Long term impact of mineral amendment on the distribution of the mineral weathering associated bacterial communities from the beech Scleroderma citrinum ectomycorrhizosphere

Liming is a known forest management procedure used to amend nutrient-poor soils such as soils of acidic forests to rectify cation deficiencies and to restore soil pH. However, although this procedure is well known for its beneficial effect on the forest trees, its relative impact on the functional and taxonomic diversity of the soil bacterial communities has been poorly investigated. In this study, we characterized the ability of the soil bacteria to weather soil minerals and to hydrolyze chitin. A collection of 80 bacterial strains was isolated from the Scleroderma citrinum ectomycorrhizosphere and the adjacent bulk soil in two stands of mature beeches (Fagus sylvatica) developed on very acidic soil and presenting two levels of calcium (Ca) availability: a control plot as well as a plot amended with Ca in 1973. All the bacterial isolates were identified by partial 16S rRNA gene sequence analysis as members of the genera Burkholderia, Bacillus, Dyella, Kitasatospora, Micrococcus, Paenibacillus, Pseudomonas, and Rhodanobacter. Using a microplate assay for quantifying the production of protons and the quantity of iron released from biotite, we demonstrated that the bacterial strains from the amended plot harbored a significant higher mineral weathering potential that the ones isolated from the control plot. Notably, the weathering efficacy of the ectomycorrhizosphere bacterial isolates was significantly greater than that of the bulk soil isolates in the control treatment but not in the amended plot. These data reveal that forest management, here mineral amendment, can strongly affect the structure of bacterial communities even over the long term.     

Stoichiometry of base cations and silicon during weathering of a deep soil profile derived from granite

Evaluation of the stoichiometry of base cations (BCs, including K⁺, Na⁺, Ca²⁺, and Mg²⁺) and silicon (Si) (BCs:Si) during soil mineral weathering is essential to accurately quantify soil acidification rates. The aim of this study was to explore the differences and influencing factors of BCs:Si values of different soil genetic horizons in a deep soil profile derived from granite with different extents of mineral weathering. Soil type was typic acidi-udic Argosol. Soil samples were collected from Guangzhou, China, which is located in a subtropical region. To ensure that the BCs and Si originated from the mineral weathering process, soil exchangeable BCs were washed with an elution treatment. The BCs:Si values during weathering were obtained through a simulated acid rain leaching experiment using the batch method. Results showed that soil physical, chemical, and mineralogical properties varied from the surface horizon to saprolite in the soil profile. The BCs:Si values of soil genetic horizons during weathering were 0.3-3.7. The BCs:Si value was 1.7 in the surface horizon (A), 1.1-3.7 in the argillic horizon (Bt), and 0.3-0.4 in the cambic (Bw) and transition (BC) horizons, as well as in horizon C (saprolite). The general pattern of BCs:Si values in the different horizons was as follows: Bt > A > Bw, BC, and C. Although BCs:Si values were influenced by weathering intensity, they did not correlate with the chemical index of alteration (CIA). The release amounts of Si and BCs are the joined impact of soil mineral composition and physical and chemical properties. A comprehensive analysis showed that the BCs:Si values of the soil derived from granite in this study were a combined result of the following factors: soil clay, feldspar, kaolinite, organic matter, pH, and CIA. The main controlling factors of BCs:Si in soils of different parent material types require extensive research. The wide variance of BCs:Si values in the deep soil profile indicated that H⁺ consumed by soil mineral weathering was very dissimilar in the soils with different weathering intensities derived from the same parent material. Therefore, the estimation of the soil acidification rate based on H⁺ biogeochemistry should consider the specific BCs:Si value.     

Effect of Addition of Al Hydroxides on Changes in Dispersibility and Charge Characteristics of Soils

Using a soil from a newly reclaimed area where high dispersibility of fine particles had led to poor physical properties in the field, changes in dispersibility and charge characteristics after artificial precipitation of Al hydroxides onto the soil were investigated. Al hydroxides were precipitated by neutralization with NaOH of an acidic A1C1₃ solution in which the soil samples were placed.

