黑龙江省西部风蚀荒漠化特性与防治技术

通过对黑龙江省西部风蚀荒漠化特性的研究,得出在粗糙度(Z0)为0.41cm,0-5cm土壤含水量为3.76%条件下,距地面2m和0.5m的起沙风速分别为6.04m/s和4.69m/s。地表植被盖度与风蚀强度呈负相关关系,盖度越大,风蚀强度越小。在防治技术研究中,轻度风蚀采取植物措施与栽培措施相结合的办法;中度风蚀区采用复合式沙障治理流动式沙丘,网格沙障治理固定沙丘的防治技术研究;重度风蚀区则根据不同类型不同荒漠化程度,采取"前挡后拉",行列式沙障等防治技术,防治效果明显。     

冀北坝上地区3种人工灌木林地防风蚀效果的比较

选取冀北坝上地区防风固沙林为研究对象,通过观测风速、地表粗糙度、临界起沙风速、输沙量、风沙流结构等指标,对比分析3种人工灌木林地(沙棘林地、柠条林地、沙柳林地)防风蚀效果。结果表明:人工植被能够增加地表粗糙度,改变近地表风场和风沙流结构,降低风速,减少输沙量,有效防治土壤风蚀。不同人工灌木林地防风蚀效果存在较大差异。从主要观测指标来看,粗糙度和临界起沙风速为柠条林地>沙棘林地>沙柳林地;输沙量为柠条林地<沙棘林地<沙柳林地;防风效应为沙棘林地>沙柳林地>柠条林地;固沙效应为柠条林地>沙棘林地>沙柳林地。冀北坝上地区应充分发挥林木防风固沙、保持水土的特性,采用生物治沙技术与措施,合理配置人工植被开展生态建设,防治土壤风蚀,改善生态环境。     

农牧交错带土地利用类型对土壤风蚀的影响

[目的]研究农牧交错带不同土地利用类型对土壤风蚀的影响,为干旱沙区土地资源的合理利用及经营耕作提供科学依据。[方法]通过气象资料和野外风蚀试验,分析该区不同土地利用方式下的土壤风蚀状况。[结果]不同土地利用类型对土壤风蚀的影响显著,在不同利用类型的人工草地中羊草地较苜蓿地减蚀效果显著,天然草地中滨草地减蚀效果优于蒿草地,人工草地较天然草地显著降低土壤风蚀量。农田用地中耕翻地土壤风蚀量最高,未留茬免耕玉米地较耕翻地风蚀量减少46.7%~48.6%;作物留茬地土壤减蚀效果显著,且留茬作物不同,减蚀效果差异明显,玉米留茬较耕翻地风蚀量减少了58.1%~63.5%,荞麦留茬较耕翻地减蚀率为50.5%~54.6%。在不同地形坡地中迎风坡风蚀量高于背风坡3.12~3.73倍。[结论]应在该地区适宜增加人工草地种植面积,减少冬春季节耕翻地面积,减少迎风坡土地的开垦利用,在冬春季节采取地表覆盖或者作物收获后留茬的保护措施,以降低土壤风蚀程度。     

不同植被覆盖防治土壤风蚀对比研究

通过对毛乌素沙地不同下垫面上风速、地表粗糙度、临界起沙风速、风沙流结构的观测,发现植被覆盖可以有效防止地表风蚀：植被盖度为40%的固定沙地近地表0.2 m高度平均风速比流动沙地降低45%,侵蚀风的持续时数降低83%,临界起沙风速提高70%,地表粗糙度提高190倍;当风沙流速度相同时,20%覆盖度的半固定沙地较流动沙地可平均降低输沙79.4%;而植被盖度为40%的固定沙地较流动沙地可平均降低输沙95.6%。实验证明,单株植物同样可以降低风速。疏透结构和透风结构的单株沙蒿分别可以使植株后0.5 m高度的风速较植株前方平沙地同高度的风速下降59.4%和19.8%。     

北京南郊沙地风蚀物理特征及防护对策研究--以大兴区为例

目前风沙危害是北京南郊地区面临的最为严重的生态环境问题之一．该区域的风蚀治理迫在眉睫。本文选择耕地、荒草地、流动沙地等永定河沙地典型的土地利用类型．通过定位实验观测与数学定量分析．进行沙地地表风沙活动的原理特征与风蚀防护措施的研究。研究结果认为：近地层风速随高度服从对数分布;下垫面性质不同导致对应的摩阻速度大小不同;不同利用类型下垫面对应的起沙风速明显不同;0～20cm高度范围内各层的输沙率百分含量随着高度的增加而减少,两者呈负指数函数;输沙率与风速呈正指数函数;风蚀地表组成物质明显粗化。基于该沙地的风蚀特点．提出了适合本沙地特点的综合治理技术措施。     

