石羊河中下游不同生境柽柳群落物种多样性及土壤水分、盐分关系

为了给石羊河流域柽柳群落植被恢复与保护提供参考依据,以石羊河流域4种类生境型柽柳群落为研究对象,测定了群落物种组成、数量特征及土壤水分、盐分,分析了不同生境群落特征及其与土壤水分之间的关系。结果表明:(1)柽柳群落中共有植物22种,分属9科20属,其中灌木植物最多,为8种(5科6属),其次是多年生草本,为7种(4科7属),一年生草本为7种(3科7属),分别占总物种数的36.36%,31.82%,31.82%。(2)柽柳群落中,固定盐碱沙地密度最大,盐碱地和退耕湿地次之,丘间低地最低; 平均密度差异不显著(p>0.05); 盖度差异显著(p<0.05),以固定盐碱沙地最大,为73.33%,盐碱地和丘间低地次之,均为61.67%,退耕湿地最小,为47.00%。(3)不同生境类型柽柳群落在物种组成及多样性方面存在差异,从Margalef丰富度指数、Shanon-Wiener多样性指数、Simpson多样性指数和Alatulo均匀度指数看,丘间低地>盐碱地>固定盐碱沙地>退耕湿地(p<0.05),丘间低地群落优势度指数低于盐碱地和固定盐碱沙地、退耕湿地,群落结构相对稳定; 丘间低地Pielou均匀度指数明显高于其他3种类型。(4)在0—10 cm,10—20 cm,20—30 cm,30—40 cm,40—60 cm,60—80 cm土层范围内,盐减地和固定盐碱沙地土壤含水率最高,其次是退耕湿地和丘间低地,总体呈现出先升高然后逐渐下降的趋势。物种多样性与土壤水分均呈正相关关系,但均未达到显著水平(p<0.05),综上所述,不同生境柽柳群落组成物种稀少,结构简单,种群物种平均密度差异不显著。群落组成物种中,灌木种类最多,多年生和一年生草本种类相同。丘间低地多样性指数高于其他生境类型,退耕地最低,而生态优势度指数则相反,物种多样性与土壤水分表现出非显著的正相关关系。     

重庆市茶园蚂蚁物种多样性及空间分布格局

为筛选茶园害虫的蚂蚁类天敌,采用样地调查法研究了重庆主要产茶区(海拔371~1 068 m)茶园蚂蚁物种多样性特征与空间分布格局。在重庆主要产茶区茶园,设置3条垂直带,每条垂直带划分为低海拔(300~500 m)、中海拔(500~700 m)和高海拔(700 m以上)3个水平带,每个水平带设置3~4块样地,调查茶园的蚂蚁物种组成、群落多样性及空间分布特点。在物种多样性方面:共采集到蚁科昆虫4亚科,39种。各水平带物种丰富度为7~13种,Shannon-Wiener多样性指数0.55~1.25,Pielou均匀度指数0.08~0.16,Simpson优势度指数为0.26~0.65;各水平带蚂蚁群落多样性指数差异不显著,表明其多样性水平比较一致。群落相似性指数为0.22~0.48,多数处于中等不相似水平。在群落优势种方面:不同海拔茶园蚂蚁优势种数目1~3种,常见种最多达6种,最少仅1种;稀有种最多17种,最少5种;从重庆范围来看,重庆主要产茶区茶园蚂蚁群落共有7种优势种。在蚂蚁空间分布方面:有17种蚂蚁具有较宽的垂直空间分布,活动范围涵盖土壤、地表和树冠,有作为天敌昆虫资源的可能。仅有9种蚂蚁在不同水平带的茶园中均有分布。结合群落相似性与多样性分析结果,重庆茶园生境破碎,蚂蚁群落间物种交流受阻,不利于茶园生物多样性水平的稳定与提高。     

福建将石自然保护区鸟类物种相对多度模型的拟合研究

应用对数级数分布模型、对数正态分布模型、几何级数分布模型和分割线段模型对福建将石自然保护区鸟类物种相对多度分布格局对比研究结果表明 ,对数级数分布模型、对数正态分布模型能较好地描述将石自然保护区鸟类多样性 ,而几何级数分布模型和分割线段模型则不适于描述该自然保护区鸟类多样性 ;“多度 /频度”图解可较好地反映对数级数分布模型拟合效果 ,丘陵山地鸟类群落物种相对多度不遵从对数级数分布 ,各生境群落百分率相似性指数说明各生境群落百分率相似性较低。     

山西省中条山区鸟类群落结构分析

从中条山区自然环境条件入手，在分析鸟类区系特征的基础上，揭示了不同栖息环境中鸟类的群落组成，中条山鸟类区系属古北界，人类活动对鸟类群落组成具有显著影响，鸟类分布随垂直自然带不同而变化。     

