Danxia Landform Research Articles

Correlation of spatial distribution and habitat factors of Firmiana danxiaensis based on GeoDetector

Firmiana danxiaensis is an endemic species of Danxia landform in China. Identifying the main driving factors of its distribution can provide scientific basis for the conservation of F. danxiaensis and related habitats. With GeoDetector, we analyzed the correlation (measured by q value) between the spatial distribution of F. danxiaens and its habitat factors in F. danxiaens Nature Reserve in Nanxiong City and the Guangdong Danxia Mountain Tourism Scenic Area (core scenic area). Factors measured in this study included geographical elements (geomorphological type, soil subtype, elevation, slope, aspect) and climatic elements (annual precipitation and annual sunshine hours, mean annual relative humidity and mean annual wind speed). Our results showed that the main habitat factors affecting the spatial distribution of F. danxiaensis were soil subtype, annual sunshine hours, and geomorphologic genesis type. The q values of those three factors were higher than the mean values of all factors. In the pairwise combination of habitat factors, the interaction between geomorphologic genesis types ∩ annual sunshine hours and soil subtypes ∩ annual sunshine hours was enhanced by two factors and the q value was greater than the mean value of all combinations, with a strong correlation. Compared with other factors, the q value of soil subtypes, annual sunshine hours and geomorphologic genesis types were significantly different in the ecological detection of spatial distribution correlation of F. danxiaensis. The spatial distribution of F. danxiaensis was significantly correlated with soil subtypes, geomorphologic genesis types and annual sunshine hours, indicating that the GeoDetector is a useful method for vegetation habitat factor analysis and species distribution prediction.

Front Cover: Fabrication and Functioning of Magnetically Gated PET Nanochannels (ChemNanoMat 7/2020)

A magnetically controlled conical nanochannel is fabricated by grafting ferroferric oxide nanoparticles into the polyethylene terephthalate (PET) nanochannel via bridging of DNA single strands. The nanochannel can be physically closed/opened to control the ionic/molecular transport in the nanochannel within sub-seconds using a permanent magnet. This mechanism may shine light on pigeon homing under the Earth's magnetic field, and could be widely used in noncontact control of micro/nanofluidic devices, as well as in smart drug delivery (superficial paste) controlled by external magnets. The background shows the colorful Danxia landform of rich iron ore in Zhangye, China. More information can be found in the Full Paper by Guanghua Du et al.

诸暨市丹霞地貌研究

诸暨市丹霞地貌研究

Parnassia zhengyuana sp. nov. and P. simianshanensis sp. nov.: two new species of Parnassia (Celastraceae) from karst caves and Danxia landform in southwest China

Two new species of Parnassia, Parnassia zhengyuana M.X. Ren & J. Zhang and P. simianshanensis M.X. Ren, J. Zhang & Z.Y. Liu, have been found in mountainous areas of Chongqing City, southwest China, and are described and illustrated here. Parnassia zhengyuana is found in a limestone cave near Mt Jinfo, Nanchuan District, Chongqing City. This tiny plant has special spoon‐shaped leaves and undivided staminodes with green apices. Parnassia simianshanensis was discovered in Mt Simian, Jiangjin County, Chongqing City. This species grows along streams on red sandstones, i.e. in Danxia landform. It can be easily identified by its unique rhombic leaves and the five‐ or four‐branched staminodes. The conservation status of P. zhengyuana and P. simianshanensis are assessed respectively as ‘Critically Endangered’ (CR) and ‘VU’ (Vulnerable) according to IUCN criteria. The roles of karst and Danxia landforms in the speciation process are discussed.

Retraction: Impacts of rock properties on Danxia landform formation based on lithological experiments at Kongtongshan National Geopark, northwest China.

As an erosional landform, the formation processes of Danxia landform are controlled by internal and external forces as well as lithologic properties. Using field data, we studied the role of lithologic properties on the formation of Danxia landform in Kongtongshan National Geopark, northwest China, through a series of experiments, including uniaxial compressive strength, identification analysis under polarizing microscope, X-ray diffraction analysis, inductively coupled plasma-mass spectrometry analysis, and scanning electron microscopy. The results show that the diagenesis degree, mineral composition, cement composition, degree of cementation, geochemical composition and element contents, and micro-structure influenced the structure and anti-weathering and anti-erosion abilities of the Danxia rock mass. Differential weathering of rock in different environments was an important force shaping the different types of Danxia landform. Weathering failure of the Danxia rock mass was the result of multiple combined factors; as well as lithology, other factors, such as those induced during tectonic uplift (i.e., faulting, jointing, and fracturing) and climate, cannot be neglected. Therefore, lithology played an important role in the structural development of Danxia landform, and different lithologies influenced its weathering rate and formation processes. Our findings can provide a reference for revealing the microscopic development of Danxia landform in arid and semi-arid areas.

