综合土地多功能与适宜性的南京市溧水区"三生"空间划定

区域"三生"空间的划定是其生态文明建设的重要组成部分，也是其国土空间规划与治理体系的基础。划定"三生"空间应以土地利用多功能性分析框架为指导，突出土地主导功能，并考虑其用地分布现状及功能特征的时空变化趋势。该研究以南京市溧水区为例，在土地多功能评价和"三生"空间适宜性评价的基础上，综合其土地多功能及变化趋势和"三生"空间适宜性划定研究区"三生"空间。结果表明：1）10年间研究区生产与生活功能下降，生态功能提升，各功能高低值所在区域也有变化，生产与生活功能、生态与生产功能表现出一定的相关关系；2）研究区生产空间适宜性差异最大，与耕地的分布存在高度的关联。生活空间适宜性差异最小，但其均值最高，呈由镇中心向周围递减的分布。生态空间适宜性均值略低于生活空间，在各镇间较为平均；3）研究区各乡镇"三生"空间综合评价结果比适宜性评价结果的耦合协调度提升，据此划定的生产、生活、生态空间在研究区占比分别为39.63%、22.72%、37.65%，生产空间集中在研究区中部和西北部，生活空间主要分布在研究区中部，而生态空间则在研究区南部。综合土地多功能与适宜性的"三生"空间划定结果更精细，且三生空间的协调性也更高，可以为研究区进一步的国土空间规划提供参考。     

基于Markov-FLUS-MCR模型的晋中市"三生"空间优化

三生空间优化是落实各级国土空间规划和引导土地合理开发保护的重要基础。该研究利用Markov-FLUS模型模拟预测2025年晋中市"三生"空间，选取最小累计阻力（Minimum Cumulative Resistance，MCR）模型评价国土空间开发适宜性，在空间上叠加分析模拟预测结果与开发适宜性评价结果，对晋中市进行"三生"空间优化。结果表明：1）从模拟预测结果来看，Markov-FLUS模型模拟2018年晋中市"三生"空间变化，与实际数据对比精度达到97.17%，模型具有适用性。2025年晋中市生产与生活空间均呈增长态势，其中生产空间涨幅较大，增长面积达813.53 km2，生态空间面积减少892.65 km2。2）从开发适宜性来看，MCR模型将晋中市国土空间分为5种类型：生态保护区、生态优化区、限制开发区、优化开发区和适宜开发区。生态优化区面积最大为4 994 km2，占整个研究区的30.59%，适宜开发区面积最小为1 546 km2。3）"三生"空间优化后，晋中市划分为生产空间、生态空间、生活空间、生产-生活空间、生产-生态空间、生活-生态空间和生产-生活-生态空间7种类型，表现出"整体集聚，局部零散"的空间分布特征，其中生态空间面积占比最大，为41.20%。研究结果有助于促进"三生"空间优化理论与方法的深入研究，也可为晋中市国土空间合理开发保护提供参考。     

基于适宜性和空间功能值的德兴市矿粮复合区“三生”空间优化研究

[目的]深入开展“三生”功能评价与空间调控优化，协调重构不合理的空间布局与结构，缓解矿粮空间冲突，为国土空间治理和区域高质量发展提供参考。[方法]以德兴市矿粮复合区为例，结合空间适宜性评价、功能值测算与空间自相关分析，基于AVC“三力”理论对研究区进行“三生”空间优化研究。[结果](1)农业、工业生产空间分别集中于西南部和北部，生活空间集中度自西北向东南递减，而生态空间分布广泛且整体均衡；(2)生产、生态空间多呈现聚集态势，而生活空间功能聚集性较弱，呈零星分布，且矿区对其空间适宜性、功能值及聚集度有负面影响；(3)空间重构后，生活、生态空间功能值分别从1.948 6亿元、90.755 0亿元提升至1.951 8亿元、90.778 9亿元。[结论]综合考虑适宜性、空间功能值与集中度进行空间优化与重构，研究区生活与生态空间功能值有所提高，各类空间分布趋于集聚态势，缓解了矿区对于人们生活与粮食生产的负面影响。未来应针对各类空间进行系统治理与管控，并严格控制矿区开发，以保障生产、生活与生态功能。     

