This study aimed to identify soil organic carbon stocks in croplands and pasture area of Altanbulag soum of Selenge province in the northern part of Mongolia. Based on historical soil data, which was collected in 1977. In order to reveal soil organic carbon changes between 1977 and 2019, we chose 10 sampling locations from these soil data and collected 32 soil samples from the 0-20 cm, and 20-40 cm depth of soil layers in 2019. Results showed that the organic carbon content of 0-20 cm depth of cropland soil layer decreased by 15.4 % in 2019 (21.85 t ha-1) compared to 1977 (25.8 t ha-1). Besides, soil organic carbon content for 0-20 cm depth of cropland soil layer was reduced by 51.8 %, which was reduced by 0.8 % for 20-40 cm depth of cropland soil layer compared to those results of soils of pasture land.

An important prerequisite to sustainable soil management is a good understanding of soil morphological, physical and chemical characteristics. Until now, very limited data are available on the characteristics of high mountain soils in the Mongolia. Thus, this study is conducted to determine the morpho-physical and chemical characteristics of high mountain soils in eastern Khangai. Mountain soils play a major role in the functioning and conservation of unique ecosystems and the hydrology of mountain belts. High mountain soils are soils with a beginning of soil formation, therefore the horizon differentiation is weak. However very high carbon stocks and sequestration rates can be found in this Khangai mountain area. High mountain soils are developed in medium and fine-textured materials derived from a wide range of rocks, mostly in colluvial deposits. Another specific characteristics is very cold temperatures which are defined as containing permafrost within one meters of the soil surface.

The accuracy of large-scale soil organic carbon estimation depends on data availability from a site based or small-scale measurements. In this study, we estimated soil organic carbon stock (SOCS) and its distribution difference of small catchment in the forest-steppe region. The grid sampling strategy was used to collect samples that covered 3 types of landscape in Ulziit catchment and distance between samples was measured by tape measures in the fieldwork. The average SOCS of Ulziit catchment was 60.8 t ha-1 in 0-30 cm and fluctuation of the distribution was high (CV 62.1%). Then, the result interpreted in mountain north slope, south slope, and valley bottom. SOCS was highest (115.5 t ha-1) in the bottom of the valley and SOCS at the north slope (53.3 t ha-1) and south slope (38.8 t ha-1) were significantly different (P<0.05).

Phosphorus is an essential nutrient in plants required for root establishment. There are many methods for the extraction of available forms; however the choice is dependent on several factors among them soil pH. Forty nine samples were collected from three different sites from Bayankhongor, Orkhon aimag and Ulaanbaatar city. The samples were air dried, sieved, under 2 mm sieve and stored in sample bags for subsequent analysis. Phosphorus extractions of were carried out using a basic extractants. The extracts of Machigin and Olsen were measured colorimetrically by the hydrazine method and ascorbic acid method at 630 nm and 880 nm wavelength respectively. The soils had a pH range of between 6.98-7.80; phosphorus, 3.70-71.4 mg P/ kg by Machigin and 2.22-21.37 mg P/kg by Olsen. The methods were linearly correlated (r=0.82).

This study aimed to identify soil organic carbon stocks in croplands and pasture area of Altanbulag soum of Selenge province in the northern part of Mongolia. Based on historical soil data, which was collected in 1977. In order to reveal soil organic carbon changes between 1977 and 2019, we chose 10 sampling locations from these soil data and collected 32 soil samples from the 0-20 cm, and 20-40 cm depth of soil layers in 2019. Results showed that the organic carbon content of 0-20 cm depth of cropland soil layer decreased by 15.4 % in 2019 (21.85 t ha-1) compared to 1977 (25.8 t ha-1). Besides, soil organic carbon content for 0-20 cm depth of cropland soil layer was reduced by 51.8 %, which was reduced by 0.8 % for 20-40 cm depth of cropland soil layer compared to those results of soils of pasture land.

This study aimed to identify soil organic carbon stocks in croplands and pasture area of Altanbulag soum of Selenge province in the northern part of Mongolia. Based on historical soil data, which was collected in 1977. In order to reveal soil organic carbon changes between 1977 and 2019, we chose 10 sampling locations from these soil data and collected 32 soil samples from the 0-20 cm, and 20-40 cm depth of soil layers in 2019. Results showed that the organic carbon content of 0-20 cm depth of cropland soil layer decreased by 15.4 % in 2019 (21.85 t ha-1) compared to 1977 (25.8 t ha-1). Besides, soil organic carbon content for 0-20 cm depth of cropland soil layer was reduced by 51.8 %, which was reduced by 0.8 % for 20-40 cm depth of cropland soil layer compared to those results of soils of pasture land.

