三位一体视角下三峡库区耕地资源内外转换轨迹和特征——以江津区为例

耕地资源约束趋紧下,区域发展和多维消费需求取决于耕地数量、质量、生态“三位一体”保护,揭示变化耕地的转换轨迹及“数、质、生”特征是确保耕地得到有效三位保护的前提,也是未来耕地保护的施策重点。基于2009—2018年土地利用数据和耕地质量等级评价成果,采用土地利用转换矩阵和景观生态风险指数等方法,从耕地内部和外部变化两个方向切入,找出不同时段耕地内外转换的轨迹,解析转换水旱地的“三位”特征,探究了转换耕地的时空变化规律。结果表明：(1)耕地转换以外部转换为主,2009—2012年、2012—2015年、2015—2018年3个阶段均有发生,主要转换类型为耕地与城乡建设用地间的互转,内部转换仅发生在2015—2018年,旱地转水田和水田转旱地数量基本相当。(2)转换耕地质量总体偏高,其中转出旱地主要在10—11等,转出水田主要在8等,而转入旱地以8—12等为主,转入水田以8—9等为主。(3)转换耕地主要分布在低和较高生态风险区,其中旱地转出转入与水田转出均主要发生在低生态风险区,而水田转入主要发生在较高生态风险区。由此可见近10年来耕地转换轨迹从单一外部转换向内外部多元地类转换,同时水田与...     

东北地区土地利用转换及其生态效应分析

基于1990、1995、2000年3期Landsat TM影像数据,在遥感与GIS支持下分析了东北地区1990～2000年土地利用转换特征与格局,以及耕地内部水田与旱地转换态势和成因。研究表明：农业土地利用内部及其非农化转换趋势明显。耕地、草地年均减少4.99×10⁴和1.40×10⁴ hm²,水域、林地、建设用地年均增加2.39×10⁴、1.93×10⁴和1.44×10⁴ hm²;不同时期的土地利用类型转换差异较大,以1990～1995年间变化为主,耕地、林地和建设用地变化量分别占总变化量的93.5%、85.8%和75.8%。耕地内部水田和旱地的转换频繁,主要是政策调控和市场调节综合作用下实施农田改造工程的结果。退耕还林草与林草地开垦的逆向发展,以及水田与旱地频繁的转换过程,已带来土地退化、水资源浪费和环境恶化等严重负面效应。     

陕北水蚀风蚀交错带土地利用变化及生态效应

 在GIS技术支持下,分析陕北水蚀风蚀交错带1986—1997年土地利用时空变化,并运用马尔可夫模型对未来土地利用进行预测。采用生态弹性度,进行土地利用变化与生态效应研究。结果表明:区域1986—1997年土地利用类型变化主要是水田、旱地、其他林地、高覆盖草地、水体和建设用地增加,其他呈现减少趋势。土地利用的年均动态变化指数为2.4%,土地利用动态变化幅度远远高于绝对值变化量,土地利用类型内部转换非常剧烈。除水田、高覆盖草地和其他草地外的土地利用类型垂直重心下降。生态弹性度整体呈现下降趋势,但降解幅度减小。     

1980－2005年太湖地区土地利用变化及驱动因素分析

为了定量化研究土地利用变化特征及其驱动因素,该文应用遥感和GIS技术,分析江苏省环太湖地区1980-1990年、1990-2000年、2000-2005年3个不同时段土地利用的数量变化特征及土地利用类型的空间转换特征,并对研究区各时段土地利用变化的驱动因素进行探讨。结果表明:25a江苏省环太湖地区土地利用类型发生了复杂变化,3个不同时段土地利用变化特征各不相同且具有明显的区域差异性;区域土地利用程度持续增加,土地利用仍处于发展期;从土地利用类型转移变化看,建设用地转入的速度远大于转出的速度,有规模增加的趋势,而水田、旱地、林地的转入速度小于转出速度,存在规模减少的趋势。人口数量的增加、工业化、城市化带来的经济发展与土地管理政策等人类活动是江苏省环太湖地区土地利用类型转换的主要驱动因素。尽管近年来江苏省环太湖地区的土地开发利用取得了巨大的经济收益,但部分人类经济活动给区域农业的发展及土地资源的可持续利用带来巨大压力,甚至导致以水田为主的区域耕地资源质量的进一步退化。该研究为江苏省环太湖地区土地资源的可持续利用及人-地关系的协调发展提供科学依据。     

