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     

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     

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

Antibiotic production in and around particles of plant debris in soil was studied. High yields of an antibiotic, shown by bioassay methods to be similar to gliotoxin, were obtained from wheat straws buried in a normal, unautoclaved; acid podsoc from Wareham Heath which had been inoculated with a strain of Trichoderma viride known to produce gliotoxin in culture media. Only a little of the antibiotic was produced in the soil immediately surrounding the straws. Much less was produced in straws buried in John Innes potting compost and none at all in straws buried in a Kettering loam. In no case was an antibiotic detected in straws from un-inoculated soils.
If, however, the Kettering loam was acidified or, alternatively, the straws themselves were acidified and then buried in untreated Kettering loam, good yields of the antibiotic were obtained from straw extracts. Conversely, when the pH of Wareham Heath soil was raised by addition of calcium hydroxide to the soil no antibiotic activity could be detected in the straws. This suggests that the pH of the soil and of the food substrate has a profound effect on production of an antibiotic, assumed to be gliotoxin, by T. viride. The results obtained suggested that increased production of gliotoxin after autoclaving the straws was due to a decrease in the pH of the straws rather than to a release of nutrients.     

土壤藻研究新进展

土壤藻是指分布在土壤表层、土壤下层及与土壤的形成、演替和土壤组成有关的石生、水-陆生的各种藻类的集合群,在土壤的保水、改良、防风固沙及全球气候变化方面都有明显的生态功能 ,自20世纪80年代以来 ,世界范围内土壤藻的生物技术和微藻代谢生理学得到迅猛的发展。       

THE PRODUCTION OF ANTIBIOTICS IN SOIL

Extracts of the coats of seeds inoculated with Trichoderma viride, Penicillium frequentans or P. gladioli and sown in soil contained antibiotics, identified by paper chromatography as gliotoxin, frequentin and gladiolic acid respectively. Three actinomycetes, Streptoniyces griseus, S. venezuelae and S. nureofaciens failed to produce an antibiotic in the coats of seeds sown in either John Innes potting compost or a calcareous soil.
When uninoculated pea seeds were sown in a soil in which an unintroduced gliotoxin-producing strain of Trichoderma viride was growing vigorously, gliotoxin was detected in the seed coats.     

THE PRODUCTION OF ANTIBIOTICS IN SOIL

Conditions affecting the production of gliotoxin by a strain of Trichoderma viride , known to produce this antibiotic in synthetic culture media, were studied in two types of soil, a highly acid, sandy podsol from Wareham Heath and a less acid garden soil. High yields of an antibiotic substance, which results from bioassays showed to be similar to gliotoxin, were obtained from both inoculated soils when autoclaved and supplemented with organic material. The autoclaved soils behaved differently when unsupplemented; Wareham soil supported production of the antibiotic but little or none was produced in the garden soil. No antibiotic activity could be demonstrated in soil which had not been inoculated with T. viride.
Acidification of unsupplemented garden soil by addition of sulphuric acid had a favourable effect on production of the antibiotic, but raising the pH of Wareham soil by addition of calcium hydroxide also increased the yield. These effects, therefore, cannot be due simply to the change in pH of the soil.
The beneficial effect of autoclaving the soil on production of the antibiotic assumed to be gliotoxin was analysed and separated into three distinct effects, elimination of the microflora, increase in availability of nitrogen compounds and increase in available carbon compounds. The last effect was considered to be of greatest significance.
The antibiotic was produced in normal Wareham soil if supplemented with additional carbon compounds, but not in garden soil unless this had also been acidified before inoculation. A chromatographic method of bioassay used in the later work gave more substantial evidence that the antibiotic produced in the soil was, in fact, gliotoxin.     

土壤水热条件对东北森林土壤表面CO2通量的影响

东北地区森林生态系统因其面积大,碳贮量高而在本地区和我国碳平衡中占有重要的地位.土壤表面CO2通量(RS)作为陆地生态系统向大气圈释放的主要CO2源,其时空变化直接影响到区域碳循环.该研究采用红外气体分析法比较测定我国东北东部次生林区6个典型的森林生态系统的RS及其相关的土壤水热因子,并深入分析土壤水热因子对RS的影响.研究结果表明影响RS的主要环境因子是土壤温度、土壤含水量及其交互作用,但其影响程度因生态系统类型和土壤深度而异.包括这些环境因子的综合RS模型解释了67.5%～90.6%的RS变异.在整个生长季中,不同生态系统类型的土壤温度差异不显著,而土壤湿度的差异显著(α=0.05).蒙古栎(Quercus mongolica)林、红松(Pinus koraiensis)林、落叶松(Larix gmelinii)林、硬阔叶林、杂木林和杨桦(Populus davidiana-Betula platyphylla)林的RS变化范围依次为1.89～5.23 μmol CO2·m-2·s-1,1.09～4.66μmol CO2·m-2·s-1,0.95～3.52 μmol CO2·m-2·s-1,1.13～5.97μmol CO2·m-2·s-1,1.05～6.58 μmol CO2·m-2·s-1和1.11～5.76μmol CO2·m-2·s-1.RS的季节动态主要受土壤水热条件的驱动而呈现单峰曲线,其变化趋势大致与土壤温度的变化相吻合.Q10从小到大依次为蒙古栎林2.32,落叶松林2.57,红松林2.76,硬阔叶林2.94,杨桦林3.54和杂木林3.55.Q10随土壤湿度的升高而增大;但超过一定的阈值后,土壤湿度对Q10起抑制作用.该研究结果强调对该地区生态系统土壤表面CO2通量的估测应同时考虑土壤水热条件的综合效应.