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Global climate changes result in the expansion of lower elevation plants to higher elevations. The rapid upward expansion of herbaceous plants into the alpine tundra on Changbai Mountain resulted in changes in different levels of ecosystem organization. However, the responses and feedback of litter properties and soil mesofauna to herbaceous plants expansion have not been studied yet. To understand the mechanisms underlying those changes, we conducted a field experiment in the range of 2250–2300 m in the alpine tundra of the Changbai Mountain and collected a total of 288 samples from four degrees of herbaceous plants expansion to study the litter physiochemical properties, soil mesofauna, and soil nutrient contents, and their relationships in that tundra ecosystem suffered from various degrees of herbaceous invasion. We found that herbaceous plant expansion is responsible for a major shift in the dominant species of soil mesofauna from mites to collembolan and has significant impacts on the community structure (R2=0.54, p=0.001) and diversity of soil mesofauna (Shannon-Weiner index, p=0.01). The increasing herbaceous plant expansion resulted in a significant increase in litter biomass from 91g·m−2 in the original tundra vegetation (OIT) to 118g·m−2 in the moderately invaded tundra (MIT), and an increase in litter thickness from 2.37 cm (OIT) to 3.05 cm (MIT). And, the litter total nitrogen content significantly increased, but the values of the litter carbon content, the lignin content, the C/N ratio, and the lignin/N ratio decreased with increased herbaceous coverage (both p<0.05). The litter physical properties pathway (biomass and thickness) directly explained 31% of the total variance in soil mesofauna diversity and 59% of the total variance in soil mesofauna community composition. Furthermore, both the soil available nutrients (incl. AN and AP) and plant biomass (incl. the total plant biomass and herbs/shrubs biomass) significantly increased with increasing coverage of herbaceous plant (both p<0.05), and litter chemical properties pathway directly explained 50% of the soil nutrient content variance and indirectly explained 20% of soil nutrient by affecting soil mesofauna. We found that both soil available nutrients and soil mesofauna were positively correlated with the herbaceous expansion from OIT to MIT, indicating a positive feedback of herbaceous expansion, and the abundance of soil mesofauna decreased in the severely invaded tundra vegetation, suggesting a negative feedback. While, both litter N content and soil available nitrogen were consistently increased in the severely invaded tundra vegetation, indicating a positive feedback of herbaceous expansion. Therefore, this study provides new insights into the process of herbaceous plant expansion into tundra, and provides possible evidence for further expansion according to responses and feedback of in litter properties and soil mesofauna to herbaceous plants expansion. Furthermore, these positive or/and negative feedback systems in the Changbai alpine tundra ecosystem in relation to herbaceous expansion have important implications for the tundra protection, and thus, need to be deeply studied. [ABSTRACT FROM AUTHOR]

Microorganisms drive litter decomposition while maintaining the chemical cycle of ecosystems. We used the dominant vegetation (Imperata cylindrica) in the mining area selected for this study for this experiment to explore fungal community characteristics, key fungal groups, and their associative driving factors during I. cylindrica litter decomposition. Maximum litter C/N values occurred 100days after the commencement of the decomposition experiment during all different recovery years in this copper tailings area. Heavy metals in litter [copper (Cu), zinc (Zn), plumbum (Pb), and cadmium (Cd)] accumulated gradually with decomposition. The dominant fungal phyla observed in the community were Ascomycota and Basidiomycota, while the classes Sordariomycetes and Eurotiomycetes significantly increased as litter decomposition progressed. Degrees of connectivity and interaction between fungal communities were highest during the early litter decomposition stage. Sordariomycetes, Dothideomycetes, and Leotiomycetes all played critical roles in maintaining fungal community relationships. The effect of physicochemical properties and enzyme activities in I. cylindrica litter was significant on the dominant fungi, while driving factors that affected fungal communities differed over different recovery stages. Total nitrogen (TN), heavy metals, pH, and enzyme activities in the little were significantly correlated with fungal community composition. Litter properties throughout the litter decomposition process mainly affected the dynamics of the fungal community structure. The main environmental factors that affected fungal community structure were copper content and pH. Dichotomopilus , Trichoderma , Knufia , Phialophora , Oxyporus , and Monocillium , which all played important roles in litter decomposition, positively correlated with heavy metals, sucrase, and catalase. Finally, results from this study will help us better clarify litter decomposition mechanisms in degraded ecosystems as well as provide a scientific basis for improving species cycling and nutrient transformation efficiency in mining ecosystems. [ABSTRACT FROM AUTHOR]

