秸秆还田量对土壤CO2释放和土壤微生物量的影响

对玉米季、小麦季3种不同秸秆还田量的土壤生物学指标的测定结果表明,在秸秆倍量还田中,随着秸秆量的增加,CO₂释放量增加,而且倍量处理的增加量显著大于全量处理;在玉米和小麦季节中,不同量秸秆还田对土壤0～10和10～20cm的土壤微生物量的影响不同,但均能增大土壤微生物量,全量和倍量处理间没有明显差异.在土壤表层及下层,微生物量的最大值均落后于土壤呼吸的最大值,且土壤微生物量达到最大值即其最活跃状态后,下降缓慢,但土壤呼吸减少较快,说明微生物活动存在明显的合成性呼吸与维持性呼吸;综合评价不同秸秆量还田的效应,应采用秸秆全量还田,既能调节土壤物理环境,促进微生物的代谢活动,利于养分的转化,又可以减少环境污染.     

秸秆预处理对土壤微生物量及呼吸活性的影响

冬小麦秸秆经8．0g·L^-1H2O2(pH11．0)溶液、12．5g·L^-1 NaOH溶液或H2SO4溶液浸泡8h并80℃烘干后,与无机N一起加入土壤,进行室内25℃恒温培养试验,在不同时间测定土壤微生物量C、N和CO2释放速率。结果表明,培养前期,秸秆预处理使土壤微生物量C数量增加了1．0～1．4倍,但降低了土壤微生物的呼吸活性;培养后期,NaOH和H2SO4处理使土壤微生物量C分别下降了28％和42％,但增加了土壤微生物的呼吸活性;H2O2处理则使土壤微生物量N增加90％;土壤微生物区系中的真菌比例在不同时刻有所增加,表明将秸秆预处理后施入土壤,将对土壤中微生物数量和呼吸活性产生一定影响。     

秸秆还田量对土壤CO2释放和土壤微生物量的影响

对玉米季、小麦季3种不同秸秆还田量的土壤生物学指标的测定结果表明,在秸秆倍量还田中,随着秸秆量的增加,CO2释放量增加,而且倍量处理的增加量显著大于全量处理;在玉米和小麦季节中,不同量秸秆还田对土壤0～10和10～20cm的土壤微生物量的影响不同,但均能增大土壤微生物量,全量和倍量处理间没有明显差异、在土壤表层及下层,微生物量的最大值均落后于土壤呼吸的最大值,且土壤微生物量达到最大值即其最活跃状态后,下降缓慢,但土壤呼吸减少较快,说明微生物活动存在明显的合成性呼吸与维持性呼吸;综合评价不同秸秆量还田的效应,应采用秸秆全量还田,既能调节土壤物理环境,促进微生物的代谢活动,利于养分的转化,又可以减少环境污染。     

黄土高原柴松(Pinus tabulaeformis f.shekannesis)群落的植物物种多样性

物种多样性格局与所选择的尺度密切相关,用加性分配法分析柴松(Pinus tabulaeformis f.shekannesis)群落乔木、灌木和草本层在样方、坡位和坡面3种尺度的物种多样性分配关系,结果表明:1)以物种丰富度为指标时,坡面尺度对区域多样性贡献最大,说明在区域范围内坡面是物种组成和维持的关键尺度;而以Shannon和Simpson多样性为指标时,最大多样性分配在样方内,这是由于这2个指数不仅考虑了物种数,还考虑了样方内多度以及常见种和稀有种的影响和作用;2)以Shannon多样性为指标时,样方间、坡位间和坡面间尺度的β多样性对区域多样性贡献的百分比都大于以Simpson多样性为指标时的百分比,这主要是由稀有种在各尺度间的分布格局所决定的;3)样方间、坡位间和坡面间尺度的β多样性大小顺序各不相同,这与群落乔木层、灌木层和草本层的物种组成和分布情况以及不同尺度间环境异质性有密切关系。     