An important prerequisite to sustainable soil management is a good understanding of soil morphological, physical and chemical characteristics. Until now, very limited data are available on the characteristics of high mountain soils in the Mongolia. Thus, this study is conducted to determine the morpho-physical and chemical characteristics of high mountain soils in eastern Khangai. Mountain soils play a major role in the functioning and conservation of unique ecosystems and the hydrology of mountain belts. High mountain soils are soils with a beginning of soil formation, therefore the horizon differentiation is weak. However very high carbon stocks and sequestration rates can be found in this Khangai mountain area. High mountain soils are developed in medium and fine-textured materials derived from a wide range of rocks, mostly in colluvial deposits. Another specific characteristics is very cold temperatures which are defined as containing permafrost within one meters of the soil surface.

An important prerequisite to sustainable soil management is a good understanding of soil morphological, physical and chemical characteristics. Until now, very limited data are available on the characteristics of high mountain soils in the Mongolia. Thus, this study is conducted to determine the morpho-physical and chemical characteristics of high mountain soils in eastern Khangai. Mountain soils play a major role in the functioning and conservation of unique ecosystems and the hydrology of mountain belts. High mountain soils are soils with a beginning of soil formation, therefore the horizon differentiation is weak. However very high carbon stocks and sequestration rates can be found in this Khangai mountain area. High mountain soils are developed in medium and fine-textured materials derived from a wide range of rocks, mostly in colluvial deposits. Another specific characteristics is very cold temperatures which are defined as containing permafrost within one meters of the soil surface.

The accuracy of large-scale soil organic carbon estimation depends on data availability from a site based or small-scale measurements. In this study, we estimated soil organic carbon stock (SOCS) and its distribution difference of small catchment in the forest-steppe region. The grid sampling strategy was used to collect samples that covered 3 types of landscape in Ulziit catchment and distance between samples was measured by tape measures in the fieldwork. The average SOCS of Ulziit catchment was 60.8 t ha-1 in 0-30 cm and fluctuation of the distribution was high (CV 62.1%). Then, the result interpreted in mountain north slope, south slope, and valley bottom. SOCS was highest (115.5 t ha-1) in the bottom of the valley and SOCS at the north slope (53.3 t ha-1) and south slope (38.8 t ha-1) were significantly different (P<0.05).

The accuracy of large-scale soil organic carbon estimation depends on data availability from a site based or small-scale measurements. In this study, we estimated soil organic carbon stock (SOCS) and its distribution difference of small catchment in the forest-steppe region. The grid sampling strategy was used to collect samples that covered 3 types of landscape in Ulziit catchment and distance between samples was measured by tape measures in the fieldwork. The average SOCS of Ulziit catchment was 60.8 t ha-1 in 0-30 cm and fluctuation of the distribution was high (CV 62.1%). Then, the result interpreted in mountain north slope, south slope, and valley bottom. SOCS was highest (115.5 t ha-1) in the bottom of the valley and SOCS at the north slope (53.3 t ha-1) and south slope (38.8 t ha-1) were significantly different (P<0.05).

Phosphorus is an essential nutrient in plants required for root establishment. There are many methods for the extraction of available forms; however the choice is dependent on several factors among them soil pH. Forty nine samples were collected from three different sites from Bayankhongor, Orkhon aimag and Ulaanbaatar city. The samples were air dried, sieved, under 2 mm sieve and stored in sample bags for subsequent analysis. Phosphorus extractions of were carried out using a basic extractants. The extracts of Machigin and Olsen were measured colorimetrically by the hydrazine method and ascorbic acid method at 630 nm and 880 nm wavelength respectively. The soils had a pH range of between 6.98-7.80; phosphorus, 3.70-71.4 mg P/ kg by Machigin and 2.22-21.37 mg P/kg by Olsen. The methods were linearly correlated (r=0.82).

Phosphorus is an essential nutrient in plants required for root establishment. There are many methods for the extraction of available forms; however the choice is dependent on several factors among them soil pH. Forty nine samples were collected from three different sites from Bayankhongor, Orkhon aimag and Ulaanbaatar city. The samples were air dried, sieved, under 2 mm sieve and stored in sample bags for subsequent analysis. Phosphorus extractions of were carried out using a basic extractants. The extracts of Machigin and Olsen were measured colorimetrically by the hydrazine method and ascorbic acid method at 630 nm and 880 nm wavelength respectively. The soils had a pH range of between 6.98-7.80; phosphorus, 3.70-71.4 mg P/ kg by Machigin and 2.22-21.37 mg P/kg by Olsen. The methods were linearly correlated (r=0.82).