关中地区塿土系统分类归属及代表土系建立

塿土是关中地区受人为长期土粪堆垫而在原土壤表层形成明显堆垫层的重要农业土壤,其分类一直备受关注。为了解塿土的成土特点及系统分类归属,选取关中地区18个典型塿土剖面,通过野外成土因素、剖面形态调查与土样分析测定,依据中国土壤系统分类方案,确定其在高级和基层分类单元归属。结果表明,供试剖面包含堆垫表层、黏化层、钙积层等9个诊断层和诊断特性,隶属5个亚类,其中3个剖面为钙积土垫旱耕人为土,2个剖面为斑纹土垫旱耕人为土,8个剖面为普通土垫旱耕人为土,4个剖面为堆垫简育干润淋溶土,1个剖面为普通简育干润雏形土;按土族划分标准,可分为9个土族,其中13个剖面颗粒大小级别为黏壤质,5个为壤质;16个剖面矿物学类型为硅质混合型,2个剖面为混合型,土壤温度状况均为温性,14个剖面为石灰性,4个剖面为非酸性;按土系划分标准,18个剖面可划分为18个不同的土系。相关文献的71个塿土剖面的统计结果表明,堆垫层厚度介于17~97 cm,平均厚度为50.07 cm,因此堆垫表层以50 cm厚度为检索标准是适宜于划分典型塿土的高级分类归属的。为进一步完善中国土壤系统分类,强化对具有堆垫现象的雏形土有更强的区分能力和分类的准确性,建议在简育干润雏形土土类下增设堆垫简育干润雏形土亚类。     

宁夏山地土壤的发育规律及系统分类研究

为全面了解宁夏山地土壤的发育特性及其系统分类归属,基于宁夏土系调查项目挖掘的典型剖面,选取10个发育在宁夏贺兰山山地(剖面编号为3、11、13、14和108)和六盘山山地(剖面编号为73、82、119、120和121)的土壤作为研究对象,结合剖面形态特征和理化性质,尝试对山地土壤的发育特征和系统分类归属进行研究。结果表明:(1)发育在宁夏的10个山地土壤高级单元归属为新成土、雏形土、淋溶土和均腐土等4个土纲,正常新成土、干润雏形土、湿润雏形土、冷凉淋溶土、湿润均腐土等5个亚纲,干旱正常新成土、简育干润雏形土、暗沃干润雏形土、冷凉湿润雏形土、简育冷凉淋溶土、斑纹湿润均腐土等6个土类,石灰干旱正常新成土、普通简育干润雏形土、普通暗沃干润雏形土、暗沃冷凉湿润雏形土、普通简育冷凉淋溶土、斑纹简育湿润均腐土等6个亚类,续分为10个土族,包括粗骨砂质硅质混合型温性—石灰干旱正常新成土,粗骨砂质长石型温性—石灰干旱正常新成土,壤质长石混合型石灰性冷性—普通简育冷凉淋溶土,砂质硅质混合型非酸性冷性—斑纹简育湿润均腐土等,10个供试剖面在土族完全分异,因而续分为10个土系,包括葡萄泉系、一堆系、滚钟口系、六盘山公园系、绿塬腰系等10个土系。(2)海拔对宁夏山地土壤的发育特征有着明显影响,表现为随海拔升高:腐殖质积累过程逐渐明显、土体淋溶过程加剧、土体石灰反应逐渐减弱直至消失;土壤水分条件逐渐改善,处于高海拔位置的山地土壤土体底部有弱氧化还原反应发生,形成铁子和铁锰胶膜;土壤pH逐渐减小,土壤酸碱性发生一定的变化。(3)受成土环境和成土因素的作用,土壤发育规律在诊断特征上的反映为随海拔高度的抬升呈现一定的垂直分异规律,其中诊断表层由淡薄表层演变为暗沃表层;土壤水分状况经干旱/半干润土壤水分状况向湿润土壤水分状况演化;土壤温度状况由温性土壤温度状况变为冷性状况。     