艾比湖流域近40年来土地利用与覆被动态变化研究

土地利用与覆被变化(LUCC)是全球环境变化的研究焦点,定量评估土地利用变化对区域土地资源可持续利用具有重要意义。选择干旱区典型代表区域———新疆自治区艾比湖流域为研究区,基于1970年和2009年2期的LUCC数据,利用数学模型和ArcGIS分析了艾比湖流域1970—2009年近40 a来土地利用与覆被的变化过程。结果表明,在整个研究时段内耕地和城乡建设用地面积在不断增加,其中耕地面积的年平均变化率为5.21%,城乡建设用地为5.62%,其它土地利用类型的面积均减少;耕地和草地、未利用地与草地之间的转化比较明显;城乡建设用地的动态变化最大,水域的动态变化最小;转入贡献率中占优势的主要是未利用地、草地和耕地,转出贡献率占优势的主要是未利用地和草地。     

克里雅河流域1990-2010年土地利用/覆被变化及其生态环境状况评价

通过GIS技术,以及1990年、2000年、2010年克里雅河流域Landsat-TM影像数据和中巴资源卫星数据,分析了克里雅河流域近20a土地利用/覆被变化并对其生态环境状况进行评价,结果显示:(1)克里雅河1990—2010年的20a里各土地利用类型变化显著,其中耕地、水域湿地、建设用地和林地呈不断增加趋势,变化幅度分别为29.62%,16.64%,11.28%,2.9%。草地、沙地和未利用地面积不断减少,变化幅度为-3.65%,-0.6%,-0.33%;(2)1990—2010年流域新增耕地主要由3.11%的草地、0.3%的沙地和0.35%的未利用地转移而来,新增水域湿地主要由0.15%的沙地和0.29%的草地转移而来,新增建设用地主要由0.02%的沙地和0.15%的耕地转移而来,新增林地则主要由0.18%的沙地和0.03%的草地转移而来;(3)对流域生态环境状况进行评价可知在近20a里克里雅河流域生态环境状况无明显变化,但是流域耕地面积的不断扩张对流域生态环境良性发展产生一定隐患,因此合理利用流域水土资源对流域生态环境安全十分重要。     

滇池流域土地利用动态变化及对流域水环境的影响分析

以滇池流域为研究对象,以1974年、1988年、1998年、2008年四个时期的TM遥感影像为数据基础,结合图像处理、地理信息系统及计量软件,应用马尔柯夫模型对研究区土地利用动态变化及变化趋势进行了分析,同时研究了该区域土地利用变化对水环境的影响。结果表明:①滇池流域近30a来土地利用状况发生了明显的变化,其中耕地、建设用地和其它地类的变化幅度较大,水域和林地变化不明显。②马尔柯夫链预测结果表明:2015—2030年研究区内建设用地面积进一步增加,林地、水域和其它地类进一步减少,但减少的幅度在逐渐变小,耕地面积也继续减少。③滇池流域的水质明显受到土地利用类型及利用变化情况的影响:在5%显著性水平下TP和BOD与土地利用类型之间存在相关关系,建设用地对总氮量的弹性为15.31,耕地对总氮量弹性为10.47,牧草地对总氮量弹性为-156.74。建设用地对BOD的影响为543.79,耕地对BOD影响为-272.49,林地对BOD影响为160.88;在20%显著性水平下COD与土地利用类型之间存在相关关系,建设用地、耕地和湿地对COD的弹性分别为173.88,-100.75,-4 920.59。④马尔柯夫链预测结果表明,随着年份的增长,水质污染状况指标呈现持续恶化的趋势。     

