Influence of mosses on the weathering features of sandstone and carbonate rocks in the subalpine region of western Sichuan

LIU Han; PU Wanqiu; WANG Panpan; HUANG Chengmin

doi:10.11932/karst20250306

Abstract：Sichuan Province is located in the Southwest China,with its western mountainous area serving as a transitional zone between the Qinghai-Xizang Plateau and the Sichuan Basin.The climate is complex,characterized by abundant rainfall,and the terrain is mainly mountainous,featuring significant variations in elevation.The geological conditions are complex,tectonic activities are frequent,and geological disasters occur regularly.In addition,with the increasing intensity of human activities,exposed slopes and rock masses are widely distributed.The weathering and detachment of rock fragments can easily trigger secondary disasters,posing potential threats.The widespread presence of rocky slopes makes these areas prone to such events,underscoring the urgent need for ecological restoration.Mosses play a critical role in ecological succession and soil formation on rock surfaces,acting as pioneer species that promote the development of thin soil layers.Exploring the impact of moss growth on rock weathering processes is beneficial for finding ways to promote ecological restoration.This study aims to investigate the weathering processes and mechanisms in this region by analyzing weathered rock bodies and bedrock properties under varying weathering conditions to elucidate their microscopic characteristics.Additionally,the influence of moss growth on rock weathering was further investigated.We collected samples from carbonate rocks and sandstones at various sites within several counties in western Sichuan Province.Our study focused on sites with varying degrees of moss coverage and differing weathering durations.The analyses included examining the microstructural features of weathered rock surfaces,assessing mineral composition,and analyzing elemental variations to understand how mosses interact with these geological materials.These investigations were conducted by using electron microscopy,scanning electron microscopy(SEM),X-ray diffraction(XRD)for mineral composition,energy-dispersive spectroscopy(EDS),and other analytical techniques. The results indicate that as weathering progressed,the breakdown of mineral crystal structures,the development of fractures in the rock mass,and the formation of secondary minerals occurred in both sandstone and limestone.These processes were accompanied by the infiltration of iron oxides and organic matter,and they intensified over time.Notably,sandstone exhibited a more pronounced weathering response during the early stages compared to limestone.During the weathering of carbonate rocks,a large amount of secondary minerals was produced,and the mineral composition evolved from simple to complex.In contrast,the main component of sandstone weathering has consistently been quartz;as weathering progressed,secondary minerals disappeared,and the mineral composition shifted from complex to single.The elemental content in limestone did not change significantly during the early stages of weathering,while the elemental content in sandstone changed markedly.In total,results show that the weathering of carbonate rocks is predominantly chemical,whereas physical weathering is more pronounced in sandstone. Furthermore,the impact of mosses on rock weathering is complex.For carbonate rocks,initial weathering stages exhibited minimal elemental changes with moss presence;however,with prolonged exposure,significant modifications in structural integrity and chemical composition occurred.The percentage of carbon and other elements,such as calcium and magnesium,changed markedly,due to the bioerosion effects of moss-generated organic acids,with carbon increasing and calcium and magnesium decreasing.Microstructural analysis revealed that moss-covered rocks exhibited deeper and wider fissures compared to their bare counterparts.This increase in fissure size is correlated with the mechanical and biochemical actions of mosses,which exploited small crevices to enhance their growth and further facilitate the weathering process.Over time,mosses create a conducive environment for microbial activity,which adds to the biochemical weathering of the rock substrate.When mosses grew on the surface of sandstone,it exacerbated the already intense physical weathering of sandstone during the early stages and resulted in compositional changes.Overall,moss growth accelerates the weathering process of rocks,but its influence is not significant during the early stages. The findings indicate that mosses significantly contribute to both the physical and chemical weathering processes of rocks,which in turn influence soil formation and ecological stability.These insights have important implications for ecological restoration strategies on exposed rock slopes,particularly in areas susceptible to erosion and geological instability.By harnessing the natural weathering capabilities of mosses,we can develop sustainable methods for restoring degraded landscapes and mitigating ecological risks associated with exposed rock surfaces.For the ecological restoration of limestone slopes,the use of mosses is more effective than its application on sandstone,as it provides protective benefits over time.Therefore,it is essential to consider the differences in rock types when we select suitable plants for ecological rehabilitation.Future studies should explore the long-term effects of moss-induced weathering on soil development and ecosystem restoration,particularly in sensitive mountainous regions.