基于Markov模型的长沙市和泉州市土地利用变化预测及对比研究

为探索中国中部地区和东部沿海地区典型代表城市的土地利用程度变化特征和未来演变趋势,采用地理比较分析方法,基于地理信息技术（GIS）、遥感技术和Markov模型对长沙市和泉州市未来土地利用进行模拟预测,结合土地利用程度指数分析1990—2020年期间土地利用的变化情况及其变化趋势异同,试揭示不同时期、不同区域内土地利用程度变化差异性。研究结果表明:1995—2020年期间,长沙市数量结构变化较泉州市更为稳定,耕地和建设用地所占比例结构变化具有较大差异性;土地利用程度指数的对比研究表明,两市综合程度指数均呈现一定增长,且泉州市土地利用综合程度指数变化趋势较长沙市更为显著,其土地利用程度变化量和变化率均大于长沙市。研究结果可为两市区域土地利用规划提供参考,并将有利于我国东南沿海和中部城市土地利用的可持续发展和生态环境保护。     

疏勒河中下游近35年土地利用与景观格局动态

以疏勒河流域中下游为研究区域,利用1975年Landsat MSS、2000年和2010年的Landsat TM 3期遥感影像,运用土地利用变化幅度、动态度、转移矩阵等方法,并结合景观指数,采用主成分分析方法,分析了流域1975—2010年间的土地利用/覆被和景观格局的变化及其驱动力。结果表明:近35年,研究区耕地和城乡建设用地所占比例持续上升,建设用地的动态度最高,达2.11%,耕地次之。土地利用类型间主要转移方向为:戈壁石砾地和草地转化为耕地,戈壁石砾地转为建设用地和草地。整个景观的斑块密度增大,最大斑块指数减小,景观趋于破碎化,景观的多样性增加。人口增长和经济发展因素是研究区土地利用/覆被变化的最直接驱动力。     

快速经济发展下环泉州湾地区城市建设用地扩张研究——以福建省泉州市中心城区为例

为定量化探索环泉州湾地区不同时期城市化格局演变,以LandsatTM/ETM遥感影像为数据源,从建设用地扩展速度、扩展强度、时空分布特征、建设用地转移、扩展驱动力等5个方面分析了泉州市中心城区1995-2010年建设用地的变化情况,并结合自然环境和社会经济数据分析其建设用地变化的自然和人文驱动力。研究结果表明:(1)泉州市中心城区建设用地主要集中分布于原泉州城区、惠安县和晋江市,并呈现出以泉州湾为中心,沿着晋江、洛阳江为发展轴线,环湾、向湾扩展的空间动态格局(2)1995-2010年期间泉州市中心城区建设用地呈现逐年增长的趋势,其扩展速度主要分为1995-2005年的较高速发展阶段和2005-2010年的较低速发展阶段(3)1995-2010年间新增建设用地的最大来源为耕地,次要来源为园地和林地(4)自然因素和社会因素共同驱动着泉州市中心城区建设用地的扩展,地形、人口和经济增长、政策是其主要的驱动力因素。     

近20年厦门市土地利用动态变化及预测

基于RS与GIS技术,提取1994,2000,2006和2013年4期遥感影像土地利用信息,利用土地利用转移矩阵、动态度模型、概率转移矩阵及马尔可夫模型,研究了近20 a厦门市土地利用动态变化特征,并预测其未来10 a的土地利用变化趋势。结果表明,近20 a厦门市土地利用变化速度前期较快,后期趋缓,变化面积高达46.75%;土地利用变化的总体特征与建设海峡西岸经济区龙头及加强海洋经济的城市发展战略相符;建设用地变化仍为该区域未来10 a土地利用变化的主导类型,需加强对耕地和林地的保护以促进土地利用可持续性发展。     

广西海岸带土地利用时空格局及其驱动因子

明确广西海岸带土地动态变化趋势及其驱动因子,为优化该区土地利用结构和制定合理管控政策提供参考是全面、系统、合理地利用海岸带资源,进行生态文明建设的重要依据。基于多时相遥感数据,辅以随机森林分类、转移矩阵、景观格局指数和地理探测器等方法,系统分析了2010—2018年快速发展时期广西海岸带土地利用类型时空格演变规律与景观格局,并综合探讨了其演变的驱动因子。结果表明:(1)2010—2018年广西海岸带土地利用交错增减,变化显著。建设用地、林草地、人工湿地和自然湿地面积增加,建设用地年均增加101.89 km²,集聚特征突出,主要转入源为耕地; 耕地、其他用地和水体面积缩减,耕地年均缩减162.66 km²,分散特征明显,主要转出为林草地。(2)分时段土地利用动态度差异较大。2010—2014年其他用地和2010—2018年建设用地单一动态度最大,分别为-10.48%,8.80%; 2010—2018年水体单一动态度最小(-0.11%); 综合动态度逐段上升,2010—2018年达1.52%,属快速变化型; 林草地、耕地和建设用地间交替转化活跃。(3)土地利用景观格局呈斑块破碎化、多样化和均匀化演变趋势,景观的异质性和复杂性增强。(4)人文因子是土地利用变化的主导因子,平均贡献率为17.82%; 自然因子影响较小,平均贡献率仅9.72%。人文因子和自然因子协同作用加速了广西海岸带土地利用及景观格局变化。     

