模拟氮沉降对木荷人工幼林地土壤氮素、碳素和微生物量垂直分布的影响

以NH4NO3作为氮源,对广州东北郊木荷（Schima superba）人工幼林地进行模拟氮沉降处理,共设置3个氮沉降水平,分别为N0（N：0 g·m-2·a-1）、N5（N：5 g·m-2·a-1）以及N10（N：10 g·m-2·a-1）,每月进行喷施。在连续施氮22个月（当月当次施氮5天后）对土壤氮素（硝氮、氨氮、总氮）、碳素（总碳）以及微生物量（脂磷）在0~60 cm土层中的垂直分布进行研究。结果显示：在3个氮沉降水平下,随着土层加深,pH呈现出下降的趋势,氮沉降存在加剧土壤酸化的风险;在N0、N5、N10水平下,土壤全氮和总碳的垂直分布趋势大体一致,随着土层加深,其含量下降,但在深层土壤（40~60 cm）中,施氮与对照比较,总碳呈现一定的增加趋势;除40~50 cm土层,N5、N10水平下的硝态氮含量在各个深度土壤中都表现为比对照组要高,氮沉降导致土壤一定程度上硝态氮的积累;在浅层土壤（0~20 cm）中,铵态氮水平较低并且其含量明显低于对照组,而在较深的土层中铵态氮有较多的积累,说明存在污染地下水的风险;N5和N10水平下,无机氮比例（无机氮含量与总氮含量之比）在各个深度土壤中总体高于N0水平;用脂磷含量表征土壤微生物含量,结果表明外加氮源对微生物含量有显著性影响,在N5、N10水平下,微生物含量在30~40 cm土层中出现峰值。     

模拟大气氮沉降对不同树种土壤微生物生物量的影响

土壤微生物是土壤生态系统的重要组成成分,又是土壤肥力的重要评价指标之一,在生态系统物质循环和能量流动中起着重要作用。氮沉降影响土壤微生物生长和繁殖,使其结构和功能发生改变,从而影响土壤物质循环和能量流动。通过室内模拟自然氮沉降,运用磷脂脂肪酸技术,研究氮沉降对不同树种(荷木Schima superba、马尾松Pinus massoniana、马占相思Acacia mangium、海南红豆Ormosia pinnata)土壤微生物的影响。结果表明:自然氮沉降条件下,细菌是土壤微生物的主要类群,占土壤微生物总量的40%以上。采样时间和树种均对总土壤微生物生物量、细菌生物量有显著影响。同一树种10月土壤微生物生物量(总土壤微生物、细菌、真菌、放线菌)高于4月。4月土壤微生物生物量马占相思最高(总土壤微生物生物量76.78 nmol·g-1、细菌生物量33.94 nmol·g-1、真菌生物量6.91 nmol·g-1、放线菌生物量8.38 nmol·g-1),荷木最低(总土壤微生物生物量57.89 nmol·g-1、细菌生物量24.79 nmol·g-1、真菌生物量4.16 nmol·g-1、放线菌生物量5.57 nmol·g-1);10月海南红豆最高(总土壤微生物生物量92.67 nmol·g-1、细菌生物量38.85 nmol·g-1、真菌生物量8.09 nmol·g-1、放线菌生物量9.27 nmol·g-1),荷木最低(总土壤微生物生物量71.10 nmol·g-1、细菌生物量30.79 nmol·g-1、真菌生物量4.90 nmol·g-1、放线菌生物量7.04 nmol·g-1)。采样时间和树种的交互作用对放线菌生物量有显著影响。总土壤微生物生物量与铵态氮显著正相关,而真菌生物量与土壤有机质显著正相关。结果对全球变化条件下生态系统健康管理具有重要意义。     

