基于GIS的贵州西部春薯种植气候适宜性精细化区划

以贵州西部地区15个气象观测站1978-2010年的气候资料为基础,采用地理信息系统(GIS)技术,对春薯进行气候适宜性区划,为贵州春薯生产安全布局、品种调整提供科学依据。通过分析马铃薯平均气象产量与同期气候因子的关系,得出春薯的气候适宜性区划指标有8个:海拔高度、生育期平均气温、>10℃活动积温、降水量、日照时数以及7月平均气温、7-8月昼夜平均温差、5-7月降水量,每个指标分3级,对应最适宜、适宜和次适宜。通过对各站点的气候资料及其对应的经度、纬度、海拔高度、坡度和坡向等基础信息数据,应用多元线性回归方法,建立区划指标的空间分析模式。依托GIS技术空间分析功能,运用模式进行网格距为100m×100m以及精确到贵州西部地区乡(镇)的精细化气候区划,得到春薯最适宜区占贵州西部面积的52%,适宜区占45%,次适宜区占3%。     

陕西油菜生态气候适宜性分析与精细化区划

利用陕西省96个气象站1981-2010年油菜生长阶段气象资料和地理信息数据,采用GIS技术对油菜进行气候适宜性区划,以期为气候变暖背景下的陕西油菜生产合理规划布局和可持续发展提供科学依据.通过综合分析陕西各地油菜气候适宜性特点和影响油菜产量的关键气象因子,选取1月日最低平均气温、蕾薹期平均气温、生育期平均气温、生育期≥0℃积温和生育期降水量作为陕西油菜生态气候适宜性区划指标,建立各区划指标的小网格推算模式,应用GIS技术推算出陕西无测站区域100m × 100m网格点上的气候要素值,采用综合评判的方法得到陕西油菜精细化气候适宜性区划图,并进行分区评述.结果表明,最适宜种植区主要分布在陕南汉江及其支流沿岸海拔600m以下川道、平坝地区,以及关中渭河及其支流沿岸海拔700m以下的平原地区;适宜区主要分布在秦岭北麓海拔850m以下的河谷、浅山丘陵区,秦岭南麓、巴山北麓海拔750m以下的浅山丘陵地带,以及渭河北岸最适区以北海拔800m以下的台塬地区.     

未来气候变化情景下海南岛绿橙种植气候适宜性分析

基于海南岛主岛19个气象站点连续40a（1980-2019年）逐日气象数据及地形等要素，建立空间分析模型，综合确定海南岛绿橙种植气候适宜区指标。在气候适宜度模型基础上构建海南岛绿橙种植温度、日照、降水以及综合适宜度模型，采用地理信息系统（GIS）技术综合分析，利用自然点断法对绿橙种植气候适宜性进行精细化区划，并利用RCP4.5未来气候情景模式模拟数据探讨未来30a（2020-2049年）气候变化情景下海南岛绿橙种植适宜区变化趋势。结果表明：现阶段海南岛绿橙种植最适宜区主要分布于中部地区，面积0.87×10⁴km²，气候适宜度为0.9～1.0；适宜区主要分布于东部局部地区及中西部大部地区，面积1.83×10⁴km²，气候适宜度为0.7～0.9；次适宜区主要分布于西部沿海及中西部海拔较高地区，面积0.51×10⁴km²，气候适宜度为0.4～0.7；不适宜区主要分布于中部山区，面积0.17×10⁴km²，气候适宜度为0～0.4。未来气候变化情景下海南岛气温、降水分布呈较大变化，温度适宜区由四周向中部逐渐缩小，降水适宜区由东部逐渐迁移至中部地区。未来绿橙种植气候最适宜区主要分布于琼中、屯昌和保亭县大部分地区、万宁市西部及白沙县中东部等地。     

贵州山区红心猕猴桃种植气候区划

基于贵州西部红心猕猴桃种植区2005-2014年逐日气温、降水资料,依据贵州85个气象观测站1981-2010年逐旬、逐月、逐年平均气温、降水量、日照时数和极端最高、最低气温以及观测站和1462个乡镇的地理信息数据,应用经验正交函数分解法和模糊聚类法,通过分析贵州省西部红心猕猴桃各生育期的气候条件,得到红心猕猴桃种植的气候适宜性区划指标,采用GIS技术对红心猕猴桃种植进行气候适宜性区划。结果表明：年平均气温、历年极端最低气温（80%保证率）、1月平均气温、3月平均气温、7月平均气温、8月昼夜温差、年降水量、年日照时数可作为红心猕猴桃种植的气候适宜性区划指标,每个指标分4级,对应最适宜、适宜、次适宜和不适宜,红心猕猴桃种植最适宜区在贵州西部地区,适宜种植区在贵州中部偏西地区,次适宜种植区在贵州中部,不适宜种植区主要分布在遵义市、铜仁市、东南部局部和西部边缘。调查表明,贵州山区红心猕猴桃实际种植情况与气候适宜性区划结果基本吻合。     

基于GIS的湖北省人居环境气候适宜性评价

运用GIS技术,以30m×30m为栅格尺度,基于温湿指数,采用反距离权重法、普通克里金插值法进行空间内插,系统分析温湿指数在湖北省的空间分布规律,定量评价湖北湖北省人居环境气候适宜性。研究表明:1从总体上说:温湿指数的分布由东南部地区向西北部山区递减。7月份全境只有鄂西山区的部分地区适宜居住,面积大约有大约有3 753.46km2,1月份全省处于不适宜区。2湖北省人居环境气候适宜性区域差距明显,高度适宜区分布在鄂西山区,不适宜区分布在武汉附近的一些地区。3湖北省气候适宜程度表现在由平原向山区、由东南向西北递减的趋势,大部分地区属于一般适宜区与临界适宜区,不适宜区与高度适宜区面积较少。4鄂西山区气候适宜性受到海拔高度的影响,出现了立体适宜性,即随海拔的不同适宜性出现差异。     

基于GIS的台湾青枣在福建引扩种的气候适宜性区划

为合理利用福建气候资源、优化台湾青枣在福建的种植布局,基于GIS开展台湾青枣在福建引扩种的气候适宜性区划。根据台湾青枣的生长气象指标、生命周期和生产管理特点,选取≥10℃年活动积温(∑T≥10℃)、年平均气温(Tavg)、90%保证率年极端最低气温(T90%JDW)、年降水量(R)、年日照时数(S)5个气象因子作为区划指标,构建台湾青枣的气候适宜性区划指标体系;采用专家打分法和层次分析法对区划指标进行权重分析,建立气候适宜指数算法;基于气象要素值、经度、纬度、海拔高度,通过线性回归建立5个区划指标的小网格推算模型;结合小网格推算模型和气候适宜指数算法,开展台湾青枣在福建引扩种的气候适宜性区划;采用前期相关研究成果、青枣种植现状对区划结果的可靠性进行验证。结果表明:台湾青枣的适宜种植区主要分布在泉州市辖区以南的沿海县市和漳州市的部分内陆县市;次适宜区主要分布在福建中部沿海地区及龙岩南部的永定、上杭部分乡镇,该区种植青枣可能遭受寒冻害,应注意低温防护;其余县市为不适宜种植区。区划结果与前期研究成果和青枣种植现状一致。研究结果可为台湾青枣在福建的引种、扩种和种植结构调整提供参考。     

基于GIS的广东香蕉种植气候适宜性区划

以广东省86个气象站点1992-2005年的气象数据为依据、利用数理统计方法对1992-2005年香蕉平均气象产量与同期气候条件进行相关分析,确定香蕉种植的气候适宜性区划指标。根据广东86个站点1970-2009年的气候资料及对应站点的经纬度、海拔高度、坡度和坡向等基础信息数据,应用多元线性回归确定区划指标空间分析模型,推算出1km×1km的气象要素分布图。依托GIS技术空间分析功能,根据综合评分标准进行香蕉种植气候适宜性区划,得出广东省气候上最适宜种植香蕉的土地面积占17%,适宜区占18%,次适宜区占25%,不适宜区占40%。研究结果可为广东香蕉种植的合理布局提供参考。     

气候变化背景下中国苹果适宜种植区北移西扩：基于高分辨率格点气象数据的区划分析

利用1981-2010年5km×5km格点气象数据,基于前人研究指标,采用气候倾向率、ArcGIS空间插值等方法,对影响苹果种植的气温、降水、相对湿度等主要气候指标分布特征进行分析。首先利用一票否决式指标剔除不能满足苹果生长基本要求的不可种植区域,然后结合苹果气候区划因子评分标准,对可种植区进行适宜性评价,并分析年际间适宜区的变化特征。结果表明,总体来看,苹果可种植区为华北、西北、西南以及华东、华南的部分地区。在可种植区中,适宜区主要位于黄土高原大部分地区和环渤海地区,次适宜区主要位于华北平原和黄土高原少部分地区以及塔里木盆地和云贵高原地区,不适宜区主要分布在东北地区、长江以南大部分地区、青藏高原地区以及新疆北部部分地区。与20世纪80年代相比,90年代、21世纪00年代山东半岛、黄土高原南部由适宜种植区转变为次适宜种植区,辽蒙交界地区、云贵川交界地区、黄土高原北部以及陕甘交界处由次适宜种植区转变为适宜种植区,苹果适宜种植区变化呈现明显北移西扩的特点。     

新疆平欧杂种榛种植气候区划

利用新疆40个气象台站连续10a(2009-2018年)气象数据年平均气温和地理信息资料,选取海拔、年平均气温、年均降水量、日照时数4个因子作为区划指标;采用多元回归,建立气象因子的空间模型,利用地理信息系统(GIS)技术对4个因子参数进行数据网格插值分析;根据层次分析法(AHP)计算指标权重值,利用GIS叠加分析功能,得到平欧杂种榛适生区专题图。结果表明:平欧杂种榛种植区分为最适宜区、适宜区、次适宜区、不适宜区;最适宜区面积为27.722×10~4km~2,占新疆土地总面积的16.7%,主要分布在喀什地区、阿克苏地区、伊犁河谷、昌吉回族自治州、乌鲁木齐市、巴音郭楞蒙古自治州北部、吐鲁番地区以及哈密地区北部;适宜区面积为69.056×10~4km~2,占新疆土地总面积的41.6%,主要分布在喀什地区、克孜勒苏柯尔克孜自治州、和田地区北部、巴音郭楞蒙古自治州北部、阿克苏地区、塔城地区以及阿勒泰部分地区。     

雅安4·20震后宝兴河流域农村居住区适宜性评价

在汶川—芦山两次强震作用下,先天脆弱与高风险并存的武都—泸定一线山区成为受灾最为严重的地理单元。灾区生境重建是4·20灾后重建的重点、难点,也是维护灾区社会稳定的关键之一。以宝兴河流域农村居住地为研究对象,选取了地形、气象、植被、地质灾害、大熊猫栖息地世界遗产等影响适宜性的关键因子,开展农村居住地环境适宜性评价。结果表明:(1)山区农村居住地适宜性分布呈现出明显的海拔、坡度、坡向指向,且集中分布在世界遗产保护区及其外围。海拔2 900m以下、坡度小于30°且阳坡、半阳坡地带是适宜性及次适宜性的主要分布区,具有沿河流及两侧集聚分布的特征,说明地形条件是影响适宜性分布的主要因子;(2)海拔2 900m以上、坡度大于30°且半阴坡、阴坡地带是较不适宜及不适宜的分布区域,这与山高坡陡、热量不足等局地植被生境限制条件有关;(3)农村居住地适宜性由东南部向西北部逐渐降低,适宜区占总面积的16.79%,次适宜区占26.93%,较不适宜区占32.47%,不适宜区占23.81%。研究结果可为地震灾区安全选址与生境修复提供科技支撑。     

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,     

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.     

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.