Longmen Mountain Research Articles

Size distribution law of earthquake-triggered landslides in different seismic intensity zones

Abstract. The Ms 8.0 Wenchuan earthquake in 2008 and Ms 7.0 Lushan earthquake in 2013 produced thousands of landslides in the southern region of the Longmen Mountains in China. We conducted field investigations and analyzed remote sensing data to determine the distribution law of earthquake-triggered landslides. The results show a strong negative power law relationship between the size and frequency of landslides in VII, VIII, and IX seismic intensity zones, a weak power law in the X seismic intensity zone, and a lognormal distribution in the XI seismic intensity zone. Landslide density increases with increasing seismic intensity. A sandpile cellular automata model was built under the conceptual framework of self-organized criticality theory to simulate earthquake-induced landslides. Data from the simulations demonstrate that, with increasing disturbance intensity, the dynamical mechanism of the sandpile model changes from a strong power law to a weak power law and then to a lognormal distribution. Results from shaking table experiments of a one-sided slope sandpile show that, for peak ground acceleration (PGA) in the range of 0.075–0.125 g, the relation between the amount and frequency of sand follows a negative power law. For PGA between 0.15 and 0.25 g, the relation obeys a lognormal distribution. This verifies that the abovementioned distribution of earthquake-induced landslides should be a universal law from a physical viewpoint and may apply to other areas. This new perspective may be used to guide the development of an inventory of earthquake-triggered landslides and provide a scientific basis for their prediction.

Trace and rare-earth element characteristics of fine-grained sediments in the Upper Triassic Xujiahe Formation in the western Sichuan Basin, SW China: implications for the provenance and depositional environment

Xujiahe fine-grained sediments (FGSs) are regarded not only as important shale gas targets but also as significant regional hydrocarbon source rocks. To analyze the provenance and depositional conditions of the Xujiahe FGSs, trace elements and rare-earth elements (REEs) from two wells in the western Sichuan Basin were investigated. The results indicate that the Xujiahe FGSs mainly originated from the upper continental crust (UCC), the source rocks gradually changed from mixed influence to relatively pure sedimentary rocks from the second member of Xujiahe Formation (Xu2 member) to the fourth member of Xujiahe Formation (Xu4 member), which was related to the uplift of Longmen Mountain. La–Th–Sc and Th–Co–Zr/10 diagrams indicate an active continental margin environment. The redox condition indices (V/Cr and Th/U) suggest that the Xujiahe FGSs were deposited in an oxic environment, while the paleoclimate indices suggest differences among the members. The Xu3 member shows a stable warm-humid climate, and the Xu2 and Xu4 members alternate between humid and arid climates. The combination of climate and tectonics is the key factor in the formation of the Xujiahe FGSs. The warm and humid climate result in high productivity in the basin, tectonic movement influence the substance supply and create a high sedimentary rate for the Xujiahe Formation; thus, the organic matter in the Xujiahe FGSs can still be effectively preserved even under oxidation conditions.

Household recovery strategies in Longmen Mountain area, Sichuan, China, following the 2008 Wenchuan earthquake disaster

After the Wenchuan earthquake, the overall post-reconstruction of the affected area was completed in 2 years with significant achievements in a top-down fashion. However, the secondary large-scale mass movements and floods that followed the earthquake have shattered mountain settlements and resulted in serious loss of life and property over the last ten years. Local people have taken their own initiative for house reconstruction and recovery. Having taken the tremendous government-driven reconstruction into consideration, the current study aims to understand the contribution of bottom-up approach in whole reconstruction process in Jianjiang River, Longmen Mountain Town of Sichuan, China. This study reveals that in the process of individual rebuilding, local households have tried to construct houses by using more contemporary structures and local resources to rebuild smaller buildings. Such reconstruction activities have changed their lifestyle and source of income to cope with future disasters and adapt with the post-disaster recovery process. Rural households shifted their income sources from tourism to labour migration while revitalizing farming for food and additional income. More than half of residents have no worry about the risk of disasters in reconstruction areas. The bottom-up adaptation can be more sustainable in Longmen Mountain area and provide a reference for other rural areas under recovery after disasters.

