土壤空间分布多样性与景观指数的关联分析

选取河南省中部典型样区为研究对象,利用仙农熵变形公式计算了1 km×1 km、3 km×3 km、5 km×5 km三种网格尺度下的土壤空间分布多样性,运用GIS技术和灰色理论探讨了多样性指数与景观指数之间的关联性,综合评价了研究区的土壤类型空间分布格局,研究表明:平均斑块形状指数大多小于2.0,说明土属斑块形状相对比较规则,受人为干扰的程度比较高;同一土属的空间分布多样性指数在不同网格尺度下具有相似的分异规律,其中空间分布相对比较均匀的土壤是黄砂潮褐土(多样性指数为:0.790);景观分离度指数与土壤空间分布多样性之间存在一定的负相关关系,相关系数为R2=0.866;平均斑块面积指数与空间分布多样性指数之间的回归方程为y=0.099ln(x)+0.644,R2=0.625;面积指数与土壤空间分布多样性之间存在明显的正相关关系,相关系数R2=0.865。     

以地形为基础的河南省域土壤多样性的格局

选取河南省作为研究区域,对其DEM数据进行处理得到河南省地形分类图。以地形分类图为基础用经典的土壤构成组分多样性算法计算丰富度指数S、多样性指数H′和均匀度指数E,再使用改进的仙农熵指数(Yh)计算不同地形下每个土类面积占本土类总面积的比例及其在1 km×1 km网格尺度下的土壤空间分布多样性。结果表明:河南省主要有平原、丘陵、山地和盆地4种地形,且以平原地形为主;河南省有15种土类,从平原、丘陵、山地到盆地地形,土壤丰富度依次递减,且随着地形面积的增加,土类丰富度指数S也不断增加且二者拟合函数为多项式函数;多样性指数H′测度分析显示,4种地形下从土类、亚类到土属多样性值均处于递增趋势,且从平原、丘陵、山地到盆地地形,土类和亚类的多样性值呈"先上升后下降"趋势,土属一直呈"下降"趋势;土属的均匀程度高于土类和亚类的均匀程度,且从平原、丘陵、山地到盆地地形均匀度指数E/土壤构成组分多样性均呈"先上升再下降"趋势;土壤分支率与构成组分多样性间的拟合函数均为多项式函数。经研究,河南省地形和土壤的形成及空间分布多样性有密切的联系,如河南省广阔的平原赋予了潮土分布的地域背景条件,山地地形中山间谷底仅有少量潮土分布,然而平原地形下潮土空间分布斑块多、斑块面积大、空间分布多样性指数高而成为平原地形下空间分布离散性强的优势土壤类型,同时平原也是省内极少面积盐土和碱土仅有的分布区域;同样,山地和丘陵地形下面积最大且空间分布多样性值最大的土类均为褐土;盆地地形以黄褐土、砂姜黑土为主。通过对比,不同地形下指数Yh在空间分布表达上优于其他指数。     

市域尺度的稀有濒危土壤类型的界定与评价——以郑州市为例

在当今世界城市化高速发展的背景下,土壤资源的保护也越来越受到人们的关注,土壤多样性骤减也成为了全球关注的焦点,界定和评价稀有濒危土壤对于保护土壤资源及其多样性具有非常重要的指导意义。本文以郑州市为例,应用土壤类型密度和土壤多样性两种多样性测度方法分别对郑州市1 km×1 km和5 km×5 km网格尺度下基于不同分类级别的土壤空间多样性分布格局进行了分析和定量化研究;利用1988、2001、2007和2013年4期遥感资料进行土地利用分类,结合基于第二次土壤普查的1∶20万郑州市土壤图,采用多时相连续对比法对郑州市近25年来土地利用变化对土壤的扰动情况进行了分析;结合土壤多样性方法和传统评价方法界定和评价了稀有濒危土壤。结果表明,郑州市土壤整体分布较为均匀,且随着分类单元级别的降低,构成组分多样性指数升高,即分类越细,土壤类型分布越均匀;1988~2013年郑州市土壤受到非农建设扰动剧烈,干扰比例为16.01%,随着时间的推移,土壤受扰动的速度是呈上升趋势的;稀有土属有16种,濒危土属有2种,稀有濒危土属有4种。截止2013年濒危土属整体受到扰动比例高达35.38%,而稀有土属受到扰动比例为8.76%。     