26年长期施肥对土壤微生物量碳、氮及土壤呼吸的影响

研究长期小麦连作施肥条件下土壤微生物量碳、氮,土壤呼吸的变化及其与土壤养分的相关性。以陕西长武长期定位试验为平台,应用氯仿熏蒸-K2SO4提取法、碱液吸收法和化学分析法分析了长达26a不同施肥处理农田土壤微生物量碳、微生物量氮和土壤呼吸之间的差异及其调控土壤肥力的作用。长期施肥及种植作物,均能提高土壤微生物量碳、氮含量,尤其是施用有机肥,土壤微生物量碳、氮含量高于单施无机肥的处理,土壤呼吸量也提高15.91%—75.73%,而施用无机肥对于土壤呼吸无促进作用。土壤微生物生物量碳氮、土壤呼吸与土壤有机质、全氮呈极显著相关。长期有机无机肥配施可以提高土壤微生物量碳氮、土壤呼吸,氮磷肥与厩肥配施对提高土壤肥力效果最好。微生物量碳氮及土壤呼吸可以反映土壤质量的变化,作为评价土壤肥力的生物学指标。     

Microbial biomass and nitrogen cycling responses to fertilization and litter removal in young northern hardwood forests

The influence of site fertility on soil microbial biomass and activity is not well understood but is likely to be complex because of interactions with plant responses to nutrient availability. We examined the effects of long-term (8 yr) fertilization and litter removal on forest floor microbial biomass and N and C transformations to test the hypothesis that higher soil resource availability stimulates microbial activity. Microbial biomass and respiration decreased by 20–30 % in response to fertilization. Microbial C averaged 3.8 mg C/g soil in fertilized, 5.8 mg C/g in control, and 5.5 mg C/g in litter removal plots. Microbial respiration was 200 µg CO₂-C g^–1 d^–1 in fertilized plots, compared to 270 µg CO₂-C g^–1 d^–1 in controls. Gross N mineralization and N immobilization did not differ among treatments, despite higher litter nutrient concentrations in fertilized plots and the removal of substantial quantities of C and N in litter removal plots. Net N mineralization was significantly reduced by fertilization. Gross nitrification and NO₃ ^– immobilization both were increased by fertilization. Nitrate thus became a more important part of microbial N cycling in fertilized plots even though NH₄ ⁺ availability was not stimulated by fertilization.Soil microorganisms did not mineralize more C or N in response to fertilization and higher litter quality; instead, results suggest a difference in the physiological status of microbial biomass in fertilized plots that influenced N transformations. Respiration quotients (qCO₂, respiration per unit biomass) were higher in fertilized plots (56 µg CO₂-C mg C^–1 d^–1) than control (48 µg CO₂-C mg C^–1 d ^–1) or litter removal (45 µg CO₂-C mg C^–1 d^–1), corresponding to higher microbial growth efficiency, higher proportions of gross mineralization immobilized, and lower net N mineralization in fertilized plots. While microbial biomass is an important labile nutrient pool, patterns of microbial growth and turnover were distinct from this pool and were more important to microbial function in nitrogen cycling.     

Priming effect after glucose amendment in two different soils evaluated by SIR- and PLFA-technique

This study investigated the metabolic and structural effects of adding glucose to the top soils of a contaminated sandy Eutric Cambisol and an uncontaminated silty Haplic Chernozem during substrate-induced respiration (SIR) measurement. We hypothesized that glucose amendment causes microbial community shifts. To indicate changes of the microbial structure during SIR measurement, we have evaluated the microbial community structure using phospholipid fatty acid (PLFA) analysis on soil samples immediately before they were enclosed in SIR apparatus (Start), after the equilibrium of basal respiration had been reached (Con-0), 8 h later (Con-8), and on the other hand immediately after adding glucose (Glu-0), and 8 h after that (Glu-8).The accumulated PLFA content of Start, Con-0 and Con-8 was of the same order of magnitude with no significant differences among them in the contaminated sandy Eutric Cambisol. In contrast, PLFA-biomass of the Glu-0 sample was only 52% of that measured in the Start. Furthermore, the PLFA-biomass was reduced even more drastically to 20% compared to the original Start value in Glu-8. The reduction of PLFA-microbial biomass after glucose amendment was accompanied by the inverse reaction of basal respiration. The PLFA profiles were dominated by the group of saturated fatty acids in the case of Start, Con-0 and Con-8, but by unsaturated fatty acids in the Glu-0 and Glu-8. In contrast to these results, the uncontaminated silty Haplic Chernozem showed no significant differences between Start, Con-0 and Glu-0 but a 243% and a 274% higher PLFA content of Con-8 and Glu-8 compared to the Start, respectively.The findings of triggered metabolic activities indicate that the microflora of these soils is affected and that PLFA analysis reflects a shift in the soil microbial community after adding glucose. We hypothesized that this shift from slow-growing microbial oligotrophs with low substrate needs to fast-growing copiotrophs with high substrate demands might be caused by the glucose added. Structural differences of the microbial community before and after glucose amendment should be taken into consideration when interpreting the metabolic SIR results in future.     

