Soil Carbon Sequestration Potential of Analog Forests in Comparison to Tea Plantation Areas of Up Country Intermediate Zone of Sri Lanka

Carbon sequestration can be used to reduce atmospheric carbon dioxide levels, thereby mitigating climate-change implications. Land-use changes determine the soil's ability to sequester and store carbon. This study aims to assess the soil organic carbon stock between the analog forest system and the cultivated tea area. Soil samples were collected from 0 to 10 cm, representing topsoil and 0 to 30 cm representing the subsoil. Analysis of the Variation (ANOVA) was used to compare the soil quality parameters of land-use types at two depths levels. Soil organic carbon stock (SOCS) was calculated for each sample location in the analog forest, and the SOCS was spatially predicted for ______________________________________ areas in the analog forest using the Arc GIS 10.7.1 software. The study results revealed that analog forest systems have higher below-ground carbon fixation potential than monoculture systems. According to the statistical analysis, the amount of SOCS was 13 % higher in analog forests (33.95 Mg/ha > 29.93 Mg/ha). The application of the general linear model confirmed that both land use and soil depths are the significant driving forces of SOCS (P < 0.05).


INTRODUCTION
The increasing greenhouse gas (GHG) concentration in the atmosphere is a critical issue for the natural functioning Three mechanisms were suggested to reduce GHG levels, including emission reduction, joint implementation, and clean development (Kenye et al., 2019).
Further, carbon reduction targets are initially assigned to developed countries. The practice of those mechanisms helps to reduce anthropogenic carbon dioxide (CO2) emissions and improve carbon sinks in the biosphere (Albrecht and Kandji, 2003 higher below-ground carbon storage than the monoculture land-use systems.
The main objectives of this study were (1)

Study Area
Analog forest located at Belipola, Mirahawatte, (longitude 80. 93397 0 E, latitude 6. 87515 0 N), Badulla district, intermediate zone of Sri Lanka ( Figure   1) was selected to represent man-made forest system and adjacent tea lands that share the same climatic, and geological conditions (Table 1)

Soil Analysis
The laboratory analysis was carried out at the Faculty of Agriculture and  (Dharmakeerthi et al., 2007). Soil organic carbon was quantified by using Walkley and Black method (Walkley and Black, 1934). Finally, bulk density was determined by the core sample method (Blake and Hartage, 1986).

Comparison of Soil Quality between the Analog Forest and the Tea Cultivation
The results were supported to accept the first research hypothesis that the mean SOCS varies significantly with the land use. The frequency distribution of SOCS shows analog forests hold higher organic carbon stock than cultivated tea areas ( Figure 2  We found that bulk density (BD) in tea land was significantly lower than that of analog forest (Table 2). Due to limited activities within the analog forest to improve the soil, soil compaction may be higher in the analog forest than in the cultivated tea area. In contrast, weeding and fertilization had done in the smallholder tea cultivation lands that we selected for data collection during this study. This could be the reason for the reported lower bulk density for cultivated tea areas.
The one-way ANOVA results show that soil pH is significantly lower in the cultivated tea areas (Table 2)

Quality Parameters between Top and Subsoil Layers
Our second research hypothesis (the mean SOCS varies significantly between top and subsoil) was accepted as SOCS varied considerably between 0-0.1 m and 0.1-0.3 m soil layers (Table   3).  Further, results suggested that bulk density and electrical conductivity significantly differed between top and subsoil in the analog forest system. In tea cultivation, bulk density and pH were significantly changed with the soil depth, not the electrical conductivity (Table 3)

CONCLUSION
This study has shown that analog forest systems have higher below-ground carbon fixation potential than monoculture systems (tea cultivation).
The amount of SOCS was 13 % higher in the analog forest than in the cultivated tea area. This study reveals that higher SOCS in the analog forest system is a function of high biomass levels, rich species composition, and ecological restoration abilities.

Belipola Arboretum and Research
Centre, Mirahawatta is acknowledged for proving their sites for conducting this research. The authors wish to thank Mr. Indika Karunarathna and the staff of Earth Restoration (Pvt) Ltd.,

Belipola Arboretum and Research
Centre for their support during the fieldwork.