旱作农田沟垄微型集雨结合覆盖玉米种植试验研究

田间沟垄微型集雨结合覆盖技术有效地利用了膜垄的集水和沟覆盖的蓄水保墒功能,改变了降雨的时空分布,使降雨集中富集在种植沟中,显著地提高了降水的利用效率,特别是小雨的利用率。研究结果表明:土垄的平均集水效率为7% ,而垄上覆膜后集水效率为87% ,膜垄能产生径流的最小降雨量为0 8mm。田间沟垄微型集雨结合覆盖技术能提高土壤贮水量,增加玉米的产量。垄上覆膜结合沟覆盖处理玉米产量比平地增加2 339～5 2 97kg/hm2 (44 %～14 3% ) ,水分利用效率基本都在2kg/m3 以上。     

容器苗造林技术要点分析

容器育苗造林具有节水抗旱、成活率高的优势,在容器苗根系可形成自带基质,其不仅不会松散脱落,而且具有较高的肥力,在苗木起苗、运输时能在最大程度上保护苗木根系的完整性。造林时将完整的根系植入造林地,可为苗木生长提供较好的过渡期,且造林后会有较长的缓冲抗旱期,大大延长了造林季节,提高了干旱地区、瘠薄石质山地、沙滩荒地的造林成活率。基于此,主要针对容器苗造林的技术要点进行探讨。     

活动式坡地集雨及滴灌系统研究

雨水利用是干旱半干旱地区农业发展的生长点，该文依据干旱半干旱地区自然降水特征、农耕地分布特点、农业种植制度、作物需水与土壤水分动态变化规律，提出了“上坡春季种粮，秋季覆膜集雨，地边打窖贮水，补灌下部作物”的坡地活动式集雨及灌溉系统，并对其集雨效率、农田水分效应和系统产出效益进行了试验研究。研究结果表明，该系统具有集水效率高、保水效果好和增产效益明显的优点，是一种适合于干旱半干旱地区的集雨灌溉农业模式。     

黄土丘陵沟壑区鱼鳞坑雨季土壤水分状况

在黄土高原半干旱地区,降水是限制植被生长的主要限制因子。鱼鳞坑作为一种集水措施在人工造林中被普及推广。为研究鱼鳞坑雨季的集水功能,对样地鱼鳞坑内部、上部及侧面坡面典型部位的土壤水分进行了连续性监测,结果显示：7—8月,鱼鳞坑内的平均土壤含水量维持在低于鱼鳞坑外部坡面的水平;鱼鳞坑内20～40 cm土层是土壤水分的主要利用层,鱼鳞坑的集雨效果表现在40～60 cm土层上;单个鱼鳞坑的集雨效果存在差异性,这种差异性主要表现在有径流产生的降雨期。单个鱼鳞坑的集雨效果受鱼鳞坑的布置模式、施工工艺等因素的影响。     

径流林业技术在我区的推广应用

在干旱，半干旱区地造林，由于降雨少而集中，致使林大难以成活且生长缓慢。径流林业技术通过对集雨带的坡面处理，使有很的降雨资源再分配，达到了集水，节水的目的，从而提高造林成率和林木长量。     

黄土高原沟壑区阴坡油松集水造林集蓄比试验研究

按照水量平衡原理,采用对比研究方法,对黄土高原沟壑区阴坡坡地油松集水造林的年耗水量、土壤水分盈亏、土壤含水率、苗木成活率、苗木生长量、整地费用进行了研究,结果表明:汛前是一年中土壤水分亏缺最多的时段,汛期是一年中降水量最多的时段;黄土高原沟壑区阴坡山地油松集水造林适宜的集蓄比为3∶1~4∶1,适宜的造林密度为1000~1250株/hm2。     

集水措施下油松植树带微域环境的水量平衡分析

为解决因干旱少水导致黄土高原树木生长不良的问题,利用径流林业的理论,对不同集水面积和集水措施对油松生长环境的水量平衡做了研究。结果表明,不同的集水面积和坡面处理措施对植树带的来水量、耗水量和水量平衡都产生较大影响。其中集水面积5m2的水分盈余比集水面积3m2的要多,采取压实拍光措施(PG)的水分盈余比未采取措施(CK)的要多。     

3种有机硅喷涂集雨面后的产流特征与集雨效率

集雨工程的建造往往比较复杂,寻找更经济、简便的集雨材料是干旱半干旱地区雨水资源利用的重要研究方向。高分子有机硅由于其具有良好的防水性、化学惰性、操作简单等特性,成为新型集雨材料的潜在选择。试验选用3种不同性质的硅烷(有机硅)乳液,设计4种有机硅与水的稀释比例(1∶7,1∶10,1∶13,1∶16),3种集雨面坡度(0°,9°,15°),通过室外模拟降雨进行集雨效率观测。结果表明,集雨效率道康宁IE-6683最大,为96.96%,道康宁520次之,为96.50%,有机硅原液为90.24%;3种有机硅与水的比例在1∶13与1∶16时集雨效果较好,平均集雨效率在90%以上;集雨面坡度对集雨效率具有显著影响,有机硅原液在坡度为0°与9°变化时集雨效率随坡度增加而增加,坡度为15°时集雨效率有所下降,道康宁520与道康宁IE-6683集雨效率均随集雨面坡度的变大而增加。     

干旱瘠薄山区绿化技术的研究

在介绍山东省山区丘陵概况的基础上 ,系统论述了砂化、石漠化区封山育林技术 ,干旱瘠薄山地造林技术 ,经济林旱作栽培技术 ,为山东省干旱瘠薄山区绿化和防治水土流失提供依据。     

鲁中南山地6个造林树种根系形态的比较

干旱瘠薄山地造林树种选择是制约这一特殊生境植被修复的关键问题。为明确不同树种对干旱瘠薄生境的生态适应策略,为困难地造林树种选择提供依据,采用挖掘法获取树木整体根系,用根系扫描仪测定细根形态参数,对比分析鲁中南干旱瘠薄山地黑松、侧柏、黄连木、麻栎、黄栌、扶芳藤6个造林树种根系构型及细根形态特征,阐明干旱瘠薄生境中不同树种根系形态的差异性及其对特殊生境的适应性。结果表明:1)相同立地条件下6树种根系构型差异较大,黑松、侧柏、扶芳藤根系表现为浅根性,依靠水平空间的拓展获得水分和养分是它们对干旱瘠薄生境的适应策略;而黄栌、黄连木、麻栎根系则为深根性。2)各树种细根形态存在较大差异,扶芳藤各级细根数量最多,且长度、表面积和体积显著高于其他树种(P<0.05),表明其具有极强的生根能力及水分和养分利用能力。3)麻栎和扶芳藤低级细根(1~2级)的比根长在所有树种中最大,表明它们的细根具有良好的吸收功能。根据各树种的根系形态特征,在干旱瘠薄山地造林实践中,可利用其根系生长策略的不同考虑树种混交,营建针阔混交、乔灌混交等多种林型,充分发挥森林固水保土等生态效益。     

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.     

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.     

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.     

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.     

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.     

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.