大白菜TuMV抗性的主基因+多基因混合遗传分析

以大白菜抗TuMV品种BP8407的高代自交系和感TuMV品种极早春的高代自交系,抗TuMV品种二青的高代自交系和感TuMV品种春大将的高代自交系配制两个F2群体。以F2群体人工摩擦接种TuMV-C4后的ELISA鉴定的P/N值为抗性鉴定指标,应用P1、P2、F1、F2 4个世代的数量性状主基因+多基因混合遗传分析方法,分析了大白菜TuMV抗性的遗传规律。结果表明：大白菜TuMV的抗性由2对主效基因控制,遗传模型分别为E-1、E-0,主基因遗传率分别为86.51%、77.64%。因此,大白菜对TuMV-C4抗性符合2对主基因+多基因的遗传模式,抗性遗传以主基因为主。     

豆科与禾本科绿肥饲草作物混播增肥及改土效果研究

采用四因素单形重心混料设计,对豆科与禾本科绿肥作物混播增肥改土效果及其混播技术进行研究,结果表明:箭筈豌豆、毛苕子、谷子混播为最佳混播方式,其用种量为箭筈豌豆75.0kg/hm2、毛苕子30kg/hm2、谷子20kg/hm2,在小麦扬花期撒播,鲜草产量可达36138kg/hm2,较单播箭筈豌豆、毛苕子、谷子分别增产34.6%、1.9%、156.3%;鲜根量可达3534kg/hm2,较单播箭筈豌豆、毛苕子、谷子分别增加81.4%、67.2%、28.9%。混播区较单播区土壤有机质含量增加0.148～0.43g/kg,全氮增加-0.04～0.11g/kg,碱解氮增加2.1mg/kg,速效磷增加1mg/kg,全磷基本保持平衡,土壤容重减轻0.01～0.02g/cm3,土壤孔隙度提高0.33%～0.66%。     

Determinants of herbaceous plant species composition on a number of ranches in the north‐western Transvaal

Herbaceous plant species composition was measured on ranches in the Thabazimbi district, Transvaal, to obtain veld composition scores and to quantify the relations between such scores and certain determinants considered important in influencing species composition. Determinants investigated were mean annual rainfall and herbivory (stocking rate). The survey was undertaken on seven game and cattle ranches in Combretum apiculatum woodland of the Mixed Bushveld (Acocks 18) of the north‐western Transvaal. Rainfall for the season preceding the vegetation survey and bulk and selective grazer stocking rates had a significant effect on veld composition scores. The recommended agricultural grazer stocking rate for the survey area is 12.5 LSU 100 ha"¹ a"¹. Under the present conditions and in view of the findings of this survey, it is suggested that a grazer stocking rate of 6.25 LSU 100 ha^?1 a^?1 be implemented.     

Mixed Forests as a Part of Sustainable Forestry in Southern Sweden

Abstract

We review and discuss the applicability of mixed stands in the context of sustainable forestry in southern Sweden. This is done from a silvicultural perspective regarding aspects such as regeneration, pre-commer-cial thinnings, production, economy, damage and policy implications. The paper is based on literature reviews and on studies performed in southern Sweden or under comparable conditions. After considering the underlying mechanisms, we find that it is possible to establish a mixed stand in the regeneration phase and sometimes even to a lower cost compared to monocultures. To keep the mixture, or to create it, with pre-commercial thinnings is, however, often more expensive. The reviewed studies, together with a new simulation, show that the effect on productivity of mixed stands compared to monocultures is minor. Some positive effects on damage (i.e., decreased levels) in mixed stands have been found. The economy and the policy implications of mixed stand management were found to be dependent on the specific stand and situations. A general finding was that research and knowledge of managing mixed stands, as compared to monocultures, are limited, which in turn could limit the applicability of mixed stand management.     

江苏里下河地区鸭鱼共养模式研究

[目的]探讨江苏里下河地区半放养情况下鸭鱼共生比例关系。[方法]通过鸭鱼共养试验测定鸭日排粪量和鱼塘中鸭粪的施肥量,并观测正常养鸭情况下河塘水质情况和鱼的生长情况。[结果]每只鸭每天排出153g新鲜粪。鸭粪中干物质含量为44．83％,全氮含量为1．67％,全磷含量为0．92％,全钾含量为1．62％。采用鸭鱼共养模式可以提高江苏里下河地区养殖的综合效益。[结论]鸭鱼共养模式在江苏里下河地区具有较高的推广价值。     

Snow damages on trees of an uneven age in mixed broadleaf forests:effects of topographical conditions and tree characteristics

Snow damage on natural stands is an important problem concerning mountainous forest management.In the present research,the frequency and intensity of heavy snow damage on natural stands and the relationship of damages with characteristics of trees,stand and topography were studied in mountainous forests of northern Iran.A systematic sampling design was applied to the study area(140 ha),with 122 circular plots.The grid dimension was100 m and each plot area was 1000 m^2.The four types of snow damage to trees include:crown damage(8.6%),stem breakage(5.4%),uprooting(3.2%),and bending(1.4%).The frequency of crown damage grew with an increase inthe diameter at breast height(DBH),while the frequency of stem breakage,uprooting and bending decreased with an increase the DBH.The frequency of crown damage,stem breakage,and total damages was related to tree species(p<0.01).Not all tree species were equally susceptible to snow damage.The amount of damage grew with increasing elevation and slope angle and decreased with increasing soil depth.Young trees(DBH<25 cm)were more susceptible to snow damage than other trees.Snow damage decreased by as the trees in the stand became more mixed in age.The susceptibility of trees to snow damage increased by height and slenderness coefficient.With adequate silvicultural operation,snow damage can be reduced to a minimum level in these natural forests.     