When the titration rates were changed, no significant differences in dispersibility were observed in the resultant soils. In the systems with the addition of 2 g kg^-1 or less of A1(OH)₃, dispersion ratios of clays were almost identical with those of blank samples although the specific surface areas were reduced. In the systems with 5 g kg^-1 or more of A1(OH)₃, considerable effects of Al hydroxides on reduction of clay dispersibility were recognized (e.g. 10 g kg^-1 addition yielded less than one-third of the original ratio of the clay dispersion). A slightly larger decrease in dispersion was observed by the addition of 15 g kg^-1 or more. As the amount of added Al increased, the amount of negative charges of the soil decreased while that of positive charges increased. The charge characteristics of the system with the addition of 20 g kg^-1 of A1(OH)₃ were closer to those of the adjacent forest soil which was characterized by a very low dispersibility. It was inferred that added Al hydroxides polymerized to form Al polycation species that were not readily exchangeable, neutralizing negative charges of clays, and acting as interparticle bonding between the clays. On the other hand, forest soils were considered to have acquired a physical stability against the dispersion of fine particles as free Al oxides had been accumulated in the process of natural weathering. It was concluded that charge characteristics primarily determined the dispersion and flocculation behavior of soils and that Al hydroxides were important modifiers of charge characteristics of soils.     

论地质条件对某水电站坝型选择的影响

某水电站的地质条件比较复杂,在前期地质工作不足的条件下,认为在此处的工程地质条件总体较优,混凝土拱坝和心墙堆石坝都比较适合;随着坝址区地质勘测的深入,在分析研究了重力坝与拱坝方案存在的主要工程地质问题后,进而比较了上述坝型地质条件的各自利弊,最后推荐了心墙堆石坝.     

海南岛火山岩砖红壤铁质风化壳主量元素特征[1]

通过对海南岛西北部火山岩砖红壤铁质风化壳剖面样品进行X荧光光谱法检测、风化特征指数及质量迁移系数的计算,揭示海南岛新生代火山岩砖红壤铁质风化壳的主量元素分布、风化强度和迁移特征。风化壳主量元素以Fe2O3、Al2O3、SiO2为主,K、Na、Ca、Mg等易溶组分较低;Fe2O3、Al2O3富集、SiO2淋失的热带地区风化特征。风化层CIA指数高达95%以上、Fe2O3/Al2O3上升,BA值较低, SiO2/Al2O3、SiO2/R2O3、BA下降;以Zr为参比元素,铁、铝迁移系数大于1,最大可达4.029,钠、钾、钙、镁、硅、锰迁移系数小于1,可低至-0.996。研究认为海南岛西北部火山岩风化壳表现为典型的脱硅富铁,铁质元素强烈富集,其它元素淋失明显,且铁铝元素发生了的分异,是比较成熟的风化壳。     

Changes in surface properties of tropical wood species exposed to the Indonesian climate in relation to mold colonies

Changes in mold populations and genera on the exposed surfaces of tropical hardwoods — albizia (Paraserianthes falcata), kapur (Dryobalanop lanceolata), mahoni (Switenia macrophylla), nangka (Artocarpus heterophyllus), puspa (Schima wallchii) — were investigated. The wood specimens were exposed to the Indonesian climate for 32 weeks. Properties including mass loss, wettability, mold growth (colony-forming units), and mold genera were evaluated. The change in properties after exposure was significantly affected by the wood species, but there was no clear relation between mass loss and the initial chemical components or between wettability and wood density. The number of mold populations was different by exposure period and wood species, but there was no significant effect of climate conditions, such as rainfall and ultraviolet radiation. Of the genera identified,Aureobasidium, Cladosporium, andPenicillium were dominant molds on the exposed wood surfaces.     

Genese von Lockerbraunerden im Bayerischen Wald

Distribution and genesis of Loose Brown Earths in the Bayerischer Wald In the Hinterer Bayerischer Wald (Germany) Lockerbraunerden (Loose Brown Earths, FAO: Dystric Cambisols) widely occur, which differ with their bright orangebrown coloured Bfv-horizons obviously from the yellowish or dark brown Bv-horizons of the Brown Earths (FAO: Cambisols). Our investigations show, that they differ also mineralogically significantly from the Bv-horizons of the Brown Earths, namely in their contents of poorly crystallized iron oxides (sequential extraction). We deduce from the high contents of oxalate soluble iron, that ferrihydrite minerals, are responsible for the characteristic morphological and physical properties of this type of soil.     

