Facilitation of an Exotic Grass Through Nitrogen Enrichment by an Exotic Legume

Invasive species control requires understanding the mechanisms behind their establishment and their interactions with other species. One potential ecosystem alteration influencing the establishment and spread of invasive species is anthropogenic nitrogen enrichment, from sources like introduced or invasive nitrogen (N)-fixing legumes, which can alter competition between native, non-native, and invasive plants. Kentucky bluegrass (Poa pratensis) and N-fixing yellow sweet clover (Melilotus officinalis) are exotic to the Great Plains and are currently invading and degrading native rangelands by altering ecosystem processes and displacing native plants. Therefore, we investigated how N enrichment from yellow sweet clover affects the aboveground biomass production of Kentucky bluegrass and western wheatgrass (Pascopyrum smithii), a native cool-season grass, the ranges of which overlap in the northern Great Plains. In a controlled greenhouse environment, we conditioned experimental pots by growing yellow sweet clover and terminating each plant after 8 wk. Conditioned soils contained ≈ 340% more plant-available N than untreated soils 2 wk after yellow sweet clover death. We then grew Kentucky bluegrass and western wheatgrass transplant seedlings in interspecific and intraspecific pairs in pots conditioned either with or without yellow sweet clover for 12 wk. Aboveground biomass production of both Kentucky bluegrass and western wheatgrass grown in interspecific and intraspecific pairs increased in conditioned soils. However, when grown together in conditioned pots, the increase in Kentucky bluegrass biomass relative to untreated pots (520%) was double that of the increase in western wheatgrass biomass (260%). Our results reveal that Kentucky bluegrass can use increased soil N to produce proportionally more aboveground biomass than western wheatgrass, a native grass competitor. Thus, our results suggest yellow sweet clover and other sources of N enrichment may facilitate the invasion of Kentucky bluegrass.     

党的先进性建设如何借鉴国际共产主义运动的基本经验教训

前苏联及东欧共产党丧失执政地位使国际共产主义运动遭受重大挫折的原因有很多，最重要的因素是苏东共产党蜕化变质。没有按照党的先进性来建设党，丧失了党的思想、理论、阶级基础、群众基础、前进方向的先进性，从而失去了它作为无产阶级先锋队的作用，削弱乃至丧失了执政能力，最终葬送了社会主义事业也葬送了党的自身。国际共产主义的经验教训对中国共产党人在全党开展先进性建设的启示是深刻而巨大的：在新的形势下必须坚持党在指导思想上与时俱进；必须从严治党，建立党的先进性建设长效机制；必须加强党的执政能力建设。巩固党的执政基础；必须加大反腐败力度。永葆党的先进性。     

草坪杂草入侵及其竞争效应

以华中农业大学校园的建植草坪为研究对象,以机械布点方式进行样地布设。在所设置的85块样地中进行物种名录调查与统计,并对其中不同光照条件、建植年限及人工管理水平等17块典型样地进行物种特征值调查与计算,以物种重要值来反映该物种在群落中的地位与优势程度。结果表明,在所建植的草坪内入侵植物达141种,隶属39科,其中菊科、蝶形花科、伞形科、石竹科等杂草通过入侵、定居、生长和繁殖,成为优势物种。入侵物种的分布及其竞争能力受光照条件、土壤质地、建植草坪草物种特性及人工管理的影响。管理技术措施,如遮荫、松土、施肥、灌溉及去除杂草是影响其竞争能力的最直接因素。     

Competition model for international comparisons of livestock

Interbull has been responsible for comparing dairy bulls across countries since the mid‐1980s. The current methodology is called MACE (multiple across country evaluations) which has been in use since 1995. Now that genomic data are being utilized in many countries, this has led to two serious problems. The first is that of preselection of young bulls such that the young animals are no longer a random sample of progeny from a sire by dam mating pair. Secondly, some countries are becoming less willing to share genomic data with Interbull. Both issues raise concern over the future of Interbull and international comparisons. This paper suggests a competition model as a potential replacement for MACE. The competition model makes pairwise comparisons between all pairs of bulls within a country and combines these differences across countries through bulls that are used in more than one country. Pedigree information is ignored as are all genomic data because bulls are treated as fixed. The model produces one international ranking of bulls averaging out any genotype by environment interactions which may exist. The competition model is illustrated by a small example. The limitations and advantages of the competition model are discussed.     

采煤沉陷区苦草的生物学特性及其竞争机制

采煤活动所致的动态沉陷湿地具有动态性、高潜水位和生态脆弱性等特点,探明此类人工重构湿地的水生植物群落的生物学特性及其竞争机制,有助于为采煤沉陷区湿地水生植物群落修复提供科学依据。本研究以淮南潘集区人工构建的苦草群落(Ass. Vallisneria natans)为例,采用样方调查法,研究苦草的生物学特性及其与其他水生植物的竞争机制。结果表明,1)沉陷区苦草的生物学特性与浅水湖泊较一致。主要表现在苦草的繁殖方式、传粉方式、生活史方面,但研究区苦草以有性繁殖为主。2)沉陷区苦草能与以种子萌发形成的水烛群丛(Ass. Typha angustifolia)共生,但生物量低;在与形成两年以上的水烛群丛竞争中处于劣势,在水烛群丛盖度达到90%时苦草逐渐消失。3)沉陷区苦草在与浮叶植物莕菜群丛(Ass. Nymphoides peltatum)、苹群丛(Ass. Marsilea quadrifolia)竞争中处于弱势,其盖度、株高、生物量等指标都明显下降。4)沉陷区苦草在与沉水植物竹叶眼子菜群丛(Ass. Potamogeton malaianus)竞争中处于劣势,苦草与沉水植物黑藻群丛(Ass. Hydrilla verticillata)、狐尾藻群丛(Ass. Myriophyllum verticillatum)、大茨藻群丛(Ass. Najas marina)、金鱼藻群丛(Ass. Ceratophyllum demersum)占据不同水层空间,种间竞争不强烈,能较好地共存。总之,苦草较之于相似生长型的植物具有较明显的竞争优势,对于具有不同生活型,尤其是挺水植物和浮叶植物,处于竞争劣势。     

