酸杆菌是土壤中一类重要的细菌类群。基于16S rRNA基因序列分析发现，酸杆菌一般占细菌总量的20%左右，甚至高达50%以上，表明酸杆菌在土壤生态过程中起到重要的作用。从植被、海拔高度、氮肥管理及二氧化碳升高对土壤酸杆菌分布的影响，以及酸杆菌根际效应等几方面论述了土壤酸杆菌门细菌生态学研究进展；综合分析揭示出不同分类单元酸杆菌细菌分布与环境因子间的关系；阐述了部分酸杆菌细菌的潜在生态功能。最后指出在土壤酸杆菌研究中应强化分离培养、细化分子生态、采用宏基因组学和单细胞测序新技术的重要性。

\n Cotton (\n Gossypium hirsutum\n L.) monoculture under conventional tillage has been the predominant cropping system in the Southern High Plains region of the United States since the 1940s. This study evaluated other cropping systems and land uses for their potential to increase soil quality and enhance soil functioning compared with continuous cotton (Ct‐Ct), including a mixture of grasses in the Conservation Reserve Program (CRP), a pasture monoculture [\n Bothriochloa bladhii\n (Retz) S.T. Blake] and a cotton–winter wheat (\n Triticum aestivum\n L.)–corn (\n Zea mays\n L.) rotation (Ct‐W‐Cr). Soil microbial communities were evaluated according to microbial biomass C (MBC) and N (MBN), fatty acid methyl ester (FAME) profiling, and molecular cloning techniques. Soil MBC was higher under the alternative systems at 0 to 5 cm (CRP > pasture = Ct‐W‐Cr > Ct‐Ct), 5 to 10 cm (CRP = Ct‐W‐Cr > pasture > Ct‐Ct), and 10 to 20 cm (CRP = pasture = Ct‐W‐Cr > Ct‐Ct). Soil DNA concentration was correlated with key soil quality parameters such as microbial biomass (\n r\n > 0.52,\n P\n < 0.05), total C (\n r\n = 0.372,\n P\n < 0.1), and total N (\n r\n = 0.449,\n P\n < 0.05). The 16S rRNA gene banding patterns (0–5 cm) of undisturbed systems (CRP and pasture) were more similar to each other than to Ct‐Ct and Ct‐W‐Cr. Fungal/bacterial FAME ratios were higher under CRP and pasture than under Ct‐Ct at 0 to 5 and 5 to 10 cm. This study found increases in sensitive soil quality parameters under alternative management compared with cotton monoculture.\n

Analyzing spatiotemporal changes in land use and land cover could provide basic information for appropriate decision-making and thereby plays an essential role in promoting the sustainable use of land resources, especially in ecologically fragile regions. In this paper, a case study was taken in Zhenlai County, which is a part of the farming-pastoral ecotone of Northern China. This study integrated methods of bitemporal change detection and temporal trajectory analysis to trace the paths of land cover change for every location in the study area from 1954 to 2005, using published land cover data based on topographic and environmental background maps and also remotely sensed images including Landsat MSS (Multispectral Scanner) and TM (Thematic Mapper). Meanwhile, the Lorenz curve and Gini coefficient derived from economic models were also used to study the land use structure changes to gain a better understanding of human impact on this fragile ecosystem. Results of bitemporal change detection showed that the most common land cover transition in the study area was an expansion of arable land at the expense of grassland and wetland. Plenty of grassland was converted to other unused land, indicating serious environmental degradation in Zhenlai County during the past decades. Trajectory analysis of land use and land cover change demonstrated that settlement, arable land, and water bodies were relatively stable in terms of coverage and spatial distribution, while grassland, wetland, and forest land had weak stability. Natural forces were still dominating the environmental processes of the study area, while human-induced changes also played an important role in environmental change. In addition, different types of land use displayed different concentration trends and had large changes during the study period. Arable land was the most decentralized, whereas forest land was the most concentrated. The above results not only revealed notable spatiotemporal features of land use and land cover change in the time series, but also confirmed the applicability and effectiveness of the methodology in our research, which combined bitemporal change detection, temporal trajectory analysis, and a Lorenz curve/Gini coefficient in analyzing spatiotemporal changes in land use and land cover.