基于景观生态安全格局的成都平原与龙门山脉过渡带土地资源开发利用

[目的]基于景观生态安全格局的土地利用研究,为缓解人地矛盾、经济发展与生态保护提供科学依据。[方法]以成都平原与龙门山脉过渡带的四川省绵竹市为例,基于遥感和GIS技术,在提取和分析20a来土地利用变化及其地形因子响应基础上,以生态用地保护为目标,选取地形和土地覆盖类型为阻力因子,应用最小累计阻力模型构建景观生态安全格局。通过与土地资源现状的叠加,对不同景观安全水平的土地资源进行划分。[结果]研究区土地资源分为优先开发、适度开发、限制开发、禁止开发等4种类型,其面积分别达7 218.39,17 974.75,21 545.39,77 791.46hm2,并分析各类型土地利用特征,提出了相应的土地资源开发利用规划。[结论]基于景观生态格局理论与方法,提出的不同生态安全水平的土地用地规划,有利于区域生态安全保护和土地资源持续性利用。     

CACE模型及其在生态安全格局优化中的应用

中国城镇化进程的快速推进,使得各种建设活动对土地资源的需求日益增加,引发一系列生态环境问题,特别是在生态脆弱区,土地资源不合理的开发利用加剧了区域生态安全风险。因此,为探究区域生态安全格局优化的途径方法,保障区域生态安全和土地资源合理利用,该研究通过解译判读怀来县1993年、2003年和2013年3期遥感影像,运用土地利用变化信息图谱及构建建设用地和生态用地竞争优势模型,分析了怀来县土地利用变化热点区域及建设用地与生态用地竞争优势分布区,划分了建设用地与生态用地优势分布临界线,同时,基于景观生态学理论,构建了怀来县综合生态安全格局,并将建设用地与生态用地竞争优势分布区应用于生态安全格局优化。结果表明:怀来县综合生态安全格局面积为1 470.59 km2,占怀来县总面积的82.51%,基本安全格局分布在临界线外围,满意安全格局外围主要沿临界线分布、理想安全格局主要分布在临界线内部。基本生态安全格局受到建设用地扩张的压力相对较小,满意生态安全格局主要位于生态优势区,在一定程度可以起到对建设用地扩张的限制作用,作为怀来县重要的生态缓冲区,理想安全格局受到建设用地扩张的压力较大,其内部应注重生态廊道网络建设,引导自然斑块以廊道或小型斑块的形式分散地融入建设用地中。研究方法和结果可以为区域生态规划和城乡布局等提供决策参考。     

基于生态安全的青龙满族自治县土地利用冲突识别

生态安全视角下土地利用冲突识别有助于协调生态保护与社会经济发展之间的平衡。基于青龙满族自治县2016年土壤、气象、土地利用等数据,首先,按照识别源地、廊道、缓冲区的步骤构建研究区生态安全格局;其次,利用GIS空间分析功能,揭示耕地、建设用地与不同等级生态安全用地的空间叠加关系,由此识别生态安全视角下耕地、建设用地、综合用地的土地利用冲突空间分布特征。结果表明:青龙满族自治县土地利用冲突总体分布较为分散,其中耕地极严重冲突区主要分布在祖山镇、龙王庙乡、青龙镇,该类地区为人口密集区,对农产品需求较大,导致耕地对生态安全空间的占用;建设用地极严重冲突区主要分布在青龙镇、祖山镇、大巫岚镇,该类地区为经济发展密集区,城镇扩展导致建设用地对生态安全空间的占用;综合土地利用极严重冲突区主要分布在祖山镇、龙王庙乡、青龙镇。针对土地利用冲突高发区,应通过调整土地利用结构、转变经济发展方式等措施达到保障区域生态安全的目的。     

甘州区土地利用格局变化及生态服务价值变化评价

生态系统服务功能价值评估研究是可持续发展评估研究的关键内容和焦点,通过分析甘州区土地利用及其变化,并在此基础上,对甘州区生态服务功能价值评价进行研究。通过研究分析,结果表明:2005~2020年间,甘州区土地利用格局变化总体趋势为少数几种土地利用类型占主导地位的情况得到缓解;土地利用均匀度指数略微有所升高,说明社会经济的发展较2005年相比更为平衡;土地利用多样化程度也稍有增加。而这一变化直接影响到生态服务功能价值的变化。甘州区生态用地的结构和布局规划合理,能够满足社会经济发展和生态建设对生态用地的需求。期望通过建立环境友好型土地利用模式,优化生态用地结构与强化土地生态功能,以确保生态安全目标的实现。     

干旱区河谷城市土地利用生态风险动态预测——以新疆伊宁市为例

土地利用规划和土地生态安全是土地资源可持续利用的基础和核心。基于伊宁市土地利用总体规划(2010—2020年),依照规划基期年及末期年土地利用结构特征,借助土地利用变化、土地利用类型动态度和生态风险空间分析方法,测算了土地利用生态风险指数。并通过运用ArcGIS 9.3对生态风险进行了系统采样、半变异函数分析及空间插值,研究伊宁市土地利用生态风险动态演变和空间分异特征。结果显示:伊宁市土地利用总体规划对全市土地利用空间结构进行了较大调整,土地生态风险具有明显的区域性,生态安全状况由北向南逐渐加重,且高、较高风险区在南部区域呈圆环式蔓延趋势。在未来土地利用变更中应加强生态环境保护意识,在伊宁市河谷构建良好的生态用地格局,提高土地利用的综合效益。     