区域景观中生境特异性对昆虫多样性的影响——以西双版纳为例

生境特异性(habitat-specific)在维持生物多样性上发挥着重要作用。本研究旨在了解在区域景观中,不同类型生境对不同类群昆虫多样性的贡献及群落结构差异,从大尺度上探讨昆虫多样性分布格局和维持机制。于2019年8—9月,在西双版纳地区利用样线调查法,调查了保护区、次生林、人工林和农田4种生境中蝴蝶、蝽和甲虫的物种数、特有物种数,分析了昆虫群落的生境特异性指数、群落结构相似性及物种丰富度与生态因子的关系。共采集昆虫2588头,其中蝴蝶94种(744头),蝽197种(1094头),甲虫129种(750头),保护区的昆虫物种数和特有物种数均高于其余类型生境。保护区昆虫群落的生境特异性指数实测值高于期望值,而其余类型生境昆虫群落的生境特异性指数实测值均低于期望值;不同类型生境间,3个类群的昆虫群落汇总的生境特异性指数不存在显著差异(F_(3,57)=2.054),甲虫生境特异性指数差异显著(F_(3,55)=3.478),蝴蝶(F_(3,38)=1.504)和蝽类(F_(3,53)=1.153)生境特异性指数差异不显著。群落结构相似性分析显示,保护区和农田的3个类群昆虫群落汇总的群落结构差异显著;次生林和人工林的蝴蝶群落结构差异显著,保护区和次生林的蝽类群落结构差异显著,甲虫昆虫群落结构差异不显著。本研究还发现,只有生境类型对昆虫群落的物种丰富度产生的影响极显著(P0.01),而其他生态因子的影响不显著。在大尺度区域景观中,保护区对昆虫群落的多样性影响最大,生境类型与昆虫群落的物种丰富度密切相关,保护较好的天然林是维持区域昆虫群落分布格局和多样性的重要机制。     

小兴安岭天然林土壤革螨的生态分布特征

对小兴安岭云冷杉林、兴安落叶松林、赤杨林、白桦林和阔叶红松林五种天然林生境土壤革螨的水平和垂直分布进行了调查研究。结果表明 ,广泛分布各生境的为峰革赛螨和小兴安岭螨 ,仅存在一种生境的种类较多 ,各生境仅存的种类越多 ,生境差异性就越明显。通过Jaccard相似性指数比较分析 ,兴安落叶松林和赤杨林生境土壤革螨群落最相似 ,云冷杉林和赤杨林生境及赤杨林和白桦林生境土壤革螨群落极不相似。土壤革螨的垂直分布总体上表现为表聚性 ,但各生境存在差异。土壤有机质和全氮含量高的土壤 ,土壤革螨的种类和数量都多。多数土壤革螨适宜在微酸性的条件下生存。     

几种沙生灌木生物量及其在不同器官分配与土壤理化特征相关性

灌木群落的生物量及其在不同器官分配与土壤理化特征之间关系复杂。以毛乌素沙地柠条锦鸡儿(Caragana korshinskii)、油蒿(Artemisia ordosica)、杨柴(Hedysarum fruticosum)灌木群落为研究对象,分析了不同灌木的生物量分配与土壤理化特征的相关性。结果表明:供试的3种灌木整株生物量与各器官生物量均为:柠条锦鸡儿>油蒿>杨柴,且达到了显著性差异(P<0.05)。3种灌木各器官生物量及分配比例为:茎>根>叶。其中,柠条锦鸡儿的生物量在茎、根、叶的分配比例分别为62%、25%、13%;油蒿的分配比例分别为53%、30%、17%;杨柴分别是55%、35%、10%。3种灌木群落土壤有机质含量均表现为随土层加深而递减的垂直变化特征。相关性分析表明,3种灌木整株生物量与土壤有机质含量呈极显著正相关性(r=0.920**,P<0.01),与土壤全氮、速效氮含量呈显著正相关性,相关系数分别为r=0.762*(P<0.05)和r=0.789*(P<0.05),而与土壤全磷和速效磷含量的关系不显著。3种灌木整株生物量及其在不同器官分配特征与荒漠生境有关,它们与干旱、半干旱环境长期相互作用产生了不同的生存策略,茎的木质化程度、叶构型、根系分布情况会影响各器官的异速生长,进而影响了生物量的分配特征。在荒漠生态系统中,灌木林生产力受群落类型和土壤养分的共同制约。     

