PRECIS和RegCM3对中国区域气候的长期模拟比较

以欧洲中期天气预报中心的再分析资料(ERA40)为侧边界及初始条件,在相同模拟区域和分辨率设置下,完成了PRECIS和RegCM3两个区域气候模式对中国区域近44a(1958年12月-2001年11月)的气候模拟,并分析比较两个模式对中国区域温度和降水的气候态和年际变率的模拟能力。结果表明,PRECIS和RegCM3均能较好地模拟出中国区域多年平均气温的空间分布特征,但PRECIS比观测气温平均偏暖1.5℃左右,而RegCM3则以冷偏差为主,平均偏低0.8℃左右,PRECIS整体上比RegCM3偏高2～3℃;两个模式均可基本再现气温年际变率的分布特征,但变率中心的位置和强度与观测值存在一定偏差;对于中国区域降水量的平均态及其年际变率而言,PRECIS和RegCM3均具有较好的模拟能力,但PRECIS模拟的降水高值中心、变率较大区域的位置和强度比RegCM3更接近实际。     

PRECIS模拟区域的选择对宁夏区域气候模拟效果的敏感性分析

选定4种大小不同的模拟区域设置25km水平分辨率的PRECIS系统于宁夏地区,利用欧洲中期天气预报中心(ECWMF)1978年12月-1979年9月的再分析数据作为准观测边界条件驱动PRECIS,通过模拟的宁夏地区冬夏两季日平均气温和降水与观测资料的对比,分析25km水平分辨率气候模拟结果对模式区域选择的敏感性。结果表明:25km水平分辨率的PRECIS在4种不同模拟区域下都能较好地模拟宁夏地区典型年的日平均温度和降水量,尤其是对降水的模拟效果更好;总体上,PRECIS的模拟效果随着模拟区域的缩小而下降,但PRECIS在中小模拟区域下仍然能够获得较好的模拟效果。考虑到计算成本,本研究认为在中小模拟区域下25km水平分辨率的PRECIS能够较为高效地进行宁夏地区的气候模拟。     

SRES A1B情景下未来宁夏玉米生育期气候资源变化分析

玉米是宁夏的三大粮食作物之一,其种植分布广泛,中部干旱带和南部山区基本属于雨养玉米区,气候条件对当地的玉米生产影响很大。观测到的气候变化已经对当地农业造成不利影响,未来SRES A2和B2情景下宁夏地区的气候变化研究也有一定成果。由于气候变化引发宁夏的气温和降水出现异常,为分析未来中等排放情景下气候变化可能对当地玉米生产造成的影响,本文利用订正后的英国Hadley气候中心区域气候模式PRECIS模拟的情景数据,分析了SRES A1B情景下宁夏未来2020s、2050s和2080s时段相对于气候基准时段(1961—1990年)的玉米生育期(4—9月)平均气温、最高气温、最低气温、≥10℃有效积温和降水的变化,具体方法为先分析气候基准时段宁夏的气候要素分布并与实际状况进行比较,再将未来3个时段的气象要素与气候基准时段求差值(其中降水用距平百分率表示),分析未来玉米生育期的气候变化。结果表明:平均、最高和最低气温以及≥10℃有效积温的模拟值普遍低于实际值,且具有相似的北高南低的空间分布状态,而降水的模拟值在大范围区域内高于实测值,亦呈现出相似的南高北低分布状态,总体来讲模拟值可以较合理地反映出宁夏的实际状况。相对于气候基准时段,未来各气象要素总体表现为增加,且增幅随时间推移而加大;未来最高气温在宁夏南部增加剧烈,平均气温、最低气温和≥10℃有效积温在宁夏北部增加较多,降水则呈现北增南减的分布。在未来3个时段,最高气温和降水分别为增量最大和波动最大的气象要素,出现极端高温天气和发生干旱或洪涝等异常气候事件的可能性增大。总体上看,未来气温升高对宁夏北部灌区的玉米生产有一定促进作用,尤其是≥10℃有效积温的增加可以提供更充足的热量;而南部山区气温增加虽然对玉米生产有利,但是未来降水的减少将会给雨养玉米造成不利影响,应当采取合理的应对措施。     