地形及土壤多样性与耕地动态变化的相关分析

本文以河南豫北、豫中和豫南3个典型样区为研究对象,运用地统计学方法,从多样性、相关性角度定量分析了地形、土壤的多样性特征及其与耕地变化(2001年、2007年和2017年)面积的空间分布多样性特征的关系,以期为耕地资源动态变化的驱动力分析及合理利用提供新的研究角度。研究表明:1)豫北和豫中样区的地形构成组分多样性呈现出均匀性,豫南样区表现为相对单一性;各研究区的地形空间分布多样性为平原丘陵山地。2)豫南的土壤构成组分最为均匀且丰富,豫中的土壤构成组分相对单一;各研究区的典型土壤各异但总体上分布皆较均匀,各样区的土壤空间分布多样性的显著差异与地形条件密切相关。3)研究尺度影响地形、土壤空间分布多样性特征的表达, 3 km×3 km网格是相对适宜的研究尺度。4)地形和土壤的空间分布多样性指数与耕地变化面积空间分布都具有明显的相关性,其中地形中平原相关性较大,达0.95左右;各样区典型土壤如豫南的水稻土,豫中、豫北的褐土以及豫北的潮土的相关性更为明显,达0.9以上。综合来看,典型样区的地形、土壤因子的构成组分多样性及空间分布格局有显著差别;在不同网格尺度下,耕地的变化面积与地形、土壤因子的空间分布多样性指数密切相关。     

河南省成土母质与土壤空间分布多样性的特征

成土母质作为土壤发育的主要形成因素,二者间的关系密切。选取河南省作为研究区,从多样性的角度运用经典的仙农熵测度方法分析成土母质和土壤要素的构成组分多样性、不同母质基础上各土壤分类级别的多样性特征,并运用改进的仙农熵公式研究5 km×5 km网格尺度下不同成土母质对土类空间分布离散程度的影响及不同成土母质和土壤的空间分布多样性特征和相关性。结果表明:(1)成土母质类型虽少,但其构成组分多样性高于土类,这与二者分类系统的分支率有关;(2)6类母质类型中,残积、坡积物母质面积最大且发育土壤类型最为复杂;15种土壤类型与6类母质之间的关系有一对多、一对一和多对一3种类型;(3)不同母质上发育的土类的空间分布离散性程度不同,残积、坡积物母质上分布的优势土类为粗骨土,河流冲积物和河湖相沉积物母质上的优势土类分别是潮土和砂姜黑土,洪积物和黄土与红土母质上发育较好的两种土类为黄褐土和褐土,风积物母质上仅发育了风砂土一种土类;(4)潮土和河流冲积物母质分别是是河南省面积最大、空间分布多样性值最高的土类类型和成土母质类型,且成土母质与土类空间分布多样性间存在不同程度的相关性。综上,河南省的6大类成土母质与15种土类的构成组分多样性和空间分布离散性程度存在差异,且二者的空间分布多样性间存在一定的相关性。     

河南省多级地貌特征及与土壤多样性的关系

从土壤多样性向地多样性发展符合土壤地理学的研究趋势,选择河南省作为研究区,将地貌这一主要的地学要素加入到土壤多样性的研究中,并用改进的仙农熵公式对多级地貌空间分布多样性及其与土壤多样性的相关性进行探讨。首先,对河南省1︰175万地貌类型图进行矢量化得到地貌类型等级系统;然后,对地貌和土壤的构成组分多样性和2种不同分类体系的分支率进行计算并分析其特征;最后,在3 km×3 km网格尺度下分析地貌和土壤多样性间的相关性。研究表明:河南省共有3个一级地貌,12个二级地貌和37个三级地貌;随着土壤和地貌分类的等级细化,其分类个数和构成组分多样性值均呈上升趋势,即土壤和地貌所有分类单元在数量构成上的均匀程度越来越高;两种分类系统中,土壤分类较地貌分类有更详细的分类体系,且分支率有较大范围的变化;河南省一级地貌、二级地貌和三级地貌的空间分布多样性值和面积值均最大的类型分别是流水地貌、冲积平原和泛滥平坦地,是不同级别的优势地貌类型;一级地貌类型与土类、亚类和土属多样性间存在紧密的相关关系,且以流水地貌与土壤多样性间的相关性最强。     