A study on the forecast calculating method of the density of rainfall debris flow in Southwestern of China

Density is the most important parameter of debris flow. This work looks into the typical debris flow and mountain torrent occurred in Longmen Mountains in the past 20 years and compares the calculation results of the density using various methods. It shows that the mean deviations of result are in the range of 20–30%, and the static model is only suitable to the occurred debris flow event but not the forecast. Based on the analysis of typical rainfall debris flow, the influence factors of density are revealed; it shows that the density is controlled by the form conditions and the soil-water coupling process of debris flow. A function is introduced to describe the activity of material source, which defined by volume and relative elevation of materials, and the watershed area. The forecast model is established by the relationship between the density and its influence factors. When the new method is applied to the Longmen mountain area and the upper basin of the Minjiang River, although there are still few discretization errors, the results still can explain nearly 95% of the evolution trend, which shows that the new method is not compromised by regional differences.

Fossil dipterid fern Thaumatopteris in China: new insights of systematics, diversity and tempo-spatial distribution patterns

ABSTRACT Thaumatopteris (Goeppert) Nathorst is a typical dipterid fern in the early Mesozoic, showing global significances for palaeoclimate, phytogeography and biostratigraphy. However, the detailed understanding on the relationship between species diversity and the environmental background of this genus is still unclear. Here, we reinvestigated new collections and type specimens of Thaumatopteris contracta Li et Tsao collected from the Upper Triassic of Yunnan Province, and analysed the systematic, diversity variations and tempo-spatial distribution patterns of Thaumatopteris in China. An emendation was proposed for species diagnosis of Thaumatopteris contracta based on both sterile and fertile pinnae. Our analysis demonstrates that the genus Thaumatopteris reached a higher diversity and differentiation with 11 species during the Late Triassic in China and suffered a severe loss of species diversity across the Triassic-Jurassic transition. Changes in the spatial distribution pattern of Thaumatopteris demonstrate an ecological response to local environment degradation in the Upper Yangtze region. The destruction of habitat and the block of the transport channel of warm moist flow from the Tethys Ocean caused by the Indosinian tectonic movement, especially, the uplift of the Longmen Mountains may represent the potential environmental trigger.

The potential occurrence modes of hydrocarbons in asphaltene matrix and its geochemical implications

As the most polar component of crude oils, asphaltenes are characterized by their complex molecular structures and their sequestration of small organic molecules. These organic compounds are often protected from various secondary alteration processes, and thus might serve as useful molecular markers. However, little is presently known about the mode of occurrence of hydrocarbons isolated from asphaltenes by conventional approaches. In the current study, we collected veined bitumen samples from the Changjianggou Formation of the Longmen Mountains on the northwestern rim of the Sichuan Basin, extracted soluble organic matter with dichloromethane, precipitated asphaltenes with petroleum ether, and isolated hydrocarbons from the asphaltenes by centrifugation and hydrous pyrolysis. The results indicated that the n-alkane profiles of saturated hydrocarbons obtained by centrifugation and by hydrous pyrolysis at 300 °C not only were similar to each other, but also resembled those of typical crude oils more closely than the n-alkane profiles of the saturates fraction in veined bitumen extracts did. The asphaltene-bound aromatic hydrocarbons and resins were found to be too difficult to extract thoroughly by the current separation methods. A possible explanation is that saturated hydrocarbons are mostly associated with the peripheral substituents of asphaltenes via hydrophobic association, whereas aromatics and resins tend to interact with the asphaltene cores through π-π stacking, which is much stronger. Therefore, the dissociation or diffusion of the loosely bound saturated hydrocarbons would alter the geochemical information that they had originally recorded, whereas the covalently bonded or more tightly associated hydrocarbons are better shielded from secondary alteration processes.

Responses of sedimentary δ2Halk values to environmental changes as revealed by different plant responses to altitude and altitude-related temperatures

