多环芳烃长期污染土壤的微生物强化修复初步研究

本研究通过室内模拟试验,以急性毒性较强的菲(Phe)和遗传毒性较强的苯并[a]芘(B[a]P)为代表性多环芳烃(PAHs)污染物,以不同C源、通气状况和水分条件为调控因子,对PAHs长期污染土壤的土著微生物强化修复进行初步研究。结果表明,搅动处理使污染土壤中Phe和B[a]P的降解率分别达59.44%和26.14%,而淹水处理使两者降解率分别达46.48%和13.27%。添加C源(淀粉和葡萄糖)处理提高了土壤中PAHs的降解率,且随着C源的施用量而增加。同时也发现污染土壤中PAHs降解菌和微生物总量呈正相关,并随着PAHs降解菌数量的增加,土壤中PAHs降解率也随之提高。可见,土壤中PAHs降解速率主要决定于PAHs的降解菌数量。     

生物表面活性剂强化微生物修复多环芳烃污染土壤的初探

通过温室盆栽实验,单独或联合接种多环芳烃专性降解菌(DB)和添加生物表面活性剂-鼠李糖脂(RH),研究了生物表面活性剂强化微生物修复多环芳烃(PAHs)长期污染土壤的效果。结果表明,添加RH和接种DB能明显促进土壤中PAHs总量和各组分PAHs的降解。经过90 d培养后,添加RH、DB和RH+DB处理的PAHs的降解率分别为21.3%、32.6%、36.0%,较对照分别提高了333.0%、563.3%、633.0%。此外,随着苯环数的增加,土壤中15种PAHs平均降解率逐渐降低。同时也发现DB、RH+DB处理土壤中脱氢酶活性、多酚氧化酶活性和PAHs降解菌数量显著高于CK、RH处理,但是CK与RH处理没有显著差异,说明DB、RH在促进土壤中PAHs的降解方面有不同的机制。     

干热河谷土壤酶活性和车轴草生长对氮磷添加的响应

为了探讨干热河谷地区不同土地利用类型下土壤酶活性和植物生长对氮磷添加的响应以及二者之间的联系,采集了元谋干热河谷6种不同土地利用类型土壤,包括灌丛、草地、森林、新开垦农田(新农)、常年耕作农田(常农)、侵蚀裸地(裸地),并利用盆栽探索了土壤酶活性和车轴草(Trifolium repens L.)生长对氮(N)、磷(P)、氮磷(N+P)处理的响应特征。结果表明:(1)植物生物量受土地利用类型和处理双重因素影响,两者的交互作用对植物生物量具有显著作用。(2)除农田土壤(新农和常农)外,其他土地利用类型的土壤上植物生长受到养分添加的显著影响,其中添加P处理的生物量显著高于对照; 而N+P处理又显著高于单一的P添加; 而新农和常农不同养分处理间植物生物量差异不显著。(3)土壤酶活性受土地利用类型显著影响,但是不同养分添加处理之间土壤酶活性差异不显著; 土壤酶活性与植物生物量无显著相关性。综上,干热河谷土壤中植物生长的限制养分主要为磷,然而土壤酶活性则不受氮磷养分的限制,其活性主要与土地利用类型有关。     

生态系统生境改变对土壤微生物群落结构的影响

【目的】森林和农田生态系统的土壤有机碳和微生物群落结构存在显著差异,为了预测生态系统对不断变化的环境条件的瞬时响应,需明确土壤微生物群落结构对生境气候变化的响应。【方法】在我国北方地区同一纬度的森林和农田生态系统中设置土柱置换试验,对生物标识物磷脂脂肪酸和土壤因子进行分析,探究土柱置换两年后土壤微生物群落结构对生境改变的响应并明确影响微生物群落结构的主要土壤因子。【结果】(1)森林土壤置换到农田生境后,上层土壤微生物生物量显著降低（P <0.05）。其中总微生物生物量下降了28.2%,细菌生物量下降了27.9%,真菌生物量下降了44.1%,革兰氏阴性菌生物量下降了39.6%,革兰氏阳性菌生物量下降了18.8%,放线菌生物量下降了19.8%;置换的下层土壤中仅革兰氏阴性菌生物量显著降低（P <0.05）。(2)农田土壤置换到森林生境后,上层土壤各类群微生物生物量呈增加趋势,但差异不显著;而下层放线菌生物量和总微生物生物量显著下降（P <0.05）。(3)土壤微生物群落结构变化均与土壤因子显著相关,其中土壤含水率对微生物群落结构变化的贡献率可占到27.5%～50.9%。【...     

