Asynchronous terrestrial and marine signals of climate change during Heinrich events

Tropical regions have been reported to play a key role in climate dynamics. To date, however, there are uncertainties in the timing and the amplitude of the response of tropical ecosystems to millennial-scale climate change. We present evidence of an asynchrony between terrestrial and marine signals of climate change during Heinrich events preserved in marine sediment cores from the Brazilian continental margin. The inferred time lag of about 1000 to 2000 years is much larger than the ecological response to recent climate change and appears to be related to the nature of hydrological changes.     

Soil development along an altitudinal transect in a Bolivian tropical montane rainforest: Podzolization vs. hydromorphy

Knowledge about soil formation in tropical montane rainforests is scarce and patchy. We examined the altitudinal change of soils in a Bolivian tropical montane rainforest, aiming to illuminate the contribution of podzolization and hydromorphic processes to soil formation. In three transects from 1700 m to 3400 m a.s.l. we determined the pH, exchangeable cation exchange capacity, carbon and nitrogen stocks, and iron and aluminium fractions from 26 soil profiles. Three zones of different dominant soil forming processes were found: In the lower montane forest (LMF, 1700–2200 m a.s.l.), Dystropepts with high nutrient concentration and acidity were common. The pronounced change to the upper montane cloud forest (UMCF, 2200–2700 m a.s.l.) coincided with the appearance of Placorthods with more acidic conditions, deep ectorganic horizons and increasing translocation of sesquioxides. In the sub-alpine forest (SCF, 2700 m–3400 m a.s.l.), hydromorphic processes dominated over podzolization, resulting in Placaquods with low mineralization rate and nutrient concentration. This shows that due to increasing wetness and colder temperatures at high altitudes, dominant soil forming processes change from podzolization to hydromorphism soils with increasing altitude.