INcas and alders

Article Abstract:

Pollen and stratigraphical record of a small lake in the Peruvian Andes, investigated by Chepstow-Lusty and colleagues, shows that charcoal was abundant about 4,000 years ago, suggesting vegetation management by burning. Grasslands may have been grazed by herds of camelids, encouraging the abundance of weeds such as Ambrosia. The decline in the abundance of pollen of Chenopodiaceae and Ambrosia is explained by the general fall in temperature. A sudden expansion of alder trees took place around AD 1050 and this may be explained by the reduction of human activity in the area, leading to natural vegetative recovery.

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Back to the little ice age

Article Abstract:

A study of twelve well preserved shoots of Cassiope tetragona, an arctic dwarf-shrub, found in Ellesmere island in Canada provides important clues about the ecological conditions prevailing between AD 1425 and 1665, known as the Little Ice Age. Results reveal that the July temperature of the region was about 0.7 degrees lower at the time when the shrubs became fossilized under the snow than the present temperature. Growth rings of the shrubs yield an estimation of the climate.

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Seeds of doubt

Article Abstract:

Researchers have studied three weed species to measure features such as biomass yield, survivorship and seed mass.

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