混合菌群强化去除泥浆体系中菲、芘的效果及影响因素

通过室内泥浆体系模拟试验,研究了混合微生物菌群(嗜热菌和多环芳烃特异性降解菌),在40℃条件下(两类微生物均能较快生长繁殖),对泥浆体系中代表性多环芳烃菲、芘的去除效果及其影响因素(水土比,葡萄糖、淀粉、水杨酸及其浓度)。结果表明:泥浆体系中混合微生物菌群对多环芳烃的去除效果显著(P0.01),单日菲去除率最大可达20.0%,芘达15.3%。随着反应进程的进行,菲和芘的去除率提高,去除速率则逐步降低,菲的半衰期1.8天小于芘4.9天,因此菲的去除较芘更快。试验得到该泥浆体系中混合微生物菌群去除多环芳烃最合适的水土比为2︰1,碳源为葡萄糖,浓度TOC_(葡萄糖):TOC_(PAHs)为2︰1。该研究结果可为泥浆体系中混合微生物菌群强化修复多环芳烃污染土壤的技术研发提供理论基础和技术支撑。     

木质素与蚯蚓对黑麦草生物量及土壤微生物群落的影响

采集农田土壤,设置添加木质素和蚯蚓不同组合处理的黑麦草盆栽试验,在测定植物生物量的基础上,结合定量PCR、高通量测序等方法,研究木质素和蚯蚓及其联合作用对土壤细菌、真菌群落的影响。结果显示:木质素显著降低了黑麦草的生物量,而蚯蚓能够缓解木质素的抑制作用,促进黑麦草生长。木质素明显抑制了土壤细菌、真菌数量,并改变群落结构,以Sphingomonadaceae、Methylophilaceae为标志的降解细菌和担子菌等潜在降解真菌显著富集;单一加入蚯蚓对土壤微生物的影响相对较小,木质素和蚯蚓组合处理显著提高细菌、真菌数量,改变上述降解微生物的丰度。这些结果表明,木质素降低土壤微生物数量,并可能通过其自身降解释放的酚类化感物质抑制植物生长,对土壤生态系统健康产生不利影响;蚯蚓与木质素联合处理影响土壤中木质素降解微生物组成,微生物数量与植物生物量均表现增加趋势,蚯蚓有利于土壤中木质素的微生物代谢,并为植物生长提供更多的养分。本研究为农田生态系统木质素资源化利用提供了科学依据。     

运用多隔层根箱研究玉米幼苗根际微域中芘的降解

采用多隔层根箱,通过尼龙撩网插片的控制,实现根室土(S0)、离根室0～2mm(S1)、2～4mm(S2)、4～6mm(S3)及6mm(S4)各室层土壤的分离采集,分析离根系表面不同距离土壤芘的根际降解,并借助脂肪酸甲酯(fattyacidmethylester,FAME)分析土壤微生物群落结构的空间响应机制。结果表明:种植玉米处理的各室层内土壤可提取态芘含量存在显著的不同,其大小顺序为S4S3S0S2S1;各室层微生物群落结构存在显著的变化,其中微生物生物量和丛枝菌根真菌特征脂肪酸含量表现出与土壤可提取态芘含量变化相反的变化趋势。未种植玉米处理的各室层土壤可提取态芘含量和微生物群落结构没有差异。土壤可提取态芘含量与微生物生物量和丛枝菌根真菌的特征脂肪酸呈显著负相关(p0.01)。     

