Key Factors for the Rapid Cultivation of Lithophytic Moss Crusts and Preliminary Trials in the Ecological Restoration of Rocky Slopes

Effect of moss crusts on mitigation of post-fire soil erosion

Moss-dominated biocrusts (moss crusts) are a feasible approach for the ecological restoration of drylands, but difficulty obtaining inoculum severely limits the progress of large-scale field applications. Exogenous microorganisms could improve moss growth and be conducive to moss inoculum propagation. In this study, we investigated the growth-promoting effects and potential mechanisms of exogenous microorganism additives on moss crusts. We used an incubator study to examine the effects of inoculation by heterotrophic microorganisms (Streptomyces pactum, Bacillus megaterium) and autotrophic microorganisms (Chlorella vulgaris, Microcoleus vaginatus) combined with Artemisia sphaerocephala gum on the growth of Bryum argenteum, the dominant moss crusts species in sandy deserts. Amplicon sequencing (16S and 18S rRNA) and PICRUSt2 were used to illustrate the microbial community structure and potential function in the optimal treatment at different developmental stages. Our results showed that exogenous microorganisms significantly promoted moss growth and increased aboveground biomass. After 30 days of cultivation, the Streptomyces pactum (1 g kg–1 substrate) + Chlorella vulgaris (3.33 L m–2) treatment presented optimal moss coverage, height, and density of 97.14%, 28.31 mm, and 2.28 g cm–2, respectively. The best-performing treatment had a higher relative abundance of Streptophyta—involved in moss growth—than the control. The control had significantly higher soil organic carbon than the best-performing treatment on day 30. Exogenous microorganisms improved eukaryotic community diversity and richness and may enhance soil microbial functional and metabolic diversity, such as growth and reproduction, carbon fixation, and cellulose and lignin decomposition, based on functional predictions. In summary, we identified the growth-promoting mechanisms of exogenous additives, providing a valuable reference for optimizing propagation technology for moss inoculum.

Sprayed planting concrete (SPC) can be used for the ecological restoration of rocky steep slopes. It is a kind of outside-soil material with excellent soil and slope stabilization performance, and plants can grow in SPC, thus achieving harmony between engineering stability and ecological restoration and improving the landscape and ecosystem. The addition of cement is the key to allowing SPC to achieve slope stabilization and prevent soil erosion. However, the addition of cement can cause SPC to have high alkalinity, overheating (cement generates hydration heat), and excessive hardening, which are not conducive to the growth of plants and can lead to poor ecological performance of SPC for slope ecological restoration. We studied the improvement of the ecological performance of SPC by using a polymer composite material composed of a polymer adhesive material and a polymer water-retaining material. This paper studied the improvement effects of the polymer composite material on the ecological performance of SPC used in slope ecological restoration through a laboratory erosion resistance test and a plant growth test. The results showed that SPC with the addition of polymer composite material can reduce its cement content by about 50% while still retaining excellent erosion resistance performance when it is used in slope ecological restoration. Additionally, the plant germination rates and plant heights when using the SPC improved by polymer composite material were increased by 190% and 110%, respectively. These results show that polymer composite material can significantly improve the ecological performance of SPC and effectively improve its slope ecological restoration effects. This study provides theoretical and technical support for the application of SPC in ecological restoration on rocky steep slopes.

