有机无机肥配施提高旱地麦田土壤养分有效性及酶活性

【目的】有机无机肥配施可显著提高土壤微生物活性,改善土壤养分供应状况。深入理解不同氮肥用量配施有机肥下土壤的生物化学性状,为充分发挥肥料效益,实现冬小麦高产稳产提供科学施肥依据。【方法】以冬小麦为供试作物,在黄土高原南部半湿润易旱区连续三年进行了田间定位试验。采用裂区试验,设置5个氮肥用量 (N 0、75、150、225、300 kg/hm2),配施或不施有机肥 (30 t/hm2)。在冬小麦拔节期、抽穗期、灌浆期、成熟期,取0—20 cm土层样品,采用常规方法测定土壤养分和酶活性。在收获期,调查了冬小麦籽粒产量。【结果】1) 冬小麦产量以施氮量N 150 kg/hm2配施有机肥处理最高,且有机无机肥配施与单施化肥处理相比能够在减少19.1%的氮肥用量条件下,保证冬小麦产量稳产高产,此外在天气不理想的状况下,冬小麦的净收益也能保持在较高水平。2)在冬小麦的整个生育期,有机无机肥配施处理可显著提高0—20 cm土层土壤有机质、全氮、有效磷、速效钾、硝态氮含量以及土壤蔗糖酶、碱性磷酸酶和脲酶活性,与单施化肥处理相比分别增加18.2%、27.4%、149.3%、31.4%、27.6%、4.0%、4.7%、1.5%,但对过氧化氢酶活性无明显促进作用,且除了脲酶以施氮量N 300 kg/hm2配施有机肥的活性最高,其余指标均以施氮量N 150 kg/hm2配施有机肥处理效果最佳。3) 施氮量、有机肥、冬小麦生育期显著影响土壤蔗糖酶、碱性磷酸酶、过氧化氢酶和脲酶活性,施氮量和有机肥的交互效应显著影响碱性磷酸酶活性,施氮量和冬小麦生育期的交互效应显著影响土壤蔗糖酶、碱性磷酸酶和过氧化氢酶活性,有机肥和冬小麦生育期的交互效应显著影响土壤碱性磷酸酶和过氧化氢酶活性,施氮量、有机肥和冬小麦生育期三者的交互效应显著影响土壤蔗糖酶活性。4) 相关分析表明,土壤碱性磷酸酶与有机质间、脲酶与速效钾之间均未达显著相关水平,土壤蔗糖酶、碱性磷酸酶、过氧化氢酶和脲酶与有机质、全氮、有效磷、速效钾均呈显著或极显著正相关。【结论】土壤养分、酶活性和冬小麦产量之间密切相关,在施用有机肥30 t/hm2的基础上配施氮肥N 150 kg/hm2,有利于增强黄土高原南部半湿润易旱区冬小麦土壤生态系统的可持续性。     

长期施肥对棕壤氧化还原酶活性和动力学特征的影响

土壤质量与土壤的生物学性质密切相关,施肥制度对土壤生物学特性的影响研究对土壤质量管理具有重要的意义。本文以沈阳农业大学长期肥料定位试验为基地,研究长期不同施肥制度对土壤理化性质,过氧化氢酶、脱氢酶活性和动力学特征的影响。主要研究结果:施用化肥、有机肥配施化肥降低土壤pH值,提高4种土壤全量养分(全C、全P、全S、全N)含量,有机肥配施化肥提高土壤速效N含量;低量化肥配施有机肥显著提高土壤过氧化氢酶活性及Vmax/Km值和Vmax值,低量化肥配施有机肥显著提高脱氢酶活性及Vmax/Km值,降低脱氢酶Km值。本文的研究表明,合理的化肥施用量及配施有机肥是提高土壤生物学活性的有效手段。     

不同生物有机肥用量对土壤活性有机质和酶活性的影响

通过盆栽试验研究了不同有机质含量的土壤中,不同用量生物有机肥对棉花苗期土壤活性有机质和5种酶活性的影响。结果表明,不同土壤随着生物有机肥施用量的增加,其活性有机质及碳库管理指数(CMI)均显著增加。其中高有机质含量土壤施用生物有机肥20 g/kg效果显著,中等有机质含量土壤和低有机质含量土壤施用生物有机肥30、40 g/kg效果显著。5种土壤酶活性施肥处理均高于对照(CK),并且土壤酶活性与施用量成正比。脲酶、蔗糖酶、多酚氧化酶在施用生物有机肥10、20 g/kg与其它处理相比变化显著,过氧化氢酶、蛋白酶变化不显著。相关分析表明,有机质与活性有机质和CMI在棉花出苗0 d相关系数分别为0.831**、0.542*;在出苗后60 d相关系数分别为0.928**、0.635**,其中有机质与活性有机质相关性最高。而CMI与有机质和活性有机质在棉花出苗0 d相关系数分别为0.542*、0.896**,在出苗后60 d分别为0.635**、0.842**,说明活性有机质相对于有机质与CMI关系更为密切。蔗糖酶、过氧化氢酶、多酚氧化酶与土壤有机质和活性有机质在棉花出苗0 d和出苗后60 d存在显著相关,表明活性有机质与土壤酶活性能够较好的反映肥力水平。     

