黄土高原汛期降水年代际演变

利用黄土高原区域40a的降水资料，研究汛期降水年代际演变。结果表明，黄土高原汛期旱涝交错的变化幅度不断减小；降水带南移雨量带南移。20世纪80年代较60年代南移0.6个纬度，90年代南移约1．8个纬度（高原东部地区南移4个纬度）。前3个模态演变的转折（突变）时间和显著程度不同，但其振荡强度和周期的阶段性与降水对应较好。多雨期降水变幅大，周期短，振荡强。少雨期对应多周期，弱振荡。降水异常的敏感区年代际变动明显，演化路径基本由东北向西南移动，高原西部旱涝灾害趋向频繁。     

淮河流域汛期候尺度降水集中度与集中期的时序变化特征

降水分布的不均匀性特征是水循环研究的热点问题,也是区域旱涝防灾与水资源利用的重要依据。基于淮河流域30个气象测站点1960-2014年汛期（5-8月）的逐日降水数据,采用降水集中度指标、趋势与突变检测以及小波周期方法,分析了淮河流域近55 a来汛期降水集中特性的时序变化特征。结果表明:（1）汛期降水年际间波动频繁,变幅较大,1970s和1990s为汛期雨量偏低时期,而2000s以来是汛期降水量最高的时代。（2）降水集中度波动较大,呈微弱减小趋势,以1960s为最集中,1980s最低,1983年出现一次较为明显的突变过程。多年平均降水集中期出现于7月上旬的38候;集中期以1980s为最偏早,1990s以来都较为偏迟,在1990年为明显的突变过程,此后集中期总体推后。（3）集中度在1960s中期具有2 a左右的周期,在1991-2004年存在3~5 a左右的周期。集中期在1970s后段存在2 a左右短周期,而在1970-1982年存在显著的6~9 a左右稍长周期。集中度与集中期在1975-1985年还具有显著的4~5 a左右正相位共振周期。     

近50年浙西南汛期旱涝变化及特征

通过对浙西南汛期降水资料的分析,引用降水指数建立了浙西南旱涝序列,根据当地汛期特点将汛期分为前汛期和台汛期。分析结果表明,浙西南汛期和前汛期降水总量表现出明显的减少趋势,而台汛期具有弱的增加趋势。汛期旱涝变化具有明显的年际特征,从上世纪50年代以来到70年代末浙西南汛期雨水趋少,从80年代到90年代末雨水增多,到了21世纪初又有减少的趋势。因此在上世纪50年代以及90年代是涝灾多发时段,而70年代中期到80年代中期是一个旱灾多发时段,进入21世纪后汛期降雨量又迅速的减少,旱灾发生渐频。另外浙西南旱涝序列还有一定的周期性,前汛期、台汛期以及汛期的旱涝周期分别是6～7 a、2～3 a、26 a。     

江苏沿海开发地区近50年来降水演变特征与趋势

利用1960—2009年10个代表气象站降水资料,采用多方法分析了江苏沿海开发地区的降水特征与趋势。结果表明:年降水量波动频繁,南部较北部略偏多,盐城波动幅最大,南通最小;其年代变化上,南通为持续增加趋势,盐城以1960s降水量最多,其后大幅减少,而连云港则总体偏低,且年代际变幅最大。汛期降水量上,沿海北部较南部偏大,波动幅度与年降水量类似;汛期降水年代变化上,南通总体仍呈增加趋势;而盐城则总体减少,以1970s最低;连云港以1980s为最低值,此前偏高,此后略有增加。2000年以来的旱涝波动更为频繁,并以涝为主。近50a来南通、盐城的年降水呈较弱的减小趋势,连云港则呈增加趋势,而汛期降水量的变化趋势则与年降水量相反。未来趋势上,南通、盐城、连云港的年降水量仍将分别呈现减少、减少、增加的趋势,汛期降水量也仍将分别表现为增加、增加、减少的趋势。     

基于M-K法的朝阳市降水量时空演变特征分析

以朝阳地区77个降水站点1963—2016年实测降水数据,应用M-K非线性统计方法对朝阳市近54a降水量时空变化特征进行了分析。分析结果表明:从1963~2016年朝阳市年降水量略微下降,下降趋势不显著,M-K统计值为-0.7684,未通过90%的显著性检验,年降水量突变点分布出现在1965年、1976年、1984年;汛期降水量呈现下降趋势,非汛期降水量则呈现上升趋势,M-K统计值分别为-1.1652和1.037,也均未能通过90%的显著性检验,汛期降水量突变年份和年降水量突变年份一致,非汛期降水突变点分别出现在1991年和2005年。朝阳市各年代际降水总体呈现南部大北部偏小的分布趋势,从1980年代开始,朝阳市降水量空间分布呈现较为明显的10 a丰、枯变化趋势。研究成果对于朝阳市水资源量的定量评估提供参考价值。     

