Effects of latitude and altitude on the composition of humus in forest soils in the Low Latitude Plateau

The forest soil humus carbon pool is a significant part of the global carbon cycle. However, there are currently few reports on the pattern of distribution of latitude and altitude and influencing factors on humus carbon in forest soils, although it is highly important to explore the decomposition, mechanism of transformation and storage of soil carbon in forests. We measured the contents of surface soil organic carbon (SOC), humic acid carbon (HAC), fulvic acid carbon (FAC) and humin carbon(HMC) in forest soils of low-latitude and high-altitude and clarified the characteristics and influencing factors of the changes in humus at different latitudes and altitudes. The results showed that the composition of SOC and HAC increased with the increase in latitude and altitude. The influence of altitude on the composition of humus carbon was significant at latitudes of 23°N ~ 25°N but not at other latitudes. The soil moisture content and the C/N were the primary factors that affected the soil SOC and HMC in high latitude and altitude areas. The soil HAC and FAC at low latitudes and altitudes are primarily affected by the mean annual temperature, pH and amount of silt. Therefore, when assessing forest soil carbon sequestration, the focus on should be on carbon sequestration in high-latitude and high-altitude areas. This study revealed the characteristics and influencing factors of soil humus carbon composition in low-latitude and high-altitude regions of China and provide a reference for the evaluation of soil carbon storage in complex terrain and climatic regions of the world.