Developments in soil microbiology since the mid 1960s

Since the 1960s, soil microbiology underwent major changes in methods and approaches and this review focuses on the developments in some selected aspects of soil microbiology. Research in cell numbers of specific bacterial and fungal groups was replaced by a focus on biochemical processes including soil enzyme activities, and flux measurements of carbon and nutrients. Ecologists focused on soil microbial pools whereas soil microbial biomass as an important source and sink of nutrients were recognized in agriculture. Soil microbiologists started to use structural components like phospholipid fatty acids for quantification of specific microbial groups without the need to cultivate them. In the last decade, molecular approaches allowed new insights through the analysis of soil extract DNA showing an unexpected diversity of genomes in soil. At the end of the review a brief outlook is given on the future of soil microbiology which ranges from in situ identification of bacteria, to routine assays of microbial communities by microarray technology.     

Changing public interest in,and awareness of,acid deposition: Some evidence from the UK

It is fundamental that the general public have access to usable environmental information on which they can base their decisions. Since 1984 the Atmospheric Research and Information Centre (ARIC) has operated a public information programme for the UK on the subject of acid deposition. The objective of the programme is to disseminate information on acid deposition without advocacy. ARIC provides enquirers with a broad range of authoritative and accurate facts and opinions from a wide range of parties from all sides of the debate. These sources include pressure groups, governmental bodies and industrialists from the UK and overseas. By deconstructing complex technical material and reassembling it for dissemination in a user friendly form, ARIC assists those receiving information to obtain a balanced perspective. This enables personal decision making within the context of the fullest information resource ARIC is able to provide.     

Soil microbial biomass and activity: the effect of site characteristics in humid temperate forest ecosystems

Microbial biomass, respiratory activity, and in‐situ substrate decomposition were studied in soils from humid temperate forest ecosystems in SW Germany. The sites cover a wide range of abiotic soil and climatic properties. Microbial biomass and respiration were related to both soil dry mass in individual horizons and to the soil volume in the top 25 cm. Soil microbial properties covered the following ranges: soil microbial biomass: 20 µg C g^–1–8.3 mg C g^–1 and 14–249 g C m^–2, respectively; microbial C–to–total organic C ratio: 0.1%–3.6%; soil respiration: 109–963 mg CO₂‐C m^–2 h^–1; metabolic quotient (qCO₂): 1.4–14.7 mg C (g C_mic)^–1 h^–1; daily in‐situ substrate decomposition rate: 0.17%–2.3%. The main abiotic properties affecting concentrations of microbial biomass differed between forest‐floor/organic horizons and mineral horizons. Whereas microbial biomass decreased with increasing soil moisture and altitude in the forest‐floor/organic horizons, it increased with increasing N_tot content and pH value in the mineral horizons. Quantities of microbial biomass in forest soils appear to be mainly controlled by the quality of the soil organic matter (SOM), i.e., by its C : N ratio, the quantity of N_tot, the soil pH, and also showed an optimum relationship with increasing soil moisture conditions. The ratio of C_mic to C_org was a good indicator of SOM quality. The quality of the SOM (C : N ratio) and soil pH appear to be crucial for the incorporation of C into microbial tissue. The data and functional relations between microbial and abiotic variables from this study provide the basis for a valuation scheme for the function of soils to serve as a habitat for microorganisms.     

Interdisciplinary and multidisciplinary approaches to the study of long‐term soil degradation: A case study from Schleswig‐Holstein,Germany

Soil degradation is a serious problem and an important environmental issue in many ecosystems. Without integrative, interdisciplinary and historical approaches, understanding the effects of long‐term soil degradation is difficult. According to this idea it is hypothesized that in order to study long‐term natural and human‐induced soil degradation, it is necessary to use interdisciplinary and multidisciplinary approaches with respect to temporal and spatial landscape changes. The results of the investigation of colluvial sediments and soils in research area in Schleswig‐Holstein (Germany) with a high resolution in space and time—using the four‐dimensional landscape analysis—indicated the temporal and spatial variation of soils and sediments from the Mesolithic until Modern times. Intensive soil degradation occurred as a result of the land clearance and agricultural land use in the investigation areas since the Neolithic time. The general results of this investigation show that the use of an interdisciplinary and multidisciplinary approach with pedological and geomorphological perspectives for different times and places can help to reconstruct the long‐term natural and human‐induced soil degradation. Copyright © 2009 John Wiley & Sons, Ltd.     