凋落物质量和分解对中亚热带栲木荷林土壤氮矿化的影响

用控温、控水室内培养方法,研究了中亚热带栲木荷常绿阔叶林和邻近柳杉人工针叶林凋落物的分解及其对栲木荷林土壤氮矿化的影响.结果表明:栲木荷阔叶林的凋落物失重率大于针阔混合凋落物的失重率,大于柳杉针叶纯林凋落物的失重率.所有凋落物失重率都与其初始氮含量呈显著负相关,和初始碳含量呈显著正相关,而与凋落物C/N比的相关性不强.不同凋落物处理下的土壤NO3--N含量差异显著(P＜0.05,N=18),NH4 -N含量差异不显著(P＞0.05,N=18),混合凋落物处理下的土壤NO3--N和NH4 -N含量最高,分别是224.21 mg kg-1和56.77 mg kg-1,其氮转化速率也最高,硝化、氨化、氮矿化速率分别为1.74 mg kg-1 d-1、0.36 mg kg-1 d-1和1.90mg kg-1 d-1.各凋落物处理下的土壤氮含量随时间变化的规律不一致.土壤氨化速率与土壤全氮呈显著正相关(r=0.843,P＜0.05,N=21),与栲木荷林凋落物的失重率呈显著负相关(r=-0.997,P＜0.05,N=21).图3表4参29     

氮沉降增加对贝加尔针茅草原土壤微生物群落结构的影响

土壤微生物是草原土壤生态系统的重要组成部分。为研究氮沉降增加对草原土壤微生物群落结构的影响,以内蒙古贝加尔针茅草原为研究对象,开展连续6年(2010—2015年)模拟氮沉降试验,以N计算,设置:N0(0 kg·hm~(-2))、N50(50kg·hm~(-2))、N100(100 kg·hm~(-2))、N150(150 kg·hm~(-2))和N300(300 kg·hm~(-2))5个处理,采用磷脂脂肪酸(PLFA)技术测定0~10 cm土壤特征微生物PLFA生物标记数量并探讨土壤微生物群落结构对氮沉降的响应。结果表明:随氮添加量增大,土壤微生物总PLFAs、细菌PLFAs、革兰氏阳性细菌PLFAs、革兰氏阴性细菌PLFAs和放线菌PLFAs含量呈先升高后降低的趋势,均以N100(100 kg·hm~(-2))处理最高。土壤微生物群落PLFA标记的主成分分析显示,不同氮添加下土壤微生物PLFA标记有显著差异。相关分析表明,土壤革兰氏阳性菌、放线菌PLFA含量、G~+/G~-与土壤p H值呈显著负相关,土壤微生物总PLFAs、土壤细菌PLFAs、革兰氏阳性菌PLFAs、革兰氏阴性菌PLFAs、放线菌PLFAs和饱和脂肪酸PLFAs含量均与土壤速效磷含量呈显著正相关。综合研究表明,连续6年氮添加改变了贝加尔针茅草原土壤微生物群落结构,土壤p H值和土壤速效磷含量是驱动这种变化的主要因素。     

施氮水平对河套灌区套作小麦-玉米土壤微生物量碳、氮的影响研究

通过田间试验研究了河套灌区套作小麦(Triticum aestivum L.)-玉米(Zea mays L.)在不同施氮水平下(小麦N0 0 kg·hm~(-2)、N1 90 kg·hm~(-2)、N2 180 kg·hm~(-2)、N3 270 kg·hm~(-2);玉米N0 0 kg·hm~(-2)、N1 135 kg·hm~(-2)、N2 270 kg·hm~(-2)、N3 405 kg·hm~(-2))土壤微生物量碳、氮的变化规律,为农业生产中定量施氮提供有益的生物参数和指标。结果表明:小麦全生育期内土壤微生物量氮、碳含量呈现出"升-降-升"趋势,抽穗期土壤微生物量氮达到最大值,灌浆期的下降幅度最大,土壤中的养分被小麦大量吸收消耗,此时微生物矿化出一部分微生物量氮以供作物吸收利用,土壤微生物量含量大幅下降。玉米土壤微生物量氮、碳含量随生育期进程推进而先增加后降低,在抽雄期出现峰值,土壤中的有效养分充足,同时,根系代谢活动旺盛,分泌物增多,使微生物代谢加快,为微生物的生长和繁殖提供了充足的营养环境。套作小麦-玉米土壤微生物量碳、氮含量均随着施氮水平的升高呈现出先增加后降低的趋势,在N2(小麦180 kg·hm~(-2)、玉米270 kg·hm~(-2))水平下,土壤微生物量碳、氮含量最高。N2处理的小麦微生物量碳较N0增加了53.7%,微生物量氮则是N0的3.29倍;N2处理的玉米微生物量碳、氮分别是N0的2.61、5.38倍。回归分析表明,土壤微生物量与施氮量之间表现为显著的二次型回归关系,适宜的氮肥施用量对微生物量碳、氮的负效应较低;根据边际分析及综合土壤微生物量碳、氮,推荐小麦最佳施肥量为165.9~187.5 kg·hm~(-2),玉米最佳施肥量为227.5~287.9 kg·hm~(-2)。     

