Water limitation and plant inter-specific competition reduce rhizosphere-induced C decomposition and plant N uptake

Plants can affect soil organic matter decomposition and mineralization through litter inputs, but also more directly through root-microbial interactions (rhizosphere effects). Depending on resource availability and plant species identity, these rhizosphere effects can be positive or negative. To date, studies of rhizosphere effects have been limited to plant species grown individually. It is unclear how belowground resources and inter-specific interactions among plants may influence rhizosphere effects on soil C decomposition and plant N uptake. In this study, we tested the simple and interactive effects of plant diversity and water availability on rhizosphere-mediated soil C decomposition and plant N uptake. The study was conducted in the greenhouse with five semi-arid grassland species (monocultures and mixtures of all five species) and two water levels (15 and 20% gravimetric soil moisture content). We hypothesized that microbial decomposition and N release would be less in the low compared to high water treatment and less in mixtures compared to monocultures. Rhizosphere effects on soil C decomposition were both positive and negative among the five species when grown in monoculture, although negative effects prevailed by the end of the experiment. When grown in mixture, rhizosphere effects reduced soil C decomposition and plant N uptake compared to monocultures, but only at the low-water level. Our results suggest that when water availability is low, plant species complementarity and selection effects on water and N use can decrease soil C decomposition through rhizosphere effects. Although complementarity and selection effects can increase plant N uptake efficiency, plant N uptake in the mixtures was still lower than expected, most likely because rhizosphere effects reduced N supply in the mixtures more than in the monocultures. Our results indicate that rhizosphere effects on C and N cycling depend on water availability and inter-specific plant interactions. Negative rhizosphere effects on soil C decomposition and N supply in mixtures relative to monocultures of the component species could ultimately increase soil C storage and possibly influence how plant communities in semi-arid grasslands respond to global climate change.     

《黄金时代》传播、接受史研究

《黄金时代》自刊出后就受到评论界和学术界的广泛关注,对它的研究经历了不同的阶段。文中通过对《黄金时代》出版发行、传播、接受过程的梳理,进而研究其传播中受阻的现象。从而发现小说中关于“性”描写和知青小说书写两方面的开创性和超越性意义,并分析与此主题相关的研究热点,最后通过近十年的研究现状的梳理,对研究的走向作出预测。     

四川乳肉兼用牛群体的泌乳性能研究

以2213头成年乳肉兼用牛产奶量纪录和558个乳样的乳脂测定结果为基础材料,对四川乳肉兼用牛的泌乳性能进行了初步分析。结果表明,四川乳肉兼用牛的各胎次泌乳量为3889．4±1580．6 kg,泌乳期为283．5±35．2 d,乳脂率为4．509％±0．58％。其中第1胎至第5胎305 d平均泌乳量分别为3395．4±740．81 kg,4123．4±1038．8 kg,5260．7±1728．9 kg, 5149．6±1988．4 kg和4896．3±1979．5 kg;第1胎至第5胎平均乳脂率分别为4．403±0．32％,4．561±0．63％,4．561±0．72％,4．470±0．35％和4．497±0．73％,第5胎及5胎以上个体305 d平均产奶量为4602．3±1478．4 kg,表明四川乳肉兼用牛具有较好的泌乳性能。     

A Game Analysis of Credit System and Mortgage Backed Securitization

This essay illustrates the importance of credit to the supply of asset pool and the operation of MBS from the accept and the basic operation process of MBS. According to our country's conditions, this essay states from two sides. Through the game of housing consumer and commercial, for one thing, housing consumer desides applying for loan or not,and commercial bank desides granting loan or not; for another ,housing consumer selects prepaying loan,paying loan on time or branking contract,and commercial bank selects lawsuiting or not. Through the game analysis of two sides , it discusses relations between the loan of bank and the development of credit system,and give us some suggestions in order to the development of MBS.     

大白菜细胞核雄性不育两用系的利用途径探讨

不同来源的大白菜核不育两用系存在不同的遗传机制,其不育株与可育株都各略占50％并存。在利用上,50％不育株可作母本用于配制F_1杂种和核基因互作雄性不育系;50％可育株可用作F_1杂种父本、质核复合雄性不育保持系和核基因互作雄性不育临保系,同时自交还可快速选育自交系。在优势育种上,大白菜核不育两用系具有一定开发潜力和应用前景。     

Game Analysis of Housing Consumer and Commercial

According to our country's conditions, consumer selects prepaying loan,paying loan on time or branking contract,and commercial bank selects lawsuiting or not. Through the game analysis of two sides,it discusses relations between the loan of bank and the development of credit system,and give us some suggestions in order to the development of MBS in our country.     

自优化模拟技术在水库兴利调度中的应用

自优化模拟在单库及多库兴利调度方面较一般模拟方法效果理想，且模型易于编程求解，有较好的实用性。采用自优化模拟技术，针对某地区水库部分入流(有外流域调水)可以调控的特殊情况，建立基于自优化模拟的逆时序模拟模型，确定了该地区水库运用方式和水库兴利调度图，调度结果较一般模拟方法要好，显示自优化模拟技术在水库兴利调度中较好的应用性。     

广西山茶属木材解剖分子研究

对采自广西的9个组47种山茶属木材解剖分子进行了测定研究,研究表明,山茶属木材的各种解剖分子显示长度长、直径小、胞壁薄的特点,属于比较原始的种系。山茶属解剖分子特征还表明,其木材密度大,各种力学强度也大,是很好的纤维工业用原料和农具柄及工艺用材。     

毛泽东与实学传统

实事求是、经世致用、史学经世是中国传统实学的重要组成部分 ,也是毛泽东与实学传统间关系最为密切的三个方面。毛泽东自青少年时代起就接受了实学传统的积极影响 ,完成世界观转变后 ,他又运用马克思主义的科学态度自觉地批判继承了这一传统 ,并实现了马克思主义的超越。毛泽东不愧为站在现代社会制高点上正确处理传统文化的一位大师     

加入WTO后政府出版物的整合

加入WTO后，政府信息将全面对国内外公开。作者论述了政府出版物的定义和分类，并分别对印刷体、网站、数据库为载体的政府出版物的现状、特点进行描述。同时对政府出版物的整合提出两个方案：(1)中国政府出版物贮藏计划；通过立法保证全国范围内若干个图书馆承担收藏、整理、揭示政府出版物的任务，向所有公众开放。(2)政府出版物门户站点：建立一个全国范围内的政府信息交换、收藏、检索的网站平台，目的是使“中国为人所知”。