国道112线丰宁县城至千松梁段扩建对水土流失的影响及对策

国道 112线丰宁段处于半湿润半干旱的气候条件下 ,当地植被覆盖率低 ,土壤为黄土质母质 ,结构松散 ,黏结力差。该段公路长 5 8 4km ,路线宽度从 6～ 8m扩建为 12m。公路建设只在一定时期内对水土流失有影响 ,且不同部分影响时间不同 ,确定各部分的影响时间为路面 1a ,取土场、弃土场和路基边坡为 5a,临时占地为 3a。根据不同地貌条件下侵蚀模数、面积等计算的原地貌条件下的水土流失量为 748 0t,影响期内的年水土流失量为 145 6 1t。由公路建设引起的水土流失量为 70 8 1t。主要是由于弃土场和公路边坡引起。减轻水土流失的措施对弃土场修建挡渣墙整理后种草植树。对路边坡进行植物护坡     

建设项目中弃土场的水土流失状况

以绥满公路海林至亚布力段的弃土场为研究对象,通过观测降雨、土壤、植物和水土流失量的因子,研究弃土场的水土流失状况。弃土场表土物质组成对水土流失起着重要作用,表土受雨水冲刷,砾石含量逐渐增大,水土流失量逐渐减小;降雨侵蚀力与降雨造成的单位面积水土流失量之间,表现出较好的一元线性正相关关系,在不考虑影响坡面水土流失的其他因素的前提下,随着降雨侵蚀力的增大,水土流失量将加大;采取工程措施和植物措施综合防护,可以有效减少弃土场的水土流失量。     

高速公路植物措施保土效益初探——以云南省安宁至楚雄段为例

以云南省安宁至楚雄段高速公路为对象,初步研究该段公路边坡和弃土场的水土流失现状和植物防治措施种类及其布局.结果表明在公路边坡宜采用草灌混播方式,弃土场则在削坡开级和修建挡渣墙的前提下,种植坡柳或迎春花.通过在典型地段采用综合调查获取的数据分析研究,植物盖度在70%以上的公路边坡,基本上无鳞片状面蚀发生.在弃土场,由于坡面与堆渣体植被退化严重,发生不同程度的面蚀与沟蚀.经现场量测,其土壤侵蚀量为8090.4 t/km2(3 a时间),土壤侵蚀模数为2 696.8 t/(km2·a).高速公路两侧采取植物措施后既可防治水土流失,又可美化道路环境,保障行车安全.     

浦南高速公路建设水土流失特点与防治措施

通过对浦南高速公路建设过程中水土流失特点的分析,按主体工程区、取弃土场区、临时工程区分别采取相应的防治措施,坚持水土保持“三同时”制度,就能够有效减少公路建设所造成的水土流失量。     

高速公路弃土场的水土流失监测及其生态治理

高速公路弃土场边坡的生态治理是公路建设环境保护的重要内容。在京珠高速公路粤境南段弃土场开展水土流失监测研究,探讨了弃土场的水土流失及其生态治理的水土保持效果。结果表明,弃土场水土流失剧烈,侵蚀模数平均为3.24×10^4t/（km^2·a）,边坡沟蚀现象明显。采用香根草（Vetiveria zizaniodes）生态护坡技术治理弃土场边坡水土流失,水土保持效果显著,坡面土壤流失量比对照小区减少92.24%,边坡稳定,在一定程度上可代替浆砌片石骨架植草护坡措施。因此,高速公路弃土场的水土流失生态治理可大力推广应用香根草生态护坡技术。     

云南省公路水土流失量的监测方法

[目的]分析云南省公路上常用的水土流失量监测方法,为云南省公路建设期间水土保持措施的布设及防治措施效益的计算提供准确依据。[方法]采用划分不同的地形地貌单元对公路进行水土流失量监测的方法,以云南省元江至红河二级公路元江段为例,在同等监测条件下,进行了常规监测方法和该监测方法的对比监测。[结果]采用常规监测方法获得公路建设期间的水土流失量为102 058t,采用监测方法所得的水土流失量为56 378t,在对监测结果分析的基础上,可知采用该水土流失量监测方法的精度更高。[结论]采用划分不同的地形地貌单元对公路进行水土流失量监测,可更好体现云南省公路建设期间水土流失发生的特点。     

高速公路弃土场边坡沟蚀规律研究——以湖北沪蓉西高速公路为例

为探讨公路弃土场边坡沟蚀发生发展规律,以湖北沪蓉西高速公路(宜长段)为例,从弃土场沟蚀发育特征、发生发展规律和与沟间侵蚀的关系3方面对弃土场沟蚀规律进行探讨.结果表明,弃土场边坡沟蚀与降雨有密切的关系,沟蚀在坡面土壤侵蚀量占的比重越来越大;弃土场坡面沟蚀发展呈加剧发展趋势,随着观测时间的变化,细沟侵蚀在整个坡面土壤侵蚀量中占的比重越来越小,而相对浅沟侵蚀和切沟侵蚀所占的比重越来越大.     

公路建设中受损生态区域恢复技术

公路工程建设对地面的扰动面积很大,施工期间将进行大量的路基开挖和土方取弃活动,对沿线生态环境影响很大,尤其在取、弃土场等受损生态敏感区域影响更为严重。从保护公路沿线生态环境、水土资源、减少水土流失的角度出发,针对公路建设中取、弃土场特定的受损生态区域特点,并结合"黄祁高速公路工程"典型取、弃土场受损生态区域防治措施设计案例,探讨了目前公路建设中常用的相关恢复技术措施。     

计算机模拟模型在黄土丘陵区土地可持续利用中的实证研究

针对黄土丘陵区的土地可持续利用问题，引入目前国际上较先进的水土流失与土地利用规划模型APEX和AV-SWAT，利用GIS技术及陕北安塞县纸坊沟小流域定位站多年的连续观测资料，对模型在黄土丘陵区的适用性进行了初步验证。通过对该类型地区的水土流失量、作物产量、植被生物量等方面的测算，结果表明模型模拟计算的水土流失量与实际观测量的误差小于10%，5年加权平均的作物模拟产量与实测值的差异不显著。从而为该类型区土地可持续利用方法论提供了新的计算工具，也使得更大尺度上的土地可持续利用设计成为可能。     

黄土高原公路弃土场侵蚀规律及其模拟研究

公路弃土场是道路侵蚀的重要单元之一,对其土壤侵蚀机理的研究与模拟是完善道路侵蚀模型、准确预测流域产沙量的基础。通过不同雨强(0.6~2.79 mm/min)的人工降雨实验对不同坡度(19.4%~78.1%)的弃土场坡面及坡度为30.6%的弃土场施工道路的土壤侵蚀规律进行了研究,并提出了弃土场土壤侵蚀预报方法。结果表明:弃土场土壤侵蚀速率与雨强呈较好的幂函数关系;小雨强下容重与侵蚀速率呈正相关,大雨强下容重与侵蚀速率呈负相关;弃土场坡面侵蚀量与坡度呈正相关,但侵蚀量随坡度的变化趋势与陡坡耕地有较大差异;使用EI30、容重及坡度等因子可以较好地预测弃土场土壤侵蚀量。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

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.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

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.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.