多形态多水平氮添加对温带森林土壤根系呼吸和微生物呼吸的影响

为阐明不同水平、不同形态的氮添加对土壤总呼吸、土壤微生物呼吸、根系呼吸的影响及微生物机制,本研究以温带森林土壤为研究对象,开展多形态(硝态氮(NaNO_3)、铵态氮((NH_4)_2SO_4)和混合态氮(NH_4NO_3))多水平(50 kg N·ha~(-1)·a~(-1)和150 kg N·ha~(-1)·a~(-1))的增氮控制实验.在施氮后的第7—9年,利用静态箱-气相色谱法研究土壤呼吸组分和磷脂脂肪酸方法研究微生物群落丰度和群落结构的改变.结果表明,氮添加显著提高了土壤硝态氮和铵态氮含量,而土壤pH平均降低0.85个单位.在施氮后的第7—9年,氮添加将会减弱土壤呼吸活动,高水平的氮添加效应强于低水平氮添加;就形态来说,(NH_4)_2SO_4起到促进效应,而NH_4NO_3则逐渐由促进效应转变成抑制效应,例如在2019年(施肥后第9年),高水平的(NH_4)_2SO_4施加分别提高土壤总呼吸和微生物呼吸的34.06%和37.95%,而高水平NH_4NO_3添加则分别抑制了土壤总呼吸和微生物呼吸的27.62%和31.70%.而高水平的(NH_4)_2SO_4添加对根系呼吸有促进作用,而高水平的NH_4NO_3则有抑制效应.微生物呼吸和细菌、真菌显著正相关,和真菌/细菌比值也呈正相关.总之,土壤呼吸各组分对氮添加的响应受氮素形态和水平的控制,特定森林土壤碳排放量对土壤氮基质响应具有多阶段性,微生物呼吸的降低反映了土壤有机质分解速度的降低,这有可能会进而促进土壤碳的积累,达到氮促碳汇的效果.     

10年氮添加未显著影响苦竹林土壤磷组分

土壤磷(P)的可利用性是影响植物生长发育的重要因素。以研究氮(N)添加对土壤P组分的影响为切入点,探讨长期N沉降增加对竹林生态系统中土壤P素可利用性及P循环的影响,对预测该区域大气N沉降持续增加背景下人工竹林系统P素状态的变化具有重要意义。于2007年10月在苦竹(Pleioblastus amarus)林中建立模拟N沉降试验样地,设置对照(CK,0g·m~(-2)·a~(-1))、低N(LN,5g·m~(-2)·a~(-1))、中N(MN,15g·m~(-2)·a~(-1))和高N(HN,30g·m~(-2)·a~(-1))4个处理,每个处理设置3个重复。从2007年10月—2017年10月,每月下旬进行N添加处理。在连续N添加处理10a后,于2017年4月采集0~10cm土壤样品并测定土壤P组分、土壤微生物生物量P含量、土壤酸性磷酸酶活性及土壤pH。结果表明:该苦竹林土壤总P质量分数为0.64mg·g~(-1),其中残渣P约占77.0%,有机P占15.0%,无机P占8.0%。CK处理下,碳酸氢钠和氢氧化钠提取的无机P组分(NaHCO3-Pi和NaOH-Pi)质量分数分别为0.26mg·kg~(-1)和4.26mg·kg~(-1),N处理分别使其增加了100.0%~157.7%和43.2%~70.0%,但未达到统计学显著水平(P0.05)。另外,N添加处理未显著影响土壤pH、土壤酸性磷酸酶活性和土壤微生物生物量P(P0.05)。研究结果表明,长期N添加未显著影响苦竹林土壤酸性磷酸酶活性、土壤总P含量以及各个P组分的分配(P0.05),这说明长期N添加未显著影响土壤P素可利用性。在未来一段时间内,该林分的P素循环可能不会受到大气N沉降增加的强烈影响。     

