利用阻尼最小二乘法求解Van Genuchten方程参数

土壤水分参数对于定量预报非饱和水流运动是非常重要的，该文运用阻尼最小二乘法。拟合了描述土壤水分特征曲线的Van Genuchten方程参数，同时与非线性单纯性法拟合结果进行了比较，结果表明：该方法拟合精度较高，可以作为计算Van Genuchten方程参数的一种方法。此外。用VB语言编写算法程序，便于对输入数据进行修改。     

基于改进粒子群神经网络的麦田土壤水分反演

作物区土壤水分遥感反演往往受到作物冠层、地表粗糙度等因素影响,较难得到满意的土壤水分反演结果。为解决麦田土壤水分反演的问题,提出一种改进粒子群神经网络优化算法。该算法将多源光学和雷达影像数据进行联合,利用改进粒子群算法对神经网络权值进行优化,建立遥感影像与土壤水分之间一种隐式映射,并将影像数据作为该优化模型的输入变量,对麦田土壤水分进行反演。结果表明改进粒子群神经网络优化算法反演精度高于其他的反演方法,同时主被动遥感联合反演地表土壤水分的精度也比仅使用单一数据源作为输入的方法精度高,R~2达到0.807,RMSE为0.043 cm~3cm~(-3)。由此可见,改进粒子群神经网络的优化方法是可行的,可以有效建立后向散射系数与土壤水分之间的隐式关系,获取较高精度的土壤水分值。该方法可为利用雷达影像数据进行大范围土壤水分估测提供支持。     

垄沟集雨系统Laio土壤水分动态随机模型参数敏感性分析及优化

水文模型参数的敏感性分析、优化和验证对提高模型计算精度和效率具有重要意义。为探讨Laio土壤水分动态随机模型(Laio模型)各参数在垄沟集雨系统的敏感性,同时,确定参数优化和模型验证的最佳方案,本文结合多因素敏感性分析法以及改进单纯形法(ISM)、粒子群优化算法(PSO)和混合粒子群优化算法(HPSO),利用中国气象局定西干旱气象与生态环境试验基地2012—2013年垄沟集雨燕麦生长季降雨、径流和土壤水分等实测数据,对垄沟集雨系统Laio模型的13个参数进行敏感性分析、优化和验证。结果表明,平均降水量α和凋萎系数s_w对土壤水分概率密度函数p(s)最敏感,p(s)对参数α的敏感性在低土壤含水率下更明显,对参数s_w的敏感性在高土壤含水率下更明显;3种算法(ISM、PSO和HPSO)的优化参数值均能对垄沟集雨系统土壤水分概率密度函数进行较好模拟,峰值(CPV)、峰值位置(PP)和95%置信区间(CI95%)实测值与模拟值的相对误差均小于10%,CM指数均大于0.5;同时,HPSO算法优化参数的模拟效果和收敛速度均显著优于PSO算法和ISM算法,能较显著克服ISM算法和PSO算法存在的缺陷。HPSO算法可作为垄沟集雨系统土壤水分动态随机模型参数优化的待选方案。     

基于随机粒子群算法的Van Genuchten方程参数优化求解

使用随机粒子群算法拟合土壤水分特征曲线并以此求解出Van Genuchten方程参数。通过算例与其他优化算法比较，结果表明：随机粒子群算法具有运算速度快，编程简单，初值无关性，全局收敛和计算精度高等优点，可以作为计算Van Genuchten方程参数的新方法。     

基于ANN的复垦土壤水分特征曲线的预测研究

为能较容易且更准确地获取复垦土壤水分特征曲线,将易测定的土壤特性如土壤质地、容重和饱和含水量作为输入变量,采用基于bagging算法的神经网络法建立了用于预测土壤水分特征曲线的土壤转换函数法(PTFs)模型,并对徐州矿区复垦土壤的水分特征曲线进行了预测,同时与普通BP算法预测精度进行了比较.研究结果表明所建立的PTFs参数模型具有较高的估计精度,bagging算法均方根预测误差比普通BP算法减少了7.5%～27.0%,说明该模型的建立与求解为复垦土壤水分特征曲线的预测研究提供了一条新途径.     