The complete chloroplast genome of Firmiana danxiaensis, an endangered species endemic to Danxia landform in Southern China

We sequenced the complete chloroplast of Firmiana danxiaensis (Malvaceae), which is 161,253 bp in size and consists of a large single-copy region (LSC) of 90,142 bp and a short single copy region (SSC) of 20,067 bp. It was separated by two inverted repeats (IRs) regions of 25,522 bp for each. The GC content of the whole genome, LSC, SSC, and IRs region was 36.87%, 34.68%, 31.24%, and 42.97%, respectively. The overall base content was A (31.07%), T (32.05%), C (18.80%), and G (18.08%). The genome contained 127 genes, including 82 protein-coding sequences, 37 tRNA genes, and 8 rRNA genes. Phylogenetic analysis showed that F. danxiaensis is sister to F. simplex, and supported there was a close relationship among F. danxiaensis, F. simplex, and F. pulcherrima.

A new tuberous species of Begonia sect. Diploclinium endemic to Danxia landforms in central China

Begonia danxiaensis, a new tuberous species of Begonia, is described and illustrated, and supported by morphological and molecular evidences. It belongs to Begonia sect. Diploclinium and is endemic to the Danxia landforms of both Jiangxi and Hunan provinces, China. The morphological similarity between the new species and its similar taxa were compared and discussed. The new species is assigned to Vulnerable (VU) according to the IUCN Red List Categories and Criteria.

The Spatial Patterns of Red Beds and Danxia Landforms: Implication for the formation factors\u2013China

This research examined the distribution features of red beds and 1,100 Danxia landform sites across China, while probing the relationship between these spatial patterns and geological elements. This study is based on geological and tectonic maps of China. ArcGIS software was used to process the adjacent index, then perform a spatial analysis of Danxia landforms and red beds, and a coupling analysis of Danxia landforms and red beds with tectonics. Based on a point pattern analysis of Danxia landforms, the adjacent index is 0.31, and the coefficient of variation verified by Thiessen polygon reaches 449%. These figures reflect the clustered distribution pattern of the Danxia landforms. Across the country, Danxia landforms are concentrated into three areas, namely, the Southeast China region, the Sichuan Basin region and the Qilian-Liupan region. The exposure of red beds covers 9.16 × 105 km2, which accounts for 9.5% of the total land area of China. With this research background, the geological elements of tectonics and their effects on the distribution, number, and spatial pattern of Danxia landforms and red beds were analyzed.

Determining the number and distribution of Firmiana Danxiaensis, a rare and endangered plant species in Danxiashan, South China, using DEM data and UAV technology

Firmiana danxiaensis, a rare and endangered plant species in Danxiashan, South China, belongs to Sterculiaceae family. The central Danxiashan covering an area of 10.6 km2 was selected as a case study. The location data of F. danxiaensis was collected by field work, and the environmental variables (slope, aspect, and elevation) were generated from DEM data of 1m resolution, while their images were collected by unmanned aerial vehicle (UAV) in revealing the relationships between the micro-landforms and their spatial distribution. Three spatial analysis modules of ArcGIS10.0, including the Raster Surface-Contour List, slope, and aspect functions were used to extract from the DEM data of 1m resolution which were superimposed on the remotely-sensed photo data and transferred onto maps for the purpose of visualizations. The visualized maps indicated that there were no more than 1000 F.danxiaensis in the case study area. They are mainly distributed along sheer Danxia cliffs, with slopes above 30º and elevation ranges from100-300m. Also these cliffs have with vertical joints or horizontal bedding, and some drought tolerant plants, such as Osteomeles subrotunda, Lycoris aurea, and Selaginella tamariscina were usually found nearby. The main conclusions are as follows: 1The special Danxia landforms provided the key survival space for F. danxiaensis which is a kind of drought tolerant plant, growing mainly along Danxia cliffs with joints or beddings of thin barren soils. 2 According to the rules discussed above, F. danxiaensis is presumably distributed outside of the case area with the similar sheer cliff micro-landform environments in Danxia landforms. 3 Our research here may provide a proof of concept that UAVs may provide a low cost and accurate method in fast conducting surveys of data.

