氯甲基吡啶对滴灌棉田土壤微生物群落功能多样性的影响

已知硝化抑制剂氯甲基吡啶能有效抑制土壤硝化,减少氮的淋洗和硝化-反硝化损失,促进作物对氮素的吸收,但是其对干旱区滴灌条件下土壤微生物群落功能多样性的影响尚不明确。本试验研究了尿素添加氯甲基吡啶(Nitrapyrin)分次随水滴施对干旱区滴灌棉田土壤微生物碳代谢和群落功能多样性的影响。试验采用随机区组设计,设置不施氮肥[CK,0 kg(N)·hm~(-2)]、单施尿素[Urea,225 kg(N)·hm~(-2)]和尿素添加氯甲基吡啶[Urea+nitrapyrin,225 kg(N)·hm~(-2)+2.25 kg(nitrapyrin)·hm~(-2)]3个处理,重复4次,采用Biolog-ECO法进行土壤微生物碳代谢和功能多样性研究。结果表明:与不施氮肥(CK)相比,施用尿素和尿素添加氯甲基吡啶均能显著提高土壤微生物对31种碳源的代谢能力(AWCD)和代谢强度(S)(P0.05),增加土壤微生物多样性和丰富度(Shannon指数、Simpson指数、Mc Intosh指数和Richness指数)以及对各类碳源的利用能力。尿素添加氯甲基吡啶随水滴施后,土壤微生物AWCD值、碳代谢强度、Shannon指数、Simpson指数、Mc Intosh指数以及Richness指数均大于单施尿素处理,且较单施尿素处理分别提高13.83%、9.33%、1.29%、1.34%、11.26%、11.79%(P0.05),均匀度指数则低于单施尿素处理(P0.05)。PCA和聚类分析结果表明,施用尿素和尿素添加氯甲基吡啶对土壤微生物群落功能多样性均产生了显著影响,但尿素添加氯甲基吡啶与单施尿素处理差异不显著;氯甲基吡啶的添加提高了土壤微生物对聚合物、酚酸、羧酸、氨基酸以及胺类的利用,降低了对碳水化合物的利用(P0.05)。上述研究结果得出,在干旱区滴灌棉田,尿素添加氯甲基吡啶分次随水滴施可调控土壤的微生态环境,在一定程度上提高土壤微生物的代谢能力,增加微生物群落功能多样性,缓解因长期施用无机氮肥导致的土壤微生物活性的降低。     

市售山茶油功能性脂肪酸组成分析

研究了市场上畅销的8种山茶油的功能性脂肪酸的组成,采用了氢氧化钾-甲醇甲酯化法和GCMS分析法,以棕榈酸甲酯、硬脂酸甲酯、油酸甲酯及亚油酸甲酯为对照品,在制定4种脂肪酸甲酯的标准曲线(r0.999)和回归方程的基础上,计算各脂肪酸绝对含量。结果表明,8种山茶油中棕榈酸、硬脂酸、油酸及亚油酸的含量分别为老知青山茶油(3.83%、0.77%、25.07%、4.08%),润心山茶油(4.52%、0.99%、35.46%、5.57%)、源森山茶油(3.44%、0.93%、25.72%、4.30%)、绿海山茶油(3.76%、0.69%、24.41%、3.73%)、得尔乐山茶油(5.07%、1.09%、41.90%、6.22%)、山润山茶油(4.64%、1.04%、35.41%、5.44%)、贵太太山茶油(4.05%、0.99%、32.01%、4.62%)、金浩山茶油(4.66%、1.06%、35.81%、6.04%)。8种山茶油中油酸含量25.07%~41.90%,亚油酸含量3.73%~6.22%,未检测到亚麻酸。     

Arbuscular mycorrhizal fungi reduce ammonia emissions under different land-use types in agro-pastoral areas

Ammonia (NH₃) emissions, the most important nitrogen (N) loss form, always induce a series of environmental problems such as increased frequency of regional haze pollution, accelerated N deposition, and N eutrophication. Arbuscular mycorrhizal (AM) fungi play key roles in N cycling. However, it is still unclear whether AM fungi can alleviate N losses by reducing NH₃ emissions. The potential mechanisms by which AM fungi reduce NH₃ emissions in five land-use types (grazed grassland, mowed grassland, fenced grassland, artificial alfalfa grassland, and cropland) were explored in this study. Results showed that AM fungal inoculation significantly reduced NH₃ emissions, and the mycorrhizal responses of NH₃ emissions were determined by land-use type. Structural equation modeling (SEM) showed that AM fungi and land-use type directly affected NH₃ emissions. In addition, the reduction in NH₃ emissions was largely driven by the decline in soil NH⁺₄-N and pH and the increases in abundances of ammonia-oxidizing archaea (AOA) amoA and bacteria (AOB) amoB genes, urease activity, and plant N uptake induced by AM fungal inoculation and land-use type. The present results highlight that reducing the negative influence of agricultural intensification caused by land-use type changes on AM fungi should be considered to reduce N losses in agriculture and grassland ecosystems.     