Microorganisms drive litter decomposition while maintaining the chemical cycle of ecosystems. We used the dominant vegetation (Imperata cylindrica) in the mining area selected for this study for this experiment to explore fungal community characteristics, key fungal groups, and their associative driving factors during I. cylindrica litter decomposition. Maximum litter C/N values occurred 100days after the commencement of the decomposition experiment during all different recovery years in this copper tailings area. Heavy metals in litter [copper (Cu), zinc (Zn), plumbum (Pb), and cadmium (Cd)] accumulated gradually with decomposition. The dominant fungal phyla observed in the community were Ascomycota and Basidiomycota, while the classes Sordariomycetes and Eurotiomycetes significantly increased as litter decomposition progressed. Degrees of connectivity and interaction between fungal communities were highest during the early litter decomposition stage. Sordariomycetes, Dothideomycetes, and Leotiomycetes all played critical roles in maintaining fungal community relationships. The effect of physicochemical properties and enzyme activities in I. cylindrica litter was significant on the dominant fungi, while driving factors that affected fungal communities differed over different recovery stages. Total nitrogen (TN), heavy metals, pH, and enzyme activities in the little were significantly correlated with fungal community composition. Litter properties throughout the litter decomposition process mainly affected the dynamics of the fungal community structure. The main environmental factors that affected fungal community structure were copper content and pH. Dichotomopilus, Trichoderma, Knufia, Phialophora, Oxyporus, and Monocillium, which all played important roles in litter decomposition, positively correlated with heavy metals, sucrase, and catalase. Finally, results from this study will help us better clarify litter decomposition mechanisms in degraded ecosystems as well as provide a scientific basis for improving species cycling and nutrient transformation efficiency in mining ecosystems.

Soil plays an essential role in providing ecosystem services, especially in mountain ecosystems which are often considered as fragile and sensitive systems and commonly consist of a mosaic of forest and rangeland plant communities. The relationship between above-ground plant cover and the properties of soil organic and mineral layers in mountain areas are rarely studied. This research aimed to assess the effect of different land covers (i.e. forest, forest-rangeland ecotone, and rangeland) on soil functional indicators, i.e. fertility and biological activities, in the Hyrcanian region of northern Iran. We hypothesized that (i) the presence of tree cover enhances soil fertility and biological activities and creates hot spots (islands) of soil functional indicators especially in the topsoil, (ii) litter quality and organic matter fractions are the drivers for activities of soil organisms, nutrient cycles and transformation processes in mountain ecosystems. Litter (O-horizon including L, F and H layers) and mineral soil samples (in two separate depths of 0–10 cm and 10–20 cm) were taken using iron frames (30 × 30 cm). In total, 45 litter and 90 soil samples were transferred to the laboratory. Soil characteristic especially in the 0–10 cm depth, litter carbon (C), nitrogen (N) and C/N ratio were significantly affected by different land covers showing the maximum of soil organic C and microbial activity under forest. Our findings showed that the studied land covers, as well as litter and soil properties can be separated by PCA output. The first and second axes, accounted more than 50% of the explained variance in each of the studied soil depths. Soils with a better quality of litter (i.e. lower C/N ratio), higher values for organic matter fractions, soil fertility indicators and soil biological activities can be attributed to the forest. In contrast, positions of low soil fertility indicator values and biota abundance were imposed by forest-rangeland ecotone and rangeland. Although each land cover plays a prominent ecological role and takes its place in the evolutionary process, forests are essential because of their capacity to store and transform carbon and nutrients and to create hotspots identified by functional soil indicators. Based on our findings, soil functions decreased ranked in the order forest > forest-rangeland ecotone > rangeland, which can be assigned to the lower density of trees, and the amount of litter mass and litter quality. It can be concluded that tree covers have a prominent role in increasing soil functions, which should be given special consideration in the restoration of degraded mountain ecosystems.

