Forage production and nutritive value of Dactylis glomerata and Trifolium subterraneum mixtures under different shading treatments

Production and nutritive value of forage in silvopastural systems can be improved by introducing shade‐ tolerant grass and legume species in appropriate mixtures. The management of these systems can present a challenge regarding the selection of the proper grass and legume species as well as the maintenance of the optimum balance between the two species in the grass–legume stand. The objectives of the present study were to evaluate the performance of pure stands and mixtures (75:25, 50:50, 25:75) of Dactylis glomerata:Trifolium subterraneum under full sun, 60% shade and 90% shade. Dry matter production of D. glomerata was not affected by shading, while that of T. subterraneum was drastically reduced. Shading increased the crude protein (CP) and acid detergent lignin content, but did not affect the acid detergent fibre and neutral detergent fibre content. The dry matter production of the 75:25 and 25:75 mixtures was higher compared to the one of the 50:50 mixture, while the CP content of the 75:25 mixture was the highest under moderate shading. However, relative yield, aggressivity index and competitive balance index indicated higher competitive ability for D. glomerata compared with T. subterraneum especially under shade. Therefore, the 25:75 mixture is suggested as the most suitable under moderate shade (60%), to perpetuate the stand and avoid the frequent re‐sowing of T. subterraneum.     

Effects of water regime,nitrogen fertilization,and rice plant density on growth and reproduction of lowland weed Echinochloa crus-galli

Direct-seeded rice systems are increasing in Asia as farmers respond to the high labor cost and shortage of water. Echinochloa crus-galli is one of the most problematic and competitive weeds in direct-seeded rice systems. Because of concerns about excessive herbicide use, there is an interest in developing cultural weed management strategies. However, the design of such strategies requires a better understanding of the weed response to crop density, nutrition, and water regime. A study was therefore conducted in pots to determine the effect of water (flooded and aerobic), nitrogen (N) fertilization (0, 100, and 200 kg N ha⁻¹), and rice density [0, 4 rice plants (≈20 kg seed ha⁻¹), and 16 rice plants (≈80 kg seed ha⁻¹)] on the growth and reproduction of E. crus-galli. When grown alone, the growth and seed production of E. crus-galli were higher in flooded conditions than in aerobic conditions. However, no such differences were observed when E. crus-galli was grown with rice interference. E. crus-galli growth and seed production increased with increases in N rate. Irrespective of water regime and N rate, the growth and seed production of E. crus-galli declined with increases in rice density. At 100 kg N ha⁻¹, for example, E. crus-galli shoot biomass and seed production decreased by 84–86% and 82–87%, respectively, when grown with 16 rice plants compared with its growth without rice interference. The results suggest that growth and seed production of E. crus-galli can be greatly reduced by increasing rice seeding rate. However, there is a need to involve other weed management strategies to achieve complete control of E. crus-galli and other weed species.     

洽草、草地早熟禾与草坪杂草竞争能力的比较研究

本文在2011年6月-10月期间利用田间试验方法研究了洽草、草地早熟禾与草坪重要杂草-早开堇菜的种间竞争季节动态.结果表明：（1）早开堇菜的生物量、分枝数、有性繁殖能力在与两种草坪草竞争中均受到显著抑制,草地早熟禾对其抑制强度高于洽草;（2）在竞争中洽草的生物量、分蘖数显著增加,取得比较明显的竞争优势,草地早熟禾的株高、地上生物量显著升高,但根系以及分蘖能力受到早开堇菜显著抑制;（3）早开堇菜趋于增加地下部分竞争能力,而洽草和草地早熟禾更趋向于增强地上部分的竞争能力.     

Ungulate browsing on conifers during summer as revealed by DNA

Young trees are particularly vulnerable to browsing by ungulates, since most, or all, of their canopies are within browsing height. In tree species with strong apical dominance, browsing may also affect the structural development of the tree, causing impaired timber quality. Across Sweden, ungulate communities comprise multiple coexisting species, making it a challenge to determine which herbivore species have caused the browsing damages. However, correct identification of the culprits is pivotal for the appropriate management actions to be undertaken. In central Sweden, forest plantation owners recently reported a perceived increase in browsing damages on conifers, primarily Scots pine (Pinus sylvestris). Concurrent with this increase in browsing damages, they noticed an increase in the population of red deer in the area, leading them to suspect that the red deer (Cervus elaphus) were the primary browsers responsible for the damages. Browsed twig samples were sent to us so that we could identify the responsible browsing species using DNA. We discovered that 73.7% of the damages were actually attributable to moose (Alces alces) with 24.7% caused by red deer and 1.5% by fallow deer (Cervus dama). DNA diagnostics can thus yield important information regarding multispecies assemblages enabling managers to correctly identify the relative contributions of different species to browsing damages.     

Designing for and Analyzing Results from Field Experiments

SUMMARY

Some of the topics covered are statistical design axioms, plot technique, experiment design selection, block experiment designs, row-column experiment designs, unreplicated or screening experiment designs, exploratory model selection, multi-site/year trials, and parsimonious experiment designs. In line with the axiom “design for the experiment, do not experiment for the design,” two simple methods for constructing block experiment designs are described. In addition, a software toolkit for constructing optimal or near-optimal randomized plans of experiment designs for many situations is discussed. The effect of response model selection is illustrated with examples. Suggestions for increasing the efficiency of plant-breeding programs are given. Augmented and parsimonious experiment designs can be utilized to increase the efficiency of plant-breeding programs. Some remarks on the construction of these designs are given.     

