花岗岩崩岗区不同土层的侵蚀水动力学特征

土壤剥蚀率是单位时间单位面积水流剥蚀土壤的质量,定量研究崩岗不同土层土壤剥蚀率对预测土壤剥蚀过程及建立崩岗侵蚀物理模型具有重要的理论和实践意义。针对湖北通城花岗岩崩岗区发育的表土层、红土层、砂土层、碎屑层,采用不同坡度(8.8%、17.6%、26.8%、36.4%、46.6%)和不同流量(0.2 Ls~(-1)、0.4 Ls~(-1)、0.6 Ls~(-1)、0.8 Ls~(-1)、1.0 Ls~(-1))相结合的室内放水冲刷试验,分析表土层、红土层、砂土层、碎屑层土体土壤剥蚀率与水动力学参数之间的关系,初步探讨花岗岩崩岗侵蚀的水动力学机制。结果表明:在一定坡度条件下,土壤剥蚀率随径流流量的增大而增大,且各土层土壤剥蚀率存在很大差异,碎屑层土壤剥蚀率最大,砂土层次之,表土层最小;在相同流量条件下,各土层土壤剥蚀率均随冲刷时间的延长逐渐降低并趋于稳定;径流剪切力、水流功率对崩岗各土层土壤剥蚀率的影响均可采用线性方程很好地描述(R~20.926),相比用单位水流功率拟合的多项式方程的相关性(R0.830)要高,径流剪切力和水流功率均可作为描述崩岗各土层土壤侵蚀的水动力学参数。表土层、红土层、砂土层、碎屑层的临界径流剪切力依次减小,分别为0.28Pa、0.13Pa、0.10Pa、0.07Pa,各土层土壤细沟可蚀性参数差异明显,碎屑层的最大,砂土层次之,表土层最小。因此,在崩岗垂直结构上,随着土层深度的增加,土体抵抗径流剥蚀的能力逐渐减弱。     

花岗岩崩岗不同层次土壤抗冲性及其影响因素

针对湖北通城花岗岩崩岗区发育的淋溶层(A层)、淀积层(B层)、过渡层(BC层)以及母质层(C层),采用不同坡度(8.8%,17.6%,26.8%,36.4%,46.6%)和不同流量(0.2,1.0L/s)相结合的室内放水冲刷试验,分析崩岗各层次土壤的抗冲性指数,初步探讨花岗岩崩岗不同坡度及各层次土壤主要理化性质对抗冲性的影响。结果表明:(1)湖北通城县崩岗土壤A层、B层、BC层以及C层的理化性质存在较大差异。(2)当流量一定时,随着坡度的增大,土壤的抗冲性指数均表现为减小的趋势;当坡度一定时,大流量条件下土壤的抗冲性指数较小;在相同坡度和流量条件下,土壤的抗冲性指数均由A层向C层递减,说明A层抗冲性能最好,C层最差。(3)各层次的土壤抗冲性指数随坡度呈显著的线性递减关系(p0.05),土壤的抗冲性能随坡度的增加而减小,其中A层回归方程的系数项绝对值最大,常数项也最大,说明A层的抗冲性随坡度的变化最快,抗流水侵蚀能力最强,土壤流失量最少。(4)土壤抗冲性与粉粒含量、黏粒含量、水稳性指数、渗透系数呈正相关;与土壤干密度、砂粒含量呈负相关,其中和干密度以及水稳性指数的相关性较高,表现为极显著相关;土壤抗冲性与有机质含量、CEC、游离氧化铁呈正相关,与土壤pH呈负相关,其中与有机质含量的相关性系数大于0.9,相关性极显著。     

鄂东南花岗岩崩岗崩壁土壤水分特征研究

针对鄂东南地区崩岗崩壁不同层次的土壤水分特征进行研究,旨在区分各层次土壤水分与崩岗侵蚀的联系。结果表明,崩壁不同层次的土壤性质存在差异,同时土壤水分特征曲线有一定的变化规律,表土层和红土层持水能力强于斑纹层和碎屑层,土壤水分特征曲线用Gardner模型拟合有较好效果。利用TDR对崩壁水分含量进行测定发现,表土层的含水量从上到下呈现逐渐增大的趋势,红土层至碎屑层含水量逐渐变小。崩壁纵剖面由里到外逐渐减小,且表层土壤水平方向上的土壤含水量变化量要大于剖面底层。     

水土化学作用对崩岗土体抗剪特性的影响

【目的】探究水土化学作用对花岗岩崩岗区崩壁土体抗剪特性的影响,为阐明花岗岩崩岗侵蚀的成因机理提供理论依据。【方法】以福建省长汀县典型崩岗区崩壁土体(红土层、砂土层和碎屑层)为研究对象,分析了经不同离子浓度(0.005、0.01和0.1 mol L^-1)和离子类型(Na⁺和K⁺)的盐溶液交换处理后崩岗3个土层的土体抗剪特性(偏应力、黏聚力和内摩擦角)。【结果】红土层的偏应力、黏聚力和内摩擦角均显著高于砂土层和碎屑层。随着溶液浓度的增加,K⁺体系下崩岗3个土层的黏聚力显著增加,其中红土层增幅最大,增加了17.39%,Na⁺体系则表现出相反趋势;2种离子体系下土体的内摩擦角总体差异不显著。K⁺体系下崩岗3个土层的偏应力和黏聚力均显著大于Na⁺体系,其中,K⁺处理的红土层、砂土层和碎屑层的黏聚力比Na⁺处理的分别高9.99%、3.37%和9.65%,但2种离子对内摩擦角的影响总体并不显著。水土化学作...     