Fallen plant material such as leaves, needles and branches form litter beds which strongly influence fire ignition and spread. Traits of the dominant species influence litter flammability directly by determining how individual leaves burn and indirectly through the structure of the litter bed. However, we are yet to determine the relative importance of these different drivers across a range of plant species from different biomes.We undertook a meta‐analysis, combining leaf trait, litter structure and flammability data for 106 species from North America, South America, Europe, Asia and Australia. The dataset encompassed broad‐leaved and coniferous species from seven different experimental studies. Relationships between leaf traits, litter structure and key flammability metrics—sustainability, combustibility and consumability—were analysed using bivariate and piecewise structural equation modelling (SEM).Traits which characterise the three‐dimensional nature of the leaf and how much space a leaf occupies showed much stronger associations to litter structure and flammability than other morphological traits. Leaf curl, surface area to volume ratio (SAV) and SLA predominately influence litter flammability indirectly via litter structure with SLA being the only leaf trait which had a negative direct effect on flame duration. Packing ratio and bulk density were influenced by different combinations of leaf traits and, in turn, they aligned with different flammability metrics. Bulk density predicted flame spread rate and flame duration whereas packing ratio predicted consumption.Synthesis. We identified key leaf and litter traits which influence different components of litter bed flammability. Importantly, we show that the effects of these leaf and litter traits are consistent across a wide range of taxa and biomes. Our study represents a significant step towards developing trait‐based models for predicting surface wildfire behaviour. Such models will more flexibly accommodate future shifts in the composition of plant species triggered by altered fire regimes and climate change. [ABSTRACT FROM AUTHOR]

Aims: Plant invasions generally lead to mixtures between native and non-native litter. We assess the interactions between leaf litters from two invasive non-native trees (Robinia pseudoacia or Ailanthus altissima) and the native Populus alba on litter decomposition, nutrient release and soil properties along two gradients of invasion. Methods: Microcosms with field-collected soil covered by varying proportions of native and non-native litter simulated the two invasion gradients. We assessed the proportion of remaining litter mass and nutrient mass (N, P, C), and soil C, N-NO3−, total N, and pH, five times throughout a period of 11 months. Observed values were compared to the expected values on the assumption of no interactions. Results: Litter mass and C mass decayed slower in Robinia and faster in Ailanthus than in Populus. The three species immobilized N and P. Soil properties did not differ across pure litters. Both litter mixture gradients showed additive or antagonistic interactions on litter decomposition, whereas N and P mass were equal or higher than expected. The proportion of non-native litter in the mixture had non-linear effects on most variables, suggesting that the impact of these non-native trees on litter decay levels off or even declines as they become more abundant. Conclusion: The impacts of Ailanthus and Robinia litter on soil processes should not be derived from single species experiments, both due to non-additive effects and to non-linear responses to litter abundance. [ABSTRACT FROM AUTHOR]

Understanding plant litter decomposition in broad-leaved forests is important because it influences the geochemical cycles of nutrients and represents a vital link in the global carbon cycle. Bacteria play an important role in litter decomposition, especially late in the decomposition process, when they become abundant. In this paper, we investigate bacterial community composition and diversity during about 1 year of Quercus wutaishanica litter decomposition using a molecular approach, to fill the gaps in knowledge about bacterial communities during decomposition. The results showed that the phyla Proteobacteria (Alpha and Betaproteobacteria), Actinobacteria, Bacteroidetes, and Acidobacteria were the most dominant throughout the experiment. As decomposition progressed, a dynamic succession of community and diversity was observed for different decomposition periods. Decay stages and seasonal shifts occurred by successful replacement of copiotrophic bacterial groups such as Betaproteobacteria in the early stage. During the entire process of decomposition, litter decomposition selectively stimulated the relative abundance of Alphaproteobacteria (Sphingomonas, Rhizobium, and Methylobacterium) and Bacteroidetes, but reduced the abundance of Massilia (Betaproteobacteria), Acidobacteria, and Actinobacteria. Among the abiotic factors, litter N and P content was the main factor driving the succession of litter bacteria. These results indicate the changes in decomposition stages in terms of the bacterial groups and elucidate the microbial community underpinnings of nutrient cycling in forest ecosystems. [ABSTRACT FROM AUTHOR]

