Analysis of morphological characteristics of gravels based on digital image processing technology and self-organizing map

A comprehensive understanding of spatial distribution and clustering patterns of gravels is of great significance for ecological restoration and monitoring.However,traditional methods for studying gravels are low-efficiency and have many errors.This study researched the spatial distribution and cluster characteristics of gravels based on digital image processing technology combined with a self-organizing map(SOM)and multivariate statistical methods in the grassland of northern Tibetan Plateau.Moreover,the correlation of morphological parameters of gravels between different cluster groups and the environmental factors affecting gravel distribution were analyzed.The results showed that the morphological characteristics of gravels in northern region(cluster C)and southern region(cluster B)of the Tibetan Plateau were similar,with a low gravel coverage,small gravel diameter,and elongated shape.These regions were mainly distributed in high mountainous areas with large topographic relief.The central region(cluster A)has high coverage of gravels with a larger diameter,mainly distributed in high-altitude plains with smaller undulation.Principal component analysis(PCA)results showed that the gravel distribution of cluster A may be mainly affected by vegetation,while those in clusters B and C could be mainly affected by topography,climate,and soil.The study confirmed that the combination of digital image processing technology and SOM could effectively analyzed the spatial distribution characteristics of gravels,providing a new mode for gravel research.

Migmatite-like textures in anthracite:Further evidence for low-grade metamorphic melting and resolidification in high-rank coals

Previous studies demonstrated that melting,initiated by supercritical fluids in the 375-400℃range,occurred as part of anthracite metamorphism in the Appalachian Basin.Based on the known behavior of vitrinite at high temperatures and,to a lesser extent,at high pressures,it was determined that the duration of the heating,melting,and resolidification event was about 1 h.In the current study,featureless vitrinite within banded maceral assemblages demonstratesthe intimate association of melted and resolidified vitrinite with anthracite-rank macerals.By analogy with metamorphosed inorganic rocks,such associations represent diadysites and embrechites,i.e.,cross-cutting and layered migmatites,respectively.Even though the temperature of formation of the anthracite structures is several hundred℃lower than that seen in metamorphosed inorganic rocks,anthracites are metamorphic rocks and the nomenclature for metamorphic rocks may be appropriate for coal.

Microbial community structure across grazing treatments and environmental gradients in the Serengeti

As one of the last remaining naturally grazed ecosystems on Earth,the Serengeti National Park is an ideal location to study the influence of migratory mammals on the structure of microbial communities and the factors that generate biogeography of soil microbes.Furthermore,volcanic inputs generate environmental gradients that may also structure microbial communities.We studied 16S rRNA amplicons in a 13-year herbivore removal experiment to examine the influence of grazing and environmental gradients on the natural distribution of soil microbes.Removal of mammalian herbivores shifted microbial community structure,with 31 taxa that were significant indicator taxa of the ungrazed treatment and three taxa that were indicators of the grazed treatment.The abundance of many taxa were correlated with soil texture,phosphorus,iron,calcium and rainfall,and the evenness of taxa within samples was also correlated with these variables.Bayesian general linear mixed effects models with single predictors of multiple,highly correlated variables of beta diversity were consistent with a significant,but weak(2%),effect of grazing,and stronger effects of phosphorus(14%).Beta diversity of microbial communities was greater in grazed than in ungrazed plots;suggesting that the impacts of grazing on community assembly of microbes results from deterministic environmental filtering caused by the influence of herbivores on plant communities and soil properties rather than stochastic dispersal via herds of large mammals.These herbivore effects are superimposed on deterministic environmental filtering by natural soil and precipitation gradients across the Serengeti.