三相鼓泡塔生物反应器培养黄孢原毛平革菌合成木素过氧化物酶系

利用三相鼓泡塔反应器固定化培养黄孢原毛平革菌，可以高效地合成木素过氧化物酶系，固定化载体为聚氨酯泡沫塑料．实验表明，合成木素过氧化物酶和锰过氧化物酶的最佳通气量均是1．0vvm。在此通气量下，最大木素过氧化物酶的酶活达367U/L，最大锰过氧化物酶的酶活达4．72U／mL。在使用相同的培养基和固定化载体单位体积用量条件下，与摇瓶培养相比，酶活分别增大1倍和1．2倍．一定条件下，在三相鼓泡塔中可以进行重复间歇培养生产木素过氧化物酶，连续进行了5批培养，每批最大木素过氧化物酶的活力均在250U／L以上，最高酶活出现在第二批为480U／L，总培养时间达22d．图9参15     

亚热带常绿阔叶林土壤微生物量动态变化及其对氮磷添加的响应

土壤微生物是土壤生物化学过程的驱动者,对环境变化极其敏感。为了探讨不同年份气候差异及不同坡位土壤微生物对氮沉降的响应机制,在安徽南部查湾自然保护区选择不同坡位亚热带常绿阔叶林,就氮、磷添加对土壤微生物量碳(MBC)、氮(MBN)的影响进行了为期3年的试验研究。选择中坡和坡顶两种立地类型,分别设置3种控制实验,对照(CK,0 kg N?hm~(-2)?a~(-1))、氮添加(N,100 kg N?hm~(-2)?a~(-1))、氮磷添加(N+P,100 kg N?hm~(-2)?a~(-1)+50 kg P?hm~(-2)?a~(-1))。取样后,测试不同处理土壤MBC、MBN及土壤理化性质。结果表明,氮磷添加后,不同坡位MBC和MBN季节变化存在差异。与対照相比,氮磷和氮添加中坡MBC分别降低了14.6%和15.4%,而在坡顶,两种处理MBC分别提高5.8%和2.1%。中坡MBC变化范围为171.94~2 151.35 mg?kg~(-1),MBN变化范围为52.14~203.3 mg?kg~(-1);坡顶MBC变化范围为102.49~2 219.95 mg?kg~(-1),MBN变化范围为38.56~203.3 mg?kg~(-1)。中坡第2年、第3年及坡顶第3年氮磷和氮添加降低了ω(MBC)/ω(MBN)比,不同坡位ω(MBC)/ω(MBN)比均值为7.88~14.21。土壤微生物量的季节变化显著,土壤MBN在生长季节(5月、7月、9月及11月)较高,最低值出现在休眠期(1月);养分添加改变了土壤MBN季节变化规律。季节、坡位改变了土壤微生物量碳氮和土壤养分的相关性。因此,养分添加对不同立地土壤微生物的影响不同,且不同年份存在差异。长期氮、磷添加降低了ω(MBC)/ω(MBN)比值,但不同坡位反应时间存在差异。土壤MBC、MBN不同年份之间差异显著,主要受不同年份降雨和气温变化控制。冗余分析(RDA)表明,月降水频率、不同年份气温及降水差异、林分因子及土壤理化性质均对土壤微生物量存在显著影响,其季节变化由降水频率(月降水天数)、降水量及气温变化和月降水量及气温波动差异(月标准差)所控制。     