鄂东南崩岗剖面土壤水分特征曲线及模拟

崩岗是我国南方花岗岩地区破坏性极强的水土流失类型。以鄂东南地区两个典型的崩岗剖面为对象,探讨崩岗剖面包括表土层、红土层、斑纹层和碎屑层的土壤水分特征及方程拟合过程,明确崩岗发生的水分运动机理。结果表明:崩岗土壤释水量伴随吸力呈规律性变化,其中斑纹层和砂土层低吸力时脱水能力大于表土层和红土层,高吸力时各个层次土壤水分特征曲线趋于平缓。利用当量孔隙的计算发现不同土层的孔隙变化也存在变化规律,均体现为由表土层至碎屑层土壤大孔隙比例增加而毛管孔隙减少。选取van Genuchten方程和Gardner方程对崩岗剖面土壤实测数据进行了曲线拟合,同时进行了两个方程的拟合评价,R2基本在0.9以上,同时残差平方和的数量级在10-3和10-5之间。研究表明,van Genuchten方程参数能够较好地拟合崩岗表土层和红土层土壤水分特征曲线的实测数据,误差相对较小,而Gardner方程适用于斑纹层和碎屑层土壤。     

花岗岩红壤丘陵区崩岗土体界限含水量的温度效应研究

水分和温度会显著影响花岗岩红壤的力学状态,是崩岗发生和发展的两大驱动因素.以崩壁三个土层土壤:红土层、砂土层和碎屑层为研究对象,在15、25、40和60℃温度条件下对三个土层土壤的液塑限和结合水含量开展研究.结果表明:红土层的液限、塑限和塑性指数均高于砂土层和碎屑层,碎屑层土壤的液塑限最小.崩岗土壤的液塑限与细黏粒、有...     

基于分形理论模拟花岗岩崩岗剖面土壤水分特征曲线

崩岗是我国南方花岗岩地区特殊的土壤侵蚀现象,给山区经济造成了严重的影响.为了探索南方花岗岩地区崩岗侵蚀剖面的水分特性,明确水分与崩岗发育的关系,本研究采用野外调查采样与室内分析的方法,运用土壤粒径分形理论,并结合Brooks and Corey模型,模拟花岗岩崩岗剖面土壤水分特征曲线.选择通城县花岗岩崩岗剖面5个层次(表土层、红土层、过渡层、砂土层和碎屑层)采集土样,通过对土壤粒径分布和土壤含水量的测定,分析分形维数与土壤粒径之间的关系.同时,应用土壤粒径分形理论,模拟土壤水分特征曲线,基于估算结果与实测结果的比较,探讨分形方法估算土壤水分特征曲线的可行性.结果表明:崩岗剖面土壤黏粒质量分数越大,土壤粒径分维值越大;土壤粒径分维值越大,土壤水分特征曲线的分维值则越大,两者之间线性关系较好;运用分形理论,模拟土壤水分特征曲线的预测值与实测值具有良好的一致性,模拟结果的精度随土层的深度增加而增加,模拟效果以土壤黏粒和粉粒质量分数较少、砂粒质量分数较多的土壤效果较好.研究结果为花岗岩崩岗机理的探索奠定了基础,对崩岗水分的研究具有指导意义.     

干湿循环作用下崩岗土体抗拉强度的衰减性分析

针对干湿循环影响下崩岗土体崩壁出现失稳等问题,通过开展室内单轴抗拉试验,研究了湖北通城地区不同干湿循环作用下崩岗土体抗拉强度的变化规律。结果表明:崩岗土体的抗拉强度随着干湿循环次数的增加逐渐衰减,最后逐渐趋于稳定,且不同层次土壤的抗拉强度衰减主要集中在前3个干湿循环周期,表土层、红土层、过渡层和砂土层抗拉强度衰减比例分别达到90%,82%,83%,90%,且不同层次土壤的抗拉强度总体表现为过渡层>红土层>表土层>砂土层。并通过考虑崩岗不同层次土体深度和干湿循环次数的共同影响,建立了抗拉强度衰减预估模型,且抗拉强度模型预测值与实测值有较高的相关关系(R^2=0.97),该模型对研究崩岗不同层次土体抗拉强度衰减机制具有指导意义。     

坡面水流分离崩岗崩积体土壤的动力学特征

利用变坡式水槽,在坡度(20°,25°,30°,35°,40°)和流量(1.1,2.2,3.3,4.4,5.5L/min)下进行崩岗崩积体土壤的分离试验。结果表明:流量对土壤分离速率的作用大于坡度,土壤分离速率与坡度及流量呈线性相关;水深对土壤分离速率的影响大于坡度,土壤分离速率与坡度及水深呈线性相关;土壤分离速率与水流流速呈指数函数关系;水流剪切力、水流功率及单位水流功率与土壤分离速率之间的关系均为线性关系,其中,水流功率和水流剪切力可以很好地描述崩积体的土壤分离速率。     

花岗岩风化壳的层次特性对土壤侵蚀及其防治措施的影响

花岗岩发育的土壤剖面具有显著的层次结构,各层次的颗粒组成、有机质含量都有很大的差异。不同层次土壤的抗侵蚀性能也因此有很大的差异,从表土层往下逐渐降低,砂土层最低,而到碎屑层又有所提高。随着上层土壤被侵蚀冲刷掉,下层土壤依次出露,土壤侵蚀类型也随之发生变化,依次会发生面蚀——沟蚀——崩岗侵蚀。土壤侵蚀模数与侵蚀强度会逐渐增强,到碎屑层出露时有所降低,土壤侵蚀程度则会不断加深。不同层次出露,土壤侵蚀类型发生变化,因此治理措施也应随之变化：表土层与红土层出露时,主要是提高土壤入渗率,从而减少土壤侵蚀量;砂土层出露时,以减少水流对土壤的直接冲刷作用为主;碎屑层出露时,以植被恢复为主。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.