河南省地形、土壤和地表水体多样性格局特征

在水土资源多样性的研究中,地形要素对其空间分布形式和内在联系有重要影响。选取河南省作为研究区,在1 km×1 km网格尺度下以变形仙农熵公式计算河南省的地形空间分布多样性和土壤空间分布多样性(土类级别)及关联性,并将河南省划分为6个面积相近的次级区域,用空间分布面积指数(Y_h)计算地形、土壤的构成组分多样性,用空间分布长度指数(MSHDLI)计算地表水体多样性,对以上特征及关联性进行研究。结果表明:平原和潮土是河南省面积最大且空间分布离散性最高的地形类型和土类。地形与土壤之间关系密切,有76%以上的相关系数r值大于0.50,相关性高;6个分区中,东部分区为单一的平原地形但MSHDLI值次高,平原地形水系发育好,西部分区地形复杂且以山地为主但地表水体多样性指数MSHDLI值最小,山地条件下水系发育较简单;研究区面积相近的情况下,土类构成组分多样性值主要取决于土类间面积大小的均衡程度,与土类面积比例平均变化量之间呈负相关,R~2值为0.94;面状的地形和土壤构成组分多样性指数与线状的地表水体多样性指数间无明显相关性。综上所述,地形、土壤和地表水体三要素间关系密切,共同影响地多样性的空间格局。     

河南省土壤与植被空间分布的多样性特征研究

植被作为土壤发育的主要形成因素之一,二者间关系密切。以河南省为研究样区,在中国1∶100万植被数据库的基础上获取河南省三级植被分类图,并运用改进的仙农熵公式计算植被和土壤要素的构成组分多样性及5 km×5 km网格尺度下二者的空间分布多样性。接着,将河南省划分为6个面积相近的次级研究区探讨不同分区优势植被(栽培植被)下发育的土壤类型状况。最后,计算一级植被类型和土类空间分布多样性的相关性。结果表明:①随着分类级别由高级别向低级别变化,植被和土壤要素的丰富度指数和构成组分多样性均呈上升趋势,且土壤类型的丰富度指数和构成组分多样性值整体上均大于植被类型的对应值。②栽培植被、两年三熟或一年两熟旱作和落叶果树分别是河南省的一级和二级优势植被类型,三级植被类型中有75%的区域被农作物覆盖,且甘薯、花生、大豆和小麦在河南省的种植比例高。③在6个不同的次级研究区内,西部分区栽培植被下发育的土类个数最多,但其面积在6个分区中最小;东部分区土类个数和构成组分多样性值均最低,但其面积最大。④11个一级植被类型与15个土类空间分布多样性间存在一定的相关性,相关比例达到61%。综上,植被和土壤类型的发育程度和...     

郑州市土壤多样性和土地利用多样性研究及关联分析

以郑州市为研究对象,将多样性理论及其测度方法应用于土壤和土地利用多样性研究.选取2004年和2009年两个时期的TM影像进行土地利用分类,并基于第二次土壤普查的郑州市土壤矢量数据,对郑州市土壤和土地利用的组成分布多样性和空间分布多样性进行了初步分析和定量化研究,探索了土壤和土地利用之间的关联性。结果表明:郑州市土壤构成组分较为复杂,其组成分布多样性指数取值0.776,土地利用组成分布多样性指数由2004年的0.610增加为2009年的0.651;郑州市同一土属或土地利用类型的空间分布多样性指数在不同网格尺度下存在相似的分异规律,其中空间分布最离散的土壤类型为砂土,空间分布最离散的土地利用类型为耕地;在3种空间网格尺度下,城镇建筑用地、农村居民点和工矿用地与各典型土壤的关联系数随研究时期推进均呈不同程度的增加趋势。     

基于仙农熵的土壤多样性和土地利用多样性关联评价

以南京市为例,将多样性理论与方法应用于土壤和土地利用相关性评价中,对该市1986年和2003年的遥感数据进行了土地利用分类,计算了各土壤类型和各土地利用类型的构成组分多样性指数以及多网格尺度下的空间分布多样性指数,并提出一种用于评价土壤和土地利用相互关系的关联系数,求算了5 km网格尺度下南京市典型土种单元同9种土地利用类型之间的关联系数。研究结果表明,1986年至2003年这十余年间,南京市土地利用的构成组分变化明显,其中1986年的构成组分多样性为0.361,2003年为0.444。2003年南京市土地利用的空间分布离散性更高,5种主要土地利用类型的空间分布多样性均有明显增加。南京市典型土种与各土地利用类型关联系数的计算结果表明,多组关联系数的变化趋势相同,由此推断相比于1986年,2003年南京市土壤与土地利用之间的相互联系更为复杂多变。     

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,     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

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.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

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,     

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,     

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.