Impacts of rock properties on Danxia landform formation based on lithological experiments at Kongtongshan National Geopark, northwest China.

As an erosional landform, the formation processes of Danxia landform are controlled by internal and external forces as well as lithologic properties. Using field data, we studied the role of lithologic properties on the formation of Danxia landform in Kongtongshan National Geopark, northwest China, through a series of experiments, including uniaxial compressive strength, identification analysis under polarizing microscope, X-ray diffraction analysis, inductively coupled plasma-mass spectrometry analysis, and scanning electron microscopy. The results show that the diagenesis degree, mineral composition, cement composition, degree of cementation, geochemical composition and element contents, and micro-structure influenced the structure and anti-weathering and anti-erosion abilities of the Danxia rock mass. Differential weathering of rock in different environments was an important force shaping the different types of Danxia landform. Weathering failure of the Danxia rock mass was the result of multiple combined factors; as well as lithology, other factors, such as those induced during tectonic uplift (i.e., faulting, jointing, and fracturing) and climate, cannot be neglected. Therefore, lithology played an important role in the structural development of Danxia landform, and different lithologies influenced its weathering rate and formation processes. Our findings can provide a reference for revealing the microscopic development of Danxia landform in arid and semi-arid areas.

The Fine Characterization and Potential Photocatalytic Effect of Semiconducting Metal Minerals in Danxia Landforms

The Danxia landform is representative of the Cretaceous continental red sediment. The careful identification and potential environmental effects of minerals in Danxia red beds have yet to be clearly reported. In this work, reddish sandstone samples were collected from Lang Mountain Danxia landform in Xinning, Hunan province, China, and their mineral phases, element distribution, microstructure, and the spatial relationship of different minerals were investigated using polarizing optical microscope, environmental scanning electron microscopy, energy-dispersive X-ray analysis, electron probe microanalysis, micro-Raman spectra, micro- X-ray diffraction, X-ray fluorescence spectroscopy, and high-resolution transmission electron microscopy. The results revealed that iron oxide (mainly hematite) and titanium oxide (mainly anatase) were the dominant minerals in Danxia red layers. Microcrystalline hematite was suggested as being the coloring mineral. Anatase, reported here for the first time in Danxia red beds, constituted the content of titanium in the red layer (0.17–0.57%) and was present in a significantly higher amount than the adjacent limestone formation (0.13%). Over 95% of Fe/Ti oxides served as a cementation agent along the framework of coarse-grain minerals (quartz and feldspar). The hematite and anatase were visible-light-responsive semiconductors, with a band gap of 2.01 eV and 3.05 eV, respectively. Photoelectrochemical experiments were performed on synthetic hematite, anatase, and their coupled material. The inactive hematite displayed an enhanced 23-fold photocurrent at 0.8 V (vs. Ag/AgCl) when coupled with anatase. Furthermore, in a photodegradation experiment using methyl orange dye under simulated sunlight, the coupled material showed decolorizing efficiency 2.4 times that of hematite. The anatase, therefore, prominently improved the photocatalytic activities of hematite. It is proposed that these semiconducting minerals in red beds produce oxygen reactive species and have significant environmental effects, which is of great importance.

A Brief Analysis of Cave Types of Danxia Landform in Xinjiang Basin

The Xinjiang basin’s tectonic site properly on the suture where the two plates of Yangtze and Cathaysia collided. It had suffered an evolution history from rift basin to fault basin affected by Movement of Pacific Block since Mesozoic and had deposited a set of huge thick bedded terrestrial facies fragmentary system. There developed amount of Danxia Landforms in the basin with the effects of exogenic geological process. Cavernous weathering is the common phenomenon in Danxia Landform areas. The evolution of Danxia cave is controlled by lithologic characters, cleavages and fissures. The siltstone and sandstone and pebbled sandstone interlayers of Upper Cretaceous Chongan Formation are the principal stratigraphic position of forming the caves. It is considered that the devolvement of the caves in the surveyed area frequently results from the synthetic action of multifold external powers, just as the weathering denudation, water currents, and gravitational force.