生物质炭对盆栽黑麦草生长的影响及机理

通过盆栽试验,采用实时定量PCR和微孔板荧光法,分别研究了生物质炭添加对太湖地区农田土壤黑麦草生长、微生物群落丰度和酶活性的影响。结果表明:生物质炭添加量为4%(炭/土质量比)处理显著提高了土壤p H、有机碳、全氮、碳氮比、速效钾含量及黑麦草生物量;提高了土壤细菌、古菌和固氮菌nif H基因拷贝数,而对真菌无影响;提高了β-葡萄糖苷酶、纤维二糖水解酶、木糖苷酶、β-N-乙酰氨基葡萄糖苷酶和酸性磷酸酶的活性。微生物丰度(除真菌外)与多数土壤酶活性(除亮氨酸氨基肽酶)均成显著正相关。因此,生物质炭可增加土壤矿质养分,提高主要微生物类群和功能菌的丰度及土壤碳、氮和磷转化酶活性,这可能是施用生物质炭提升农田土壤养分转化功能和生产力的主要原因。     

环境条件对麻纤维地膜降解及其土壤微生物量和酶活性的影响

通过设置不同土壤pH、施氮量、季节和作物种植的土壤环境条件,采用盆栽埋袋试验方法研究麻纤维地膜的降解规律变化,并分析其与土壤微生物生物量及酶活性的关系。结果表明:麻纤维地膜的降解过程均服从Olson衰减模型(R~2=0.689～0.996,P0.05)。施氮量和使用季节对麻纤维地膜的降解产生显著影响,在秋冬季节施氮量增加和种植小白菜呈抑制地膜降解的趋势,夏季地膜降解速率显著高于秋冬季,但土壤pH(5.80～8.34)对地膜的降解速率影响较弱。不同土壤环境条件下,试验末期麻纤维地膜的降解率与土壤微生物生物量碳、氮(MBC、MBN)、纤维素酶及过氧化氢酶活性呈显著正相关关系(P0.05)。因此,土壤环境条件改变导致的土壤微生物生物量及酶活性变化可能是其影响麻纤维地膜降解速率的重要原因。     

长期石油污水灌溉对东北旱田土壤微生物生物量及土壤酶活性的影响

以土壤微生物生物量和土壤酶活性等为土壤微生物变化指标,研究了含油污水长期灌溉对东北沈抚灌区农田土壤微生物的影响.结果表明:土壤微生物生物量碳和生物量氮随着污灌有机物污染程度的增加而增加,与土壤石油烃(TPH)含量极显著正相关,相关系数分别为0.955和0.962(P<0.01);与土壤多环芳烃(PAHs)含量也极显著正相关,相关系数为0.941和0.946(P<0.01).土壤酶活性分析表明,土壤脱氢酶和多酚氧化酶与土壤TPH含量极显著正相关,相关系数分别为0.977和0.958(P<0.01);与PAHs含量也极显著正相关,相关系数分别为0.997和0.977(P<0.01).土壤中的脲酶受污水灌溉中含N物质的影响与TPH含量显著相关,相关系数为0.713(P<0.05),与PAHs污染无明显相关性.而纤维素酶与土壤有机物污染无明显相关关系.土壤微生物生物量和土壤脱氢酶、多酚氧化酶可以作为污灌土壤TPH和PAHs污染敏感的生物学和生物化学指标.     

Effects of Bacterial-Feeding Nematode Grazing and Tea Saponin Addition on the Enhanced Bioremediation of PyreneContaminated Soil Using Polycyclic Aromatic Hydrocarbon-Degrading Bacterial Strain