Podzol: Soil of the Year 2007. A review on its genesis,occurrence, and functions

The Podzol has been elected “Soil of the year 2007” in Germany. This article reviews the present knowledge on the development, functions, and threats of Podzols. The main theories on mobilization and transport of organic matter, Fe, Al, and Si are (1) metal‐organic migration, (2) metal reduction, and (3) inorganic sol migration. Immobilization theories include precipitation or polymerization due to increasing pH/abundance of base cations with depth, mechanical filtering in soil pores, oxidation of metal‐organic complexes, biodegradation of the organic part, decreasing C‐to‐metal ratios during translocation, adsorption to soil particles, and flocculation at the point of zero charge. Podzolization is discussed also on the catena scale, where vertical and lateral translocation processes (across pedon boundaries) need to be considered to understand Podzol patterns in landscapes. Chronosequence studies show that incipient podzolization usually becomes visible between 100 and 500 y and mature Podzols develop in 1,000–6,000 y. The occurrence of Podzols worldwide is concentrated mainly on the boreal zone and mountain regions within the humid temperate zone. Smaller Podzol areas are found in some perhumid tropical and subtropical regions. In Germany, Podzols occur in the Alps, in the glaciofluvial valleys and heathlands of N Germany, and in the mountain ranges. They fulfil several ecological functions, especially for groundwater recharge. Main threats for these mostly sandy soils are wind erosion and surface mining of sand. Two pedons which were chosen to represent the “Soil of the year 2007” are presented. Finally, some conclusions about podzolization processes are drawn, which may explain the diverse observations reported in the literature.     

现代气候变化情景下土壤微生物活性和碳动态研究进展

Microbial activities are affected by a myriad of factors with end points involved in nutrient cycling and carbon sequestration issues. Because of their prominent role in the global carbon balance and their possible role in carbon sequestration, soil microbes are very important organisms in relation to global climate changes. This review focuses mainly on the responses of soil microbes to climate changes and subsequent effects on soil carbon dynamics. An overview table regarding extracellular enzyme activities (EAA) with all relevant literature data summarizes the effects of different ecosystems under various experimental treatments on EAA. Increasing temperature, altered soil moisture regimes, and elevated carbon dioxide significantly affect directly or indirectly soil microbial activities. High temperature regimes can increase the microbial activities which can provide positive feedback to climate change, whereas lower moisture condition in pedosystem can negate the increase, although the interactive effects still remain unanswered. Shifts in soil microbial community in response to climate change have been determined by gene probing, phospholipid fatty acid analysis (PLFA), terminal restriction length polymorphism (TRFLP), and denaturing gradient gel electrophoresis (DGGE), but in a recent investigations, omic technological interventions have enabled determination of the shift in soil microbe community at a taxa level, which can provide very important inputs for modeling C sequestration process. The intricacy and diversity of the soil microbial population and how it responds to climate change are big challenges, but new molecular and stable isotope probing tools are being developed for linking fluctuations in microbial diversity to ecosystem function.     

A Scanning Electron Microscopy Study of a Calcium‐Polygalacturonate Network in the Presence of Aluminum: A Model to Investigate Soil‐Root Interface Processes

Abstract

The objective of this study was to investigate the effects of aluminum (Al³⁺) on a calcium‐polygalacturonate (Ca‐PG) network used as a soil‐root interface model. Calcium‐PG networks were exposed to Al³⁺ solutions at different concentrations (100, 200, 400, and 800 µM) at pH 3.50. In the present study, the scanning electron microscopy technique was used to evaluate morphological variations induced by Al³⁺sorption. Results showed how aluminum (Al) sorption induces conformational changes of the Ca‐PG complex. The Ca‐PG complex shows a regular structure with a honeycomb‐like pattern. Interlacing fibrils form a porous system, which can easily allow sorption and/or passage of nutrients as well as toxic elements. As Al becomes the predominant reticulating ion, the pores decrease in size and lose their regular shape. The scanning electron micrographs have in fact shown that Al sorption damages the Ca‐PG complex, leading to its collapse; the Ca‐Al‐PG networks exhibit an irregular uneven structure.     