淹水培养条件下土壤微生物生物量碳、氮和可溶性有机碳、氦的动态

以洞庭湖区2个典型水稻土（红黄泥和紫潮泥）为对象,研究了25℃、淹水培养条件下稻草-硫铵配施和单施硫铵处理土壤微生物生物量碳、氮（SMBC、SMBN）和可溶性有机碳、氦（SDOC、SDON）的动态变化．结果表明,SMBC、SMBN和SDOC、SDON在培养前期达到峰值,之后降低,并趋于稳定．添加底物后,2种土壤不同处理土壤微生物生物量碳与有机碳（SMBC／TC）和土壤微生物生物量氮与全氮（SMBN／TN）的平均值都在2％-3％之间变化;可溶性碳与全碳（SDOC／TC）的平均值为1％左右,可溶性氮与全氮（SDON／TN）平均值为5％-6％．2种土壤中SMBC峰值单施硫铵处理最大,但与稻草-硫铵配施处理差异均不显著;SMBN、SDOC和SDON峰值稻草-硫铵配施最大．稻草．硫铵配施与单施硫铵处理中,低肥力红黄泥的SMBN、SDOC和SDON峰值差异显著;而高肥力紫潮泥SMBN和SDOC峰值差异不显著．前7d,SMBC／SMBN〈10;14d后,同一时刻单施硫铵处理SMBC／SMBN〉稻草．硫铵配施．不同处理的SDOC!SDON3d时最大．28d时最小．     

保护性耕作对土壤微生物量及活性的影响

研究保护性耕作对土壤微生物特性的影响对于土壤管理具有重要意义。试验研究了保护性耕作对麦田土壤微生物量碳、活跃微生物量、土壤呼吸、呼吸商的影响。前3项采用的方法分别是:基质诱导呼吸法、呼吸曲线数学分析法和CO2释放量法。结果表明,保护性耕作土壤微生物量碳0～10cm土层大于10～20cm土层,而常规耕作两土层间无明显差异。秸秆还田在播种前、越冬期和起身期能显著提高土壤微生物量碳,而开花期和收获期则降低土壤微生物量碳。少耕还田10～20cm土层微生物具有较强的养分调控作用。保护性耕作利于0～10cm土层活跃微生物量的提高。秸秆还田和保护性耕作在耕作作业初期(越冬期和起身期)能增强土壤呼吸速率;在耕作作业后期(开花期和收获期)能显著降低土壤呼吸速率。免耕秸秆覆盖在10～20cm土层呼吸商较高,而常规耕作无秸秆还田在0～10cm土层呼吸商较高。土壤微生物量碳和呼吸商是衡量土壤微生物特性的重要指标。     

冀北辽河源自然保护区土壤微生物碳代谢特征对凋落物分解主场效应的响应

通过凋落物袋法研究了冀北辽河源地区表层0～5、5～10和10～20 cm土壤微生物生物量碳、微生物呼吸速率和微生物代谢熵对白桦及蒙古栎叶凋落物分解主场效应的响应过程.结果表明： 主场白桦及蒙古栎凋落物处理土壤微生物生物量碳显著高于客场;而土壤微生物呼吸则差异不显著.土壤微生物生物量碳、微生物呼吸对不同植物凋落物分解主场效应的响应程度也不一致.客场蒙古栎叶凋落物处理各土层土壤微生物生物量碳相比主场降低了39.6%、34.9%、33.5%;白桦凋落物则降低了31.6%、27.1%、17.0%.客场蒙古栎凋落物微生物呼吸分别为主场的96.3%、92.4%、83.7%,白桦凋落物为99.4%、97.3%、101.3%.微生物代谢熵则呈现出与微生物生物量碳相反的变化趋势.植物凋落物在主场分解速率较快,可供微生物利用的养分较多,促进了土壤微生物的活动,且土壤中丰富的有机质削弱了植物摄取与微生物需求之间的矛盾,进而导致土壤微生物生物量碳及微生物代谢熵对叶凋落物分解主场效应产生了明显的响应.而土壤微生物呼吸由于受到林地内土壤温度、含水率以及二者共同作用的影响,对主场效应表现出了微弱的响应.此外,由于低质量凋落物会表现出更强的主场效应,从而使土壤微生物生物量碳、微生物呼吸及微生物代谢熵对白桦叶凋落物分解主场效应的响应程度低于蒙古栎凋落物.     

