区域尺度侵蚀产沙估算方法研究

 区域土壤侵蚀模型是大区域土壤侵蚀普查和水土保持宏观决策的支持工具,土壤侵蚀模型的研发是土壤侵蚀学科的前沿领域。基于DEM将区域划分为规则网格,设计产流、产沙过程的单元模型,包括植被截留、入渗、填洼、流速、携沙能力、径流剥蚀量、泥沙沉积等算法。将月降水当作1次降雨事件,并划分若干时段进行迭代计算,利用GIS空间分析功能完成水沙汇集运算,并在ArcGIS支持下进行计算机程序设计,有效地完成了区域侵蚀产沙量的计算。将模型应用于延河流域得到:1995年7月份平均径流深为35.6mm,径流系数为0.237,流域出口径流量为2.72亿m3,流域出口输沙量为0.38亿t,流域平均侵蚀模数为4575t/(km2.月);输出图形空间格局和结构符合实际情况,初步模拟结果令人较满意。     

植被覆盖度和降雨侵蚀力变化对小流域泥沙连通性的影响

泥沙连通性可以反映泥沙源汇的潜在联系,识别流域水土流失热点区域及泥沙迁移路径。研究泥沙连通性的影响因素有助于更好地理解泥沙连通性的时空变化特征。该研究在已有泥沙连通性指数（Index of Connectivity,IC）模型基础上,考虑影响连通性的功能性因素,并采用修正泥沙连通性指数（Revised Index of Sediment Connectivity,ICr）探讨了植被覆盖度和降雨侵蚀力耦合作用下的季节与年际变化对天目湖中田舍河流域泥沙连通性特征的影响。结果表明：2019年夏冬季植被覆盖度分别为85%、57%,对应的泥沙连通性指数均值是-9.39、-6.85,植被覆盖度变化对泥沙连通性具有重要影响,利用NDVI值获取模型中的地表综合系数,可以动态反映地表植被和土地利用的区域及季节性变化;降雨影响泥沙的功能连通性,年尺度上的连通性指数均值同流域泥沙量的相关系数达0.91。说明在流域植被覆盖变化不明显时或者在林地为主的流域中,降雨因子具有主导作用;植被覆盖度升高28%,IC均值降低37%,而单独考虑降雨因子的IC-R均值则反映出雨量升高,指数值随之升高,修正连通性指数ICr综合考虑了植被与降雨因子,但在应用中要依据流域实际情况适当调整两者的权重。研究结果指出泥沙连通性指数在中国东南部区域运用中存在的问题,将对气候变化背景下我国湿润区湖泊小流域水土保持与水环境治理等提供科学参考。     

土壤侵蚀研究的尺度转换

研究对象不同,测试点的代表性、因子匹配和泥沙产生和输移过程的复杂性,尺度对研究结论和方法影响很大。尺度转换对现有小区、坡面和小流域等较小尺度与流域、区域等较大尺度土壤侵蚀资料的应用和印证等研究有着非常重要的意义。影响土壤侵蚀的因子和形式在时间和空间尺度方面应用的适宜程度不同。尺度转换方法主要有主导因子更替法、影响因子尺度转换法和泥沙输移比转换法等,在转换过程中,应结合现有资料和复杂的土壤侵蚀规律加以选择。     

分布式流域产流数学模型的研究

基于流域下垫面各个因子空间分布不均匀的特点 ,开发出一个参数分布式流域产流模型 ,将流域划分为一系列网格单元 ,采用连续方程计算每一网格单元的反映。模型可与地理信息系统连结 ,以获取网格单元的地理信息 ,可视化地显示和分析各单元格的基本情况以及对降雨径流的关系。采用此模型对陕西镇巴县的黑草河小流域进行了模拟 ,模拟结果与实际的洪水过程符合良好。     

大凌河流域水土流失模拟研究

以大凌河流域为例,将改进的通用土壤侵蚀方程与垂向混合产流模型相结合构建水沙耦合模型,并以土地利用、土壤类型、数字高程等流域地理信息数据为基础,运用朝阳水文站2006—2015年水文资料率定和验证了模型参数;为进一步探究流域土壤侵蚀受土地利用变化的影响,利用土壤侵蚀空间模拟结果设定3种土地利用情景模式。研究表明:对于流域水土流失的模拟该模型表现出较好适用性,验证期和率定期内模拟的确定性系数均超过0.50,年含沙量相对误差都低于20%,能够达到泥沙模拟的预期精度;3种土地利用情景模式中草地、林地和旱地面积均增大12.0%,土壤侵蚀模数依次减少6.82%、15.37%、13.40%,为保护流域生态环境、土壤侵蚀现状调查以及合理规划区域经济发展提供科学指导。     

