我们利用宏基因组技术研究了玉米种植模式、土壤性质和地理位置对中国4个玉米主产区土壤原核生物群落的影响。在本研究所有土壤样品中，α-变形菌纲、γ-变形菌纲、β-变形菌纲、芽单胞菌纲、酸杆菌纲和放线菌纲是共同优势原核生物类群。非度量多维尺度法分析发现，原核生物群落划分4个组，且与4个玉米种植区相吻合。冗余分析表明，土壤性质(尤其是pH)、地理位置和种植模式共同影响土壤原核生物群落多样性，而地理位置（纬度）、pH和种植模式影响土壤原核生物功能基因。4个玉米生产区土壤原核生物某些代谢途径中的功能基因丰度差异显著，如微生物-微生物相互作用、芳香化合物降解、原核生物固碳途径和微生物在不同环境中代谢等。总之，土壤pH、种植制度和地理位置三者共同影响了我国4个玉米主产区土壤原核生物群落和功能基因。研究结果有助于深入了解大尺度农业生态系统中土壤原核生物群落的组成和基因功能。

The expression of mitogen-activated protein kinase (mapk) double-stranded RNA in cucumber is effective in controlling infestations of the root-knot nematode Meloidogyne incognita.  However, little is known about the ecological effects of transgenic plants.  Here, we analyzed the diversity of 16S rDNA genes derived from the rhizosphere archaea of transgenic cucumber plants as an indicator of ecological change.  A total of 17 and 18 operational taxonomic units were detected in the rhizospheres of non-transgenic cucumber and mapk dsRNA-expressing plants, respectively.  No significant difference was observed between the two groups according to Shannon and Simpson indices.  In soil samples of the two rhizospheres, the dominant group was Crenarchaeota at the phylum level, with Staphylothermus, Methanococcus, Pyrodictium and Sulfolobus the abundant taxa at the genus level.  These results suggest that expressing mapk double-stranded (ds) RNA in cucumber has no apparent effect on the diversity of rhizosphere archaea, and provide powerful evidence for the ecological safety of transgenic cucumber expressing mapk dsRNA.   

This article analyses the technical and environmental efficiency of hog production in China using data from the China Agricultural Product Cost-Benefit Compilation (NDRC 2005–2013) and the First National Census of Pollution: Manual of Discharge Coefficient of Livestock and Poultry Industry (IEDA and NIES 2009). The empirical results show a great variation in environmental efficiency, ranging from 0.344 to 0.973 with a mean value of 0.672 that declines over time. Southwest China is found to be the most environmentally efficient region, while the Northeast and the Northwest are the least efficient. Another finding is that technical and environmental efficiencies are highly correlated in hog production; the most environmentally efficient regions are usually found to have high technical efficiency, and vice versa. In addition, we computed the output elasticities with respect to each factor input. The results show that feed is the most efficient input, with an output elasticity of approximately 0.551, which is much higher than the elasticity of the nitrogen surplus, other capital or labour. The output elasticity with respect to the nitrogen surplus is 0.287 on average. Finally, the scale elasticity in hog production is slightly higher than 1.

China’s hog production is undergoing a great transformation due to the soaring demand and changing raising system. Regarding the essential role of pork in Chinese diet, a systematic analysis on the productivity and efficiency of hog production can provide significant implications for policy makers. This paper investigates the productivity and efficiency of hog production and the determinants of technical efficiency in China using a household level panel data (2004–2010). A stochastic frontier translog production function with scaling property in inefficiency term is adopted for hog production analysis, and the determinants of technical efficiency are incorporated in a one-step estimation using maximum likelihood estimation. Our results show that the average technical efficiency of hog production in China is 0.5914. More importantly, we find that specialized farmers have higher technical efficiency than others, and technical efficiency in the eastern region is higher than that in Central and West China.