Spatial correlation of pit and mound topography with canopy gaps in a virgin mixed beech forest,northern Iran

In a reserved forest parcel in a virgin eastern Hyrcanian mixed beech forest,80 ha was surveyed to determine the pit and mound topography,canopy gaps and dead trees.The aim was to investigate the spatial patterns and correlation of pit and mound features with canopy gaps.Seventy-five canopy gaps and 61 pit and mound features were identified.The univariate first order nearest neighbor(R_CE)and bivariate second order test(Ripley’s K)statistic were applied.R_CE statistics highlighted a general aggregation pattern for canopy gaps and pits and mounds,while pits and mounds alone were more clumped.Distances between canopy gaps were 130 m average,whereas distances between pit and mound features and dead trees were 60 and 78 m,respectively.Spatial positive correlation of canopy gaps with pits and mounds were observed with all distances.The result of spatial correlations between canopy gaps with pits and mounds confirmed that windthrows cause micro successions in fallen tree ecosystem-scale correlated with gap phase dynamics in the forest community-scale.     

野生大豆与青贮玉米混作对饲草产量及品质的影响

通过在辽宁地区对2个野生大豆品系与青贮玉米进行混作栽培,研究其对饲草产量和营养成分的影响。结果表明:野生大豆与青贮玉米混作可显著提高饲草产量,二者混作收获物青贮后营养成分较玉米单播均有所增加,野生大豆品系LYD140116与青贮玉米在混播密度6.75万株/hm2条件下,饲草产量和品质可达较佳水平。     

青海水、旱地甜高粱与豆科混播及其刈割对草产量的影响

为探索青海水、旱地覆膜种植甜高粱（Sorghum dochna）的增产栽培技术,将2个甜高粱品种‘九甜杂3号’和‘吉甜5号’与3个豆科品种‘草原224’,‘西牧333’和‘1741’分别在水地和旱地进行混播、刈割试验。结果表明：不同海拔生态区不同品种各性状差异显著,综合表现为水地优于旱地;在旱地与豆科混播对甜高粱‘九甜杂3号’和‘吉甜5号’的生长具有明显促进作用,‘吉甜5号’不刈割混播的鲜草产量比单播增加0.42%~21.44%,干草产量增加14.63%~32.24%;‘九甜杂3号’不刈割混播比单播干草产量增加16.74%~43.30%。生长中期刈割对‘九甜杂3号’影响显著,其水地和旱地鲜草产量分别增加9.57%和9.91%。‘九甜杂3号’适宜与豆科品种‘草原224’混播,在生长中期刈割1次,两茬鲜草产量高达147.33 t·hm^-2和112.40 t·hm^-2;‘吉甜5号’适宜与‘西牧333’混播且不刈割,两者鲜草产量达129.55 t·hm^-2和104.01 t·hm^-2,干草产量达29.57 t·hm^-2和22.15 t·hm^-2。因此,甜高粱品种与豆科植物的混播及刈割能够增加其草产量,这对生产实践有着一定的指导意义。     

Management targets for continuously stocked mixed oat × annual ryegrass pasture in a no-till integrated crop–livestock system

Feeding livestock with cover crops can improve the efficiency and sustainability of integrated crop–livestock systems under no-till. However, no-till systems are based on permanent soil cover by organic material, so grazing livestock can compete for soil cover. Hence, managing stocking rates during the grazing period of the cultivated forage species is a key factor to assure enough herbage mass for maintaining long-term sustainable no-till systems. In this context, the objective of this study was to determine sward management targets for a continuously stocked mixed oat (Avena strigosa) × annual ryegrass (Lolium multiflorum) pasture in rotation with soybean in a no-till integrated crop–livestock system to determine the optimum balance between animal production and herbage mass for soil cover. The effects of sward height management on animal performance and herbage mass covers were evaluated. Treatments corresponded to four sward heights: 10, 20, 30 and 40 cm, maintained throughout the experimental period through continuous stocking and variable stocking rate, plus a no-grazing control area. Treatments were arranged in a randomized complete block design with three replications. Herbage mass and animal performance increased linearly with sward height, but weight gain per hectare decreased. Grazing efficiency fitted to a quadratic regression and conversion efficiency a logarithmic model. Equilibrium between grazing and conversion efficiencies was reached on swards managed at 20 cm, indicating that this sward height provided enough herbage mass to allow both animal performance and no-till crop demand for soil cover.