SRES A2、B2情景下宁夏地区日较差、夏季日数及霜冻日数变化的初步分析

利用Hadley气候预测与研究中心的区域气候模式系统PRECIS（Providing Regional Climate for ImpactsStudies）进行宁夏地区SRES A2、B2情景下2071-2100年（2080s时段）日较差、夏季日数及霜冻日数变化响应的初步分析。将ECMWF1979-1993年的再分析数据（ERA15）作为边界条件驱动PRECIS模拟宁夏地区的日较差、夏季日数及霜冻日数。模拟值与台站实际观测资料进行的对比分析表明,PRECIS能够模拟出宁夏地区这些极端指标的空间分布差异和年际变化,总体上来说,日较差、夏季日数模拟值偏大,南部地区霜冻日数的模拟值偏小。3个极端指标气候基准时段（1961-1990年）的模拟频率和观测频率的对比分析表明,PRECIS能够模拟出极端指标的频率分布。另外,用观测数据对模式数据进行了订正,经验证,订正后的值与观测值的吻合程度明显提高。相对于Baseline,SRES A2、B2情景下2080s宁夏大部地区的日较差将减少;夏季日数将增加,两种情景下平均每年增量分别可达69d和48d;而霜冻日数将减少,两种情景下平均每年减少量分别可达50d和36d。     

不同林型对小流域气象效应的影响

采用大区平行对比观测试验方法，对御路的小流域不同部位，不同林型（纯林和混交林）的太阳辐射，有效辐射和林内总辐射，地面最高温度，地面最低温度，水分条件及风速等气象参数进行了观测，分析结果表明：混交林的气象效应好于纯林， 混交林构成的复层结构能较多利用和贮存太阳能，减少辐射量，缓和极端温度，缩小温度日较差，并且混交林在降低风速，改善水分条件方面也优于纯林。     

区域气候模式PRECIS对中国气候的长期数值模拟试验

利用欧洲中心ERA40再分析资料驱动区域气候模式PRECIS,对中国地区进行了50km水平分辨率、40a(1961-2000年)时间长度的连续积分,并对模拟的温度和降水与观测资料进行了比较分析。结果表明:模式对中国地区温度和降水的年、季空间分布型态均具有一定的模拟能力,对温度和降水的年际变化也有较好的模拟效果,尤其对于20世纪80年代后期出现的暖冬以及1998年的夏季极端降水都有较好的体现。但模式不足在于区域内普遍存在模拟的气温略高于实况的系统性暖偏差,幅度一般在1~3℃;内蒙古和东北地区年降水量比观测值明显偏多,长江以南地区和四川盆地的降水中心范围都明显偏大,位置偏南。总体来看,无论是空间分布还是年际变化,模式对温度的模拟能力明显优于降水。     

贺兰山油松林冠层的辐射能量截获及传输利用特征

油松作为我国北方地区典型的森林植被类型,研究辐射能量在其冠层中的分配、收支及传输,是构建森林冠层辐射传输模型和生态过程模型的理论基础,对阐明森林植被群落中能量流动和物质循环机理具有重要意义。基于贺兰山生态站油松林通量塔定位观测获取的上、下行长短波辐射、光合有效辐射(photosynthetically active radiation, PAR)以及气象数据,分析2021年4—9月不同天气和季节条件下油松林冠层的辐射能量截获及传输特征。结果表明：(1)晴天条件下太阳总辐射的日变化表现为光滑的“单峰”曲线,但多云条件下则呈现不规则的“多峰”曲线,且减弱48.3%的太阳总辐射能量到达冠层顶部。(2)太阳总辐射以下行短波辐射为主,晴天的上行短波辐射日变化虽也呈“单峰”形态,但仅占下行短波辐射的8.1%,上行和下行长波辐射随昼夜交替略有波动。(3)太阳短波辐射的季节动态特征表明,上行和下行短波辐射在6月最高,而上行和下行长波辐射在7月最高。(4)在冠层上方(25 m处)呈规则“单峰”形态的PAR日动态曲线,经过冠层截获和传输作用后,在冠层下方(7 m处)变为不规则曲线;PAR的透过率为32.2...     

