Root–soil adhesion as affected by crop species in a volcanic sandy soil of Mexico

Field observations have shown that root residues maintain root-adhering soil for several months after harvest. The aim of this work was to compare post-harvest effect of Amaranthus hypochondriacus (amaranth), Phaseolus vulgaris (common bean) and Zea mays (maize) roots on root-adhering soil, aggregation and organic carbon content. The experimental site was located on a volcanic sandy soil (Typic Ustifluvent) in the Valley of Mexico. In 1999 and 2000, maize had the highest root mass (92 and 94 g m⁻²) and the highest root-adhering soil (9051 and 5876 g m⁻²) when a root–soil monolith of 0.20 m × 0.20 m × 0.30 m was excavated after harvest. In contrast, bean roots (2 and 5 g m⁻²) had only 347 and 23 g m⁻² of adhering soil per monolith in each year. Amaranth had intermediate values between maize and bean. Dry soil aggregate classes (<0.25, 0.5, 1, 2, 5 and >5 mm) were similarly distributed among the three species. The sum of the three soil macro-aggregates classes >1 mm was 0.1 g g⁻¹ in both years. Neither water stability of the 2–5 mm aggregates (0.05–0.09 g g⁻¹) nor soil organic C (SOC) in three aggregate classes (<0.25, 1–2 and >5 mm; mean 14.6 mg g⁻¹) was affected by species (P < 0.05) in either year. Observations of thin sections (10× and 40×) revealed absence of macro-aggregates under maize. Soil compaction was attributed to high mass of maize roots in the sampled soil volume. Root systems sampled after harvest had the capacity to maintain a well structured soil mass, which was proportional to root mass. Root-adhering soil measured in the field could be used to select species promoting soil adhesion by roots.     

Micromorphological evidence of paleoenvironmental changes in Northern Cilento (South Italy) during the Late Quaternary

Three representative soil profiles developed during the Late Quaternary in Northern Cilento (South Italy) were studied by optical microscopy and SEM-EDS observation of thin sections to examine soil features as evidence for past climatic fluctuations.Two of the profiles are polygenetic and the third monogenetic. All these have a clear interglacial imprint, whereas the polygenetic profiles also contain other features, which can be related to periglacial conditions during the stadial glacial periods although in midlatitude coastal areas. All the paleosols show a strong marine influence during development, which probably resulted from windblown processes or submergence during past interglacial phases.     

土壤胶膜的研究进展

土壤胶膜是土壤中普遍存在的形成物,其性质与整个土体有较大的变异和不同,对土壤的物质流和能量流、生产力和植物营养以及土壤质量等有重要影响。本文从土壤胶膜的成因、分类、微形态特征、物质组成及其对土壤性质的影响,土壤胶膜与土壤发生与分类、古气候等的关系,探讨了土壤胶膜的研究进展,并展望了以后可能的研究趋势。     

The use of micromorphology in soil pollen analysis: The interpretation of the pollen content of slope deposits in Galicia, Spain

Humic horizons of soil profiles often contain pollen and spores. Comparison of the sequence of pollen associations of soil profiles with pollen zones of reference diagrams offers palyno-ecological information, relevant for reconstruction of landscape ecological development. In palynological studies of semiterrestrial and aquatic deposits, pollen is considered to be part of the sediment and anaerobic conditions in water-saturated deposits promote its conservation. This is not true for pollen in soils. Aerobic conditions in drained soils result in bio-oxidation of unprotected pollen grains. Interpretation of soil pollen associations requires knowledge of the processes of infiltration and conservation of pollen grains in the soil material. Micromorphology is an important technique to investigate these processes. This is demonstrated in a case study of polycyclic slope deposits in Galicia (Spain). The buried cambisols, in pleistocene solifluction deposits, contain post-sedimentary infiltrated pollen. The pollen associations reflect successive phases in soil ecological development. The holocene colluvial deposits contain syn-sedimentary incorporated pollen. The pollen associations reflect environmental conditions during the deposition of colluvial layers.     

4种葱蒜类蔬菜种子表皮微形态的研究

本研究首次对4种葱蒜类蔬菜种子表文报形态进行了电镜扫描观察,发现韭菜、大葱、洋葱、韭葱之间,种子表皮微形态特征有明显差异,可以根据种子表皮微形态特征准确鉴别这4种蔬菜作物的种子。     

Soil surface drip point features: an integrated approach using analytical photogrammetry and soil micromorphology

This study considers changes occurring on a soil surface after exposure to simulated rainfall. The soil surface in question has a crop cover of artificial maize, and interest focuses specifically on the surface features produced by leaf drips. An analytical photogrammetric approach is used to examine surface morphological change at a small scale (1 mm). These topographical changes are then related to sub-surface crust development as observed by the use of impregnated polished blocks. For the first time therefore soil surface and soil sub-surface changes are integrated together in one study. The results reveal a ‘cut and fill' type process in which aggregate welding and breakdown operate in parallel.     