To address the ecological restoration needs of steep rocky slopes in southwestern China, this study systematically investigated the mechanisms by which bioremediation technologies influence soil microbial community structure and functional genes involved in carbon and nitrogen cycling. By spraying composite microbial agents (containing functional strains such as Clostridium and Desulfovibrio) and combining Illumina high-throughput sequencing with metagenomic analysis, we evaluated dynamic changes in soil fertility, microbial diversity, and functional genes over a 13 months restoration period. The results showed that total nitrogen (TN), total carbon (TC), and organic matter (OM) contents in the bioremediation area increased by 547.4%, 540.6%, and 1765.7%, respectively, compared to the natural crust group, significantly enhancing the nutrient supply capacity of barren rocky soil. Microbial diversity and richness increased, with functional phyla such as Proteobacteria and Actinobacteriota exhibiting abundance increaseed of 24.5% and 3.4%, respectively, driving synergistic enhancement of carbon, nitrogen, and phosphorus cycling. Metagenomic analysis revealed that carbon fixation genes and nitrogen fixation gene clusters (e.g., nifZ, nifX) were upregulated in the restoration group compared to the control group. This enhancement was achieved by regulating CO2 hydration and biological nitrogen fixation pathways, significantly improving carbon and nitrogen sequestration efficiency in the ecosystem. From a molecular ecology perspective, this study elucidates the mechanism by which microbial remediation facilitates rapid ecological restoration of slopes through reshaping functional microbial networks and activating key metabolic gene expression. These findings provide a theoretical foundation for sustainable restoration of rocky slopes.

Interplays between plants and environmental factors determine pullout resistance on different revegetated slopes in mining areas

Induced and natural moss soil crusts accelerate the C, N, and P cycles of Pb[sbnd]Zn tailings

The restoration of moss crust (moss-dominated biological soil crust) through artificial cultivation is of great significance for preventing soil wind erosion and desertification in arid and semi-arid regions. However, the tiny size of moss plant and associated observational challenge hindered the establishment of scientifically validated and standardized indicators for assessing the growth and development of artificial moss crusts. We measured moss crust development indicators, including plant density, coverage, and height every five days during a 60-day cultivation experiment, as well as the dry weight and thickness of moss crust after the cultivation. We determined the eva-luation indicators for the artificial cultivation of moss crusts by analyzing the relationship between those indicators and the stability (characterization of erosion resistance) of moss crusts. The results showed that the new gametophytes germinated after five days cultivation. Plant individual density and coverage of moss crust increased rapidly and turned stable after 35 to 40 days of cultivation. The moss height remained within a narrow range of 1.53 to 1.63 mm during the cultivation. Dry weight of moss and thickness of moss crusts reached 0.0074 g·cm-2 and 6.30 mm at the end of cultivation, respectively. Moss density exhibited the highest sensitivity to cultivation time, followed by coverage, whereas plant height showed relatively low sensitivity. The stability index of moss crusts cultivated for 60 days ranged from 0.12 to 0.69, which were positively related with plant density and coverage. The comprehensive scoring for development indicators, including moss density, coverage, plant height, biomass, and thickness of moss crusts indicated that moss plant density and coverage are key indicators for assessing the growth and development of artificial moss crusts cultivation.

Engineering construction and mining activities have resulted in numerous exposed rocky slopes, posing significant geological and ecological challenges. To address these issues, this study developed compound microbial agents composed of functional microorganisms and applied them in a field-based ecological restoration project on typical high and steep rocky slopes in Southwest China. The aim was to restore the micro-ecological environment of the slopes by reconstructing the soil conditions. After 240 days of restoration, soil available phosphorus increased from < 2.0 to 6.10mg/kg, available potassium from 62.80 to 75.00mg/kg, organic matter from 8.90 to 12.86g/kg, and organic carbon from 0.70 to 0.73%. Total nitrogen and total phosphorus slightly increased, indicating improved soil fertility. The addition of compound microbial agents enhanced microecological stability while maintaining the overall structure of the indigenous microbial communities. The progressive development of biological soil crusts and rock fissures facilitated the colonization of algae, lichens, mosses, and higher plants. By the 8th month, vegetation coverage exceeded 30% in some areas. This study presents an effective field-based model for the microbial ecological restoration of rocky slopes and offers insights into ecosystem-recovery mechanisms supporting sustainable land management.