有机无机肥配施对旱地冬小麦产量、水肥利用效率及土壤肥力的影响

在陕西渭北旱塬,为探寻适合当地冬小麦生产的合理有机无机肥配施比例,通过田间试验研究不同氮肥用量(0kg/hm2,75kg/hm2,150kg/hm2,225kg/hm2和300kg/hm2)与有机肥(30t/hm2猪粪)配施对冬小麦产量、氮肥利用效率、水分利用效率及土壤养分的影响。结果表明,有机无机肥配施能提升冬小麦产量,3a冬小麦产量最高值均出现在M+N225处理,比对照分别增产23.1%,49.7%和23.0%,比相同氮肥用量下的单施无机肥处理分别提升1.2%,12.7%,3.5%。经过3a连续种植,有机无机肥配施处理有土壤有机质、全氮、有效磷、速效钾分别比试验前提升18.8%,22.2%,282.1%和15.1%。合理的有机无机肥配施比例能显著提升冬小麦水分和氮肥利用效率,但过量氮肥与有机肥配施会造成冬小麦减产,水分和氮肥利用效率显著降低,而且残留在土壤中的硝态氮含量显著增加。综上所述,在渭北旱塬地区小麦生产中,应在施用有机肥30t/hm2(折合纯氮240kg/hm2)的基础上配施75~150kg/hm2的氮肥。     

黄土高原旱地小麦施肥对产量及水肥利用效率的影响

在长期定位试验的基础上,研究了黄土高原旱地不同施肥对小麦产量、土壤养分和水分的变化及其利用效率的影响。结果表明,单施有机肥(M)增产效果较好,产量达5265.0 kg/hm2;有机肥和化肥配施(NPM)小麦产量最高,达5898.8 kg/hm2。NPM配施小麦总吸氮量最大,比单施氮肥(N)增加了131.4 kg/hm2;NPM配施的氮肥利用率、氮肥偏生产力、氮肥农学效率、氮肥生理利用率分别为67.0%、49.16 kg/kg、36.97 kg/kg、73.11kg/kg;在不同施肥体系中其变化趋势基本一致,均为:NNPNMNPM,处理间差异显著。土壤养分含量变化看出,单施氮肥土壤全氮、碱解氮与不施肥(CK)的差异不显著;有机肥可显著提高土壤速效钾的含量;NPM配施土壤耗水量最大为558.3 mm,水分利用率最高为31.5 kg/(hm2.mm),随着耗水量增加的同时,土壤出现干燥化趋势。     

