Abstract
Understanding distribution of soil organic carbon (SOC) in soil profile is important for assessing soil fertility and SOC stock because it varies with soils of different vegetation and land use types. In this context, the objective of this research is that it was conducted to determine key variance in the SOC stock in three different soil layers, 0–20 cm, 20–40 cm, and 40–60 cm of different vegetation covers of Shivapuri Nagarjun National Park of Kathmandu district, Nepal. Overall field measurement was based on standard national methods. We used the dichromate digestion method to analyse SOC concentrations. The highest SOC concentration (%) was recorded as 4.87% in 0–20 cm of oak forest and lowest 0.42% in 40–60 cm of Chir pine forest. Forest types (oak, upper mixed hardwood, lower mixed hardwood, and Chir pine) had SOC stock 149.62, 104.47, 62.5, and 50.85 t/ha, respectively, up to 60 cm depth. However, these values are significantly different (p=0.02) at 5% level of significance when comparing means between the forest types. The SOC stock was decreased with increased soil depth, though not significantly different at 5% level of significance. Further study with respect to different climate, soil, forest, and land use type is recommended.
Highlights
Soil is a complex mixture of mineral nutrients, organic matter, water, air, and living organisms determined by diverse environmental factors such as climate, parent material, relief, organisms, and time factor [1]
E Soil organic carbon (SOC) concentration was found higher in the upper layers which could be related to higher soil organic matter content and less influence of parent materials. e oak forest soil had the highest SOC concentration (4.8%), followed by upper mixed hardwood forest (3.7%), lower mixed hardwood forest (1.9%), and Chir pine forest (1.5%)
Pradhan et al [22] reported greater SOC concentration in the Schima-Castanopsis forest than in other forest types, but this study shows that the SOC concentration is found higher in the oak forest as the forest was dense and due to different microbial activities in the soil. e greater the depth, the lower the SOC concentration for all types of forest
Summary
Soil is a complex mixture of mineral nutrients, organic matter, water, air, and living organisms determined by diverse environmental factors such as climate, parent material, relief, organisms, and time factor [1]. In the first meter of soil, the SOC stock contains an estimated 1500 PgC which is more carbon than in the atmosphere (approximately 800 PgC) and terrestrial plants (500 PgC) combined [4]. E amount of SOC stock experiences significant spatial diversity, both horizontally by land use type and vertically within the soil profile. Depending on their turnover times, land cover affects carbon that exists between different soil pools. Soils are a potentially viable sink for atmospheric carbon [6]
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