京郊延庆康庄地区不同土地利用类型对土壤风蚀的影响

在2005～2006年冬春大风季节，对北京市郊区延庆康庄地区不同土地利用类型（疏林地．乔灌草．林草．翻耕地，免耕地，菜地，果菜间作）进行了风速、粗糙度、风蚀量的实地观测。得出的初步结论为：不同防护林模式中乔灌草模式与疏林地和林草两种模式相比，地表粗糙度最大，削弱近地面风速和降低土壤风蚀量的效果也最为明显；农田中果菜间作地表粗糙度最大，免耕地次之，翻耕地最小；在削弱近地面风速方面，果菜间作效果最为明显．菜地次之，翻耕地最差；在降低土壤风蚀量方面，免耕地降低幅度最大，果菜间作次之，翻耕地最差；在不同防护林模式中．乔灌草防风蚀效果最好．在农田中，免耕与果菜间作防风蚀效果较好。     

天然灌草植被防治土壤风蚀机理

通过对毛乌素沙地不同下垫面上风速、地表粗糙度、临界起沙风速、风沙流结构的观测,发现植被覆盖可以有效防止地表风蚀。植被盖度为40％的固定沙地近地表0．2m高度平均风速比流动沙地降低43％,侵蚀风的持续时数降低85％,临界起沙风速提高70％,地表粗糙度提高180倍;当风沙流速度相同时,20％覆盖度的半同定沙地较流动沙地可平均降低输沙62．33％;而植被盖度为40％的同定沙地较流动沙地可平均降低输沙93．07％。实验证明,单株植物同样可以降低风速。疏透结构和透风结构的单株沙蒿分别可以使植株后0．5m高度的风速较植株前方平沙地同高度的风速下降59．4％和19．8％。     

不同地表状况对土壤风蚀的影响——以内蒙古太仆寺旗为例

通过对采取不同耕作措施和不同留茬方式的农田土壤进行野外风沙观测.观测结果表明,人为因素对农田土壤风蚀影响非常大,不同地表状况的土壤风蚀特征存在显著差异.留茬地因为表面残茬的存在显著增加了土壤表面粗糙度,从而使得其风蚀强度较小;而秋翻地人为扰动较大,表面覆盖度较小,其风蚀强度在所研究的土壤中为最大.因此,对于内蒙古太仆寺旗农田土壤风蚀较严重区域,应该采取留茬措施以减少人为扰动,增加覆盖度以提高土壤表面粗糙度,从而有效地减少土壤风蚀.     

沙地土壤风蚀动力因子分析

地表粗糙度反映地表对风速减弱的作用以及对风沙流的影响 ,其值大小取决于地形、植被覆盖及作物的播种方向 ,粗糙度越大风蚀强度越小。吉林省西部流动沙丘的起沙风速为 1 0 3m/s,风蚀耕地的起沙风速为 6 3～ 7.9m/s。春季侵蚀性风能为 1 72 1 8(v·u)。该区风蚀性气候因子和侵蚀性风能自东向西递增 ,西北部的通榆为最大     

新疆托克逊县不同配置防护林的防风蚀效能

[目的] 对比分析不同配置防护林迎风林缘与背风林缘的防风蚀效能,为干旱区绿洲城市防护林建设、防沙治沙以及生态环境改善工作提供理论依据。[方法] 以新疆托克逊县城郊区不同配置防护林为研究对象,通过观测近地表风速、起沙风速、近地表粗糙度、输沙量、风沙流结构等指标,对比研究混交林1（胡杨68%+柽柳32%）、混交林2（柽柳65%+胡杨35%）、梭梭林迎背风林缘的防风蚀效能。[结果] 不同配置防护林的地表粗糙度、起沙风速、风速廓线、防风阻沙效能都有差异。不同配置防护林地面粗糙度从高到底依次为：混交林2（0.569 cm）>混交林1（0.378 cm）>梭梭林（0.123 cm）。起沙风速从高到低依次为：混交林2（6.17 m/s）>梭梭林（6.02 m/s）>混交林1（5.98 m/s）。防风效能从强到弱依次为：混交林2>混交林1>梭梭林。阻沙效能依次为：梭梭林（48.2%）>混交林2（45.6%）>混交林1（37.1%）,各林地0—10 cm,10—20 cm垂直高度上的集沙量所占比例较高。[结论] 混交林2有效降低不同垂直高度的风速及输沙量,混交林2的防风蚀效能较高。     

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.     

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.     

Genetic similarities among Spanisch populations of Agropyron, Elymus and Thinopyrum, using PCR-based markers

Arbitrary oligonucleotides were used as primers to amplifygenomic DNA of 48 wild Spanish populations of Agropyroncristatum, Elymus hispanicus,E. caninus,E. repens,Thinopyrum curvifolium, Th.junceum and Th.intermedium. Genetic diversity was analysedusing nineteen primers. The number of amplified products ranged from8 to 18 per primer and a total of 240 markers were scored. Differentlevels of intraspecific genetic diversity were found, the allogamousspecies E. repens andTh. intermedium being themost variable. Jaccard's similarity coefficients for internalmeasure within and between populations were used to produce a clusterdiagram. The results demonstrate differences in the degree ofsimilarity between taxonomic units. Interpopulational variability andinterspecific genomic relationships of these species arediscussed.     

Mycorrhizae,biocides, and biocontrol. 4. Response of a mixed culture of arbuscular mycorrhizal fungi and host plant to three fungicides

The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg^-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants.