温度和水分对长白山不同海拔梯度土壤有机质分解的影响

Decomposition of soil organic matter(SOM) is of importance for CO_2 exchange between soil and atmosphere and soil temperature and moisture are considered as two important factors controlling SOM decomposition. In this study, soil samples were collected at 5 elevations ranging from 753 to 2 357 m on the Changbai Mountains in Northeast China, and incubated under different temperatures(5, 10, 15, 20, 25, and 30?C) and soil moisture levels(30%, 60%, and 90% of saturated soil moisture) to investigate the effects of both on SOM decomposition and its temperature sensitivity at different elevations. The results showed that incubation temperature(F = 1 425.10, P 0.001), soil moisture(F = 1 327.65, P 0.001), and elevation(F = 1 937.54, P 0.001) all had significant influences on the decomposition rate of SOM. The significant effect of the interaction of incubation temperature and soil moisture on the SOM decomposition rate was observed at all the 5 sampling elevations(P 0.001). A two-factor model that used temperature and moisture as variables fitted the SOM decomposition rate well(P 0.001) and could explain 80%–93% of the variation of SOM decomposition rate at the 5 elevations. Temperature sensitivity of SOM decomposition, expressed as the change of SOM decomposition rate in response to a 10?C increase in temperature(Q_(10)), was significantly different among the different elevations(P 0.01), but no apparent trend with elevation was discernible. In addition, soil moisture and incubation temperature both had great impacts on the Q_(10) value(P 0.01), which increased significantly with increasing soil moisture or incubation temperature. Furthermore, the SOM decomposition rate was significantly related to soil total Gram-positive bacteria(R~2= 0.33, P 0.01) and total Gram-negative bacteria(R~2= 0.58, P 0.001). These findings highlight the importance of soil moisture to SOM decomposition and its Q_(10) value,which needs to be emphasized under warming climate scenarios.     

Screening of soil bacteria for plasmids carrying antibiotic resistance

Summary To evaluate the role of plasmids in soil communities antibiotic-resistant bacteria have been isolated from soil. Among them, 419 l-aminopeptidase positive strains (Gram-negative) and 28 l-aminopeptidase negative strains (Gram-positive) were screened for the presence of plasmids. None of the Gram-negative organisms contained plasmids. Among the Gram-positive bacteria plasmid-harboring strains were detected.     

Variable use of plant- and soil-derived carbon by microorganisms in agricultural soils

In this study we used compound specific ¹³C and ¹⁴C isotopic signatures to determine the degree to which recent plant material and older soil organic matter (SOM) served as carbon substrates for microorganisms in soils. We determined the degree to which plant-derived carbon was used as a substrate by comparison of the ¹³C content of microbial phospholipid fatty acids (PLFA) from soils of two sites that had undergone a vegetation change from C3 to C4 plants in the past 20-30 years. The importance of much older SOM as a substrate was determined by comparison of the radiocarbon content of PLFA from soils of two sites that had different ¹⁴C concentrations of SOM.The ¹³C shift in PLFA from the two sites that had experienced different vegetation history indicated that 40-90% of the PLFA carbon had been fixed since the vegetation change took place. Thus PLFA were more enriched in ¹³C from the new C4 vegetation than it was observed for bulk SOM indicating recent plant material as preferentially used substrate for soil microorganisms. The largest ¹³C shift of PLFA was observed in the soil that had high ¹⁴C concentrations of bulk SOM. These results reinforce that organic carbon in this soil for the most part cycles rapidly. The degree to which SOM is incorporated into microbial PLFA was determined by the difference in ¹⁴C concentration of PLFA derived from two soils one with high ¹⁴C concentrations of bulk SOM and one with low. These results showed that 0-40% of SOM carbon is used as substrate for soil microorganisms. Furthermore a different substrate usage was identified for different microorganisms. Gram-negative bacteria were found to prefer recent plant material as microbial carbon source while Gram-positive bacteria use substantial amounts of SOM carbon. This was indicated by ¹³C as well as ¹⁴C signatures of their PLFA. Our results find evidence to support ‘priming’ in that PLFA indicative of Gram-negative bacteria associated with roots contain both plant- and SOM-derived C. Most interestingly, we find PLFA indicative of archeobacteria (methanothrophs) that may indicate the use of other carbon sources than plant material and SOM to a substantial amount suggesting that inert or slow carbon pools are not essential to explain carbon dynamics in soil.     