模拟氮沉降对武夷山亚热带常绿阔叶林土壤呼吸的影响

大气氮沉降是全球变化的焦点问题之一,为研究大气氮沉降对森林生态系统土壤呼吸的影响,在武夷山亚热带常绿阔叶林进行人工模拟氮沉降,设置对照(N0,0 kg·hm~(-2)·a~(-1))、低氮(N1,50 kg·hm~(-2)·a~(-1))、中氮(N2,100 kg·hm~(-2)·a~(-1))和高氮(N3,150 kg·hm~(-2)·a~(-1)),采用Li-6400分析系统测定土壤呼吸速率,同时测定土壤温度和土壤含水量,探讨氮沉降的背景下土壤温度和土壤含水量与土壤呼吸的关系。结果表明,(1)亚热带常绿阔叶林土壤呼吸速率具有明显的季节动态变化,土壤呼吸速率均为1月最低,8月最高。(2)常绿阔叶林土壤总呼吸存在明显的季节格局,总体呈单峰型,其峰值均出现在8月,重复测量方差分析结果显示,在生长季,氮沉降对土壤总呼吸均无显著影响(P0.05)。(3)常绿阔叶林土壤总呼吸与土壤温度呈显著的指数关系,其响应具体表现在,低高氮(N1,N3)处理和中氮(N2)处理在一定程度上分别提高和降低了土壤呼吸Q_(10)。N0、N1、N2、N3处理下土壤总呼吸的Q_(10)分别为1.52、1.57、1.44、1.56;土壤呼吸速率与0~5 cm和5~10 cm土层土壤含水量之间的关系用二次曲线拟合的效果最好,其决定系数R~2分别为0.156~0.354和0.239~0.387,明显低于土壤呼吸速率与土壤温度关系方程的R~2值,这表明土壤呼吸速率与土壤含水量之间的相关性较弱,由此可知土壤含水量对土壤呼吸的影响远小于土壤温度对土壤呼吸的影响。(4)N0、N1、N2和N3处理的土壤总呼吸年碳排放量分别为5.67、5.98、6.22和4.22 t·hm~(-2)·a~(-1),低氮和中氮处理的排放比对照高出5.46%和9.70%,低氮促进了土壤呼吸年通量,而高氮抑制了土壤呼吸年通量;方差分析结果表明,氮沉降对土壤呼吸、异养呼吸年通量有显著影响,其中N2对土壤呼吸、异养呼吸年通量影响最大(P0.05)。     

Variation in soil organic carbon mineralization and microbial community structure induced by the conversion from double rice fields to drained fields北大核心CSCD

Land use conversion is an important factor influencing the carbon gas exchange between land and atmosphere. The effect of land use conversion on soil organic carbon mineralization and microbial function is important for soil organic carbon sequestration and stability. This research studied the effects of land use conversion on soil chemical properties, organic carbon mineralization and microbial community structure after two years of conversion from double rice cropping (RR) to maize-maize (MM) and soybean-peanut (SP) double cropping systems in southern China. The results showed that soil pH significantly decreased by 0.50 (MM) and 0.52 (SP, P = 0.002), and dissolved organic carbon significantly increased by 23%- 35% (P = 0.016). No significant difference was found in soil organic carbon mineralization rate with the land use conversion, though the accumulated mineralization decreased after 13 days of incubation (P = 0.019). Land use conversion from paddy to upland significantly changed soil microbial community structure. The total PLFAs, bacterial, gram-positive bacterial (G+), gram-negative bacterial (G-) and actinomycetic PLFAs decreased significantly (P < 0.05), the ratio of fungal PLFAs to bacterial PLFAs (F/B) increased significantly (P = 0.006). But no significant differences in microbial groups were found between MM and SP. The accumulated mineralization at the beginning period of the incubation were significantly positively correlated with soil actinomycetic PLFAs (P = 0.034). After 13 days of incubation, soil F/B showed a positive correlation with the accumulated mineralization (P = 0.004). However, soil microbial community structure(P = 0.014)and total PLFAs(P = 0.033)showed a positive correlation with the accumulated mineralization after 108 days of incubation. Our results indicated that after conversion from paddy soils to drained soils, soil pH and total nitrogen are the key factors regulating the variations in soil microbial community structure and biomass, and then influencing soil organic carbon mineralization.     