植被恢复背景下土壤侵蚀研究需要加强的内容

植被是调控土壤侵蚀的关键因素,退耕还林(草)工程的有效实施使入黄泥沙锐减,充分证明植被恢复已显著改变了黄土高原的土壤侵蚀环境。但区域侵蚀泥沙的显著减少,仅体现了植被恢复驱动侵蚀泥沙变化的集总效应,无法揭示植被恢复影响土壤侵蚀的过程与动力机制。在黄土高原植被恢复的大背景下,提出了细沟间、细沟、切沟、重力侵蚀需要加强研究的重点内容,明确了新形势下不同侵蚀类型小流域侵蚀泥沙贡献、植被影响土壤侵蚀的参数表征和多时空尺度小流域土壤侵蚀预报模型等方面急需加强的研究内容,旨在揭示植被影响土壤侵蚀的动力学机理,明确植被恢复导致区域侵蚀泥沙锐减的物理机制,确定植被恢复水土保持效应的可持续性,维系区域生态系统服务功能,实现黄河流域生态安全与健康发展。     

羊道沟流域侵蚀产沙模型原型选定问题

侵蚀的空间尺度不同,在建立土壤侵蚀模型时,要考虑由于空间变化所引起的侵蚀因子对侵蚀产沙响应的不同。土壤侵蚀模型在空间尺度上可以划分为坡面、小流域和区域三个不同层次。在坡面尺度上,主要考虑坡面侵蚀的垂直分带性及其相互影响;小流域尺度上,不但考虑坡面侵蚀的特点,还要考虑坡面来水来沙对沟道侵蚀产沙的影响、重力侵蚀及泥沙输移情况;在区域尺度上则主要考虑小流域各自的侵蚀产沙特点及其相互影响。通过分析国内外常用的不同尺度上的侵蚀产沙模型及其最新发展情况,并借鉴羊道沟流域研究的丰富经验,提出了羊道沟流域作为王家沟流域-侵蚀产沙单元的侵蚀产沙概念模型,为流域侵蚀产沙模型尺度之间转换提供借鉴。     

小流域土壤侵蚀动态过程模拟模型

建立流域土壤水蚀预报模型将为小流域综合治理、土地利用规划等宏观决策提供依据，为小流域水土保持效果有效评价提供参考。通过对小流域侵蚀动态过程的分析，在水流连续方程、动量守恒方程及泥沙质量守恒方程基础上，对坡面－沟道及各沟道间土壤侵蚀时空关系进行合理耦合，建立了流域系统土壤侵蚀动态模拟过程模型；采用有限元方法对土壤侵蚀模拟模型进行数值离散，建立了小流域系统数值离散模型；在确定流域时空离散方法基础上，采用VC++语言编制流域水蚀模拟程序；在室内人工模拟降雨条件下，对模型小流域50 mm/h降雨强度，5 min降雨历时情况下土壤侵蚀情况进行模拟，在得到流域内典型点处径流流量、径流含沙量及各沟道流速动态过程的同时，将流域内各沟道出口处模拟结果与测量结果比较，径流流量、径流含沙量、流速模拟精度均高于80%。研究结果表明小流域土壤侵蚀模拟模型的建立是可靠的，模型的数值离散方法及编制的计算程序是完全可行的。这一模型的建立将为小流域土壤侵蚀动态过程的模拟预报及实现由小流域向中大流域的侵蚀动态模拟预报提供一定的理论基础。     

面向地表过程模拟的降雨径流模型开发与应用

降雨径流是流域地表过程的主要驱动力，是众多地表模型的基础。该文在充分考虑流域气象及下垫面等要素空间异质性的基础上，提出了一个面向地表过程模拟的、基于DEM的分布式次降雨径流模型。模型将流域离散为栅格计算单元，并按水流特性将栅格划分为坡面单元和河网单元；模型考虑了降雨、植被截流和入渗等产流过程，利用运动波分级汇流的方式进行汇流演算。模型在江西躁口水流域进行了检验和应用。结果表明：该模型模拟的流量过程精度较高；模拟的径流深度及径流搬运力的空间分布符合水文规律。模型结构简洁、参数较少，具有较好的实用价值；为土壤侵蚀及非点源污染等以流路为基础的复杂地表过程研究奠定了基础。     

小流域水文及土壤侵蚀过程模拟方法研究

流域土壤侵蚀动态模拟,需要采用合适的方法对坡面—沟道耦合问题及初始和边界条件进行正确的处理。将流域划分为坡面侵蚀与沟道侵蚀,采用时间空间耦合处理方法,实现了小流域坡—沟侵蚀过程中水流与泥沙输送的面—线耦合及沟道间的线—线连接。给出了模拟流域土壤侵蚀过程的控制微分方程、初始条件、边界条件及坡面向沟道汇水输沙的动态模拟处理方法。得到了较为符合实际的流域土壤侵蚀动态模拟模型。模拟结果与室内实验测量结果的比较表明,模拟精度达到80%以上,说明了动态模拟方法的可行性。     

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