Example-based image colorization using locality consistent sparse representation

—Image colorization aims to produce a natural looking color image from a given grayscale image, which remains a challenging problem. In this paper, we propose a novel examplebased image colorization method exploiting a new locality consistent sparse representation. Given a single reference color image, our method automatically colorizes the target grayscale image by sparse pursuit. For efficiency and robustness, our method operates at the superpixel level. We extract low-level intensity features, mid-level texture features and high-level semantic features for each superpixel, which are then concatenated to form its descriptor. The collection of feature vectors for all the superpixels from the reference image composes the dictionary. We formulate colorization of target superpixels as a dictionary-based sparse reconstruction problem. Inspired by the observation that superpixels with similar spatial location and/or feature representation are likely to match spatially close regions from the reference image, we further introduce a locality promoting regularization term into the energy formulation which substantially improves the matching consistency and subsequent colorization results. Target superpixels are colorized based on the chrominance information from the dominant reference superpixels. Finally, to further improve coherence while preserving sharpness, we develop a new edge-preserving filter for chrominance channels with the guidance from the target grayscale image. To the best of our knowledge, this is the first work on sparse pursuit image colorization from single reference images. Experimental results demonstrate that our colorization method outperforms state-ofthe-art methods, both visually and quantitatively using a user stud

The structure and soil characteristics of a Pinus tabuliformis planted forest after 60 years of natural development in North China

This study evaluated the transformation of a Carrière forest into a near-natural forest after 60 years of natural development. The structure and soil characteristics of planted forest, the near-natural forest (coniferous-broadleaved mixed forest), and secondary forest ( Fisch. ex Ledeb. forest) were compared. Tree, shrub and herb species diversity of the mixed and forests was higher than that of the planted forest. Examination of soil characteristics revealed that compared to the pure pine forest, nitrogen (N) and phosphorus (P) concentrations of the mixed and forests increased in the forest floor and soil, but total carbon (C) concentration decreased in the forest floor, countered by increases in the soil. Furthermore, soil cation exchange capacity (CEC) and pH in the forest increased when deciduous broadleaved species were present. Total microbial biomass and bacterial biomass in the soils were greatest in the forest, followed by the mixed, and then the forests. However, fungal biomass did not significantly differ among the three forests. Overall, the findings of this study suggest that different forest types can affect soil microbial biomass and community structure. Meanwhile, the natural development is recommended as a potential management alternative to near-natural transformation of a planted forest.Pinus tabuliformisP. tabuliformisP. tabuliformisQuercus mongolicaQ. mongolicaP. tabuliformisQ. mongolicaP. tabuliformisQ. mongolica P. tabuliformis P. tabuliformi

Improving Effects of Afforestation with Different Forest Types on Soil Nutrients and Bacterial Community in Barren Hills of North China

Afforestation can improve soil nutrient content and microbial community structure, increase soil carbon sequestration, and reduce greenhouse gas emissions. However, at present, there is a lack of research on the low hills and mountainous areas in North China. In order to scientifically evaluate the effect of afforestation recovery with different forest types on the improvement of the soil ecological system, the Fanggan ecological restoration in North China was taken as the research sample, and the coniferous forests, mixed coniferous and broad-leaved forest quadrats and broad-leaved forests, as well as the contrast of barren hills bushes were set to achieve the research goals. Research results of different forest types on soil nutrient and bacterial community in the Fanggan ecological restoration area have shown that afforestation with broad-leaved forests most obviously improved the nutrition properties and bacterial community of soil. (1) Broad-leaved forest afforestation obviously improved water retention and ammonia nitrogen content but reduced the content of available phosphorus and nitrate nitrogen of surface soil. It also increased available phosphorus, ammonia nitrogen, and nitrate nitrogen content of lower soil. (2) Broad-leaved forest afforestation significantly increased α-diversity of the bacterial community in surface soil, but only enhanced the Chao1 and ACE indices of lower soil. In addition, afforestation has also significantly changed the structure of soil bacterial community and β-diversity index. (3) Proteobacteria, Acidobacteria, Actinobacteria, and Verrucomicrobia accounted for the highest proportion of soil bacterial community. Proteobacteria and Verrucomicrobia occupied higher proportion in broad-leaved forests than in other forest types, while the proportion of Acidobacteria and Actinobacteria was the opposite. (4) Afforestation decreased cooperation and increased competition among bacteria of surface soil as well as increased coexistence and rejection among subsoil bacteria. (5) pH, ammonia nitrogen, organic carbon, and available phosphorus have exhibited a significant impact on the structure of bacterial community in the surface soil, while the bacterial community structure of the lower soil was mainly affected by pH and available phosphorus. Results have fully demonstrated the positive effects of broad-leaved forest on the restoration of soil nutrients and microbial community structure. Meanwhile, the important combinations of soil physical and chemical factors affecting soil bacterial community structure were also explored. The results can provide scientific basis for revealing the mechanism of soil organic matter, nutrient and ecological function restoration by artificial afforestation, and also offer theoretical support and practical reference for the restoration of artificial afforestation in the hilly and mountainous areas of North China

Responses of Rhizosphere Soil Chemical Properties and Bacterial Community Structure to Major Afforestation Tree Species in Xiong’an New Area

