楸树无性系苗期氮素分配和氮素效率差异

为开展氮素高效型楸树(Catalpa bungei)无性系的选育,选取10个楸树无性系进行了高氮 （+N）和低氮 （-N）条件下植株体内氮素的分配和氮素效率差异研究。结果表明,-N下,大部分氮的分配为根＞叶＞茎;而+N下则相反,氮素的分配为叶＞茎＞根,且无性系间差异较小。+N下无性系的氮素效率极显著高于-N,且-N下无性系间的变异程度较高;氮素吸收效率和氮素利用效率都是-N下的变异程度较高,增加氮素用量可显著提高氮素吸收效率,但氮素利用效率显著降低。相关性分析可知,氮素吸收效率对氮素效率的贡献大于氮素利用效率。在两种氮条件下,无性系2-7和015-1的氮素效率较高。     

叶面施氮对不同类型大豆品种氮素积累与分配的影响

为研究大豆不同类型品种叶面氮素吸收、积累与分配规律,以黑龙江省三江平原大豆主栽4种类型品种为试验材料,采用¹⁵N示踪法在大豆R₅期进行叶面施氮,探究不同施氮量及品种类型各器官对标记氮素积累与分配规律。结果表明,在4.5 kg·hm^-2施氮量条件下,大豆各器官干物质量、氮素积累量及¹⁵N积累量总体均达到最高,不同类型品种间,亚有限尖叶型茎及叶器官干物质积累量最高,亚有限圆叶型叶柄、荚皮、籽粒及全株干物质积累量最高,无限圆叶型根、茎、叶、籽粒及全株氮素积累量最高,无限尖叶型叶柄和荚皮的氮素积累量最高,亚有限圆叶型根、茎和叶柄的¹⁵N积累量最高,无限圆叶型叶¹⁵N积累量最高,无限尖叶型籽粒¹⁵N积累量最高;¹⁵N分配率与积累量在根、叶、叶柄和荚皮器官均在同一处理达到最高,而在茎和籽粒中分配率与积累量的最高值不在同一处理。说明茎和籽粒中氮素分配率在不同处理间不同,更易受到叶面施氧的影响。本研究结果为大豆叶面氮素利用机制研究及不同类型品种叶面氮肥生产应用提供了理论依据。     

毛白杨对15N-硝态氮和铵态氮的吸收、利用及分配

以毛白杨新无性系50号插条苗为试材,应用15N示踪技术研究在相同施氮量下毛白杨(Populus tomentosa)苗木对不同形态氮素的吸收、分配及利用特性。结果表明：不同处理下毛白杨苗木在施肥1周后对肥料氮的吸收呈逐渐上升趋势,并在施肥后28d达到最大值,NO3-15N处理苗木全氮量为0.67g/株, NH4-15N处理苗木全氮量为0.60g/株;吸收NO3-15N为0.26g/株,吸收NH4-15N为0.12g/株,分别占苗木全氮的比例39.15%和19.95%。毛白杨苗木对两种氮素的利用程度差异显著,在利用率最高时期,NO3-15N利用率可达25.83%,约为NH4-15N（12.03%）的2倍。氮素在各器官中分配差异显著,总体趋势为叶﹥根﹥茎。叶中NO3-15N的分配率显著高于NH4-15N     

氮肥深追可提高玉米对15N的吸收、分配及利用

【目的】 利用15N示踪技术,探索不同追氮方式下玉米植株各组织器官氮素吸收、分配及氮素利用率的情况,为指导寒地玉米高产、高效施肥技术提供理论依据。 【方法】 试验以玉米品种德美亚3号为试验材料,设置不施氮肥（N0）、浅追施一次（S1）、深追施一次（D1）和深追施二次（D2）4个处理。分析了玉米氮素吸收、分配和利用特性,以及肥料贡献和残留。 【结果】 氮肥深追施处理玉米不同器官干物质积累量高于浅追,深追二次又显著高于一次（P < 0.05）;除茎外,深追二次玉米各器官氮素含量均显著高于其它处理（P < 0.05）;氮肥深追玉米各器官氮素积累量高于浅追,除茎和轴差异不显著外,根、叶和籽粒氮素积累量差异显著（P < 0.05）;深追处理15N标记氮素含量显著高于浅追（P < 0.05）,除穗轴外,其它器官间差异达到显著水平（P < 0.05）;氮素深追15N在玉米根和籽粒分配率高于浅追,在叶和轴内的分配率相反;深追一次15N在茎中的分配率高于浅追,深追二次则低于浅追。氮肥深追与浅追相比,氮素利用率分别显著提高了26.0%和14.1%（P < 0.05）;氮肥深追二次与一次相比差异也显著（P < 0.05）;土壤15N残留率深追二次和一次处理分别比浅追一次降低2.1%（P < 0.05）和1.2%,氮素损失率分别减少了23.9%和12.9%（P < 0.05）,肥料氮素贡献率深追二次和一次分别提高了3.6%（P < 0.05）和0.6%。 【结论】 氮肥深追可有效提高玉米的干物质积累、氮素吸收、分配及氮素利用率,降低土壤氮素残留率,提高氮肥的贡献率,且氮肥深追二次好于一次深追。     

