我国沙棘工业原料林品种介绍

沙棘属(Hippophae)植物是一种发源自青藏高原,分布于欧亚大陆,在我国三北地区(西北、华北、东北)一般呈灌木状,在西南地区多呈小乔木、乔木状生长的高效水土保持植物。多年来,我国人工种植的沙棘多为中国沙棘(Hippophae rhamnoides ssp.sinensis)亚种,而从俄罗斯、蒙古引进的所谓大果沙棘,多为蒙古沙棘(Hippophae rhamnoides ssp. monglica)亚种。     

陕西吴起县退耕还林地不同植被水土保持效益分析

在全国退耕还林工程示范县陕西省吴起县退耕还林地内设置了野外径流小区,在对其进行了土壤物理性质、入渗、抗冲实验及实测泥沙资料基础上,分析了退耕还林后不同植被类型的水土保持效益,结果显示:土壤入渗的初渗率、稳渗率、平均入渗率大小顺序为油松荒草地沙棘+油松b沙棘+油松a沙棘;土壤抗冲性能沙棘林地最强,沙棘+油松林地次之,油松林地最弱;土壤产沙量为油松林地最大,沙棘与沙棘+油松林地相对较少;地表径流量为油松林地荒草地沙棘+油松林地b沙棘+油松林地a沙棘林地;退耕还林后,土壤物理性质得到不同的改良。油松林地的土壤容重最高,土壤总孔隙度与土壤毛管孔隙度最低。因此,退耕还林可有效地防治水土流失,而不同植被类型中沙棘纯林的水土保持效益最为显著。     

陕北黄土高原不同植被类型下降雨对坡面径流侵蚀产沙的影响

通过对陕北黄土高原吴起县退耕地5个不同植被类型径流小区降雨对径流产沙影响的分析,研究退耕还林后不同植被类型的水土保持效应。结果表明:(1)降雨量与雨强对径流量的影响显著;小区建立初期5个径流小区的产流状况从大到小为油松>草地>沙棘+油松(Ⅱ)>沙棘+油松(Ⅰ)>沙棘;随着植被生长,产流从大到小为草地>沙棘+油松(Ⅱ)>沙棘>油松>沙棘+油松(Ⅰ)。随着林分郁闭度的增大,降雨与径流量的相关性在减少。(2)径流量与雨强对产沙量的影响显著;小区建立初期5个径流小区的产沙量从大到小顺序为油松>沙棘+油松(Ⅱ)>草地>沙棘>沙棘+油松(Ⅰ);随着植被生长,产沙量从大到小为草地>油松>沙棘>沙棘+油松(Ⅱ)>沙棘+油松(Ⅰ)。随着植被生长,产沙量基本趋于稳定。(3)坡度对径流产沙的影响显著。同一场降雨,植被类型相同,坡度大的径流量大、产沙量也大;坡度相近的小区,小区建立初期径流产沙量从大到小为油松>沙棘+油松(Ⅱ)>草地>沙棘>沙棘+油松(Ⅰ);随着植被生长,径流产沙从大到小为草地>油松>沙棘>沙棘+油松(Ⅱ)>沙棘+油松(Ⅰ)。因此,退耕还林后,林草植被恢复有效减少了水土流失,在造林初期,沙棘纯林的水土保持效果最为显著,随着植被生长,(沙棘+油松)混合林地的水土保持效应效果最佳。     

