低分子量有机酸对不同肥力土壤磷素的活化作用

针对石灰性土壤磷素固定累积问题,采用化学浸提方法,探讨低分子有机酸对不同肥力水平土壤磷素的活化作用,提高磷素的有效性.结果表明,对于低肥力和中肥力土壤,相同浓度下有机酸活化土壤磷的能力表现为草酸＞柠檬酸＞苹果酸;对于高肥力土壤,相同浓度下有机酸活化土壤磷的能力为柠檬酸＞草酸＞苹果酸.低浓度对有机骏对土壤磷的活化有抑制作...     

科尔沁沙地不同植物群落土壤呼吸及环境因素分析

对科尔沁沙地固定、半固定和流动沙丘土壤呼吸的日进程、季节变化及其环境因素进行了测定分析.结果表明:1)土壤呼吸速率与植物群落生物量、土壤有机碳、全氮及粘粉粒含量之间存在显著的正相关关系;固定沙丘日平均土壤呼吸速率分别是半固定和流动沙丘的1.18和2.02倍.2)从固定、半固定到流动沙丘,土壤温度及近地表空气温度呈现增加...     

Can soil respiration estimate neglect the contribution of abiotic exchange？

This study examines the hypothesis that soil respiration can always be interpreted purely in terms of biotic processes, neglecting the contribution of abiotic exchange to CO2 fluxes in alkaline soils of arid areas that characterize 5% of the Earth’s total land surface. Analyses on flux data collected from previous studies suggested reconciling soil respiration as organic(root/microbial respiration) and inorganic(abiotic CO2 exchange) respiration, whose contributions in the total CO2 flux were determined by soil alkaline content. On the basis of utilizing meteorological and soil data collected from the Xinjiang and Central Asia Scientific Data Sharing Platform, an incorporated model indicated that inorganic respiration represents almost half of the total CO2 flux. Neglecting the abiotic module may result in overestimates of soil respiration in arid alkaline lands, which partly explains the long-sought "missing carbon sink".     

土壤温度和水分对不同类型沙丘土壤呼吸的影响

通过实验室土壤培养试验,测定了不同土壤温度(8,18,28,38℃)和含水量对科尔沁退化沙质草地不同生境(流动沙丘,半固定沙丘和固定沙丘)土壤呼吸的影响。结果表明,在8~38℃范围内,土壤呼吸速率与温度呈正相关。在含水量为田间持水量(WFC)的5%~65%范围内,3种类型的土壤呼吸速率随含水量的增加而升高,当超过该范围时,流动沙丘的土壤呼吸速率仍呈上升趋势,而38℃培养条件下的半固定沙丘和18~38℃下的固定沙丘的土壤呼吸速率呈下降趋势。土壤温度和水分对土壤呼吸作用存在明显的交互效应,不同类型沙化土壤呼吸作用强弱存在显著差异。温度系数Q10值随含水量的变化为:流动沙丘1.90~2.15,半固定沙丘1.80~2.13,固定沙丘1.82~2.16。     

陕北毛乌素沙地土壤水分时空变异规律研究

对陕北毛乌素沙地流动、固定、半固定沙丘的土壤水分进行的长期动态观测结果表明,含水量排序为流动沙丘(8.47%)＞半固定沙丘(8.40%)＞固定沙丘(8.39%).沙地含水量随土壤深度的变化存在着分布上的差异,随着深度的增加呈现先增加再减少的趋势,在0～60 cm土层,流动沙丘、半固定沙丘和固定沙丘土壤水分含量分别为8.08%、8.00%和8.03%,差异不显著;在60～200 cm土层,流动沙丘、半固定沙丘和固定沙丘土壤水分含量分别为8.65%、8.57%和8.53%,差异显著(P>0.05),其中60～140 cm层,流动沙丘、半固定沙丘和固定沙丘土壤水分含量分别为8.76%、8.62%和8.54%,差异极显著(P>0.01).固定沙丘、半固定沙丘大部分背风面的土壤含水量高于迎风面的含水量,但在流动沙丘上迎风面的土壤含水量却明显比背风面的高.在沙丘的不同部位含水量也存在差异,土壤含水量坡顶部＜坡中部＜坡底部,在沙丘下部的丘间土壤含水量明显高于丘顶部.另外,沙地水分还受季节变化的影响,具有明显的季节变异性.     

