Regional and local factors affecting diversity, abundance and activity of free-living, N2-fixing bacteria in Australian agricultural soils

N₂-fixation by free-living (diazotrophic) microorganism is a key process affecting ecosystem functioning in soils. Understanding drivers affecting diazotrophic community assemblages and activities may lead to management practices to increase primary production and/or environmental sustainability. We used PCR-DGGE to determine the fundamental relationships between diazotrophic community structure and in a wide range of soils across southern Australia. In addition qPCR, RT-qPCR and N₂-fixation (acetylene reduction) were used to investigate factors influencing gene abundance, expression and processes in similar soils with different agricultural inputs. Across 22 soils, the structural composition of the nifH community was significantly influenced by site (ANOSIM R = 0.876; P = 0.001). The effects of management practices were evident, and often larger than between-soil differences, but were only present at some sites. Differences in nifH communities between sites correlated to particulate organic carbon (POC; measured by mid-infrared spectroscopy) content of the soils (BIO-ENV test; ρ = 0.502; P = 0.001), but not other factors including total soil C. In 3 soils from the Murrumbidgee irrigation region of NSW, intensification of the farming systems was associated with increasing N₂-fixation (P < 0.05), except where rice was cultivated. N₂-fixation correlated either with nifH abundance or gene expression in soils, but not both. Our data shows that soil C is closely linked to diazotrophic ecology. Principally, the amount of C entering the soil system is directly related to the abundance and N₂-fixation activity of free-living bacteria. However, we also show that C in the POC pool has associative links to the genetic diversity of the soil diazotroph community. Given the importance of diversity and abundance of functional organisms in supporting ecosystem processes, we suggest that soil C inputs should be considered for both qualitative and quantitative properties when considering impacts on diazotrophic bacterial ecology.     

耕作方式对紫色水稻土总有机碳及颗粒态有机碳的影响

为研究耕作方式对西南地区紫色水稻土总有机碳及颗粒态有机碳的影响,以1989年设立的位于西南大学农场的农业部重庆紫色土生态环境重点野外科学观测试验站内的长期免耕试验田为对象,研究在冬水田平作（DP）、水旱轮作（SH）、垄作免耕（LM）、厢作免耕（XM）和垄作翻耕（LF）5种不同耕作方式下,土壤中总有机碳（TOC）含量、颗粒态有机碳（POC）含量、颗粒态土壤质量分数和颗粒态有机碳分配比在土壤中的分布特点。结果表明,不同的耕作方式主要对表层土壤的TOC、POC分布产生显著影响,其中LM对提高积累TOC和POC贡献最大;0-60 cm土层TOC含量变化范围为7.10～34.45 g/kg,颗粒态土壤质量分数所占比例为30.38%～45.65%,POC含量为1.31～19.39 g/kg,各数值基本变化趋势都是随土壤深度的增加而减小。TOC与POC都可作为评价耕作方式影响紫色水稻土土壤质量变化与固碳能力的有效指标,但相同耕作制度下POC变化幅度更大,对其响应也更为敏感。从TOC和POC的关系来看,不同耕作制度下有机碳的增加与土壤物理保护能力的提高有关,免耕方式有利于有机碳以及颗粒态有机碳的保护和稳定。     

猪APOA5和APOC3基因mRNA的表达差异及与肌内脂肪沉积的相关性分析

为了探究载脂蛋白A5（apolipoprotein A5,APOA5）基因和载脂蛋白C3（apolipoprotein C3,APOC3）基因组织表达差异及其与肌内脂肪（intramuscular fat,IMF）沉积的相关性,本研究利用荧光定量PCR方法分析APOA5和APOC3基因mRNA在可乐猪和江口萝卜猪7个组织中的相对表达量及其与IMF沉积的相关性。研究结果表明：APOA5和APOC3基因在可乐猪和江口萝卜猪的7个组织中均有不同程度表达,在肝脏中表达量最高,在皮下脂肪和背最长肌中表达量次之;APOA5基因在可乐猪多数组织中的表达量显著低于江口萝卜猪（p〈0.05）,而APOC3基因未呈现类似规律性;可乐猪中,除心脏外,其它组织均表现为APOC3基因mRNA表达量高于APOA5,江口萝卜猪心脏、肝脏、脾脏、小肠和背最长肌中同样呈现上述表达差异。相关及回归分析表明,IMF沉积量与可乐猪APOC3 mRNA表达丰度呈线性正相关（p〈0.05）。根据研究结果,可以推测APOA5和APOC3基因与IMF沉积有一定关联性。     

中亚热带退化林地土壤有机碳及不同粒径土壤颗粒有机碳的变化

采用土壤颗粒分级方法,以湘中丘陵区地域相邻、环境条件基本一致的4种林地:檵木—南烛—满山红灌草丛(LVR)、檵木—杉木—白栎灌木林(LCQ)、马尾松—石栎—檵木针阔混交林(PLL)和石栎-红淡比-青冈常绿阔叶林(LAG)为对象,研究土壤有机碳(SOC)及不同粒径土壤颗粒有机碳含量随着林地退化的变化特征,剖析林地退化对中亚热带森林SOC库的影响机制。结果表明:随着林地退化,2μm砂粉粒百分含量增高,而2μm黏粒百分含量下降,土壤质地粗砂化;林地SOC含量呈负指数函数下降,LAG林地SOC库以粉粒、黏粒有机碳为分配主体,PLL、LCQ、LVR林地以粉粒、砂粒有机碳为分配主体;随着林地退化,同一土层同一粒径有机碳含量呈下降趋势,砂粒有机碳含量的分配比例明显增加,黏粒有机碳含量的分配比例明显下降,同一土层颗粒有机碳(POC)/矿物结合有机碳(MOC)值增加,SOC固持和保护作用减弱,SOC稳定性下降。群落物种组成、生物量和土壤颗粒组成随着林地退化的变化是导致林地SOC含量和稳定性下降的主要因素。     