Biological soil crusts (BSCs) perform vital ecosystem services, but the difference in biological components or developmental level still affects the rate and type of these services. In order to differentiate crust successional stages in quantity and analyze the relationship between crust developmental level and successional stages, this work determined several biological indicators in a series of different developmental BSCs in the Shapotou region of China. The results showed that crust developmental level (level of development index) can be well indicated by crust biological indicators. Photosynthetic biomass was the most appropriate to differentiate crust successional stages, although both photosynthetic biomass and respiration intensity increased with the development and succession of BSCs. Based on of the different biological compositions, BSCs were quantificationally categorized into different successional stages including cyanobacterial crusts (lichen and moss coverages <20 %), lichen crusts (lichen coverage >20 % but moss coverage <20 %), semi-moss crusts (moss coverage >20 % but <75 %), and moss crusts (moss coverage >75 %). In addition, it was found that cyanobacterial and microalgal biomass first increased as cyanobacterial crusts formed, then decreased when lots of mosses emerged on the crust surface; however nitrogen-fixing cyanobacteria and heterotrophic microbes increased in the later developmental BSCs. The structural adjustment of biological components in the different developmental BSCs may reflect the requirement of crust survival and material transition.

Summary1. Biodiversity–environment relationships are increasingly well‐understood in the context of species richness and species composition, whereas other aspects of biodiversity, including variability in functional diversity (FD), have received rather little rigorous attention. For streams, most studies to date have examined either taxonomic assemblage patterns or have experimentally addressed the importance of species richness for ecosystem functioning.2. I examined the relationships of the functional biodiversity of stream macroinvertebrates to major environmental and spatial gradients across 111 boreal headwater streams in Finland. Functional biodiversity encompassed functional richness (FR – the number of functional groups derived from a combination of functional feeding groups and habit trait groups), FD – the number of functional groups and division of individuals among these groups, and functional evenness (FE – the division of individuals among functional groups). Furthermore, functional structure (FS) comprised the composition and abundance of functional groups at each site.3. FR increased with increasing pH, with additional variation related to moss cover, total nitrogen, water colour and substratum particle size. FD similarly increased with increasing pH and decreased with increasing canopy cover. FE decreased with increasing canopy cover and water colour. Significant variation in FS was attributable to pH, stream width, moss cover, substratum particle size, nitrogen, water colour with the dominant pattern in FS being related to the increase of shredder‐sprawlers and the decrease of scraper‐swimmers in acidic conditions.4. In regression analysis and redundancy analysis, variation in functional biodiversity was not only related to local environmental factors, but a considerable proportion of variability was also attributable to spatial patterning of environmental variables and pure spatial gradients. For FR, 23.4% was related to pure environmental effects, 15.0% to shared environmental and spatial effects and 8.0% to spatial trends. For FD, 13.8% was attributable to environmental effects, 15.2% to shared environmental and spatial effects and 5% to spatial trends. For FE, 9.0% was related to environmental variables, 12.7% to shared effects of environmental and spatial variables and 4.5% to spatial variables. For FS, 13.5% was related to environmental effects, 16.9% to shared environmental and spatial effects and 15.4% to spatial trends.5. Given that functional biodiversity should portray variability in ecosystem functioning, one might expect to find functionally rather differing ecosystems at the opposite ends of major environmental gradients (e.g. acidity, stream size). However, the degree to which variation in the functional biodiversity of stream macroinvertebrates truly portrays variability in ecosystem functioning is difficult to judge because species traits, such as feeding roles and habit traits, are themselves strongly affected by the habitat template.6. If functional characteristics show strong responses to natural environmental gradients, they also are likely to do so to anthropogenic environmental changes, including changes in habitat structure, organic inputs and acidifying elements. However, given the considerable degree of spatial structure in functional biodiversity, one should not expect that only the local environment and anthropogenic changes therein are responsible for this variability. Rather, the spatial context, as well as natural variability along environmental gradients, should also be explicitly considered in applied research.