基于15N 示踪的酿酒葡萄氮素营养需求分析

植物在不同时间对氮素营养的需求迥异,为掌握宁夏贺兰山东麓酿酒葡萄氮素分布特征和营养需求规律,以7 年生“赤霞珠”为研究对象,每株施氮255.10 g(15N- 硫酸铵10 g+ 普通硫酸铵245.10 g)。利用15N 同位素示踪技术,在施氮后35、70、105、140 和160 d 采集土壤和酿酒葡萄根、茎(茎分为主干、一级分枝、二级分枝)、叶、果,对其15N 丰度和全氮量进行测定分析。计算不同时间各器官肥料中吸收分配到的15N量对该器官全氮量的贡献率(Ndff)、分配率、氮肥利用率、残留率以及损失率。结果表明:根、主干、一级分枝、二级分枝、叶和果的干物质量均在施氮后70 ～ 105 d 明显增加,施氮后105 d 的干物质量较施氮后70d 分别增加了95.19%、4.23%、6.51%、58.58%、30.00% 和219.84%。在施氮后70 ～ 105 d,根、主干、一级分枝、二级分枝、叶和果的Ndff 值明显上升,施氮后105 d 的Ndff 值较施氮后70 d 分别增加了6.38、5.89、5.87、7.25、4.34 和7.01 个百分点。根的15N 分配率在施氮后35 d 高于其他施氮时期,为1.46%。主干、一级分枝和二级分枝的15N 分配率均在施氮后160 d 高于其他施氮时期。根、主干、一级分枝、二级分枝、叶和果的15N 分配率在施氮后70 ～ 105 d 均明显增加,施氮后105 d 的15N 分配率较施氮后70 d 分别增加了5.26、0.52、0.24、2.55、3.70 和3.21 个百分点。综上所述,酿酒葡萄在施氮后70 ～ 105 d 为氮素吸收峰值期,在此期间应注重氮肥的施入。整个施氮时期酿酒葡萄的氮肥利用率为38.97%,氮肥残留率为17.77%,氮肥损失率为43.25%。     

有机-无机缓释肥对番茄产量和氮肥利用率的影响

利用盆栽试验研究了有机-无机缓释肥料对番茄产量和氮肥利用率的影响。结果表明,与施用等NPK无机养分对照比较,施用缓释肥料B显著提高氮肥利用率,增加肥料氮在果实和叶片中的分配率;并且有利于后期产量形成,增产17.13%。施用缓释肥料A2提高氮肥利用率,增加肥料氮在根系和叶片中的分配率;并且有利于后期产量形成,增产16.33%。施用缓释肥料A2,氮肥利用率和产量的增幅均较小。     

不同施氮方式对甘蔗氮肥效率及氮素去向的影响

以新台糖22号(ROC22)为试材,通过网室盆栽试验方法,在总施氮量(15N标记尿素5g/盆,相当于450kg·hm-2)相同条件下,研究了全部基施(T1)、50%基施+50%在分蘖期追施(T2)和30%基肥+30%在分蘖期追施+40%在伸长期追施(T3)3种施氮方式对甘蔗氮肥效率与氮素去向的影响。结果表明:甘蔗吸收的氮素约18%～29%来源于当季施用的尿素氮,71%～82%来自土壤和种茎氮;氮肥利用率为21.0%～34.52%,残留率为37.61%～44.13%,有21.35%～41.39%的氮素损失。3种施氮方式下,氮肥残留在0～20cm土层较多,在20～40cm残留较少。随氮肥施用时间后移,甘蔗吸收的氮素、来源于肥料氮素的比率、氮肥利用率、氮肥残留率、蔗茎产量及产糖量明显增加,而氮肥损失率显著下降,蔗茎的氮素分配率和蔗糖分积累略呈下降趋势,同时氮素在0～20cm土层的残留呈上升趋势,在20～40cm土层呈下降趋势。从经济效益和环境效益考虑,T3施氮方式的效果较为理想。     

