陕西黄土台塬区土地系统变化特征分析

基于GIS和RS支持,采用土地利用变化系列指标对陕西黄土台塬区1985-2010年土地利用变化特征进行了分析。结果表明,2010年黄土台塬区耕地984337.30 hm²,草地143030.47 hm²,建设用地105871.35 hm²,分别占总面积77.89%,11.32%和8.38%;研究时段内耕地、草地、林地、水域依次减少20866.61,11065.22,1186.44和748.96 hm²,分别比1985年减少了2.08%,7.18%,4.60%和11.64%;建设用地增加33902.8 hm²,为1985年的47.11%;建设占用耕地26668.8 hm²,占建设用地转入流的96.26%;草地转耕地18923.9 hm²,占草地转出流的93.24%;1985-1990年土地系统较为稳定,综合动态度为0.52;1990-1995土地利用变化活跃,综合动态度达到3.60,其后逐渐降低,到2005-2010降低为1.16,土地系统趋于稳定。空间上,耕地转建设用地在城镇周边幅度较大,草地和耕地互转主要在渭南台塬东部、咸阳塬北部以及宝鸡台塬区。     

乡村振兴视角下“三生”空间格局演变及优化策略——以陕西省米脂县高西沟村为例

[目的] 探寻城镇化快速发展条件下作为生态示范村的陕西省米脂县高西沟村的土地利用转型特征,为陕北黄土高原地区的乡村“三生”空间可持续发展提供参考。 [方法] 通过土地利用动态度、土地利用转移矩阵分析高西沟1953—2022年的“三生”空间特征,并结合实地调研对村域多年“三生”空间格局演变特征及对应的空间治理优化策略展开分析。 [结果] ①1953—2022年,高西沟生产空间呈减小趋势,生活空间和生态空间呈增大趋势。1953—1973年,生态空间变化幅度最大,绿地生态空间从12.07 hm²增加到100.33 hm²,其他生态空间从12.07 hm²减小到100.33 hm²,生产空间逐渐减小,从145.67 hm²减小到110.07 hm²。1986—2022年,生产空间减少了42.4 hm²,生活空间增加了5 hm²,生态空间增加了37.39 hm²。 ②1986—2022年,高西沟“三生”空间转型体现在绿地生态空间和农村生活空间的增加,农业生产空间、其他生态空间和水域生态空间的减少。有67.83 hm²的农业生产空间和59.95 hm²的其他生态空间转化为绿地生态空间,而部分绿地生态空间转化为农业生产空间和农村生活空间,其转移面积分别为21.20和3.22 hm²。 ③高西沟针对生产空间效益不足的问题,采取改变广种薄收的耕种方式,大幅提高粮食产量,改变单一的农业生产状况,实现多种经营模式并存的举措;针对生活空间品质低下的问题,采取全力抓牢基建,量力新建家园,鼓励青年外出,从事其他产业的举措;针对生态空间破坏严重的问题,采取控制水土流失,退耕还林还草,打造旅游文化,推广生态风光的举措。 [结论] 根据早期“三生”空间的主要问题,高西沟做出适宜的优化策略,提高土地利用率,扩大林草面积,使绿地生态空间达到80%。农林牧的高效发展,生产、生活、生态的全面改善,使高西沟成为黄土丘陵区的生态示范代表。     

基于灰色系统理论的挠力河流域净耕地面积预测

[目的] 研究如何精准提取净耕地利用信息,为农田管理与耕地科学利用提供理论支持。[方法] 基于灰色系统理论提出净耕地预测思路,以典型粮食产区挠力河流域为研究区,在土地利用变更调查数据支持下,运用净耕地系数、突变检测模型、灰色动态模型（GM）等数理模型,提取并验证净耕地（包括旱地和水田）利用信息。[结果] 挠力河流域土地利用斑块面积变化表现出显著的“灰色”特征,对20 hm²等额面积区间的非旱地和非水田斑块面积累加处理,可增强数据列的规律性特征;GM （1,1）灰色系统模型和多项式预测方法均可较为准确地提取非旱地和非水田面积信息。2018年,挠力河流域旱地和水田的净面积分别是1.06×10⁶ hm²和3.87×10⁵ hm²,对应的净系数为97.65%和98.07%。[结论] 耕地斑块面积变化具有灰色特征,可采用灰色系统理论进行净耕地面积预测。     

中国东北漫川漫岗典型黑土区沟道侵蚀特征

[目的] 通过对450 km²黑土区进行实测调查,旨在评估研究区沟道侵蚀现状。[方法] 选取沟道侵蚀严重的450 km²的漫川漫岗黑土区为调查区域,首先在谷歌卫星影像上进行侵蚀沟识别和定位,再对侵蚀沟立体形态进行实地测量。[结果] ①研究区土地利用以耕地为主,耕地、建设用地、林地、草地分别占研究区总面积的85%,8%,6%,1%。②研究区坡耕地占86%,坡度0.25°~3.0°占64%,大于5°的占12%。③共有侵蚀沟1 049条,其中耕地中侵蚀沟577条,占总侵蚀沟条数的55%;沟壑密度1.2 km/km²,按沟壑密度衡量沟蚀强度为中度;沟壑面积比例为2.89%,以此界定沟蚀强度为剧烈。④研究区侵蚀沟平均长度、宽度、深度和面积分别为996,13.1,2.7 m和2.4 hm²。[结论] 漫川漫岗黑土区沟道侵蚀严重,主要危害坡耕地,但侵蚀沟相对较小,易于治理。     

西北干旱区绿洲县域3类空间冲突分析与模拟

[目的] 对西北干旱区绿洲县域3类空间冲突进行分析与模拟,为该区国土空间合理布局、区域可持续发展提供科学参考。[方法] 以西北干旱区绿洲县域——新疆麦盖提县为研究区,基于土地利用主导功能构建空间分类体系,将国土空间划分为城镇、农业与生态空间;根据景观格局指数构建空间冲突测度模型探讨2009—2019年空间冲突水平演变特征;通过CA-Markov模型预测2024年空间布局并分析冲突强度变化特征。[结果] ①3类空间呈现“两增一减”的变化动态,城镇空间面积呈逐年递增趋势,由1 537.74 hm²增加至4 582.24 hm²;农业空间由84 670.06 hm²增加至107 447.66 hm²;生态空间面积减少25 822.69 hm²。②2009—2019年空间冲突强度显著增强,中等空间冲突、较高空间冲突与高空间冲突评价单元所占比例分别增加了50.41%,13.45%,0.53%。③2024年城镇空间、农业空间将分别增加2 981.19和4 285.96 hm²,生态空间将减少7 267.16 hm²;冲突水平以所占比例为60.24%的中等空间冲突为主。[结论] 2009—2019年城镇空间、农业空间逐年增加、生态空间逐年递减,各类空间的无序变化导致空间冲突强度整体增强,通过预测2024年3类空间变化趋势与2009—2019年保持一致,并以中等空间冲突为主。     

生态脆弱区宜耕未利用土地开发适宜性评价——以山西省大同市为例

大同市地处我国西北部, 土地生态环境较为脆弱, 同时又是我国主要的煤炭生产基地, 人类活动对生态环境影响较大。为了合理确定大同市未利用土地开发为耕地的适宜性, 进而确定开发的空间和时序, 本文首先采用模糊综合评价法对大同市进行生态脆弱性分区, 分区结果为大同市南郊区、阳高县、左云县、天镇县属于生态环境重度脆弱区, 浑源县属于中度脆弱区, 广灵县属于轻度脆弱区, 新荣区、大同县和灵丘县属于微度脆弱区。在生态脆弱性分区基础上, 结合大同市生态环境现状以及农用地分等规程, 对宜耕未利用土地进行开发适宜性评价。结果表明: 大同市宜耕未利用土地总面积468 692.59 hm², 占未利用土地总面积的84.09%; 其中有205 165.81 hm²位于生态微度脆弱区内, 占宜耕后备土地资源的43.77%; 52 392.84 hm²位于轻度脆弱区内, 占宜耕后备土地资源的11.18%; 中度和重度脆弱区内宜耕后备土地资源面积为69 427.45 hm²和 141 706.49 hm², 分别占宜耕后备土地资源总量的14.81%和30.23%。微度脆弱区内的非常适宜级别的用地可以作为未利用土地开发为耕地的首选区域; 微度脆弱区内的较适宜级别的土地可以作为开发的备选用地; 对于中度和重度脆弱区内的非常适宜耕作的未利用土地, 在可能情况下尽量不作为第一开发时序用地。     