适量有机肥与氮肥配施方可提高河西绿洲土壤肥力及作物生产效益

【目的】 河西绿洲灌溉农业区是我国主要的商品粮生产及玉米制种基地,结合当地耕作制度进行土壤有效培肥是提高农业生产效益和可持续发展的基础。本研究以河西灌漠土长期定位试验为依托,探讨了长期施用一种或者多种有机肥以及有机无机肥配合对土壤养分、土壤酶活性及产量的影响,为筛选出适于当地农业可持续发展的施肥模式提供理论依据。 【方法】 试验采用随机区组排列,除对照外,在施磷肥 (P₂O₅) 150 kg/hm2 的基础上,再设 12 个处理:单施用农家肥 120 t/hm2 (M);单施绿肥 45 t/hm2 (G);单施秸秆 10.5 t/hm2 (S);单施氮肥 375 kg/hm2 (N);农家肥 60 t/hm2 + 绿肥 22.5 t/hm2 (1/2MG);农家肥 60 t/hm2 + 秸秆 5.25 t/hm2 (1/2MS);农家肥 60 t/hm2 + 氮肥 187.5 kg/hm2 (1/2MN);绿肥 22.5 t/hm2 + 氮肥 187.5 kg/hm2 (1/2GN);秸秆 60 t/hm2 + 氮肥 187.5 kg/hm2 (1/2SN);农家肥 40 t/hm2 + 绿肥 15 t/hm2 + 氮肥 124.5 kg/hm2 (1/3MGN);农家肥 40 t/hm2 + 秸秆 3495 kg/hm2 + 氮肥 124.5 kg/hm2 (1/3MSN);农家肥 30 t/hm2 + 秸秆 2625 kg/hm2 + 绿肥 11.25 t/hm2 + 氮肥 94.5 kg/hm2 (1/4MGSN)。调查了耕层土壤有机质和速效养分含量变化以及几种主要土壤酶活力,采用主成分分析、聚类分析、经济效益分析综合比较了不同施肥方式对土壤质量与经济收益的影响。 【结果】 长期不施肥、单施氮肥(N)、氮肥配施绿肥或者秸秆均会造成土壤钾素匮缺,较 1988 年初测土土壤速效钾含量分别下降了 16.59%、39.37%、25.04%、23.31%;M、G、S 三种有机肥单施或与氮配施均能提高土壤碱解氮、土壤有效磷、土壤有效钾、土壤有机质(SOM)含量,不同施肥方式下,其含量大小总体表现为高量有机肥 > 减量有机肥 + 减量 N > N > CK;M、G、S、N 单施或 1/2MN、1/2GN、1/2SN 处理均能提高蔗糖酶、磷酸酶、脲酶、过氧化氢酶活性,以 G、1/2GN 处理对提高土壤蔗糖酶、脲酶的活性的效果最显著,M、G、MN、GN 处理对提高碱性磷酸酶活性的效果最显著;主成分得分进行聚类分析,不同处理培肥土壤质量效果由高到低分成四类,分别为一类高量有机肥 M、G、1/2MG > 二种有机肥与氮肥减量配施 1/2MN、1/3MSN、1/3MGN、1/2GN、1/2MS、1/4MSGN > 三类氮肥、秸秆、秸秆与氮肥 N、1/2SN、S > 四类不施肥(CK);各施肥方式均能提高作物产量,与不施肥(CK)相比,增产幅度为 12.21%～235.4%,肥料贡献率在 10.89%～70.18% 之间,单施肥增产总趋势为 N > G > M > S,减量配施肥增产总趋势为 1/2GN > 1/2MN>1/2MS,施肥方式以有机肥配施 N 对产量贡献最大;经济效益分析表明施 N 或有机肥与 N 配施对于提高净收益作用较大。 【结论】 通过主成分分析与聚类分析、经济效益与产量综合比较,农家肥、绿肥和秸秆长期单施成本高,产量和经济效益低,维持土壤养分和产量需要的用量大。因此,提倡适量有机肥与氮肥配施,达到提高作物产量,增加经济效益,保证土壤肥力可持续发展。      

施氮水平对不同肥力土壤微生物学特性的影响

为阐明不同肥力区域,施氮水平对土壤微生物学特性的影响,采用室内分析法系统比较3个肥力条件下,5个施氮水平(不施氮、70%×优化施氮、优化施氮、130%×优化施氮和农民习惯性施氮)对土壤微生物生物量碳、氮以及酶活性的影响。结果表明:较高肥力有利于微生物生物量氮(MBN)的保蓄。随氮肥施用水平提高,微生物所同化的氮在各肥力区均有所增加,继续增大尿素用量(312kg/hm2),中、低肥力土壤MBN的数值有所回落;而肥力差异未对微生物生物量碳(MBC)产生规律性的影响。低肥力条件下,施氮对MBC的影响表现为先抑制后促进的作用,高、中肥力则与之相反;优化施氮与农民习惯性施氮均有助于蔗糖酶和脲酶活性的提高;在高、低肥力区域,随施氮水平增加,过氧化氢酶活性先降低而后升高,与在中等肥力区所表现的规律恰好相反。与无氮对照(N0)相比,70%优化施氮对土壤蛋白酶活性有抑制作用,而随氮肥用量增加,蛋白酶活性渐趋升高,尿素用量为312kg/hm2时的蛋白酶活性达最大值;适量施氮范围内(0~270kg/hm2),增施尿素有利于碱性磷酸酶活性的提升。     