鄱阳湖区土地利用景观格局特征研究

在RS与GIS技术的支持下，该文对鄱阳湖区1990～2002年间的土地利用景观变化进行了分析。研究结果表明，1990～2002年鄱阳湖区面积变化的趋势是耕地减少、林地增加、草地减少、水体增加、居民点与工矿用地大幅度增加，未利用地维持不变。利用二级土地利用景观类型，对景观变化的原因进行了分析。利用多样性指数、优势度、分维数、破碎度等景观指数对鄱阳湖区土地利用景观格局特征的研究表明，1990～2002年鄱阳湖区土地利用景观格局总体变化趋势是多样性增加、优势度减少、分数维减少、破碎度增加。最后，该文利用典型相关分析法对鄱阳湖区景观格局变化的社会经济驱动力进行了定量分析，认为导致景观分维数、景观破碎度变化的主要驱动力是人口与国内生产总值，导致景观多样性和优势度变化的主要驱动力是境内公路里程与农村居民年均纯收入。     

鄱阳湖区土地利用与景观格局变化研究

通过获得的遥感数据资料,运用地理信息系统的空间分析和数理统计功能以及景观分析软件Fragstats分析了鄱阳湖区1985—2005年的土地利用变化特征及各种土地利用类型之间的转化情况和景观指标变化特点。结果表明：（1）鄱阳湖区在1985—2005年土地利用变化的特点是：耕地与水域的变化情况完全相反;其次是建设用地持续增加,而其他土地利用类型的变化幅度不大;（2）从整体上来看,耕地与水域之间实现转换,而建设用地的增加主要来自于耕地;同时,鄱阳湖区的土地利用变化在空间上存在着很大的差异性;（3）从景观格局指数的变化来看,鄱阳湖区的景观异质性程度在逐渐提高,土地利用向着多样化和均衡化的方向发展。     

基于不同种类生态安全的土地利用情景模拟

为解决中国城市化进程中日益严峻的生态和环境问题,合理确定未来土地利用结构和布局是关键,开展不同约束条件下的土地利用情景模拟研究对于科学规划和辅助决策具有重要意义。该文首先采用景观安全格局理论构建了曹妃甸新区综合生态安全格局,然后基于GIS和CA-Markov模型,提出了一种基于生态安全格局的土地利用情景模拟方法,并借助于2005年和2013年2期土地利用遥感解译图对曹妃甸新区生态安全格局保护与无生态保护2种土地利用情景下2021年的土地利用结构和布局进行了预测和模拟,结果显示,曹妃甸新区生态安全格局总面积为1 058.80km2,占区域总面积的53.53%,其中底线生态安全格局面积为312.67km2,占区域总面积的15.81%。生态安全格局保护情景下,底线生态安全格局范围内新增建设用地为0,且总生态安全格局范围内新增建设用地比无生态保护情景减少17.47km2。生态安全格局保护情景下,景观更趋于破碎化,景观的形状更趋复杂,建设用地与生态用地的分布更趋合理。该研究方法和结果可为区域城市规划和生态保护提供技术支撑和决策参考。     

干旱区绿洲县域土地利用规划中土地生态安全预测——以新疆阿瓦提县为例

土地生态安全是土地资源可持续利用的核心和基础。通过运用土地利用变化、生态风险空间分析方法,基于阿瓦提县土地利用总体规划（2010—2020年）,根据规划基期年及期末年土地利用结构特征,测算了土地利用生态风险指数。并运用ArcGIS 10.0对生态风险采样结果进行半变异函数分析和空间插值,分析阿瓦提县土地利用生态风险动态演变和空间分异特征。结果表明,阿瓦提县土地利用总体规划对全县土地利用空间结构进行了较大调整,阿瓦提县土地生态风险有明显区域性,生态安全状况由南向北逐渐加重,且北部较高风险区域有向西北和西南方向蔓延趋势。在未来土地利用变更中应加强生态环境保护意识,在阿瓦提绿洲构建良好的生态用地格局,提高全县生态系统服务功能。     

基于生态安全的土地利用结构优化研究

满足生态安全的土地利用结构优化是协调社会经济发展与生态环境间矛盾、实现土地持续利用的有效途径。本文以保定市土地利用结构数据(2002~2009年)为基础,引入反映生态指标生态绿当量和土壤有机碳储量,评价研究区土地利用结构在不同发展阶段的生态效益,并且借助TOPSIS模型对历年土地利用结构进行生态合理度评价。在此基础上以经济发展和生态效益并重为目标,构建多目标优化模型,获得保定市2020年土地利用结构优化方案,调整内部用地结构,注重生态用地保护,生态效益和生态合理度得到提升,进而提出合理利用土地资源的建议。研究结果为保定市土地利用可持续发展以及土地利用总体规划修编提供借鉴和指导。     

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.