Effects of Population Density of Bolboschoenus planiculmis on the Absorption and Accumulation of Cotton Nutrients

[Objective] The aim of this study is to clarify the competition of the absorption and accumulation of nutrients in cotton by the Bolboschoenus planiculmis (F. Schmidt) T. V. Egorova. [Method] In this experiment, the population densities of B. planiculmis were set at 0, 20, 40, 60, 80, 100 plant·m^－2. The contents of phosphorus, potassium, nitrate nitrogen, soluble sugar and soluble protein in cotton seedling stage, bud stage and flowering and boll stage were detected to study the effect of population density of B. planiculmis on the nutrient absorption and accumulation of cotton. [Result] At the cotton seedling stage, when the population density of B. planiculmis was 20 plants·m^－2, the soluble protein content of cotton leaves increased significiantly (P＜0.05) compared with the CK, but there was no significant difference in other indicators. However, the higher population density of B. planiculmis could reduce the soluble protein content of cotton leaves and increase the soluble sugar content of cotton leaves. At the cotton bud stage, when the population density of B. planiculmis was lower than 40 plants·m^－2, the phosphorus content in cotton leaves increased significantly. At the cotton boll stage, the population density of all B. planiculmis populations could reduce the content of potassium and soluble sugar in cotton leaves. When the population density of B. planiculmis was 20 plants·m^－2, no significant effects were found on cotton yield. But under other population densities, the cotton yield was significantly reduced. [Conclusion] When the population density of B. planiculmis was higher than 20 plants·m^－2, significant effects were found on the absorption and accumulation of cotton nutrients and cotton yield.     

基于竞争指数的杉木林分生长可视化模拟研究

以我国南方速生丰产林——杉木纯林为研究对象,采用改进过的Hegyi的简单竞争指数模型对杉木纯林间的竞争强度进行定量分析,并建立单木生长模型,再通过径阶模型将其应用于全林分,将单木生长模型研究扩展到全林分生长模型研究。同时,通过可视化模拟技术,为更加逼真的恢复和重建林分空间结构提供理论依据。     

旱直播稻抑草潜力的评价

利用旱直播稻自身的竞争及化感作用,评价旱直播稻品种（品系）对杂草的抑制作用。采用田间小区试验方法,评价旱直播稻对杂草的竞争能力和耐受能力。通过测定旱直播稻特征化感次生物质含量计算出的化感指数来评价其化感潜力;在旱直播稻播种后45 d,杂草生物量与旱直播稻的生物量成显著负相关、与相对竞争强度成显著的正相关。旱稻品系‘HF04’和‘HF011’对杂草的抑制作用最强,前者抑草能力强表现在竞争力,后者抑草能力强表现在耐受杂草竞争力和化感作用。     

Influence of plant host species on intraspecific competition during infection by Aspergillus flavus

Compositions of Aspergillus flavus populations determine the extent to which crops become contaminated with aflatoxins. In the current study, influences of diverse crop hosts on competition among A. flavus isolates were quantified with pyrosequencing. Maize, cotton, soyabean and sorghum supported different levels of sporulation, but intraspecific differences in sporulation were not detected on any host. However, hosts differentially influenced competition during infection, allowing greater sporulation by some isolates and increased host tissue invasion by others. Furthermore, competitive interactions during host invasion did not predict isolate success during sporulation. Isolates were similarly competitive on maize and sorghum, the two most closely related hosts. Host‐specific influences on intraspecific competition may dictate compositions of A. flavus populations and, as a result, the severity of aflatoxin contamination. Host factors should be considered when designing and implementing aflatoxin management strategies including biocontrol with atoxigenic strains.     

转抗虫抗草甘膦除草剂基因(Cry1Ac+EPSPS)棉的检测技术与生存竞争能力研究——基于草甘膦压力和对靶标害虫不防治环境下

此研究为国家转抗虫抗草甘膦除草剂基因(Cry1Ac+EPSPS)棉环境安全评价技术建立而设。在草甘膦压力和对靶标害虫不防治环境下的检测技术,以杂交抗虫棉赣棉杂1号和非转基因棉赣棉11号为2个对照,来检测评价转抗虫抗草甘膦除草剂基因(Cry1Ac+EPSPS)棉的生存竞争能力。结果:转Cry1Ac+EPSPS棉与两个对照相比不显示抗虫优势;株高增长无竞争力;覆盖度有不显著的弱竞争力;单株成铃、单铃籽棉重、单铃皮棉重、衣分率、脱落率、籽棉产量、皮棉产量与赣棉杂1号比呈现显著或极显著的负竞争优势,与赣棉11号比无竞争优势;果枝层数前期与两对照相比有极显著的负竞争优势,后期与赣棉杂1号比无竞争优势,与赣棉11号比有显著的负竞争优势。结论:转Cry1Ac+EPSPS棉推广种植可行性较差。本项检测技术和评价方法有较好的适用性。