DOM对米槠次生林不同土层土壤微生物呼吸及其熵值的影响

可溶性有机质(Dissolved organic matter,DOM)作为土壤可溶性有机碳的重要来源,进入土壤之后通过改变土壤微生物数量和活性影响土壤矿化。DOM输入对土壤微生物呼吸和熵值的研究多集中在表层土壤,但对深层土壤微生物呼吸和熵值的影响关注较少。通过室内培养实验(120 d)研究米槠(Castanopsis carlesii)鲜叶DOM添加对表层土壤(0—10 cm)和深层土壤(40—60 cm)微生物呼吸及其土壤代谢熵和微生物熵的影响,为揭示DOM输入对亚热带森林土壤碳过程的影响提供理论依据。结果表明,在培养第1天,添加DOM的表层和深层土壤CO_2瞬时排放速率均显著高于对照(P0.001),分别是对照(不添加DOM)的3.58倍和6.93倍,之后显著下降。就累积排放量而言,无论是DOM添加处理还是对照,表层土壤显著大于深层土壤;在米槠鲜叶DOM添加后,表层土壤累积排放量显著大于对照的表层土壤(P0.001),但DOM添加处理深层土壤累积排放量与对照的深层土壤无明显差异。就微生物生物量碳而言,表层土壤微生物生物量碳含量在培养期间显著大于深层土壤。在整个添加DOM培养期间,表层土壤微生物生物量碳含量显著大于表层对照土壤,深层土壤微生物生物量碳含量显著大于深层对照土壤(第3天除外)。培养结束时(120 d),米槠鲜叶DOM添加处理下,表层土壤和深层土壤有机碳含量与第3天相比分别减少26%和19%。米槠鲜叶DOM添加处理后的深层土壤代谢熵(qCO_2)显著低于对照的深层土壤和DOM添加处理的表层土壤qCO_2(P0.001),说明外源DOM进入深层土壤后提高了土壤微生物对碳的利用效率。米槠鲜叶DOM添加处理后的深层土壤微生物熵是培养第3天的1.58倍,显著大于培养初期(P0.05),而DOM添加处理的表层土壤、对照的表层土壤与深层土壤的微生物熵分别是培养第3天的68%、79%和21%,说明DOM添加提高了深层土壤质量。     

施肥对日光温室黄瓜生长和土壤生物学特性的影响

采用田间试验研究了施肥对黄土高原日光温室黄瓜生长发育和产量,以及对土壤微生物区系和土壤酶活性的影响。结果表明,施用有机肥和沼肥明显促进了黄瓜生长发育,提高了黄瓜产量,叶面施肥可以降低无机化肥和有机肥用量,施肥对日光温室土壤生物学特性有明显影响,施用有机肥和叶面施肥增加了土壤细菌数量;施用无机化肥和沼肥增加了真菌的数量,施用有机肥降低了真菌的数量;施肥增加了放线菌的数量．同时施肥提高了土壤脲酶、磷酸酶、蔗糖酶活性,但对过氧化氢酶影响较小．施用有机肥提高了脲酶和磷酸酶活性,施用化肥和沼肥对土壤脲酶和土壤磷酸酶活性影响差异不大。     

