黄土高原藓结皮覆盖土壤导水性能和水流特征

生物结皮具有特殊的水文物理性质,为探究其对土壤水分渗透性和水流特征的影响,以黄土高原风沙土和黄绵土上3种典型地表覆盖类型(裸地、藓结皮、藓结皮-草本植物混合)为对象,采用环刀法和染色示踪法对其导水性质与水流特征进行探究。结果表明:藓结皮对2种土壤类型0~5 cm土层土壤理化性质影响较大,与裸地相比土壤容重降低了9.85%~10.00%,土壤黏粒含量增加了1.01~1.29倍,表层有机质含量提高了2.73~3.02倍;藓结皮使0~5 cm土层土壤饱和导水率降低了61.32%~88.89%,而在5~10 cm土层饱和导水率则有明显上升。另外,由于草本植物的影响,藓结皮-草本植物0~5 cm土层与藓结皮土壤相比土壤饱和导水率提高了1.32~6.43倍;黄绵土藓结皮与藓结皮-草本植物的染色面积比均高于裸地,且水分下渗深度增加了10 cm,而风沙土藓结皮与风沙土裸地的染色面积比差异不明显。综上所述,藓结皮和藓结皮-草本植物的存在改变了表层土壤水分渗透性以及水流运动特征和水分下渗深度,影响着黄土高原土壤水分保持和生态恢复。     

黄土地与沙地生物结皮的发育特征及其生态功能异同

基于课题组已有研究成果,选取陕北水蚀风蚀交错区内气候条件相同但土壤质地迥异的试验区,探讨黄土地和沙地生物结皮发育特征及其生态效应的异同。结果表明:(1)苔藓结皮是2种土地生物结皮的重要类型,其中,黄土地的优势藓种为尖叶对齿藓[Didymodon constrictus(Mitt.)Saito.]、真藓(Bryum argenteum Hedw.)、狭网真藓(B.algovicum Sendt.);沙地的优势藓种为黄色真藓(B.pallescens Scheich.)、弯叶真藓(B.recurvulum Mitt.)、银叶真藓(B.argenteum Hedw.)。沙地乔灌植物下生物结皮盖度(77.5%)、厚度(11.8 mm)及容重(1.9 g·cm~(-3))均高于黄土地生物结皮,而黄土地多年生草本植物下生物结皮抗剪强度(26.5 k Pa)高于沙地生物结皮,总体上,沙地生物结皮发育的更好。(2)黄土地的入渗增幅和0~200 cm剖面的平均土壤含水率增幅均显著高于沙地(P0.05),且在旱季和雨季其0~200 cm剖面的平均土壤含水率增幅分别比沙地高1.4%和1.9%。(3)两地生物结皮均表现出了较好的减蚀作用,其减蚀效率分别为81.0%和90.6%。     

荒漠草原地区生物结皮的微生物群落与产漆酶细菌分离纯化

为了解生物结皮的微生物组成及影响碳素循环的微生物,文中在采用高通量技术研究西夏王陵生物结皮的微生物群落结构的基础上,采用选择培养基从生物结皮中分离产漆酶的微生物。研究结果表明:细菌的多样性显著高于真菌;变形菌门、酸杆菌门、蓝细菌门、放线菌门、拟杆菌门是绝对优势的细菌门类,子囊菌门和担子菌门是绝对优势的真菌门类;微鞘藻属、藓杆菌属、鞘氨醇单胞菌属、甲基杆菌属在细菌中占比较大的属,链格孢属、菌刺孢属、热子囊菌属、亚脐菇属等是主要的真菌,这些类群在稳定生物结皮结构、碳氮循环、有机物代谢等方面发挥了重要作用。以愈创木酚为唯一碳源从生物结皮中获得能利用愈创木酚的细菌10株,基于丁香醛联氮氧化的颜色反应,筛选出产漆酶能力最强的菌株C01和C06,基于16S rDNA序列的分子鉴定表明,两菌株均为芽孢杆菌。     

寡营养细菌对古尔班通古特沙漠土壤环境的影响

利用从古尔班通古特沙漠生物结皮中分离的1株寡营养细菌制成的菌剂,喷洒在流沙表面,分析寡营养细菌对沙漠土壤微生物、酶活性、土壤养分及生物结皮形成的影响。结果表明：①喷洒寡营养细菌菌剂,提高各层土壤主要微生物数量,其中显著（P〈0.05）提高了0～2 cm土层的细菌和放线菌数量及2～5 cm层的寡营养细菌数量;②对不同土壤...     