基于分维模型的台兰河流域土地利用变化研究

以新疆台兰河流域1990年、2000年和2005年土地利用数据为例,将分形理论应用于土地利用空间分布及其变化的研究中,定量分析干旱内陆河流域土地利用空间结构复杂性、稳定性以及各土地利用类型随时间的变化趋势,从而阐述不同土地利用类型的空间分布规律。结果表明:各种土地利用类型都具有空间分形特征,分维数是面积、斑块数量和平均斑块面积等单项指标有机结合的综合表现,是综合表征土地利用变化空间格局的定量指标。1990年、2000年和2005年不同土地利用分维数的排序分别为:水域工矿居民用地耕地草地未利用地林地;水域工矿居民用地草地耕地林地未利用地;水域工矿居民用地草地林地耕地未利用地。1990年、2000年和2005年台兰河流域整体土地利用分形维值分别为1.5993,1.5986,1.6079,流域土地利用的分维数呈现先减后增的趋势,土地利用空间结构趋于复杂化,土地利用类型有扩张的趋势。1990年、2000年和2005年台兰河流域整体空间结构稳定性指数分别为0.1720,0.1563,0.1435,说明整个流域土地利用类型的空间结构稳定性逐渐下降。     

基于地学信息图谱的江汉平原土地利用时空变化分析

为分析江汉平原土地利用时空变化特征,探索土地利用变化原因、过程并预测未来变化趋势,基于江汉平原1990年、2000年和2010年土地利用空间数据,运用地学信息图谱方法,构建两个时序的土地利用变化图谱、涨落势图谱和变化模式图谱,分析了江汉平原1990—2010年土地利用的时空变化规律和发展过程。结果表明:(1) 1990—2010年耕地和水域是主要土地利用类型,耕地持续减少,水域和建设用地持续增加;(2)变化图谱以耕地与水域、建设用地间的互相转换为主。耕地与水域间的互相转化集中于低湖平原区;耕地转化为建设用地贯穿整个研究时段,主要是经济相对发达的城区周边区域;而建设用地转化为耕地发生在后期,集中在石首市和松滋市等地;(3)落势图谱中萎缩耕地面积最大,占68.63%;增势图谱中新增水域面积最大,占46.39%。各县市存在明显差异;(4)变化模式图谱中全期稳定型占据主要地位,其次是后期变化型。研究表明江汉平原土地利用变化呈现土地利用类型"典型化"、土地动态变化"差异化"和土地变化模式"稳定化"的特征。     

基于地形因子的鄱阳湖地区土地利用格局变化分析

为研究土地利用空间格局变化地形特征,采用1990年、2000年、2010年、2013年4期鄱阳湖地区Landsat TM解译数据及DEM数据,借助地形位、分布指数、地学信息图谱方法,深入探讨了1990—2013年鄱阳湖地区不同地形下土地利用格局的变化特征。结果表明:(1)1990—2013年,鄱阳湖地区土地利用类型以耕地、林地、水域为主,三种类型面积占比均在90%以上,建设用地快速增长,由1990年的1 387.42km~2增加到2013年的2 413.98km~2,增加了1 026.56km~2,耕地、未利用土地、林地面积分别减少513.39km~2,399.04km2,123.75km~2;(2)1990—2013年,土地利用格局变化具有地形效应,低地形范围优势分布耕地、建设用地、水域,高地形范围林地优势分布,未利用土地、草地零散分布对地形变化适宜性较强;(3)1990—2013年,研究区土地利图谱以稳定型和中期型为主,面积分别为48 457.44km~2,2 014.56km~2,稳定型图谱的优势区域位于高、低地形范围,耕地、林地、建设用地变化稳定;低、中高地形范围是中期变换型的优势分布区,主要表现为未利用土地—未利用土地—水域—水域、耕地—耕地—建设用地—建设用地。     

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.     

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.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.     

Genetic similarities among Spanisch populations of Agropyron, Elymus and Thinopyrum, using PCR-based markers

Arbitrary oligonucleotides were used as primers to amplifygenomic DNA of 48 wild Spanish populations of Agropyroncristatum, Elymus hispanicus,E. caninus,E. repens,Thinopyrum curvifolium, Th.junceum and Th.intermedium. Genetic diversity was analysedusing nineteen primers. The number of amplified products ranged from8 to 18 per primer and a total of 240 markers were scored. Differentlevels of intraspecific genetic diversity were found, the allogamousspecies E. repens andTh. intermedium being themost variable. Jaccard's similarity coefficients for internalmeasure within and between populations were used to produce a clusterdiagram. The results demonstrate differences in the degree ofsimilarity between taxonomic units. Interpopulational variability andinterspecific genomic relationships of these species arediscussed.     

Mycorrhizae,biocides, and biocontrol. 4. Response of a mixed culture of arbuscular mycorrhizal fungi and host plant to three fungicides

The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg^-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants.