Print PageBackground/Question/Methods
Regional carbon budget estimates for the Amazon Basin often exclude the contribution of floodplain forests. Despite comprising only approximately 4% of land area of the Basin, floodplain forests can sequester carbon at 2-3 times the rate of upland tropical forests. Such high rates of production could offset local carbon losses, but few data are available to incorporate seasonally flooded forests into carbon budget models. We used a network of 49 0.1 ha plots floodplain forests of the Eastern Amazon to measure aboveground forest biomass and biomass accumulation rates over a nine-year period. Forests of 15-80 y old were located across a flood gradient of 0-2 m aboveground and varied in terms of recent activity of introduced livestock. As land-use history can play an important role for forest productivity, we compared aboveground biomass and biomass accumulation rates across forest age, flood level, and livestock activity. We used allometric equations based on tree DBH (≥ 10 cm), height, and wood density to estimate aboveground woody biomass and carbon sequestration rates over a nine-year period.
Results/Conclusions
We provide the first known estimates for aboveground biomass and biomass accumulation rates in Amazonian floodplain forests of the Dry Corridor region. We estimated average aboveground woody biomass of 15-80 year-old forests as ~210 Mg ha-1. Despite a long history of land-use, forest biomass is similar to that of less disturbed floodplain forests in the Central Amazon. Biomass was highest in mid-successional forests with moderate flooding (water column of 0.60-1.3 m aboveground). In a subset of forests monitored over nine years, average aboveground biomass accumulation was ~5 Mg ha-1 y-1. Our results confirm the importance of early successional forests for carbon sequestration. Biomass accumulation rates were not correlated with flood level, refuting the hypothesis that productivity should increase with decreasing flood duration. Livestock activity and species composition may play a role in producing high mortality, slow tree growth, and low recruitment that resulted in carbon losses in some stands. C sequestration by secondary floodplain forests may play a small but important role in offsetting local carbon losses by deforestation and CO2 out-gassing in wetlands. These data may also improve regional models for C budgets by providing missing data for floodplain forests in the Dry Corridor of the Amazon Basin.
