丛枝菌根对有机污染土壤的修复作用及机理

丛枝菌根(AM)是丛枝菌根真菌(AMF)与植物根系相互作用的互惠共生体,能改良土壤结构,增强植物抗性.自然界中已知的AMF有170多种,分布广泛,且可与大多数植物共生.利用AM修复有机污染土壤正成为一个崭新的研究方向.本文综述了AM对多环芳烃、酞酸脂、石油和农药等一些典型有机污染物污染土壤的修复作用.AM修复有机污染土壤的机理主要包括:AMF代谢有机污染物;AM分泌酶,降解污染物;AM影响根系分泌作用,并促进根际微生物对有机污染物的降解;AMF宿主植物吸收积累污染物.AM修复研究中,高效AMF的筛选、复合菌种效应、土壤老化、AM作用下植物对有机污染物的吸收积累等几方面仍有待于深入研究.     

贵州山区土壤中微生物担是能源物质碳流动的源与汇

在传统的农业生态系统的研究中 ,主要精力放在营养物 (如Ｎ)上 ,认为它们是限制生产力的因素 ;而往往忽略了土壤中碳的重要性 ,认为收获不受Ｃ限制的影响。然而 ,碳循环中的有机碳的分解作用部分控制着出现在地表下和显露在地表上的农业过程[4]。土壤中所储存的有机质 ,其数量既反映土壤从植物残留物的输入所获得的有机质与微生物群落的能量和营养需求之间的平衡 ,又反映植物对营养物的需求与有机质分解作用之间的平衡。因此 ,土壤中碳的平衡能反映出有机质中能量物质的储存[5]。大部分由光合作用形成的碳 ,是通过地表下的生态系统来流动的[…     

The Growth Response of Ecotypes of Holcus lanatus L. from Different Soil Types in Northwestern Europe to Phenolic Acids

Abstract: Phenolics are often discussed in relation to either allelopathy or to herbivory. This work, however, was undertaken to determine if phenolic acids benefit the growth of plants in very acid soils. We here report racial differences in the phenolic acid concentrations of the important plant species found in five sites within Central Scotland which covered a wide range in soil acidity from very acid (organic peats) to mildly acid (calcareous), and describe the racial differences in the growth response of Holcus lanatus L. to phenolic acids with increasing acidity. The total concentrations of phenolic acids in the ecotypes of important species were correlated with the total concentrations found in their respective soils. In general, the most phenolic-rich ecotypes of the five came from the organic acid soils (Flanders Moss [FM] and Sheriffmuir [SMB]). However, with the exception of ferulic acid which was a major component of both acid soils and their associated vegetation, individual simple phenolic acids extracted from either plants or soils were not consistently correlated. The addition of dry plant material collected from the five sites (0.5 g plant material 100 g^-1 soil) to the acid-organic Flanders Moss (FM) soil stimulated the growth of two ecotypes of Holcus (acid-mineral Sheriffmuir [SMM], calcareous Kinloch Rannoch [KR]) but the same litter addition in non-organic, less acidic or calcareous soil inhibited growth of these ecotypes. In hydroponic solutions, growth response of Flanders Moss (FM) and Kinloch Rannoch (KR) to pH and phenolic acid mixtures was interdependent: in acid solutions (pH 4.0) but not at pH 6.5 root elongation rates (RER) of both ecotypes, and shoot elongation rates (SER) of Flanders Moss (FM), increased after treatment with a mixture of seven commonly occurring phenolic acids.     