Initial soil development in lignite ash landfills and settling ponds in Saxony‐Anhalt,Germany

Weathering and initial soil formation was investigated on 5 sites of lignite ash disposal differing in age (5 to 30 years) and methods of disposal (landfills and sluicing to settling ponds). Soils developed on lignite ash derived substrates were characterized by low bulk densities (< 0.85 g cm^—3), high contents of gypsum (maximum 27%) and calcium carbonate (maximum 46%), high pH values (7—9), very high contents of organic carbon (about 20%), and high contents of ammonium oxalate soluble Si, Al, and Fe containing compounds. These features depended on the constitution of the lignite and the burning conditions. As the substrates were initially in disequilibrium with their environmental surroundings, they were subjected to rapid weathering. Typical features were the depletion of gypsum and decarbonatization in the topsoils of the profiles. Furthermore, pedogenic organic carbon became enriched by ruderal vegetation despite low contents of plant available P and K and high pH values. The C : N ratios increased with profile depth, which indicated the input of pedogenic OM with low C : N ratios into topsoils and the predominance of lignite with a wide C : N ratio (> 100) in subsoils.     

Effects of silicate weathering and lessivage on K‐content in forest soils derived from Pleistocene sediments

The potassium (K) content of soils developed from Pleistocene calcareous till, glacial sand and loess in NW Germany was investigated in order to characterize stores of K in feldspars (K_feldspar) and mica/illite (K_mica/illite) as well as changes as a function of soil depth. From each horizon, up to seven sand, six silt and three clay fractions were separated. K_feldspar and K_mica/illite were quantified by means of chemical composition and estimation by IR‐spectroscopy. On account of distinct differences in mineralogical composition between different particle size fractions, K‐content of the bulk soil < 2000 μm and the proportion of K_mica/illite and K_feldspar are clearly related to grain size distribution of the sample. Generally, the K‐content of particle size fractions of a soil derived from calcareous till is significantly higher than that of a soil from glacial sands. K_mica/illite of clay and silt fractions increases with depth, reflecting greater mica/illite weathering at the soil surface, whereas K_feldspar shows no noticeable change. Illite accumulates by lessivage in Bt horizons. On a whole‐soil basis, the Bt horizons of Luvisols derived from loess and calcareous till contain more K_mica/illite than either the A or the C horizons. By comparing the K‐content in the different particle size fractions with soil depth, the highest rate of change is found for soils derived from glacial sand. Gains in K in the silt fractions of soils from calcareous till and glacial sand result from weathering of feldspar sand grains. Additionally, decomposition of feldspar‐containing rock fragments of gravel size, and aeolian sedimentation, may also have contributed to these gains.     

一株高效溶解钾长石芽孢杆菌的分离鉴定与生物学特性研究

从风化的钾质粗面岩表面分离筛选到1株高效风化钾长石的芽孢杆菌E31菌株,通过菌株的生理生化特征并结合菌株16S r DNA序列分析,E31菌株被鉴定为苏云金芽孢杆菌(Bacillus thuringiensis)。同时对E31菌株溶解钾长石的效应与机制以及生物学特性进行了研究。结果表明,E31菌株能风化钾长石并释放出其中的元素,28℃振荡培养不同时间,接菌处理发酵液中可溶性K、Fe、Ca、Al含量分别比对照提高了19.6%~25.6%、1~12.5倍、10.4%~47.2%和1.2~4.5倍。在钾长石存在条件下接菌处理发酵液pH为3.62~3.80,发酵液中葡萄糖酸含量达61~1 794 mg/L,发酵液细胞数量达(8.7~16.1)×10~6 cfu/ml,表明菌株可以通过代谢产生的有机酸来加速对钾长石的分解作用。另外,E31菌株能够合成生长素和铁载体,E31菌株对温度、pH和盐浓度具有较强的耐受性。