陕西黑垆土在中国土壤系统分类中的归属

在分析陕西省境内9个黑垆土剖面成土环境、剖面形态特征及理化性质的基础上,按照中国土壤系统分类高级及基层分类检索标准,确定了其在中国土壤系统分类中的归属。9个黑垆土剖面的腐殖质层厚度介于30～120 cm,通体均具有强石灰反应,CaCO_3含量介于12.5～189.5 g/kg,其中6个剖面具有30～45 cm的堆垫层。黑垆土共包括淡薄表层、暗沃表层、雏形层、黏化层、钙积层5个诊断层和堆垫现象、钙积现象、盐积现象3个诊断现象,均腐殖质特性、温性土壤温度状况、半干润土壤水分状况以及石灰性4个诊断特性。9个黑垆土剖面在高级分类上可检索为淋溶土和雏形土2种土纲,向下继分为普通钙积干润淋溶土、钙积暗沃干润雏形土、钙积简育干润雏形土以及普通简育干润雏形土4个亚类;其土族鉴别特征可分为黏壤质混合型温性、壤质硅质混合型石灰性温性、壤质混合型温性等6个土族以及胡家庙系、崾崄系、崔木系等9个土系。但目前的系统分类检索结果未能体现黑垆土具有深厚腐殖质层及堆垫现象的典型特性,因此黑垆土的系统分类归属仍需开展深入研究,同时建议新增堆垫干润雏形土土类或堆垫简育干润雏形土亚类,以体现人为农业生产活动对黄土高原地区土壤的影响。     

湘东地区花岗岩红壤在中国土壤系统分类中的归属

为了研究湖南省东部花岗岩红壤在中国土壤系统分类中的归属,选取湘东地区8个由花岗岩母质发育的典型土壤剖面,在对其成土环境、剖面形态特征及其理化性质进行研究的基础上,按照中国土壤系统分类方案,检索出了其诊断层和诊断特性,据此确定了其在中国系统分类中的归属。结果表明,供试的8个土壤剖面包含了淡薄表层、暗瘠表层、低活性富铁层、黏化层等9个诊断层和诊断特性,其在中国系统分类体系中的位置分别为:淋溶土、富铁土和雏形土3个土纲;湿润淋溶土、湿润富铁土和湿润雏形土3个亚纲;简育湿润富铁土、铝质湿润淋溶土、酸性湿润淋溶土和铝质湿润雏形土4个土类;普通铝质湿润雏形土、普通简育湿润富铁土、普通铝质湿润淋溶土、普通酸性湿润淋溶土4个亚类;按照土族和土系划分标准,建立了黏壤质硅质混合型酸性热性-普通铝质湿润雏形土等6个土族和脱甲系(43-CS18)等8个土系。实践表明,目前的土族土系划分标准适用于供试土壤基层分类单元划分。与土壤发生学分类结果相比,土壤系统分类结果更能定量反映出湘东花岗岩母质发育土壤性状的差异,进而客观反映出土壤发育阶段和土壤类型的差异。     

河南省典型淋溶土土系划分研究

在河南省选取8个典型土壤剖面,对其进行景观特征、剖面形态学特征的描述及其理化性质的分析,并确定其在土壤系统分类(Chinese Soil Taxonomy)中的归属,结果表明,供试土壤归属于壤质混合型石灰性温性普通简育干润淋溶土、壤质混合型非酸性温性斑纹简育湿润淋溶土、黏壤质混合型温性斑纹钙积干润淋溶土、黏壤质混合型温性普通钙积干润淋溶土、壤质混合型石灰性温性普通简育湿润淋溶土和壤质混合型非酸性温性普通简育湿润淋溶土等6个土族;并在此土族基础上,根据土系划分规则和河南地区淋溶土诊断特征及构型特征,尝试提出"土系对比检索逻辑图"以阐述土系参比划分的逻辑过程。通过对比,可将8个典型土壤剖面划分为7个土系:汤阴系、汲水系、神沟系、尚庄系、侯集系、枣林系和尚店系。     

河南中西部典型褐土在系统分类中的归属

选取位于河南中西部褐土土类的7个典型单个土体作为研究对象,通过土壤剖面形态特征和理化性质的分析,确定了它们在中国土壤系统分类中的位置。按照《中国土壤系统分类(第三版)》诊断标准,供试剖面中诊断出包括黏化层、钙积层、雏形层、氧化还原特征、温性土壤温度状况、半干润土壤水分状况等诊断层和诊断特性,7个剖面中,4个划归淋溶土纲,3个划归雏形土纲;按照土族和土系划分标准建立了杨岭系、诸葛系等7个土系。从高级分类单元和基层分类单元分别对7个土壤进行发生分类与系统分类之间的参比。此外,在高级分类单元级别上进行了中国土壤发生分类、中国土壤系统分类、美国土壤系统分类和世界土壤资源参比基础之间的参比研究,并建议中国土壤系统分类中新增"钙积干润雏形土"土类。     