Fatty acid composition of various ectomycorrhizal fungi and ectomycorrhizas of Norway spruce

Whole cell fatty acid (WCFA) compositions of three different structures of ectomycorrhizal (ECM) fungi: sporocarps, pure culture mycelia and ectomycorrhizas were analysed to evaluate the potential use of fatty acid profiles as biomarkers for ECM fungi and ectomycorrhiza-associated bacteria. Sporocarps of Amanita muscaria, Amanita rubescens, Lactarius rufus, Lactarius thejogalus, Leccinum scabrum, Paxillus involutus, Russula foetens, Russula rosea, Russula vesca, Suillus grevillei, Tylopilus felleus, Xerocomus badius, Xerocomus subtomentosus, pure cultures of A. muscaria, P. involutus, X. badius, X. subtomentosus, Suillus bovinus Suillus luteus and seven ectomycorrhizal morphotypes of Norway spruce were examined. Our results revealed species-specific composition of fatty acids of fungal sporocarps and pure culture mycelia. Ectomycorrhizal morphotypes distinguished and identified by morphological and molecular methods (PCR-RLFP and sequencing) created specific fatty acid profiles. The dominating fatty acids in pure cultures and sporocarps were 18:2ω6,9, 18:1ω9 and 16:0, whereas ectomycorrhizas also contained plant and bacterial specific fatty acids. Especially, fatty acids specific to Gram-positive bacteria 15:0 anteiso and 17:0 anteiso were present in relatively high amounts and suggested that these bacteria are dominating in the examined Norway spruce mycorrhizosphere. In conclusion, our results show that fatty acid based methods can be useful in studies of ectomycorrhizal fungi, both as a quick method for differentiation of fungal species and also in studies of mycorrhiza-associated microorganisms in the field.     

解钾细菌C6X对不同富钾矿物含量土壤钾素迁移的影响

为了改善黄土高原地区煤炭开采引起土壤质量急剧退化的现状,该文以玉米为供试植物,通过日光温室短期盆栽的方式,系统研究解钾细菌C6X和玉米生长对土壤钾素迁移的影响.结果表明:1)玉米生长条件下,解钾细菌在富钾矿物质量分数45％上层土壤(0～20 cm)中对速效钾增量的促进作用最佳.2)解钾细菌和玉米生长协同提高上层土壤钾素固定能力,缓效钾增量在土壤富钾矿物质量分数68％为最大值.3)解钾细菌和玉米生长协同促进土壤钾素上移能力,在富钾矿物质量分数45％水平,土壤上移速效钾呈最大值;同时,解钾细菌促进土壤上移速效钾和玉米钾素积累量二者趋于线性稳定,利于土壤钾肥长期管理.因此,解钾细菌和玉米生长协同促进土壤钾素的释放和固定,并促进土壤钾素上移.     

Land use changes the soil carbon stocks,microbial biomass and fatty acid methyl ester (FAME) in Brazilian semiarid area

Land use affect soil C and microbial structure, especially in tropical dry areas. The objective of this study was to evaluate the effects of the land use on physical, chemical, and microbiological attributes of soils from Brazilian semiarid. We analyzed soil physical, chemical, total carbon stocks (TCS), water-soluble carbon (WSC), microbial biomass carbon (MBC) and microbial structure of soil from forest, no irrigation maize, succession areas (Anadenanthera falcate and Tabebuia alba) and secondary shrubby vegetation. The use of soil influences C stock. The forest soil showed higher TCS and MBC. The conversion in T. alba reduced in 9% soil total bacteria. The multivariate analysis showed that TCS, MBC and FAMEs contributed to separation of natural forest and other areas in the superficial layer. This study indicates that the conversion of forest into successional areas can decrease by up to 44% TCS and 68% MBC. The present study provided alarming data concerning the impact of land use on quality of soil in a tropical dry region in Northeastern Brazil. Our results provide an alternative tool for the management of deforested dry areas that could serve as guideline for management plan to sustainability for agricultural impacted dry areas.     

中国北方温带草原土壤微生物对气温变暖与添加氮素的响应特征

The responses of soil microbes to global warming and nitrogen enrichment can profoundly affect terrestrial ecosystem functions and the ecosystem feedbacks to climate change. However, the interactive effect of warming and nitrogen enrichment on soil microbial community is unclear. In this study, individual and interactive effects of experimental warming and nitrogen addition on the soil microbial community were investigated in a long-term field experiment in a temperate steppe of northern China. The field experiment started in 2006 and soils were sampled in 2010 and analyzed for phospholipid fatty acids to characterize the soil microbial communities. Some soil chemical properties were also determined. Five-year experimental warming significantly increased soil total microbial biomass and the proportion of Gram-negative bacteria in the soils. Long-term nitrogen addition decreased soil microbial biomass at the 0-10 cm soil depth and the relative abundance of arbuscular mycorrhizal fungi in the soils. Little interactive effect on soil microbes was detected when experimental warming and nitrogen addition were combined. Soil microbial biomass positively correlated with soil total C and N, but basically did not relate to the soil C/N ratio and pH. Our results suggest that future global warming or nitrogen enrichment may significantly change the soil microbial communities in the temperate steppes in northern China.     

露天矿排土场植物恢复对土壤氮循环功能基因的影响

   植被恢复对改善矿区生态环境至关重要,可促进重构土壤发育,从而调控生物地球化学循环和发挥生态系统功能。本研究为明确露天矿区植物恢复对土壤氮循环微生物类群及功能基因丰度的影响。   采集内蒙古准格尔旗黑岱沟露天矿东排土场苜蓿（GL）、沙棘（BL）、油松（CF）和刺槐（BF）复垦区及对照（CK）共25个表土样品,利用高通量qPCR芯片技术测定土壤氮循环功能基因丰度。   ①不同植被对土壤理化性质、酶活性及氮循环功能基因丰度影响有显著差异（P < 0.05）。BL对土壤有机碳、有效磷累积优于其他植被,BF对土壤铵态氮累积有优势,但土壤全氮和有机碳低于CK。复绿显著地提高土壤过氧化氢酶活性,并降低了土壤β-葡萄糖苷酶、脲酶和亮氨酸氨基肽酶活性。但复绿对土壤氮循环功能基因丰度的影响完全一致：BF > CF > BL > GL > CK。②土壤氮循环功能基因丰度与土壤pH呈显著性正相关（P < 0.01）,与土壤硝态氮、总氮、脲酶、亮氨酸氨基肽酶和碱性磷酸酶活性呈显著性负相关（P < 0.05）。③不同植被直接影响土壤过氧化氢酶或硝化功能基因丰度从而操控土壤氮循环功能基因丰度,或通过反硝化功能基因丰度影响土壤过氧化氢酶再间接影响氮循环过程。   露天矿植物恢复影响土壤酶活性和氮循环功能基因丰度而影响土壤氮循环过程,灌丛（沙棘）对该地区土壤质量的改善有着更好的效果。     

Drought Tolerance and Ion Accumulation of Rice Following Application of Additional Potassium Fertilizer

Five levels of water stress cycle (control flooded, control saturated, 5, 10, and 15 days of irrigation interval) and three potassium fertilization levels [80 kg, 120 kg, and kg 160 dipotassium oxide (K₂O) ha^?1] were exposed to investigate the influence of potassium fertilizer for minimizing water stress effect and maximizing productivity of rice. Different phyto-physiological parameters as well as uptake of major nutrient elements [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe)] were examined. It was observed that rice yield, harvest index, and other physiological parameters reduces with increasing duration of water stress while application of additional potassium fertilizer has progressive impact on those parameters. From our observation, 10 days of watering cycle with potassium fertilization at 120 kg K₂O ha^?1 produces highest grain yield and harvest index. Uptake of major nutrient elements was also enhanced by potassium fertilizer. Therefore, it can be stated that additional potassium fertilizer application could be useful to mitigate water stress effect in rice.     

微生物菌剂对盐碱土理化和生物性状影响的研究

采用盆栽试验方法,研究了微生物菌剂对盐碱土壤微生物、养分、盐分及玉米苗期生长的影响。结果表明,施用微生物菌剂后,盐碱土壤中钾细菌和枯草芽孢杆菌数量、土壤有机质含量、速效N、P、K含量状况均明显高于无添加菌剂对照处理,其中以菌剂施用量为0.4g·kg^-1土的效果最明显。施用微生物菌剂后,土壤pH、含盐量均有不同程度地降低,菌剂施用量0.4g·kg^-1土的处理在前中期表现出较好的土壤脱盐效果,而菌剂施用量0.8g·kg^-1土的处理在后期脱盐效果较好。添加微生物菌剂促进玉米苗期株高和叶片数增加,有利于玉米地上部分干物质的积累,以菌剂施用量0.4g·kg^-1土的效果最明显。差异显著性检验表明,菌剂处理玉米株高、干物质重与无添加菌剂对照相比差异均达显著水平,但不同菌剂量处理间差异不明显。综合判定菌剂施用量0.4g·kg^-1土对盐碱土理化和生物性状改良效果较好。     

