放牧对小针茅荒漠草原土壤微生物分布的影响

以苏尼特右旗小针茅荒漠草原为样本区域,分别设置无牧、轻度、中度、重度和极重度放牧5种放牧梯度,在生长季(5月～9月)内对不同放牧强度下小针茅荒漠草原三大类土壤微生物(细菌、真菌、放线菌)的分布特征进行了研究.结果表明:不同放牧强度下,小针茅荒漠草原三大类微生物的数量及比例具有明显的季节性分布特征;小针茅荒漠草原土壤微生物数量表现为土壤细菌数量＞放线菌＞真菌,其垂直分布具有明显的差异性,三大类群土壤微生物数量随土层加深而减少;随放牧强度的增加,不同土层三大类群土壤微生物数量均随之减少.     

哈萨克斯坦首都努尔苏丹人工林健康评价

通过分析努尔苏丹不同人工林,筛选健康综合评价指标,建立健康综合评价模型,为努尔苏丹及其周边人工林提供健康综合评价理论基础。调查努尔苏丹25块人工林样地和2块天然林样地,选取林下植物Shannon-Wiener指数(X_1)、Pielou指数(X_2)、Simpson指数(X3)、林分空间综合结构综合指数(X_4)、土壤有机质(X_5)、全氮(X_6)、全磷(X_7)、p H(X_8)、质量含水量(X_9)、林木平均株高(X10)、平均胸径(X11)、平均枝下高(X12)、平均冠幅(X13)和林下更新(X14)共14个指标,采用因子分析、聚类分析、判别分析和逐步回归分析等多元统计分析法,对努尔苏丹人工林健康状况开展综合评价。通过因子分析将14个单项指标转换为4个相互独立的综合指标,其贡献率分别为30.482%、24.374%、19.711%和8.646%,代表了全部数据83.212%的信息量。结合因子得分系数矩阵与各因子权重得到健康综合得分值。对健康综合得分值进行聚类分析,将选择的样地划分为5类,优质健康(Ⅰ)、良好健康(Ⅱ)、一般健康(Ⅲ)、亚健康(Ⅳ)和不健康(Ⅴ)。使用判别分析验证聚类分析的效果,其自身验证与交叉验证的准确率分别为100%、85.185%。采取逐步回归分析建立努尔苏丹人工林健康评价最优数学模型,H=0+0.293X13+0.186X5+0.079X3+0.100X2+0.038X7(R2=0.987),筛选出5个判断人工林健康状况的指标,分别为平均冠幅、土壤有机质、Simpson指数、Pielou指数和土壤全磷。平均冠幅、土壤有机质、Simpson指数、Pielou指数和土壤全磷可作为判断努尔苏丹人工林健康状况的指标,可在相同条件下测定这5项指标,计算健康综合评价值并预测其健康状况。     

水分对尕海湿地退化演替土壤氮矿化的影响

水分是湿地土壤氮矿化过程的主要调控因子,对于湿地土壤中氮素循环过程具有重要作用.以甘南尕海湿地为研究对象,设置4个退化程度(未退化UD、轻度退化LD、中度退化MD和重度退化HD)和4个田间持水量(20％ FC、40％ FC、60％ FC和80％ FC),通过室内49 d的好气培养,测定各处理条件下湿地土壤在0～10 c...     

