Estimating Anthropogenic Influence in Tropical Forests Using Charcoal Introduction Jessica Del Greco Advisors: Crystal H. McMichael, Earth System Research Center, University of New Hampshire Michael Palace, Earth System Research Center, University of New Hampshire Methods Amazonian forests comprise a total area of 4.8 million km 2, and our study focused on the region of Santarem in eastern Amazonia (Figure 1). Fire is not natural in the Amazonian landscape, and most fire ignitions are a result of human activity (1). Fires leave fragments of charcoal in the soils below, and are commonly used to reconstruct ancient human activity in Amazonia (2). But, how might modern land-use influence these paleoecological and archaeological reconstructions? I examined the charcoal distribution from different forest types in the Santarem region based on modern human activity in those areas to determine how modern land use may affect paleoecological reconstructions. H1: Charcoal will be more frequent in logged + burned and burned forests than in the logged and undisturbed forests. H2: Soil charcoal abundance will decrease as depth increases. If charcoal is found in undisturbed forest samples it will be mostly in 20-30cm. +N+P +Ca+TOC Hypotheses Results Figure 1:Satellite imagery shows the location of the samples in Santarem. Summary and Conclusions Figure 3: Charcoal area for each land use category at each depth increment. Results from Kruskal-Walis tests indicate that charcoal area is significantly different between land use categories (Table 1). Charcoal was more frequent in burned and logged + burned forests at all depths analyzed. These results suggest that paleoecological and archaeological reconstructions are not feasible in areas that have recently been burned or logged + burned. Undisturbed forests or those that have been selectively logged are more useful for these types of surveys. Charcoal abundance did not decrease with increasing depth. Although there is a general trend of decreasing charcoal with increasing depth, these results were not significant. Increased sample size may lead to a different conclusion. Santarem is the oldest site of human occupation in Amazonia, where research has found pottery dating from 10, years ago. Undisturbed forest samples that contained abundant charcoal mostly in cm interval may indicate ancient disturbances. Forest type and land use classifications were made by a combination of 30 years of remote sensing imagery (Landsat) and field surveys. Sampling locations within undisturbed, logged, burned, and logged + burned forests (n = 8 per category, N = 32) were randomly chosen. Soils were collected with a hand auger in increments of 10 cm to a total depth of 30 cm. Charcoal was extracted from 50 grams of soil per sample using standard floatation and sieving techniques for fragments >500 um, and analyzed using a LW scientific stereoscope. The surface area of the charcoal within each sample was measured using a Moticam camera. The surface areas from each category were compared with a Kruskal Walis test (Figure 3, Table 1). Changes in the amount of charcoal was also compared between adjacent depth intervals using repeated measures (paired) t-tests (Table 2). Figure 2: Relative amounts of charcoal shown for each depth interval analyzed. Table 2: Paired t-test results that compare charcoal amounts for adjacent depth intervals. Results for each land use category are shown. References/Acknowledgements (1)Malhi, Y. et al. Exploring the likelihood and mechanism of a climate-change-induced dieback of the Amazon rainforest. Proceedings of the National Academy of Sciences 106, (2009). (2)McMichael, C. et al. Sparse pre-Columbian human habitation in western Amazonia. Science 336, (2012). Soil sampling was designed and conducted by Luiz Aragao (Exeter/INPE), Jos Barlow (Lancaster), Erika Berenguer (Lancaster), Joice Ferreira (Embrapa), and Toby Gardner (Cambridge). Any publications resulting from this work will be in full collaboration with these contributors. Table 1: Kruskal-Walis results for comparisons between land-use types. * indicates significant differences