As one of the most widely distributed bacterial predators in the soil, the role of bacterivorous nematodes on the enhanced bioremediation of polycyclic aromatic hydrocarbon-contaminated soils is crucial, but remains to be investigated.A microcosm-level study was conducted to examine the effects of bacterial-feeding nematode grazing and tea saponin(TS) addition on bioremediation of a pyrene-contaminated soil enhanced by the polycyclic aromatic hydrocarbon(PAH)-degrading bacterial strain Sphingobium sp.PHE9.After 180 d of incubation, the highest pyrene dissipation(71.3%) was achieved through a combination of Sphingobium sp.PHE9 inoculation with nematode and TS addition.Meanwhile, high counts of culturable PAH-degrading bacteria, soil enzyme activity, and biodiversity indices were observed under the combined treatment, implying that the microbiological function of the contaminated soil was significantly restored.Additionally, the results of Tenax~ extraction with the first-order three-compartment model indicated that rate-limiting factors varied among treatments.The lack of degrading microorganisms was the main rate-limiting factor for the treatments involving TS/nematode addition, and inadequate bioaccessible pyrene was the vital rate-limiting factor in the treatments involving Sphingobium sp.PHE9 inoculation.The proposed combined clean-up strategy proved to be a promising bioremediation technology for aged pyrene-contaminated soils.     

低分子量有机酸作用下土壤中菲和芘的残留及形态

采用微宇宙试验方法,以菲和芘为多环芳烃(PAHs)代表物,研究了几种低分子量有机酸作用下黄棕壤中菲和芘的残留和形态。结果表明,老化60 d后土壤中菲和芘的残留含量明显减少;不施加有机酸的对照土壤中,菲和芘的残留含量为10.13和29.18 mg kg-1,去除率为87.33%和63.50%。与对照相比,供试浓度(0～64 mg kg-1)范围内,柠檬酸、草酸、酒石酸等3种低分子量有机酸作用下土壤中PAHs残留含量提高,去除率减小,表明供试条件下有机酸抑制土壤中菲和芘的降解;进一步分析发现,少量(≤4 mg kg-1)的有机酸即可对PAHs降解产生高的抑制效果。微生物降解在PAHs的去除中起重要作用,且芘比菲更抗微生物降解。供试条件下,可脱附态和有机溶剂提取态是土壤中菲和芘存在的主要形态,而结合态残留占总残留的比例很小(<8.5%)。3种有机酸均提高了土壤中可脱附态和有机溶剂提取态菲和芘的残留含量,施加有机酸使土壤中菲和芘的可脱附态含量较对照分别提高了46.67%～749.1%和1.83%～80.20%,有机溶剂提取态则提高了8.73%～375.2%和22.63%～114.3%;低分子量有机酸作用下结合态的菲和芘含量仍很小。     

The combined effects of earthworms and arbuscular mycorrhizal fungi on microbial biomass and enzyme activities in a calcareous soil spiked with cadmium

Earthworms and arbuscular mycorrhizal fungi (AMF) are known to independently affect soil microbial and biochemical properties, in particular soil microbial biomass (SMB) and enzymes. However, less information is available about their interactive effects, particularly in soils contaminated with heavy metals such as cadmium (Cd). The amount of soil microbial biomass C (MBC), the rate of soil respiration (SRR) and the activities of urease and alkaline phosphatase (ALP) were measured in a calcareous soil artificially spiked with Cd (10 and 20 mg Cd kg⁻¹), inoculated with earthworm (Lumbricus rubellus L.), and AMF (Glomus intraradices and Glomus mosseae species) under maize (Zea mays L.) crop for 60 days. Results showed that the quantity of MBC, SRR and enzyme activities decreased with increasing Cd levels as a result of the elevated exchangeable Cd concentration. Earthworm addition increased soil exchangeable Cd levels, while AMF and their interaction with earthworms had no influence on this fraction of Cd. Earthworm activity resulted in no change in soil MBC, while inoculation with both AMF species significantly enhanced soil MBC contents. However, the presence of earthworms lowered soil MBC when inoculated with G. mosseae fungi, showing an interaction between the two organisms. Soil enzyme activities and SRR values tended to increase considerably with the inoculation of both earthworms and AMF. Nevertheless, earthworm activity did not affect ALP activity when inoculated with G. mosseae fungi, while the presence of earthworm enhanced urease activity only with G. intraradices species. The increases in enzyme activities and SRR were better ascribed to changes in soil organic carbon (OC), MBC and dissolved organic carbon (DOC) contents. In summary, results demonstrated that the influence of earthworms alone on Cd availability is more important than that of AMF in Cd-polluted soils; and that the interaction effects between these organisms on soil microorganism are much more important than on Cd availability. Thus, the presence of both earthworms and AMF could alleviate Cd effects on soil microbial life.     

