西双版纳不同热带森林下土壤铵态氮和硝态氨动态研究

用顶盖埋管法(Close-Top Tube Incubations)就西双版纳3种热带森林（热带季节雨林、片断热带雨林、橡胶林）研究了土壤铵态氮（NH     

羊草草原土壤微生物的分布及其与土壤因子间的关系

 本文较系统地研究了东北羊草草原土壤微生物的分布规律和环境因子对微生物分布的制约作用。结果表明：微生物的数量、生理群的数量及微生物总生物量在羊草和杂草群落土壤生境中均最高,而碱茅和碱蓬群落生境中最低,隐子草群落生境居中。土壤全磷、全氮、全钾、pH和活性有机质对微生物有较大的直接作用,通径系数为6.15—2.02。全氮—全磷、活性有机质-全磷、pH-全磷、pH-全钾、全钾—全磷、活性有机质—全氮、活性有机质—全钾和有机质—全氮之间的间接作用对微生物影响最明显,作用系数为5.94—2.90,其余因素的作用相对不显著。     

THE PRODUCTION OF ANTIBIOTICS IN SOIL V. BREAKDOWN OF GRISEOFULVIN IN SOIL

When griseofulvin (I; R = Cl, R '= OCH₃), a chlorine-containing antibiotic produced by Penicillium nigricans , was added to fresh garden loam, after an initial lag it disappeared rapidly. When further griseofulvin was added it was inactivated from the start and at rates which increased with each successive addition, suggesting that it was degraded biologically. The numbers of one organism, a Pseudomonas sp., increased in the soil steadily after adding griseofulvin.
When a little soil was added to a solution (pH 7·0) containing inorganic salts and griseofulvin as the sole carbon source, bioassays showed that the griseofulvin disappeared within 5 days. An organism isolated from the broth was identified as the Pseudomonas sp. thought to break down griseofulvin in soil. Griseofulvin also disappeared from a broth at pH 5·0 inoculated with soil, but at this lower pH value a dematiaceous fungus was responsible for its breakdown.
The Pseudomonas sp. also degraded two derivatives of griseofulvin, dechlorogriseofulvin (I; R = H, R'= OCH₃) and the amine (I; R = Cl, R '= NH₂). Cl^– was detected in the solutions after breakdown of griseofulvin by the Pseudomonas ; the amount present agreed well with that calculated on the assumption that all the chlorine in the griseofulvin supplied was liberated as Cl^–. Spectrophotometric examination of the solutions showed no metabolites with the aromatic ring intact, and confirmed the complete breakdown of griseofulvin suggested by the liberation of Cl-.     

高寒草甸土壤生态系统的结构及昆虫群落的某些特性

自1881年达尔文报道蚯蚓对土壤的作用以来,人们对土壤动物的研究做了许多工作,Kevan(1955)和Murphy(1962)先后发表了这方面的专著。70年代初,国际生物学规划(IBP)选择了苔原、草原、森林等典型地区,开展了较为系统的土壤动物调查研究工作。随着人类对土地利用和土壤改良的重视,土壤生态系统的研究正趋向于成为一个专门的研究领域。 土壤动物的研究对象,大多属于土壤昆虫,我国草原土壤昆虫的研究,至今仍属薄弱环     

SOIL SAMPLING FOR WHEAT-BLOSSOM MIDGES

A method of assessing the population of wheat-blossom midges by the recovery of the cocoons from soil is described.
In the dry summer of 1947, considerable numbers of larvae of Sitodiplosis mosellana Géhin were still in the ears at the time of harvesting. Burning the straw immediately after combining may considerably reduce the numbers of midges.
The majority of the larvae are found in the top 3 in. of the soil although a considerable number may be found from 3 to 6 in. Headland infestations may be lighter than the rest of the field.
Cocoons of S. mosellana remain viable in the soil for several years, and 150,000 per acre were recovered in February 1951 from a field which had not had a wheat crop since 1944. At the same time 50,000 Contarinia tritici Kirby cocoons per acre were found in a field which was last under wheat in 1947.
Viable pupae were successfully obtained by soil sampling, and the pupation in the soil and subsequent emergence of the midges can be followed. Thus it is possible also to estimate the numbers of midges that will emerge.
Progress has been made towards predicting outbreaks of these two midges.