生物结皮富集营养元素和重金属元素的空间分异特性

通过测定库布齐沙漠腹地达拉特旗火力发电厂附近沙地中不同年代人工结皮和下层土壤中重金属和营养元素的含量,旨在研究生物结皮富集重金属和营养元素的能力,富集结果及空间差异性。通过单因素方差分析(ANOVA)和比较,得出以下结论:在水平格局,结皮中的重金属和营养元素含量表现为:Cr>Pb>Cu>Cd和C>K>N>P的顺序关系,相同发育年代结皮中的重金属和营养元素含量均表现为:藓结皮>藻结皮>物理结皮;不同发育年代结皮中各种重金属和营养元素含量均表现为随着发育时间的增加而增加;在垂直格局,各类型结皮中重金属和营养元素含量均表现为随着土壤垂直深度增加而降低。     

黄土地表生物结皮对土壤贮水性能及水分入渗特征的影响

采用双环法对山西省偏关县3种结皮覆盖下(苔藓藻结皮、藻结皮和薄层藻结皮)土壤的贮水性能和渗透特征进行了对比研究.结果表明:不同结皮覆盖下土壤的贮水能力受结皮厚度和孔隙度状况的影响较大,0～10 cm土层饱和贮水量为502.69～525.80 t/hm2 ,滞留贮水量为169.71～198.29 t/hm2;初渗速率的变化范围为5. 19～11.10 mm/min,无结皮最高,苔藓藻结皮最低;稳渗速率变化范围为1.6 7～2.67 mm/min.采用的3种入渗模型(Kostiakov模型、Horton模型和Ph ilip模型)中Horton模型的拟合值更接近于实测值, 决定系数R2在0.98～0.99,更适用于描述本研究区具有生物结皮土壤的入渗特征.     

荒漠生物结皮研究中的几个问题

生物结皮在干旱区生态系统中扮演着一个关键的角色,它可以影响干旱区土壤的结构、功能、生产力,包括土壤稳定性、土壤保水力、碳、氮的固定和土壤的肥力等。结合国内外生物结皮的研究,提出生物结皮的影响因子、生物结皮与周围植物的关系、生物结皮形态的变化与分布的异质性等几个问题并进行了讨论。     

黄土丘陵沟壑区生物土壤结皮理化性质

为了解黄土丘陵沟壑区生物结皮发育过程中理化性质的变化,分析了不同盖度水平结皮的机械组成、养分、化学元素以及土壤因子与生物结皮盖度的相关性和结皮发育过程中土壤因子之间的相互作用。结果表明:随着结皮的发育,土壤有机质、全氮、全钾、速效氮、速效磷、速效钾含量均呈增长趋势,pH值则相反;土壤细砂粒含量(0.25~0.05 mm)减少,粗粉粒(0.05~0.01 mm)含量增加;土壤中的化学元素含量也呈增加趋势。土壤有机质、全氮、全磷、pH值、细砂粒、粗粉粒、Ca,Mg,Na和Fe含量与生物结皮的形成发育密切相关(P0.01)。此外,各土壤因子之间存在着相关关系,特别是粗粉粒含量和pH值,与其他因子有显著的相关性。     

土壤微生物在生物结皮形成中的作用及生态学意义

在荒漠地区的固定、半固定沙地和流动沙地上,微生物、藻类植物及地衣、苔藓植物能参与并形成生物结皮,其在干旱和半干旱荒漠地区具有重要生态意义。其中土壤微生物因其极强的适应性和生存能力,在生物结皮形成各阶段都起着积极的作用。土壤微生物的生长和活性与土壤酶活性的变化具有良好的相关性,它的组成、分布和数量因沙丘类型和沙土层深度的不同而有所变化,也受到季节和植被的影响。土壤微生物的生理代谢活动及数量变化可以改变沙土表面理化性质,在土壤结皮的形成、植物营养的转化过程中发挥积极作用,为植物生长创造了良好的条件。     