To explore the response of rhizosphere chemical and biological properties to eight major afforestation species in Xiong’an New Area, we measured rhizosphere soil properties in their pure stands and analyzed the bacterial community structure using a high-throughput sequencing platform. The results showed that: (1) Compared with coniferous species, broadleaved species had higher total nutrient concentration and pH in the rhizosphere but lower available nutrient concentration and soil moisture. Nitrate nitrogen deficiency was found in all stands. (2) Uncultured_bacterium_f_Longimicrobiaceae and RB41 could distinguish Platycladus orientalis (Linn.) Franco from other trees. Compared with other tree species, Sabina chinensis (Linn.) Ant., Armeniaca vulgaris Lam., and Fraxinus chinensis Roxb. gathered more Actinobacteria, Planctomycetes, and Gemmatimonadetes, respectively. Uncultured_bacterium_o_Rokubacteriales, uncultured_bacterium_f_Gemmatimonadaceae, and uncultured_bacterium_c_Subgroup_6 were major contributors to the differences in bacterial communities among most tree species. (3) Species characteristics changed soil chemical properties, further affecting the bacterial community. Total carbon, organic matter, total nitrogen, and pH were the main factors explaining these variations. In general, Sophora japonica Linn. and F. chinensis could increase soil total nutrient significantly, which meant that they were more suitable for afforestation in the studied area than the other species. P. orientalis and Pinus tabuliformis Carr. were better choices among conifers. We suggest planting more mixed forests to improve the rhizosphere nutrient status of conifers. A suitable way to alleviate prevailing nitrogen and phosphorus limitations is also required, such as introducing understory vegetation or supplementing organic fertilizers

Improving Effects of Afforestation with Different Forest Types on Soil Nutrients and Bacterial Community in Barren Hills of North China

Afforestation can improve soil nutrient content and microbial community structure, increase soil carbon sequestration, and reduce greenhouse gas emissions. However, at present, there is a lack of research on the low hills and mountainous areas in North China. In order to scientifically evaluate the effect of afforestation recovery with different forest types on the improvement of the soil ecological system, the Fanggan ecological restoration in North China was taken as the research sample, and the coniferous forests, mixed coniferous and broad-leaved forest quadrats and broad-leaved forests, as well as the contrast of barren hills bushes were set to achieve the research goals. Research results of different forest types on soil nutrient and bacterial community in the Fanggan ecological restoration area have shown that afforestation with broad-leaved forests most obviously improved the nutrition properties and bacterial community of soil. (1) Broad-leaved forest afforestation obviously improved water retention and ammonia nitrogen content but reduced the content of available phosphorus and nitrate nitrogen of surface soil. It also increased available phosphorus, ammonia nitrogen, and nitrate nitrogen content of lower soil. (2) Broad-leaved forest afforestation significantly increased α-diversity of the bacterial community in surface soil, but only enhanced the Chao1 and ACE indices of lower soil. In addition, afforestation has also significantly changed the structure of soil bacterial community and β-diversity index. (3) Proteobacteria, Acidobacteria, Actinobacteria, and Verrucomicrobia accounted for the highest proportion of soil bacterial community. Proteobacteria and Verrucomicrobia occupied higher proportion in broad-leaved forests than in other forest types, while the proportion of Acidobacteria and Actinobacteria was the opposite. (4) Afforestation decreased cooperation and increased competition among bacteria of surface soil as well as increased coexistence and rejection among subsoil bacteria. (5) pH, ammonia nitrogen, organic carbon, and available phosphorus have exhibited a significant impact on the structure of bacterial community in the surface soil, while the bacterial community structure of the lower soil was mainly affected by pH and available phosphorus. Results have fully demonstrated the positive effects of broad-leaved forest on the restoration of soil nutrients and microbial community structure. Meanwhile, the important combinations of soil physical and chemical factors affecting soil bacterial community structure were also explored. The results can provide scientific basis for revealing the mechanism of soil organic matter, nutrient and ecological function restoration by artificial afforestation, and also offer theoretical support and practical reference for the restoration of artificial afforestation in the hilly and mountainous areas of North China

Ultra-dense carbon defects as highly active sites for oxygen reduction catalysis

Defective carbons have recently been considered as one of the most promising alternatives to precious metal electrocatalysts. However, atomic structural tailoring of carbon defects poses challenges, especially in regulating defect density to maximize the active sites. Herein, we report an interfacial self-corrosion strategy to control the removal and reconstruction of carbon atoms via a series of thermal redox reactions of ZnO quantum dots and formed CO2 gas in confined carbon cavity. The ultra-dense carbon defects (HDPC) (2.46 × 1013 cm−2) in the derived porous carbon served as efficient active sites for oxygen reduction, resulting in an excellent catalyst in both base and acid (half-wave potentials of 0.90 or 0.75 V in 0.1 M KOH or HClO4). The normalized specific activity and density functional theory calculation reveal a gradient “proximity effect” between carbon defects with different spatial distance, indicating that the quantitative control of carbon defect density is the key to enhancing electrocatalytic activity.</p

Changes in Soil Bacterial Community Structure and Diversity of <i>Pinus Tabuliformis</i> Plantation after 65 Years of near-naturalization in North China

Our study investigates the effect of near-naturalization of plantations on soil physicochemical and bacterial features and the difference between soil layers in Baxianshan National Nature Reserve. Four stands were involved, including two forest types: near-naturalized and natural secondary forests, with the former classified into three stages. Soil physicochemical and bacterial properties were determined and analyzed. TC, TN contents and C/N ratio of the surface soil were higher than the corresponding lower layer. TC, TN contents decreased first and then increased with near-naturalization, lower than the natural secondary forests, while the C/N ratio was the opposite; total and endemic OTUs quantity was more in the surface layer than the lower and both increased with near-naturalization; the dominant phyla were Proteobacteria, Acidobacteria, Gemmatimonadetes, and verrucomicrobia, the relative abundance of Proteobacteria increased with near-naturalization while that of other dominant phyla decreased; the α-diversity increased on the whole during near-naturalization and was lower than the natural secondary forests except for Simpson and Shannon index; environmental factors significantly explained the bacterial α-diversity and community structure of natural secondary forests but not near-naturalized forests. This study helps fully understand the change characteristics and response mechanisms of soil bacterial community structure to the restoration of the plantation.</p