A highly effective polycyclic aromatic hydrocarbon-degrading bacterium, Paracoccus sp. HPD-2, shows opposite remediation potential in two soil types

Bioaugmentation is an efficient and eco-friendly strategy for the bioremediation of polycyclic aromatic hydrocarbons (PAHs). Since the degrading abilities of soils can greatly alter the abilities of PAH-degrading bacteria, illustrating the potential and mechanism of highly efficient degrading bacteria in different soil environments is of great importance for bioremediation. A PAH-degrading bacterium, Paracoccus aminovorans HPD-2, and two soil types, red and paddy soils, with distinct PAH-degrading abilities, were selected for this study. A soil microcosm experiment was performed by adding pyrene (PYR) and benzo[a]pyrene (B[a]P). Illumina sequencing was used to examine bacterial community structure. The results showed that inoculation with HPD-2 significantly elevated PYR and B[a]P degradation rates by 44.7% and 30.7%, respectively, in the red soil, while it only improved the degradation rates by 1.9% and 11%, respectively, in the paddy soil. To investigate the underlying mechanism, the fate of strain HPD-2 and the response of the indigenous bacterial communities were determined. Strain HPD-2 occupied certain niches in both soils, and the addition of the bacterium changed the native community structure more noticeably in the red soil than in the paddy soil. The addition of PAHs and strain HPD-2 significantly changed the abundances of 7 phyla among the 15 detected phyla in the red soil. In the paddy soil, 5 of the 12 dominant phyla were significantly affected by PAHs and the inoculation of HPD-2, while 6 new phyla were detected in the low-abundance phyla (< 0.1%). The abundances of Massilia, Burkholderia, and Rhodococcus genera with PAH degradation efficiency were significantly increased by the inoculation of HPD-2 in the red soil during 42 d of incubation. Meanwhile, in the paddy soil, the most dominant effective genus, Massilia, was reduced by HPD-2 inoculation. This research revealed the remediation ability and inherent mechanism of the highly effective PAH-degrading strain HPD-2 in two different soil types, which would provide a theoretical basis for the application of degrading bacteria in different soils.     

不同恢复方式下盐渍化弃耕地土壤生物学活性的变化

以干旱区新疆玛纳斯河流域冲积扇缘定点定位试验地为研究对象, 研究灌溉处理、人工草地处理和补植处理对盐渍化弃耕地土壤微生物量、酶活性及土壤呼吸速率的影响。结果表明, 不同恢复方式均明显增加了土壤微生物数量和土壤微生物量碳、氮及土壤酶活性。不同处理土壤微生物量碳、氮分别比原始弃耕地高17.80%、26.38%、5.33%和7.89%、12.75%、21.93%; 不同处理土壤微生物数量分别是原始弃耕地的4.72倍、6.04倍和4.56倍; 不同处理土壤蔗糖酶活性分别比原始弃耕地高3.4倍、3.2倍和7.7倍, 多酚氧化酶活性比原始弃耕地高1.7倍、1.2倍和1.5倍, 脲酶活性比原始弃耕地高11.1%、52.3%和37.1%; 灌溉处理土壤过氧化氢酶活性最高, 是原始弃耕地的1.53倍, 土壤呼吸速率变化表现为人工草地处理>灌溉处理>补植处理>原始弃耕地, 其中, 人工草地处理土壤呼吸速率比弃耕地高52.25%。相关分析表明, 微生物量碳与微生物C/N和微生物数量之间均呈显著正相关关系(P<0.05); 土壤呼吸速率与土壤脲酶、微生物数量和微生物量碳的相关性达到显著水平(P<0.05), 与土壤微生物量氮呈负相关关系, 但相关性不显著; 土壤蔗糖酶与其他3种酶以及微生物量氮呈显著正相关关系, 土壤脲酶与微生物数量呈显著正相关关系, 多酚氧化酶与过氧化氢酶相关性达到显著水平(P<0.05)。本研究表明干旱区盐渍化弃耕地采用灌溉与人工草地处理有利于土壤养分积累, 可在一定程度上改善土壤质量。     