黄土丘陵区沙棘混交林叶片、凋落物、土壤碳氮磷化学计量特征

以黄土丘陵区沙棘(Hippophae rhamnoides)+油松(Pinus tabuliformis)、沙棘(H.rhamnoides)+刺槐(Robinia pseudoacacia)混交林(H_rP_t、H_rR_p)及油松(P_t)和刺槐(R_p)纯林为对象,测定叶片、凋落物和0—100 cm土壤C、N、P含量及其化学计量比,探究混交造林对不同组分间养分协同变化规律的影响。结果表明:(1)相比P_t,H_rP_t中油松叶片C、N、P含量(p0.05)及N∶P(p0.05)增加,C∶N和C∶P降低(p0.05),表明H_rP_t有助于缓解N限制,加快其生长速率;相比R_p,H_rR_p中刺槐叶片C、N含量及C∶P和N∶P降低,P含量及C∶N增加(p0.05),表明H_rR_p增强刺槐对P的吸收,但降低其对C和N的固存;(2)相比P_t,H_rP_t凋落物C、N、P含量及N∶P增加,C∶N和C∶P降低(p0.05),表明H_rP_t有助于加快凋落物分解,促进养分归还;相比R_p,H_rR_p凋落物C、N、P含量及其计量比均有所增加(p0.05),表明H_rR_p对凋落物分解无显著作用;(3)相比P_t和R_p,H_rP_t和H_rR_p土壤C、N、P含量增加,但C∶N和C∶P降低(p0.05),表明H_rP_t和H_rR_p均有助于提高N和P利用效率,改善土壤养分状况;(4)叶片、凋落物化学计量指标间具有较强协同效应,且N、P相比C在不同组分间的相关性更明显。综上,相比H_rR_p,H_rP_t更有助于改善养分限制因子供给,加快组分间养分转化。研究结果对于揭示黄土高原地区人工混交林生态系统养分供应潜力及合理制定营林规划具有重要意义。     

不同土壤水分条件对中国沙棘和俄罗斯沙棘的光合和蒸腾作用的影响

在野外不同生境和田间不同干旱条件下,对中国沙棘(Hippophae rhamnoides sinensis)和俄罗斯沙棘(Hippophae rhamnoides)的光合和蒸腾作用的日进程进行研究后发现:随着土壤水分含量的增加,沙棘的光合速率和蒸腾速率随之升高。在不同的土壤水分条件下,光合作用和蒸腾作用的日进程表现为双峰或单峰曲线,峰值的出现时间也随土壤水分条件的变化而变化。中国沙棘光合速率的日平均值表现为雌株高于雄株,而俄罗斯沙棘表现为水分条件适宜时雄株略高于雌株,受到干旱胁迫后雌株大于雄株;且俄罗斯沙棘的光合能力优于中国沙棘。俄罗斯沙棘蒸腾速率的日均值为雌株高于雄株,中国沙棘雌雄株蒸腾速率的差异规律不一致。光合速率和蒸腾速率与土壤含水量的回归分析表明:二者呈显著的正相关,回归方程为一元二次方程,复相关系数接近1。     

中国四个地区代表性沙棘果实综合品质评价

为明确中国代表性产区沙棘品质的差异，该研究以山西、河北、内蒙古、新疆地区加工使用频率高的4个沙棘品种（中国沙棘Hippophae rhamnoides.L.Zhongguoshaji、宇璐沙棘Hippophae rhamnoides.L.Yulushaji、中国沙棘Hippophae rhamnoides.L.Zhongguoshaji、阿勒泰大果沙棘 Hippophae rhamnoides.L.Aletaidaguoshaji）为研究对象，从色泽、质地、滋味、风味、营养功能组分等方面研究其品质，测定沙棘浆中的香气成分和小分子活性物质组成，明确4个地区沙棘的综合品质，并探究不同地区沙棘综合品质的差异。结果显示：新疆阿勒泰大果沙棘色泽最鲜艳；内蒙古中国沙棘的糖酸比（1.997）最大；河北宇璐沙棘总酚含量（1.14 mg/g）最高；新疆沙棘类胡萝卜素含量（37.15 mg/100 g）最高；4种沙棘维生素C的含量无明显差异（P>0.05），约为21～23 mg/100 g；4种沙棘抗氧化活性水平存在显著差异，山西沙棘DPPH自由基清除率最高（P<0.05），内蒙古沙棘的ABTS自由基清除率和铁离子还原能力（FRAP）均最高（P<0.05）。4个地区沙棘挥发性成分差异显著（P<0.05），其中河北、内蒙古、新疆、山西沙棘中特征挥发物质分别为3-辛酮、2-庚烯醛等，异戊酸异丙酯、2-甲基丁酸丙酯等，正辛烷、2,3-二氢-2,2,6-三甲基苯甲醛，己酸戊酯、癸酸乙酯。4个地区沙棘主要多酚类物质包括奎宁酸、异鼠李素、阿洛酮糖等。4个地区沙棘14项品质指标进行因子分析，共提取3个公因子，累计方差贡献率达到100%。综合品质评价模型得出，4个地区代表性沙棘品种综合品质得分依次为河北沙棘，山西沙棘，内蒙古沙棘，新疆沙棘。该研究将为沙棘系列产品的开发原料选择提供理论依据和基础。     

