人工降雨条件下黄土坡面养分随径流迁移试验

降雨条件下坡面农用化合物随地表径流迁移既是农业问题,又是水环境问题。利用室内人工降雨模拟试验,研究了黄土坡面不同坡度下土壤氮、磷和钾随地表径流迁移的特征。研究结果表明,在定坡长土槽坡度变化为5°～25°范围内,初始产流时间随坡度增大呈先变小后增大的趋势;产流15 min内,径流量均急剧增加,随后趋于稳定。随着坡度增加,水土流失程度加剧,径流溶质浓度增高,土壤侵蚀对径流溶质浓度的贡献增大。基于指数函数和幂函数拟合试验数据的结果,表明了幂函数模型更适合模拟黄土坡面非饱和条件下径流溶质浓度变化过程,也可描述径流磷和钾的流失过程,但其初始阶段的拟合不太令人满意。该研究为进一步完善黄土坡面径流养分迁移模拟模型提供了参考。     

黄土坡面不同植被覆盖度下产流产沙与养分流失规律

植被与降水是决定坡面产流产沙及养分流失的主要因素,为探求植被覆盖度对土壤侵蚀和养分流失的影响,采用野外黄土坡面放水冲刷试验,在30L/min冲刷流量条件下,对不同苜蓿覆盖度下黄土坡面的径流量、产沙量和养分流失量进行研究。结果表明:当植被覆盖度分别为0%,33.5%,43.2%和68.8%时,坡面径流量分别为693.35,362.51,324.65,266.64L;产沙量分别为16.3,5.9,0.16,0.091kg;溴离子流失量分别为5 852.07,1 274.51,397.29,178.56mg。利用幂函数对径流溶质浓度变化过程进行拟合,结果显示幂函数可以很好地反映田间坡面溶质随地表径流变化过程,为进一步描述径流溶质变化过程的数学模型提供指导。平均坡面糙率能够反映土壤侵蚀量的变化。植被覆盖度增加使得平均坡面糙率增大,从而减小了土壤侵蚀量和养分流失量。     

表层土壤容重对黄土坡面养分随径流迁移的影响

农田化学物质随地表径流迁移的问题,既是农业问题,又是水环境问题。地表土壤容重是影响土壤溶质随径流迁移的重要因素之一。通过室内模拟试验,研究了降雨条件下土壤容重对黄土区坡面土壤氮、磷和钾随径流迁移过程的影响。结果表明,随着土壤容重增大,初始产流时间提早,径流系数增大,土壤流失量增多,土壤磷和钾流失量也随之增大。径流养分浓度变化对土壤容重响应程度的大小次序是：NO3ˉ-N〉PO4^3-P〉K^＋。径流养分流失率过程曲线存在“峰值点”,它是土壤容重、溶质理化特性以及土壤水文参数综合作用的结果。通过数学模拟,进一步证实了幂函数是模拟黄土区非饱和水流条件下养分流失过程的最佳模型。本研究为深入理解黄土坡面径流溶质迁移机理提供了参考。     

不同坡度坡耕地土壤氮磷的流失与迁移过程

采用人工模拟降雨试验研究不同坡度的土壤侵蚀程度,分析了土壤养分在不同坡度(5°,10°,15°,20°,25°)随坡面径流流失及水分入渗向下迁移的动态变化过程和机制。结果表明,在恒定降雨强度下,初始产流10min内,产流产沙量随时间迅速递增,随后缓慢增加并逐渐趋于稳定,总产流量大小为15°10°20°5°25°;10°总产沙量最大,15°和20°总产沙量相近,5°和25°总产沙量接近。不同坡度条件下总产流量和总产沙量随坡度的变化趋势均可用二次函数拟合,相关系数R2为0.65。10°~15°坡度之间存在一个对径流中养分浓度变化有显著影响的转折点。硝态氮在湿润层内的迁移过程用幂函数描述,铵态氮在湿润层内的浓度变化用三次多项式拟合,速效磷浓度在湿润层内随深度变化并不明显;硝态氮、铵态氮总流失量随坡度的变化趋势符合二次多项式变化,相关系数R2分别为0.91和0.77。20°时水溶性磷流失总量最大,为15°坡面的1.61倍。径流中初始养分浓度主要受养分在径流中溶解度的影响,在产流后期,土壤流失量对径流养分浓度的影响程度加大。     

坡度对坡面土壤矿质氮素水蚀流失负荷的影响

坡度是影响坡面水土流失和土壤养分流失过程的重要因素。室内模拟降雨试验表明,当坡长一定时,不仅土壤侵蚀量存在一个“侵蚀临界坡度”,土壤矿质氮流失量随坡度变化也存在一个“养分流失临界坡度”。试验测定这2个临界坡度均在15°～20°之间。土壤矿质氮地表流失以随地表径流流失为主,约占总流失量的99%。坡面矿质氮总流失量的96%为硝态氮,硝态氮对径流中矿质氮总量的贡献率明显高于在侵蚀泥沙中的贡献率。采取一定的截流措施是控制坡面矿质氮流失的关键。     