石灰性紫色土硝化作用及硝化微生物对不同氮源的响应

土壤中发生的硝化作用是对p H高度敏感的典型过程。本文采用室内恒温培养法,结合定量PCR和高通量测序,研究石灰性紫色土硝化作用以及氨氧化细菌(Ammonia-oxidizing bacteria,AOB)、氨氧化古菌(Ammonia-oxidizing archaea,AOA)、亚硝酸盐氧化细菌(Nitrite-oxidizing bacteria,NOB)的丰度与群落结构对不同氮源的响应。结果表明:不同氮源均刺激土壤硝化作用的发生,CO(NH2)2处理下的净硝化速率最大,约是CK处理的4.76倍,(NH_4)2SO4和NH_4Cl处理下的净硝化速率分别为N 3.88和3.34 mg kg-1d-1。相比于(NH_4)2SO4和CO(NH2)2处理,NH_4Cl处理降低了硝态氮的累积量,抑制了铵态氮的减少量。AOB amo A基因拷贝数在28 d培养过程中变化显著(p0.05),在(NH_4)2SO4和CO(NH2)2处理中呈先增长后降低趋势,在NH_4Cl处理中呈持续增长趋势;而AOA amo A基因拷贝数无显著变化(p0.05)。说明石灰性紫色土硝化作用的主要推动者是AOB,而不是AOA。在28 d培养过程中,亚硝酸盐氧化细菌占总微生物的比例高于氨氧化细菌和古菌,意味着石灰性紫色土中可能存在全程氨氧化微生物(Comammox)。高通量测序的结果表明:石灰性紫色土中AOB的优势种群为亚硝化螺菌Nitrosospira Cluster 3,AOA的优势种群是土壤古菌Group 1.1b,NOB的优势种群是硝化螺菌Nitrospira。     

土壤矿物钾活化途径

针对我国钾肥资源短缺问题,分析了土壤钾资源的开发潜力,概述了土壤矿物钾的存在状态及其释放特点,综述了硅酸盐细菌、富钾植物和有机酸活化土壤矿物钾的能力与机理,并展望了活化土壤矿物钾的三种途径在生产中的应用前景。     

海水稻根际效应对滨海盐碱地土壤氨氧化微生物的影响

滨海盐碱地的特殊环境严重限制了土壤氮素转化和利用。微生物介导的水稻根际氨氧化过程是盐碱稻田土壤氮循环的关键过程,但限于研究盲点和技术不足,海水稻根际效应对滨海盐碱地土壤氨氧化微生物群落结构的影响仍少有报道。据此,本研究以“海稻86”为研究对象,分别设置低盐浓度(2 g·kg^–1)和高盐浓度(6 g·kg–1)两组处理进行盆栽试验。结果显示：种植海水稻70 d后,高盐和低盐处理根际土壤的pH分别下降了0.82和0.70个单位,土壤有机质(SOM)含量下降了6.41和4.46 g·kg^–1,腐殖质(HU)含量提高了5.76和4.45 g·kg^–1,全氮(TN)含量减少0.46和0.37 g·kg^–1,表明海水稻可通过降低盐碱地土壤pH,加速有机质分解转化,提高土壤氮循环速率。水稻根际作用可显著提高土壤微生物生物量碳(MBC)、微生物生物量氮(MBN)和微生物呼吸强度,并在种植第55天达到最高,在高盐处理中分别达到850.0 mg·kg^–1、72.2 mg·kg^–1     

解磷、钾功能性微生物耐盐效应研究

围绕设施菜田土壤盐渍化问题,以解磷、钾功能微生物胶质芽孢杆菌和巨大芽孢杆菌为研究对象,探究了盐分胁迫对功能菌活性、解磷钾能力的影响,并阐明了含2种功能菌微生物菌剂在轻度盐渍化设施菜田的作用效应。结果表明,混合功能菌最大耐受盐浓度为10.5%NaCl,最适宜生长盐分浓度为0.5%NaCl,且解磷、钾能力最强,有效磷、钾增幅分别为52.06%,75.41%;此外,轻度盐渍化设施菜田的小区试验结果显示含2种功能菌的菌剂可提高番茄、甜瓜、西瓜果实VC和可溶性糖含量,分别增产104.81%,23.72%,28.96%;土壤中有效磷和速效钾含量分别提高95.12%,22.83%,134.52%和92.71%,6.66%,117.46%,显著增加了土壤菌群数量(P0.05)。综上所述,解磷、钾功能微生物具有耐盐性,可在轻度盐渍化土壤中定殖,并能活化土壤磷、钾,提高蔬菜产量和改善品质。