Regulation of initial soil environmental factors on litter decomposition rate affects the estimation accuracy of litter mass loss in a subtropical forest

Aims Litter decomposition is a fundamental process in the carbon cycle in subtropical forests. Accurate evaluation of leaf litter decomposition rate is critical for understanding global carbon budgets. The effect of initial soil environmental factors (i.e., temperature and water content) on litter decomposition rates warrant detailed study. Methods Six groups of decomposition experiments starting in different months (January, March, May, July, September, and November) were conducted to simulate different initial soil environmental factors in a subtropical forest in southwest China. The annual litter mass loss was then calculated using the decomposition rate obtained from initial month treatments and local litterfall input data. Results Annual litter decomposition rates showed significant differences among treatments starting in the dry and rainy seasons, characterized by low and high initial soil temperatures and water contents. The average soil temperature and water content in the first 10-15 days significantly affected the annual litter decomposition rate. Compared with the accumulation algorithm, the calculated annual litter mass loss based on the decomposition rate obtained from the experimental group starting in May (at the transition of the dry and rainy seasons) was almost the same. However, it was overestimated by 18.2% in the experimental groups starting in the rainy season (July, September) and underestimated by 15.0% in the dry season (January, March). Conclusions Our findings suggested that a random arrangement of litter decomposition experiments may lead to inaccurate estimates of litter mass loss in areas with obvious seasonal changes.