棉花根系分泌物对枯草芽胞杆菌NCD-2生物膜形成和根际定殖的影响

 为明确棉花根系分泌物对生防枯草芽胞杆菌NCD-2生物膜形成的影响,本研究首先比较了菌株NCD-2在不同棉花品种(冀棉11、中棉所41、中植棉2号、鲁棉29和海岛棉Pima90)根际的定殖能力。结果表明,菌株NCD-2在Pima90的根际定殖能力最强,播种35 d后在根际的群体数量达到7.63×10⁵ CFU·g^-1根重;而在中植棉2号的根际定殖能力最弱,播种35 d后根际菌株NCD-2的群体数量为6.51×10⁴ CFU·g^-1根重。通过再循环水培系统收集根系分泌物的方法获得了不同棉花品种的根系分泌物,测定了其对菌株NCD-2生物膜形成的影响。结果表明,海岛棉Pima90的根系分泌物对该菌株生物膜形成的促进作用最强,而中植棉2号的根系分泌物对菌株NCD-2生物膜形成影响最弱。进一步分析了棉花根系分泌物中6种糖分和13种氨基酸对菌株NCD-2生物膜形成的影响,结果发现,葡聚糖和脯氨酸显著促进了该菌株的生物膜形成。     

Scale dependence of plant species richness and vegetation-environment relationship along a gradient of dune stabilization in Horqin Sandy Land,Northern China

Ecological patterns and processes in dune ecosystems have been a research focus in recent years, however the information on how dune stabilization influences the spatial scale dependence of plant diversity is still lacking. In this study, we measured the plant species richness, soil properties and altitude across four spatial scales(1, 10, 100 and 1,000 m2) at three different dune stabilization stages(mobile dune, semi-fixed dune and fixed dune) in Horqin Sandy Land, Northern China. We also examined the relationships between plant species richness, community composition and environmental factors along the gradient of dune stabilization. Our results showed that plant species richness increased with the increase of spatial scales in each dune stabilization stage, as well as with the increase of dune stabilization degrees. Canonical correspondence analysis(CCA) showed that plant distribu- tions in the processes of dune stabilization were determined by the combined environmental gradient in relation to soil organic carbon(SOC), total nitrogen(TN), carbon/nitrogen(C/N), pH, electrical conductivity(EC), soil water content(SWC), fine sand(FS), very fine sand(VFS), silt and clay(SC), and altitude. Plant species richness was significantly and positively correlated to SOC and TN in mobile dune, and significantly and positively correlated to SOC, TN, C/N, VFS and SC in semi-fixed dune. However, no significant correlation between plant species richness and environmental factors was observed in fixed dune. In addition, plant species richness in different dune stabili- zation stages was also determined by the combined gradient of soil properties and altitude. These results suggest that plant species richness has obvious scale dependence along the gradient of dune stabilization. Soil resources depending on dune habitats and environmental gradients caused by dune stabilization are important factors to de- termine the scale dependence of species diversity in sand dune ecosystems.     

旱区灌溉棉田土壤呼吸昼夜变化特征及其与土壤温度的关系

本试验以裸地为对照,通过对土壤剖面CO2浓度的监测,研究了旱区灌溉棉田土壤呼吸的昼夜变化规律及其与土壤温度的关系。主要结果如下:(1)土壤及根际呼吸均呈"V"型昼夜变化特征,最小值出现在16∶00~17∶00之间,而土壤微生物呼吸昼夜变化趋势与之相反;(2)土壤微生物呼吸产生的CO2通量在土壤升温阶段略高于降温阶段,相对的,根际呼吸在土壤升温阶段产生的CO2通量低于降温阶段,并形成一个明显的逆时针圆圈;(3)棉花根际呼吸对土壤呼吸的平均贡献率为47%。以上结果说明,在建立土壤呼吸与土壤温度相关关系模型的过程中,需要区分根际呼吸和土壤微生物呼吸,充分考虑土壤温度变化对土壤呼吸各组分影响的差异性。     