川西亚高山森林土壤呼吸和微生物生物量碳氮对施氮的响应

随着全球大气氮沉降的明显增加,将有可能显著影响我国西部地区受氮限制的亚高山森林生态系统。土壤微生物是生态系统的重要组成部分,是土壤物质循环和能量流动的重要参与者。由于生态系统类型、土壤养分、氮沉降背景值等的差异,土壤呼吸和土壤生物量碳氮对施氮的响应存在许多不确定性。而施氮会不会促进亚高山森林生态系统中土壤呼吸和微生物对土壤碳氮的固定?基于此假设,选择了川西60年生的四川红杉(Larix mastersiana)亚高山针叶林为研究对象,通过4个水平的土壤施氮控制试验(CK:0 g m~(-2) a~(-1)、N1:2 g m~(-2)a~(-1)、N2:5 g m~(-2) a~(-1)、N3:10 g m~(-2)a~(-1)),监测了土壤呼吸及土壤微生物生物量碳氮在一个生长季的动态情况。结果表明:施氮对土壤呼吸各指标和土壤微生物碳氮都有极显著的影响,施氮能促进土壤全呼吸、自养呼吸、异养呼吸通量和土壤微生物生物量碳氮的增长,施氮使土壤呼吸通量提高了11%—15%,土壤微生物量碳提高了5%—9%,土壤微生物量氮提高了23%—34%。在中氮水平下(5 g m~(-2) a~(-1))对土壤呼吸的促进最显著。相关分析发现,土壤呼吸与微生物生物量碳氮和微生物代谢商极呈显著正相关,微生物量碳氮与土壤温度呈极显著的正相关,与土壤湿度呈极显著负相关。通过一般线性回归拟合土壤呼吸速率与土壤10 cm温湿度的关系,发现土壤呼吸速率与土壤温度呈极显著的正相关,与土壤湿度极显著负相关(P0.001),中氮水平下土壤温度敏感性系数Q_(10)值(7.10)明显高于对照(4.26)。     

Chemistry and microbial activity of forest and pasture riparian-zone soils along three Pacific Northwest streams

Throughout the United States, agricultural practices are responsible for large quantities of nutrients entering lakes and streams. Previous studies have shown that forested riparian areas can filter nutrients from surface runoff and groundwater that may potentially contaminate lakes and streams. This study examined seasonal differences in soil chemistry and soil microorganisms in paired mixed-forest riparian and pasture systems, the aim being to gain understanding of the sequestering of N and P. The forest soils retained higher levels of organic C and N, mineralizable N, extractable P, and fungal biomass, and had higher respiration rates than pasture soils. These findings suggest that forested riparian zones have a greater capacity than pasture soils to sequester C and retain nutrients. In past studies, fungal biomass has been shown to be less than bacterial biomass in grassland soils, but in this study, fungal biomass was greater than bacterial biomass throughout the year in both forest and pasture soils.     

长期施肥对双季稻田土壤微生物学特性的影响

为探明不同施肥处理对早稻和晚稻各个生育时期稻田土壤微生物生物量碳、氮和微生物熵的影响,以湖南宁乡长期定位试验为平台,应用氯仿熏蒸-K_2SO_4提取法和化学分析法系统分析了定位长达29年5种施肥处理之间(化肥、秸秆还田+化肥、30%有机肥+70%化肥、60%有机肥+40%化肥和无肥)双季稻田土壤微生物生物量碳、氮和微生物熵的差异。结果表明,早稻和晚稻各主要生育时期,长期施肥均能提高土壤微生物生物量碳、氮含量和微生物熵,各施肥处理土壤微生物生物量碳、氮含量和微生物熵均随水稻生育期推进呈先增加后降低的变化趋势,均于齐穗期达到最大值,成熟期达到最低值;其中,以60%有机肥和30%有机肥处理双季稻田土壤微生物生物量碳、氮含量和微生物熵均为最高,均显著高于其他处理,其大小顺序表现为60%有机肥30%有机肥秸秆还田化肥无肥。长期有机无机配施可以提高土壤微生物生物量碳、氮和微生物熵,有机肥与化肥配施对提高土壤肥力效果最好。土壤微生物生物量碳、氮及微生物熵可以反映土壤质量的变化,可作为评价土壤肥力的生物学指标。     

A comparative account of the microbiological characteristics of soils under natural forest,grassland and cropfield from Eastern India

Microbiological and physico-chemical characteristics of tropical forest, grassland and cropfield soils from India were investigated. The study revealed that the conversion of natural forest led to a reduction of soil organic C (26–36%), total N (26–35%), total P (33–44%), microfungal biomass (44–66%) and total microbial biomass C, N and P (25–60%) over a period of 30–50 years. Comparative analysis of microbial activity in terms of basal soil respiration revealed maximum activity in the forest and minimum in the cropfield soil. Analysis of microbial metabolic respiratory activity (qCO₂) indicated relatively greater respiratory loss of CO₂-C per unit microbial biomass in cropfield and grassland than in forest soil. Considering the importance of the microbial component in soil, we conclude that the conversion of the tropical forest to different land uses leads to the loss of biological stability of the soil.