Fine wood decomposition rates decline with the age of tropical successional forests in Southern mexico: implications to ecosystem carbon storage

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Wood decomposition in tropical forests is strongly linked to the terrestrial carbon cycle. Our understanding of the successional changes in wood decomposition in diverse tropical forests is still lim ited. In this study, we tested the hypothesis that fine wood decomposition rates decline with the increas ing age of successional forests due to the interspecific variation in wood density and changes in species composition. We studied fine wood decomposition in a chronosequence of tropical forests representing four successional phases in southern Mexico. Wood segments (1–7.5 cm diameter) from 30 dominant species (wood density range 0.34–0.83 g cm-³ ) were left on the ground for decomposition, and samples were recollected at different time intervals for three years. We used a modified negative expo nential model by introducing the power parameter (p) that allowed for a time-dependent decomposi tion rate (k). Average k within a successional phase ranged from 0.22 to 0.39 yr-¹ and declined gradu ally with the increase in forest age. We found a sig nificant negative correlation between wood density and decomposition rate constants. The kspecies ranged from 0.07 to 1.11 yr-¹ , whereas p-parameters varied between 0.65 and 1.42. Trees such as Bursera simar uba, and Cascabela gaumeri decomposed faster, while Eugenia ibarrae, and Pouteria reticulata decomposed slower. Average fine woody debris inputs ranged from 1.2 to 3.7 Mg ha-¹ yr-¹ which increased with forest age. Increasing production and declining decomposition rates during succession contribute to the higher accumulation of deadwood in primary forests. The results on generalized, age- and species-specific wood decay parameters have important implications in simulating carbon dynamics of the changing tropical forests. eng