高光谱技术——生态学领域研究的新方法

高光谱技术是一种新的地物探测技术,该技术以其敏锐的地物光谱特征探测能力为精准识别地物属性提供了强有力的手段,在生态系统过程与属性研究中具有广阔的应用前景。该文以可见光-近红外光谱分析技术为例概述了高光谱技术的原理、特点与优势,以及高光谱技术分析的流程;总结并归纳了其在土壤、植物生理、农产品品质检测、凋落物分解方面的研究应用,指出高光谱技术与遥感成像技术结合在生态监测研究中的优势;归纳了高光谱技术应用中面临的问题,并希望高光谱技术在生态学领域研究中得到更广泛的应用。     

同位素示踪技术在丛枝菌根真菌生态学研究中的应用

丛枝菌根(arbuscular mycorrhizal,AM)真菌是生态系统中重要的土壤微生物之一。AM真菌菌丝体网络是由AM真菌菌丝体在土壤生态系统中连接两株或两株以上植物根系所形成的菌丝体网络。随着菌根学研究的深入,如何直观的揭示AM真菌的生态学功能已经成为相关领域关注的热点问题。研究发现,利用同位素示踪技术可以开展AM真菌与宿主植物对土壤矿质营养的吸收、转运等方面的研究,以及菌丝体网络对不同宿主植物之间营养物质的分配研究和AM真菌在生态系统生态学中的功能研究。基于此,为了阐明同位素示踪技术在AM真菌研究中的价值,围绕菌根学最新研究进展,系统回顾了利用同位素示踪技术探究AM共生体对不同元素吸收和转运的机制、同位素示踪技术在AM真菌菌丝体网络研究中的价值和利用同位素示踪技术研究AM真菌在生态系统中的功能,为AM真菌生态学功能的研究提供理论基础,并对本领域未来的研究方向和应用前景进行展望。     

A simple method for the extraction of soil solution by high speed centrifugation

Summary A simple technique for extracting samples of soil solution by high speed centrifugation is described. The method uses inexpensive commerically available centrifuge tubes requiring only slight modification. Aspects of the method are discussed together with an example of its application.     

Application of actinomycetes to soil to ameliorate water repellency

AIMS: The aim of this study was to develop a novel isolation technique using a mixture of Bacillus and Streptomyces phages to selectively isolate wax-utilizing non-streptomycete actinomycetes effective in ameliorating water repellency in a problem soil. METHODS AND RESULTS: Phages added to a soil suspension reduced the dominance of Bacillus and Streptomyces isolates and significantly increased the number of non-streptomycete actinomycetes on isolation plates. Promising isolates, grown on a medium containing beeswax as sole carbon source, were selected for application to water repellent soil. Their addition significantly reduced water repellency. CONCLUSIONS: Phage application significantly increased the isolation of non-streptomycete actinomycetes. Wax-utilizing isolates were found to significantly reduce water repellency in a problem soil. SIGNIFICANCE AND IMPACT OF THE STUDY: The phage technique can be used for the routine isolation of non-streptomycete actinomycetes. Beeswax medium can be used to selectively isolate wax-utilizing micro-organisms with the potential to ameliorate water repellency in soil.     

分形理论及其在土壤空间变异研究中的应用

土壤具有不同程度的空间变异性,土壤空间变异研究对于土壤管理有重要意义.本文简要综述了分形理论及其在土壤空间变异研究中的应用,重点讨论了利用矩方法计算土壤属性分形维,多重分形分析土壤空间变异性及基于多重分形谱参数的土壤属性尺度转换.早期研究验证了分形理论在分析土壤空间变异中的有效性和应用潜力,国内外近期研究则报道了利用分形及多重分形理论分析土壤空间变异的最新进展.分形理论可以成为量化土壤属性空间变异性及尺度转换的重要工具.     