小飞蓬入侵对伊犁河谷草原土壤有机碳的影响

为探讨小飞蓬入侵对伊犁河谷草原生态系统的影响,揭示小飞蓬的入侵机制,对不同入侵程度(轻度、中度、重度)小飞蓬及本地植物猪毛蒿根际土壤有机碳(SOC)、土壤容重和土壤含水量的变化规律进行研究。结果表明:随着小飞蓬入侵程度的加深,土壤SOC含量上升:小飞蓬重度、中度、轻度入侵和猪毛蒿群落土壤有机碳含量平均值分别为16.70、11.31、9.56 g·kg~(-1)和8.23 g·kg~(-1),表明小飞蓬入侵增加了伊犁河谷草原土壤SOC的含量,随着入侵程度的加深,土壤SOC含量提高更加明显,同时增加了伊犁河谷草原土壤的碳汇功能。从垂直分布剖面上看,4个群落土壤SOC含量变化一致:随着土壤深度的增加而SOC含量减少,且最大土壤SOC含量均出现在0～20 cm土层,小飞蓬重度、中度、轻度入侵和猪毛蒿群落最大土壤SOC含量分别为:20.3、15.0、13.2 g·kg~(-1)和11.5 g·kg~(-1)。小飞蓬重度、中度、轻度入侵和猪毛蒿群落土壤容重平均值分别为5.02、4.94、4.85 g·kg~(-1)和5.09 g·kg~(-1),土壤含水量平均值分别为1.22%、1.20%、1.19%和1.24%,表明小飞蓬的入侵改变了伊犁河谷土壤物理性质,随着小飞蓬入侵程度的加深不断降低土壤容重与含水量,土壤含水量与土壤容重存在极显著的正相关性(P0.01),结合土壤SOC进行分析,发现土壤容重与含水量对土壤SOC的影响一致,均呈现极其显著的负相关性(P0.01)。     

基于CVOR指数的巴音布鲁克高寒草原健康评价

利用草地生态系统健康评价CVOR综合指数,对巴音布鲁克高寒草原生态系统2004—2012年健康状态进行评价与退化分级研究,并对引起CVOR变化的内在驱动力因素进行探讨。结果表明:(1)研究区高寒草原生态系统健康状况由一般病态(2004年CVOR=0.58)逐渐恢复为健康状态(2012年CVOR=0.72);退化状况由强度退化恢复为中度退化,但局部仍存在强度退化;(2)降水是高寒草原生态系统CVOR指数的主要限制因子,降水也是除基况外各分指数变化的重要驱动因素;在气候变化背景下,CVOR指数将上升;(3)放牧改变了围栏外的群落功能组分,围封可以改善高寒草原生态系统的健康状况,有利于植被的正向演替,过度放牧是影响高寒草原恢复和演替的重要因素。总体上,降水和放牧是影响研究区高寒草原健康状况的主要原因。     

开都河流域下游绿洲土壤盐渍化时空变化及其成因分析

以开都河流域下游绿洲为研究区,以1973年MSS、1990年TM、2010年ETM+影像和统计资料为基本数据源,运用RS与GIS技术对研究区土壤盐渍化的类型、程度、面积与空间分布信息进行提取,利用土地转移矩阵和盐渍化动态度模型对近40a研究区土壤盐渍化时空动态变化及其成因进行分析。研究结果表明:1)1973年土壤盐渍化面积为1293.14km2,2010年为659.68km2,减少633.46km2;其中重度盐渍化面积减少150.69km2,中度盐渍化面积减少370.56km2,轻度盐渍化面积减少112.21km2,均呈现下降趋势。2)1973～2010年,重度、中度、轻度土壤盐渍化向绿洲边缘移动;重度、中度、轻度盐渍化地之间相互转化,荒地是三类盐渍化地转入面积的主要部分。3)大陆荒漠性气候、成土母质富含硫酸盐和氯化物、低洼的地形、地下水位浅等自然因素是该区域土壤盐渍化发生演变的内因;大规模的绿洲土地开发利用和不合理的农业灌溉模式等人类经济活动是其发生演变的外因。     