Managing soils for long-term productivity

Meeting the goal of long-term agricultural productivity requires that soil degradation be halted and reversed. Soil fertility decline is a key factor in soil degradation and is probably the major cause of declining crop yields. There is evidence that the contribution of declining soil fertility to soil degradation has been underestimated. <br>Sensitivity to soil degradation is implicit in the assessment of the sustainability of land management practices, with wide recognition of the fact that soils vary in their ability to resist change and recover subsequent to stress. The concept of resilience in relation to sustainability requires further elaboration and evaluation.<br>In the context of soil degradation, a decline in soil fertility is primarily interpreted as the depletion of organic matter and plant nutrients. Despite a higher turnover rate of organic matter in the tropics there is no intrinsic difference between the organic matter content of soils from tropical and temperate regions. The level of organic matter in a soil is closely related to the above and below ground inputs. In the absence of adequate organic material inputs and where cultivation is continuous, soil organic matter declines progressively. Maintaining the quantity and quality of soil organic matter should be a guiding principle in developing management practices.<br>Soil microbial biomass serves as an important reservoir of nitrogen (N), phosphorus (P) and sulphur (S), and regulates the cycling of organic matter and nutrients. Because of its high turnover rate, microbial biomass reacts quickly to changes in management and is a sensitive indicator for monitoring and predicting changes in soil organic matter. Modelling techniques have been reasonably successful in predicting changes in soil organic matter with different organic material inputs, but there is little information from the tropics. <br>Nutrient depletion through harvested crop components and residue removal, and by leaching and soil erosion accentuates the often very low inherent fertility of many soils in the tropics. An integrated approach involving inorganic and organic inputs is required where animal and plant residues are returned, as far as practicable. Chemical fertilizers alone cannot achieve long-term productivity on many soils and organic material inputs are required to maintain soil organic matter levels and crop productivity. A major research effort is required to develop improved strategies for halting and reversing soil degradation if long-term productivity is to be secured. <br>     

Degradation and Preservation of Vascular Plant-derived Biomarkers in Grassland and Forest Soils from Western Canada

The total solvent extracts (TSE) of mineral and organic horizons of selected soils and overlying vegetation were analyzed using gas chromatography–mass spectrometry (GC–MS) to determine the composition of solvent-extractable (‘free’) lipids in soils and to study the degradation and possible preservation of vascular plant-derived molecular markers (biomarkers) in soils. Major compound classes in the TSE of soils and vegetation included a homologous series of aliphatic lipids (alkanoic acids, alkanols, alkanes), steroids, and terpenoids. Characteristic patterns of aliphatic and cyclic biomarkers derived from the overlying, native vegetation were recognized in the associated soil samples indicating the preservation of lipids from the external waxes of vascular plants in the soil organic matter (SOM). The observed biomarker patterns in the grassland soils (Brown Chernozems) were similar to the compounds identified in their major source vegetation, Western Wheatgrass. A similar composition of biomarkers was observed in Aspen leaves and the soil horizons of the forest–grassland transition soil (Dark Gray Chernozem). The Lodgepole Pine needles yielded a characteristic pattern of diterpenoids that was also detected in leaf litter and the O horizon of the associated forest soil (Brunisol). The results demonstrate that solvent extractable biomarkers derived from vascular plants maintain their characteristic pattern of aliphatic and cyclic lipids despite ongoing degradation processes and are thus valuable molecular markers for the determination of the sources of SOM. Furthermore, the abundance of aliphatic wax lipids in plant material and soils decreased at higher rates than the steroids and terpenoids indicating the preferential degradation of aliphatic over cyclic biomarkers. Most of the plant-derived steroids and terpenoids identified in the soils were unaltered, preserved biomolecules as observed in the source vegetation, but minor amounts of their degradation products were also present. Oxidation products of plant sterols are reported here for the first time in soils. The detected alteration products of steroids and diterpenoids are consistent with the oxidative degradation of free cyclic biomarkers in decomposing plant material and soils.     

有机物料对滨海盐渍土重金属根际效应的影响 Ⅰ.土壤内源Zn形态分布

研究了排水条件下施用腐熟有机物料、种稻改良滨海盐渍土内源Zn形态分布。结果表明,单淹水使土中各形态Zn一定程度上向生物有效性较低的Zn形态转化,有效态Zn降低。土壤盐分量不同,明显影响无定形氧化铁结合态、紧结有机态以及硅酸盐矿物态Zn变化。种稻不施有机物料,根际交换态和硅酸盐矿物态Zn亏缺;碳酸盐结合态、氧化锰结合态和无定形氧化铁结合态Zn富集。根际Zn形态转化强度大于非根际,其有效态Zn量接近临界值并高于非根际。有机物料利于根际内外土壤中硅酸盐矿物态Zn的转化,低盐土壤根际更强烈。随有机物料用量增加,促使根际硅酸盐矿物态、碳酸盐结合态及氧化锰结合态Zn向交换态、紧结有机态和无定形氧化铁结合态Zn转化,低盐土壤较明显。     