Petrocodon asterocalyx, a new species of Gesneriaceae from Guangxi, China

Petrocodon asterocalyx F.Wen, Y.G.Wei & R.L.Zhang, a new species from the Danxia landform area in Guangxi, South China, is described and illustrated based on molecular and morphological data. The molecular evidence shows that the new species is recovered in a weakly supported clade. Within this clade, the new one is morphologically similar to P. hancei (Hemsl.) A.Weber & Mich.Möller and P. coriaceifolius (Y.G.Wei) Y.G.Wei & Mich.Möller, and it can be distinguished from the former by calyx lobes 20–40 × 2–3 mm, corolla 2.5–3.0 cm long, filaments sparsely erectly pubescent, anthers sparsely pubescent, staminodes 3, and stigmas 2; from latter by leaf blades rhombic-oblong or rhombic, base shallowly cuneate, margin crenulate to serrate, calyx lobes linear, 20–40 × 2–3 cm, and anthers 3.5–3.8 mm long, sparsely pubescent and elliptical.

Research on the Genesis and Development of Danxia Landform in the South Sichuan

The South Sichuan is one of the areas in China famous for Danxia Landform. Danxia Landform in the South Sichuan is characterized by wide distribution and square shaped hills. However, there is no systematic research on the genesis of those Danxia Landforms at present. Based on the study of spatial distribution and the genesis of the Danxia Landforms in the South Sichuan, we discovered that the lithostratigraphy, regional tectonic, crustal uplift and external forces contribute together to the formation of the Danxia Landform. On the basis of learning the development experiences from famous scenic spots and the updated national policies and regulations, proposals were made to boost the development of Danxia Landform resources in the South Sichuan by excavating its historic, cultural, natural and scientific connotation in the form of educational tourism.

Geo-environmental characteristics of weathering deterioration of red sandstone relics: a case study in Tongtianyan Grottoes, Southern China

It is reasonable to study the destruction and preservation of stone relics from a geo-environmental point of view. The Tongtianyan Grottoes, known as “the First Grottoes in Southern China”, are located in the city of Ganzhou, Jiangxi province, China, and are the largest cave temples in eastern China and southern China. The grottoes were carved into sandstone palisades during the period from the late Tang Dynasty (755–763 AD) to the Republic of China (1912–1949 AD). In China, the Danxia landform is a special landform characterized by red sandstone cliffs. Different from the grottoes located in arid climate regions, the Tongtianyan Grottoes have the lowest latitude (25°45′N) among all the grottoes in China, and the stone relics are under a perennially warm and humid environment. The monuments have suffered from various forms of weathering deterioration, which can be summarized as five types: exfoliation, bio-weathering deterioration, crack, erosion, and loss. Detailed investigations have been conducted to analyze the mechanisms of the weathering deterioration of the stone relics based on different aspects of geo-environmental characteristics. The weathering sandstone samples were analyzed using X-ray diffraction and X-ray fluorescence, and the chemical weathering indices (LOI, WPI, and WI) were calculated. We found that there is a boundary zone at a depth of 10 ± 2.5 mm from the surface to the inner rock based on the curves of the chemical weathering indices, and the rock outside of the boundary zone has much stronger weathering than that inside.

Upper Cretaceous alluvial fan deposits in the Jianglangshan Geopark of Southeast China: implications for bedrock control on Danxia landform evolution

The Jianglangshan Geopark in the western Zhejiang Province of Southeast China is well-known for its spectacular red-colored sandstone landforms. Little is known about the depositional processes of the conglomerate-dominated Fangyan Formation, the lithologic base of the Danxia landforms in this geopark. Based on detailed field investigation of lithology, sedimentary structures, bed thickness and geometry, five facies are recognized: facies A (matrix-supported cobble conglomerate), facies B (pebble conglomerate), facies C (pebbly sandstone), facies D (fine-grained sandstone) and facies E (mudstone). The results show that streamflow-dominated fans were the main depositional processes responsible for the accumulation of the Fangyan Formation along the mountain fronts. These fan conglomerates form the base for the evolution of the Danxia landscapes owing to the uplift and erosion of the study area. In contrast, the fine-grained sedimentary successions produced by fluvial floodplains in the distal part of the fans were thinner and more easily weathered. Such sedimentary facies distribution patterns were thought to be similar during Late Cretaceous across Southeast China. The Danxia landforms are largely the geographical expressions of the conglomerate-dominated redbeds in the proximal-middle fans.