有机碳源物对淹水土壤中氮素转化的影响

八周淹水培养试验表明：木质素对土壤矿质氮影响不大，纤维素则影响强烈，而淀粉的影响比纤维素更为强烈持久．硫铵与纤维素或淀粉配施时，氮的固持作用大于矿化作用，在培养期间均没有释放出氮素．在八周时间内．氨基酸态氮趋向增加，表明是微生物对氮素的固持作用；氨基糖态氮占全氮比例很低而且变化不大；其它有机组分氮在短期内的变化没有明显的规律性．     

Effect of clay minerals on extractability of heavy metals and sewage sludge mineralization in soil

An incubation experiment lasting 111 d was carried out to study the effect of the addition of three clay minerals (Na-bentonite, Ca-bentonite, and zeolite) to soil derived from sewage sludge on water-extractable and exchangeable forms of four heavy metals (Zn, Cd, Cu, and Ni), as well as on soil organic matter mineralization, microbial biomass C and the release of inorganic N. The addition of clay minerals led to a significant decrease in water-extractable and exchangeable forms of heavy metals. The extent of decrease ranged from 14 to 75% for the water-extractable heavy metals and from 12 to 42% for the exchangeable form over the incubation time, as compared with untreated soil. The reduction in extractability of heavy metals was greater due to the addition of Na-bentonite and Ca-bentonite than that due to the addition of zeolite. Addition of clay minerals did not affect any of the following microbiological parameters in the soil: microbial biomass C, organic C (C_org) mineralization, and metabolic quotient (qCO₂), and release of inorganic N during the first 3 weeks of incubation. However, as the incubation period increased, these parameters were significantly increased by the addition of clay minerals, especially by the addition of Na-bentonite and Ca-bentonite. This result is explained by a strong reduction in extractability of heavy metals after the addition of Na-bentonite and Ca-bentonite.     

Plants control the seasonal dynamics of microbial N cycling in a beech forest soil by belowground C allocation

Soil microbes in temperate forest ecosystems are able to cycle several hundreds of kilograms of N per hectare per year and are therefore of paramount importance for N retention. Belowground C allocation by trees is an important driver of seasonal microbial dynamics and may thus directly affect N transformation processes over the course of the year. Our study aimed at unraveling plant controls on soil N cycling in a temperate beech forest at a high temporal resolution over a time period of two years, by investigating the effects of tree girdling on microbial N turnover. In both years of the experiment, we discovered (1) a summer N mineralization phase (between July and August) and (2) a winter N immobilization phase (November-February). The summer mineralization phase was characterized by a high N mineralization activity, low microbial N uptake, and a subsequent high N availability in the soil. During the autumn/winter N immobilization phase, gross N mineralization rates were low, and microbial N uptake exceeded microbial N mineralization, which led to high levels of N in the microbial biomass and low N availability in the soil. The observed immobilization phase during the winter may play a crucial role for ecosystem functioning, since it could protect dissolved N that is produced by autumn litter degradation from being lost from the ecosystem during the phase when plants are mostly inactive. The difference between microbial biomass N levels in winter and spring equals 38 kg N/ha and may thus account for almost one-third of the annual plant N demand. Tree girdling strongly affected annual N cycling: the winter N immobilization phase disappeared in girdled plots (microbial N uptake and microbial biomass N were significantly reduced, while the amount of available N in the soil solution was enhanced). This was correlated to a reduced fungal abundance in autumn in girdled plots. By releasing recently fixed photosynthates to the soil, plants may thus actively control the annual microbial N cycle. Tree belowground C allocation increases N accumulation in microorganisms during the winter which may ultimately feed back on plant N availability in the following growing season.     