Single species-based altitudinal transects may provide a new understanding of the variabilities in sedimentary wax-derived n-alkane hydrogen isotope (δ2Halk) values caused by altitude and complex climatic change linked with the growth of mountains. We investigated Kobresia pygmaea (Kobresia), Quercus aquifolioides (Quercus) and Berberis thunbergii DC (Berberis) along three altitudinal transects on the Tibetan Plateau (TP), i.e., the southern TP, the Longmen Mountains (LM; eastern TP) and the Qilian Mountains (QL; northeastern TP). Here we present 47 plant δ2Halk values: these include 14 Kobresia, 27 Berberis and 6 Quercus samples, which are accompanied by comparisons with nine new soil δ2Halk values from the QL, and 105 previously-published δ2Halk values for surface soils along the first two transects. Our data show that altitude is the dominant factor in determining three plant δ2Halk values. However, we observed substantial differences in the δ2Halk values and their εwax-p ratios for Kobresia, Quercus and Berberis for different climatic regimes and along these three transects. Significantly, for Kobresia along the LM and QL transects, ∆δ2Halk = −84.3‰/km (r2 = 0.94; p < 0.05; n = 4) and − 65.5‰/km (r2 = 0.74; p < 0.01; n = 10), and ∆εwax-p = −80.4‰/km (r2 = 0.93; p < 0.05) and −56.7‰/km (r2 = 0.66; p < 0.01), respectively, were three or four times as large as for the soil δ2Halk values observed along these altitudinal gradients. Overall, the altitudinal lapse rate (ALR) of δ2Halk values and their εwax-p ratios varies between species, with Kobresia being the most negative and Berberis the least negative, potentially resulting from the strong response of monocotyledoneae Kobresia δ2Halk values to cooling with increasing altitude, and the relative influence of cryosphere meltwater at higher altitudes. Thus, impact of climate change on the sedimentary δ2Halk values should therefore be fully taken into account during reconstructions of paleoaltitudes.

Mechanical Mechanism of Fault Dislocation Based on in situ Stress State

Fault dislocation occurs under certain stress conditions. Based on the mechanical relationship between the direction of crustal stress and the occurrence of fault plane, three criterions of fault strike dislocation trend, dip dislocation trend and fault dislocation or not are put forward, According to these three criteria, the fault slip and the type of slip can be inferred. The parameters that have great influence on the characteristics of fault slip are: fault dip angle, angle between horizontal principal stress and fault strike, depth, lateral pressure coefficient, internal friction angle and cohesion of fault plane. Fault slip is more likely to occur in the environment of high deviation stress, low friction angle and dip angle of about 40°. Fault rupture is a point-to-surface and deep-to-shallow process. When the criterion f2 of the local position of the fault is greater than 0, it will lead to the slip of the nearby fault. When the slip range of the fault extends to the surface, it will cause large earthquakes with large-scale surface rupture. The theoretical calculation is basically consistent with the numerical simulation results. According to the theory in this paper, the slip instability state of Longmen Mountain Fault Zone under different stress conditions is calculated, the results show that when the lateral pressure coefficient is greater than 2.5, dislocation occurs in the deep part of the fault.

Soil moisture estimation in the transition zone from the Chengdu Plain region to the Longmen Mountains by field measurements and LANDSAT 8 OLI/TIRS-derived indices

Soil moisture is a key element in hydrological processes, and the accessibility of the moisture in the soil controls the mechanisms thereof amid land surface and atmospheric progressions. Many studies have examined the role of the land surface temperature (LST) and normalised difference vegetation index (NDVI) in changes in soil moisture. Nevertheless, an understanding of the influence of the temperature vegetation dryness index (TVDI), which combines the LST and the NDVI, on soil moisture remains elusive, including in the transition zone area from the Chengdu Plain region to the Longmen Mountains (TZ). In this study, the TVDI was calculated based on the NDVI and LST, using LANDSAT 8 operational land imager/thermal infrared sensor (OLI/TIRS) images. From the TVDI, regression models were trained by using 96 observation points of in situ soil moisture measurements to calculate the soil moisture in the transition zone. The results revealed that there is a strong and significant negative correlation between the TVDI and the in situ measured soil moisture (P < 0.05, r = 0.710, R2 = 0.504). This indicates that the TVDI can reflect the soil moisture status in the TZ. The overall spatial patterns of soil moisture content were relatively high in the northwestern and central mountainous areas but were relatively low in the southeastern plains. Our study uniquely illustrates the spatial patterns of the relationship between TVDI variability and soil moisture variability in the TZ, western China and provides an approach for using remotely sensed soil moisture to optimise the parameterisation of soils in agricultural water management.