山东沿海地区土地利用和景观格局变化

为分析和预测山东省沿海区域土地利用和景观格局变化,该文将景观格局指数作为评价土地利用变化模拟模型的基本指标;基于RS和GIS技术分析2000-2010年土地利用和景观格局的变化特征,并尝试CA-Markov模型预测土地利用变化,发现其在景观格局预测方面的不足,因而探索和提出Spatial-Markov模型,该模型不仅适合于土地利用变化模拟,也适合于景观格局过程分析。具体包括:1)基于2000、2005和2010年的Landsat影像进行土地利用分类,分析10a间土地利用和景观格局的变化特征,表明:耕地面积不断减少,城镇和农村居民点用地不断扩张而占用大量耕地,草地等又不断开垦为耕地;区域景观格局破碎化趋势显著,人为干扰加剧,各种景观类型的分布向均匀化发展;2)基于Logistic-CA-Markov模型,以11个变量、2000和2005年土地利用分类图为基础,模拟的2010年土地利用图与观测值相比较,虽然得到的Kappa系数较高(0.8530),但难以支持对景观格局特征的预测和分析;3)提出Spatial-Markov模型,基于2000和2005年土地利用分类图模拟2010年土地利用,模拟结果的Kappa系数高达0.8872,且景观格局指数也与观测值非常接近,因此,选择该模型预测2015和2020年的土地利用和景观格局;4)预测结果表明,2010-2020年间耕地面积将继续减少,城镇、农村居民点将继续保持快速增长的态势;景观尺度除了分形维数,其他指数保持2000-2010年间的变化趋势,而在类型尺度,除水域和未利用地外,各种景观类型多个景观指数将总体保持原有的变化趋势。该研究可为山东沿海区域土地利用规划提供参考,并为土地利用预测研究提供了一种新的方法。     

1985～2015年淮北市土地利用变化特征及其预测研究

以1985、1995、2005、2015年4期遥感影像为基础,应用RS、GIS技术和景观生态学方法,分析了淮北市1985～2015年土地利用景观格局变化,并采用ANN-CA模型预测2025年淮北市土地利用数据。结果表明:1)淮北市土地利用类型以耕地为主,耕地面积占60%以上,建设用地次之;近30年,建设用地和林地面积呈增加趋势,耕地、水域和草地呈减小趋势;2005～2015年土地利用结构和景观格局变化显著,各类土地利用面积变化速率加快。2)1985～2015年土地利用类型的转移主要为耕地向建设用地转变、水域向耕地和建设用地转变。3)1985～2015年淮北市土地利用破碎化程度不断升高,景观格局趋向复杂化,景观异质性增强。4)2015～2025年,林地面积将保持不变,耕地、草地、水域面积减少,建设用地面积不断增加。     

2003—2018年瑞兴于地区土地利用景观格局时空演变及驱动因素

为了解近15年来瑞兴于地区土地利用景观格局时空变化特征及其驱动因素,基于4期遥感影像,结合RS和GIS技术,运用土地利用动态度、土地利用转移矩阵、景观格局指数等分析了瑞兴于地区土地利用、景观格局时空演变特征,选取11项社会经济因素进行主成分分析并结合相关统计信息及政策法规分析其驱动因素。结果表明:林地是瑞兴于地区最主要的土地利用类型,约占研究区域总面积的70%,2003—2018年建设用地呈持续增加趋势,而耕地则呈持续减少趋势,草地和水域处于波动状态; 类型转换以林地与草地、草地与耕地、耕地与建设用地之间的相互转换为主,耕地是建设用地最主要的转入源; 研究区内景观破碎化程度降低,优势性提高,整体多样性及均衡性略有提高,研究区内景观类型区域均衡化、多样化发展。瑞兴于地区土地利用景观格局变化在一定程度上受到地形地貌因素的影响,主要驱动因素为经济发展、人口增加、产业结构调整以及相关政策法规的实施。     

关中-天水经济区土地利用/覆被变化与景观格局

以1980年和2005年的TM影像为数据源,应用ArcGIS,Erdas软件对影像解译,把关中-天水经济区(简称“关天经济区”)的土地利用景观分为6大类景观类型.基于ArcGIS分析模块,分析了关天经济区土地利用/覆被变化过程,并使用景观软件Fragstats分别从景观级别和景观类型级别上计算了相应的景观指数,得出以下结论:(1) 25 a间耕地和未利用地面积减少,林地、草地、水体和建筑用地面积增加,大量的耕地转变为林地、草地、建筑用地.同时较多草地开垦为耕地,但小于耕地向其转化的量.而建设用地属于转入型用地,转出量几乎为0.(2)关天经济区土地利用景观的蔓延度、优势度指数减少,香农多样性指数、香农均匀度指数增加.(3)耕地是关天经济区的优势景观类型,建设用地景观斑块正在向规模化扩张.研究结果为合理制定该区域可持续发展的土地利用政策及规划提供科学的参考及依据.     

京郊西北地区农地利用与景观格局时空特征

运用遥感与地理信息系统技术,对三年Landsat 1M多光谱遥感图像(1989年、1996年、2005年)进行解译判读,获取京郊西北地区各土地利用类型数据.运用土地利用程度时空演变模型、土地利用动态度模型、土地利用重心模型和景观生态学方法,对研究区1989～2005年间农用地利用及景观格局变化进行了分析.结果表明:农用地频繁流转,以耕地流失最为显著,去向主要为城市及建设用地,林地面积增加缓慢,沙荒地向林地转移明显:农用地各类型的新增速率远小于同期的转移速率,而城市及建设用地则相反;1989～1996年间研究区的综合土地利用动态变化率较1996～2005年间的大,变化集中表现在西北城郊过渡区域,城镇用地扩张导致耕地的利用重心不断向西偏南方向转移;研究区农用地景观破碎化程度在增加,各景观类型的平均斑块形状趋于分散和简单,景观多样性、景观均匀度旱现增加趋势,而景观优势度存逐渐减小.以利用农业用地为鲜明特征的城市化过程是影响北京西北地区景观格局演变的直接因素,城市及建设用地的不断扩张使得林地、耕地斑块的平均面积逐渐变小,景观格局连通性降低.     

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.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

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.     

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.