徐州矿区充填复垦土壤特性实验研究

为了研究矿区复垦土壤的特性、环境质量状况,探寻矿区特殊生态环境中的污染物料的时间路径、人工土壤的质量品质,为煤矿塌陷区的充填复垦、环境治理提供依据,采用对复垦场地进行实验研究和数据分析的方法,对不同物料充填复垦场地的土壤特性进行比较分析。结果发现：①土壤环境：从渗透性来说,矸石复垦场地的保水性高于粉煤灰复垦场地,土层的保水性高于充填物料层的保水性;从土壤紧实度来说,粉煤灰充填复垦场地充填物料层的紧实度低于土层的紧实度,但都在适宜作物生长的范围内;比照地的土壤紧实度偏高;粉煤灰充填场地的土壤偏碱性;②土壤品质：粉煤灰充填土壤能够正常种植小麦、稻、草本的植物、蔬菜等;粉煤灰充填场地的土层虽然是沙土,但比较容易板结,不利于水分的渗透,而底层的粉煤灰保水性比较差;煤矸石充填复垦场地表层覆土厚度不均匀,且煤矸石保水保肥性比较差;③充填土壤的适种性和产量分析：粉煤灰回填的土壤适合草本蔬菜类植物的种植,单产与正常产量相当;对于种植稻的田块,保持正常的单产水平;种植小麦的产量受到影响。     

徐州矿区充填复垦场地作物重金属含量研究

为了了解矿区充填复垦土壤重金属污染状况和复垦场地主要作物的重金属含量情况,通过场地采样试验与室内检测相结合的方法,对不同作物不同部位的砷、镉、铬、汞、铅、铜和锌等重金属含量进行了测定,并进行了相关的分析和研究。结果表明:作物在生育阶段不同部位对不同元素的敏感性不同;复垦场地红豆幼苗受重金属的污染较轻,而小麦和水稻则较严重;复垦场地应改变耕作制度,种植红豆或者利用红豆充当先锋作物。     

高潜水位采煤塌陷区重构土壤水分运移规律模拟研究

以江苏省徐州市贾汪矿区为研究区,通过野外采样与室内土柱试验模拟不同土壤重构模式,对固定地下水位不同重构模式下土壤水分运移过程进行了观测。试验设置土柱上层0—50cm为土壤充填,50—80cm为不同表土替代物充填。按照下层50—80cm充填物的不同,设置4组处理,其中处理1为对照组(土壤充填),处理2(粉煤灰充填)、处理3(煤矸石充填)、处理4(煤矸石-粉煤灰混合物充填)为试验组。结果表明:(1)重构土壤上层含水率与下层相比变化明显,底层含水率临近于饱和含水率,变化微小;(2)在不同充填物的分界线处含水率变化明显,充填物类型对土壤水分垂直变化有较大影响;(3)煤矸石、粉煤灰混合物充填重构模式含水率变化规律与土壤充填模式最为一致,且饱和含水率最为接近,具有良好的保水、透气性,是高潜水位采煤塌陷区土地复垦最理想的土壤重构模式。本研究可以为高潜水位采煤塌陷区土地复垦的土壤重构以及盐渍化控制等提供一定的理论依据和技术支撑。     

煤矸石充填复垦地理化特性与重金属分布特征

为研究煤矸石充填复垦地农作物产量达到最佳时的覆土厚度及煤矸石充填复垦地重金属分布状况,该文以新庄孜矿煤矸石充填复垦地作为研究对象,采取室外田间小区试验和室内试验分析方法,选取不同覆土厚度50~60,60~70,70~80,80~90 cm的4类试验地块及对照地块对其土壤理化性质及农作物根系分布、长势产量、重金属元素含量进行调查分析,发现复垦地块各项指标与对照地块差异显著,劣于对照地块;煤矸石充填基质土壤理化性质较差;70~80 cm的厚度是煤矸石充填复垦造地较经济合理的覆土厚度。煤矸石复垦地重金属元素有向上迁移的趋势;复垦土壤及煤矸石基质中Pb、Zn、Cr元素含量处于安全水平;大部分监测的Cu、Ni、Cd元素含量高于淮南土壤背景值,低于中国土壤环境质量标准二级标准,对复垦土壤已构成潜在的威胁性,应予以重视;覆土厚度50~60 cm地块的煤矸石基质中Cu、Ni元素含量处于安全水平,煤矸石基质中Cd元素含量高于淮南土壤土壤背景值,低于中国土壤环境质量标准二级标准,应予以重视。结果表明70~80 cm的厚度是煤矸石充填复垦造地最佳覆土厚度;新庄孜煤矸石充填复垦地重金属有向上迁移的趋势,复垦土壤中重金属含量符合国家二级标准,未出现重金属污染情况,但部分重金属元素含量高于淮南市土壤背景值,应予以重视。     

矿区复垦土壤种植小麦的重金属安全性

为分析矿区充填复垦土壤种植农作物的生态安全性,以中国徐州市柳新矿区复垦场地为例,对照当地农田土壤,对充填场地种植小麦不同部位As、Cd、Cr、Cu、Hg、Pb、Zn 7种重金属元素含量进行检测,分析了Cd、Cr在成熟小麦不同器官中的分布、富集情况,并利用单项污染指数法和综合指数法对小麦籽粒进行了风险评价。结果表明,三场地中Cd 和Hg在未成熟苗中的含量小于成熟茎中的含量,Cr、Cu和Zn则与之相反,Pb和As的含量规律性不太明显;复垦场地小麦未成熟根的重金属含量都小于成熟根中的含量;比照地中除Cr 和Zn之外,其余元素在未成熟根中的含量均大于成熟根的含量;参照粮食污染限量标准,小麦籽粒中Cd和Cr含量均超标。风险评价显示三场地小麦籽粒中Cd、Cr单项污染指数达到轻度至重度水平,综合污染指数处于轻度污染至中度污染水平之间。该研究对矿区粮食安全的监控具有重要的实际应用价值。     

不同复垦工艺土壤物理性状研究

采用实地模拟试验,研究不同复垦机械在不同填充材料下不同的碾压次数对土壤物理性状的影响,并采用winner2000激光颗粒仪对其土壤颗粒组成进行了量测分析,研究不同机械不同填充材料复垦对物理性状的影响。结果表明:(1)经过3次碾压后,各复垦地块土壤容重变化趋势趋于平稳,但从碾压7次到碾压9次这个过程,是复垦过程中的一个敏感碾压区,碾压7次后土壤容重会有明显的上升,且在煤矸石、建筑垃圾和粉煤灰三种填充材料中,粉煤灰充填复垦地块在碾压5次后,容重明显高于煤矸石和建筑垃圾充填地块。(2)自卸汽车复垦过程碾压超过3次,其容重即超过1.5 g cm-3,碾压9次容重达到1.76 g cm-3,使土壤质地板结;履带式推土机碾压7次,其容重仍在1.44 g cm-3以下,适于作物生长。(3)经不同程度的碾压后,履带式复垦地块中,建筑垃圾、粉煤灰和煤矸石充填地块"物理性黏粒"含量的最大值分别为25.29%、26.66%和36.89%;自卸汽车复垦的地块中,建筑垃圾、粉煤灰和煤矸石填充的地块总含量的最大值分别为36.23%、32.11%和51.73%。     

王庄煤矿采煤沉陷区充填复垦现状及改进措施

山西省王庄煤矿主要位于农耕区,采煤导致土地大面积沉陷,耕地数量减少,且质量下降,单产锐减,致使矿群关系恶化。在煤炭开采和洗选加工过程中产生的煤矸石以及电厂发电排放的废渣粉煤灰是王庄煤矿的主要固体废弃物,煤矸石和粉煤灰平地起堆不仅压占了大面积土地,还污染了生态环境。以潞安集团王庄煤矿为例,分析了王庄煤矿采煤沉陷区充填复垦工作现状及不足,并提出了具体改进措施:一是运用化学方法改变土壤的酸碱性,以适于植物生长;二是优化施工工艺,降低对土壤的破坏;三是优化充填工艺,防止煤矸石、粉煤灰中有害物质的迁移及对周围环境造成污染;四是优化充填方法,对作为建设用地的充填地基实施加固处理。     

机械压实过程中复垦土壤紧实度影响因素的模拟分析

机械碾压造成的土壤压实是土地复垦中面临的主要问题之一,影响土壤压实程度的因素很多,除土壤自身的因素以外,还包括压实机械、压实次数以及土层厚度等。该文基于统计学的理论,采用2×5×4的混合试验设计并建立模拟实验区,使用重锤模拟分析了2种压实机械、不同压实次数(1、3、5、7、9次)和不同土层厚度(0~10cm、10~20cm、20~30cm、30~40 cm)上土壤紧实度的变化情况,并在SPSS中进行变量的方差分析和多重比较,试图找到机械压实过程中影响土壤紧实度的因素及其变化水平。结果表明:增加压实机械的承重轮面积能够有效降低对土壤的压实作用;压实机械、土层厚度和压实次数都是影响土壤紧实度的显著性因素且各因素的贡献率(97%)远高于随机误差;自卸汽车在第5次压实之后就已经使上层土壤紧实度达到最大值,而履带式推土机需要压实7次,土地复垦中应尽量选择履带型机械,碾压次数控制在5~7之内;机械压实的过程中,各土层厚度之间土壤紧实度的大小关系并不是一成不变的,中间层次(10~30 cm)的土壤由于同时受到来自上下2个方向的作用力,紧实度相对较高;不同次数的压实对土壤紧实度的影响深度和程度不同,在一定范围内,随着压实次数的增加,单次压实对土壤紧实度的影响逐渐减小。     

高潜水位矿区不同复垦方式下土壤热导率及其影响因素

以东部高潜水位采煤塌陷复垦耕地为研究对象,研究挖深垫浅复垦、充填复垦、预复垦3种复垦方式下土壤热导率的分布及原因。在3种复垦方式典型样地上开挖剖面,分别取0—20,20—40,40—60cm土层土样,经实验分析观测土壤热导率及相关物理指标。结果表明:(1)复垦方式、剖面层次和二者交互作用均是使热导率产生显著差别的因素(p0.01),对土壤热导率总体变异的贡献率分别为86.8%,89.6%,71.9%;(2)土壤热导率随土壤剖面深度增加呈先增加后降低的""型变化趋势;(3)复垦可以显著(p0.05)影响土壤热导率大小,并增加其在不同剖面层次上分布的差异;(4)在含水量和温度差异不大的条件下,土壤容重在1.205~1.593g/cm3时,砂粒含量为影响热导率的主要因素,当土壤容重在1.604~1.813g/cm3时,容重为影响热导率的主要因素。与未塌陷耕地相比,复垦土壤热导率偏低,在土层间分布差异性增加,因此应综合考虑容重和质地,从降低土壤容重的角度入手,改良复垦土壤热导率。     

