Management of permanent set-aside on arable land in Sweden

1. Set-aside fields have been an important element of the European agricultural landscape since the introduction of the set-aside scheme by the European Community. However, countries in the European Community differ in their rules for managing set-aside owing to different priorities.
2. In Sweden, a major goal is to reduce the total use of agricultural pesticides, consequently their use is prohibited in set-aside. The options for weed control are therefore cutting and/or the use of a cover crop.
3. In this study, we describe the course of succession following the abandonment of farmland managed in different ways. The floristic composition was followed over a 10-year period. Temporal trends in community development are described.
4. The experiment began in 1975 on farmland at six localities, distributed from southern to northern Sweden. The management treatments involving the application of fertilizers and cutting were applied to plots sown with a cover crop and to plots in which the succession started from bare ground.
5. We found that competitive interactions between species largely determined the successional course in our study. The competitive success of species was related to the management practices applied but there were also interactions between management and site conditions.
6. We propose that natural succession can be recommended on poor sites in combination with cutting, mainly to prevent the invasion of woody species. On fertile sites a cover crop should be used to suppress perennial weeds, and cutting is recommended mainly to increase species diversity.     

采伐迹地恢复阔叶林与人工栽杉土壤肥力变化差异的初步研究

本文连续3a分析比较了采伐迹地恢复阔叶林和人工种植杉木林土壤肥力变化的差异。结果表明:在人工栽杉3a内,杉木林土壤水分含量和有效水含量下降,土壤干湿交替变化增大,水分物理性状变差,土壤水稳性团聚体含量降低,结构体破坏率增大,而阔叶林则呈上升趋势。杉木林下土壤微生物数量在造林3a内呈不断下降趋势,而阔叶林则呈增加趋势;杉木林土壤氧化还原酶活性弱于阔叶林,水解酶活性强于阔叶林,两种酶系活性在3a内阔叶林增强,杉木林减弱;阔叶林土壤养分在3a内不断提高,杉木林土壤不断下降。     

广藿香扦插繁殖不定根形成的解剖学研究

利用常规石蜡切片法,系统研究了广藿香不定根的起源和发育。观察结果表明：广藿香茎中没有先成根原始体,其不定根属于诱生根类型,起源于靠近维管形成层的初生韧皮部薄壁细胞中,愈伤组织内无不定根生成。本研究揭示了广藿香扦插生根的解剖学特征,从而为该药材在生产中提高扦插育苗成活率提供理论依据和实践指导。     

Anterior dental cutting in the Laetolil hominids and the evolution of the bicuspid P3

The younger Laetolil hominids provide evidence of a unique anterior cutting complex with a chisel-like action occurring between the lingual-distal C face and a transverse ridge on the P₃ perpendicular to it, extending between the subequal cusps. An earlier adaptation to more efficient grinding may have resulted in reduced canine projection and the development of the lingual P₃ cusp, raising the ridge between it and the buccal cusp. This development acted to retain the anterior cutting function by shifting it to the top of the premolar.     

Runoff transport of faecal coliforms and phosphorus released from manure in grass buffer conditions

AIMS: To test the hypothesis that faecal coliform (FC) and phosphorus (P) are transported similarly in surface runoff through the vegetative filter strip after being released from land-applied manure. METHODS AND RESULTS: The Hagerstown soil was packed into boxes that were 10 cm deep, 30 cm wide and 100, 200 or 300 cm long. Grass was grown in boxes prior experiments. Same-length boxes were placed under rainfall simulator and tilted to have with either 2% or 4% slopes. Dairy manure was broadcast on the upper 30-cm section. Rainfall was simulated and runoff samples were collected and analysed for Cl, FC and total phosphorus (TP). Mass recovery, the concentration decrease rate k, and the ratio FC : TP showed that there was a consistent relationship between FC and TP in runoff. Conclusion: The FC and TP transport through simulated vegetated buffer strips were highly correlated. SIGNIFICANCE AND IMPACT OF THE STUDY: As a knowledge base on the effect of the environmental parameters on P transport in vegetated buffer strips is substantially larger than for manure-borne bacteria, the observed similarity may enhance ability to assess the efficiency of the vegetated buffer strips in retention of FC currently used as indicator organisms for manure-borne pathogens.     

胚轴切断法诱导棉株对棉铃虫生长发育的影响

通过室内饲喂棉铃虫的方法,测定了诱导棉株对棉铃虫幼虫发育历期、幼虫体重和肾重的影响。结果表明,不加菌处理和加菌处理的诱导抗性棉株可分别使棉铃虫幼虫发育历期延长０．５和３ｄ,幼虫体重（５龄）降低１１．４５％和１９．６０％,蛹重降低６．５４％和１０．８１％。用诱导棉株叶片饲养８日龄棉铃虫幼虫３天后,菌诱导和无菌诱导分别使棉铃虫的相对生长率降低２２．９％和１７．２％,相对取食量降低２６．１％和２１．４％     

NO和NADPH-黄递酶在绿豆下胚轴不定根发生和发育过程中的变化

研究了一氧化氮(NO)供体普钠(SNP)、一氧化氮清除剂C-PTIO和一氧化氮合酶(NOS)抑制L-NAME对绿豆(Vigna radiataL.)下胚轴插条生根的影响.并对不定根生期间手条基部NO 和NADPH-黄递酶的时空变化进行了检测.所试浓度SNP均明显促进下胚轴不根发生.分别插条切取后24h和36h于其基部维管束之间检测到NADPH-黄递酶(NOS标记酶)阳性反应和NO荧光,根原基也于48h在相同位置出现,并于60h进一步伸长.48~60h期间,NADPH、黄递的阳性反应及NO荧光有增强趋势,并主要分布在不定根分生组织中.L-NAME既减弱NADPH-黄递酶的阳性反应和NO荧光,也延缓不不定根发生;而c-PTIO对NO荧光及不定根生均有抑制作用.上述结果证明:NO在不定根发生及发育过程中有重要作用,而且此过程中的NO很可能由类似的NOS催化产生.     

The role of plant traits and their plasticity in the response of pasture grasses to nutrients and cutting frequency

MethodsMonocultures of the grass species were grown in a fully factorial block design combining plant species, cutting frequency and N supply as factors.ConclusionsVariations in ANPP of species in response to an increase in cutting frequency and a decrease in N supply are controlled by a group of traits, rather than by one individual trait. Incorporating plasticity of the individual traits into these trait combinations was the key to explaining species'' productivity responses, accounting for up to 89 % of the total variability in response to the changes in N supply.