Search

Studies dealing with the reconstruction of Holocene climate change of tropical areas are scarce. Of these, multi-proxy investigations using peatlands are still absent. In this paper, we present the Holocene record of environmental changes in central–eastern Brazil reconstructed from a core sampled in Pau de Fruta mire (Serra do Espinhaço Meridional, Brazil). We combined palynological and geochemical analyses, supported by core stratigraphy, 14 C dating and multivariate statistics. The location of the mire is ideal because it is in an area which is directly associated with the South Atlantic Convergence Zone (SACZ). Six main phases of change suggested by vegetation and local and regional landscape dynamics were described. In phase I (~ 10,000–7360 cal. yr BP) the climate was very wet and cold and was accompanied by soil instability in the mire catchment (severe local erosion) and the 8.2 ka event was easily recognizable by a large increase in the deposition of regional dust. Phase II (~ 7360–4200 cal. yr BP) was characterized by wet and warm conditions, catchment soil stability and enhanced deposition of regional dust. In phase III (~ 4200–2200 cal. yr BP), climate was dry and warm and soil erosion in the catchment increased again. In phase IV (~ 2200–1160 cal. yr BP) dry and punctuated cooling was reconstructed, together with enhanced deposition of regional dust. Phase V (~ 1160–400 cal. yr BP) reflects sub-humid climatic conditions (like the current climate), the lowest inputs of local and regional dust and the largest accumulation of peat in the mire. While in phase VI (< ~ 400 cal. yr BP) sub-humid conditions continued but both local and regional erosion significantly increased. Our results demonstrate that the tropical peatlands of Serra do Espinhaço Meridional contain relevant records of Holocene climate changes, and that a multi-proxy approach offers good opportunities for a detailed reconstruction of palaeoenvironments. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution macroscopic charcoal and pollen analyses were used to reconstruct the fire and vegetation history of the Willamette Valley for the last 1200years. Presented in this paper are three new paleoecological reconstructions from Lake Oswego, Porter Lake, and Warner Lake, Oregon, and portions of previous reconstructions from Battle Ground Lake, Washington, and Beaver Lake, Oregon. The reconstructions show that prior to Euro-American settlement vegetation and fire regimes were influenced by a combination of natural and anthropogenic factors. Battle Ground Lake shows a stronger influence from climate, while Lake Oswego, Beaver Lake, Porter Lake, and Warner Lake were more controlled by human activity. However, human-set fires were also modulated by regional climate variability during the Medieval Climate Anomaly and the Little Ice Age. Fire reconstructions from Battle Ground Lake, Lake Oswego, Beaver Lake, and Porter Lake imply that fires were infrequent in the Willamette Valley 200–300years prior to Euro-American settlement. The decline of Native American populations due to introduced disease may have led to this reduction in fire activity. The prehistoric record from Warner Lake, however, indicates that fires in the foothills of the Cascade Range were more frequent than on the valley floor, at least until ca. AD 1800. The historic portions of the reconstructions indicate that Euro-American land clearance for agriculture and logging produced the most dramatic shifts in vegetation and fire regimes. All five records indicate that few fires in the Willamette Valley have occurred since ca. AD 1930, and fires today are predominantly grass fires. [ABSTRACT FROM AUTHOR]