Long-term trends in vegetation changes of managed versus unmanaged Eastern Carpathian beech forests

A vegetation survey of semi-permanent plots was conducted between years 1955–1962 and 2005–2009, and aimed to determine floristic changes occurring in beech forests located on a scarcely populated, dense forest area. The survey encompassed all natural beech forest types within the Polish part of the “Eastern Carpathians” International Reserve of Biosphere. A comparison of trends in changes between unmanaged (Bieszczady National Park) and managed (the remaining part of the Biosphere Reserve) forests was attempted. DCA analysis was used for the determination of changes on the community level. The density of vegetation, species richness, frequency of occurrence and cover, and functional groups of species were determined. Much more profound community changes were determined to have occurred in managed beech forests. However, a similar direction in vegetation changes within both managed and unmanaged forests verifies the existence of a regional pattern of changes in beech forests. This regional pattern involves (1) a decrease in the shares of arborescent species within the shrub layer, (2) disturbance of the canopy layer, (3) acidification of the top layer of the soil, (4) change of light conditions, (5) increase in shares of generalist species and decrease in shares of specialist species. A decreasing anthropogenic pressure, aging of forest stands, functioning of large, dense forest areas and sustainable forest management strategies forestry management system mimicking natural deciduous forest disturbance regime constitute factors shaping the regional changes of the forest vegetation. The undergoing changes can lead to biotic and spatial homogenization of the Eastern Carpathian beech forests.     

河南省农业产业集群的现状及对策研究

在阐述农业产业集群的内涵的基础上,介绍了农业产业集群竞争优势：一是促使农业生产要素集聚,降低农业生产成本;二是提高产业创新能力;三是提高农村的城镇化水平,增加农民收入。分析了河南农业产业集群发展的现状,指出其有资源、成本、区位等优势,探讨了河南省农业产业集群存在的问题：一是农业产业集群规模较小,产业链条较短;二是龙头企业数量偏少,产业集群内辐射带动能力不强;三是农业产业集群的组织化程度较低,缺乏科技创新能力。为了解决产业集群中存在的问题,提出了相应的对策建议,一是以市场为导向,加强政策制定,稳步推进河南省农业产业集群的发展;二是要选择合适的农业产业集群发展模式。     

川西亚高山林线交错带及邻近植被土壤细菌生理群数量特征

研究川西亚高山林线交错带及上缘流石滩草甸和下缘冷杉林土壤8种细菌生理群数量的空间分布和时间动态特征。结果表明:不同植被细菌生理群数量均随土壤深度加深而降低;0～30cm土层硝化细菌、反硝化细菌、好气固氮菌、有机磷分解菌和好气纤维素分解菌数量表现为林线交错带下缘冷杉林上缘流石滩草甸,而氨化细菌、无机磷分解菌和厌气纤维素分解菌除上缘流石滩草甸最低外,林线交错带与下缘冷杉林无显著差异;氨化细菌、有机和无机磷分解菌是各植被土壤中的优势菌群,纤维素分解菌数量最低;在0～15cm土层,上缘流石滩草甸各菌群数量4月最低,6月最高,林线交错带及下缘冷杉林各菌群数量亦4月最低,厌气性的反硝化细菌与厌气纤维素分解菌6月最高,其余菌群均8月达最大值;而各植被底层土壤各细菌生理类群数量无明显时间动态规律;林线交错带及邻近植被细菌生理群的空间分布与时间动态与土壤的立地条件、营养成分、水热条件变化关系密切。     

风景名胜区功能区划分与旅游空间结构研究——以天台山-七里坪风景名胜区为例

笔者在分析旅游规划分区原则的基础上,依据地域完整性,并突出特色的原则,提出将天台山—七里坪风景名胜区分为5大类功能区,并对各个功能区的规划指引和控制要点作了进一步分析。此外,根据风景区景观资源分布、开发价值和适宜性,创新性地提出将该风景名胜区在空间布局上采用"一轴四环五区"的旅游空间结构。     

跨区域粮食销售市场中各主体利益的协调分析

本文以粮食销售市场中粮食所有权的流程为线,对市场中各利益主体间的关系进行探讨,并运用交易费用理论,分析市场粮源充足和市场粮源不充足两种情况下阻碍跨区域粮食流通的主要因素。结果表明,降低市场交易费用、提高粮食购销企业间的交易效率是协调粮食销售市场各主体利益、顺畅跨区域粮食流通的关键。最后,从政府的角度,针对如何提高不同市场供需情况下购销企业的交易效率问题,提出政策建议。     

硬球链流体在硬球粒子表面的密度分布和剩余吸附研究

在密度泛函的理论(Density Functional Theory,DFT)框架下,应用Yu等改进的基本度量理论(Modified Fundamental Measure Theory,MFMT)和Wertheim等发展的微扰理论分别表达剩余自由能的硬球作用和链连接作用,对硬球链流体体系进行了研究,建立了适用于均匀和非均匀流体的状态方程和化学势,得到了硬球链流体在硬球粒子表面的密度分布表达式,计算了在硬球粒子表面的链节密度分布,并将理论计算数据与叶等进行的Monte Carlo计算机模拟所得数据进行比较,结果吻合较好。此外,还进一步探讨了硬球粒子尺度和硬球链链节数对体系剩余吸附的影响。     

取代芳烃对大型蚤急性毒性的定量构效关系研究

[目的]建立具有良好相关性和稳定性的取代芳烃对大型蚤定量结构-活性关系（QSAR）模型。[方法]采用Gaussian03程序包中密度泛函理论（DFT）B3LYP方法计算取代芳烃的部分结构参数和毒性参数。[结果]-lgEC50的回归方程为-lgEC50=4.496＋1.5×10-2MM＋9.958×EHOMO＋0.677×ΔQR;方程中各自变量的变异膨胀因子（VIF）分别为：1.508、1.364和1.157。取代芳烃对大型蚤急性毒性的主要影响因子为分子量MM、分子最高占有轨道能EHOMO和苯环上净电荷增量ΔQR,且这3个结构参数与-lgEC50正相关,其标准系数分别为0.986、0.289和0.175。分子量越大,分子总能量（能量为负值）越低,化合物越稳定,毒性越大;分子量越大,lgP越大,化合物的脂溶性越大,毒性越大。[结论]该试验建立的模型具有良好的稳定性和很强的预测能力。