引黄河泥沙充填复垦采煤沉陷地技术的试验研究

为探寻适合中国东部高潜水位平原矿区的土地复垦新技术,该文选取济宁市北部试验场为研究对象,介绍了引黄河泥沙充填复垦采煤沉陷地的新技术,包括技术工艺流程、复垦后地貌景观、复垦土壤剖面状况、复垦土壤理化性状以及复垦农田生产力。结果表明:1)短距离引黄河泥沙充填复垦技术在济宁市北部试验场得到了成功应用,土地复垦率为100%,耕地面积恢复率达95%,证明了引黄河泥沙充填复垦技术的可行性;2)黄河泥沙充填复垦土壤剖面的保水保肥性能存在一定的不足,复垦农田的表层(0~20 cm)、中层(20~50 cm)和底层(50~80 cm)土壤的含水量、全氮、速效钾、有机质含量以及表层(0~20 cm)土壤的有效磷含量均小于对照农田相应层的含量,且复垦农田土壤全氮和有机质较为缺乏,限制了农作物的生长;3)实地测产发现充填复垦农田的产量只有对照农田的一半左右,说明需要对充填复垦工艺进行革新和复垦土壤进行改良。论文在分析引黄充填技术可行性的基础上,提出了未来需要革新的4个方面:复垦土壤剖面重构的革新、水沙快速分离的充填排水工艺革新、动水条件下高效取沙设备的优选与革新以及远距离管道输沙技术参数优选。引黄河泥沙充填复垦技术对滨黄河流域的河南、山东等省很多矿区的采煤沉陷地都具有推广应用价值。     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Einfluss der düngungsmethoden auf die entwicklung von zuckerrübenkrankheiten

Während neunjähriger (1994-2002) Untersuchungen in der Versuchsanstalt Ba?cyny (Fahlerde, Fall-Gleyboden, ausgebildet aus leichtem Lehmboden) wurde der Befall mit Krankheiten an der Zuckerrübe in Abhängigkeit von der Düngungsmethode bewertet. Folgende Methoden wurden angewendet: A - Mineraldünger, B - Stalldung und Mineraldünger, C - Stroh-, Gründung und Mineraldünger, D - Kompostdünger und Biopräparate (ökologische Düngung). Auf den Objekten A, B, C wurden bei konstanter Phosphor-Kalium-Düngung die Stickstoffgaben von 0 bis 180 kg.ha^?1 differenziert. Auf dem ökologischen Objekt D ohne Mineraldünger wurden statt Stickstoff die Biopräparate P₅₀₀ und P₅₀₁ verabreicht. Der geringste Befall von Krankheiten wurde an der Zuckerrübe auf jenem Objekt festgestellt, das mit Kompost und den Biopräparaten gedüngt worden war. Im Rahmen der konventionellen Düngungsmethoden wurde allgemein die höchste Intensität der Krankheiten an der mit Stroh, Gründung und Mineraldünger gedüngten Zuckerrübe beobachtet. Ausnahmen von dieser Regel bildete das Vorkommen von echtem Mehltau und Keimlingsfäule. Auf den Objekten A, B, C nahm die Intensität der Krankheiten mit der Steigerung der Stickstoffgabe zu. Auch die auf Objekt D verabreichten Biopräparate stimulierten die Entwicklung der Krankheiten. The effect of various fertilization methods on the diseases of sugar beet was estimated on the basis of nine-year studies (1994-2002) conducted in the Experimental Production Farm in Ba?cyny on loess-based, sedimentary-gley, light-clay soil. The following fertilization methods were applied: A - mineral fertilization, B - mineral and manure fertilization, C - straw, green manure and mineral fertilization, D - ecological compost and biodynamic preparations fertilization. In the objects A, B and C fertilized with phosphorus and potassium, various doses of nitrogen ranging from 0 to 180 kg/ha^?1 were used. In the ecological object D, where mineral fertilization was not used, biodynamic preparations P₅₀₀ and P₅₀₁ were applied instead of nitrogen. The lowest ratio of the diseases of sugar beet was observed in the object fertilized with the compost and biodynamic preparations. In view of the conventional fertilization methods, generally the highest incidence of diseases was noted in the sugar beet fertilized with straw, green manure and mineral fertilizers. The exception was the occurrence of powdery mildew and the black leg. In objects A, B and C the incidence of the diseases increased with the increase in nitrogen doses. The applied biodynamical preparations in the object D stimulated the development of diseases too.     

Prospects for control of Pythium damping-off of lettuce with Trichoderma,Gliocladium and Enterobacter spp.