基于遥感与GIS的土地用途转移分析——以洞庭湖区为例

采用遥感、GIS一体化技术，以1989～1990、1999～2000年获取的陆地资源卫星Landsat TM或ETM图像为主信息源，对洞庭湖区近10年土地用途的转移变化进行了检测，对驱动变化的主要因素进行了分析。结果表明，1990年以来的10年间，耕地减少0.9万hm²，占总面积的比重减少了0.32%；各类建设用地总计增加了0.75万hm²，比重增加0.26%；水域增加0.16万hm²，比重增加了0.06%。林地略有减少，草地、未利用地略有增加。流失的耕地中，绝大部分被退田还渔还湖，或被建设用地所占用。建设用地的扩张占地中，耕地被占74.08%，林地被占20.86%。土地利用、土地价格及税收等方面的政策、城市化与工业化、农业结构的调整、以及科技的进步对土地用途的转移有决定性的影响。     

基于地形梯度的高山峡谷区土地利用时空格局及功能分区

[目的] 分析高山峡谷区土地利用情况及其地形梯度分布格局,并进行功能分区,为类似区域土地资源的可持续利用提供参考。[方法] 以云南省泸水市为例,采用地形位指数和分布指数系统分析高山峡谷区土地利用在地形梯度上的分布变化特征。[结果] ①泸水市土地利用具有显著的优势分布特征,2000-2018年,林地作为主导地类,其比例从77.50%增长至84.49%。建设用地也快速增长,由2 804.49 hm²增加到4 785.65 hm²。未利用地、耕地、草地逐渐向林地转变,面积分别减少了14 368.38,5 171.68和4 049.54 hm²,水域面积稳定在900 hm²左右。②泸水市土地利用格局在地形梯度上的层级差异十分显著,林地在整个地形梯度上具有统治地位,水域、建设用地、耕地广泛分布于中、低地形位,草地的优势区间位于坡度高但高程较低的中地形位,未利用地则在高地形位占据主导优势。③基于地形分异规律,泸水市可分为4大功能区：河谷集约发展区、陡坡综合治理区、中高山生态提升区、山顶生态封禁区。[结论] 高山峡谷区在地形梯度上形成了多层级独特的土地利用分布格局,具有分区发展的潜力,不同分区对应着不同的土地利用发展策略。     

宁夏土地利用碳排放强度时空变化与效应

[目的] 土地利用变化是影响碳排放和环境质量的重要驱动力之一。研究土地利用碳排放时空格局变化与效应,为制定低碳发展策略提供理论依据。[方法] 基于灰色理论和生态承载系数,利用1980—2020年宁夏回族自治区22个县区土地利用和能源消耗数据,分析了土地利用变化与碳排放强度变化及效应。[结果] ①碳排放变化量与土地利用变化之间具有密切的关联性。其中,建设用地与碳排放的关联度最大,为0.95。②1980—2020年宁夏土地利用类型碳排放量净增加了5.24×10⁷ t,增幅625.43%。建设用地面积以年均4.42%的速率增长,碳排放量增幅达2 385.85%;草地面积减少了2.95×10⁵ hm²,碳汇量减少了5.80×10⁴ t;林地对碳汇的贡献超过75%,且随林地面积的不断增大而增加。③1980—2020年宁夏土地利用碳排放强度以年均0.25 t/hm²的速率增大,中度及以上等级覆盖面积逐渐增大,在空间上形成沿黄城市碳排放强度高于中、南部的分布格局。④宁夏各县区碳排放生态承载系数空间差异明显,碳生态容量表现出北弱南强的分布格局。[结论] 1980—2020年宁夏土地利用碳排放强度逐渐增大,北部沿黄河各县区碳生态容量逐渐减小,中南部县区碳生态容量增大,但减排压力较大。建议优化建设用地空间格局,增加混交林面积,增强森林碳汇能力。     

东露天煤矿区采矿对土地利用和土壤侵蚀的影响预测

黄土区大型露天矿区是一种剧烈的人工扰动区域，采矿活动对土地资源和生态与环境破坏非常严重，正确预测人工开采引发的人为加速土壤侵蚀与土地利用变化，可为生态脆弱煤矿区的生态恢复和重建提供依据。该文采用RS、GIS技术、统计分析、类比和趋势外推相结合的方法，对东露天矿区2005～2080年的土地利用变化和水土流失进行了预测性研究。结果表明：75年间，在没有采取生态重建的措施下，农用地减少3666.07 hm²，未利用地减少1402.13 hm²，居民点用地减少121.80 hm²，全部变为独立工矿用地。土地利用结构和类型由多样性向单一类型的裸露的独立工矿用地发展，水土流失量由54.50万t/a变为77.85万t/a。     

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.