Impact of Lower Atmospheric Carbon Dioxide on Tropical Mountain Ecosystems

Abstract

Carbon-isotope values of bulk organic matter from high-altitude lakes on Mount Kenya and Mount Elgon, East Africa, were 10 to 14 per mil higher during glacial times than they are today. Compound-specific isotope analyses of leaf waxes and algal biomarkers show that organisms possessing CO2-concentrating mechanisms, including C4 grasses and freshwater algae, were primarily responsible for this large increase. Carbon limitation due to lower ambient CO2 partial pressures had a significant impact on the distribution of forest on the tropical mountains, in addition to climate. Hence, tree line elevation should not be used to infer palaeotemperatures.

Major environmental changes recorded by lacustrine sedimentary organic matter since the last glacial maximum near the equator (Lagoa do Caçó, NE Brazil)

“…New analytical approaches applied on new records are needed in order to enhance our understanding of the nature, the extent and the origin of past paleoclimatic fluctuations. OM analyses have now proven their utility for paleoenvironmental reconstructions, in particular in lacustrine sedimentary records in temperate areas (Lallier-Vergès et al, 1993;Meyers and Lallier-Vergès, 1999;Manalt et al, 2001;Sifeddine et al, 1996), but rarely in tropical settings (Talbot and Livingstone, 1989;Street-Perrott et al, 1997;Sifeddine et al, 1998;2001;Ficken et al, 1998;Huang et al, 1999). Sedimentary lacustrine series are attractive targets to document paleoenvironmental changes because they generally offer high temporal resolution due to high sedimentation rates.…”

Spatial and temporal variations of C3/C4 relative abundance in global terrestrial ecosystem since the Last Glacial and its possible driving mechanisms

“…Lacustrine   13 C results from Sacred Lake (Figure 1) in Kenya, East Africa indicate that dominance of C 4 plants in this area during the Last Glacial was replaced by C 3 plants during the Holocene. Change of atmospheric CO 2 concentration was considered to be the main driving force responsible for this ecological shift [9]. Simulation results also suggested that change of CO 2 concentration alone could explain this observed vegetation shift in tropical Africa [10].…”

“…and low-altitude lakes in mountains (Figure 1), (including Lake Sacred [9,20,21], Lake Nkunga [22,23] and Lake Rutundu [24] in Mt. Kenya, Lake Kimilili in Mt.…”

Developing a methodology for carbon isotope analysis of lacustrine diatoms

“…The presence of organic matter observed through optical microscopy prior to treatment in nitric acid also highlighted the need for powerful oxidising agents [23] . 8 Further prolonged treatments in H 2 O 2 resulted in a fluctuation of %C and  13 C around a plateau. The gas chromatograms show slight increases in short-chain carbon compounds during this stage, which is contrary to what would be expected from the oxidation process.…”