Facies model of a mixed siliciclastic-carbonate ramp of the Ma’antang Formation (Carnian period), Sichuan Basin, China

The Ma’antang Formation of Late Triassic is of great importance in petroleum exploration in Sichuan Basin, China, but its sedimentary facies and thickness distribution need further specific investigation. In this paper, the concerning types, distribution, facies model, and controls of sedimentary facies of the Ma’antang Formation are thoroughly discussed, based on an analysis of 130 wells and 12 outcrops in the whole basin. As a result, it is proposed that the Ma’antang Formation is of siliciclastic-carbonate ramp facies model, including seven types of sedimentary facies: open sea shelf, organic reef, bioclastic bank, oolitic shoal, interbank sea, tidal flat, and delta. The organic reef, bioclastic bank, and oolitic shoal are distributed along the Longmen Mountain belt in the southwest part of the basin; the tidal flat, consisting of gray and black mudstone interbedded with thin siltstone and coal bed, is mainly located in the middle of the basin; the delta is distributed chiefly in the northwest of the basin. Three controls are contributed to the formation of the siliciclastic-carbonate ramp, including the flattish palaeotopography, the abundant supply of terrigenous clast and lower rate fluctuation of base level during Carnian period. Four types of reservoirs (organic reef, bioclastic bank, and oolitic shoal reservoir and deltaic reservoir) are developed in the Ma’antang Formation and two types of source rocks (the Ma’antang Formation shale and Xiao’tangzi Formation shale) can supply abundant hydrocarbon to it. The reservoirs and source rocks form efficient assemblages of source rock and reservoir vertically.

The mountain torrent disasters and its effect on sediment transport after the Wenchuan earthquake

By analyzing the formation causes of the mountain torrent disasters as well as the distribution characteristics of rainstorm in Longmen Mountain area, and citing the typical post-seismic the mountain torrent disasters within 2008~2013 after the Wenchuan earthquake in the area as example, the character of post-seismic floods, the spatial distribution of the devasting post-seismic debris flows, the critical rainfall to trigger the mountain torrent disasters and so on are explored. Besides, the sediment before and after the Wenchuan earthquake of the Minjiang watershed are compared. The conclusions are as following: (1) The time of the post-seismic flash floods and debris flows after the Wenchuan earthquake are centered from July to September, which is consistent with the rainfall of the area. (2) Rather than the debris flows are triggered when the rainfall intensity reached the critical rainfall intensity, those are closely linked with the pre-accumulated rainfall. That is to say, the more pre-accumulated rainfall, the more probability of the debris flows. (3) After the Wenchuan earthquake, the total sediment increases 13.8%~70%. But the increasing range is varied from year to year. In the year when the debris flow occurred, the sediment shall increase drastically.

Relationships between hydrocarbon evolution and the geochemistry of solid bitumen in the Guanwushan Formation, NW Sichuan Basin

Abstract Recently, the Devonian Guanwushan Formation in the northwestern Sichuan Basin gained industrial attention when solid bitumen was discovered in reservoirs and outcrops. This discovery initiated the exploration and development of the Devonian natural gas. Devonian in the northwestern Sichuan Basin is a new stratum for the exploration and development of Paleozoic marine natural gas in Sichuan Basin. However, the unclear recognition on the genesis, the sources and the hydrocarbon evolution history of solid bitumen and natural gas seriously restricted further exploration and development. Based on the solid bitumen reflectance, carbon isotopes, saturated hydrocarbon chromatography, and solvent extract bitumen biomarkers combined with the component and carbon isotopes of natural gas, comprehensive analyses have been performed on the origin of the solid bitumen and the accumulation and evolution of the natural gases. The results showed that the outcrop solid bitumen is derived from biodegraded oil from the Lower Cambrian source rocks, and is characterised by low bitumen reflectance, low saturated/aromatic hydrocarbon ratios, seriously damaged normal-alkanes, and severe migration of the gas chromatographic baseline. The reservoir bitumen formed through thermal cracking of oil from Lower Cambrian and Lower Permian source rocks, and is characterised by high bitumen reflectance, high saturated/aromatic hydrocarbons, and complete normal-alkanes. The differences of tectonic evolution take control of the two different-genesis bitumen. The Longmen Mountain strata in the northwestern Sichuan Basin were uplifted sharply after the Jurassic and the early generated crude oil was biodegraded during uplifting and formed the outcrop bitumen. However, strata in Well Shuangtan-3 (ST3) continued to subside and the paleo reservoir thermal-cracked during deep burial into dry gas and heavy components gathered to form reservoir bitumen. Revealing the Devonian hydrocarbon evolution in Sichuan Basin is of highly significance and is meaningful to guide further researches on the gas-source correlation of natural from paleo-strata. It is of great significance to reveal the Devonian hydrocarbon evolution in Sichuan Basin and to guide further researches on the gas-source correlation of natural gas from paleo-strata.

