Tropical forest biomass recovery is an important carbon sink, but the controls on its magnitude and spatial variation are poorly understood. The Brazilian Atlantic forest has been heavily deforested and affected by human activities for hundreds of years. Recent efforts, such as the establishment of the Serra do Conduru State Park in Bahia, Brazil, have created a patchwork landscape of small farms, different-aged forests, and remnant mature forests which are used for hunting, selective logging, and fiber harvesting. The degree to which these activities degrade intact forests or slow regeneration in unknown. Our objective was to understand the distribution of drivers of biomass recovery in this region by integrating forest inventory plots with high-density, discrete return airborne lidar. We mapped aboveground biomass (AGB) with lidar across 5000 ha of mature and secondary forest. We measured tree heights and diameters in 30 plots (0.25 ha each), estimated AGB with allometric equations, and developed a statistical model between lidar metrics of forest structure and plot-estimated biomass. We derived forest age from a time series of Landsat imagery and mapped topography, roads, trails, and human settlements using a combination of remote sensing and existing datasets.
We found rapid biomass recovery in areas regenerating from clearcutting or prior use as pasture. In areas with mature or 40-plus-year old secondary forest, we found lower biomass at lower elevations and nearer to trails, roads, and settlements. Mean secondary forest AGB was 99, 139, and 218 Mg ha-1 in forests with 1-10, 11-20, or 21-30 years of recovery respectively. Mature and older secondary forest had a mean AGB of 334 Mg ha-1. We found higher biomass in areas with steeper slopes, higher elevation, and in those areas with less evidence of human disturbance (e.g. further from trails and roads). These results show that biomass regeneration in the Southern Bahian Atlantic forest is rapid (~9 Mg ha-1 yr-1) relative to other neotropical sites. However, regeneration rates and biomass of intact forest are lower in areas with more evidence of human activity. Despite its protected status, human influence remains an important factor in this landscape and likely has important consequences for other ecosystem properties such as tree species composition and habitat quality.