日光温室内太阳辐射估算模型的构建

日光温室内不同位置的太阳辐射量是作物光合和蒸腾模拟模型的重要参数,也是研究温室内墙体能量收支平衡方程的重要因子。该文研究了温室围护结构对太阳辐射的遮蔽,建立了可蔽视角的计算公式,在此基础上估算了晴天温室内任一位置的太阳直接辐射、散射辐射和太阳总辐射,并以辽沈Ⅱ型日光温室为例,将模拟结果与实测结果进行了比较,对造成模拟误差的可能原因进行了分析。研究结果表明:日光温室内模拟的散射辐射和总辐射的日变化与实测值趋势较为一致,模拟值要略高于实测值,平均偏高6.4%和8.8%,误差的可能来源有大气透明系数、棚膜透光率的估算误差、承重骨架的遮蔽及人为观测的误差。研究结果可为日光温室内不同位置作物光合蒸腾模拟、群体光分布模拟、围护结构能量平衡等模拟模型提供参考。     

基于格网的GCM数据修订分析未来海南岛农业水热资源的变化特征

以海南岛为研究区域，选用5个大气环流模式（GCMs）1970−1999年的逐日输出数据和同期地面气象观测数据，使用空间插值降尺度到0.5°×0.5°格网。以格网单元为基础，应用系统误差修订（修正值法或比值法）和多模式集合平均方法（贝叶斯模型平均法BMA或等权重平均法EW），训练与验证GCMs输出值并进行综合修订。在此基础上，分析RCP2.6、RCP4.5和RCP8.5情景下，未来海南岛近期（2020−2059年）和远期（2060−2099年）农业水热资源，包括年平均气温、1月平均气温、≥10℃积温、≥20℃积温、年降水量、1月降水量和≥20℃界限温度生长期间降水量的变化特征。结果表明：GCMs输出值的系统误差和BMA权重系数在格网间存在较大的空间差异，且GCMs输出值低估逐日最高气温约3.55℃，高估逐日最低气温约1.19℃，逐日降水量仅为观测值的54.35%。基于格网的综合修订，可有效降低GCMs输出值在空间上的不确定性，BMA与EW的修订结果相似，均优于单一GCM模式。通过格网BMA综合修订后，最高气温、最低气温和降水量在验证期的相关系数r分别约提升0.10、0.07和0.06；均方根误差RMSE分别约降低2.38℃、1.01℃和1.01mm；较单一GCM相对观测值的偏差平均约减少3.25℃、1.13℃和25.67mm。未来海南岛农业热量资源在空间上主要表现为从中部向外围逐渐升高，高温主要分布在南部至西部沿海地区，年平均气温的增幅全岛较为接近，1月平均气温、≥10℃积温和≥20℃积温的增幅分别表现为由东向西、由北向南和由中部向外围递减。在时间上，RCP8.5情景下所有农业热量资源均为极显著增加且增温最快，RCP4.5情景为先增加后平缓，RCP2.6情景较为平缓，远期无显著增温。未来海南岛降水资源在空间上转为由东向西逐步递减的格局，南部和北部沿海地区降水变率增加，西部和中部降水变率减少，在时间上无显著变化趋势。随着未来海南岛气候变暖和降水格局的改变，农作物适宜种植面积扩大，会对农业生产带来巨大挑战，应提前布局，做好趋利避害。     

CMIP5全球气候模式统计降尺度数据对辽宁省极端气温模拟能力评估

利用1971−2010年辽宁地区32个气象台站观测资料,采用SS指标和M2指标,评估CMIP5气候预估降尺度数据集中31个模式对辽宁省全年和4个季节极端气温指数时空变化特征的模拟能力,并经MR综合评级,筛选模拟效果最好的模式。极端温度指数选用平均最高气温（TXm）、平均最低气温（TNm）、霜冻日数（FD0）、夏日日数（SU25）、最低气温极小值（TNn）、最高气温极大值（TXx）和极端气温范围（ETR）。结果表明：对单一极端气温指数而言,所有模式对表征气温平均特征的指数模拟效果较好,对表征连续极端气温事件的指数模拟效果一般,而对气温的极端特征模拟能力不足。由于模式对全年、各季节各极端气温指数的排名无一致性,引入MR评级指标进行排序,优选的3个模式为MPI-ESM-LR、GFDL-ESM2M和MIROC-ESM-CHEM。比较发现,优选模式集合平均结果相对于观测值的误差百分率整体上明显优于所有模式的集合平均结果,具有可用性。研究结果可为预估未来区域极端气温提供理论参考,建立的逐日模式资料可为开展辽宁农业气象灾害风险相关研究提供数据支撑。     

“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     

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.     