湘北地区典型水稻土的发生特性及其在中国土壤系统分类中的归属

选取湘北地区7个发育于2种母质的水稻土剖面样点,通过对其成土环境、剖面形态特征以及土壤理化性质进行野外观测和室内分析,按中国土壤系统分类方案,检索出诊断层和诊断特性,确定其在中国土壤系统分类中的归属,并评述土系的生产性能。结果表明:供试水稻土归属于水耕人为土亚纲下的简育和铁聚水耕人为土2个土类,底潜简育水耕人为土、普通简育水耕人为土、普通铁聚水耕人为土、漂白铁聚水耕人为土4个亚类;进一步按照土族和土系划分标准,划分出7个土族和7个土系。在相同成土环境下,同种母质发育的水耕人为土,土壤系统分类比土壤发生分类具有更强的划分能力。其划分的基层土壤单元(土族和土系),对农业生产、土地资源利用更具有指导意义。     

湘东第四纪红色黏土发育的典型土壤在中国土壤 系统分类中的归属

选取湖南省东部地区12个由第四纪红色黏土发育的典型土壤剖面,在对其成土环境、剖面形态特征及其理化性质进行研究的基础上,按照中国土壤系统分类方案,检索出了其诊断层和诊断特性,据此确定了其在中国土壤系统分类中的归属。结果表明,供试土壤剖面包含了淡薄表层、暗瘠表层、低活性富铁层、黏化层、聚铁网纹层等10个诊断层和诊断特性,其在中国系统分类体系中的位置分别为:淋溶土、富铁土和雏形土3个土纲;湿润淋溶土、湿润富铁土和湿润雏形土3个亚纲;简育湿润富铁土、铝质湿润淋溶土和铝质湿润雏形土3个土类;暗红简育湿润富铁土、表蚀简育湿润富铁土、网纹简育湿润富铁土等6个亚类;按照土族和土系划分标准,建立了黏质高岭石型酸性热性-普通铝质湿润淋溶土等9个土族和燕塘系(43-LY01)等12个土系。研究发现:受亚热带气候影响,许多土壤剖面发生了富铁铝化过程,且由于淋溶强烈,形成了聚铁网纹层,而现行的《中国土壤系统分类检索(第三版)》还不能给出一个合适的位置,因此建议在铝质湿润淋溶土亚类中增设一个可以反映相关特性的网纹铝质湿润淋溶土亚类。     

湘东第四纪红土母质发育的典型土壤在中国土壤系统分类中的归属

选取湖南省东部地区12个由第四纪红色黏土发育的典型土壤剖面，在对其成土环境、剖面形态特征及其理化性质进行研究的基础上，按照中国土壤系统分类方案，检索出了其诊断层和诊断特性，据此确定了其在中国土壤系统分类中的归属。结果表明，供试土壤剖面包含了淡薄表层、暗瘠表层、低活性富铁层、黏化层、聚铁网纹层等10个诊断层和诊断特性，其在中国系统分类体系中的位置分别为：淋溶土、富铁土和雏形土3个土纲；湿润淋溶土、湿润富铁土和湿润雏形土3个亚纲；简育湿润富铁土、铝质湿润淋溶土和铝质湿润雏形土3个土类；暗红简育湿润富铁土、表蚀简育湿润富铁土、网纹简育湿润富铁土等6个亚类；按照土族和土系划分标准，建立了黏质高岭石型酸性热性-普通铝质湿润淋溶土等9个土族和燕塘系(43-LY01)等12个土系。研究发现：受亚热带气候影响，许多土壤剖面发生了富铁铝化过程，且由于淋溶强烈，孔隙周围形成了聚铁网纹层，而现行的《中国土壤系统分类检索（第三版）》还不能给出一个合适的位置，因此建议在铝质湿润淋溶土亚类中增设一个可以反映相关特性的网纹铝质湿润淋溶土亚类。     

广西岩溶地区水稻土发生特性及其在中国土壤系统分类中的归属

为明确广西岩溶地区水稻土在中国土壤系统分类中的归属，以该区域不同母质发育的水稻土为研究对象，挖掘20个典型剖面，通过野外观测、分层取样与分析，依据《中国土壤系统分类检索（第三版）》进行分类检索。结果表明，大多剖面出现明显的复钙现象。供试剖面的系统分类高级单元归属为人为土土纲，水耕人为土亚纲，潜育、铁聚和简育水耕人为土3个土类，复钙、铁聚和普通潜育水耕人为土、复钙和普通铁聚水耕人为土、复钙和普通简育.水耕人为土7个亚类，在系统分类基层单元归属上，可划归出17个土族和续分为20个土系。考虑广西地区水耕人为土耕作层Ap1碳酸钙相当物含量往往低于犁底层Ap2的现象，而现行水耕人为土复钙亚类的检索中“表层土壤”的“表层”不尽明确而可能导致的亚类误判，建议将其修改为“水耕表层（耕作层或犁底层）土壤”；另外，由于实际调查发现广西地区的一些铁聚水耕人为土也具有复钙特征，建议在检索中增设复钙铁聚水耕人为土亚类。     

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