There are contrasting reports about whether and how vegetation types influence litter and soil properties. Accurate and comprehensive assessment of the complex relationship between vegetation types, litter and soil characteristics in semi-arid mountain landscapes is almost unknown. Thus, the purpose of this research was to study the effects of (1) Carpinus orientalis Miller., (2) Crataegus melanocarpa M.B. , (3) Rhamnus pallasii Fisch. and C.A.Mey, (4) Agropyron longiaristatum Boiss, (5) Bromus tomentolus Bioss. and (6) Hordeum vulgare L. on litter properties and soil physical, chemical, biochemical and biological features in northern Iran. A sampling of the organic layer (litter) and mineral soil (30 × 30 cm) from a depth of 0–10 cm was done for all characteristics in the summer season and for soil microclimate and biological characteristics in the summer and fall seasons. A total of 90 litter samples, 90 soil samples in summer and 90 soil samples in fall (6 vegetation types × 2 seasons × 15 samples) were taken from the area and transferred to the laboratory. Results showed that the Carpinus improved litter properties, soil organic matter contents, total N and available nutrients (P, K, Ca and Mg) and enzyme activities (urease, acid phosphatase, arylsulfatase and invertase). In addition, the population of earthworm groups (epigeic, anecic, and endogeic), acarina, collembola, nematodes, protozoa (especially in the fall season) and bacteria and fungi (especially in the summer season) under Carpinus significantly increased. Data analysis demonstrated higher soil fertility and biological activities in the woody vegetation, which can be assigned to the higher litter input and nutrients. Overall, the findings of this study showed that woody vegetation, especially Carpinus , can improve soil properties at high altitudes of mountainous, semi-arid sites that are often considered as especially fragile and sensitive ecosystems. [Display omitted] • Vegetation types strongly affected litter chemistry in a mountainous semi-arid environment. • Soil fertility increased under woody vegetation types, especially Carpinus orientalis. • Litter properties and soil fertility are the main drivers of soil biota activities. • Planting of Carpinus orientalis in a semi-arid landscape can strengthen litter and soil properties. [ABSTRACT FROM AUTHOR]

Studying the influence of topography and litter and soil nutrients on soil enzymes and microbial biomass is important to the understanding of soil nutrient transformation and cycling, but these relationships in heterogeneous soils of karst ecosystem remains poorly understood. We determined environment factors influencing the urease (URS) and alkaline phosphatase (ALP) activity and microbial biomass C and N (MBC and MBN) with advancing vegetation succession. The results showed that ALP increased but URS decreased with the advancing vegetation succession. The MBC and MBN were highest in shrubland, but both were lowest in grassland. The URS was positively correlated with the surface cover of rock outcrops (SRO) but negatively correlated with litter N, and soil available N and pH. Conversely, ALP was positively correlated with litter N, soil organic carbon (SOC), and soil available N and pH, but negatively correlated with soil total N. The MBC was positively related to litter quantities and SOC but negatively related to soil pH; the MBN was positively related to slope gradient (SLG), SOC, and soil total P and available P. Additionally, the trends of the index URS/MBN were grassland > secondary forest > shrubland > primary forest, but the index ALP/MBN increased with advancing vegetation succession. It indicated that soil microorganism mainly exudate extracellular URS and ALP to soils. We also found the interactions of topography (SLG and SRO), litter (nutrients and quantity), and soil (nutrients and pH) explained 42.00, 87.00, and 66.00% of the variations in URS, ALP, and microbial biomass, respectively. Path analysis showed that the topography had a directly positive effect on litter nutrients and quantities, but not on soil nutrients; the litter nutrients and quantities had direct positive effect on soil nutrients, which had direct effect on soil enzymes and microbial biomass; the relationships (R2) between the independent variable and enzymes activities and microbial biomass increased with advancing successions. Thus, it suggested that high SLG and SRO are good for collecting litters back to soils and then the topography, litter, and soil factors increased its controlling effect on soil enzymes activities and microbial biomass with advancing successions in karst ecosystem. [ABSTRACT FROM AUTHOR]

Deforestation in the Amazonian rainforest is the main cause of biodiversity loss, soil erosion, and climate change. Land covers influence the soil properties, soil biota community composition, and litter properties by providing habitat and nutrients. Our aim here was to present a quantitative analysis of the soil biochemical properties, soil biota assemblage, and litter properties associated with four land covers (primary Amazon rainforest, pasture, Hevea brasiliensis , and deforested sites) from the Brazil's Legal Amazon, Rio Branco, Acre. The non-metric multidimensional scaling (NMDS) grouped the land covers in four groups considering the dissimilarities on soil biota abundance between each other. The SEM models showed that deforestation increased the soil pH, and decreased SOC, TN, P, microbial N biomass, microbial C biomass, litter lignin content, litter N, C and P contents, and biodiversity indices (Margalef index, and α diversity). The results of our study highlighted the importance of considering land covers in Brazil's Legal Amazon, based on a sustainable way to improve soil quality and soil biodiversity, since even the studied monocropping system (pasture) showed decreases in habitat provision (litter deposition) and nutrient availability. Thus, the use of forest systems (H. brasiliensis) or the preservation of primary Amazon rainforest may positively influence the soil chemical properties, soil biota, and litter properties. • Deforestation increased soil pH, but decreased SOC, N, P, microbial biomass, and respiration. • Deforestation reduced the diversity indices, and uniformity index. • Litter deposition and quality were strongly related to soil biota abundance and diversity. • Pasture increased N and microbial respiration, while decreased all biodiversity indices. • Hevea brasiliensis increased Simpson's diversity index and litter C content. [ABSTRACT FROM AUTHOR]