Stone pillar rockfall in Danxia landform area, Mt. Langshan, Hunan Province, China

A typical Danxia stone pillar, Leipishi I, in the World Natural Heritage site at Mt. Langshan, China, collapsed on 2 November 2009. To understand the mechanism controlling this rockfall event, uniaxial compressive strength, tensile strength, resistance against sulfuric acid, and freezing and thawing properties were analyzed from 44 sandstone and conglomerate cores collected from the Lanlong Formation, the only exposed formation on Mt. Langshan. In addition, four rock slices were created for analysis under a polarizing microscope. A detailed reconstruction of the geometry and restraint conditions of the stone pillar in place before the rockfall occurred permitted an estimation of the stress state before collapse using 3D finite-element code. The results show that the rapid retreat of soft, intercalated rock layers due to weathering can profoundly change the stress state within the rock body, causing compressive or tensile stresses to rise above compressive or tensile strengths in specific sections of a rock body, and causing partial or complete collapse.

De Novo Transcriptome Assembly in Firmiana danxiaensis, a Tree Species Endemic to the Danxia Landform

Many Firmiana species are locally endemic, providing an interesting system for studying adaptation and speciation. Among these species, F. danxiaensis is a tree species endemic to Mount Danxia in Guangdong, China, which is an area known for presenting the Danxia landform. How F. danxiaensis could have adapted to the stressful environment of rocky cliffs covered with barren soils in the Danxia landform is still unknown. In this study, we performed de novo assembly of the transcriptome of F. danxiaensis, obtaining 47,221 unigenes with an N50 value of 987 bp. Homology analysis showed that 32,318 of the unigenes presented hits in the NCBI non-redundant database, and 31,857 exhibited significant matches with the protein database of Theobroma cacao. Gene Ontology (GO) annotation showed that hundreds of unigenes participated in responses to various stresses or nutritional starvation, which may help us to understand the adaptation of F. danxiaensis to Danxia landform. Additionally, we found 263 genes related to responses to Cd, partially explaining the high accumulation of Cd observed in Firmiana species. The EuKaryotic Orthologous Groups (KOG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations revealed many genes playing roles in the biosynthesis of secondary metabolites and environmental adaptation, which may also contribute to the survivor and success of Firmiana species in extreme environments. Based on the obtained transcriptome, we further identified a Firmiana-specific whole-genome duplication event that occurred approximately 20 Mya, which may have provided raw materials for the diversification of Firmiana species.

Dryopteris shiakeana (Dryopteridaceae): A new fern from Danxiashan in Guangdong, China

Dryopteris shiakeana, a new species of Dryopteridaceae from Danxia landform in Danxiashan National Park, Guangdong, China, is described and illustrated. This species exhibits morphological characteristics similar to D. dehuaensis but differs in terms of dense scales on the rachis of laminae and pinnae, dissected pinnules, more prominent veinlets, reddish-brown scales on stipes, and toothed margin. Based on results of molecular phylogenetic analysis of the trnL-F sequence, our conclusion is that D. shiakeana is most closely related to D. dehuaensis.

Numerical simulation of the evolutionary process of Danxia landforms

Danxia landforms are defined as a landscape type that developed in red terrestrial clastic rocks generally with near-horizontal strata. Lithology, vertical joint sets, tectonic history, and rainfall play important roles in shaping Danxia landforms, leading to increased difficulty and complexity in quantitatively understanding their evolution. Integrating the factors mentioned above, this study represents the first attempt to investigate the evolutionary process of Danxia landforms using a numerical simulation. Parameters used in this study were employed from earlier studies on Danxia Mountain in southeastern China. The results quantitatively present a complete dynamic course shaping Danxia landforms that could not be seen from field observation alone. The process arises from interactions between tectonics and fluvial erosion and displays typical characteristics of Danxia landforms in different evolutionary stages. The results also show that the features of fractures and joints have significant constraints on the evolutionary process. Through comparative analysis of the earlier conceptual results and our simulation, we conclude that the model used in this study can reasonably represent the typical, physical formation process of Danxia landforms. Although the model is robust and thus might not be precise, our results still reveal the interesting dynamic behavior shaping Danxia landforms.