磁化处理促进施氮条件下葡萄氮素的代谢和分布

以‘夏黑’葡萄扦插苗为试验材料,采用盆栽试验方法,分析了磁化水灌溉后葡萄叶片、茎和根系中不同形态氮素含量、氮素代谢关键酶活性以及不同氮源的贡献率,探讨磁化作用对‘夏黑’葡萄扦插苗生长以及氮素吸收、分配和利用的影响。以~(15)N为外源氮肥,分3次施入土壤中。试验设置4个处理,包括:磁化水灌溉处理、非磁化水灌溉处理、磁化水灌溉+施氮处理、非磁化水灌溉+施氮处理。磁化处理组中利用磁化装置处理灌溉水。结果表明:1)施氮条件下,与非磁化处理相比,磁化处理后葡萄叶片、根系和全株的全氮量提高,但是肥料中~(15)N对不同器官中氮素的贡献率无显著差异;叶片和根系的氮素利用率显著提高;全氮在叶片中分配率显著提高,在茎中的分配率则显著降低。2)与非磁化处理相比,磁化处理后葡萄叶片中谷氨酰胺合成酶和谷氨酸合酶活性显著提高,根系中显著降低。3)与单独施氮相比,磁化水灌溉+施氮提高了土壤氮含量;氮肥中~(15)N利用率提高,损失率降低。由以上研究结果可以看出,磁化水灌溉不仅可提高氮素代谢关键酶活性,而且可提高不同器官中氮素营养的吸收和利用,从而改变了氮素在不同器官中的分布。     

氮肥用量对花生氮素吸收与分配的影响

为明确花生氮素吸收与分配规律,以花育25号为试验材料进行土柱栽培试验,采用¹⁵N 示踪法研究氮肥用量对花生不同器官氮素同化吸收与积累分配的影响。结果表明,当施氮量超过90 kg·hm^-2(N2)时,花生植株各器官干物质量及氮素积累量基本不再显著增加。籽仁干物重在3个施氮量(N1、N2、N3) 条件下分别较不施氮增加2.61%、5.32%和1.88%,且在施氮量90 kg·hm^-2(N2)时最高,为19.00 g/株。同一施氮量条件下,花生不同器官¹⁵N 积累量表现为籽仁> 叶> 茎>果壳>根;在不同施氮量条件下,¹⁵N 在花生各器官积累量随施氮量增加而增加。N2增加了¹⁵N 在籽仁中的分配比例,降低了茎和叶片中的分配比例,促进氮素由营养器官向生殖器官转运,提高了¹⁵N 在籽仁中的积累量,其氮肥利用率分别较N1、N3和N4提高22.77%、17.56%和28.13%。综上,本试验条件下施用90 kg·hm^-2氮素(N2)可提高花生籽仁干物重,增加氮素积累量和氮肥利用率。一元二次方程模拟结果表明,77.19 kg·hm^-2为花生产量最高的最适施氮量。本研究结果为花生氮肥利用率及氮肥的合理施用提供了理论依据。     

施氮水平对甘蔗氮素吸收与利用的影响

以新台糖22号(ROC22)为试材,设15N标记尿素2.5、5.0和7.5g/盆(相当于225、450和675kg/hm2)3个处理,采用网室盆栽试验方式,研究施氮水平对甘蔗氮素吸收与利用的影响。结果表明:甘蔗吸收的氮素17.27%～27.28%来自施用的氮肥,72.72%～82.73%来自土壤和种茎;甘蔗氮肥利用率为34.21%～42.46%。随施氮水平提高,甘蔗干物质积累、氮素积累及来源于肥料氮素的比率显著增加,同时蔗叶对氮素的吸收利用呈上升趋势,但蔗茎对氮素的吸收利用呈下降趋势,氮肥利用率也显著下降。土壤碱解氮和硝态氮在各土层中的含量随施氮水平的提高而增加,且两者在0～20cm土层的积累明显大于20～40cm土层。本试验条件下,甘蔗氮肥施用为尿素5.0g/盆(相当于450kg/hm2)及土层深度为20cm较为适宜。     

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