Soil microbial population and enzyme activity related to grazing pressure in alpine meadows of Nanda Devi Biosphere Reserve

The present study aims to analyze the interaction of prevailing biotic pressure on soil environment with emphasis on its physicochemical and microbiological characteristics determining soil fertility status and thus supporting plant and animal biodiversity in Nanda Devi Biosphere Reserve (NDBR) which is located in northern part of Uttaranchal hills between 79 degrees 40'E to 80 degrees 05'E longitude and 30 degrees 17'N to 30 degrees 41'E latitude. The experimental results revealed that the physico-chemical characteristics (viz., moisture, pH, EC, C, N, P, K, CEC) of soil were maximum in moderately grazed meadow and minimum in intensively grazed meadow. Soil microbial analysis measured in terms of total viable count (TVC) exhibited grazing sensitivity trend being maximum population of bacteria > fungi > actinomycetes. The soil microbial population was positively correlated with soil respiration, dehydrogenase activity, acid phosphatase and microbial biomass, which exhibited uneven trend with grazing pressure. Soil from moderately grazed meadow showed highest microbial count and enzyme activities, whilst intensively grazed meadow showed lowest microbial count and enzyme activities. This depicts the beneficial role of prescribed grazing up to limited extent in management of soil fertility, which might have supported luxuriant growth of a variety of grasses.     

植物群落对铜尾矿废弃地土壤微生物量和酶活性的影响

以铜尾矿废弃地为对象,研究了铜尾矿废弃地上植物群落发展与表层尾矿微生物量C、N和脱氢酶、过氧化氢碱性磷酸酶和脲酶活性的变化,探讨了植物群落-微生物量C、N_土壤酶活性之间的相互关系.结果表明,随着植物群落的发展,铜尾矿废弃地表层尾矿微生物量和酶活性在不断增加;铜官山老尾矿废弃地白茅群落下表层尾矿(TBM)微生物量和酶活性与杨山冲尾矿废弃地及铜官山新尾矿废弃地表层尾矿微生物量和酶活性存在显著差异性(p<0.05).相关分析表明铜尾矿废弃地表层尾矿微生物量C、N与土壤有机质、总氮之间呈显著正相关(P<0.01);脱氧酶、碱性磷酸酶及脲酶与微生物量C、微生物量N、土壤有机质、总氮之问呈显著正相关(P<0.01),但过氧化氢酶与微生物量C、微生物量N、土壤有机质、总氮之间呈显著负相关(P<0.01).     

4种农药对土壤微生物的影响Ⅱ:氮素矿质化的变化

研究农药,氯氰菊酯、高效氯氰菊酯、多菌灵和丁硫克百威对山西省两种土壤氮素矿质化（ 氨化作用和硝化作用） 的影响．结果表明,添加低浓度（ ｗ ＝ １００ ｍｇ／ｋｇ） 的４ 种农药,对土壤氮素矿质化无显著影响． 高浓度（ ｗ ＝ １０００ ｍｇ／ｋｇ） 的菊酯类农药会抑制土壤中硝化细菌的活动,使土壤中氨的含量明显积累;添加高浓度多菌灵的土壤样品出现硝态氮积累的现象,这可能与其对微生物生长影响有关;添加高浓度丁硫克百威在一种土壤样品中使氨的含量有明显积累,但在另一种土壤样品中与对照基本相同．可见,农药对土壤氮素矿质化及微生物活性的影响,因农药品种的不同和浓度的不同而异,不同的土壤因微生物活性的差异而对农药污染的反应也不同     