1970-2019年河南省年内降水分配非均匀性的时空演变

[目的] 分析河南省年内降水分配非均匀性的时空演变规律,为区域水资源管理提供依据。[方法] 依托河南省113个气象站1970—2019年逐月降水数据,评估了降水季节性指数（PSI）的时空变化。[结果] ①PSI的空间分布表明河南省北部呈现出较高的降水非均匀性,超过28%的降水集中在7月;②基于主成分分析,河南省可以划分为4个呈现不同PSI演变特征的子区域,分别为西部、中东部、北部、南部;③西部、中东部、及南部地区的PSI在1990年后呈现出一定的上升趋势,而北部地区PSI呈现出更为强烈的短期振荡;④河南省大部分地区PSI的年代际变化主要受厄尔尼诺/南方涛动（ENSO）影响;⑤与其他粮油作物相比,冬小麦产量的年际波动对PSI更为敏感。[结论] 河南省年内降水分配的时空变异性较强,其与大尺度环流信号的相关性存在显著的区域差异。     

西北地区夏季降水的气候特征分析

利用西北地区119站1961-2000年夏季（6-8月）降水资料，统计分析了各站历年夏季降水的平均场、方差场和各年代际平均值分布特征与整体总量逐年平均值的年际和周期变化特点，结果表明：西北地区夏季降水可划分为3个基本气候分区，即北疆区、中西部盆地沙漠区和东部季风影响区。中西部盆地沙漠区降水量和降水量方差均最小，处于稳定的干旱状态；东部季风影响区降水量的方差变化较大，降水的不稳定性增加，干旱频率增大；北疆区降水量较大，变差处于另外两区之间，表明旱涝影响微弱。各区的降水量在不同年代际间也具有不同的特点，降水量的变化会直接影响到当地主要旱地作物的产量。     

黄土丘陵沟壑区罗玉沟流域水沙特性分析

依据罗玉沟流域1986—2010年降水、径流、泥沙观测资料,采用统计学原理,分析研究了流域降水、径流、泥沙特征及其相关关系。罗玉沟流域多年平均降水量552.5 mm,降水年际、年内变化大,时空分布不均;多年平均径流量201.33万m3,多集中在汛期;多年平均输沙量33.83万t,沙量集中在汛期;年降水量与年径流量、汛期降水量与年产沙量、次平均降水量与次洪水输沙量相关性较好,年径流量与年输沙量具有较好的线性相关关系。     

典型峰丛洼地坡面土壤水分动态变化的时序分析

采用时间序列分析方法，分析了2004年5～9月广西环江典型峰丛洼地坡面上6种土地覆被类型10，20cm土壤水势与降水动态变化的相关关系。结果表明：（1）灌丛与板栗覆草土壤中的水分较充裕，其含量受天气的波动变化较小，对降水的影响具有缓效性、长期性的特点；（2）坡耕地中水分含量较低，随降雨的波动变化剧烈，但南瓜的地上植株部分对土壤水分的调节保持有积极作用；（3）撂荒草地与木豆土壤水分含量的层间差异都较显著，对降水响应的即时性也强，但撂荒地20cm土层对降水的响应期长些，能保证短时间内向10cm土层的水分补给；（4）处于幼龄期的板栗，土壤水分变化反映的是仅受天气影响下的自然裸露坡地的状况，变化介于灌丛、板栗覆草和撂荒草地、木豆之间。     

川渝地区汛期逐小时降水融合产品误差分析

利用2021年汛期三套降水融合产品CMPAS、GSMaP和IMERG，经质量控制后的川渝地区190个国家气象站逐小时降水数据，结合川渝地区的不同地形区间和不同小时雨强对三套融合产品进行误差分析。结果表明：（1）2021年汛期总降水量空间分布上，CMPAS产品与站点实测最为接近，其次依次为GSMaP、IMERG产品。（2）针对不同地形区、不同时段，CMPAS产品的相关性、命中率、关键成功率最优，IMERG次之；CMPAS产品的偏差、均方根误差、误报率最小，GSMaP产品的误报率最大，IMERG的偏差、均方根误差最大；各融合产品在8月和9月的命中率、关键成功率最优，在20:00-次日2:00、2:00-8:00的相关性、命中率、关键成功率最优，误差和误报率最小。（3）针对不同小时雨强，CMPAS明显优于IMERG和GSMaP产品；其中CMPAS产品5月和9月的相关性、命中率、关键成功率最优；当小时雨强增大时，各融合产品的均方根误差逐渐增大。研究结果说明汛期CMPAS产品在川渝地区的精度明显优于IMERG和GSMa P产品，可以为地面实测数据缺乏的地区提供有效的降水数据补充。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

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 from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

Responses of native legume desert trees used for reforestation in the Sonoran Desert to plant growth-promoting microorganisms in screen house

Three slow-growing legume trees used for desert reforestation and urban gardening in the Sonoran Desert of Northwestern Mexico and the Southwestern USA were evaluated whether their growth can be promoted by inoculation with plant growth-promoting bacteria (Azospirillum brasilense and Bacillus pumilus), unidentified arbuscular mycorrhizal (AM) fungi (mainly Glomus sp.), and supplementation with common compost under regular screenhouse cultivation common to these trees in nurseries. Mesquite amargo (Prosopis articulata) and yellow palo verde (Parkinsonia microphylla) had different positive responses to several of the parameters tested while blue palo verde (Parkinsonia florida) did not respond. Survival of all tree species was over 80% and survival of mesquite was almost 100% after 10 months of cultivation. Inoculation with growth-promoting microorganisms induced significant effects on the leaf gas exchange of these trees, measured as transpiration and diffusive resistance, when these trees were cultivated without water restrictions.