Fine root biomass stocks but not the production and turnover rates vary with the age of tropical successional forests in Southern Mexico

Fine root production, turnover, and decomposition are fundamental rhizosphere processes that can vary when young forest ecosystems pass through different phases of succession towards maturity. To assess these changes during succession, we applied ingrowth bag and sequential coring methods for fine root production and a modified negative exponential model for fine root decomposition at four phases of tropical forest chronosequence: 1) young secondary forests of about 8 years, 2) medium secondary forests of 15 years, 3) advanced secondary forests of 25 years, and 4) old-growth primary forests of >100 years. Primary forests stored higher fine root biomass than secondary forests but the average fine root productivity did not differ statistically between successional phases. Fine root turnover rates were >1 yr−1 for all the phases of succession, indicating that the turnover was higher than the standing fine root biomass. Fine root decay models showed that the decomposition rates did not differ significantly between successional phases. Furthermore, fine root production and mortality correlated positively to soil organic carbon concentrations. Our results showed that fine root productivity and turnover rates in secondary forests get to PF level from the younger phases of succession. The results have important implications in understanding the successional patterns regarding belowground resource allocation, nutrient turnover, and soil organic carbon sequestration in the constantly changing tropical forests ecosystems.