A social learning video method: Identifying and sharing successful transformation knowledge for sustainable soil management in Switzerland

To enhance sustainable land use, a From Farmer to Farmer project was conducted in Switzerland (2001–2010). A multi‐stakeholder discussion group co‐produced nine videos with experienced farmers and wine producers showing sustainable soil management practices. We analysed the video audio‐visual content and drew on reflections of the co‐production process, referring to concepts of system, target and transformation knowledge, as well as on social learning. The analysis showed a broad range of means (or actions) for sustainable soil management in arable land management, fodder production and wine growing that are aligned to transformation knowledge. The research showed that farmers refer to three phases of social learning, light‐bulb moments, coping with challenges and gaining successful expertise. These are not just linear processes of individuals. Four types of social learning were found in the video analysis: (a) learning from observing actions of others, (b) sharing experiences with storytelling, (c) informal social interactions and (d) being a role model with a large social network. Videos enable transformation knowledge to be shared with peers using storytelling; this powerful narrative communication style provides credibility and respects the ‘thought style’ of the target audience group. We conclude that for successful implementation of sustainable actions, it is important to address a specific target group and share their transformation knowledge built upon system and target knowledge. The social learning video method is a viable way to enable social learning between science, administration and practice and has potential for fostering change in sustainable soil management.     

Soil organic carbon content and soil structure quality of clayey cropland soils: A large-scale study in the Swiss Jura region

Soil organic carbon (SOC) fashions soil structure, which is a key factor of soil fertility. Existing SOC content recommendations are based on SOC:clay ratio thresholds of >1:10. However, the corresponding SOC content might be considered hard to reach in clayey soils, whose structure degradation risk is assumed to be high. Here, we analysed the SOC content and soil structure quality of soils under similar cropping practices with clay contents ranging from 16% to 52%. Five undisturbed soil cores (5–10 cm layer) were collected from 96 fields at 58 farms in the Swiss Jura region. We assessed the soil structure quality visually using the CoreVESS method. Gravimetric air content and water content, and bulk density at −100 hPa were also measured, and the soil structure degradation index was calculated. We found that the relationship between SOC and clay content held over the clay content range, suggesting that reaching an acceptable SOC:clay ratio is not limited by large clay contents. This suggests that the 1:10 SOC:clay ratio may remain useful for clayey soils. In contrast to what was expected, it is not more challenging to reach this ratio in clayey soils even if it implies reaching very large SOC contents. SOC content explained the considered physical properties better than clay content. From a soil management point of view, these findings suggest that the soil texture determines a potential SOC content, while the SOC:clay ratio is determined by farming practices regardless of the clay content.     

长江上游紫色丘陵区土壤侵蚀与泥沙输移比研究——以涪江流域为例

 通过涪江流域水文站控制区域的地貌与土地利用类型的综合分析,以不同土地利用类型地块作为侵蚀量计算单元,计算每个流域发生侵蚀的地块（即旱坡地、陡坡旱地、有林地、疏林地、草地、灌木地和裸地）侵蚀量,得到全流域年均侵蚀量为2 460万t/a,年均侵蚀模数为813.9 t/（km2.a）,上游山地区侵蚀模数>1 000 t/（km2.a）,紫色丘陵区侵蚀模数50～0800t/（km2.a）;流域平均泥沙输移比为0.83,上游泥沙输移比>0.90,中下游丘陵区泥沙输移比在0.30～0.80之间,而在流域上中游山地丘陵衔接的冲洪积扇区的年均泥沙沉积量约144万t/a;流域泥沙输移比与流域面积不存在固定的线性关系,其根本原因在于流域面积是度量衡单位,而不是影响因素。     

寒地黑土养分元素地球化学特征及丰缺评价——以抚远市为例

本文以黑龙江省抚远市为例,基于近年土地质量地球化学调查资料成果,采用地统计分析和GIS分析等相结合,揭示研究区黑土表层土壤中N、P、K、Ca、Mg等13项养分元素及土壤有机质的含量和分布特征及在不同土壤类型分布区含量特征,统计得出表层土壤养分元素背景值,并依据相关标准对各养分元素指标丰缺现状进行评价。研究结果表明,抚远地区表层土壤中有机质含量富足,N、P含量较丰富,K元素适中,Ca、Mg、B、Zn较缺乏,S、Fe、Mn、Cu元素含量分异较大,且等级中等以上均大于60%;土壤养分地球化学综合评价表明,该地区土壤养分丰富-较丰富约占77.1%,较缺乏区仅占1.2%,土壤肥力良好,可为该区现代农业发展和黑土地保护利用提供参考资料。     

Interaction of Different Iron Chelates with an Alkaline and Calcareous Soil: A Complementary Methodology to Evaluate the Performance of Iron Compounds in the Correction of Iron Chlorosis