青海共和盆地不同人工灌木群落土壤碳密度研究

共和盆地高寒沙区植被恢复区4种典型人工灌木林是柠条(Caragana korshinskii)、沙棘(Hippophae rhamnoides)、沙柳(Salix psammophila)和乌柳(Salix cheilophila)。土壤有机碳密度调查研究表明,不同灌木群落类型下的土壤有机碳密度(0~100 cm)由大到小是:沙棘9.42 kg/m2、沙柳6.73 kg/m2、乌柳6.06 kg/m2、草地4.56 kg/m2、柠条3.67 kg/m2。不同灌木林地0~100 cm土壤质地和分层状况不同,土壤有机碳含量随着土壤深度增加而减少,表层(0~10 cm)含量最高。与对照样地草地相比,位于丘间地的林地土壤有机碳含量均有不同程度的提高。     

晋北风沙区人工林土壤水分及粒度特征

以位于晋北风沙区右玉县贾家窑6种人工林地(11 a油松林、21 a油松林、23 a华北落叶松林、17 a油松+柠条混交林、柠条林和沙棘林)为研究对象,通过测定土壤含水量及粒度、计算粒度参数等分析比较不同林地土壤水分和粒度的变化及分布。结果表明:1)在0~100 cm深度,6种林地平均土壤含水量由大到小依次为:沙棘林11 a油松林柠条林17 a油松+柠条混交林23 a华北落叶松林21 a油松林;0~20 cm土层土壤含水量相对较低,较深土层土壤水分受植物蒸腾耗水、根系分布深度及密度等因素影响;2)6种林地的粒度组成以极细砂和粉粒为主。7个粒级中,柠条林和沙棘林粉粒占比最大,其他林地极细砂含量占比最大;3)在0~100 cm深度,6种林地土壤平均粒径大小依次为:23 a华北落叶松林11 a油松林21 a油松林17 a油松+柠条混交林沙棘林柠条林;4)沙棘林和柠条林有较强的水土保持能力,在晋北风沙区植被恢复过程中可以优先选择沙棘和柠条进行造林;5)研究区经过多年植被恢复,人工林耗水量增加。认为有必要根据土壤水分状况结合植被耗水特性和生长阶段开展人工林的科学管护,如适当调整植被盖度,加强林下草本和枯落物保护。     

皖西南大沙河流域水沙变化及其与人类活动的影响

在野外不同生境和田间不同干旱条件下，对中国沙棘（Hippophae rhamnoides sinensis）和俄罗斯沙棘（Hippophae rhamnoides）的光合和蒸腾作用的日进程进行研究后发现：随着土壤水分含量的增加，沙棘的光合速率和蒸腾速率随之升高。在不同的土壤水分条件下，光合作用和蒸腾作用的日进程表现为双峰或单峰曲线，峰值的出现时间也随土壤水分条件的变化而变化。中国沙棘光合速率的日平均值表现为雌株高于雄株，而俄罗斯沙棘表现为水分条件适宜时雄株略高于雌株，受到干旱胁迫后雌株大于雄株；且俄罗斯沙棘的光合能力优于中国沙棘。俄罗斯沙棘蒸腾速率的日均值为雌株高于雄株，中国沙棘雌雄株蒸腾速率的差异规律不一致。光合速率和蒸腾速率与土壤含水量的回归分析表明：二者呈显著的正相关，回归方程为一元二次方程，复相关系数接近1。     

黄土高原不同林型对土壤腐殖质组成及胡敏酸性质影响的研究

不同林型下土壤腐殖质研究表明:(1)当年枯枝落叶及表层土壤C/N值均以油松林地最大,沙棘林地最低;表层土壤C/N值与林龄、枯枝落叶C/N呈正相关,与枯枝落叶灰分含量呈负相关。(2)剖面中腐殖酸、胡敏酸、富里酸各平均值为白桦林地>辽东栎林地>辽东栎×山杨林地>山杨林地>沙棘林地>油松林地,即阔叶乔木林地>灌木林地>针叶林地;胡敏素平均值大小顺序与此完全相反。(3)表层土壤胡敏酸芳构化程度在子午岭的为:白桦林地>辽东栎林地>辽东栎×山杨林地>山杨林地>油松林地>沙棘林地;六盘山为:山杨林地>辽东栎林地。剖面芳构化程度为:三层>二层>一层。     

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