The Importance of Litter Biomass in Estimating Soil Organic Carbon Pools in Natural Forests of Taiwan

Litter layers store a significant reservoir of carbon in forest ecosystems and are prone to be impacted by climate change and anthropogenic management practices. However, estimating forest litter biomass is commonly neglected in soil surveys. In this study, litter biomass, soil bulk density, fine soil content, and C concentration of the top 20 cm of topsoils were analyzed for 8 natural forests at elevations ranging 390~3000 m located within 4 climate zones (tropical, subtropical, temperate, and cool-temperate climate) to understand the importance of forest litter biomass in estimating soil organic carbon (SOC) pools in Taiwan. Natural temperate forests at high elevations stored 2~3 times the C per hectare than did warm tropical and subtropical ones. The proportion of the litter C pool in topsoils increased with elevation and was highest in the temperate forest (28.8%) and lowest in the tropical forest (4.0%). These results suggest that when estimating the potential of forest C sequestraion and release, temperate and cool-temperate forest litter layers should be of great concern since these C pools are considerably less well protected. The warmth index (WI) was significant positively correlated with litter C pools and SOC stocks (R=0.95), while there was no correlation between the annual precipitation and litter and SOC pools, indicating that litter accumulation and the SOC content in Taiwan are mainly controlled by temperature rather than precipitation.