马铃薯根系分泌物组分对不同种植模式的响应

作物根系分泌物与作物连作障碍密切相关,为寻求减小作物连作障碍的途径,在轮作(大豆-马铃薯)、固定间作(马铃薯/大豆)和马铃薯连作3种种植模式下,分离鉴定了马铃薯根系分泌物的主要组分。结果表明:与轮作处理相比,固定间作和连作处理马铃薯根系分泌物种类分别增加了13.79%和17.24%,烷烃类物质的相对含量分别增加了52.17%和52.60%,酸类物质的相对含量分别增加了65.41%和14.79%。连作处理马铃薯根系分泌物中鉴定出乙胺、N-乙基吗啉和邻苯二甲酸二丁酯的相对含量分别为1.46%、2.87%和5%,而在轮作和间作处理中均未检测到。与轮作处理相比,间作和连作处理N,N-二乙基乙酰胺相对含量分别高出123.29%和47.95%,棕榈酸相对含量分别高出23.18%和40.0%,硬脂酸相对含量分别高出27.36%和39.80%。说明大豆-马铃薯轮作可有效降低马铃薯根系分泌物组分的种类和含量。因此,生产实践中,可通过大豆-马铃薯轮作克服因某一种马铃薯化感物质累积而造成的毒害作用。     

阿拉善荒漠功能灌木群的土壤呼吸动态研究

使用LI-8100仪器实测了在生长季阿拉善的梭梭、沙冬青、红砂、华北驼绒藜、珍珠、白刺六种植物群落土壤呼吸速率,使用挖刨面法逐月测定了土壤温度和土壤含水量。结果表明:这六种荒漠植物群落土壤呼吸速率日动态均呈单峰型,最高值皆出现在12:00-14:00,最低值出现在早晨8:00,土壤呼吸速率最大值出现时间先于气温最高值出现的时间。六种植物群落土壤呼吸速率的月变化呈单峰曲线,与近地面气温的变化趋势一致。六种植物群落土壤呼吸速率的日变化与地表温度达到极显著正相关关系,与近地面气温、5cm、10cm温度具有显著相关性。六种植物群落与土壤含水量0-10cm、10-20cm、20-30cm都没有显著相关性。在源与汇的问题上,梭梭、沙冬青、红砂、珍珠、华北驼绒藜、白刺是汇。     

二氧化碳在华北大黑鳃金龟幼虫定位寄主植物根系中的作用

为探究二氧化碳(CO2)在华北大黑鳃金龟Holotrichia oblita幼虫定位寄主植物根系时所发挥的作用,对其开展了触角电位生理反应及行为生测试验.研究结果表明,CO2浓度为0.75％、1.5％、3％、6％时均能显著激发幼虫的触角电位和趋性反应,且随着浓度增加幼虫对CO2的趋向爬行所用时间显著缩短;根系分泌物同样...     

Influences of drip and flood irrigation on soil carbon dioxide emission and soil carbon sequestration of maize cropland in the North China Plain

The need is pressing to investigate soil CO_2(carbon dioxide) emissions and soil organic carbon dynamics under water-saving irrigation practices in agricultural systems for exploring the potentials of soil carbon sequestration. A field experiment was conducted to compare the influences of drip irrigation(DI) and flood irrigation(FI) on soil organic carbon dynamics and the spatial and temporal variations in CO_2 emissions during the summer maize growing season in the North China Plain using the static closed chamber method. The mean CO_2 efflux over the growing season was larger under DI than that under FI. The cumulative CO_2 emissions at the field scale were 1959.10 and 1759.12 g/m~2 under DI and FI, respectively. The cumulative CO_2 emission on plant rows(OR) was larger than that between plant rows(BR) under FI, and the cumulative CO2 emission on the irrigation pipes(OP) was larger than that between irrigation pipes(BP) under DI. The cumulative CO_2 emissions of OP, BP and bare area(BA) under DI were larger than those of OR, BR and BA under FI, respectively. Additionally, DI promoted root respiration more effectively than FI did. The average proportion of root respiration contributing to the soil CO_2 emissions of OP under DI was larger than that of OR under FI. A general conclusion drawn from this study is that soil CO_2 emission was significantly influenced by the soil water content, soil temperature and air temperature under both DI and FI. Larger concentrations of dissolved organic carbon(DOC), microbial biomass carbon(MBC) and total organic carbon(TOC) were observed under FI than those under DI. The observed high concentrations(DOC, MBC, and TOC) under FI might be resulted from the irrigation-associated soil saturation that in turn inhibited microbial activity and lowered decomposition rate of soil organic matter. However, DI increased the soil organic matter quality(the ratio of MBC to TOC) at the depth of 10–20 cm compared with FI. Our results suggest that the transformation from conventional FI to integrated DI can increase the CO2 emissions and DI needs to be combined with other management practices to reduce the CO_2 emissions from summer maize fields in the North China Plain.     