Summary Damping-off of lettuce (Lactuca sativa) caused by Pythium ultimum was studied in pots containing a non-sterile potting mix in the glasshouse. Fifty P. ultimum sporangia g^-1 compost reduced the plant stand to 15% and shoot dry weight to 18%, but this reduction was totally prevented by applying Trichoderma harzianum at 2×10⁵ viable propagules g^-1 potting mix. Gliocladium virens and Enterobacter cloacae also alleviated the damping-off. E. cloacae did not adversely affect the action of the fungal antagonists. The co-existence of the bacterial and fungal antagonists was revealed on the root surface and inner surface of the testa by scanning electron microscopy, indicating the compatibility of the biocontrol agents.     

细菌、真菌及植物氮营养信号研究进展

氮素吸收代谢是所有生物生命活动的核心部分,因此,各种生物对氮的吸收与同化过程都有精细的调节。这种调节依赖于生物对体内氮素状况信号及体外（生长介质中）氮素信号的感受。过去几十年中,在细菌、真菌中已经对氮素营养信号有了较好的研究,而植物中则相对缓慢,但也有了一定的认识。本文重点比较细菌、真菌及植物中氮信号系统的组成,以期为进一步认识植物中的氮信号接受与转导系统提供启示。     

Aircraft operations near concentrations of birds in Antarctica: The development of practical guidelines

Aircraft operations have the potential to disturb and to impact negatively on bird life. A gradient of increasing behavioural response is evident in birds when exposed to increasing aircraft stimulus. The most major disturbance is likely to lead to impacts on the health, breeding performance and survival of individual birds, and perhaps bird colonies. A process of revision to policies on aircraft operations contained in management plans for a number of specially protected areas in Antarctica by the United Kingdom, accompanied by consultations made within the scientific community through the Scientific Committee on Antarctic Research (SCAR) and with operational interests through the Council of Managers of National Antarctic Programmes (COMNAP) resulted in new guidelines being adopted by the Antarctic Treaty Consultative Parties in June 2004. The principal recommendations of the guidelines are that bird colonies should not be overflown below 2000 ft (∼610 m) above ground level and landings within 1/2 nautical mile (∼930 m) of bird colonies should be avoided wherever possible. These guidelines are less stringent and less specific than those that were recommended by the SCAR specialist group on birds, and represent a compromise to accommodate operational needs. While the adoption of clear and consistent guidelines for the operation of aircraft in Antarctica is welcome in that this provides practical advice that is likely to reduce incidences of close aircraft/bird encounters, there remains insufficient knowledge of the interactions between aircraft and birds in Antarctica, and the consequent impacts on individual birds and on bird populations. It is important, therefore, that the guidelines adopted are considered interim, and should be kept under scrutiny with revisions made as new and improved research results appear.     

The abundance of heterocystous blue-green algae in rice soils and inocula used for application in rice fields

Summary Algal populations were quantified (as colony-forming units [CFU] per square centimetre) in 102 samples of rice soils from the Philippines, India, Malaysia and Portugal, and in 22 samples of soil-based inocula from four countries. Heterocystous blue-green algae (BGA) were present in all samples. Nostoc was the dominant genus in most samples, followed by Anabaena and Calothrix. In soils, heterocystous BGA occurred at densities ranging from 1.0 × 10² to 8.0 × 10⁶ CFU/cm² (median 6.4 × 10⁴) and comprised, on average, 9% of the total CFU of algae. Their abundance was positively correlated with the pH and the available P content of the soils. In soil-based inocula, heterocystous BGA occurred at densities ranging from 4.6 × 10⁴ to 2.8 × 10⁷ CFU/g dw (dry weight), comprising only a moderate fraction (average 13%) of the total algae. In most soils, the density of indigenous N₂-fixing BGA was usually higher than that attained by applying recommended rates of soil-based inoculum. Whereas research on the practical utilization of BGA has been mostly directed towards inoculation with foreign strains, our results suggest that attention should also be given to agricultural practices that enhance the growth of indigenous strains already adapted to local environmental conditions.Maître de Recherches ORSTOM (France), Visiting Scientist at IRRI