Biological soil crusts (biocrusts) are the common cover in arid and semiarid areas. Together with plants, biocrusts affect runoff and flow velocity. However, few studies have focused on the effects of the co-covering of plant and biocrust (plant+biocrust) on the flow velocity, with a knowledge gap in the study of driving factors for slope erosion in arid and semiarid areas. In this study, simulated rainfall experiments were used to investigate the effects of biocrust and three types of biocrusts (more cyanobacteria less moss, more moss less cyanobacteria, and moss) on the flow velocity of revegetated grassland in the hilly Loess Plateau. The results showed that plant and plant+biocrust significantly reduced flow velocity, with that of plants and plant+biocrust being 70.7% and 83.1% lower than bare soil. The reduction benefits of plant and biocrust on flow velocity were 70.7% and 12.4%, respectively, when they were co-covered. Biocrust composition under plant cover affected flow velocity. The reduction benefits of more cyanobacteria less moss, more moss less cyanobacteria, and moss crust on flow velocity were 11.5%, 12.4%, and 19.4%, respectively. There was a significant negative correlation between flow velocity and moss coverage and a significant positive correlation between flow velocity and cyanobacteria coverage. The relationship between moss cove-rage (x) and flow velocity (y) was y=-2.081x+0.03 (R2=0.469). The moss coverage was a key factor affecting the flow velocity of co-covering of plant and biocrust slope with similar plant coverage (40%±10%). In conclusion, biocrusts under plant cover significantly slowed flow velocity, and the effect magnitude was related to its composition, implying that the role of biocrusts should be considered in understanding the mechanism underlying slope erosion in revegetated grassland.

The study area, Shapotou district (37°27' N, 104°57' E) of Ningxia Hui Autonomous Region is situated in the southeastern fringe of the Tengger Desert of China. A study of species identification, coverage and biomass in the soil microbiotic crusts of fixed sand dunes was conducted in Shapotou district, from which we found two families, seven genera and sixteen species of mosses. Didymodon constrictus (Mitt. ) Saito and D. tectorwn ( C. Muell. ) Saito were reduced to synonymy of D. vinealis ( Brid.) Zand. by Zander and Red-fearn. Crossidium chloronotos (Brid. ) Limpr. , Crossidium aberrans Holz. Bartr. Aloina obliquifolia ( C. Muell. ) Broth. and Tortilla atrovirens ( Sm. ) lindb. are new to Shapotou district. Bryum argenteum is an eu-rytopic species that survives on all kinds of habitat, and is the dominant component that forms moss synusia. The community of Didymodon vinealis, D. rigidulus Hedw. var. ditrichoides and Syntrichia bidentata are found on hillocks and are randomly distributed in crusts. Diversity of species is the highest in this area in the natural fixed dunes, with sixteen species, followed by five species of mosses (31.3%) in the fixed dunes of 1956, four species of mosses (25.0%) in the fixed dunes of 1964, and only two species of mosses (12.5%) in the fixed dunes of 1981. The total coverage of mosses and algae increased with the fixed-sand time, hi different ages, the coverage of mosses and algae exist in an equal distance gradient, while in the fixed dunes they exist along the slope with the coverage of mosses decreasing as that of algae increased. A determination of biomass and binding-sand quantity of the dominant species-Bryum argenteum showed that its biomass (944.03 kg·hm-2) and binding-sand (3.925 × 104 kg·hm-2) quantity increased when the fixed sand time prolonged in moss crusts of the fixed dunes of 1950s. While the rate of binding-sand of Bryum argenteum decreased, its saturated water absorption had a positive correlation with biomass of 7.06 ×103 kg·hm-2 . Therefore the results indicate that the moss crusts had a strong ability to absorb and reserve water, which is of ecological significance in arid desert region.