施氮和玉米生长对土壤氧化亚氮排放的影响

运用土壤盆栽试验、静态箱法采样和气相色谱分析技术研究了种植玉米土壤和裸土在两种土壤施氮水平 (低氮:150 mg·kg^-1土,和高氮:300 mg·kg^-1土) 下对土壤排放N₂O的影响.结果表明,在种植玉米的土壤中,N2O排放率的峰值出现在苗期,且氮肥施用量的影响显著,土壤N₂O排放率与温度没有显著的相关性.在裸土中,土壤N₂O排放率的峰值出现在试验后期,土壤N₂O排放率与温度呈极显著指数相关.土壤施氮量增加,土壤N₂O排放总量增加,裸土N₂O增加尤其显著,种植玉米比裸土减少87%～92%的N₂O排放量.这一结果表明种植作物与否,不仅改变了土壤N₂O排放的季节变化和排放量,而且改变了温度与土壤N₂O排放之间的关系.     

Quantification of the slug parasitic nematode Phasmarhabditis hermaphrodita from soil samples using real time qPCR

Phasmarhabditis hermaphrodita is a nematode parasite that infects and kills several species of slugs. The nematode is produced commercially as a biological control agent for slug pests of agriculture and horticulture. Given the difficulties of distinguishing this species from other nematode species in soil samples, very little is known about its natural ecology or its behaviour and persistence following application for biological control. Here we describe a method to quantify P. hermaphrodita in soil samples based on real time PCR. We designed primers and a dual labelled fluorescent probe that can be used to quantify numbers of P. hermaphrodita and which is capable of distinguishing this species from the morphologically identical Phasmarhabditis neopapillosa. We compared different methods whereby the entire nematode community is extracted prior to DNA extraction, and three methods to extract DNA directly from soil samples. Both nematode extraction and DNA extraction from large (10 g) samples of soil gave reliable estimates of nematode numbers, but methods which extracted DNA from small (1 g or less) soil samples substantially underestimated numbers. However, direct extraction of DNA from soils may overestimate numbers of live nematodes as DNA from dead nematodes was found to persist in soil for at least 6 days. The technique could be modified for detection and quantification of all soil borne parasitic nematodes.     

Some aspects of microbiological stimulation in a soil treated with streptomycin

Summary An investigation was made to follow the effect of streptomycin on the soil microflora using a direct method of observation together with plate counting technique on some selective media.It was reported that the bactericidal effect of streptomycin in the first week of application to soil, has masked an early stimulatory effect manifested by stimulation of two bacterial species appearing on mannitol nitrogen-free agar plates. One of these bacterial species identified as Pseudomonas sp. was able to fix small but significant amounts of nitrogen. The direct observation technique enabled to observe some aspects of microbial stimulation in soil. Stimulation of large cocci, identified as Hansenula sp., long bacterial rods, and Fusarium solani were successfully observed by such technique. Enrichment technique helped in isolating Hansenula sp. and F. solani; F. solani formed a mat on the surface of treated soil 50 days after streptomycin application. The recorded aspects of stimulation were claimed to be due to microbial equilibrium disturbance as a result of applying streptomycin to soil. Suggestion for further investigations was offered to verify the possible significance of such aspects of stimulation in controlling soil-borne pathogens.     

原位酶谱技术在土壤酶活性研究中的应用进展

原位酶谱可方便、直观地展示土壤中酶活性的二维空间变异,近些年来通过与其他成像技术和分析方法相结合,土壤原位酶谱已发展成为分析土壤微观生态过程及土壤-根系-土壤动物相互作用界面过程的有效方法。然而,土壤原位酶谱技术尚未成熟,亟待深入分析其技术不足、完善技术方法,梳理其在不同领域中的应用现状,拓展并深化其在更多领域研究中的应用前景。基于此,综述并分析了该技术在土壤酶相关研究领域的应用现状,结合原位酶谱技术在底物载体选择与酶活定量方法的优化历程,分析了其存在的问题,发现：(1)可供研究的酶种类较少;(2)结果准确性仍有质疑;(3)在除根际研究外其他领域的研究较少、缺乏系统性,难以直接借鉴。这三者仍是阻碍原位酶谱技术在多领域中推广的最大障碍。综上所述,土壤原位酶谱技术虽仍存在缺陷,但其具有操作简便、测量结果的时空分辨率高等优势,在未来土壤酶学领域研究中仍潜力巨大,研究旨在为推进原位酶谱技术在土壤学和生态学等学科研究中的应用和发展提供理论指导。     