荒漠结皮对土壤水分状况的影响

本研究针对鄂尔多斯沙地生物结皮进行调查 ,利用人工喷水模拟降雨分析结皮对土壤入渗性能的影响。研究表明 :生物结皮能显著地降低土壤水分的入渗速率。在去掉结皮时 ,表层下 5 cm处的土壤含水量在 1 0分钟时即开始显著增加 ,而有结皮时 ,此处的含水量则在 1 5分钟时才开始显著增加。利用圆盘入渗仪测定有结皮和无结皮条件下的土壤饱和导水率表明 :固定沙丘间地有生物结皮的土壤饱和导水率范围是 :2 9.1 0 - 82 .2 1 mm/ h;半固定沙丘有微弱结皮时饱和导水率为 1 43.5 4 - 2 30 .2 5 ;去掉结皮后土壤的饱和导水率可显著上升数倍 ,无结皮的流沙的饱和导水率最高。     

The degradation of methazole in soil. I. Effects of soil type,soil temperature and soil moisture content

[¹⁴C]-Labelled methazole was incubated in six soils at 25°C and with soil moisture at field capacity. Under these conditions, methazole was unstable, the concentration declined following first-order kinetics with half-life values in the soils ranging from 2.3 to 5.0 days. The main degradation product was 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU) which was more stable than the parent compound. After about 160 days, DCPMU accounted for 30 to 45% of the initial methazole concentration. Degradation of methazole and DCPMU was affected by soil temperature and moisture content. With methazole, half-lives in one soil at field capacity moisture content and temperatures of 25, 15 and 5°C were 3.5, 8.7 and 31.1 days respectively. The half-life at 25°C was increased to 5.0 days at 50% of field capacity and 9.6 days at 25% of field capacity. A proportion of the initial radioactivity added to the soil could not be extracted and this proportion increased with time. After 160 days this unextractable radioactivity accounted for up to 70% of the amount applied.     

Residual phytotoxic activity of pethoxamid in soil and its concentration in soil water under different soil moisture conditions

The relationship between the residual phytotoxic activity of pethoxamid (2-chloro- N -[2-ethoxyethyl]- N- [2-methyl-1-phenyl-1-propenyl] acetamide) on rice ( Oryza sativa cv. Kiyohatamochi) seedlings and its behavior in soil was investigated under different moisture conditions. The phytotoxic activity of pethoxamid on the shoot growth of rice seedlings in soil was higher in 80% soil moisture content than in 70% and 60% soil moisture contents. The phytotoxic activity in soil in 70% and 80% soil moisture conditions decreased with the increasing time after application, but the phytotoxic activity was slight in 50% soil moisture conditions at any given time after application. The residues of pethoxamid in soil water, the amount adsorbed on soil solid, and the amount in total soil was reduced with the time after application in a similar manner among these soil moisture conditions. The residual phytotoxic activity of pethoxamid on the shoot growth of rice seedlings in soil was more highly correlated with the concentration in soil water than with the amounts adsorbed on soil solid and in total soil. The partition coefficients between the amounts of pethoxamid adsorbed on soil solid and its concentration in soil water were similar among the soils with different moisture conditions at each day, and the partition coefficient increased with the time after application. These results suggested that the residual phytotoxic activity of pethoxamid in soil depends on the decreasing concentration of pethoxamid in soil water with time, except in low soil-moisture conditions, which were insufficient for seedling growth.     

Residual thenylchlor concentration in soil water and its phytotoxic activity in soil

The phytotoxic activity of soil-applied thenylchlor (2-chloro- N -[3-methoxy-2-thenyl]-2',6'-dimethylacetanilide) on the growth of rice seedlings and its behavior in two different types of soil, Ryugasaki soil and Tsukuba soil, after application was investigated with emphasis on the concentration in the soil water. The greatest inhibition of thenylchlor on the growth of rice seedlings was found immediately after application to both the Ryugasaki and Tsukuba soils. The phytotoxic activity decreased with time in both soils. However, the rate of decrease in phytotoxic activity was slower in the Ryugasaki soil than in the Tsukuba soil. The concentration of thenylchlor in soil water, the amount adsorbed on the soil solid, and the amount in the total soil reduced with time after application to both soils. The amount of thenylchlor adsorbed on the soil solid phase was more persistent than that in the soil water in both soils and the concentration in the soil water was higher in the Ryugasaki soil than in the Tsukuba soil at any given time. The residual phytotoxic activity of thenylchlor on the growth of the rice seedlings in the soil was highly correlated with its concentration in the soil water but not with the amount in the total soil. These results suggested that the residual phytotoxic activity of thenylchlor in the soil is determined by its concentration in the soil water after application.     