Microbiological community analysis of vermicompost tea and its influence on the growth of vegetables and cereals

Vermicompost, the digestion product of organic material by earthworms, has been widely reported to have a more positive effect on plant growth and plant health than conventional compost. A study was conducted to investigate the effects of different vermicompost elutriates (aerated compost teas) on soils and plant growth. The teas were analyzed by chemical, microbiological, and molecular methods accompanied by plant growth tests at laboratory and field scale. The number of microorganisms in the teas increased during the extraction process and was affected by substrate addition. The vermicompost tea found to increase plant growth best under laboratory tests was applied to cereals (wheat and barley) and vegetables (Raphanus sativus, Rucola selvatica, and Pisum sativum) in a field study. The results revealed no effects of tea application on plant yield; however, sensoric tests indicated an improvement in crop quality. The soils from laboratory and field studies were investigated to detect possible microbial or chemical changes. The results indicated that minor changes to the soil microbial community occurred following tea application by foliar spray in both the laboratory-scale and field-scale experiments.     

有机物料对滨海盐渍土重金属根际效应的影响Ⅰ.土壤内源Zn形态分布

研究了排水条件下施用腐熟有机物料、种稻改良滨海盐渍土内源Ｚｎ形态分布．结果表明,单淹水使土中各形态Ｚｎ一定程度上向生物有效性较低的Ｚｎ形态转化,有效态Ｚｎ降低．土壤盐分量不同,明显影响无定形氧化铁结合态、紧结有机态以及硅酸盐矿物态Ｚｎ变化．种稻不施有机物料,根际交换态和硅酸盐矿物态Ｚｎ亏缺;碳酸盐结合态、氧化锰结合态和无定形氧化铁结合态Ｚｎ富集．根际Ｚｎ形态转化强度大于非根际,其有效态Ｚｎ量接近临界值并高于非根际．有机物料利于根际内外土壤中硅酸盐矿物态Ｚｎ的转化,低盐土壤根际更强烈．随有机物料用量增加,促使根际硅酸盐矿物态、碳酸盐结合态及氧化锰结合态Ｚｎ向交换态、紧结有机态和无定形氧化铁结合态Ｚｎ转化,低盐土壤较明显．     

Adsorption of polycyclic aromatic hydrocarbons (PAHs) by soil particles: influence on biodegradability and biotoxicity

Summary Polycyclic aromatic hydrocarbon (PAH) biodegradation was investigated in contaminated soils from two different industrial sites under simulated land treatment conditions. Soil samples from a former impregnation plant (soil A) showed high degradation rates of PAHs by the autochthonous microorganisms, whereas PAHs in material of a closed-down coking plant (soil B) were not degraded even after inoculation with bacteria known to effectively degrade PAHs. As rapid PAH biodegradation in soil B was observed after PAHs were extracted and restored into the extracted soil material, the kind of PAH binding in soil B appears to completely prevent biodegradation. Sorption of PAHs onto extracted material of soil B follows a two-phase process (fast and slow); the latter is discussed in terms of migration of PAHs into soil organic matter, representing less accessible sites within the soil matrix. Such sorbed PAHs are suggested to be non-bioavailable and thus non-biodegradable. By eluting soil B with water, no biotoxicity, assayed as inhibition of bioluminescence, was detected in the aqueous phase. When treating soil A analogously, a distinct toxicity was observed, which was reduced relative to the amount of activated carbon added to the soil material. The data suggest that sorption of organic pollutants onto soil organic matter significantly affects biodegradability as well as biotoxicity.     

