楚.应用室内模拟培养实验,研究水稻收获后输入土壤的光合同化碳在土壤碳库中的矿化及其转化特征.结果表明,100 d的培养期内,原有有机碳的平均矿化速率在4.44~17.8μg·(g·d)-1之间,而光合碳(新碳)的矿化速率则在0.15~1.51μg·(g·d)-1之间.光合同化碳的输入对土壤活性碳库(DOC、MBC)的转化产生显著影响,在培养期内,14C-DOC的转化量为1.89~5.32 mg·kg-1,转化速率的变化幅度为0.18~0.34 mg·(kg·d)-1,原有DOC则在61.13~90.65 mg·kg-1,减少幅度为4.10~5.48 mg·(kg·d)-1;14C-MBC和原有MBC的转化量分别为10.92~44.11 mg·kg-1和463.31~1 153.46mg·kg-1,转化速率变化幅度分别为0.80~2.87 mg·(kg·d)-1和41.60~74.46 mg·(kg·d)-1,说明水稻光合碳的输入对MBC的周转要大于DOC的周转.而且,与原有有机碳相比,输入的"新碳"易被微生物矿化分解,100 d的培养期内,有13.5%~20.2%的新碳被矿化分解,而仅2.2%~3.7%的原有有机碳被矿化分解,光合同化碳的输入对维持稻田土壤的碳汇功能具有重要作用.