基于自适应进化相关向量机的耕地面积预测模型

为解决耕地面积预测模型建立过程中的非线性、稀疏化及结果可靠性评价等问题,该文将相关向量机与差分进化优化算法进行融合及改进,提出基于自适应进化相关向量机的耕地面积预测模型。该文以黄石市为例,建立基于自适应进化相关向量机的短期、中期耕地预测模型,并与多元线性回归、BP神经网络、支持向量机算法在精度、计算效率及可靠性方面进行对比分析。试验验数据表明,自适应进化相关向量机的预测精度大约是其余3种方法的2倍以上;模型的计算效率是多元线性回归方法的2倍,比BP神经网络、支持向量机高出2个数量级;测试数据的实际耕地面积均在自适应进化相关向量机估计的95%置信度的置信区间内,并且由后验差比、小误差概率判定模型等级属于"好"。基于以上数据,证实该模型是一种精度高、计算快、可靠性强的耕地预测新方法。     

科尔沁沙地土壤水分特征曲线传递函数的构建与评估

为了快速准确的获取某一区域的水力性质,该文以科尔沁沙地典型沙丘-草甸相间地区为研究区,在对该区49个不同地貌类型采样点土壤水分特征曲线与土壤基本物理化学特性参数测试分析的基础上,采用函数参数非线性规划法构建了土壤干容重、粒径分布、有机质、pH值、电导率值等基本参数与水分特征曲线之间的传递函数,并进行了精度评估与分析。结果表明:1)研究区土壤水分特征曲线的坡度陡峭,不同地貌类型与土地利用方式下,土壤水分特征曲线有较大差异,相同负压下,土壤持水量按照流动沙丘-半固定沙丘-固定沙丘-农田-草甸的顺序递增;土壤的供水能力按照流动沙丘-半固定沙丘-固定沙丘-草甸-农田的顺序递减;2)利用土壤基本物化特性参数通过函数参数非线性规划法建立了研究区土壤水分特征曲线的传递函数,干容重和砂粒含量是预测土壤水分特征曲线模型参数的主要变量,增加土壤的理化指标可以提高预测精度,然而有机质含量、pH值、电导率值对本区土壤水分常数的影响并不大,对水分特征曲线模型3个参数的影响略微增加;3)通过对传递函数的检验与精度评估分析,各参数的平均误差均在0附近;饱和含水率、残余含水率的均方根误差分别为0.017、0.023;土壤水分常数的相关系数在0.95附近,饱和含水率、残余含水率的误差比的几何标准偏分别为1.04、1.27。表明所建土壤水分特征曲线传递函数的精度较高,可用于该区土壤水分特性研究。该研究可为该区水分、溶质运移、水-热-盐耦合运移模拟提供技术支持和理论保证。     

L波段主被动微波协同反演裸土土壤水分

土壤水分是进行干旱监测、土壤侵蚀、农作物产量预测以及地表温度研究的重要参量,利用主被动微波协同的方法提高土壤水分的反演精度是定量遥感发展所面临的重要任务。本文基于土壤L波段微波散射辐射模拟数据集,通过对比分析主被动微波数据对土壤水分含量和粗糙度2个参数的敏感性,提出了基于L波段主被动协同的裸土土壤水分反演算法,算法充分利用了被动微波地表发射率对土壤水分较为敏感,而主动微波后向散射系数对地表粗糙度较为敏感的特点。首先由地表垂直极化发射率和 VV 极化后向散射系数协同提取地表粗糙度信息,再由被动微波双极化数据结合地表粗糙度信息来估算土壤水分信息。利用SMAPVEX12实验数据集中部分稀疏植被采样点的观测数据对算法进行验证,验证结果显示,土壤水分反演结果与地面实测数据相关性为0.6637,RMSE为0.0607 cm3/cm3。该文反演算法模型系数直接由模拟数据集计算得到,克服了常规经验算法的发展对地表实测数据的依赖性,减小了算法在实际应用中的局限性。     

利用人工神经网络预报不同水分条件下作物根系发育参数

通过对人工神经网络理论的分析,建立了一个能够描述作物根——冠间非线性变化的模拟模型,利用植物地上部参数推求不同水分环境影响的地下根系参数。并通过改进BP算法解决了全局寻优的问题。利用精密的管栽试验为模型提供了足够的学习样本和检验样本。结果表明,该文建立的人工神经网络模型对描述根、冠间复杂的非线性关系方面具有相当高的精度和应用价值     

基于累积分布函数匹配的多源遥感土壤水分数据连续融合算法

数据融合是解决不同来源遥感数据无法直接对比分析这一瓶颈的有效方法。实时更新的SMOS土壤水分数据(soil moisture and ocean salinity)可开展实时干旱评价(2010年至今),但由于序列短无法开展频率及演变分析。CCI(climate change initiative)土壤水分数据是联合了多种主被动遥感数据合成的长序列数据产品(1979—2013年)。为提高不同来源遥感数据的融合精度,该研究基于累积分布匹配原理构建了多源遥感土壤水分连续融合算法,将SMOS和CCI融合成长序列、近实时的遥感土壤水分数据。经验证分析,累积概率曲线相关性中表征干旱的低值区纳什效率系数由0.52提高到0.99,且融合后土壤水分数据可以较准确地反映当地的干旱事件。该研究提出的多源遥感土壤水分连续融合算法显著提高了现有融合算法的融合精度。     

“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.