对虾池生态系统溶解有机碳及颗粒有机碳的周日动态

对两个海水养虾池溶解有机碳（ＤＯＣ）及颗粒有机碳（ＰＯＣ）的周日动态进行了研究,结果表明,ＤＯＣ的浓度,１４：００～１８：００下降,１８：００～２２：００升高,之后又下降,周日波动幅度为３．２２ｍｇ／Ｌ（１池）及１．２４ｍｇ／Ｌ（２池）ＰＯＣ浓度白天（６：００～１８：００）升高,夜间（１８：００～次日６：００）下降,周日波动幅度为１．２８ｍｇ／Ｌ（１池）及１．２６ｍｇ／Ｌ（２池）。ＰＯＣ浓度高的虾     

Usefulness of a Point-of-Care Analyzer to Measure Cardiac Troponin I and D-Dimer Concentrations in Critically Ill Horses With Gastrointestinal Diseases

Point-of-care (POC) systems for the joint measurement of Troponin and D-dimers have not been studied in horses. The aim of this study was to perform the validation of a POC system (AQT90 FLEX) for the measurement of cardiac troponin I (cTnI) and D-dimers in the serum of horses with gastrointestinal diseases. The main objective was to evaluate whether or not this system can distinguish healthy animals from diseased animals. A sample of 33 horses was included in the study: control group (n = 10) and horses with gastrointestinal disorders (n = 21), which were classified according to their outcome in survivors (subgroup A = 9) and nonsurvivors (subgroup B = 12). Considering the diagnosis of the process, ill horses were classified into three groups: inflammatory (I = 7), obstructive (O = 9), and strangulating diseases (S = 5). The clinical usefulness of AQT90 FLEX was validated by the study of linearity, coefficient of variation, and detection limits. Later, concentrations of D-dimers and cTnI were measured. A significant increase in both parameters was detected in ill animals (cTnI: control: 0.014 ± 0.01 μg/mL, survivors: 0.27 ± 0.37 μg/mL, nonsurvivors: 0.60 ± 1.21 μg/mL; D-dimers: control: 104.90 ± 30.82 ng/mL, survivors: 1,217.22 ± 1,213.28 ng/mL, nonsurvivors: 1,613.67 ± 1,426.75 ng/mL), although there were no statistically significant differences in concentrations according to diagnosis and outcome. In conclusion, AQT90 FLEX POC analyzer can be used in horses with gastrointestinal diseases to measure cTnI and D-dimer concentrations. It is a quick, practical, and minimally invasive tool that helps in determining the severity of illness.     

改良剂对复垦土壤水稳性团聚体及POC和MOC的影响

为探究改良剂对煤矿复垦土壤有机碳的影响,以山西省襄垣县煤矿复垦区复恳7年的土壤为研究对象,采用田间微区的方法研究了泥炭和腐殖酸对复垦土壤及各粒级水稳性团聚体颗粒态有机碳(POC)和矿物结合态有机碳(MOC)的影响。结果表明:施用泥炭和腐殖酸均能增加复垦土壤水稳性大团聚体(>0.25 mm)含量,但6个月后,水稳性大团聚体会减少,而水稳性微团聚体(<0.25 mm)会增加,>2 mm和<0.25 mm粒级的团聚体变化较大,2种改良剂相比,腐殖酸各处理土壤大团聚体及微团聚体的变化比泥炭大。泥炭和腐殖酸均能增加复垦土壤总POC、MOC含量及各粒级水稳性团聚体中的POC、MOC含量,施用比例相同时,施用腐殖酸的土壤POC、MOC增量更大,施用泥炭6个月和1年后土壤POC含量变化分别为2.14~8.89,1.53~5.00 g/kg,施用腐殖酸6个月和1年后土壤POC含量变化分别为8.07~20.12,5.63~19.36 g/kg,施用泥炭6个月和1年后土壤MOC含量变化分别为4.84~10.51,5.41~8.08 g/kg,施用腐殖酸6个月和1年后土壤MOC含量变化分别为9.10~35.34,5.91~30.00 g/kg。但6个月后,泥炭和腐殖酸各处理土壤POC和MOC含量会减少。施用泥炭和腐殖酸会降低土壤有机碳的稳定性,不利于有机碳的储存。     

用后处理装置减少DMDF发动机的有害排放

目的 在一台增压中冷电控单体泵的四缸柴油机上采用柴油/甲醇双燃料（DMDF）燃烧方式进行台架实验,研究了甲醇替代率和不同后处理装置对有害气体、烟度和微粒排放特性的影响。结果 结果表明：在排气管加装柴油机氧化催化转化器（DOC）耦合微粒催化转化器(POC)可以大幅降低双燃料燃烧产生的THC和CO,基本可以实现零排放;与催化前相比,微粒的总数量浓度和总质量浓度均有大幅度降低,平均降幅分别为91.7%和88.1%;烟度排放得到改善,平均降幅为21.9%;同时,该后处理装置对DMDF发动机的NO_x排放无明显影响。与之不同,双DOC耦合的后处理装置对THC和CO的催化效率略优于DOC+POC,但在大部分工况下会导致NO_x和烟度排放的同时增加。