Abstract

A great number of studies have shown that the stability of iron chelates as a function of pH is not the unique parameter that must be considered in order to evaluate the potential effectiveness of Fe‐chelates to correct iron chlorosis in plants cultivated in alkaline and calcareous soils. In fact, other factors, such as soil sorption on soil components or the competition among Fe and other metallic cations for the chelating agent in soil solution, have a considerable influence on the capacity of iron chelates to maintain iron in soil solution available to plants. In this context, the aim of this work is to study the variation in concentration of the main iron chelates employed by farmers under field conditions—Fe‐EDDHA (HA), Fe‐EDDHMA (MA), Fe‐EDDHSA (SA), Fe‐EDDCHA (CA), Fe‐EDTA (EDTA), and Fe‐DTPA (DTPA)—in the soil solution of a calcareous soil over time. To this end, soil incubations were carried out using a soil:Fe solution ratio corresponding to soil field capacity, at a temperature of 23°C. The soil used in the experiments was a calcareous soil with a very low organic matter content. The variation in concentration of Fe and Fe‐chelates in soil solution over time were obtained by measuring the evolution in soil solution of both the concentration of total Fe (measured by AAS), and the concentration of the ortho‐ortho isomers for Fe‐EDDHA and analogs or chelated Fe for Fe‐EDTA and Fe‐DTPA (measured by HPLC). The following chelate samples were used: a HA standard prepared in the laboratory and samples of HA, MA, SA, CA, Fe‐EDTA, and Fe‐DTPA obtained from commercial formulations present in the market. The percentage of iron chelated as ortho‐ortho isomers for HAs was: HA standard (100%); HA (51.78%); MA (60.06%); SA (22.50%); and CA (27.28%). In the case of Fe‐EDTA and Fe‐DTPA the percentages of chelated iron were 96.09 and 99.12, respectively. Results show that it is possible to classify the potential effectiveness of the different types of iron chelates used in our experiments as a function of two practical approaches: (i) considering the variation of total iron in soil solution over time, MA is the best performing product, followed by HA, CA, SA, DTPA, EDTA, and ferrous sulfate in the order listed and (ii) considering the capacity of the different iron chelates to maintain the fraction of chelated iron (ortho‐ortho isomers for HA, MA, SA, and CA and total chelated iron for EDTA and DTPA) in soil solution, the order is: SA > CA > HA > MA > EDTA ≈ DTPA. This result, that is related to the nature of the chelate and does not depend on the degree of chelated Fe in the products, indicates that SA and CA might be very efficient products to correct iron chlorosis. Finally, our results also indicate the suitability of this soil incubation methodology to evaluate the potential efficiency of iron compounds to correct iron chlorosis.     

Magnitude and Occurrence Probability of Soil Loss: A Risk Analytical Approach for the Plot Scale For Two Sites in Lower Austria

Long‐term contribution of soil loss events depends on both – the magnitude and the occurrence probability – but oftentimes, a limited observation period impedes the assessment of the temporal soil loss distribution. In this research, the event‐based soil loss from two plot locations in Lower Austria (Mistelbach and Pixendorf) was linked with the event‐based rainfall erosivity (EI₃₀) to assess the temporal soil loss distribution using long‐term rainfall data from two meteorological stations in Lower Austria. For both plot locations, a risk analysis was performed to (i) assess the long‐term average annual soil loss and to (ii) evaluate the contribution of incremental erosion events according to different event return periods. The risk analysis showed that in Pixendorf the events <20 years return period dominatingly contribute to long‐term soil loss, because the contribution of the events >20 years return period is progressively reduced through the low occurrence probability. On the contrary, in Mistelbach the soil loss magnitudes of the extreme events overcome the effect of the low occurrence probability, and consequently, the contribution of the extreme events (>20 years return period) is dominant. The spatially variable contribution of the erosion events reveals the need for spatially customized soil conservation strategies. A risk analytical approach may help to allocate the driving events and thus to define proper event design magnitudes for local soil conservation planning. Copyright © 2014 John Wiley & Sons, Ltd.     

Alterations in Soil Chemical Properties Induced by Continuous Rice Cultivation: A Study on the Arid Nile Delta Soils of Egypt

Changes in soil chemical properties resulting from continuous rice (Oryza sativa) cultivation on the Nile Delta soils of Egypt were examined. The eight soil profiles characterized for this study were designated as 0 (crop rotation without rice), 1 (crop rotation with rice after every 2 years), and 2, 3, 4, 5, 6, and 7 representing continuous rice cultivation for 2, 4, 8, 12, 15, and 20 years, respectively. Sampling was conducted at 0–20, 20–40, 40–60, and 60–80 cm depths for each profile and samples analyzed for a suite of chemical properties. Soil pH, salinity indicators [electrical conductivity (EC), and exchangeable sodium percentage (ESP)], as well as soluble and exchangeable cations and anions such as chloride and sulfate, all tended to decrease with years of continuous rice cultivation, with a number of significant (p < 0·05) differences observed. Cation exchange capacity (CEC) increased with years of continuous rice cultivation, with a 12% increase observed between 2‐ and 20‐year continuous rice cultivation systems. Principal component analysis conducted on soil properties within the continuous rice cultivation systems (profiles 2–7) revealed two possible components, namely F1 (pH, EC, ESP, and soluble Na⁺, Mg²⁺, K⁺, Cl⁻, and SO₄⁻²) and F2 (clay, organic matter, and CEC), which could be broadly associated to soil salinity and soil fertility, respectively. Findings suggested possible alterations in soil chemical properties by continuous rice cultivation practices on these Nile Delta soils of Egypt, Africa. Copyright © 2015 John Wiley & Sons, Ltd.     