低分子量有机酸对二氯喹啉酸在土壤中吸附-解吸的影响

采用高效液相色谱仪及批量平衡试验方法,研究了乙酸、苹果酸、酒石酸、草酸、丁二酸和柠檬酸6种低分子量有机酸对麻沙泥和第四纪红土红壤吸附-解吸二氯喹啉酸的影响。结果表明:低分子量有机酸可推迟二氯喹啉酸在土壤中的吸附平衡时间,其吸附动力学过程可用准二级动力学方程描述。Linear和Freundlich方程能较好地拟合二氯喹啉酸在供试两种土壤中的吸附等温线;二氯喹啉酸在麻沙泥中的吸附能力(lg Kf值)从大到小依次为苹果酸柠檬酸草酸=乙酸丁二酸酒石酸,在第四纪红土红壤中为苹果酸丁二酸乙酸草酸柠檬酸酒石酸;低分子量有机酸浓度对二氯喹啉酸解吸的影响因有机酸种类和供试土壤的不同而差异较大,6种供试有机酸均促进了第四纪红土红壤对二氯喹啉酸的解吸,且其解吸率均明显高于麻沙泥对二氯喹啉酸的解吸率,但在麻沙泥中呈现不同的影响模式。     

Carbon sequestration in the total and light fraction soil organic matter along a chronosequence in grazing exclosures in a semiarid degraded sandy site in China

Horqin Sandy Land is a fragile,seriously desertified region located in Inner Mongolia of China.Overgrazing is one of the primary drivers of desertification in this region.We investigated whether the establishment of grazing exclosures in areas with active sand dunes enhances soil carbon(C) sequestration and benefits soil recovery.The results showed that soil organic C storage was 1.4,1.9,and 3.5 times,and light fraction C storage was 2.3,3.2,and 4.4 times in the 100-cm topsoil after 7,12,and 25 years of grazing exclusion,respectively,compared to the case in active sand dunes.The light fraction of soil played an important role in soil C sequestration,although it might not change rapidly to provide an early indication of how soil C is increasing in response to grazing exclusion.The results indicated that soils could potentially sequester up to 13.8 Mt C in 25 years if active sand dunes in the study area were to be protected by exclosures.This corresponds to 12.8% of the estimated carbon loss(107.53 Mt) that has been associated with desertification over the past century in the Horqin Sandy Land.Our results suggested that exclosures have the capacity to increase soil C sequestration;however,decades will be required for soil C to recover to historical grassland levels observed prior to desertification.     