Groundwater Chemical Characteristics and Analysis of Their Controlling Factors in an Alluvial Fan of Jianjiang River

The Jianjiang alluvial fan is one of the frontal alluvial fan clusters in the Longmen Mountains of the Chengdu Plain. In order to study the groundwater chemical characteristics and controlling factors, we collected 30 groups of groundwater samples on site in May 2018. Descriptive statistical analysis, Piper diagrams, ArcGIS spatial analysis, ion-scale coefficients, and other methods were used to analyze the chemical types and ion spatial distribution characteristics. The main factors controlling the chemical evolution processes of the groundwater and the main sources of ions are discussed. The northeast area of the alluvial fan contains mostly weakly acidic waters, accounting for 13.33%, the rest being weakly alkaline. Groundwater chemical types included HCO3·SO4-Ca, HCO3-Ca, HCO3·SO4-Ca·Mg, and HCO3·SO4-Ca·Na, and all groundwater was freshwater. The main ion spatial variation coefficient were between 0.22 and 0.91, and the variability was moderate. The chemical evolution processes of groundwater was mainly controlled by leaching, and human activities have certain influence. The effect of evaporation and concentration, and atmospheric rainfall, and alternating cation adsorption were not obvious.

Geodynamic simulation of the WenChuan Ms8.0 and Lushan Ms7.0 earthquakes

The Lushan Ms7.0 earthquake, occurred on April 20th, 2013, is another strong earthquake that occurred on Longmen Mountain Faults after the Wenchuan Ms8.0 earthquake. In this paper we construct a finite element model depicting fault frictional mechanism to study the geodynamics of these two strong earthquakes. The locations of the initial rupture points and the dislocation forms of the Wenchuan earthquake and Lushan earthquake are simulated to find out the potential relationship between the two earthquakes. Simulative results show that the elevation, fault geometry, and the different rheological strengths between the Sichuan basin and Tibetan plateau play an important role in the earthquake dynamics. The dynamic simulation shows the initial rupture points are located at Yingxiu county and the rupture process is mainly along the northeast direction for the Wenchuan earthquake. In particular, the different frictional strengths caused by the fluid pressure decrease between the southern and northern segments of Longmenshan faults after the Wenchuan earthquake have affected the initial rupture point and the fault dislocation form of the Lushan earthquake, when considering the thrust of Tibetan plateau to Sichuan basin as the major dynamic source.

Cement characteristics and effects on dolomite reservoir pores in the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin

Cement characteristics and effects on dolomite reservoir pores in the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin

Development of Land Resources in Transitional Zones Based on Ecological Security Pattern: A Case Study in China

Land use based on landscape ecological security pattern provides a scientific basis for alleviating conflicts between land conservation and human use, ensuring concomitant economic development and ecological integrity. The majority of studies by Chinese researchers have been focused on the carrying capacity and land development intensity, and less attention has been paid to the ecological security pattern of the landscape in Mianzhu in the transitional zone between the Chengdu Plain region and the Longmen Mountains, western China. However, land resources are undergoing significant changes resulting from land use associated with rapid economic development and demographic growth. In this study, we constructed a minimum cumulative resistance model in Mianzhu in the transitional zone, and the land space was divided into optimized development areas, key development areas, restricted development areas, and prohibited development areas according to the landscape ecological security pattern based on the model surface. These land use types covered 7218.39 ha, 17,974.75 ha, 21,545.39 ha, and 77,791.46 ha, respectively. We also examined land use changes over the last 20 years and quantitatively analyzed the relationships between land use changes and geographic factors based on remote sensing and geographic information system. The information obtained from this research ultimately impacts future policies and plans regarding land resources and can be used to promote the sustainable use of land resources in the region.

Beichuan's Tragedy: Tan Zuoren and the politics, suffering, and injustice of the Wenchuan earthquake

AbstractIt has been argued that Tan Zuoren's essay ‘Longmen Mountain, please bear witness for the children of Beichuan’ is not only an attempt to narrate an alternative version of the story of the Wenchuan earthquake but also to present a vision of an alternative future for Chinese society. The building blocks for this alternative future would be finding a balance between human beings and nature, respect for minorities, and responsible rule. Tan does not demand the end of Communist Party rule, but explains how the system could be changed to make it better for both the people and nature. The keys to achieving this goal are rectifying historical injustices, an honest examination of mistakes, and respect for ordinary people.