菲在黑麦草种植土壤中的降解及其对土壤酶的影响

研究了种植黑麦草对土壤中3环多环芳烃菲的动态降解作用。结果表明,黑麦草可以促进土壤中菲的降解,在75 d的盆栽试验里,种植黑麦草土壤中菲的可提取浓度明显低于不种植土壤（p<0.05）。在菲浓度为5 mg kg^-1、50 mg kg^-1、200 mg kg^-1的3种处理中,种植黑麦草壤中菲的降解率分别为81.07%、90.35%、84.94%,而不种植土壤中菲的降解率分别为75.34%、86.62%、67.60%。种植黑麦草增强了土壤中多酚氧化酶、脱氢酶和过氧化氢酶的活性以及增加土壤中微生物生物量碳的含量,即提高了土壤中生物活性,从而促进了土壤中菲的降解率。不同浓度菲处理,土壤中生物活性存在明显差异,高浓度菲(200 mg kg^-1)对土壤中生物活性产生较强的抑制作用,影响土壤中生物对菲的降解作用,从而揭示了植物促进菲降解的生物学及酶学机理。黑麦草对土壤中多环芳烃有较强的忍耐性,但过高的菲浓度对黑麦草的生长有影响。     

海洋细菌生物膜用于生物修复陆地生态系统中土壤多环芳烃污染

Polycyclic aromatic hydrocarbons(PAHs) in soil retain for a quite long period due to their hydrophobicity and aggregation properties. Biofilm-forming marine bacterial consortium(named as NCPR), composed of Stenotrophomonas acidaminiphila NCW702,Alcaligenes faecalis NCW402, Pseudomonas mendocina NR802, Pseudomonas aeruginosa N6P6, and Pseudomonas pseudoalcaligenes NP103, was used for the bioremediation of PAHs in a soil microcosm. Phenanthrene and pyrene were used as reference PAHs. Parameters that can affect PAH degradation, such as chemotaxis, solubility of PAHs in extracellular polymeric substances(EPS), and catechol2,3-dioxygenase(C23O) activity, were evaluated. P. aeruginosa N6P6 and P. pseudoalcaligenes NP103 showed chemotactic movement towards both the reference PAHs. The solubility of both the PAHs was increased with an increase in EPS concentration(extracted from all the 5 selected isolates). Significantly(P 0.001) high phenanthrene(70.29%) and pyrene(55.54%) degradation was observed in the bioaugmented soil microcosm. The C23O enzyme activity was significantly(P 0.05) higher in the bioaugmented soil microcosm with phenanthrene added at 173.26 ± 2.06 nmol min~(-1) mg~(-1) protein than with pyrene added at 61.80 ± 2.20 nmol min~(-1) mg~(-1) protein. The C23O activity and gas chromatography-mass spectrometer analyses indicated catechol pathway of phenanthrene metabolism. However, the metabolites obtained from the soil microcosm added with pyrene revealed both the catechol and phthalate pathways for pyrene degradation.     

Influence of soil properties on microbial populations, activity and biomass in humid subtropical mountainous ecosystems of India

 Microbial populations, biomass, soil respiration and enzyme activities were determined in slightly acid organic soils of major mountainous humid subtropical terrestrial ecosystems, along a soil fertility gradient, in order to evaluate the influence of soil properties on microbial populations, activity and biomass and to understand the dynamics of the microbial biomass in degraded ecosystems and mature forest. Although the population of fungi was highest in the undisturbed forest (Sacred Grove), soil respiration was lowest in the 7-year-old regrowth and in natural grassland (approximately 373 μg g^–1 h^–1). Dehydrogenase and urease activities were high in "jhum" fallow, and among the forest stands they were highest in the 7-year-old regrowth. Microbial biomass C (MBC) depended mainly on the organic C status of the soil. The MBC values were generally higher in mature forest than in natural grassland, 1-year-old jhum fallow and the 4-year-old alder plantation. The MBC values obtained by the chloroform-fumigation-incubation technique (330–1656 μg g^–1) did not vary significantly from those obtained by the chloroform-fumigation-extraction technique (408–1684 μg g^–1), however, the values correlated positively (P<0.001). The enzyme activities, soil respiration, bacterial and fungal populations and microbial biomass was greatly influenced by several soil properties, particularly the levels of nutrients. The soil nutrient status, microbial populations, soil respiration and dehydrogenase activity were greater in Sacred Grove, while urease activity was greater in grassland. Received: 14 October 1998     

