A comprehensive analysis of the response of the fungal community structure to long-term continuous cropping in three typical upland crops

Certain agricultural management practices are known to affect the soil microbial community structure;however,knowledge of the response of the fungal community structure to the long-term continuous cropping and rotation of soybean,maize and wheat in the same agroecosystem is limited.We assessed the fungal abundance,composition and diversity among soybean rotation,maize rotation and wheat rotation systems and among long-term continuous cropping systems of soybean,maize and wheat as the effect of crop types on fungal community structure.We compared these fungal parameters of same crop between long-term crop rotation and continuous cropping systems as the effect of cropping systems on fungal community structure.The fungal abundance and composition were measured by quantitative real-time PCR and Illumina MiSeq sequencing.The results revealed that long-term continuous soybean cropping increased the soil fungal abundance compared with soybean rotation,and the fungal abundance was decreased in long-term continuous maize cropping compared with maize rotation.The long-term continuous soybean cropping also exhibited increased soil fungal diversity.The variation in the fungal community structure among the three crops was greater than that between long-term continuous cropping and rotation cropping.Mortierella,Guehomyces and Alternaria were the most important contributors to the dissimilarity of the fungal communities between the continuous cropping and rotation cropping of soybean,maize and wheat.There were 11 potential pathogen and 11 potential biocontrol fungi identified,and the relative abundance of most of the potential pathogenic fungi increased during the long-term continuous cropping of all three crops.The relative abundance of most biocontrol fungi increased in long-term continuous soybean cropping but decreased in long-term continuous maize and wheat cropping.Our results indicate that the response of the soil fungal community structure to long-term continuous cropping varies based upon crop types.

SORPTION AND DESORPTION CHARACTERISTICS OF CADMIUM BY FOUR DIFFERENT SOILS IN NORTHEAST CHINA

Four soils, phaeozem (PM), saline-alkali soil (SA), meadow albic bleached soil (MA) and dark brown forest soil (DB) from Northeast China were used to examine the sorption and desorption characteristics of Cd and pH influence on it. According to sorption experiment without pH control, the order of amount of absorbed Cd by soils was: SA>PM>DB>MA. The results from non-linear fitting method showed that Langmuir and Freundrich models were more adaptable than Temkin model in describing the sorption data. The maximum sorption amounts from Langmuir model were: PM>SA>MA>DB. Exponential equation for PM and SA and quadratic equation for MA and DB were suitable to fit the desorption data. The order of average desorption percentage was: MA>DB>PM>SA. The amounts of sorption by PM, DB and MA reached the maximum in pH 9.0, while sorption by SA was linearly increased in the experimental range of pH 3.3-11.4. In uniform pH, however, Cd sorption by SA was the minimum among four soils, which indicated that the more amounts of Cd absorbed by SA in isotherm sorption were ascribed to the higher soil pH. The higher sorption of Cd in PM resulted from the higher percentage of organic matter and clay components.

石油钻井现场工作开展的相关安全管理方案

针对石油钻井现场工作安全管理相关内容,做了简单的论述,提出了安全管理措施。安全是钻井作业管理的核心内容,由于钻井现场工作环境复杂,存在着诸多不安全因素,增加了安全管理的难度,因此需要结合现场实际情况,采取针对性安全管控措施。

Coupling of a T12Ba2CaCu2O8 Thin Film Intrinsic Josephson Junction and a Fabry-Perot Resonator

We study the electromagnetic coupling mechanism of a T1_(2)Ba_(2)CaCu_(2)O_(8)(TI-2212)thin film intrinsic Josephson junction to a hemispherical Fabry-Perot resonator.An effective model to analyze coupling mechanism is put forward.The dielectric substrate is used as a dielectric resonator antenna and the Josephson junction,and a superconducting film is used as the feed line to excite a resonance mode inside the dielectric resonator antenna.To confirm this method,two Josephson junction samples with different dimensions of substrate and shapes of superconducting film are fabricated and tested under microwave irradiations.At the same time,numerical simulations of the antenna characteristics and the field distribution of these samples are performed by numerical simulation.The different coupling intensities of the two samples with the Fabry Perot resonator fit well with the numerical simulation results.The proposed model is important for Josephson junctions used in the microwave field.

陆地农业生态系统丛枝菌根真菌物种多样性研究进展

丛枝菌根真菌(AMF)是一种古老的、在自然界中普遍存在的土壤微生物,能与大部分陆生植物形成互惠互利的菌根共生体.在这种共生关系中,AMF从植物获取自身生长所需碳源的同时,帮助宿主吸收氮、磷等营养物质.AMF在农业生态系统中具有重要作用,能够促进植物生长、改善作物品质、提高植物抗逆性、稳定土壤结构、维护生态平衡和维持农业可持续发展.本文总结了近几年来陆地农业生态系统AMF的研究进展,着重从我国陆地农业生态系统AMF物种多样性、AMF生物多样性时空分布特征及影响AMF多样性的因素等几个方面,综述了陆地农业生态系统AMF的物种多样性,并对以后的研究进行了展望.