主要紫色土电导率特征及其影响因素研究

本研究初步探讨了四川丘陵区暗紫泥、灰棕紫泥、棕紫泥和红棕紫泥4种主要紫色土电导率的特性。研究结果表明,这四种主要紫色土的平均电导率为185.62±44.33μScm-1,土壤阳离子交换量、有机质、pH和容重与土壤电导率有着不同程度的相关性,其中土壤阳离子交换量和土壤容重与土壤电导率呈极显著相关,土壤有机质和pH与土壤电导率呈显著相关。     

我国酸性硫酸盐土壤中铁锰形态转化及迁移

酸性硫酸盐土壤酸性很强，有机质含量高，造成了这种土壤所特有的铁锰淋洗、转化和迁移规律。研究结果表明：在酸性硫酸盐土壤中全铁含量较低，一般在３５－５０ｇ／ｋｇ（以Ｆｅ２Ｏ３计），全锰含量也低，一般在０．２５－０．５５ｇ／ｋｇ（以ＭｎＯ计），一般滩涂中全铁大于６０ｇ／ｋｇ，全锰大于１ｇ／ｋｇ。酸性硫酸盐土壤中，铁的游离度较小，一般在３７－７０％，铁的活化度较大，一般在８－２０％，而滩涂中铁的游离度一般     

紫色水稻土硅有效性的研究

通过田间试验和土壤培养试验研究了紫色水稻土有效硅含量的概况，影响因素及施硅效应。结果表明，紫色水稻土施硅肥有不同程度的增产效应，增产幅度〉１０％的土壤占５５％。土壤有效硅含量为红紫泥田〈灰棕紫泥田〈红棕紫泥田。     

拉巴豆在不同土壤上的结瘤效应、饲用品质

选择重庆市4种具有代表性的土壤（灰棕紫泥两种、红棕紫泥和灰岩黄壤各一种）,接种促生根瘤菌,研究了拉巴豆的结瘤性能、生长情况、光合速率、营养品质及矿质养分等。结果表明,在微酸性和酸性灰棕紫泥土壤上,拉巴豆的生长、生理、光合、产量和品质显著优于灰岩黄壤和红棕紫泥。在微酸性灰棕紫泥（pH 6.14）和灰岩黄壤（pH 6.45）上,接种根瘤菌能形成根瘤,但在酸性灰棕紫泥（pH 4.09）和碱性红棕紫泥（pH 7.50）上,形成根瘤极少或不形成根瘤,说明土壤酸碱度过高和过低均抑制根瘤形成。接种根瘤菌形成根瘤之后,不同程度地改善了拉巴豆氮、磷营养,提高了其净光合速率,促进了生长,增加了生物量,改善了品质。拉巴豆生物量,氮、磷吸收量,收获后土壤有效氮、磷含量与根瘤重量呈显著正相关,故根瘤重量可反映根瘤活性。此外,在微酸性灰棕紫泥土壤中,拉巴豆的根瘤数量虽然比灰岩黄壤少53.32%,但根瘤体积较大,根瘤重量为灰岩黄壤上的1.66倍,接种效应总体上优于灰岩黄壤。所以,在重庆市的拉巴豆栽培中,选择微酸性和酸性灰棕紫泥,并接种根瘤菌有益于高产优质。     

应用交换性NH4—沸石重新释放土壤中的磷

通过室内模拟、盆钵栽培和田间试验，研究ＮＨ４－饱和斜发沸石交换体重新释放石灰性土壤累积的难溶性磷。结果表明，ＮＨ４－沸石具有很强的释磷作用，溶解磷灰石和土壤难溶性磷的能力是对照的４．８７－１２．８６倍；土壤有效磷含量啬加０．５－１９．０μｇ／ｇ，增长６．４％－４６．３％。小麦体内磷素含量提高３１－７３２ｍｇ／ｋｇ，磷素累积量增加２９．８９％－４８．５４％。盆栽小麦增产４．５％－２９．８％，玉米增产     

贵州省典型土壤中稀土元素含量及分布特征

本文对贵州省六个主要土类有代表性的典型土壤６８个剖面,２０４个土样中的稀土含量及分布进行研究。结果表明：贵州省典型土壤中稀土元素总量（２６４．４４μｇ／ｇ）高于全国土壤平均含量（１９５．７μｇ／ｇ）,各土类稀土元素的丰度都遵守Ｏｄｄｏ－Ｈａｒｋｉｎｓ法则,Ｃｅ富集明显,贵州典型土壤中轻稀土元素含量（１９９．０１μｇ／ｇ）亦高于全国土壤,属典型的轻稀土土壤类型;石灰土中稀土各元素含量大于其它土类。同     

紫色土镍对莴笋的毒性临界状态值研究

以盆栽试验，研究了紫色土中镍对莴笋的毒性统一临界指标。结果表明，以０．０５ｍｏｌ／Ｌ ＣａＣｌ２提取Ｎｉ为指标的土壤Ｎｉ毒性临界状态值在各土壤中可达统一，考虑到土壤伴随元素的影响，可按石灰性和非石灰性紫色土两种情况制定指标，本研究结果是：非石灰性紫色土为（１１．４±０．９２）ｍｇ／ｋｇ土，石灰性紫色土为（１．２±０．１１）ｍｇ／ｋｇ土。     

石灰性紫色土渍水氧化还原状况的研究

本文通过模拟培育试验，研究了石灰性紫色土渍水状态下氧化还特征。结果表明，石灰性紫色土与普通紫色土，不饱和紫色土相比，不易向强还原状况发育，这些其富含碳酸钙和低量的活性铁有关；不同种类有机物料对其还原程度的影响是不同的；表征土壤氧化还原过程的强度因素Ｅｈ和数量因素还原性物质含理有很好的相关性，并与水稻的生长状况相一致，当土壤Ｅｈ小于－１００ｍＶ，还原物总量大于３．６３ｃｍｏｌ＾（＋）／ｋｇ时，土壤极     

磷影响下根际无机砷的形态分布及其对水稻生长的影响

两种有代表性的紫色土的水稻盆裁试验结果表明，磷的加入可减轻受砷污染的红紫泥中砷对水稻的毒害；但磷的加入会加剧受砷污染的红棕紫泥中砷对水稻的毒害。根际无机砷的形态分布研究表明：试验土壤上，根际砷各形态都比非根际高，砷在根际呈富集状态；在根际环境的作用下，红紫泥中，磷的加入加剧了砷由有效态砷（Al-As、Fe-As）向相对无效态砷（O－As）转化，砷对水稻的毒性减弱；红棕紫泥中，磷的加入加剧了砷由相对无效态砷Fe-As和Al-As向有效态砷Ca-As和A-As（表示水溶态砷及松结态砷）的转化，砷对水稻的毒性增强。     

安徽省主要农用土壤中硫形态组份的初步研究

对安徽省６种主要农用土壤耕层（黄潮土、灰潮土、砂姜黑土、黄红壤和水稻土）２２个样品中硫形态组份的分析表明：供试土壤中总硫（Ｓ）含量为１１２．４－２３７．０（均值为２０５．８）μｇ ｇ＾－１。各土壤的有机硫和无机硫含量有所不同。其中，黄潮土、灰潮土的总Ｓ含量相对较高，潜在供硫能力相对较强，但土壤有效硫低；砂姜黑土、水稻土的总硫含量中等，潜在供硫能力较大，土壤有效硫中等；黄褐土、黄红壤的总硫含量小，潜     

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.     

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.     

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.     

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.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.