基于洛伦兹曲线和土地利用转型的喀斯特山区“三生”空间分布研究

[目的]对贵州省都匀市"三生"空间分布进行研究,为喀斯特山区"三生"空间可持续发展、县域科学开展国土空间规划、生态环境保护提供参考依据。[方法]采用洛伦兹曲线、基尼系数及转型模型对都匀市2009—2018年"三生"空间进行综合研究。[结果]①2018年,都匀市"三生"空间现状主要以生态空间为主,生态空间占都匀市国土面积的69.19%,比例较高;其次为生产空间,比例为26.87%;而生活空间则占比相对较小。②2009—2018年间生产空间和生态空间面积呈现出下降趋势,生活空间面积则呈现出增长趋势,从二级空间转移来看,城镇和农村生活空间面积增长来自农业生产空间和林地生态空间,城市建设发展占用部分林地资源和农业资源。③从2009—2018年洛伦兹曲线和基尼系数来看生态空间和生产空间分布相对平均,而生活空间与其他空间相比更远离绝对平均线,下凹程度大,2009—2018年基尼系数均介于0.3～0.4间,生活空间分布基本合理。④从区位熵来看,生态空间优势区域主要为研究区西部地区,生活空间优势区域主要集中在中部地区,生产空间优势区域主要为南部及东部地区。[结论]都匀市"三生"空间分布基本合理,城市以生态空间为主,在今后城市建设中,应在保障生态空间的同时,合理进行城市发展,避免过多占用生态用地。     

环滇池地区2000-2020年“三生”空间格局演变及其驱动力

[目的] 研究环滇池地区“三生”空间格局演变及驱动力,为研究区国土空间优化和滇池保护提供支撑。[方法] 基于环滇池地区2000,2005,2010,2015和2020年5个时期土地利用和社会经济数据,采用空间分析、动态度、转移矩阵、景观格局指数和地理探测器等方法,分析环滇池地区2000—2020年“三生”空间格局演变及驱动力。[结果] ①环滇池地区生态空间和生产空间持续缩减,生活空间逐渐增加;“三生”空间综合动态度波动上升,但生产空间和生态空间单一动态度持续下降;生态空间和生产空间缩减区域与生活空间扩张区域均主要位于滇池周边;官渡区、安宁市和呈贡区“三生”空间变化最为剧烈。②空间转移特征表现为：生态空间和生产空间主要转向生活空间,生活空间主要转向生产空间;生态空间主要来源于生产空间,生产空间主要来源于生态空间,生活空间来源于生产空间和生态空间。③景观格局指数显示,“三生”空间破碎化有所降低,但仍处于较高水平,斑块形状先复杂后简单,凝聚程度先下降后紧实,“三生”空间中斑块呈现均匀化分布趋势,景观多样性增强。④自然地理因素是“三生”空间格局演变的基础性决定条件,社会经济因子是“三生”空间格局演变的直接推动力,政策规划因子是“三生”空间格局演变的间接推动力。[结论] 环滇池地区“三生”空间动态变化显著,空间差异明显,格局演变受到自然地理、社会经济和政策规划因子多重作用。     

基于“三生”适宜性的典型喀斯特乡村土地利用冲突识别及分析

[目的]科学地识别喀斯特乡村生产-生活-生态(“三生”)用地冲突,分析其区域差异特征,为优化国土空间布局,推动乡村振兴提供理论参考。[方法]以贵州省喀斯特中山、喀斯特盆地、喀斯特槽谷、低山丘陵4种喀斯特地貌的典型乡村为例,构建了“三生”适宜性评价体系及用地冲突识别矩阵,并探讨“三生”用地冲突在不同地形梯度上的分布格局。[结果](1) 4个典型喀斯特乡村的“三生”适宜性用地空间分布和结构组成存在明显差异,且在空间上存在重叠等突显土地利用冲突现象的特征;(2)土地利用冲突以“生产-生活冲突”和“生产-生态冲突”为主,前者主要分布于地势起伏小的生产-生活热点区,后者主要分布于坡地及生态脆弱区;(3)随着地形梯度增加,冲突强度逐渐降低,即冲突激烈区主要集中于低地形位,冲突微弱区和用地适宜区在高地形位上分布更显著。[结论]典型喀斯特地貌背景下,人类活动受到严重制约,喀斯特乡村土地利用冲突特征明显,亟需因地制宜地优化区域发展空间布局。     

基于“三生”空间的重庆市土地利用演变与城镇化关系研究

[目的] 分析重庆市土地利用时空演变规律,探究土地利用转型及景观格局响应的演变特征与城镇化的关系,为重庆市"三生"土地规划与城镇化可持续发展提供数据支持。[方法] 基于"三生空间"功能分类的视角构建用地分类标准,利用2000,2010,2020年土地遥感影像和夜间灯光数据,采用转移矩阵、相关性分析及回归分析法进行分析。[结果] ①2000-2020年重庆市生产、生态空间总体减少,生活空间持续扩张。2000-2010年,生产、生态空间减少191.87,252.95 km²,生活空间增大446.03 km²;2010-2020年,生产空间面积减少13.76 km²,生态空间减少324.05 km²,生活空间增大314.87 km²。②重庆市生产功能向生活功能转化较为明显。随着城镇化加强,生态空间转向生产空间显著,功能转变明显聚集于重庆市中心区域。③重庆市空间景观破碎度减小,景观复杂度逐渐提高,林草水生态空间占据主导优势。④2000-2010,2010-2020年土地利用面积变化对夜间灯光值的影响存在差异;2000年,城镇生活空间、农村生活空间变化对夜间灯光变化影响起主导作用,而2020年工业生产空间、城镇生活空间变化对夜间灯光变化影响较强。[结论] 重庆市各类空间发生相互转换,利用不同"三生"空间类型变化和城镇化的关系,推动土地规划与城镇化协调发展。     