Tree influence on soil biological activity: What can be inferred from the optical examination of humus profiles?

Humus forms may vary in different forest stands, but the local influence of trees upon soil microbial and faunal activities is still imperfectly known. Optical methods could help to discern processes of litter transformation and formation of organo-mineral assemblages, allowing a better diagnostic of tree influences upon humus-soil development. The microstratification of humus was studied under a beech (Fagus crenata), a mixed oak forest (Quercus crispula and Quercus serrata), and a cedar (Cryptomeria japonica) plantation. The three sites are located in Kyoto (Japan), and share similar environmental conditions. Litter decomposition rates and soil fauna were also investigated. At the beech site, which had the thickest O horizon, the main process was the gradual fragmentation of litter. This process, together with shallow root and weak fungal development, gave rise to a stable sandwich-like structure in the O horizon. In contrast, the oak site showed a two-step transformation of litter. Initially, litter decomposition was triggered by the activity of white rot fungi, and the discarded litter decayed much more slowly thereafter. The cedar site exhibited a sharp vertical delineation between upper thick Oe horizon developed since plantation time and a relict A horizon. The optical method thus demonstrated differences in soil biological activities and litter transformation patterns under the three sites.     

关中东部地区退耕还林对土壤微形态的影响研究

用偏光显微镜和Sisc Ias V8.0软件对关中东部典型农耕地和花椒园土壤的微形态进行观察和分析,结果表明:耕地和花椒园土壤有相同的剖面构型Ap1-Ap2-BC;粗颗粒矿物组合均以石英和长石占优势;与耕地相比,花椒园土壤的有机质含量增多,粗颗粒趋于变小变圆的程度降低,C/F(10μm)值较大;残积黏土和无定形铁含量增加,孔隙所占比例增加。这说明短时间内退耕还林对土壤剖面的构造和矿物组合影响不明显,但是对土壤微形态有显著影响;花椒园土壤更有利于旱塬地区土壤的吸水和保水,使其有机质含量增加。     

Development and origin of the microgranular structure in latosols of the Brazilian Central Plateau: Significance of texture,mineralogy, and biological activity

Brazilian Latosols are characterized by low activity clay, little horizon differentiation, a weak macrostructure and a strong microgranular structure. The development of the latter that was reported as being possibly related to the fine material mineralogy, location in the landscape, parental material and biological activity is still under discussion. The aim of this study is to discuss the origin of the microgranular structure of Latosols located in the Brazilian Central Plateau. Ten Latosols (L) developed in different parent materials were selected along an approximately 350-km long regional toposequence across the South American Surface (SAS) (L1 to L4) and Velhas Surface (VS) (L5 to L10). The structure of the Latosols was studied in the field and samples of the diagnostic Bw horizons were collected for laboratory analyses. Basic soil characterization was performed on the < 2-mm material according to the Brazilian standard procedures. The SiO₂, AL₂O₃, Fe₂O₃ and TiO₂ content was determined after dissolution with 1:1 H₂SO₄. The microstructure was studied in optical microscopy and scanning electron microscopy in thin sections. The results showed a varying compound strong microgranular structure and weak to moderate medium sub-angular blocky structure independently of the landscape position as well as the parental material, except for the Latosol developed on a quartzite. The Latosols were classified as gibbsitic-sesquioxidic, kaolinitic non-sesquioxid, or kaolinitic-sesquioxid Latosols but there was no relationship between their composition and the development of the microgranular structure in the Bw horizon. The analyses showed indeed several types of microgranular structure with different proportions but without any relationship with their texture and mineralogy. Actually, the types of microgranular structure appeared to be mainly related to soil bioturbation by termites and eventually secondarily by ants. Thus, the weak macrostructure and strong microgranular structure of the Latosols studied, the little vertical differentiation of the horizons, and the lack of a clear relationship between their landscape position and parent material characteristics would result from long-term biotic action with high probability.     

委陵菜属植物叶表皮微形态及其与环境关系

[目的]研究叶表皮特征在委陵菜属植物分类中的应用价值,同时对其与环境的关系进行讨论。[方法]利用光学显微镜对大庆地区9种委陵菜属植物叶表皮的形态特征及其与环境关系进行了观察和研究。[结果]9种委陵菜表皮细胞为多边形、近多边形和不规则形状;垂周壁式样出现近平直、弧形、浅波形和波形的分化;气孔器均为无规则型,随机分布;表皮毛有3种类型：单细胞直的不分枝毛、单细胞卷曲不分枝毛和腺毛。[结论]该研究为委陵菜属植物的系统分类及合理开发利用提供了更丰富的资料和依据。