巴音布鲁克高寒草地退化演替阶段植物群落特性研究

以新疆天山南坡巴音布鲁克高寒草地为研究对象,通过主分量分析以及群落多样性指标,分析了不同退化演替阶段高寒草地植物群落特性变化规律。结果表明:以重要值为参数通过主分量分析(PCA)对样方进行排序,得到未退化、轻度退化、中度退化、重度退化4种类型群落;随着植物群落的逆行演替,优良牧草盖度、高度、频度等呈递减趋势,杂类草表现为增加趋势,植物群落物种多样性丧失。未退化阶段群落羊茅(Festuca ovina)、紫花针茅(Stipa purpurea)为优势种,随着退化加重,天山赖草(Leymus tianschanicus)、委陵菜(Ptentilla spp.)等在群落中占主导地位,地下芽根茎型草本植物逐渐代替地面芽密丛型禾草植物成为群落优势种。     

高寒草甸退化对土壤电导率变化影响的研究

土壤电导率是表征土壤水溶性盐的一个重要指标,可反映土壤盐渍化程度。为了研究高寒草甸退化对土壤电导率的影响,以三江源区未退化高寒草甸和退化高寒草甸为研究对象,系统分析了退化高寒草甸的植被特征和土壤特征与土壤电导率的相互关系。结果表明:高寒草甸退化会对土壤电导率产生显著负影响,且土壤电导率与评价高寒草甸的退化指标植被盖度、地上生物量、土壤有机质、土壤全氮含量表现出一致的变化趋势。因而,认为高寒草甸的退化是会引起土壤电导率的变化,土壤电导率作为土壤盐渍化程度的衡量指标,亦可作为评价草甸退化的客观指标之一。     

利用强度对荒漠草原土壤氮循环系统的影响

随着气候的变化和人类的干扰,草原退化日趋严重。文中研究了内蒙古荒漠草原不同利用强度下土壤中4类氮素转化菌,以及土壤的固氮作用、氨化作用和硝化作用强度。结果表明,轻牧区土壤中4类氮素转化菌的数量显著增加（P〉0.05）,也显著加强了土壤中的固氮作用、氨化作用和硝化作用。有利于促进土壤的氮循环;重度利用则导致草原土壤中氮素...     

西藏沙漠化程度及其分区评价

从区域沙漠化程度概念出发,本文依据西藏沙漠化普查和荒漠化监测所得的1991年与1997年两期土地沙漠化数据,选择沙漠化土地占地率、重度沙漠化土地占地率、沙漠化土地年增率、沙漠化土地年扩大面积占地率四个指标,采用多指标加权综合指数法,对西藏各个沙漠化县(市、区)的沙漠化现状程度等级进行了定性与定量兼有的评价,在此基础上对西藏沙漠化程度进行了区域概括与分区。评价结果,西藏65个沙漠化县(市、区)中有16个属于中度沙漠化程度,其余全部属于轻度,全区可划分出9个沙漠化程度区,其中轻度区4个、中度区5个,总体而言西藏土地沙漠化程度较轻。     

Degradation of mecoprop at different concentrations in surface and sub-surface soil

Biodegradation of [ring-¹⁴C] mecoprop (2-(4-chloro-2-methylphenoxy)propionic acid) was determined in surface and sub-surface soil at concentrations of 0·0005, 0·05, 0·5, 5, 50, 500, 5000 and 25000 mg kg^-1. The kinetics of mineralisation were evaluated from the mineralisation rates as a function of time and by non-linear regression analysis. In the sub-surface soil, degradation was 6–8 times slower than in surface soil, but the shape of the curves was the same in both layers. At concentrations between 0·0005 and 0·5 mg kg^-1, in both surface and sub-surface soil, degradation was initially zero-order followed by first-order kinetics. At 5 to 500 mg kg^-1 in surface soil and 5 to 50 mg kg^-1 in sub-surface soil the degradation rate was initially either constant or decreasing followed by exponential degradation indicating increasing populations of mecoprop decomposers in the soil. At 5000 and 25000 mg kg^-1 in the surface soil and at 500, 5000 and 25000 mg kg^-1 in the sub-surface soil, the degradation was negligible, as determined by the percentage [¹⁴C] carbon dioxide evolved. By non-linear regression, the three-half order model was found to describe the mineralisation. © 1998 SCI     