Soil organic carbon stock variability in the Northern Gangetic Plains of India: interaction between agro‐ecological characteristics and cropping systems

Soil organic carbon (SOC) content and its spatial distribution in the Northern Gangetic Plain (NGP) Zone of India were determined to establish the cause–effect relationship between agro‐ecological characteristics, prevailing crop management practices and SOC stock. Area Spread Index (ASI) approach was used to collect soil samples from the NGP areas supporting predominant cropping systems. Exponential ordinary kriging was found most suitable geo‐statistical model for developing SOC surface maps of the NGP. Predicted surface maps indicated that 43.7% area of NGP had 0.5–0.6% SOC, while the rest of the area was equally distributed with high (0.61–0.75%) and low (< 0.5%) SOC content levels. Averaged across cropping systems, maximum SOC content was recorded in Bhabar and Tarai Zone (BTZ), followed by Central Plain Zone (CPZ), Mid‐Western Plain Zone (MWPZ), Western Plain Zone (WPZ) and South‐Western Plain Zone (SWPZ) of the NGP. The SOC stock was above the optimum threshold (> 12.5 Mg/ha) in 97.8, 57.6 and 46.4% areas of BTZ, CPZ and MWPZ, respectively. Only 9.8 and 0.4% area of WPZ and SWPZ, respectively, had SOC stock above the threshold value. The variation in SOC stock was attributed largely to carbon addition through recycling of organic sources, cropping systems, tillage intensity, crop or residue cover and land‐use efficiency, nutrient‐use pattern, soil texture and prevailing ecosystem. Adoption of conservation agriculture, balanced use of nutrients, inclusion of legumes in cropping systems and agro‐forestry were suggested for enhancing SOC stock in the region.     

气田开发工程水土流失特点与防治对策——以苏里格气田为例

结合苏里格3个气田开发工程的实际情况,对苏里格气田开发工程的组成、征占地面积、水土流失防治措施分别进行分析与评价,并通过经验总结,提出目前生产建设项目水土保持工作中存在的问题和不足。结果表明：1）气田工程项目组成较为复杂,占地以临时占地为主,占整个项目占地的75％左右;2）在水土流失防治分区中,以管网区与道路区所占比例最大,占整个项目占地的90％左右,同时也是整个项目中产生水土流失的重要部位,占整个项目水土流失量的90％左右,是水土流失防治与监测的重点部位。根据调查提出目前水土流失防治措施中存在的问题,并提出建设性意见和具体思路。     

重点生态功能区水土流失敏感性评价与分布研究—以贵州省雷山县为例

为了定量分析重点生态功能区雷山县水土流失敏感性现状,揭示其空间分布特征,识别出水土流失敏感性关键地域,也为县域水土流失综合防治和生态环境治理提供理论依据,研究选取2010年10月覆盖雷山县全域的ALOS遥感影像和1∶50 000地形图等为数据源,通过地理空间信息技术(RS和GIS技术)结合使用,运用3D Analyst栅格计算功能,提取雷山县DEM、坡度、坡向和土地利用等主要因子,运用ENVI软件,结合归一化植被指数模型,获取植被覆盖度,运用ArcMap空间叠加分析方法,划分出水土流失敏感性等级,得到研究区水土流失敏感性空间分布情况。结果表明,雷山县轻度及以上水土流失敏感性区域面积812.29km2,占总面积的67.45%,水土流失敏感性以轻度为主;强烈以上等级占总面积5.96%,所占面积小;同时研究区不同高程、坡向、坡度和植被覆盖度等级与水土流失敏感性之间存在显著关系,即轻度以上的水土流失敏感性区域面积出现先增大后减小的单峰分布;水土流失敏感性区域主要出现在高程为800~1 400m范围内,坡向为东南和西北,坡度为15°~35°,植被覆盖度在30%~45%的区域。