根际圈在污染土壤修复中的作用与机理分析

根际圈以植物根系为中心聚集了大量的生命物质及其分泌物,构成了极为独特的“生态修复单元”。本文叙述了根在根际圈污染土壤修复中的生理生态作用,富集、固定重金属,吸收、降解有机污染物等功能;菌根真菌对根际圈内重金属的吸收、屏障及螯合作用,对有机污染物的降解作用;根际圈内细菌对重金属的吸附与固定,对有机污染物的降解作用以及根际圈真菌和细菌的联合修复作用等,同时对可能存在的机理进行了分析,认为根际圈对污染土壤的修复作用是植物修复的重要组成部分和主要理论基础之一,并指出利用重金属超富集植物修复重金属污染土壤具有广阔的应用前景;筛选对水溶性有机污染物高吸收富集及其根 发泌能力强的特异植物,同时接种利于有机污染物降解的专性或非专性真菌和细菌可能会成为有机污染土壤植物修复研究的重要方向之一。     

生态系统转换对土壤中碳水化合物的影响

采集贵州省茂兰喀斯特原始红楼梦 林中森林土壤和相邻农田土壤,系统分析其中碳水化合物总量和各单糖的含量。并以此来查明由森林生态系统向农业生态系统转换的过程对土壤碳水化合物的影响,结果表明：相对于森林土壤,农业土壤中碳水化合物总量明显降低。在农田土壤中六糖/五糖比值有升高的趋势,其中以M/X比值最为明显,这说明,在该转换过程中植物来源的单糖组分有所降低,微生物来源的则相对增加。     

Effect of green manure on Pythium spp. population and microbial communities in intensive cropping systems

Saprophytic soil-borne pathogens can be either actively suppressed by organic amendments or enhanced, depending on soil health conditions. This can be deleterious in the event of selection of a soil-borne population by previous soil management and short crop rotation. Trials were performed in the open field and in pots, using naturally infected soil from intensive crop systems, i.e., soil from fields with 8 years of strawberry cultivation. The aim was to study short-term response of Pythium and soil microbial populations to green manure. The use of green manure in these naturally infested soils, 3–10 weeks after fresh tissue incorporation, caused Pythium populations to increase concurrent with an increase in soil microbial populations, and did not result in the suppression of the pathogen. A more elaborate trial was performed under controlled conditions, amending soil with fresh wheat plant material, air-dried wheat plant material and an organic fertilizer with a high level of humic substances. Although compared to the original soil, all amendments caused a similar increase in organic matter content and small differences in soil respiration, incorporation of fresh, not decomposed, plant material strongly increased Pythium, while the organic fertilizer did not affect the original level of the pathogen population. The increase in total number of fungi and bacteria did not have any suppressive effect on the Pythium population in naturally infested soil used for this study.     

Soil acidification and adaptations of plants and microorganisms in Bornean tropical forests

In tropical forest ecosystems, a paradoxical relationship is commonly observed between massive biomass production and low soil fertility (low pH). The loss and deficiency of soil phosphorus (P) and bases generally constrain biomass production; however, high productivity on nutrient-deficient soils of Bornean tropical forests is hypothesized to be maintained by plant and microorganism adaptation to an acidic soil environment. Proton budgets in the plant–soil system indicated that plants and microorganisms promote acidification to acquire bases, even in highly acidic tropical soils. The nitric and organic acids they produce contribute to the mobilization of basic cations and their uptake by plants. In response to soil P deficiency and the recalcitrance of lignin-rich organic matter, specific trees and fungi can release organic acids and enzymes for nutrient acquisition. Organic acids exuded by roots and rhizosphere microorganisms can promote the solubilization of P bonded to aluminum and iron oxides and its uptake by plants from P-poor soils. Lignin degradation, a rate-limiting step in organic matter decomposition, is specifically enhanced in acidic organic layers by lignin peroxidase, produced by white-rot fungi, which may solubilize recalcitrant lignin and release soluble aromatic substances into the soil solution. This dissolved organic matter functions in the transport of nitrogen, P, and basic cations in acidic soils without increasing leaching loss. In Bornean tropical forests, soil acidification is promoted by plants and microorganisms as a nutrient acquisition strategy, while plant roots and fungi can develop rhizosphere and enzymatic processes that promote tolerance of low pH.     