长期施肥对黄土区连作苜蓿草地植被特征的影响

蝗虫与植被间存在复杂的耦合关系,蝗虫群落特征变化是蝗虫对植被群落重要的生态响应过程。2009年6—8月在黑河上游白大坂草原,通过野外实地调查研究了黑河上游天然草地蝗虫的种类组成、分布频度、群落多样性与植被的相关性。在海拔2 400～2 800m的7个植物群落采集到蝗虫13种,隶属于3科10属,亚洲小车蝗(Oedaleus decoratus)、李氏大足蝗(Gomphocerus licenti)和白纹雏蝗(Chorthippus al-bonemus)是优势种,分别在驴驴蒿(Artemisia dalailamae)、狼毒(Stellera chamaejasme)占优势的群落分布最多;不同植物群落中蝗虫组成、优势种差异明显,蝗虫群落多样性和优势度差异显著(p<0.05),均匀度差异不显著(p>0.05);蝗虫多样性与植被盖度、多样性呈正相关,与高度和优势度呈负相关,蝗虫群落均匀度与植物群落多样性呈负相关,蝗虫多度与植物多样性呈正相关。蝗虫分布和发生数量受蝗虫生物学特性和植物群落组成差异的影响,蝗虫对植物群落选择的多样性反映了蝗虫对生境具有较强的适应能力以及种群内部的协同作用。     

13C标记磷脂脂肪酸分析在土壤微生物生态 研究中的应用

磷脂脂肪酸(PLFA)是微生物细胞膜的重要组成成分,不同微生物群落可通过不同生化途径合成不同的PLFA,因此可选择某些PLFA作为微生物群落结构变化的生物标志物。PLFA与稳定性同位素~(13)C标记(~(13)C-PLFA)技术结合,不仅能够确定原位土壤环境中微生物群落组成,而且能够定向发掘土壤生态系统中参与碳源代谢过程的微生物群落,提供复杂群落中土壤微生物相互作用的信息,具有广阔的应用前景。其基本原理为:将富集~(13)C稳定同位素的基质加入土壤中,土壤中的某些微生物群落利用基质~(13)C合成PLFA,提取并纯化土壤微生物的PLFA,利用气相色谱-燃烧-同位素比例质谱(GC-C-IRMS)测定其~(13)C丰度,通过对比分析,从而获取微生物群落组成与其功能的直接信息。本文在介绍了~(13)C-PLFA原理的基础上,综述了该技术在光合同化碳的根际微生物利用、土壤有机质分解的激发效应、甲烷氧化、有机污染物降解、外源简单碳源和外源复杂碳源的微生物利用等方面的应用,对此项技术的优缺点进行了分析并展望了其未来应用。     

新疆达坂城盐湖不同植物群落土壤呼吸研究

新疆盐湖分布地域广泛而不均匀。盐湖生态系统碳循环是干旱区生态系统碳循环的重要组分,其动态变化对干旱区碳平衡有着重要的影响,然而目前对干旱区盐湖土壤呼吸的研究相对薄弱。为探讨盐湖沿岸不同植物群落土壤呼吸及其影响因子,以新疆达坂城盐湖为典型研究区,选取沿岸小獐毛(Aeluropus pungens)、鸢尾(Iris tectorum)、芨芨草(Achnatherum splendens)、黑果枸杞(Lycium ruthenicum Murr)植物群落土壤为主要研究对象,以周边农田撂荒地为对照,利用LI-COR 8100对达坂城盐湖沿岸4种植物群落和撂荒地土壤呼吸进行了监测,结果表明:盐湖沿岸土壤呼吸具有明显的日变化。监测时段内土壤呼吸作用均为单峰曲线,排放通量在13:00左右最高,07:00左右出现最低值。不同群落土壤呼吸速率变化范围在0.89~4.34μmol/(m~2·s)之间,撂荒地为1.77~3.48μmol/(m~2·s),表现为黑果枸杞小獐毛芨芨草撂荒地鸢尾。不同植物群落地下生物量影响土壤CO_2排放,研究区土壤呼吸日平均累计CO_2排放通量为209.28 mg/(m~2·d)。土壤呼吸速率与土壤5 cm温度呈现显著正相关(P0.01),可以解释土壤呼吸日变化的69%~78%,是决定达坂城盐湖土壤呼吸变化的主要因子。利用土壤5 cm处温度得到小獐毛、鸢尾、芨芨草、黑果枸杞、撂荒地的Q_(10)值分别为2.30、1.24、1.20、1.57、1.28,小獐毛样地土壤呼吸对温度更敏感。除撂荒地外各群落土壤呼吸与土壤湿度呈显著负相关(R~2=0.38~0.51)。该研究对进一步明确干旱区盐湖生态系统土壤呼吸变化规律和影响因素,以及对估算区域碳平衡及"碳汇"功能具有重要意义。     

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.