黄瓜枯萎病菌菌丝际细菌种群丰度变化及其影响黄瓜生长的原因初探

菌丝际细菌存在于真菌与土壤发生强烈反应的狭小区域。连作导致黄瓜枯萎病菌尖孢镰孢菌Fusarium oxysporum f.sp.cucumerinum（Foc）菌丝际细菌种群组成发生变化。本研究根据非连作土（MC）、连作土（SC）中Foc菌丝际细菌类群根瘤菌Rhizobium sp.、无色杆菌Achromobacter sp.、申氏杆菌Shinella sp.和寡养单胞菌Stenotrophomonas sp.在种群中的丰度，设计了相应的含有不同比例细菌的组合HB-1（33：8：7：6）和HB-2（41：12：2：1）。采用平板生测法测定了这4个属的菌丝际细菌代表菌株76、77、252和29的比例变化对黄瓜生长的影响结果表明，用非连作土细菌组合HB-1处理的黄瓜幼苗高于连作土细菌组合HB-2处理。采用"V"字型平板共培养法测定菌株间是否存在互作，并在96孔板中测定了菌丝际细菌培养滤液对其他菌株及自身生长的影响结果表明，4个细菌之间存在互作，菌株76的培养滤液明显促进菌株77的生长，菌株77代谢物抑制其自身生长。在96孔板中测定了4个细菌对黄瓜根分泌物合成培养液中不同碳源的利用能力结果表明，菌株76对各种碳源利用能力最强，菌株252在葡萄糖为主要碳源的根分泌物中生长最好；HB-1组合和HB-2组合在5种不同碳源根分泌物中都能较好生长。对4个菌株产IAA能力的测定结果表明：菌株76的IAA产量较高且持久，最高可达19.4 mg/L，菌株252的IAA产量在60 h达到峰值，最高可达22.1 mg/L；组合HB-1产生IAA能力始终高于组合HB-2。上述结果表明，菌株互作和对黄瓜根分泌物的利用能力是黄瓜枯萎病菌菌丝际细菌种群变化的重要影响因素；菌丝际细菌比例变化影响黄瓜生长，菌株互作产生IAA能力是影响黄瓜生长的重要因子。该研究为维护连作条件下黄瓜健康生长提供了新的线索。     

Carbon inputs regulate the temperature sensitivity of soil respiration in temperate forests

Litter and root activities may alter the temperature sensitivity (Q₁₀) of soil respiration. However, existing studies have not provided a comprehensive understanding of the effects of litter and root carbon inputs on the Q₁₀ of soil respiration in different seasons. In this study, we used the trench method under in situ conditions to measure the total soil respiration (R_total), litter-removed soil respiration (R_no-litter), root-removed soil respiration (R_no-root), and the decomposition of soil organic matter (i.e., both litter and root removal; R_SOM) in different seasons of pioneer (Populus davidiana Dode) and climax (Quercus liaotungensis Mary) forests on the Loess Plateau, China. Soil temperature, soil moisture, litter biomass, fine root biomass, litter carbon, and root carbon were analyzed to obtain the drive mechanism of the Q₁₀ of soil respiration in the two forests. The results showed that the Q₁₀ of soil respiration exhibited seasonality, and the Q₁₀ of soil respiration was higher in summer. The litter enhanced the Q₁₀ of soil respiration considerably more than the root did. Soil temperature, soil moisture, fine root biomass, and litter carbon were the main factors used to predict the Q₁₀ of different soil respiration components. These findings indicated that factors affecting the Q₁₀ of soil respiration highly depended on soil temperature and soil moisture as well as related litter and root traits in the two forests, which can improve our understanding of soil carbon-climate feedback in global warming. The results of this study can provide reference for exploring soil respiration under temperate forest restoration.     

Microbe-Mediated Germination of Ascospores of Monosporascus cannonballus

ABSTRACT Ascospores of Monosporascus cannonballus germinated readily in the rhizosphere of cantaloupe plants growing in field soil. However, little or no germination occurred in the rhizosphere of melon plants growing in field soil that was autoclaved prior to infestation with ascospores. The latter data suggested that root exudates alone do not stimulate ascospore germination and that the soil microflora may be involved in the induction of ascospore germination. Amending field soil with streptomycin (which inhibits gram-negative microorganisms) did not suppress ascospore germination in the rhizosphere of cantaloupe plants. However, amending the soil with penicillin (which inhibits gram-positive microorganisms) did suppress ascospore germination. Pentachloronitrobenzene (PCNB), which inhibits the gram-positive actinomycetes but does not inhibit gram-positive or gram-negative bacteria, also suppressed ascospore germination. These results suggest that actinomycetes, either directly or indirectly, are involved in the induction of ascospore germination in field soil in the presence of exudates from cantaloupe roots. Optimum germination occurred at temperatures ranging from 25 to 35 degrees C, and data indicate that a high percentage (>/=72%) of the ascospore population within 500 mum of a root are capable of germination and subsequent penetration of cantaloupe roots.     

