RESUMO
Land-use conversion affects soil organic carbon (SOC) dynamics. Therefore, an in-depth study of change in SOC, SOC pool, fractions of SOC and enzymatic activities of soil microbial biomass carbon (SMBC) and dehydrogenase (DHA) with the conversion of forest land to jhum, fallow jhum and settle cultivation use has been undertaken on the hills of Arunachal Pradesh of India. Geo-referenced soil samples from eight different locations, each from different land uses were collected at three depth. One part of the soil sample had been used for the analysis of SOC and its carbon fraction. The second portion was kept in a deep freezer for determining SMBC and DHA. The third part was used for the analysis of bulk density. The result revealed that the highest loss of SOC pool was recorded in jhum land (41.8 to 13.4%), and the labile carbon was also found to decrease in jhum land. The highest SMBC was observed on the surface soil of the natural forest; the highest DHA was found in the natural forest; and the lowest DHA was recorded in jhum land. This study found that the converting natural forest to jhum reduces SOC storage, enzymatic activities and C fractions significantly whereas fallow jhum shows sign of recovery because all of these parameters improved when compared to the jhum land-use system. This study also confirms that the fallow period helps restore the initial situation.