蚯蚓和堆肥固定化添加模式对漆酶降解土壤五氯酚的影响

利用土壤五氯酚（PCP）污染模拟实验,研究两种不同生态型蚯蚓（赤子爱胜蚓Eisenia foetida和壮尾环毛蚓Amynthas robustus E.Perrie）和堆肥固定化添加模式对漆酶降解土壤PCP的影响。在42 d培养期内,测试了不同处理下PCP质量分数、漆酶活性,以及土壤呼吸和微生物碳氮等微生物指标。结果表明：堆肥固定化漆酶降解土壤PCP的效果优于壳聚糖固定化漆酶和自由漆酶,主要原因是堆肥固定化漆酶能够有效地提高漆酶稳定性,减缓其活性下降速度。此外,堆肥还能提高土壤微生物的数量与活性,显著提升土壤漆酶的活性。添加两种生态型蚯蚓对漆酶活性影响不显著,但均可以显著提高土壤微生物的数量与活性,加速土壤中PCP的降解。壮尾环毛蚓对土壤微生物数量与活性的提升效果优于赤子爱胜蚓。     

Interactions among lignin, cellulose, and nitrogen drive litter chemistry-decay relationships

Litter decay rates often correlate with the initial ratios of lignin:nitrogen (N) or lignin:cellulose in litter. However, the chemical and microbial mechanisms that give rise to these patterns are still unclear. To identify these mechanisms, we studied the decomposition of a model plant system, Arabidopsis thaliana, in which plants were manipulated to have low levels of lignin, cellulose, or litter N. Nitrogen fertilizer often increases the loss of cellulose, but it suppresses the breakdown of lignin in plant litter. To understand the mechanisms driving these patterns, we decomposed plants in litterbags for one year in control and N-fertilized plots in an Alaskan boreal forest. We found that litter N had a positive effect on total mass loss because it increased the loss of lignin, N, and soluble C. Lignin had a negative effect on rates of total litter mass loss due to decreases in the loss of cellulose and hemicellulose. Cellulose had a positive effect on lignin loss, supporting the concept of a "priming effect" for lignin breakdown. However, the low-cellulose plants also lost more of their original cellulose compared to the other plant types, indicating that decomposers mined the litter for cellulose despite the presence of lignin. Low-lignin litter had higher fungal biomass and N-acetyl glucosaminidase (NAG, a chitinase) activity, suggesting that lignin restricted fungal growth and may have influenced competitive interactions between decomposers. Nitrogen fertilization increased NAG activity in the early stages of decay. In the later stages, N fertilization led to increased cellulase activity on the litters and tended to reduce lignin losses. The transition over time from competition among decomposers to high cellulase activity and suppressed lignin loss under N fertilization suggests that, in N-limited systems, N fertilization may alter decomposer community structure by favoring a shift toward cellulose- and mineral-N users.     

Impact of nitrogen fertilizer source on nitrous oxide (N2O) emissions from three different agricultural soils during freezing conditions

ABSTRACT

Nitrogen (N) application is the main agricultural management that increases nitrous oxide (N₂O) concentration in the atmosphere. Freezing conditions are common phenomenon in the northern China that significantly affect soil N₂O emissions through alterations in nutrients availability and microbial population. To develop a comprehensive understanding of how N fertilizer managements affect soil N₂O emissions during the freezing process, a lab incubation was conducted in three typical cultivated soils (black soil, fluvo-aquic soil, or loess soil) by adding different N fertilizer sources, including ammonium chloride, sodium nitrate, or urea at different N levels (0, 80, 200, or 500 mg N/kg) at the start of freezing. The N₂O emissions in the fluvo-aquic soil were significantly higher than in other soils. The application of nitrate in the fluvo-aquic soil promoted N₂O emissions by five- and seven-fold higher compared to ammonium chloride and urea, whereas N₂O emissions in black soil were enhanced by application of ammonium chloride. Data indicate that denitrification is the major pathway for N₂O production in the fluvo-aquic soil during the freezing process, while ammonia oxidation responses accounts for elevated N₂O production in black soil. No significant influence of N fertilizer levels on N₂O emissions were found during soil freezing. These results suggest that agricultural practices that focus on mitigation of N₂O emissions need to avoid selection of nitrate as N fertilizer source in fluvo-aquic soil prior to the freezing season. Future studies need to focus on how the expression of enzymes and/or shifts in microbial communities respond to different N fertilizers during freezing conditions.