“三生”空间视角下喀斯特山区流域景观生态风险的时空分布特征

[目的]深入分析喀斯特流域景观生态风险变化规律,为山区流域制定生态风险防控措施与景观管理规划提供科学参考。[方法]以典型喀斯特流域红水河流域贵州段为研究区域,从“三生”空间视角出发,采用GIS空间分析、景观生态风险指数等方法探究了研究区景观生态风险的时空变化机理,并借助分布指数方法分析了景观生态风险时空分布与地形地貌的关系。[结果](1)自2000年来,红水河流域基于“三生”空间的用地转型表现为生产、生态空间减少而生活空间快速增加,不同用地类型的转移引起区域景观生态风险变化的贡献率大小不一。(2)2000—2020年期间景观生态风险整体呈缓和趋势,红水河流域南部的景观生态风险总体优于其北部地区。(3)从景观生态风险在地形位梯度上的分布看,景观生态风险程度与地形位梯度成反比关系;另外,非喀斯特区和纯喀斯特区景观生态风险要低于亚喀斯特区。[结论]红水河流域景观生态风险虽有所好转,但部分景观生态问题依然突出,需要加强对生态环境的治理保护。     

三峡库区县域"三生空间"时空演变特征与情景模拟

探究区域"三生空间"时空演化规律和未来发展态势是进行国土空间规划和治理的重要基础，可为区域国土空间有序利用和整治修复指明方向。该研究运用转移矩阵、动态度模型分析1990－2020年三峡库区重庆市石柱县"三生空间"规模、结构及格局的动态演变特征，基于FLUS模型模拟在自然发展、耕地保护和生态保护3种情景下石柱县2035年的国土空间格局。结果表明：1）石柱县以生态空间为主，生产空间次之，生活空间占比最小，总体呈现出西部以生产空间为主，东部以生态空间为主的空间特征。2）研究期内，石柱县生产空间小幅减少，生态空间略有增加，生活空间增幅显著。"三生空间"转移呈现出"整体分散、局部集中"的空间特征。3）3种情景模拟下，石柱县"三生空间"变化显著。自然发展情景下，农业生产空间向其他空间均有转出，但转出转入面积基本平衡，其他空间均呈现出不同程度的扩张，而绿被生态空间呈现大幅度萎缩趋势。耕地保护情景下，农业生产空间的转出得到严格控制，耕地得到有效保护，但绿被生态空间成为最大的转出空间。生态保护情景下，生态空间格局得到有效保护，其面积有所增加，但农业生产空间萎缩明显，其他类型空间面积均有所增加。总体而言，研究结果与研究区社会经济发展趋势和区域发展格局形成较好的对应关系，可为研究区国土空间治理和优化提供理论支撑。     

新疆乌鲁木齐市“三生”用地的空间冲突研究

[目的]探析新疆乌鲁木齐市“三生”用地变化及其引起的空间冲突变动,为该地区的土地资源优化配置提供参考依据。[方法]利用外部压力、脆弱性和稳定性3个因子构建格网尺度下的空间冲突测度模型,对该地区2000—2018年空间冲突时空分异特征进行定量评价。[结果](1)2000—2018年,乌鲁木齐市北部为城市生活用地的主要增长方向,农业生产用地空间格局呈现破碎化趋势,生态用地是乌鲁木齐市三生用地的主要组成部分,应避免人类活动对新增核心生态用地的占用。(2)各个时期乌鲁木齐市“三生”空间冲突等级均表现为：稳定可控>轻度冲突>中度冲突>重度冲突。(3)重度冲突空间单元增幅最大,表明乌鲁木齐市重度冲突失控的地区范围有扩大的趋势。这应是乌鲁木齐市空间冲突调控的重点区域。(4)不同空间类型的空间冲突存在一定差异。乌鲁木齐市冲突强度从大到小依次为：生产空间>生活空间>生态空间。[结论]乌鲁木齐市“三生”用地变化与区域经济社会发展具有较强的吻合性,未来应逐步改变生活空间过速扩张而导致冲突水平逐渐增强的现象。应更加重视城市生活用地的动态监测,保护核心生态用地,以实现“三生”用地更...     

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.     

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.     

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.     

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.