Altitude, vegetation, paleoclimate, and radiocarbon age of the basal layer of peatlands of the Serra do Espinhaço Meridional, Brazil

Abstract

Peatlands are important chronological archives of paleoenvironmental changes, since they preserve materials which enable reconstruction of paleoenvironments from the Late Pleistocene. The Serra do Espinhaço Meridional (SdEM), located in the state of Minas Gerais, Brazil, can be considered one of the main areas of tropical mountain peatlands on Earth. When climate conditions are favorable, peatland formation occurs through the combination of lithology with relief and vegetation, whereby depressions favor the accumulation of water and nutrient poverty of quartzite lithologies induces the growth of vegetation rich in C metabolites and lignin. Anaerobiosis, together with organic matter resilience, low pH, and high Al3+ content, favor the successive accumulation of organic matter in time and space. The aim of this study is to correlate the age of basal organic matter of the SdEM peatlands with their altitudes and to identify the environmental factors that acted upon peatland formation. Eleven peatlands, situated between 1244 and 2014 m a.s.l., were identified using satellite imagery and cores were sampled in the field. Eighteen cores were collected from under grasslands and forest clusters in aluminum tubes of 8 cm in diameter. The basal layers, between 15 and 397 cm deep, had carbon content, average decomposition stage of organic matter, and radiocarbon age determined. Average carbon content increases and average decomposition stage of organic matter decreases with altitude. The peatlands situated below 1370 m a.s.l. would have begun to form in the Late Pleistocene, while those situated between 1580 and 1610 m a.s.l. would have begun to form in the Early and Middle Holocene, and those situated between 1760 and 2014 m a.s.l. would have begun their formation in the Late Holocene. In the southern hemisphere, the average temperatures would have been 9 °C lower than current average temperatures between 22 and 18 kyr BP. and, from 2 to 5 °C lower between 18 and 12 kyr BP. Between 12 and 8.8 kyr BP, the average temperatures varied from +2 to - 1 °C in relation to the current average temperatures. The favorable area for the establishment of vegetation cover in SdEM was smaller in the Last Glacial Maximum (LGM) than in the warmer periods of the Holocene. The radiocarbon age of the basement layer of SdEM peatlands decreases with increased altitude. The colder climate of the Late Pleistocene limited the formation of peatlands above 1570 m a.s.l. in SdEM.