Spatial organization of multiple plant species in arid ecosystems:linking patterns and processes

Spatial organization of multiple plant species that appears as a non-random distribution of vegetative patches is one of the mostly observed spatial patterns in arid ecosystems. Yet understanding of ecological processes allowing this spatial pattern to emerge through interspecific interactions is still lacking. With a proposed conceptual model involving interspecific trade-offs between species competitive ability and colonization ability, we have argued that within patch abundance dynamics regulated by the mechanisms of competition are strongly influenced by the between patches colonization dynamics that are maintained via this trade-offs and it holds a positive, intraspecific occupancy-abundance relationship, in which increased patch occupancy increases species density within inhabiting patches. In a constant environment, while local abundance dynamics approach toward a stable equilibrium point, a fixed spatial arrangement of species can be retained through this coupled dynamics. However, in fluctuating environments where existence of such stable equilibriums is highly uncertain, it may involve continuous transitions from one community state to another as species re-organized themselves over space through the rapid changes in local species abundances. While some of the inhabiting patches are destroyed exogenously or endogenously, or species responses to increasing environmental fluctuations vary increasingly with time, discontinuous transitions into an abrupt, irreversible state of the community dynamics may occur, as with this effect the inherent positive relationship between occupancy and abundance of species is no longer maintained.

Evaluation and optimization of the spatial organization of the petrochemical industry in China

The spatial organization of the Chinese petrochemical industry was optimized according to the status of development of the industry employing linear programming and ArcGIS spatial analysis tools. We first identified the indexes of the spatial organization of the petrochemical industry and established a comprehensive evaluation index system that in- cludes four major categories and 11 indicators. The weight of each index was then deter- mined by the analytical hierarchy process. Afterward, taking the 337 Chinese prefecture-level administrations as basic units and scientifically evaluating the potential comprehensive layout coefficients of the cities, 151 prefecture-level administrative units were selected as the basis for the choice of optimization sites with a linear programming model. Secondly, using the 151 prefecture-level administrative units and the maximum-coverage model, the optimal number and spatial distribution of refineries were identified for service radii of 100, 200 and 300 km. Thirdly, considering the actual distribution of China＇s refineries, general rules for the number of refinery layout points and objective values were summarized, and 52 refinery layout points were selected for China. Finally, with ArcGIS spatial analysis tools, the spatial effect of the 52 optimal refinery layout points was simulated for the service scope and socioeconomic factors respectively, and the GDP and population data for each refinery layout point were then ex- tracted within the service scope. On this basis and with estimation of the intensity of crude-oil consumption, final results were obtained for the optimal spatial organization of the Chinese refining capacity and ethylene production capacity.

Spatial difference features and organization optimization of cities and towns in Tarim River Basin

This paper analyzes the urban spatial structure of Tarim River Basin from the perspectives of urbanization, urban density, grading scales and spatial evolution patterns, using geographical theories and methods, such as fractal theory, principle component analysis, urbanization imbalance index, urban scale imbalance indicator, and urban spatial interaction. The results show that the urban spatial structure displays balanced distribution in the overall pattern, while an imbalanced distribution in each region. The development of town pattern tends to be gathering to the central towns in the oasis of Tarim River Basin and a development axis has begun to form along the southern Xinjiang railway. Based on the division of urban hinterland, and the development characteristics of oasis economy, this paper puts forward an urban spatial organization model. This model uses 'breakpoint model' and divides Tarim River Basin into five urban clusters: Korla urban cluster, Kuqa urban cluster, Aksu urban cluster, Kashgar urban cluster and Hotan urban cluster. As a conclusion, this article puts forward an overall framework of urban spatial organization in Tarim River Basin: 'one axis, double core, and five groups'.

