A Holocene pollen record of savanna establishment in coastal Amapá

Abstract

The main goal of this study was to investigate how climate and human activities may have influenced ecotonal areas of disjoint savannas within Brazilian Amazonia. The fossil pollen and charcoal records of Lake Márcio (Amapá) were used to provide a Holocene palaeoecological history of this region. Detrended correspondence analysis (DCA) was used to enhance the patterns of sample distribution along the sediment core. A marked vegetation change from closed forests with swamp elements to open flooded savanna at c. 5000 yrs BP was evident from the pollen record. Charcoal analysis revealed a pattern of increased accumulation of particles coincident with the establishment of savannas, suggesting higher fire frequency and human impacts near the lake. A 550-year sedimentary hiatus suggests that the lake depended heavily on floodwaters from the Amazon River, and that it became suddenly isolated from it. When sedimentation restarted in the lake, the environment had changed. A combination of factors, such as reduced river flooding, palaeofires and human occupation may have had a tremendous impact on the environment. As there are no other major changes in vegetation, after 4700 yrs BP, it is plausible to assume that the modern mosaic vegetation formed at that time.

Unfolding long‐term Late Pleistocene–Holocene disturbances of forest communities in the southwestern Amazonian lowlands

“…13), that is, near the Younger Dryas (YD) between 12,900 and 11,700 cal yr BP (cf. The record of C 4 terrestrial plants has been used to suggest dry periods in other Amazonian areas, not only in the YD, but also in the Last Glacial Maximum (LGM) and Oldest Dryas (OD; e.g., Absy et al 1991, van der Hammen and Absy 1994, Mayle et al 2000, Colinvaux et al 2000. The imprint of this event in South America remains to be investigated in greater depth.…”

Late Quaternary landscape evolution of northeastern Amazonia from pollen and diatom records

“…A vegetation change coheval with the one recorded in the study area occurs in other Amazonian areas. Hence, a marked change from dense tropical forest and mangrove to open flooded savanna was detected in Lake Marcio, State of Amapa, at c. 5,000 cal yrs BP (Toledo and Bush 2008). According to these authors, this event was attributed to lake isolation due to river floods, combined with increased paleofires mainly due to human occupation.…”

“…In Brazil, there are many palynological studies suggesting undisturbed closed forest during cooler climate episodes of the late Quaternary (e.g., Colinvaux et al 1996, Haberle 1997, Bush et al 2004, Irion et al 2006, Mayle and Power 2008, Toledo and Bush 2008. In contrast, several other studies, especially carried out in the seasonal eastern Brazilian Amazonia, have related savanna expansion to cool/dry episodes during this time interval (Absy et al 1991, Van der Hammen et al 1992, Absy 1994, Pessenda et al 1998).…”

“…In addition, several palynological studies suggest undisturbed closed forest during late Quaternary cooler climate episodes (e.g., Colinvaux et al 35-55 36 DARCILéA F. CASTRO, PAULO E. DE OLIVEIRA, DILCE F. ROSSETTI and LUIZ C.R. PESSENDA 1996, Haberle 1997, Bush et al 2004, Irion et al 2006, Mayle and Power 2008, Toledo and Bush 2008. On the other hand, cold forest is recorded in the upper Peniglacial of Ecuador (Colinvaux and Liu 1987).…”

Testing multivariate analysis in paleoenvironmental reconstructions using pollen records from Lagoa Salgada, NE Rio de Janeiro State, Brazil

“…In the last decade, however, an increasingly large number of studies that have been conducted started to apply different techniques of Multivariate Analysis in Palynology, such as Detrended Correspondence Analysis -DCA, Principal Component Analysis -PCA, Two-way Indicator Species Analysis -TWINSPAN, Non-metric Multidimensional Scaling -NMDS, and even Canonical Correspondence Analysis -CCA (e.g. , Rodgers and Horn 1996, Behling et al 1997, Haberle and Bennett 2001, Stutz and Prieto 2003, Urrego et al 2005, De Toledo and Bush 2008a.…”