关中地区耕作方法与土壤紧实度时空变异及其效应分析

为了探明关中地区土壤紧实度的基本情况,揭示长期旋耕方法对于土壤紧实度的作用与影响,在关中头道塬设置了旋耕和深翻处理、休闲和种植小麦处理的定位观察试验,在小麦各生育阶段分别监测了0～40 cm剖面范围内土壤紧实度变异情况,分析了影响土壤紧实度的因子等.结果表明:播前施行旋耕土壤紧实度较高,尤其是在15～40 cm表现得较为明显,限制了作物根系伸长;深耕松土的效应在整个小麦生育期间都能得到明显的体现.实验证实了生产上现行的旋耕方法具有明显地导致土壤紧实化的问题.土壤紧实度与含水量明显相关,影响程度随土壤深度的增加而增大;土壤紧实度对含水量的敏感反应意味着土壤干燥化会对作物生长带来干旱和机械双重胁迫;同时随着紧实度的增加土壤内部温度变化幅度也在增大.可见现行旋耕方法使得土壤不良环境缓冲性降低,对于降水或者灌溉的依赖性在增强,土壤已经处于明显疲劳状态.     

秸秆覆盖对农田黑土春季地温的影响

通过黑土区田间长期定位试验,研究了秸秆覆盖度对太阳反射和土壤含水量的影响,进而探讨了其对土壤温度的调控作用。在作物出苗前,秸秆覆盖度免耕(覆盖度70%)>少耕(覆盖度10%)>旋松(覆盖度0%)。研究结果表明:免耕、少耕和旋松的累计反射强度依次递减,反射辐射强度越大土壤温度越低;免耕具有较高的质量含水量,质量含水量均与地温存在显著的负相关关系。     

Pencycuron dissipation in soil: effect of application rate and soil conditions

Dissipation of the fungicide pencycuron was examined under controlled laboratory conditions in clay loam soils from rice cultivated fields of alluvial soil (Typic udifluvent) and coastal saline soil (Typic endoaquept) at field rate, twice the field rate and 10 times the field rate with and without decomposed cow manure maintained at 60% of maximum water-holding capacity (WHC) and waterlogged soil condition. The half-life values depended on the initial concentrations of pencycuron. Pencycuron, in general, degraded fastest in coastal saline soil and in soil amended with decomposed cow manure at 60% of maximum WHC of soil.     

Characterization of residues in soybeans grown in soil treated with 1,3-dichloropropene soil fumigant

The metabolism of cis- and trans-1,3-dichloropropene (1,3-D) was studied in soybean plants grown in soil treated 24 days prior to planting with [U-¹⁴C]E- and Z-1,3-dichloropropene at 380 liters ha^?1. Isolation and identification of the ¹⁴C residue from soybean plants at 84 days (forage) and 176 days (mature) after application showed that no 1,3-dichloropropene or its putative metabolites, 3-chloroallyl alcohol and 3-chloroacrylic acid, could be detected in any of the tissues. The components of the ¹⁴C residue included major plant constituents (i.e. fatty acids, protein, pigments, organic acids, sucrose and other carbohydrates, and lignin).     

Simulation of herbicide persistence in soil .III. Propyzamide in different soil types

The effects of soil temperature and soil moisture content on the rate of degradation of propyzamide in five soils were examined under controlled laboratory conditions. Half-lives in soils incubated at field capacity varied from 23 to 42 days at 25°C and from 63 to 112 days at 15°C. The variation in half-life at 25°C and 50% of field capacity was from 56 to 94 days. When the laboratory data were used in conjunction with the relevant meteorological records and soil properties in a computer simulation program, predicted degradation curves for propyzamide in four of the soils in micro-plots were in close agreement with those observed. Use of the program to predict residues of propyzamide in the fifth soil at crop maturity in a series of field experiments concerned with continuity of lettuce production gave values fairly close to those observed when appropriate corrections were made for initial recoveries.