Chinese Unit Neighborhood Planning Strategies: A Case Study of Beijing

Chinese unit residential buildings can be understood as a flexible urban element, and theintroduction of its concept changed the urban structure of China. In this study, starting from the constraintsof contemporary planning contexts by Chinese historical units, the categories of historical Chinese unitresidential buildings were analyzed, and how spatial order and social ties has made Chinese units becomea common framework within which collective living takes place, how does the political strategy of theChinese government creates and constructs a particular form of spatial order in each example of Chineseunit residential buildings, and the impact on the daily life of the urban population were studied. Finally,how social relations, politics, and economic strategies confront and interact within Chinese unit residentialbuildings was explored.

Long-term agricultural activity affects anthropogenic soil on the Chinese Loess Plateau

Anthropogenic activities largely influence the soil quality of agricultural fields and the composition of soil. Samples of typical anthropogenic Loutu soil in the Guanzhong area of the Loess Plateau, Shaanxi Province, China were collected and measured for soil compaction, bulk density, total organic carbon（TOC）, active organic carbon（AOC）, and soil enzyme activities to investigate spatial variations in soil quality. The results indicate that soil compaction and bulk density increased with increasing distance from the farm village, whereas soil TOC, AOC, and soil enzyme activities firstly increased and subsequently decreased with increasing distance from the farm village. All of the tested parameters presented clear concentric distribution. Vertically, soil compaction and bulk density in the topsoil were lower than those in the subsoil, but all other tested parameters in the topsoil were significantly higher than those in the subsoil. In addition, there was a significant positive correlation between organic carbon content and enzyme activities, confirming that the spatial distribution of Loutu soil characteristics has been affected by long-term anthropogenic activities to some extent. The results of this study imply that the use of farmyard manure and appropriate deep plowing are important and effective ways to maintain and improve soil quality.

Versatile Magnetic Nanoparticles for Spatially Organized Assemblies of Enzyme Cascades:A Comprehensive Investigation of Catalytic Performance

Inspired by nature,precise spatial organization of enzyme cascades of interest is crucial to the improvement of catalytic performance.Herein,DNA scaffolds were introduced to construct a toolkit for versatile immobilization of enzyme pairs on dextran-coated magnetic nanoparticles(MNPs).After the glucose oxidase(GOx)and horseradish peroxidase(HRP)pair was immobilized through random cova-lent,DNA-directed and DNA tile-directed strategies,the immobilized GOx/HRP pair on the MNP-based carrier assembled with DNA tile(TD@MNPs)exhibited the highest activity due to rational spatial organization and less conformational change of constituent enzymes.With a decrease in interenzyme distance on TD@MNPs,furthermore,the catalytic efficiency of the HRP/GOx pair increased further for both substrates,2,2'-azinobis(3-ethyl-benzthiazoline-6-sulfonate)(ABTS)and 3,3',5,5'-tetramethyl benzidine(TMB).As the assembled HRP was closer to the carrier surface,the catalytic efficiency of the GOx/HRP pair increased by 6.2-fold for positively charged TMB and only by 62%for negatively charged ABTS compared with the free GOx/HRP pair.Moreover,a reversal of catalytic efficiency was found after the GOx/HRP pair was assembled on a positively charged carrier(TD@pMNPs).This research demonstrated that MNP-based car-riers had the potential to become a versatile toolkit for shedding an insight into catalytic performance and the development of new biocatalysts.

Immigrant Pantoea agglomerans embedded within indigenous microbial aggregates: A novel spatial distribution of epiphytic bacteria