Allelopathic compounds in soil from no tillagevs conventional tillage in wheat production

Summary Incorporating allelopathy into agricultural management may reduce the use of herbicides, cause less pollution, and diminish autotoxic hazards. Authentic inhibitors isolated from plant material have been subjects for examinationin vitro, but attempts to compare their effects in soils are limited. Soils contain a heterogeneous collection of organic matter of various origins. Organic solvents and water extracts prepared from monoculture wheat soils under conventional tillage (CT) and no tillage (NT) indicated that both soils contain some inhibitory compounds. The CGC/MS/DA of some of the organics is presented. Selected organics from CT and NT as well as allelopathic and autotoxic effects are described and discussed. The relationship between the wheat yeilds in CT and NT and the possible biological stress is indicated.     

Long‐term carbon storage through retention of dissolved aromatic acids by reactive particles in soil

Soils retain large quantities of carbon, thereby slowing its return to the atmosphere. The mechanisms governing organic carbon sequestration in soil remain poorly understood, yet are integral to understanding soil‐climate feedbacks. We evaluated the biochemistry of dissolved and solid organic carbon in potential source and sink horizons across a chronosequence of volcanic soils in Hawai'i. The soils are derived from similar basaltic parent material on gently sloping volcanic shield surfaces, support the same vegetation assemblage, and yet exhibit strong shifts in soil mineralogy and soil carbon content as a function of volcanic substrate age. Solid‐state¹³carbon nuclear magnetic resonance spectra indicate that the most persistent mineral‐bound carbon is comprised of partially oxidized aromatic compounds with strong chemical resemblance to dissolved organic matter derived from plant litter. A molecular mixing model indicates that protein, lipid, carbohydrate, and char content decreased whereas oxidized lignin and carboxyl/carbonyl content increased with increasing short‐range order mineral content. When solutions rich in dissolved organic matter were passed through Bw‐horizon mineral cores, aromatic compounds were preferentially sorbed with the greatest retention occurring in horizons containing the greatest amount of short‐range ordered minerals. These minerals are reactive metastable nanocrystals that are most common in volcanic soils, but exist in smaller amounts in nearly all major soil classes. Our results indicate that long‐term carbon storage in short‐range ordered minerals occurs via chemical retention with dissolved aromatic acids derived from plant litter and carried along preferential flow‐paths to deeper B horizons.     

Effect of termite mound material on the physical properties of sandy soil and on the growth characteristics of tomato (Solanum lycopersicum L.) in semi-arid Niger

This investigation assessed the effects of termite mound material (TMM) on the physical properties of sandy soil and on tomato (Solanum lycopersicum L.) growth characteristics and water use efficiency. TMM combined with organic manure, TMM combined with rice straw mulching and organic manure, organic manure alone (OM) and unamended (T0) were the treatments used. Results showed that soil treated with TMM had more clay sized particles and organic carbon content than T0 and OM. In TMM-treated soil, more water was being retained at both field capacity and permanent wilting point. The application of TMM did not affect the amount of plant available water. Saturated hydraulic conductivity also remained unaffected by the TMM application, but increased with the organic matter treatment. Tomatoes grown in TMM amended soils had greater plant height and more leaves, fruit and biomass. No specific rate of TMM application was better for all parameters being assessed. The amount of water used by the tomatoes was significantly correlated (P?<?0.01) with fresh fruit yield (r?=?0.82), leaf area index (r?=?0.82) and total dry matter production (r?=?0.68). While TMM did not specifically affect plant water-use efficiency, this parameter was generally improved in amended soils.     

中亚热带不同母质发育森林土壤磷组分特征及其影响因素

本研究以福建三明砂岩和花岗岩发育的米槠林土壤和杉木林土壤为对象,分析土壤磷组分、铁铝氧化物、微生物生物量以及磷酸酶活性等指标,研究母质和森林类型对土壤磷组分的影响程度和机制.结果表明:母质和森林类型显著影响土壤不同磷组分含量.总体上,砂岩发育土壤全磷含量、活性无机/有机磷、中等活性无机/有机磷以及惰性磷含量均显著高于花...     