Soil salinization poses a substantial threat to global food security, particularly under the influence of climate change, and is recognized as one of the most urgent challenges in land degradation. This study aims to elucidate the challenges associated with managing arid and semi-arid saline-alkali lands in China’s Ningxia province and propose feasible solutions. To assess moss crust colonization, we measured changes in organic matter and chlorophyll levels. Additionally, we investigated the impact of an interlayer composed of Goji berry root bark using liquid chromatography-mass spectrometry analysis, biological enzyme activity analysis, and metagenomic sequencing. A total of 45 endophytes were isolated from the moss crust. The most significant colonization of moss crusts was observed when the Goji berry root bark was used as the interlayer, resulting in a significant increase in chlorophyll content. Several responses were identified as pivotal factors facilitating moss crust growth when the Goji berry root bark was used as the interlayer. In saline-alkali soil, the Goji berry root bark interlayer increased the activities of sucrase, urease, and alkaline phosphatase. Metagenomic data analysis revealed variations in the relative abundance of microorganisms at the phylum level, although these differences were not statistically significant. Evaluation of the impact of physical isolation and moss crust transplantation on the ecological restoration of saline-alkali soil using liquid chromatography-tandem mass spectrometry and metagenomic sequencing indicated that the Goji berry root bark as a physical isolation method promotes moss crust colonization in saline-alkali soil and increases soil organic matter and nutrient elements, offering valuable insights for the ecological management of saline-alkali land and serving as a reference for future research in this field.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00248-024-02473-1.

Karst rocky desertification refers to the process of land degradation caused by various factors such as climate change and human activities including deforestation and agriculture on a fragile karst substrate. Nutrient limitation is common in karst areas. Moss crust grows widely in karst areas. The microorganisms associated with bryophytes are vital to maintaining ecological functions, including climate regulation and nutrient circulation. The synergistic effect of moss crusts and microorganisms may hold great potential for restoring degraded karst ecosystems. However, our understanding of the responses of microbial communities, especially abundant and rare taxa, to nutrient limitations and acquisition in the presence of moss crusts is limited. Different moss habitats exhibit varying patterns of nutrient availability, which also affect microbial diversity and composition. Therefore, in this study, we investigated three habitats of mosses: autochthonal bryophytes under forest, lithophytic bryophytes under forest and on cliff rock. We measured soil physicochemical properties and enzymatic activities. We conducted high-throughput sequencing and analysis of soil microorganisms. Our finding revealed that autochthonal moss crusts under forest had higher nutrient availability and a higher proportion of copiotrophic microbial communities compared to lithophytic moss crusts under forest or on cliff rock. However, enzyme activities were lower in autochthonal moss crusts under forest. Additionally, rare taxa exhibited distinct structures in all three habitats. Analysis of co-occurrence network showed that rare taxa had a relatively high proportion in the main modules. Furthermore, we found that both abundant and rare taxa were primarily assembled by stochastic processes. Soil properties significantly affected the community assembly of the rare taxa, indirectly affecting microbial diversity and complexity and finally nutrient acquisition. These findings highlight the importance of rare taxa under moss crusts for nutrient acquisition. Addressing this knowledge gap is essential for guiding ongoing ecological restoration projects in karst rocky desertification regions.

Water erosion of rare earth tailings poses significant ecological risks, while moss crusts are widely distributed across these tailings. However, their role in erosion mitigation remains poorly understood. Using a single-raindrop simulation experiment, this study quantified the kinetic energy reduction capacity of moss crusts at four developmental stages (I: bare soil; II–IV: increasing cover, biomass, and height). Key results include: (1) Moss crusts markedly increased the accumulated kinetic energy required to disrupt the surface ( Emoss). At 1 cm thickness, Emoss values for developmental stages II, III, and IV were 0.04, 0.18, and 4.61 J, respectively—stage IV exhibited 363-fold greater resistance than bare soil (stage I). (2) After moss removal, the underlying soil's resistance ( Eunder) dropped sharply (averaging 0.01 J across stages), with no differences between developmental stages. Moss crusts reduced raindrop kinetic energy by 65.04% (stage II), 92.79% (stage III), and 99.72% (stage IV). (3) Resistance correlated strongly with slope and soil moisture: air-dried crusts exhibited higher Emoss (0.35 J) than wet samples, and steeper slopes (25°–30°) increased Emos s by 10-fold compared to flat terrain. These findings demonstrate that moss crusts act as effective physical barriers against splash erosion, offering a scalable strategy for ecological restoration of degraded rare earth tailings in subtropical regions.