• Soil mite diversity is positively related to resource diversity across trophic levels. • Predatory mite diversity is associated with nematode and fungal diversity. • Fungivorous mite diversity is positively associated with fungal diversity. • Detritivorous mite diversity is positively associated with litter quality. It is hypothesized that soil animal diversity is supported by environmental and food diversity. Mites are the most abundant microarthropods in soil communities that occupy several trophic levels in soil food webs and play important role in litter decomposition and nutrient cycling. However, it is not clear if diversity of mite communities is associated with diversity and quality in corresponding food resources across trophic levels. Here, we studied the influences of resource diversity (plants, fungi, and nematodes) and abiotic factors (litter and soil attributes) on taxonomic richness of detritivorous, fungivorous, and predatory mites (75 mite genera in total) in a subalpine succession (grassland, shrubland, secondary forest, primary forest) in southwestern China. Supporting our main hypothesis, diversity of the bulk mite community and individual functional groups was associated with the diversity and quality of resources across trophic levels. The total taxonomic richness was highest in the shrubland successional stage, where plant diversity was the highest, and decreased in late-successional stages despite a similar abundance. Diversity of predatory and fungivorous mites was positively associated with the diversity of nematode and fungal communities and reached maximum at the shrubland and grassland stages, respectively. Diversity of detritivorous mites was similar across different successional stages, being associated with litter quality. These findings provide empirical evidence that supports general ecological theory on the mechanisms that support multitrophic biodiversity in soils. [ABSTRACT FROM AUTHOR]

[Display omitted] • Under forest sites, fractions of soil organic matter, carbon and nutrient storage and transformation processes increased. • Soil microbial respiration and enzyme activities decreased under rangeland covers. • Except for endogeic and anecic earthworms, other soil biota increased their activities in surface soil layers at all sites. • Areas in mountainous regions under forest cover created hot spots (islands) of increased soil functional indicators. Soil plays an essential role in providing ecosystem services, especially in mountain ecosystems which are often considered as fragile and sensitive systems and commonly consist of a mosaic of forest and rangeland plant communities. The relationship between above-ground plant cover and the properties of soil organic and mineral layers in mountain areas are rarely studied. This research aimed to assess the effect of different land covers (i.e. forest, forest-rangeland ecotone, and rangeland) on soil functional indicators, i.e. fertility and biological activities, in the Hyrcanian region of northern Iran. We hypothesized that (i) the presence of tree cover enhances soil fertility and biological activities and creates hot spots (islands) of soil functional indicators especially in the topsoil, (ii) litter quality and organic matter fractions are the drivers for activities of soil organisms, nutrient cycles and transformation processes in mountain ecosystems. Litter (O-horizon including L, F and H layers) and mineral soil samples (in two separate depths of 0–10 cm and 10–20 cm) were taken using iron frames (30 × 30 cm). In total, 45 litter and 90 soil samples were transferred to the laboratory. Soil characteristic especially in the 0–10 cm depth, litter carbon (C), nitrogen (N) and C/N ratio were significantly affected by different land covers showing the maximum of soil organic C and microbial activity under forest. Our findings showed that the studied land covers, as well as litter and soil properties can be separated by PCA output. The first and second axes, accounted more than 50% of the explained variance in each of the studied soil depths. Soils with a better quality of litter (i.e. lower C/N ratio), higher values for organic matter fractions, soil fertility indicators and soil biological activities can be attributed to the forest. In contrast, positions of low soil fertility indicator values and biota abundance were imposed by forest-rangeland ecotone and rangeland. Although each land cover plays a prominent ecological role and takes its place in the evolutionary process, forests are essential because of their capacity to store and transform carbon and nutrients and to create hotspots identified by functional soil indicators. Based on our findings, soil functions decreased ranked in the order forest > forest-rangeland ecotone > rangeland, which can be assigned to the lower density of trees, and the amount of litter mass and litter quality. It can be concluded that tree covers have a prominent role in increasing soil functions, which should be given special consideration in the restoration of degraded mountain ecosystems. [ABSTRACT FROM AUTHOR]