Climate change effects on organic matter decomposition rates in ecosystems from the Maritime Antarctic and Falkland Islands

Antarctic terrestrial ecosystems have poorly developed soils and currently experience one of the greatest rates of climate warming on the globe. We investigated the responsiveness of organic matter decomposition in Maritime Antarctic terrestrial ecosystems to climate change, using two study sites in the Antarctic Peninsula region (Anchorage Island, 67°S; Signy Island, 61°S), and contrasted the responses found with those at the cool temperate Falkland Islands (52°S). Our approach consisted of two complementary methods: (1) Laboratory measurements of decomposition at different temperatures (2, 6 and 10 °C) of plant material and soil organic matter from all three locations. (2) Field measurements at all three locations on the decomposition of soil organic matter, plant material and cellulose, both under natural conditions and under experimental warming (about 0.8 °C) achieved using open top chambers. Higher temperatures led to higher organic matter breakdown in the laboratory studies, indicating that decomposition in Maritime Antarctic terrestrial ecosystems is likely to increase with increasing soil temperatures. However, both laboratory and field studies showed that decomposition was more strongly influenced by local substratum characteristics (especially soil N availability) and plant functional type composition than by large-scale temperature differences. The very small responsiveness of organic matter decomposition in the field (experimental temperature increase < 1 °C) compared with the laboratory (experimental increases of 4 or 8 °C) shows that substantial warming is required before significant effects can be detected.     

Soil factors predict initial plant colonization on Puerto Rican landslides

Tropical storms are the principal cause of landslides in montane rainforests, such as the Luquillo Experimental Forest (LEF) of Puerto Rico. A storm in 2003 caused 30 new landslides in the LEF that we used to examine prior hypotheses that slope stability and organically enriched soils are prerequisites for plant colonization. We measured slope stability and litterfall 8–13 months following landslide formation. At 13 months we also measured microtopography, soil characteristics (organic matter, particle size, total nitrogen, and water-holding capacity), elevation, distance to forest edge, and canopy cover. When all landslides were analyzed together, plant biomass and cover at 13 months were not correlated with slope stability or organic matter, but instead with soil nitrogen, clay content, water-holding capacity, and elevation. When landslides were analyzed after separating by soil type, the distance from the forest edge and slope stability combined with soil factors (excluding organic matter) predicted initial plant colonization on volcaniclastic landslides, whereas on diorite landslides none of the measured characteristics affected initial plant colonization. The life forms of the colonizing plants reflected these differences in landslide soils, as trees, shrubs, and vines colonized high clay, high nitrogen, and low elevation volcaniclastic soils, whereas herbs were the dominant colonists on high sand, low nitrogen, and high elevation diorite soils. Therefore, the predictability of the initial stage of plant succession on LEF landslides is primarily determined by soil characteristics that are related to soil type.     

Comparative analysis of microbial diversity and bacterial seedling disease‐suppressive activity in organic‐farmed and standardized commercial conventional soils for rice nursery cultivation

The outbreak of rice plant diseases can be effectively suppressed in organic farming systems. However, the mechanisms of disease suppression by organic farming systems are not well understood. When Burkholderia‐infected rice seeds were sown and cultivated on nine organic‐farmed soils which were supplied by nine independent organic rice farmers or standardized commercial conventional soils, the emergence of bacterial seedling diseases was suppressed to equivalent degrees in nine organic‐farmed soils, whereas the diseases occurred in two commercial conventional soils. In any organic or commercial conventional soil sown with healthy rice seeds as a control, the diseases did not appear. Upon physicochemical analysis of the nine organic‐farmed soils, component common to these organic‐farmed soils seemed to not be directly associated with disease‐suppressive activity. However, microbiome analyses indicated that the bacterial population in these nine organic‐farmed soils was more diverse than those in commercial conventional soils. Intriguingly, the diverse bacterial population structures of organic‐farmed soils were preserved after irrigating and sowing rice seeds, but that of commercial conventional soils was clearly changed by them. Thus, organic‐farmed soils seem to maintain robust bacterial populations despite the irrigation and seedling growth. Indeed, pathogenic Burkholderia in infected rice seeds also did not proliferate in the seedling grown on organic‐farmed soils. Taken together, the common feature of organic‐farmed soils might be the correlation between bacterial seedling disease‐suppressive activity and higher robustness of the diversified microbiome.