播种方式和行距对燕麦/饲用豌豆混播草地生产性能及种间关系的影响

为筛选出适宜于青藏高原高寒地区种植推广的播种方式及播种行距,本研究以燕麦(Avena sativa)和饲用豌豆(Pisum sativum)为试验材料,探求其在混播、间作及不同行距下的生产性能及种间竞争关系。结果表明：混播处理生产性能优于间作处理,30 cm处理优于其他行距。混播草地土地当量比均大于1,具有混播优势,混播草地中燕麦与饲用豌豆的种间相容性较好,两者间促进作用大于竞争作用,行距为30 cm与25 cm时,燕麦的竞争能力大于饲用豌豆。综合评价显示,青藏高原高寒地区燕麦/饲用豌豆混播行距30 cm时效果最佳,干草产量最高,适于建植应用。     

The influences of reseeding date and mowing prior to reseeding on establishment of alfalfa in Leymus chinensis meadows北大核心CSCD

This research studied the effects of sowing date and cutting prior to sowing on establishment of the leguminous forage,alfalfa（Medicago sativa）,in a lightly degraded Leymus chinensis meadow and investigated the sowing date×cutting interaction. The factorial experiment comprised four sowing dates（May 1,June 1,July 1,August 1）and cutting treatment（cut or uncut）prior to sowing,and evaluated the establishment performance of alfalfa and the ecological mechanisms related to establishment. It was found that soil moisture during emergence of alfalfa was the greatest when sowing occurred on July 1,and clipping prior to sowing significantly decreased the plant height of L. chinensis during emergence and seedling growth of alfalfa. There was a significant sowing date×cutting interaction effect on alfalfa establishment. Clipping prior to sowing significantly increased the emergence percentage of alfalfa through reducing the plant height of L. chinensis and associated above-and below-ground competition,and the seasonal soil moisture change resulted in a 20% higher（P<0. 05）alfalfa emergence rate when sowing occurred on July 1. With cutting,the number of surviving alfalfa seedlings and seedling survival rate were greatest（83 plants· m−2 and 53%,respectively）when sowing occurred on July 1. For later sowing,owing to the shortened growing time,the development and overwintering survival rates of alfalfa seedlings were significantly reduced. Cutting prior to sowing significantly increased the overwintering rate of alfalfa seedlings through improving their development. In the cutting treatment,the number of overwintered alfalfa seedlings（22 plants·m−2）when sowing was on July 1 was significantly higher than for other reseeding dates. In the second year,a botanical composition measurement showed that clipping prior to reseeding significantly increased the alfalfa biomass within the meadow,and the alfalfa biomass was significantly greater than in other treatments when sowing occurred on July 1 after cutting. Cutting prior to sowing also significantly increased the crude protein content of forage. Based on these research results,normal production practice should include cutting when alfalfa is sown into L. chinensis meadow. Combined with cutting,a sowing date around July 1 is the most favorable for the establishment of alfalfa. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

秦川肉牛新品系的培育

产于陕西八百里秦川的秦川牛,千百年来一直是关中农业生产的主要动力和粪肥来源,建国后,通过广大科技工作者的通力合作,协同攻关,运用国际育种先进技术,选出优秀公牛,授配主产区大批秦川母牛,配合其他措施,从而加速了秦川牛的选育,使之很快由役用型转变为肉用型,形成了秦川肉牛新品系。经屠宰测定,其肉用,役用性能不仅大大高于５０年代调查时测定的指标,而且其中一些肉用性能指标与国际著名的肉牛品种相比也毫不逊色,     

Application of Principal Component Analysis on Workable Competition Evaluation

The effective competition is an effective organizational form of the industry in modem market economy. It is a form accompanied with large - scale production and vigor competition. The analysis of effective competition has been the focus that people have paid close attention to it very much all the time. It is a basis of industrial policy, on the basis of the former research, the aufhors bring out 9 indexes according to the actual situation of our country, then take automobile trade as an example, we analyze the automobile trade with principal component.     

鄂尔多斯高原雾冰藜在沙漠-河岸过渡带白刺沙堆上的空间分布特征

采用点格局和标记点格局的方法对雾冰藜Bassia dasyphylla在唐古特白刺Tangutorum nitraria沙堆上的分布情况进行了分析.结果显示:1)雾冰藜在沙堆不同方向分布不均匀,以西北方向分布最多,占整个沙堆的61.49%,其次是西南方向,占26.87%,最少的是东北方向,只有2.09%,反映了雾冰藜对固定、半固定风沙土有较好的适应性,对流动风沙土适应性较差;2)雾冰藜聚集生长的距离范围小于沙堆的平均直径5.54 m,而且在小于这个尺度范围内雾冰藜与白刺沙堆表现为正相关,说明二者之间有相互吸引的共存关系;3)不同沙堆之间的雾冰藜数量彼此之间没有影响;4)雾冰藜在小尺度范围内表现为聚集分布,说明其种子的扩散一般是集中在植物周围,而不同沙堆间种子的扩散,风起到了重要的传递作用.