毒死蜱在灭菌和未灭菌土壤中的降解研究

研究了不同浓度毒死蜱在灭菌和未灭菌土壤中的降解规律。结果表明,不同浓度毒死蜱处理土壤,其降解速率不同。10 mg/kg处理未灭菌土壤时的半衰期为79.2 d,100 mg/kg和1 000 mg/kg处理土壤时,半衰期分别为91.8 d和278 d;而灭菌土壤中毒死蜱的半衰期分别为未灭菌土的3~4倍,1 000 mg/kg药液处理灭菌土时毒死蜱的半衰期长达672.3 d。     

贺兰山西坡不同类型草地土壤酶活性特征

以阿拉善左旗境内贺兰山中段（西坡）山前地带的主要草地类型为对象,分析不同类型草地土壤酶活性的分布特征,及其与气候、植被和土壤等环境因子的关系。结果表明：① 随着海拔高度的降低,土壤脲酶、蔗糖酶、碱性磷酸酶和过氧化氢酶活性表现为：高山草甸＞山地草原＞山地荒漠草原＞草原化荒漠,且在0～10 cm土层的差异尤其显著;② 各类草地土壤酶活性均沿土壤垂直剖面依次降低,差异呈显著性水平;③ 偏相关及逐步回归分析表明,影响该区草地土壤脲酶和蔗糖酶活性最主要的因素为土壤微生物碳氮、有机碳和全氮,碱性磷酸酶主要受土壤微生物碳和全氮影响,对过氧化氢酶影响最大的因子为土壤微生物碳、pH、全氮和降水量。     

Evidence for 2,4‐D mineralisation in Mediterranean soils: impact of moisture content and temperature

BACKGROUND: The 2,4‐D degradation ability of the microbiota of three arable Mediterranean soils was estimated. The impact of soil moisture and temperature on 2,4‐D degradation was investigated. RESULTS: The microbiota of the three soils regularly exposed to 2,4‐D were able rapidly to mineralise this herbicide. The half‐life of 2,4‐D ranged from 8 to 30 days, and maximum mineralisation of ¹⁴C‐2,4‐D ranged from 57 to 71%. Extractable ¹⁴C‐2,4‐D and ¹⁴C‐bound residues accounted for less than 1 and 15% respectively of the ¹⁴C‐2,4‐D initially added. The highest amounts of ¹⁴C‐2,4‐D bound residues were recorded in the soil with the lowest 2,4‐D‐mineralising ability. Although all three soils were able to mineralise 2,4‐D, multivariate analysis revealed that performance of this degrading microbial activity was dependent on clay content and magnesium oxide. Soil temperature affected the global structure of soil microbial community, but it had only a moderate effect on 2,4‐D‐mineralising ability. 2,4‐D‐mineralising ability was positively correlated with soil moisture content. Negligible 2,4‐D mineralisation occurred in all three soils when incubated at 10 or 15% soil moisture content, i.e. within the range naturally occurring under the Mediterranean climate of Algeria. CONCLUSION: This study shows that, although soil microbiota can adapt to rapid mineralisation of 2,4‐D, this microbial activity is strongly dependent on climatic parameters. It suggests that only limited pesticide biodegradation occurs under Mediterranean climate, and that arable Mediterranean soils are therefore fragile and likely to accumulate pesticide residues. Copyright © 2009 Society of Chemical Industry     

Persistence of pyrazosulfuron in rice-field and laboratory soil under Indian tropical conditions