湿地松林土壤生化特性和酶活性对模拟硫沉降的响应

以亚热带湿地松人工林为研究对象,通过3种水平(对照CK:pH 6.5;低硫LS:pH 4.5;高硫HS:pH 2.5)的模拟硫沉降控制试验,分析土壤生化特性及酶活性对硫添加的响应。结果表明:(1)硫输入促进了土壤酸化,0—5 cm土层土壤pH在HS处理下显著降低,5—10 cm土层土壤pH在LS和HS处理下显著降低(P0.05);(2)硫输入对土壤有机碳库存在一定影响,土壤总有机碳(TOC)对硫输入无显著响应,但土层间的差异性显著增加(P0.05),土壤可溶性有机碳(DOC)受影响有限,5—10 cm土层微生物量碳(MBC)LS显著降低(P0.05);(3)硫输入对土壤有效氮库影响存在差异,土壤可溶性有机氮(DON)、铵态氮(NH_4~+—N)尚未表现出显著变化,土壤硝态氮(NO_3~-—N)、土壤微生物量氮(MBN)均在HS处理下显著降低,且硫输入加剧土层间的差异性(P0.05);(4)硫输入抑制了酶活性,土壤脲酶活性在HS处理下显著降低(P0.05),土壤蔗糖酶活性无显著变化,但硫输入均弱化了土层间酶活性的差异性。综合分析所有处理下的土壤生化性质和酶活性等指标发现,对硫添加响应敏感的是土壤pH和酶,土层是另外一个主要影响因子,硫添加和土层的交互作用则影响有限。采用Pearson分析得出,硫输入改变了土壤生化特性、酶活性等指标间的相关性程度。可见,酸雨对土壤酸化的影响是一个逐渐累积的过程,外源性硫添加对土壤碳氮及酶活性的影响存在一定差异,这可为硫沉降环境胁迫下森林管理提供科学依据。     

东祁连山不同高寒草地型牧草返青期土壤碳分布特征

以东祁连山高寒草地为样点,对土壤有机质、K2SO4浸提碳和微生物量碳(氯仿熏蒸浸提法)等进行了研究.结果表明:该区土壤有机质介于82.3～207.2 g·kg-1,植被类型影响土壤有机质含量.土壤K2SO4浸提碳介于23.61～138.81 mg·kg-1,分别占土壤有机质和土壤微生物量碳的0.03%～0.06%和9.97%～18.46%;灌丛草地中,高山柳草地显著低于杜鹃草地(P<0.05);草本草地中,珠芽蓼草地、沼泽草地和嵩草草地显著高于禾草草地(P<0.05).土壤微生物量碳介于156.19～1 182.84mg·kg-1,上层显著高于下层(P<0.05),除2005年沼泽草地外草本草地与灌丛草地间差异显著(P<0.05);微生物量碳对土壤有机质的贡献率介于0.19%～0.48%,禾草草地最低(0.19%),金露梅灌丛草地最高(0.48%),除珠芽蓼草地和沼泽草地外均为上层高于下层;且除禾草草地和嵩草草地外微生物量碳与土壤有机质、全氮和速效磷间呈显著(P<0.05)或极显著正相关(P<0.01),与土壤K2SO4浸提碳在灌丛草地呈显著正相关(P<0.05),在草本草地呈极显著正相关(P<0.01),与微生物量氮、磷间呈极显著正相关(P<0.01).该结果表明微生物量碳及其对土壤有机质的贡献率在草地型闻和土层间差异明显,且与土壤有机质、K2SO4浸提碳、全氮和速效磷关系密切.