施硒对水稻土壤硒有效性的影响

硒在华南稻区酸性土壤中极易被固定使其有效性较低.本研究旨在通过盆栽试验,探明施用硒肥对水稻根际和非根际土壤硒有效性的影响.结果表明: 施硒能提高水稻产量,增加籽粒硒含量;水稻根际土壤中水溶态硒、交换态硒、铁锰氧化物结合态硒、有机物-硫化物结合态硒和残渣态硒含量均低于非根际土壤.各施硒处理之间,根际和非根际土壤中硒的迁移系数没有显著差异;施硒对根和叶片之间硒的迁移系数也没有显著影响,但是施硒提高了叶片和籽粒之间硒的迁移系数.施用0.5 mg·kg^-1硒增加了水稻根系有机酸的分泌,而施用1.0、5.0 mg·kg^-1硒则降低了有机酸的分泌.根系有机酸的分泌对根际土壤pH值影响不大,根际土壤pH值反而高于非根际土壤,但施硒显著降低了根际土壤pH值.随着施硒水平的提高,根际土壤黏土矿物(高岭石)的红外吸收光谱不断增强.施入土壤中的硒多转化为水稻难以吸收利用的形态,且不易向根际移动.根系分泌的有机酸也并不是通过影响土壤pH值来提高土壤硒的有效性.     

Development of an agar lift-DNA/DNA hybridization technique for use in visualization of the spatial distribution of Eubacteria on soil surfaces.

While microbial growth is well-understood in pure culture systems, less is known about growth in intact soil systems. The objective of this work was to develop a technique to allow visualization of the two-dimensional spatial distribution of bacterial growth on a homogenous soil surface. This technique is a two-step process wherein an agar lift is taken and analyzed using a universal gene probe. An agar lift is comprised of a thin layer of soil that is removed from a soil surface using an agar slab. The agar is incubated to allow for microbial growth, after which, colonies are transferred to a membrane for conventional bacterial colony DNA/DNA hybridization analysis. In this study, a eubacterial specific probe was used to demonstrate that growing bacterial populations on soil surfaces could be visualized. Results show that microbial growth and distribution was nonuniform across the soil surface. Spot supplementation of the soil with benzoate or glucose resulted in a localized microbial growth response. Since only growing colonies are detected, this technique should facilitate a greater understanding of the microbial distribution and its response to substrate addition in more heterogenous soil systems.     

桑树根际土壤微生物对间作和施氮的响应

利用Biolog-Ecoplate^TM结合主成分与冗余分析法,研究与苜蓿间作和施氮对桑树根际土壤微生物功能多样性及其与环境因子的影响.结果表明: 与单作无氮相比,单作施氮和间作(无氮和施氮)明显降低桑树根际土壤pH值,显著提高有机质含量、有效氮、含水量和过氧化物酶、脲酶的活性.同时,单作施氮和间作(无氮和施氮)提高了桑树根际土壤微生物的AWCD值、多样性指数和利用碳源比例,且间作施氮增加其提高的程度.主成分分析表明,施氮和间作改变了根际土壤微生物利用碳源强度和种类,其中单作施氮和与间作无氮处理的碳源利用情况相似,但后者对衣康酸和D-葡糖胺酸的利用率(>4%)显著高于前者.冗余分析表明,单作无氮桑树根际土壤微生物多样性与土壤多酚氧化酶活性呈正相关,与土壤含水量呈负相关.单作施氮与间作无氮处理的桑树根际微生物多样性与土壤pH值和含水量呈显著正相关,与土壤氮素营养呈负相关.间作施氮处理的桑树根际微生物多样性与土壤氮素营养呈正相关,而与土壤pH值呈显著负相关.     

