湿陷性黄土地区土壤洞穴侵蚀研究

土壤洞穴侵蚀是湿陷性黄土地区普遍发生的一种独特的土壤侵蚀方式，其危害具有多重性。目前土壤洞穴还缺乏统一的分类与命名，土壤洞穴侵蚀成因机制尚未形成统一的认识和定量的表述。在大量野外调查和前人研究成果的基础上，首先提出了一套统一的土壤洞穴分类命名方法，在总结目前关于土壤洞穴侵蚀成因观点的基础上结合各种现场与室内试验成果，对土壤洞穴侵蚀的成因机制进行了新的探讨，阐明了对土壤洞穴侵蚀的一些新的看法和观点，为土壤洞穴侵蚀的进一步深入研究提供了基础。     

植物篱-农作模式坡耕地土壤综合抗蚀性特征

土壤抗剪强度、抗蚀性与抗冲性不仅反映了土壤对水力侵蚀不同发育阶段（雨滴溅蚀、薄层水流片蚀与股流沟蚀）的侵蚀力大小,还通过共存、耦合决定对抗水力侵蚀的综合能力（综合抗蚀性）的大小。利用植物篱控制水土流失的长期定位试验,采用数理统计法研究了植物篱-农作坡耕地土壤综合抗蚀性特征。结果表明,由于植物篱模式下土壤理化性质得以改善,加之网状植物篱根系的固结等作用促使土壤综合抗蚀性增强。紫穗槐、香根草、紫花苜蓿和蓑草植物篱-农作模式土壤综合抗蚀指数分别比常规横坡农作模式增加102.9%、91.9%、87.9%、82.9%。不同植物篱模式增强土壤综合抗蚀性效应的大小为,20o坡地紫穗槐>香根草,13o坡地紫花苜蓿>蓑草。植物篱模式也增强了各坡位土壤综合抗蚀性,改善了土壤综合抗蚀性的过大坡面异质性。该论文为进一步探究植物篱模式控制水土及氮磷等污染物流失提供参考。     

陡坡的细沟间侵蚀与径流

本文测定了504mm×504mm土盒中扰动Hagerstown粉砂粘壤土的细沟间侵蚀和径流,试验持续降雨20min,雨强为92mm/h,坡度为5%~85%。稳定状态下的土壤流失量(径流中的土壤悬移质)随坡度的增加而增加,5%坡侵蚀率为3.34g/m~2·min,85%坡增到22.47g/m~2·min。随坡度的增加土壤溅蚀的变化为:坡面下部增加,坡面上部减小,侧面稍有增加。土壤溅蚀总量(坡顶+坡底)与净坡底溅蚀量(坡顶-坡底)也随坡度的增加而增加。85%坡净土壤溅蚀达3.5g/m~2·min,85%的坡面上99%的土壤溅蚀运动到坡底。15%~85%坡面的稳定径流率没有区别,其平均径流率为66.5mm/h。单位面积的冲蚀和溅蚀总量同坡度呈线性关系。比较了实测的冲蚀和溅蚀总量与WEPP模型的估算值,结果表明坡度大于30%时实测值要大于WEPP模型的预测值(85%时要大1倍)。     

元谋干热河谷潜蚀洞穴的环境灾害效应

元谋干热河谷地区潜蚀洞穴分布十分广泛,发达的洞穴不仅破坏地表形态,加速土地退化,还对当地居民生活构成威胁。同时由于地下洞穴排沙,洞内大体积悬空从而诱发其他地质灾害的产生,加剧了元谋干热河谷地区生态环境的恶化。采用野外实地调查、文献资料分析的方法,对元谋干热河谷潜蚀洞穴的危害进行了分析,为干热河谷洞穴灾害的防治和当地生态环境的恢复提供了科学依据。     

不同复合种植模式对土壤可蚀性K值与侵蚀量的影响研究

采用野外调查与室内分析相结合的方法,把4种农作物引入复合种植模式中,以土壤可蚀性K值、径流量、侵蚀量为指标,对紫色土区不同复合种植模式与水土流失特征的关系进行分析和研究.研究结果表明:(1)与单一的种植模式相比,不同复合种植模式使水土流失敏感性增强,K值增大,土壤容易被侵蚀.(2)土壤可蚀性K值与土壤砂粒含量呈极显著负相关,相关系数为-0.957;与土壤黏粒含量、有机C含量呈负相关,相关系数分别为-0.191,-0.637;与粉粒含量呈显著的正相关,相关系数为0.986.黏粒及有机质含量的高低是反映紫色土区土壤抗侵蚀能力强弱的有效指标.(3)与柚子纯林种植模式相比,复合种植模式的径流截留效益显著.综合各项指标发现,柚子—粉葛复合模式抗侵蚀效果最好,最适宜推广种植.     