不同草被格局坡面水土-养分流失动力过程试验研究

利用模拟降雨试验研究不同草被格局对坡面水土-养分流失过程及径流侵蚀动力的影响,分析水土-养分流失量与径流侵蚀功率、草被格局、盖度及坡面坡度等因素之间的关系。结果表明:径流侵蚀功率随着草被盖度的增大呈幂函数减小,且28°坡面的径流侵蚀功率大于相同条件下的21°坡面;在相同植被盖度、坡度和降雨条件下,径流侵蚀功率随草被覆盖格局不同而不同,表现为坡下聚集格局径流侵蚀功率坡中坡上;坡面水土-养分流失量随径流侵蚀功率的增加呈对数递增关系,径流侵蚀功率可作为坡面水土-养分流失过程的驱动力指标。     

极端暴雨下裸地坡面径流及壤中流中碳素输移特征

采用人工模拟降雨的方法,研究了不同雨强(90、120、150mm·h~(-1))和坡度(5°、8°、15°、25°)条件下,南方风化花岗岩母质土壤红土层裸地降雨坡面径流和壤中流中总碳(Total carbon,TC)的流失量及流失过程,并分析了雨强和坡度对TC流失量的影响。结果表明,在坡面径流中,坡度和雨强的增大对碳素质量浓度变化过程影响较小,且流失率曲线与质量浓度曲线呈极显著相关关系,TC流失率变化主要受质量浓度的影响;在壤中流中,TC质量浓度曲线呈现出迅速上升达到最大值后缓慢下降直至平稳的趋势;在试验条件范围内,各坡度条件下,随着雨强的增大,坡面径流中TC流失量增大,而壤中流中TC流失量减小;在大雨强下,坡面径流中TC流失量与坡度没有明显的线性关系,而随着雨强的增大,坡度与壤中流中TC流失量线性关系明显增加;在试验雨强和坡度下,雨强对TC流失总量和坡面径流中TC流失量的影响较坡度更显著,而在壤中流中坡度的影响则更显著。径流中碳素流失量与雨强、坡度及场降雨径流总量之间均有明显的线性关系,R~20.800。结果可为我国南方风化花岗岩母质土壤裸坡径流中TC单位面积流失量的估算提供依据。     

急陡黄土坡面土壤剥蚀率变化的水动力学机制研究

为探明模拟降雨条件下急陡黄土坡面侵蚀产沙的水动力学特征,采用室内模拟降雨的方法研究了6个坡度(25°,30°,35°,40°,45°,50°)和3个雨强(1.0,1.5,2.0mm/min)组合条件下急陡黄土坡面土壤剥蚀率变化规律以及土壤剥蚀率与各水动力学参数之间的关系。结果表明:同坡度下土壤剥蚀率随雨强的增加而增大,相同雨强下坡度对土壤剥蚀率的影响存在临界效应(40°~45°),当坡度小于临界坡度时,土壤剥蚀率随着坡度的增加而增大,当坡度大于临界坡度时,土壤剥蚀率随坡度的增加而减小;径流剪切力、径流功率与过水断面单位能随坡度和雨强的增大均呈增加趋势,其中规律最好的是径流功率;急陡黄土坡面土壤剥蚀率与平均径流剪切力、平均径流功率与平均过水断面单位能均呈幂函数关系,就拟合优度而言,R~2(ω)R~2(τ)R~2(E)。因此本试验条件下平均径流功率是描述急陡黄土坡面径流侵蚀的最优水力学参数。     

黄土坡面细沟侵蚀过程

采用具有定流量放水组合小区模拟降雨试验方法,对黄土坡面细沟侵蚀过程进行模拟试验。结果表明：不同坡度和不同降雨强度下,细沟侵蚀率都呈现随径流变化过程的递增而增大的趋势,并且幂函数方程可以较好地模拟出其变化过程,同时在径流变化过程中,不同坡度下细沟侵蚀率随径流过程变化的递增速率总体上大于不同降雨强度下的递增速率;细沟侵蚀模数随坡度及降雨强度的增大皆增大,可分别用对数方程及指数方程很好地描述,坡度及降雨强度对细沟侵蚀模数的综合作用可用二元幂函数方程很好地描述;试验条件下,水流切应力是细沟侵蚀过程发生发展的动力根源。     

模拟降雨条件下秦岭北麓土壤磷素流失特征

以秦岭北麓竹峪地区为研究区域,采用模拟人工降雨的试验方法,研究了不同坡度(5°,10°)和不同降雨强度(1.1,1.3,1.5mm/min)下该区域田地土壤磷素流失过程规律。结果表明:降雨强度能够影响径流中溶解态磷(DP)的含量,但二者之间并非呈线性关系;相比于幂函数而言,指数函数模型更适合模拟秦岭北麓竹峪地区土壤径流溶解态磷(DP)浓度变化过程(R~20.75);降雨初期,泥沙中(STP)含量相对较高,但随着降雨的延续其浓度会有所下降,并最终保持在一个较稳定的水平上;泥沙全磷(STP)的流失速率随着降雨时间以幂函数的形式逐渐递减,同时发现泥沙全磷(STP)的流失速率与土壤流失速率之间存在着明显的线性关系(R~2=0.92),说明养分流失量累积过程与产沙过程一致,可以利用土壤侵蚀状况来进一步预测养分流失状况。     

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.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.