Carbon Loss and Germinability, Viability, and Virulence of Chlamydospores of Fusarium solani f. sp. phaseoli After Exposure to Soil at Different pH Levels, Temperatures, and Matric Potentials

ABSTRACT (14)C-labeled chlamydospores of Fusarium solani f. sp. phaseoli were exposed to soil at 5, 15, 25, or 30 degrees C at pH 5 or 8 and water potential of -1 kPa or to soil at 0, -1, or -10 kPa at 25 degrees C at pH 6.9. Total carbon loss was greatest at 25 or 30 degrees C at pH 8 and -1 kPa. (14)CO(2) from respiration of chlamydospores and from soil microbes utilizing chlamydospore exudates accounted for the largest share of total carbon loss under all conditions. (14)(CO)(2) from soil microbial metabolism of (14)CO(2) exudates of chlamydospores was greatest in soil at 15, 25, and 30 degrees C, pH 8, and at either -1 or -10 kPa. Chlamydospore germinability in the absence of a C source (nutrient independence), viability in potato-dextrose broth, and virulence to kidney bean declined rapidly after exposure to soil at high temperatures (25 and 30 degrees C), pH 8, and the higher matric potentials (0 to-1 kPa). By contrast, germinability remained high (>50%), as did virulence, in soil at 5 degrees C and -10 kPa even after 70 days of incubation. Carbon loss was inversely correlated with germinability, viability, and virulence after exposure to soil at different pH levels, temperatures, and matric potentials.     

Increased rhizosphere populations of Trichoderma asperellum strain T34 caused by secretion pattern of root exudates in tomato plants inoculated with Botrytis cinerea

Root exudates secreted from plants can modify rhizosphere microbiota by enhancing or inhibiting the growth of biological control agents (BCAs) and/or pathogens. Similarly, microorganisms can modify the secretion of plant root exudates. The aim of this study was to analyse the effect of a Botrytis cinerea leaf infection on the secretion of tomato root exudates and on the populations of the BCA Trichoderma asperellum strain T34 (T34). This study found that the secretion pattern of root exudates in tomato plants was influenced by B. cinerea infection in plant leaves. An increase in the levels of gluconic acid was observed, while levels of sucrose and inositol decreased. A decrease in the severity of B. cinerea by the induction of systemic resistance triggered by T34 was also observed. Tomato plants infected with B. cinerea maintained the populations of T34 in the roots, while populations of T34 decreased in plants not inoculated with the pathogen. Samples exposed to media containing gluconic acid (as the only carbon source or at the same concentration found in roots exudates) saw an increase in the in vitro growth of T34 compared to media without gluconic acid. In conclusion, a change in the secretion pattern of root exudates caused by B. cinerea, together with the enhanced growth of T34 in the presence of gluconic acid, indicates the existence of leaf to root communication. The result of this is enhanced populations of T34, and in turn induced disease resistance and a consequential reduction in disease severity.     

低分子量有机酸对粘土矿物吸附二氯喹啉酸的影响

采用批量平衡法,研究了6种低分子量有机酸(柠檬酸、酒石酸、苹果酸、乙酸、草酸和丁二酸)对3种粘土矿物(高岭土、蒙脱石、凹凸棒石)吸附二氯喹啉酸的影响。结果表明:当低分子量有机酸存在时,供试3种粘土矿物对二氯喹啉酸的吸附过程可用Linear和Freundlich吸附等温方程描述,且Freundlich方程的拟合效果更好。供试6种有机酸对二氯喹啉酸在高岭土中吸附量的影响程度从低到高依次为苹果酸<柠檬酸<草酸<乙酸<酒石酸<丁二酸,在蒙脱石中的顺序为乙酸<草酸<苹果酸<丁二酸<酒石酸<柠檬酸,在凹凸棒石中的顺序为乙酸<丁二酸<草酸<苹果酸<酒石酸<柠檬酸。不同浓度低分子量有机酸对3种供试粘土矿物吸附二氯喹啉酸均能产生显著的影响,但影响程度因粘土矿物和有机酸种类的不同而有较大差异。