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Background: Land use and land cover changes have a significant impact on the dynamics of soil organic matter (SOM) and its fractions, as well as on overall soil health. This study conducted in Bharatpur Catchment, Chitwan District, Nepal, aimed to assess and quantify variations in total soil organic matter (TSOMC), labile organic matter fraction (CL), stable organic matter fraction (CS), stability ratio (SR), and carbon management index (CMI) across seven land use types: pastureland, forestland, fruit orchards, small-scale conventional agricultural land, large-scale conventional agricultural land, large-scale alternative fallow and conventional agricultural land, and organic farming agricultural land. The study also explored the potential use of the Carbon Management Index (CMI) and stability ratio (SR) as indicators of soil degradation or improvement in response to land use changes. Results: The findings revealed significant differences in mean values of TSOMC, CL, and CS among the different land use types. Forestland and organic farming exhibited significantly higher TSOMC (3.24%, 3.12%) compared to fruit orchard lands (2.62%), small scale conventional farming (2.22%), alternative fallow and conventional farming (2.06%), large scale conventional farming (1.84%) and pastureland (1.20%). Organic farming and Forestland also had significantly higher CL (1.85%, 1.84%) and CS (1.27%, 1.39%) compared to all other land use types. Forest and organic farming lands showed higher CMI values, while pastures and forests exhibited higher SR values compared to the rest of the land use types. Conclusions: This study highlights the influence of various land use types on soil organic matter pools and demonstrates the potential of CMI and SR as indicators for assessing soil degradation or improvement in response to land use and land cover changes. [ABSTRACT FROM AUTHOR]

This paper gives an overview of soil ecosystem services, soil organic matter dynamics, models of soil organic matter, biotic and abiotic control of litter decomposition, patterns of soil biodiversity, and potential of soil carbon sequestration to mitigate climate change. Healthy soil provides a wide range of ecosystem goods and services and the value of the ecosystem services provided by soil biodiversity amounts to US $1.5 trillion per year. Soil texture, soil mineralogy and soil organic matter play an important role in the functioning of an ecosystem. The global carbon pools and fluxes, and soil and vegetation carbon pools at biome and regional level have been discussed. The organic matter inputs and soil carbon pools vary in different biomes and ecosystems. Soil organic carbon simulation models are being increasingly used to describe soil carbon dynamics. Climate, soil fauna and litter quality regulate the rates of litter decomposition at local, regional and global scale. Litter quality has emerged as the most important direct regulator of the rates and patterns of litter decomposition at the global scale. There is much interest to analyze the effect of litter diversity, climate change and invasive species on litter decomposition rates. Modern techniques of molecular biology and high resolution microscopy elucidate the structural and functional aspects of soil biodiversity. Sustainable management and conservation of soil biota is important for conserving global biodiversity, as soil communities are species rich and affect ecosystem processes. conservation agriculture, tree plantations on degraded lands, and agroforestry could enhance carbon storage in the soil-plant system. The integration of science, technology and traditional ecological knowledge can make substantial contribution to the science of soil ecology, ecosystem carbon management, and sustainability. [ABSTRACT FROM AUTHOR]