Efficient use of animal manure on cropland--economic analysis

Manure contains all the macro- and microelements needed for plant growth; however, it represents one of the most underutilized resources in the US. The major problem with the use of manure on cropland is the direct effect of its composition on application cost. This cost is a function of the mineralization process of organic matter. The mineralization process is influenced by the properties of the manure, properties of the soil, moisture, and temperature. This study evaluates the simultaneous effect of these variables on the optimal use of manure on cropland. The results show that the properties of manure and soil significantly affect the mineralization of organic nitrogen and thus the optimal quantity of manure required to satisfy the nutrient requirement of crops in a given rotation system. Manure application costs range from a low of 18% of the cost of commercial fertilizer for chicken manure applied to one type of soil, to a high of 125% of the cost of commercial fertilizer for cow manure applied to another type of soil. The maximum distance to transfer manure to the field, that will equate its application cost to the cost of commercial fertilizer, ranges from a high of 35 km (22 miles) for chicken manure applied to one type of soil, to a low of 1 km (0.62 miles) for cow manure applied to another type of soil. For rotation system 2, manure application costs range from a low of 37% of the cost of commercial fertilizer for chicken manure applied to one type of soil, to a high of 136% of the cost of commercial fertilizer for cow manure applied to another type of soil. The maximum distance to transfer manure to the field, that will equate its cost to the cost of commercial fertilizer, ranges from a high of 20 km (12.5 miles) for chicken manure applied to one type of soil, to a low of 0 km (0 miles) for cow manure applied to another type of soil.     

Efficacy of urea spray for wheat crop under irrigated conditions in Iraq

Summary Effects of varying levels of nitrogenviz 40, 80 and 120 kg/ha and two methods of applicationviz (1) Soil application; and (2) one half applied to the soil and the other half to the plant foliage, were studied on growth and yield of wheat crop. Results showed that foliar feeding of urea in combination with soil application to wheat crop gave significant increases in their grain yields. Thus there is a great scope of utilizing this technique for increasing grain yields of wheat and other cereal crops grown in Iraq.     

Evaluating the Effect of Three Water Management Techniques on Tomato Crop

The effects of three water management techniques were evaluated on subsurface drip irrigated tomatoes. The three techniques were the intermittent flow (3 pulses), the dual-lateral drip system (two lateral lines per row, at 15 and 25cm below soil surface), and the physical barrier (buried at 30 cm below soil surface). Field experiments were established for two successive seasons. Water movement in soil was monitored using continuously logging capacitance probes up to 60 cm depth. The results showed that the dual lateral technique positively increased the yield up to 50%, water use efficiency up to 54%, while the intermittent application improved some of the quality measures (fruit size, TSS, and Vitamin C), not the quantity of the yield that decreased in one season, and not affected in the other. The physical barrier has no significant effect on any of the important growth measures. The soil water patterns showed that the dual lateral method lead to uniform wetting pattern with depth up to 45 cm, the physical barrier appeared to increase lateral and upward water movement, while the intermittent application kept the wetting pattern at higher moisture level for longer time. The cost analysis showed also that the economic treatments were the dual lateral followed by the intermittent technique, while the physical barrier is not economical. The study recommends researching the effect of the dual lateral method on the root growth and performance. The intermittent application may be recommended to improve tomato quality but not quantity. The physical barrier is not recommended unless in high permeable soils.     

施磷对稻田土壤及田面水磷浓度影响的模拟

通过施用不同剂量磷肥稻田土壤淹水培养试验,研究了施磷对稻田土壤及田面水磷浓度的影响.结果表明,土壤速效磷（Olsen-P）浓度在施磷后迅速下降,60 d后趋于稳定.随施磷量的增加,土壤速效磷和缓效磷库量均递增,Olsen-P与施磷量呈正相关关系(y=21.49+0.086x),表明该土壤有很高的固磷潜力.施磷后田面水中全磷浓度呈先迅速上升后又缓慢下降趋势,施磷120 d后,田面水中全磷浓度与施磷量呈指数相关关系(y=0.3 72e^0.0022x),施磷量在400～800 kg·hm^-2之间田面水全磷浓度加速增长,如果施磷量达到或超过800 kg·hm^-2,则磷容易进入田面水并导致流失,低于该施磷量时,则磷进入田面水中的量较少.利用分段回归模型模拟土壤Olsen-P与水面全磷关系,预测出导致田面水中磷激增的土壤Olsen-P浓度“突变点”为82.7 mg·kg^-1,即施磷量为712 kg·hm^-2.因此,土壤Olsen-P浓度可作为预测田面水中磷损失程度的指标.     