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.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Leaf litter selection by detritivore and geophagous earthworms

Summary Litterbag experiments with 10 different kinds of leaf litter showed that detritivore (Lumbricus species) and geophagous (Aporrectodea species) earthworms prefer certain litter types over others, since different numbers of worms were found below the litter after 50–52 days of exposure in a pasture. The detritivores preferred Fraxinus, Tilia, and predecomposed Ulmus and Fagus litter to Fagus litter and paper, while geophages preferred Tilia litter to Alnus and Ulmus litter, so that the two groups of earthworms showed different preferences. The detritivores seemed to be more selective than the geophages. The palatability of the litter was examined in relation to the C: N ratio, the lignin concentration and the initial and final polyphenol concentration. The numbers of detritivores were significantly correlated with the C: N ratio and the final polyphenol concentration, so that selection of litter seems to be related to palatability. The numbers of geophages were not significantly correlated with any of the parameters for palatability. The disappearance of litter after 50–52 days appeared to be due to detritivore activity, since the numbers found below the litter were positively and significantly correlated with the litter disappearance. There was no significant correlation with geophage activity. This indicates that detritivores use litter as food, and therefore influence the composition of the litter layer.     

Nematode succession and microfauna-microorganism interactions during root residue decomposition

The quality of plant material affects the vigor of the decomposition process and composition of the decomposer biota. Root residues from hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and vetch+rye, packed in litterbags were placed in pots of soil at 15 C and the content of the bags was analyzed after 2, 4, 8 and 12 weeks. Bacterial biomass did not differ between residues with contrasting composition. Among bacterivores groups of nematodes that require high bacterial production dominated in fast decomposing resources whereas flagellates with smaller requirements prevail in slower decomposing resources. Biomass of bacterial feeding nematodes correlated positively with early phase (0-2 wk) decomposition that increased in the order: rye< vetch+rye<vetch. Bacterial biomass therefore seems to be under top-down (predation) control during early decomposition. In contrast, the fungal biomass differed between resources with highest values for rye. Moreover, this increase in fungal biomass occurred later during succession and was correlated with decomposition activity for rye in that period. Fungal biomass therefore seems to be under bottom-up (resource) control. The composition of the nematode assemblages (composed of 25 taxa) showed a clear relationship to initial plant resource quality as well as decomposition phase. Early successional microbivorous nematodes vary according to resource quality with demanding bacterivores+predators (Neodiplogasteridae) dominating in vetch and less demanding bacterivores (Rhabditidae) and fungivores (Aphelenchus) being equally common in vetch and rye. Later in the succession (2-4 wk) bacterivorous Cephalobidae and fungivorous Aphelenchoides prevailed similarly on the different root materials whereas bacterivorous protozoa and the amoebal fraction thereof dominated in rye. At week 12 no species dominated the nematode assemblages that were similar between the resources. The differences between nematode assemblages among plant resources at 2 week were similar to the results of a field study sampled after 6 weeks with the same soil and plant resources. This lends support to the relevance of the successional patterns observed in this incubation study.     

Cycling of extracellular DNA in the soil environment

Upon entering the soil environment, extracellular DNA is subjected to dynamic biological, physical, and chemical factors that determine its fate. This review concerns the fate of both recombinant and non-recombinant sources of DNA. A schematic of DNA cycling coupled with genetic transformation is presented to understand its behavior in soil. Extracellular DNA may persist through cation bridging onto soil minerals and humic substances, be enzymatically degraded and restricted by DNases of microbial origin, and/or enter the microbial DNA cycle through natural transformation of competent bacteria. Lateral gene transfer may disseminate DNA through the microbial community. An understanding of DNA cycling is fundamental to elucidating the fate of extracellular DNA in the soil environment.