BACKGROUND: Pyrazosulfuron ethyl, a new rice herbicide belonging to the sulfonylurea group, has recently been registered in India for weed control in rice crops. Many field experiments revealed the bioefficacy of this herbicide; however, no information is available on the persistence of this herbicide in paddy soil under Indian tropical conditions. Therefore, a field experiment was undertaken to investigate the fate of pyrazosulfuron ethyl in soil and water of rice fields. Persistence studies were also carried out under laboratory conditions in sterile and non‐sterile soil to evaluate the microbial contribution to degradation. RESULTS: High‐performance liquid chromatography (HPLC) of pyrazosulfuron ethyl gave a single sharp peak at 3.41 min. The instrument detection limit (IDL) for pyrazosulfuron ethyl by HPLC was 0.1 µg mL^?1, with a sensitivity of 2 ng. The estimated method detection limit (EMDL) was 0.001 µg mL^?1 and 0.002 µg g^?1 for water and soil respectively. Two applications at an interval of 10 days gave good weed control. The herbicide residues dissipated faster in water than in soil. In the present study, with a field‐soil pH of 8.2 and an organic matter content of 0.5%, the pyrazosulfuron ethyl residues dissipated with a half‐life of 5.4 and 0.9 days in soil and water respectively. Dissipation followed first‐order kinetics. Under laboratory conditions, degradation of pyrazosulfuron ethyl was faster in non‐sterile soil (t_1/2 = 9.7 days) than in sterile soil (t_1/2 = 16.9 days). CONCLUSION: Pyrazosulfuron ethyl is a short‐lived molecule, and it dissipated rapidly in field soil and water. The faster degradation of pyrazosulfuron in non‐sterile soil than in sterile soil indicated microbial degradation of this herbicide. Copyright © 2012 Society of Chemical Industry     

Fate of metsulfuron-methyl in soils in relation to pedo-climatic conditions

The dependence of the behaviour of metsulfuron-methyl on soil pH was confirmed during incubations under controlled laboratory conditions with two French soils used for wheat cropping. The fate of [¹⁴C] residues from [triazine-¹⁴C]metsulfuron-methyl was studied by combining different experimen-tal conditions: soil pH (8·1 and 5·2), temperature (28 and 10°C), soil moisture (90 and 50% of soil water holding capacity) and microbial activity (sterile and non-sterile conditions). Metsulfuron-methyl degradation was mainly influenced by soil pH and temperature. The metsulfuron-methyl half-life varied from five days in the acidic soil to 69 days in the alkaline soil. Under sterile conditions, the half-life increased in alkaline soil to 139 days but was not changed in the acidic soil. Metsulfuron-methyl degradation mainly resulted in the formation of the amino-triazine. In the acidic soil, degradation was characterised by rapid hydrolysis giving two specific unidentified metabolites, not detected during incubations in the alkaline soil. Bound residues formation and metsulfuron-methyl mineralisation were highly correlated. The extent of bound residue formation increased when soil water content decreased and was maximal [48 (±4)% of the applied metsulfuron-methyl after 98 incubation days] in the acidic soil at 50% of the water holding capacity and 28°C. Otherwise, bound residues represented between 13 and 32% of the initial radioactivity. © 1998 SCI     

Laboratory studies on formation of bound residues and degradation of propiconazole in soils

Laboratory studies on the formation of bound residues and on the degradation of the triazole fungicide propiconazole were conducted in two different soils. Soils treated with 14C-propiconazole were incubated at 22 degrees C and extracted exhaustively with a solvent at each sampling date until no further propiconazole was extracted. The solvent-extractable residues were used to measure propiconazole remaining in the soil, and the extracted soils were used to investigate bound residues of propiconazole. Mineralization of propiconazole was investigated by measuring [14C]carbon dioxide evolved from the soil samples. Formation of bound residues of propiconazole was higher in silty clay loam soil than in sandy loam soil, giving approximately 38 and 23% of the applied 14C, respectively. In contrast, the rates of degradation and mineralization of propiconazole were lower in silty clay loam soil than in sandy loam soil. Decreased extractability of the 14C residues with incubation time was observed with increased formation of bound residues. When the propiconazole remaining in the solvent-extractable residues was quantitatively measured by high-pressure liquid chromatographic analysis, the half-life value in sandy loam soil was about 315 days, while the half-life in silty clay loam soil exceeded the duration of the 1 year experimental period. Increased formation of bound residues was observed as propiconazole degraded with incubation time, suggesting that degradation products are involved in the formation of bound residues. Our study suggests that the formation of bound residues of propiconazole contributes to the persistence of this fungicide in soil.     