稳定碳同位素技术在土壤-植物系统碳循环中的应用

碳作为重要的生命元素,在土壤 植物系统物质循环中发挥重要作用.作为一种天然的示踪物,稳定碳同位素（¹³C）较放射性同位素具有安全、无污染、易控制的优点,在土壤 植物生态系统碳循环研究中得到广泛应用.通过检测土壤 植物体系中稳定碳同位素的自然丰度或采用稳定碳同位素标记有机材料,能够较真实地了解植物的光合特性、光合产物在土壤 植物体系中的运转及其在土壤中的分解、转化等过程.本文概述了稳定碳同位素技术在植物光合作用及光合产物运转、古气候重建、土壤有机质周转以及植物 根际微生物相互作用等方面的研究进展,并针对当前研究中存在的问题提出了今后的研究展望.     

施用生物炭对土壤动物群落的影响研究进展

土壤动物是土壤生物群落不可或缺的组成部分,是调控土壤生态过程重要的生物驱动因子。探明向土壤中施加生物炭对土壤动物群落的影响及二者之间的相互关系,对深刻认识土壤生态系统的运行机制、评价土壤生态服务功能具有重要意义。本文综述了施用生物炭对土壤动物群落的影响及机制,包括生物炭原料、制备温度、施用量的差异对土壤动物群落造成的直接影响,及以生物介导(改变植物生理特性、提高微生物数量)和非生物介导(土壤理化性质的改变)环境条件的改变对土壤动物群落造成的间接影响。低量生物炭添加下(生物炭与土壤质量比＜5%),对土壤动物的生长繁殖和行为活动起促进作用,若施炭量过高(＞10%),则会产生毒害;土壤动物的行为活动也会影响生物炭的稳定性。未来应该加强长期田间定位、时空变异性、多学科交融和分析预测等方面的研究。     

Municipal solid waste compost amendment in agricultural soil: changes in soil microbial biomass

Agricultural application of Municipal Solid Waste (MSW), as nutrient source for plants and as soil conditioner, is the most cost-effective option of MSW management because of its advantages over traditional means such as landfilling or incineration. However, agricultural application of MSW can lead to a potential environmental threat due to the presence of pathogens and toxic pollutants. Composting is an attractive alternative of MSW recycling. Application of MSW compost (MSWC) in agricultural soils can directly alter soil physico-chemical properties as well as promote plant growth. The soil microbial biomass, considered as the living part of soil organic matter, is very closely related to the soil organic matter content in many arable agricultural soils. Numerous studies, with different MSWC amendment doses on different soil types and under different water regimes revealed no detrimental effect on soil microbial biomass. In this review, we show the state of art about the effects of MSWC amendment on soil microbial biomass.     

Biofunctionalization of nanoparticle assisted mass spectrometry as biosensors for rapid detection of plant associated bacteria

This study is based on the application of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) as biosensor to detect the plant associated bacteria (PAB) isolates from rhizospheric soil and root. The rapid bacterial detection via on particle ionization/enrichment technique using IgG functionalized Pt NPs (IgG-Pt NPs) assisted MALDI-TOF MS was successfully used to explore two PAB isolates, namely, Bacillus thuringiensis and B. subtilis from rhizospheric soil and roots of carrot plant. When these bacteria are used as bioformulations in agricultural as well as biotechnological applications, the plant growth promotion of economic crops was observed especially when the crops grow in less fertilize soil regions. This study proved that even at low concentrations, bacteria can also be directly detected without morphological, molecular and biochemical test. The current applied technique is simple, rapid and highly sensitive. Besides, it could be widely used for the detection of beneficially important PAB isolates in environmental samples.