Multifractal fluctuations of waiting time sequence of aftershocks

After a large earthquake there will be series of aftershocks. The analyzed regularity of these aftershocks will be conducive to recognize the characteristics of the aftershocks and explore their formation and evolution, and also to provide theoretical support for Earthquake Disaster Mitigation. Detrended fluctuation analysis (DFA) and multifractal methods are applied to the time-scaling properties analysis of the waiting time sequence of aftershocks (WTSAs) of the Wenchuan Ms8.0 earthquake occurred on Longmen mountain tectonic zone of Sichuan Province in China. The results show that the WTSAs is characterized by multifractal scaling.

Dynamic monitoring of soil erosion in the upper Minjiang catchment using an improved soil loss equation based on remote sensing and geographic information system

AbstractThe upper Minjiang catchment has suffered intensive soil erosion due to frequent geologic hazards and its fragile ecosystem zone with steep slopes. This study fully considers the topographic features and surface cover and introduces improved methods of K, LS, and C to establish a soil loss equation for the upper Minjiang catchment based on remote sensing and geographic information system. Spatial–temporal change patterns of soil erosion intensity and its driving mechanisms are then analyzed and discussed. Results show that (a) the soil erosion modulus of the upper Minjiang catchment for 2005 and 2015 were 1,577.29 t km−2 a−1 and 1,619.77 t km−2 a−1, both of which belong to a level of mild erosion. The slight and mild erosion zones covered the largest area and were widely distributed in the northern part of the study area, whereas zones of intensive and severe erosion were mostly concentrated in Wenchuan County and the lower reaches of the Heishui and Zagunao Rivers. (b) During 2005–2015, changes in erosion intensity showed a trend of “overall stability, local deterioration.” Zones of mild, moderate, and intensive increase were mainly concentrated in the Longmen Mountain Fault Zone, such as southern Maoxian and western Wenchuan Counties. (c) Returning cultivated land to forest and grasslands greatly reduced the erosion intensity and erosion amount, whereas geologic hazards aggravated the soil erosion condition. Zones with a slope of &lt;35° had a positive relationship with soil erosion intensity; these areas are crucial control areas for soil preservation and containing soil loss. In addition, grassland is more effective in conserving soil and water than forestland in the upper Minjiang catchment in areas of steep terrain. These results provide an important reference for estimating soil loss intensity in southwest mountainous regions of China, particularly in the Hengduan Mountains, and greatly contribute to the planning of soil and water conservation.

Geological effects influence population genetic connectivity more than Pleistocene glaciations in the water strider Metrocoris sichuanensis (Insecta: Hemiptera: Gerridae)

AbstractAimPalaeoclimatic and palaeogeological events have been identified as two main factors that influence the genetic structuring of extant organisms. We studied a montane stream‐dwelling insect, Metrocoris sichuanensis, to explore the relative roles played by these two factors in population genetic connectivity.LocationSichuan Basin, China.MethodsMitochondrial (COI, COII, Cytb, 16S) and nuclear (EF‐1α, ITS1) markers were sequenced from 208 individuals. Suitable habitat shifts from the Last Glacial Maximum (LGM) to the present were predicted through fine‐tuned ecological niche modelling (ENM). Phylogenetic and phylogeographical analyses were conducted to reveal the population genetic structure. Intraspecific divergence and expansion times were estimated using beast. Finally, the least cost path (LCP) method coupled with migrate analysis was used to identify possible dispersal corridors and estimate the asymmetric gene flow.ResultsOur ENM results suggested that population habitat connectivity did not change both in the LGM and current conditions. Whole haplotypes were separated into four highly supported clades/haplogroups that exhibited strong geographical structure. The splitting events between the four lineages likely date back to the Early Pleistocene. Bayesian skyline plot (BSP) indicated a moderate demographic growth from the LGM to the present. A putative dispersal corridor was detected along the Longmen Mountains thrust belt, with unidirectional gene flow from north to south.Main conclusionOur findings support the geographical isolation of the genetic lineages and a deep early Pleistocene split in M. sichuanensis. Landscape connectivity analysis incorporating the genetic data and the ENM prediction revealed that population genetic connectivity was strongly associated with stable climatic habitats shaped by complex topography. The drainage system might have assisted the rapid movement of populations along the Longmen Mountains thrust belt. A strategy for researching the population genetic connectivity of narrow endemics, such as M. sichuanensis, in global biodiversity hotspots is proposed and discussed in this paper.