三江源区土地利用方式对土壤氮素特征的影响

以三江源区曲麻莱县高寒草甸草原、退化高寒草甸草原、退化高寒草原和人工草地4种土地利用方式为研究对象,研究了不同土地利用方式的土壤全氮、有效氮、铵态氮、硝态氮、无机氮总量及比例,结果表明:4种利用方式土壤的氮素含量均处于较低水平,在0~10 cm土层,土壤全氮与有效氮含量表现出相似的规律性,人工草地最高,退化高寒草甸草原最低。与高寒草甸草原相比,退化高寒草甸草原0~10 cm土层全氮和有效氮含量分别降低了52.4%和76.2%,而10~40 cm土层的全氮和有效氮含量却明显增加。对土壤铵态氮和硝态氮含量的研究结果进一步表明,研究区域土壤中无机氮以硝态氮为主,退化导致0~10 cm土层的铵态氮和硝态氮含量降低,退化和人工种植均导致0~10 cm土层硝态氮含量明显降低,而10~20 cm和20~40 cm土层的硝态氮含量明显升高,且这两个土层之间差异不显著,40~60 cm土层又明显降低。因此,退化和人工种植均导致土壤硝态氮沿土壤剖面淋溶下移,并且淋溶主要发生在0~40 cm深度的土壤中。土壤无机氮总量与硝态氮表现出相似的规律性,对土壤无机氮总量和比例的研究也表明退化加剧了土壤氮素的矿化过程。     

The effect of initial concentration of carbofuran on the development and stability of its enhanced biodegradation in top‐soil and sub‐soil

Carbofuran was incubated in top‐soil and sub‐soil samples from a pesticide‐free site at a range of initial concentrations from 0.1 to 10 mg kg⁻¹. Amounts of the incubated soils were removed at intervals over the subsequent 12 months, and the rate of degradation of a second carbofuran dose at 10 mg kg⁻¹ was assessed. An applied concentration as low as 0.1 mg kg⁻¹ to top‐soil resulted in more rapid degradation of the fresh addition of carbofuran for at least 12 months. The degree of enhancement was generally more pronounced with the higher initial concentrations. When the same study was conducted in sub‐soil samples from the same site, an initial dose of carbofuran at 0.1 mg kg⁻¹ resulted in only small increases in rates of degradation of a second carbofuran dose. However, degradation rates in the sub‐soil samples were, in many instances, considerably greater than in the corresponding top‐soil samples, irrespective of pre‐treatment concentration or pre‐incubation period. Initial doses of 0.5 mg kg⁻¹ and higher applied to sub‐soil successfully activated the sub‐soil microflora. Application of the VARLEACH model to simulate carbofuran movement through the soil profile indicated that approximately 0.01 mg kg⁻¹ of carbofuran may reach a depth of 70 cm 400 days after a standard field application. The results therefore imply that adaptation of the sub‐soil microflora (c 1 m depth) by normal field rate applications of carbofuran is unlikely to occur. In experiments to investigate this in soils exposed to carbofuran in the field, there was no apparent relationship between top‐soil exposure and degradation rates in the corresponding sub‐soils. The results further confirmed that some sub‐soil samples have an inherent capacity for rapid biodegradation of carbofuran. The high levels of variability observed between replicates in some of the sub‐soil samples were attributed to the uneven distribution of a low population of carbofuran‐degrading micro‐organisms in sub‐surface soil. There was no apparent relationship between soil microbial biomass and degradation rates within or between top‐soil and sub‐soil samples. © 2001 Society of Chemical Industry