土壤抗蚀性的研究动态

在综述土壤抗蚀性研究成果及抗蚀性研究方法的基础上 ,介绍了土壤抗蚀性研究的进展 ,并指出目前土壤抗蚀性研究方法存在的问题 ,提出土壤抗蚀性研究应建立在侵蚀动力和土壤抗侵蚀力作用过程的基础上 ,从土壤侵蚀过程中各种因素的作用机理出发 ,使土壤抗蚀性的研究标准化、定量化 ,为土壤流失预报及水土流失调控措施的设计提供科学依据     

东北黑土漫岗区土壤侵蚀垂直分带性研究

东北黑土漫岗区由于其独特的自然地理与人文环境特征表现出独特的侵蚀产沙特性。通过对典型黑土漫岗区土壤侵蚀宏观遥感调查、微地貌采样调查及对该区域的实地考察，总结出该区土壤侵蚀随宏观地貌及微地貌垂直分带变化的一般特点。从黑土漫岗区土壤面蚀与沟蚀发展的一般过程出发，提出了该区土壤面蚀、沟蚀发展的一般模式。研究结果将有助于对黑土侵蚀过程的认识，进而为该区侵蚀泥沙来源与沉积位置的确定、坡沟治理的方针以及水保措施配置等重大理论与治理决策问题提供理论基础。     

花岗岩风化壳抗侵蚀特征研究 Ⅰ花岗岩风化壳物理特征

本研究根据室内外对花岗岩及其风化壳测试的物理和化学特征，利用有关土壤抗冲性和抗侵性指标以及野外实测资料，对花岗岩风化壳的地球化学过程，形成条件及抗侵蚀进行了综合分析与评价，指出垂节理发育的花岗岩体在持续的暖湿气候作用下形成的疏松深厚风化壳是土壤侵蚀特别是切沟和崩岗沟发育的物质基础，中粗晶花岗岩发育土壤表层砂砾作含量高而粘粒少，抗侵蚀性弱，有机质矿质化快，土壤生态系统脆弱，加上风化壳中抗侵蚀性极弱的砂土层存，这是导致花岗岩土壤侵蚀特别严重的内在原因，松耕土壤抗侵蚀能力仅为自然坡地未扰动土壤的1／。10，建议加强坡耕旱地面覆盖，作者指出，土壤的抗侵蚀能力强弱是一个相对概念，其随侵蚀动力类型和强弱不同而显示不同的特征，在侵蚀动力较弱情况下，抗蚀性是影响土壤抗侵蚀性能的主要方面，在较强侵蚀动力下，土壤的抗冲性将上升为影响土壤抗侵蚀性能的主导方面。     

花岗岩红壤侵蚀退化地不同治理模式土壤抗蚀性评价

为探究花岗岩红壤侵蚀退化地不同治理模式对土壤抗蚀性的影响，通过野外调查与室内外试验，以长汀县封禁（M1）、乔灌草混交（M2）、全坡面播草（M3）、低效林改造（M4）、条沟草灌带（M5）这5种治理模式的土壤为研究对象，选取开垦地（CK1）和裸露地（CK2）为对照，利用主成分分析法揭示土壤抗蚀性主要影响因子，并结合灰色关联分析和耦合分析对土壤抗蚀性进行综合评价。结果表明：（1）不同治理模式的土壤抗蚀性由强到弱依次为M5 > M2 > M3 > M4 > M1 > CK2 > CK1；（2）> 0.25 mm水稳性团聚体含量和有机质含量是影响土壤抗蚀性的主要因子；（3）土壤抗蚀性与土壤理化性质的灰色关联度较高（0.696），M3的土壤抗蚀性与土壤理化性质之间系统耦合度最高（0.883）。研究结果为花岗岩红壤侵蚀退化地的水土流失治理及生态恢复提供科学依据。     

黄土高原沟壑丘陵区沟道侵蚀与洞穴侵蚀特征

[目的]通过对黄土高原沟壑丘陵区内的沟道侵蚀和洞穴侵蚀进行特征分析,为该地区开展水土保持工作提供数据支持和决策依据。[方法]以王家沟流域为研究对象,通过资料收集、卫星影像识别和现场调查等方法对流域内沟道侵蚀和洞穴侵蚀状况进行分析。[结果](1)流域内共分布718条沟道和948个洞穴。(2)根据空间位置和地形特点将所有沟道分为冲沟、切沟、干沟、河沟。这4类沟道由于受土壤岩性组成、坡度及人为活动等因素影响,空间分布存在巨大差异。(3)43%的洞穴分布在冲沟中,51%分布在切沟中,6%分布在干沟中。河沟中没有洞穴存在。冲沟和切沟是洞穴形成和发育的主要区域。(4)洞穴沟道的沟长、面积、切深、产流及产沙量都明显大于非洞穴沟道。[结论]在黄土高原丘陵沟壑区,洞穴侵蚀是土壤侵蚀的重要组成部分,并对沟道的发育和扩展起着至关重要的作用。     

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