Immigrant bacteria located on leaf surfaces are important to the health of plants as well as to people who consume fresh fruits and vegetables. However, the spatial distribution and organization of these immigrant bacteria on leaf surfaces are still poorly understood. To examine the spatial organization of these strains, two bacterial strains on tobacco leaves： （1） an indigenous strain, Pseudomonas stutzeri Nov. Y2011 labeled with green fluorescent protein, and （2） an immigrant strain Pantoea agglomerans labeled with cyan fluorescent protein isolated from pear, were studied. Under moist conditions, P. agglomerans cells quickly disappeared from direct observation by laser- scanning confocal microscopy, although elution results indicated that large amounts of live cells were still present on the leaves. Following exposure to desiccation stress, particles of cyan fluorescent protein-labeled P. agglomerans were visible within cracked aggregates of P. stutzeri Nov. Y2011. Detailed observation of sectioned aggregates showed that colonies of immigrant P. agglomerans were embedded within aggregates of P. stutzeri Nov. Y2011. Furthermore, carbon-resource partitioning studies suggested that these two species could coexist without significant nutritional competition. This is the first observation of an immigrant bacterium embedding within aggregates of indigenous bacteria on leaves to evade harsh conditions in the phyllosphere.

Influences of Planning Policies on Community Shaping in China: From Past to Present

In China, as in other countries of the world, communities, which are often considered as self-governing social organizations, are shaped and influenced by many factors. Different from other studies, this paper approaches the issue of community shaping from a planning perspective and tries to answer the questions of how Chinese communities have been physically shaped throughout history and what influences the planning policies have on communities’ scales, forms, and functions. Hereby, the planning policies concern not only the spatial organization, but also the social management of communities. The research is elaborated chronologically, dividing the history of community development in China roughly into four periods according to socio-economic development trends, planning objectives, and community characters. The narration is mainly based on literature work and case studies, with a focus on the social and spatial characters of urban communities. The paper concludes that before the modernization of China, Chinese communities were mainly shaped into a gated Li-Fang pattern by traditional city building principles, in accordance with the regulations on social management, in spite of the terminological changes in different dynasties and the opening of gated communities during certain dynasties. In the thirty years of the planned economy, Chinese communities were mainly shaped into inward Danwei(or work unit) communities of perimeter blocks by the urban planning institution, which was regarded as a technical tool of the planned socio-economic development to support national industrialization. In the next thirty years of economic transition, Chinese communities were further shaped into gated commodity housing communities of super blocks under the influence of reforms and the guidance of urban planning regulations. In the period of new urbanization, Chinese communities face the challenge of transforming towards a dense grid, with narrow streets and small blocks, and promoting public engagement in community building, in view of the requirements for quality-oriented development.

Detecting the storage and change on topsoil organic carbon in grasslands of Inner Mongolia from 1980s to 2010s

Soil carbon sequestration and potential has been a focal issue in global carbon research. Under the background of global change, the estimation of the size as well as its change of soil organic carbon（SOC） storage is of great importance. Based on soil data from the second national soil survey and field survey during 2011–2012, by using the regression method between sampling soil data and remote sensing data, this paper aimed to investigate spatial distribution and changes of topsoil（0–20 cm） organic carbon storage in grasslands of Inner Mongolia between the 1980 s and 2010 s. The results showed that：（1） the SOC storage in grasslands of Inner Mongolia between the 1980 s and 2010 s was estimated to be 2.05 and 2.17 Pg C, with an average density of 3.48 and 3.69 kg C·m–2, respectively. The SOC storage was mainly distributed in the typical steppe and meadow steppe, which accounted for over 98% of the total SOC storage. The spatial distribution showed a decreased trend from the meadow steppe, typical steppe to the desert steppe, corresponding to the temperature and precipitation gradient.（2） SOC changes during 1982–2012 were estimated to be 0.12 Pg C, at 7.00 g C·m–2·yr–1, which didn＇t show a significant change, indicating that SOC storage in grasslands of Inner Mongolia remained relatively stable over this period. However, topsoil organic carbon showed different trends of carbon source/sink during the past three decades. Meadow steppe and typical steppe had sequestered 0.15 and 0.03 Pg C, respectively, served as a carbon sink; while desert steppe lost 0.06 Pg C, served as a carbon source. It appears that SOC storage in grassland ecosystem may respond differently to climate change, related to vegetation type, regional climate type and grazing intensity. These results might give advice to decision makers on adopting suitable countermeasures for sustainable grassland utilization and protection.