氮肥与有机肥配施协调土壤固定态铵与可溶性氮的研究

【目的】 土壤固定态铵是肥料氮的一个“临时贮藏库”,可逐渐释放以供作物利用,土壤可溶氮则是土壤固定态铵的重要来源,因此研究设施条件下氮肥与有机肥配施对土壤固定态铵和可溶性氮含量的动态变化以及相互关系的影响,对于设施生产中安全高效的施肥管理有着重要意义。 【方法】 以番茄为试材,温室内连续两年进行田间小区试验,设不施肥(CK)、施N量0、187.5、375. 562.5 kg/hm2 (N0、N1、N2、N3)、单施有机肥(M,75000 kg/hm2)以及有机肥与氮肥配施处理(MN0、MN1、MN2、MN3)。分析了土壤固定态铵和可溶性氮(土壤矿质氮和可溶性有机氮)含量动态变化。 【结果】 施肥显著提高了0-30 cm土层土壤固定态铵和可溶性氮的含量(P < 0.01);各施肥处理均以第1穗果膨大期时含量最高。总体来看,不施有机肥条件下,土壤固定态铵和矿质氮、可溶性有机氮的含量均以施N 375.0 kg/hm2处理为最高,而在氮肥与有机肥配施条件下,以施N 375.0 kg/hm2与有机肥75000 kg/hm2配施处理和施N 562.5 kg/hm2与有机肥75000 kg/hm2配施处理的土壤固定态铵和矿质氮、可溶性有机氮含量为最高,但未发现氮肥施用量对土壤固定态铵含量产生显著影响;除收获期20-30 cm土层外,整个生长季内土壤固定态铵和矿质氮含量之间均有显著的正相关关系(P < 0.05),部分土层土壤固定态铵与可溶性有机氮之间也有显著的正相关关系(P < 0.05)。 【结论】 设施番茄栽培条件下,土壤固定态铵和可溶性氮在土壤氮素的固持与释放方面极显著相关,施无机N 375.0 kg/hm2配合有机肥75000 kg/hm2,可较好地提高土壤中的氮的有效性,更好地协调土壤供氮能力。     

适宜的水氮处理提高稻基农田土壤酶活性和土壤微生物量碳氮

为探讨节水灌溉与氮肥施用对稻田土壤微生物特性的影响,该试验采用防雨棚池栽试验,研究2个灌溉模式（常规灌溉与控制灌溉）与3个水平施氮量（90、180和270 kg/hm2））对稻基农田土壤脲酶活性、土壤过氧化氢酶活性、土壤磷酸酶活性、土壤转化酶活性、土壤微生物量碳及土壤微生物量氮的影响。研究结果表明,随着施氮水平增加,土壤脲酶活性和土壤微生物量氮增加,土壤过氧化氢酶活性、土壤磷酸酶活性、土壤转化酶活性、土壤微生物量碳、土壤微生物量碳与土壤微生物量氮的比值、土壤微生物熵均呈先增加后降低趋势;与常规灌溉相比,控制灌溉显著提高稻基农田土壤脲酶活性、土壤过氧化氢酶活性、土壤磷酸酶活性、土壤转化酶活性、土壤中微生物量碳、土壤微生物量氮、土壤微生物熵,降低土壤微生物量碳与土壤微生物量氮的比值。在该试验条件下,以控制灌溉模式下施氮量180 kg/hm2可获得最优的生物环境,土壤脲酶活性、土壤过氧化氢酶活性、土壤磷酸酶活性、土壤转化酶活性、土壤中微生物量碳、土壤微生物量氮分别达到3.02×10-2 mg/g、0.93 mL/g、5.70 mg/g、10.08 mL/g、237.58 mg/kg、52.60 m/kg。该研究对认识稻基农田水氮耦合关系、指导江淮丘陵季节性干旱区水稻优质节水高产高效栽培实践提供理论依据。     

减氮配施微生物菌剂对水稻根系发育及土壤酶活性的影响

为探明滨海盐渍型水稻土在氮肥减施条件下,微生物菌剂促进水稻根系发育和提高土壤酶活性的作用机制,本试验通过室内盆栽试验,探讨了减氮配施微生物菌剂对水稻根系发育和土壤酶活性的影响。结果表明:(1)减氮配施微生物菌剂可增加水稻根长、根表面积、根平均直径、总根体积和根尖数,促进水稻根系生长;在施菌剂40～50天内,减氮30%配施菌剂处理较单施全量氮肥处理显著增加了根系生物量。(2)所有氮肥配施菌剂处理的土壤脲酶、蔗糖酶和过氧化氢酶活性均提高;且在施菌剂50天时减氮30%配施菌剂处理的土壤脲酶、蔗糖酶和过氧化氢酶活性明显高于其他处理,与单施全量氮肥处理相比,分别提高了22.7%、16.67%和16.35%。以上结果表明,氮肥减量配施微生物菌剂能提高滨海盐渍型水稻土酶活性,促进水稻根系生长。施用微生物菌剂能减少化肥用量,达到提高农业生态系统可持续发展的目的。     

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。     

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.     

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.     

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,     

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.